Download Phasing of Gene Products during Development1

[CANCER RESEARCH 34, 2044-2052. August 1974]
Phasing of Gene Products during Development1
Cole Manes
B. F. Slolinksy Laboratories, Department of Pediatrics, University of Colorado Medical Center, Denver, Colorado 80220
Summary
Although ontogeny may ultimately be best described as a
continuous process and although gene repression may never
be absolute, there is, nonetheless, considerable experimental
and conceptual justification for designating more-or-less
discrete phases in ontogeny which can be defined in terms of
characteristically predominant sets of expressed genes. The
concept of developmental phases is compatible with evi
dence demonstrating temporal sequences of only partially
overlapping transcriptive sets, such as appear to occur dur
ing early embryogenesis, as well as with evidence demon
strating a progressive restriction in transcriptional activity
within a given set, as appears to occur during terminal
differentiation within a cell lineage. The phase-specific gene
products that have been identified or inferred in developing
systems include, in addition to detectable antigens, RNA
polymerases, transfer RNA species, transfer RNA methyltransferases and their inhibitors, aminoacyl transfer RNA
synthetases, ribosomal proteins, and "masking" proteins
associated with the cell membrane. Since the regulation of
gene expression in eukaryotes appears to involve integrated
gene sets rather than individual genes, we may predict that
these gene products are members of such sets whose other
members remain to be identified. We may further predict
that the reexpression of these gene products during the
malignant transformation of adult cells may not involve a
random derepression of individual genes, but rather an
orderly switch from one integrated gene set to another,
such as occurs in transdetermination.
Work in our laboratory has focused on genetic expression
during the early phases of mammalian embryogenesis. We
have found that, even in multipotential embryonic cells, the
transcription of nonrepetitive DNA sequences is actually
more restricted than that in several adult organs. During the
period of intense organogénesis,transcription of nonrepeti
tive DNA sequences is more widespread, as might be
expected, but it is also evident that genes expressed earlier
are repressed at this later stage. There are demonstrable
losses of discrete protein synthetic capacities even during
the first days of embryogenesis, and marked decreases in
transfer RNA methyltransferase activity.
Attention is called to the mammalian trophoblast cell, its
unique position in the lineages of cells derived from the
zygote, the gene sets apparently involved in the production
of this specialized cell phenotype, and the evidence that its
mitosis and/or phenotypic expression can be, and frequently
1Presented at the Third Conference on Embryonic and Fetal Antigens
in Cancer, November 4 to 7, 1973, Knoxville, Tenn.
2044
are, regulated by the uterine milieu during normal reproduc
tion. It is proposed that this natural phenomenon may
provide clues toward solving clinical problems involving the
multiplication and differentiation of the malignant cell.
It is no longer a question that cancer cells may display
gene products that are normally components of embryonic
or fetal cells, but that are absent or present in much smaller
amount in adult cells. This phenomenon has been well
reviewed elsewhere (I, 32) and has already found applica
tion in the diagnosis and clinical management of some
forms of cancer (42). The questions that remain entail the
relevance of this phenomenon to the fundamental nature of
the malignant process and the potential of the embryonic or
fetal properties of malignant cells for new therapeutic uses
in cancer. It is these 2 questions which prompt the following
discussion of stage- or phase-specific gene expression during
normal development, in the belief that current information
regarding the regulation of gene expression in eukaryotes
and the behavior of embryonic cells will indeed contribute to
the understanding and management of this major medical
problem.
The discontinuous use of at least portions of the genetic
endowment appears to be a widespread, if not universal,
trait in the living world. Phasing is seen in organisms with
the simplest genomes as well as in those with the most
complex. For example, viral replication involves the se
quential expression of "early" and "late" functions (11).
The bacterial cell undergoing sporulation synthesizes unique
proteins in preparation for that event (31). The develop
mental cycle of the slime mold Dictyostelium discoideum is
characterized by a precise temporal sequence of gene
products which not only appear at specific times in the cycle
but also disappear when their apparent usefulness is ended
(56). A similar sequential pattern in the activities of a large
number of hydrolytic enzymes has been documented during
the early development of the snail Ilyanassa obsoleta (40).
Animals with life cycles that are marked by gross metamorphic events display differential use of genetic information as
the transition from one developmental phase to the next is
carried out. This behavior is exemplified in phase-specific
proteins that have been identified either antigenically or
electrophoretically during insect (43, 50) and amphibian
(13, 35) life cycles.
As organisms become more complex, their evolutionary
divergence from one another is more apparent in the later
stages than in the early stages of the life cycle. This
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Phasing of Gene Products during Development
generality was formulated in 1828 by K. E. von Baer: "In
the embryo, the general features which are common to all
the members of a group of animals are developed earlier
than the special features which distinguish various mem
bers within the group." The group to which von Baer re
ferred can now be broadened, as some early embryonic
properties appear to be shared across wide taxonomic lines.
Perhaps nowhere has this primitive quality of early em
bryos been so strikingly documented as in the sulfur-me
tabolizing enzymes of the chick embryo. The ability of
living organisms to convert oxidized inorganic sulfur to re
duced organic sulfur is generally restricted to bacteria and
plants. However, the yolk sac of the early chick embryo dis
plays the vestigial enzymatic capability of carrying out this
conversion, and this capability is lost during subsequent
development (12).
The mammalian life cycle, particularly in its initial
phases, is just beginning to be characterized at the genetic
and biochemical levels. However, there is every reason to
expect that transient expression of genetic information
during limited periods of development will also be a feature
of mammalian ontogeny, and that the earliest gene products
will possess a similar primitive quality. Discrete phases in
mammalian development are not easily defined, and their
definition will evidently depend upon whether the frame of
reference is anatomical, physiological, or biochemical. The
embryonic and fetal proteins that reappear in cancer cells
are phase-specific, in that they are normally "phased out"
tRNA methyltransferase activity. Another feature common
to both the embryonic and malignant cell is their agglutinability by various plant lectins (41).
In all of these examples, the unresolved question is
whether the reexpression of embryonic traits is an integral
part of the malignant transformation or is an incidental side
effect. The presence of embryonic gene products in adult
cells does, at the very least, signal a disturbance in normal
patterns of gene expression, and an examination of these
normal patterns is relevant to any attempt to define the
malignant transformation.
It is becoming clear that, contrary to earlier assumptions,
development does not involve a gradual restriction of gene
expression as ontogeny proceeds from one phase to the next.
According to this view, multipotent embryonic cells would
be expected to transcribe wide segments of the genome,
whereas cells examined at later stages would be progres
sively limited in their transcriptive activities. Although data
are not abundant, none of the studies of genetic transcrip
tion during development supports the restriction theory.
As reviewed by Britten and Kohne (8), the reassociation
kinetics of denaturated DNA from higher organisms show
that complementary nucleotide sequences are present in
vastly differing frequencies—or numbers of "copies"—
varying from those present in single copies to those present
in several hundred thousand copies. It is now recognized
that most proteins are specified by DNA sequences present
as single copies, and this DNA makes up one-half to
during the late fetal or early neonatal periods. It is not clear, three-fourths of the total genome (8). It can be shown,
on the other hand, just when these gene products are however, that both unique and repetitive DNA sequences
"phased in," nor what developmental signals may induce are transcribed in most cells (25, 53). The significance of the
their expression under normal circumstances. Since some of RNA transcripts from repetitive sequences is, at the
these proteins are specific to the germ-layer derivation of moment, speculative. Their most likely role is in regulative
the tumor in question, it seems plausible that they are and integrative functions carried on within the cell nucleus.
primitive with respect to that germ layer. For example, The initial efforts to characterize genetic transcription dur
a-fetoprotein has been detected in the yolk sac as well as the ing embryogenesis employed experimental conditions that
liver of the early rat embryo (26); it, along with carcinoem- assayed primarily these repetitive transcripts, rather than
bryonic antigen, may be phased in at the very onset of unique ones. Thus, the full interpretation of the results must
endoderma) differentiation. Other phase-specific proteins await a clearer understanding of the function of repetitive
appear to be synthesized during an even earlier period transcripts in determining cell phenotypes. Nontheless,
preceding overt germ-layer differentiation. A complex pat
these experiments clearly demonstrated that the transcrip
tern of protein synthesis can be detected in the cleaving tion of such sequences is highly stage specific and only
rabbit embryo shortly after egg fertilization (58). These pro
partially overlapping during embryogenesis in both
teins would indeed be most apt to be primitive; some of echinoderms (27, 60) and amphibians (16, 19). For example,
them are synthesized during intervals lasting but a few transcripts present in the blástulashow very little homology
hours. As yet, none of these initial proteins has been con
to those present in the gastrula, and these in turn possess
clusively identified, and it is therefore not known whether only partial identity to those in the neurula or later stages.
they too are resynthesized in the cancer cell.
These studies provided the first argument against the
The malignant cell may express embryonic properties in progressive restriction concept; such a view would predict
addition to those detected immunologically. Embryonic that transcripts present during later ontogeny would possess
forms of tRNA are found in a number of cancers (39, 49). homologs at all earlier stages.
Only within the past few years has the transcription of
Furthermore, the methylation of tRNA is much more
extensive in embryonic and malignant cells than in normal unique-sequence DNA been measured (9, 25, 53). Here
adult cells (6). It has been known for some time that the again, the evidence supports the view that genetic transcrip
activity of liver tRNA methyltransferases decreases during tion during development is best characterized as only
the newborn period (30). We have recently found that tRNA
partially overlapping RNA transcripts derived from quite
methylation also decreases markedly during early em- limited portions of the genome. We have examined the
bryogenesis in the rabbit, at the time of blastocyst forma
transcription of this portion of the genome during the early
tion (38). Thus, mammalian ontogeny appears to contain period of rabbit embryogenesis. Although approximately
several phases which could be defined by fluctuations in 70% of the rabbit genome is composed of unique-sequence
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2045
C. Manes
DNA, only 1.8% of this DNA is transcribed in the
multipotent cells of the rabbit blastocyst (53). As shown in
Chart 1, the rabbit embryo at midgestation, when early
organogénesisis complete, contains transcripts of approxi
mately 2.5% of the unique-sequence DNA. The addition of
blastocyst RNA to this midgestation RNA raises the value
to 3.2%, indicating that there are transcripts in the blas
tocyst which are no longer present at midgestation and that
there are totally new transcripts present at midgestation
which were not contained in the earlier embryo. These
findings are likewise incompatible with the "progressive
restriction" concept of gene expression during development.
They indicate further that a relatively small portion of the
unique information encoded in the genome is required to
support the cell phenotypes in the undifferentiated embryo.
Similarly, it has been shown that the amphibian oocyte,
which is presumably synthesizing RNA templates to sup
port all the protein synthesis necessary for pregastrular
development, utilizes only 1.5% of the unique-sequence
DNA (17).
While actual gene expression cannot be accurately repre
sented as undergoing a progressive restriction during devel
opment, potential gene expression certainly can. The so
matic cell lineages derived from the mammalian zygote
(Chart 2) provide a scheme of the mutually exclusive
"choices" which are required during ontogeny. Becoming
an embryoblast cell, for example, appears to preclude, after
a short labile period, becoming a trophoblast cell; the choice
of the ectoderm pathway rules out becoming an erythrocyte.
Intermediate cell types, or cells displaying two or more
phenotypes simultaneously, are not seen in normal develop
ment. At the moment, there is no inkling as to the molecular
basis of these exclusion rules in genetic expression.
Although it is not possible to specify precisely just how
many unique or repetitive DNA sequences are involved in
these choices, the number may be surprisingly large. The
unique-sequence DNA transcribed by the rabbit blastocyst,
-C
Zygote—
SyneytWrophoblMt
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Adenohypophr»!«
l_fÉM*ïlMM
—¿Ectoderm—¿
4— Neural Crert
_ Ren* Tinut
-
. Cometh«Tfceut
MipoM Tiuue
—¿
Germ Cell»?
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Peñere»
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Luni
Chart 2. Cell lineages derived from the zygote during ontogeny,
illustrating the sequential and mutually exclusive patterns displayed by
differential gene expression.
but no longer transcribed in the midgestation embryo, is
genetic material sufficient to specify some 23,000 different
proteins the size of hemoglobin. The difference between
normal and virus-transformed mouse cells has been found to
involve 5 to 8% of the unique-sequence DNA (28), or
enough to specify as many as 200,000 different proteins.
These are, of course, maximum figures and they do not
indicate how many of these transcripts are present in
polysomes, but they do provide some indication of the
magnitude of the regulatory program involved in supporting
specific cell phenotypes. Whatever model is proposed to
account for the regulation of gene transcription in eukaryotes, it must confront the fact that regulation may involve
large blocks of genes, rather than single genes. Further
more, this coordinated transcription of multiple genes is
accomplished in the absence of "opérons;" the genes
involved are not physically linked on the chromosome (7).
It would appear that the task of integrating the expression
of such a large number of genes might be subject to frequent
error. However, the precise phenotypic exclusion behavior
which is characteristic of normal development is witness
that this integration is generally successful, that the mistake
rate is acceptably low. An excellent example of such
large-scale integration is found in the differentiation of the
imaginai discs of Drosophila. Multiple genes, as defined by
known mutations, are obviously involved in determining the
developmental outcome of each imaginai disc, and this
outcome is highly specific (29). Under certain experimental
iver
conditions, this outcome can be changed, or transdeteril embryo
mined, so that an imaginai disc originally destined to
s ,
become a leg, for example, now becomes a wing. The
£2
s6-d embryo
important point is that this developmental switch is saltato
ry; there is no gradual progression from leg to wing, with
multiple intermediate types. The entire imaginai disc ap
pears to be involved with either/or choices, just as are the
cell types derived from the zygote.
Time
( Hours >
The malignant cell must be viewed against this experi
Chart 1. Hybridization of total, unlabeled rabbit RNA obtained from
the tissues indicated with tritiuted. unique-sequence rabbit DNA. The mental and conceptual background. It is evident that the
reactions reached saturation plateaus in each instance, except with 12-day fibroma that secretes insulin or the lung tumor that secretes
is violating the exclusion rules of
(d) embryo RNA. [Reproduced with the permission of Plenum Publishing adrenocorticotrophin
normal development. Since the tissue of origin of most
Corp.; from a study by Schultz et al. (53)].
<
4-
2046
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Phasing of Gene Products during Development
malignant cells is identifiable, it is further evident that adult
cells do not surrender all of their differentiated properties in
order to become malignant. Thus, the adult colonie cell that
synthesizes carcinoembryonic antigen or the adult liver cell
that synthesizes a-fetoprotein is coexpressing genes which,
by developmental rules, are normally mutually exclusive.
Moreover, the 1 or 2 aberrant gene products that can be
readily identified are almost certainly members of a much
larger block of coordinately expressed genes. Finally, once
the exclusion rules are broached, there would seem to be no
a priori reason to limit gene expression in malignant cells to
only 2 blocks of phase-specific genes; several may be
involved.
The question now posed is whether this disruption of
normal gene regulation is in itself sufficient to account for
the malignant behavior of the cell involved. This question is
tantamount to asking whether cancer is, after all, a
developmental disease. Current theory in developmental
biology maintains, with considerable experimental support,
that the varied phenotypes evolved from the zygote during
ontogeny are accomplished without alteration in the geno
type. With regard to the malignant phenotype, then, it is
possible to ask: Does this phenotype, unlike the others,
require an alteration in the genotype? Or can disturbances in
gene regulation permit the expression of "malignant infor
mation" encoded within the unaltered genotype? Indeed,
can malignant information be shown to be a part of the
normal genome?
There are advocates of the view that the malignant
phenotype does in fact require an alteration in the genotype,
that malignant information is not part of the normal
genome. It is proposed that the genotype of the malignant
cell is altered by the introduction of exogenous (viral)
genetic information (3) or by mutational events within the
DNA (51). In view of the fact that chemical and physical
agents can cause cancer, it is difficult to maintain that
exogenous genetic information is absolutely required for the
malignant transformation. Mutational events, on the other
hand, could conceivably be a common denominator of this
transformation. Since such events are random, one would
expect genetic expression in cancer cells to be "scrambled"
and reversion to normal cell behavior exceedingly rare.
However, as Pierce (46) pointed out several years ago, the
predictable reversibility of a number of malignant pheno
types argues against such a view.
The capacity of teratocarcinoma cells to give rise to
entirely benign progeny was the earliest demonstration of
such regular reversion of malignant cells (46). More re
cently, neuroblastoma cells in suspension culture have been
found to revert to a well-differentiated phenotype simply by
being allowed to attach to the culture dish (52), recalling
older reports in the clinical literature of the occasional
spontaneous conversion of malignant neuroblastomas into
benign ganglioneuromas (15). Squamous cell carcinomas
regularly give rise to "pearls" of benign cells (47). Nondividing, terminally differentiated cells are found in mam
mary carcinomas and can be shown by pulse-chase autoradiography to arise in regular fashion from undifferentiated,
highly malignant precursor cells (62). Mammary tumors in
mice have been shown to be capable of normal glandular
AUGUST
differentiation when induced by normal mouse mesenchyme
(18), and leukemic cells are transformed into normal
granulocytes in the presence of an inducing protein (23). The
simplest explanation for all of these findings is that
alterations in the genotype are not the essence of the
malignant phenotype.
The burden of proof, however, remains with those who
hold that malignant information is encoded in the normal
genome. Logically, there would appear to be 3 possibilities
for generating the malignant phenotype from the unaltered
genotype. It could result from the coexpression in the adult
cell (a) of a gene set normally expressed during early
ontogeny; (b) of combinations of gene sets, any one of which
singly would give rise to a benign phenotype; or (c) of genes
that are normally silent during ontogeny. With regard to the
last possibility, it would be very difficult to prove that a
given gene or gene set is never expressed, even very
transiently, during normal ontogeny. It is also difficult to
understand why evolutionary selection would not long ago
have eliminated genetic information whose only role is to
produce disastrous results. The other 2 alternatives, how
ever, appear to contain more promise.
One way to explore this possibility is to search among the
cell phenotypes evolved during the mammalian life cycle
and to ask whether any of these gene sets regularly yield a
malignant cell. It is not enough that a cell type possess an
antigen that may reappear in the cancer cell. The reexpression in malignant cells of embryonic and fetal antigens
would be primarily of academic interest if these same cells
did not also replicate in an uncontrolled fashion, invade
surrounding tissues, metastasize, and ultimately kill the
host. We must therefore examine the normal descendants of
the zygote for a cell type that displays behavior that can be
described as malignant.
While many embryonic cells during the early period of
morphogenesis display the capacity to invade surrounding
tissues, as epithelial buds invading the surrounding mesen
chyme, or to metastasize, as neural crest cells migrating into
many locations in the growing embryo, by definition, these
activities give rise to predictable forms and cell arrange
ments. The behavior that characterizes the malignant cell is
its apparent autonomy, its disregard for the usual morphogenetic contraints. However, the descendants of the zygote,
include more than strictly embryonic cells. The trophoblast
stem cell (Fig. 1) is an almost immediate and primitive cell
type derived by cleavage of the fertilized egg. Of all the cell
types generated during normal ontogeny, it most closely
approximates the specifications for a malignant phenotype.
In order to perform its role successfully, the trophoblast cell
must invade the endometrium and, at times, fuse with
endometrial cells (5, 22, 48). It must resist immune
rejection by the pregnant host (54), and it must stimulate
local blood flow in the surrounding tissues (24). All
malignant cells, regardless of tissue of origin, share these
properties with the trophoblast cell (14, 24, 61). A wide
variety of human cancers (57) and several virus-transformed
cell lines (2, 20, 45) also appear to share a common surface
antigen with the normal trophoblast and/or early embry
onic cells. The trophoblast, of course, does not normally kill
its host. Either local or hormonal influences induce a degree
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C. Manes
of further differentiation in the trophoblast stem cell (Chart
2), limiting its invasiveness and leading to an elaborate
capacity for endocrine function (44). In the absence of such
influences, the primitive trophoblast can indeed destroy the
uterus (37) and behave, in humans, as choriocarcinoma (44).
Such a cell phenotype, engendered by genetic information
present in the normal mammalian genome, would appear to
resolve the paradox of searching for genes that can be
simultaneously useful and lethal. The doctrine of the
"constancy of the genome" requires that the gene set
specifying the trophoblast phenotype be present in the
zygote and in all its descendants. This genetic information,
however essential it may be for reproductive success in
placental mammals, is obviously not compatible with the
highly organized and morphogenetic behavior expected of
the embryoblast and its derivatives (Chart 2). The propo
nents of the oncogene theory have suggested also that these
hereditary units, reexpressed in malignant cells, may play a
useful although unspecified role in early development (33).
Expression of oncogenes involves the production of C-type
viral particles or of viral core proteins detectable as gs
antigens. A useful role for these genes can be tentatively
assigned as contributing to the trophoblast phenotype. We
find both A- and C-type particles in the rabbit blastocyst
(Fig. 2); the C-type particles are predominantly, if not
exclusively, seen in the trophoblast cells. The developmental
role of these particles, which reappear in many malignant
cell types (34), is further suggested by their presence in
normal mammalian placentas (36). This genetic informa
tion, apparently endogenous to the mammalian genome,
may well be infectious in lower vertebrates (34).
The concept of cancer suggested by these findings is that
it is indeed a developmental disease, that it is not necessary
to invoke alterations in the genotype to account for the
behavior of malignant cells, and that genetic information
that is normally and usefully expressed to accomplish
mammalian placentation is malignant when expressed in
descendants of the embryoblast. The causes of cancer—be
they viral, chemical, physical, or spontaneous—are inter
preted in this view as disrupting mechanisms of gene
regulation and integration in a reversible manner. While it is
ultimately sensible to attempt to prevent the disruptive
actions of these various agents by immunological or envi
ronmental control, the implication of the developmental
view for the therapy of established cancer is that a rational
goal is toward reestablishing regulation while attempting
obliteration. Unfortunately, it is evident that our regulative
techniques are considerably less well developed than our
obliterative techniques.
The reassuring aspect of the work demonstrating the
reversibility of some malignant phenotypes is that the
malignant cell may retain the capacity to respond to
regulatory mechanisms. Just as the transdetermination of
imaginai discs in Drosophila requires cell division (29),
alterations in the transcriptional state of any eukaryotic cell
appear to occur predominantly at the time of DNA
synthesis and/or mitosis (21, 55). Agents that alter genetic
expression in the direction of the malignant phenotype
would be expected to affect dividing cells, principally. Ther
apeutic agents which might be forthcoming to alter genetic
2048
expression in the direction of a benign phenotype should
likewise impinge chiefly upon the dividing cell. Regulatory
agents in normal development appear to be highly specific
with regard to cell type (10). Thus, if the coexpression of
trophoblast genes in the adult cell is found to be necessary
and perhaps sufficient to cause malignant behavior, it
becomes of particular relevance to investigate those influ
ences that regulate the differentiation and replication of the
trophoblast cell during normal placentation.
It was suggested by John Beard, some 72 years ago (4),
that the trophoblast cell, a normal component of the mam
malian life cycle, is the prototype malignant cell. As Whitehead (59) remarked about philosophical systems, they are
almost never refuted, merely abandoned. Perhaps the time
has come for a serious reexamination of this long-aban
doned proposal in the light of current developmental
theory. It is now possible to make predictions about tran
scription of specific DNA sequences in trophoblast or embryoblast cells, as well as in malignant cells, predictions
which are testable by DNA-RNA hybridization techniques.
If the predictions are verified, they will have important
consequences for the regulative therapy of established
cancer.
Acknowledgments
The electron micrographs were reproduced with permission of Jonathan
Van Blerkom of the Department of Molecular, Cellular, and Develop
mental Biology, University of Colorado.
References
1. Alexander, P. Foetal "Antigens" in Cancer. Nature, 235: 137-140,
1972.
2. Ambrose, K. R., Anderson, N. G., and Coggin, J. H., Jr. Interruption
of SV40 Oncogenesis with Human Foetal Antigen. Nature, 233:
194 195, 1971.
3. Baxt, W., Yates, J. W.. Wallace, H. J., Jr., Holland, J. F., and
Spiegelman, S. Leukemia-Specific DNA Sequences in Leukocytes of
the Leukemic Member of Identical Twins. Proc. Nati. Acad. Sei. U.
S., 70: 2629-2632, 1973.
4. Beard, J. Embryological Aspects and Etiology of Carcinoma. Lancet,
/.- 1758-1761, 1902.
5. Billington, W. D. Biology of the Trophoblast. Advan. Reproductive
Physiol., 5: 27-66, 1971.
6. Borek, E. Introduction to Symposium on Transfer RNA and Transfer
RNA Modification in Differentiation and Neoplasia. Cancer Res., 31:
596-597, 1971.
7. Britten, R. J., and Davidson, E. H. Gene Regulation for Higher Cells:
A Theory. Science, 165: 349-357, 1969.
8. Britten, R. J., and Kohne, D. E. Repeated Sequences in DNA. Science,
161: 529-540, 1968.
9. Brown, I. R., and Church, R. B. Transcription of Nonrepeated DNA
During Mouse and Rabbit Development. Develop. Biol., 29: 73-84,
1972.
10. Bullough, W. S. The Chalones: A Review. Nati. Cancer Inst. Mono
graph, 38: 5-16, 1973.
11. Calendar, R. The Regulation of Phage Development. Ann. Rev.
Microbiol., 24: 241-296, 1970.
12. Chapeville, F., and Fromageot, P. "Vestigial" Enzymes during
Embryonic Development. Advan. Enzyme Regulation, 5: 155-168,
1967.
13. Chen, P. S. Patterns of Soluble Proteins and Multiple Forms of
CANCER
RESEARCH
Downloaded from cancerres.aacrjournals.org on June 16, 2017. © 1974 American Association for Cancer Research.
VOL. 34
Phasing of Gene Products during Development
Dehydrogenases in Amphibian Development. J. Exptl. Zool., 168: 36. Kalter. S. S.. Helmke, R. J., Panigel, M., Heberling, R. L., Felsburg.
337-350, 1968.
P. J., and Axelrod, L. R. Observations of Apparent C-Type Particles
in Baboon (Papio cynocephalus) Placentas. Science, 779: 1332-1333,
14. Coggin, J. H., Jr., Ambrose, K. R., Dierlam, P. J., and Anderson, N.
G. Proposed Mechanisms by Which Autochthonous Neoplasms
1973.
Escape Immune Rejection. Cancer Res., 34: 2092-2101, 1974.
37. Kirby, D. R. S., and Cowell, T. P. Trophoblast-Host Interactions. In:
R. Fleischmajer and R. E. Billingham (eds.). Epithelial-Mesenchymal
15. Gushing, H., and Wolbach, S. B. The Transformation of a Malignant
Interactions, pp. 64-77. Baltimore: The Williams & Wilkins Co.,
Paravertebral Sympathicoblastoma into a Benign Ganglioneuroma.
Am. J. Pathol., 3: 203-216, 1927.
1968.
16. Davidson, E. H., Grippa, M., and Mirsky, A. E. Evidence for the 38. Manes, C., and Sharma. O. K. Hypermethylated tRNA in Cleaving
Rabbit Embryos. Nature, 244: 283-284, 1973.
Appearance of Novel Gene Products during Amphibian Blastulation.
Proc. Nati. Acad. Sei. U. S., 60: 152-159, 1968.
39. Mittelman, A. Patterns of Isoaccepting Phenylalanine Transfer RNA
17. Davidson, E. H., and Hough, B. R. Genetic Information in Oocyte
in Human Leukemia and Lymphoma. Cancer Res., 31: 647 650, 1971.
RNA. J. Mol. Biol., 56: 491-506, 1971.
40. Morrill, J. B.. and Norris, E. Electrophoretic Analysis of Hydrolytic
Enzymes in the Ilyanassa Embryo. Acta Embryol. Morphol. Expl., 8:
18. DeCosse, J. J., Gossens, C. L., Kuzma, J. R., and Unsworth, B. R.
232-238, 1965.
Breast Cancer: Induction of Differentiation by Embryonic Tissue.
Science, /S/.-I057-I058, 1973.
41. Moscona, A. A. Embryonic and Neoplastic Cell Surfaces: Availability
19. Denis, H. Gene Expression in Amphibian Development. II. Release of
of Receptors for Concanavalin A and Wheat Germ Agglutinin.
Science, 171: 905-907, 1971.
the Genetic Information in Growing Embryos. J. Mol. Biol., 22:
285-304, 1966.
42. Neville, A. M. Human Tumor Antigens and Their Potential Useful
20. Duff, R., and Rapp, F. Reaction of Serum from Pregnant Hamsters
ness in Modern Medicine. In: B. Björklund(ed.), Immunological
Techniques for Detection of Cancer, pp. 15-31. Stockholm: Bonniers,
with Surface of Cells Transformed by SV40. J. Immunol.. 105:
521-523, 1970.
1973.
21. Ebert, J. D. Levels of Control: A Useful Frame of Perception. In: A. 43. Patel, N. G. Protein Synthesis during Insect Development. Insect
Biochem., /: 391-427, 1971.
A. Moscona and A. Monroy (eds.). Current Topics in Developmental
Biology, Vol. 3, pp. xv-xxv. New York: Academic Press, Inc., 1968. 44. Palillo, R. A., Story, M. T., Hershman, J. M., Delfs, E., and
22. Enders, A. C., and Schlafke. S. Penetration of the Uterine Epithelium
Mattingly, R. F. Hormone Control of Differentiation and Embryonic
during Implantation in the Rabbit. Am. J. Anat., 132:219-240, 1971.
Antigens in Human Placenta! Tumor Cells In Vilro. In: N. G.
23. Fibach, E., Landau, T., and Sachs, L. Normal Differentiation of
Anderson, J. H. Coggin, Jr., E. Cole, and J. W. Holleman (eds.).
Myeloid Leukemic Cells Induced by a Differentiation-Inducing Pro
Embryonic and Fetal Antigens in Cancer, Vol. 2, pp. 45 71. USAEC
tein. Nature New Biol., 237: 276-278, 1972.
Report CONF-720208. Springfield, Va.: United States Department
24. Folkman, J. Tumor Angiogenesis Factor. Cancer Res., 34:
of Commerce, 1972.
2109-2113, 1974.
45. Pearson, G.. and Freeman, G. Evidence Suggesting a Relationship
Between Polyoma Virus-Induced Transplantation Antigen and Nor
25. Gelderman, A. H., Rake, A. V., and Britten, R. J. Transcription of
mal Embryonic Antigen. Cancer Res., 28: 1665-1673, 1968.
Nonrepeated DNA in Neonatal and Fetal Mice. Proc. Nati. Acad.
Sei. U. S., 68: 172-176, 1971.
46. Pierce, G. B. Teratocarcinoma: Model for a Developmental Concept
26. Gitlin, D., Kitzes, J., and Boesman, M. Cellular Distribution of Serum
of Cancer. In: A. A. Moscona and A. Monroy (eds.). Current Topics
a-Fetoprotein in Organs of the Fetal Rat. Nature, 215: 534, 1967.
in Developmental Biology. Vol. 2, pp. 223-246. New York: Academic
Press, Inc., 1967.
27. Glisin, V. R., Glisin, M. V., and Doty, P. The Nature of Messenger
47. Pierce, G. B.. and Wallace, C. Differentiation of Malignant to
RNA in the Early Stages of Sea Urchin Development. Proc. Nati.
Benign Cells. Cancer Res.. 31: 127-134, 1971.
Acad. Sei. U. S., 56: 285-289, 1966.
28. Grady, L. J., and Campbell, W. P. Non-Repetitive DNA Transcrip
48. Potts, M. The Ultrastructure of Egg Implantation. Advan. Reproduc
tive Physiol.. 4: 241-267, 1969.
tion of Mouse Cells Grown in Tissue Culture. Nature New Biol., 243:
49. Rennert, O. M. Transfer RNA's of Embryonic Tissue. Cancer
195-198, 1973.
Res., 31: 637-638, 1971.
29. Hadorn, E. Dynamics of Determination. In: M. Locke (ed.). Major
Problems in Developmental Biology, pp. 85-104. New York: Aca
50. Roberts, D. B. Antigens of Developing Drosophila melanogasler.
Nature, 233: 394-397, 1971.
demic Press, Inc., 1966.
51. Ryser, H. J.-P. Chemical Carcinogenesis. New Engl. J. Med.. 285:
30. Hancock. R. L., McFarland, P., and Fox, R. R. sRNA Methylase
721-734, 1971.
Activity of Embryonic Liver. Experientia, 23: 806-810, 1967.
52.
Schubert,
D.. Humphreys, S., Baroni. C., and Cohn, M. In Vitro
31. Hanson, R. S., Peterson, J. A., and Yousten. A. A. Unique Biochemi
cal Events in Bacterial Sporulation. Ann. Rev. Microbio!., 24: 53-90.
Differentiation of a Mouse Neuroblastoma. Proc. Nati. Acad. Sei. U.
S., 64: 316-323. 1969.
1970.
53. Schultz, G. A., Manes, C., and Hahn, W. E. Estimation of the
32. Holleman, J. W., and Palmer. W. G. Phase-Specific Antigens. In:
Diversity of Transcription in Early Rabbit Embryos. Biochem. Genet.,
N. G. Anderson, J. H. Coggin. Jr., E. Cole, and J. W. Holleman
9: 247-259, 1973
(eds.), Embryonic and Fetal Antigens in Cancer, Vol. 2, pp. 117-126.
USAEC Report Conf-720208. Springfield, Va.: United States De
54. Simmons, R. L. Viviparity, Histocompatibility, and Fetal Survival.
Advan. Biosci., 6: 405-414, 1971.
partment of Commerce, 1972.
55. Stockdale, F. E., and Topper, Y. J. The Role of DNA Synthesis and
33. Huebner, R. J., Kelloff. G. J., Sarma, P. S., Lane. W. T., Turner, H.
Mitosis in Hormone-Dependent Differentiation. Proc. Nati. Acad.
C., Gilden, R. V., Oroszlan, S., Meier, H., Myers, D. D., and Peters,
Sei. U. S., 56: 1283-1289, 1966.
R. L. Group-Specific Antigen Expression during Embryogenesis of the
56. Sussman, M. Some Genetic and Biochemical Aspects of the Regula
Genome of the C-Type RNA Tumor Virus: Implications for On
tory Program for Slime Mold Development. In: A. A. Moscona and
togenesis and Oncogenesis. Proc. Nati. Acad. Sei. U. S., 67. 366-376.
A. Monroy (eds.). Current Topics in Developmental Biology, Vol. I,
1970.
pp. 61-83. New York: Academic Press, Inc., 1966.
34. Huebner, R. J., and Todaro, G. J. Oncogenes of RNA Tumor
Viruses as Determinants of Cancer. Proc. Nati. Acad. Sei. U. S., 57. Tal, C., and Halperin, M. Presence of Serologically Distinct
64: 1087-1094, 1969.
Protein in Serum of Cancer Patients and Pregnant Women. Israel J.
Med. Sci., 6: 708-716, 1970.
35. Inoue, K. Precipitin Reactions and Developmental Arrest by Antisera
58. Van Blerkon, J., and Manes, C. Development of Preimplantation
in Amphibian Embryos. Develop. Biol., 3: 657-683, 1961.
AUGUST
1974
2049
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C. Manes
Rabbit Embryos in Vivo and Vitro. II. A Comparison of Qualitative
Aspects of Protein Synthesis. Develop. Biol., in press.
59. Whitehead, A. N. Process and Reality, p. 9. New York: The Free
Press, 1929.
60. Whitely, A. H., McCarthy, B. J., and Whitely, H. R. Changing
Populations of Messenger RNA during Sea Urchin Development.
Proc. Nati. Acad. Sei. U. S., 55: 519-525, 1966.
61. Wiener, F., Fenyo, E. M., Klein, G., and Harris, H. Fusion of
Tumor Cells with Host Cells. Nature, 238: 155-159, 1972.
62. Wylie,
C.
V.,
Nakane,
P.
K.,
and
Pierce,
G.
B. Degree
of
Differentiation in Nonproliferating Cells of Mammary Carcinoma.
Differentiation, /.- 11-20, 1973.
Fig. 1. Living rabbit embryos photographed at approximately 84 hr following egg fertilization. The embryos are at the early blastocyst stage and
clearly show the initial separation of the products of cleavage into 2 cell populations. T, trophoblast; E, embryoblast.
Fig. 2. In a, a type C virus-like particle is shown "budding" from the cell surface in a rabbit blastocyst. This embryo was exposed in vitro to
bromodeoxyuridine at I x 10 5 M for 3.5 days. These particles are uniform in size (100 nm) and appearance and are typically shed from the surface
adjacent to the zona pellucida (zp). x 155,000. In b, a type C virus-like particle is shown between 2 trophoblast cells of a rabbit embryo at 5.5 days of age.
This embryo was recovered directly from the uterus and had not been exposed to bromodeoxyuridine. x 200.000. In c, is a cluster of cytoplasmic type A
virus-like particles in a trophoblast cell of a rabbit embryo at 4.5 days of age. This embryo was also recovered directly from the uterus and had not been
exposed to bromodeoxyuridine. Clusters of these particles are seen in many trophoblast cells in many different embryos. They are of uniform shape and
size (70 nm) and are always associated with an electron-dense mass of granular material, x 71,000. Inset, x 115,000. RER, rough-surfaced endoplasmic
reticulum; M, mitochondrion; N, nucleus.
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Phasing of Gene Products during Development
Cole Manes
Cancer Res 1974;34:2044-2052.
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