Download Cell Biology and Cancer

Cell Biology and
Cancer
What is cancer?
• Cancer is a group of more than 100 diseases that
develop across time and involve the
uncontrolled division of the body’s cells and that
are able to invade other tissues
• Cancer begins when a cell breaks free from the
normal restraints on cell division and begins to
follow its own agenda for proliferation
(multiply).
What is a tumor?
• A tumor is a mass of cells.
• In situ cancer- means the abnormal cells
remain within the tissue in which it
originated.
• Invasive cancer- when the abnormal cells
begin to invade nearby tissues.
Types of Cancer
• Benign – Non-cancerous tumor
• Malignant - tumors capable of spreading by
invasion and metastasis. By definition, the
term “cancer” applies only to malignant
tumors
• Metastatic - ability of cancer cells to
penetrate into lymphatic and blood vessels,
circulate through the bloodstream and then
invade normal tissues elsewhere in the body
• Type depends on cause and location
• Each has its own growth rate and prognosis and
treatability
• Incidence increases with age
• Tumors threaten an individual's life when the
growth disrupts the tissues and organs needed
for survival
• Inherited predisposition – can inherit a cancersusceptible mutation (breast, ovarian)
Research
• Over the last 3-4 decades, research has
revolutionized our understanding of cancer
• Success largely due to the application of the
techniques of molecular biology
• Today we know cancer is a disease of molecules
and genes
• Our increasing understanding of these genes
makes it possible for development of new
strategies for preventing, forestalling and even
correcting the changes that lead to cancer
Clues from epidemiology
• In 1775, a high incidence of scrotal cancer was
described among men who worked as chimney
sweepers
• In the mid-1800’s, lung cancer was observed at
alarmingly high rates among miners in German.
• At the end of the 19th century, using snuff and
cigars was thought to be closely associated with
cancers of the mouth and throat
• These observations and others suggested that
the origin or causes of cancer may lie outside the
body, and more importantly, they could be
linked to identifiable and even preventable
causes
• These ideas led to a widespread search for
agents that might cause cancer
• An early notion, prompted by the discovery that
bacteria caused a variety of human diseases,
suggested cancer was an infectious disease
• Another idea was that cancer arises from
chronic irritation of tissues
• This view received strong support with the
discovery of X-rays in 1895 and the observation
that exposure to this form of radiation could
induce localized tissue damage, which could lead
in turn to the development of cancer
• Carcinogens – cancer-causing agent
• Another view is that it is hereditary
• In 1910, a submicroscopic agent was
isolated from a chicken tumor and found
that it could induce new tumors in healthy
chickens
• This theory led scientists to find out that
an agent known as the Rous Sarcoma virus
is one of several viruses that can act as a
causative factor in the development of
cancer
Clues from cell biology
• Field of study that has contributed to growing
understanding of cancer
• Cancer cells are indigenous cells—abnormal
cells that arise from the body’s normal tissues.
• All malignant tumors are monoclonal in origin
(cells are derived from a single ancestral cell that
somehow underwent conversion from a normal
to a cancerous state)
Development of cancer
• The development of cancer occurs as a result of
a series of clonal (monoclonal) expansions from
a single ancestral cell
• Although a tumor is monoclonal, it may contain
a large number of cells with diverse
characteristics
• Another possibility is that cancer develops when
many individual cells become cancerous or
polyclonal
Normal cells vs. cancerous cells
• Key difference in cells – cancer cells have lost
the restraints on growth that characterize normal
cells
• Cancerous cells look and act differently
• In normal cells, the nucleus is only 1/5th the size
of the cell.
• In cancerous cells, the nucleus may occupy most
of the cells volume