Download CHROMOSOMAL INSTABILITY AND CANCER CELL STEMNESS

CHROMOSOMAL INSTABILITY AND CANCER CELL STEMNESS UNDER
EXTREME TELOMERE DYSFUNCTION
Roumelioti Fani-Marlen, Chiourea Maria and Gagos Sarantis
Laboratory of Genetics, Center of Basic Research II, Biomedical Research
Foundation of the Academy of Athens, Greece (BRFAA)
Corresponding author’s email: [email protected]
Chromosomal instability (CIN) is the most frequent type of genomic instability in
neoplasia. CIN generates extensive intra-tumor genomic heterogeneity that shapes the
multistep process of neoplasia and burdens current and future onco-therapeutic
strategies. Human tumors and immortalized cell lines utilizing the Alternative
lengthening of telomeres, do not express telomerase activity and exert high rates of
ongoing telomere dysfunction. In ALT cells, numerical chromosomal aberrations are
very frequent, while structural rearrangements affect almost every single
chromosome. This challenging context provides excellent grounds to study telomere
dysfunction driven CIN in a single cell basis. Many cancers are considered to be
driven by cancer stem cells (CSCs) that may differentiate into a variety of cell types
while maintaining the ability to self-renew. To identify putative CSCs in the ALTpathway, we combined single cell analysis by M-FISH/SKY, with a-CGH and
Immunocytochemistry, in two human ALT cell lines, before and after exposure to
ionizing radiation, topoisomerase inhibition, or DNA hyper-replication. Inducible
genotoxic stress was convoyed by increased rates of random structural chromosome
aberrations, polyploidization, and elevated frequencies of cells expressing the
mesenchymal CSC marker CD133. Molecular karyotyping revealed several DNA
damage-induced novel clonal structural chromosomal rearrangements. However by
aCGH, the insulted ALT genome displayed remarkable propensity to maintain the
major genomic imbalances of the control cells. Structural CIN was unequally
dispersed between co-dividing cells both in control and challenged cell cultures.
Mitotic survivors of structural CIN were products of polyploidization reduction and
their percentages corresponded to the fraction of CD133+ cells/population.
Furthermore, enrichment of CD133+ cells in culture, showed significant decrease at
the frequencies of telomere dysfunction foci (TIF) and in random structural CIN,
whereas the rates of whole genome endoreduplication or polyploidy reduction were
highly elevated. Our results demonstrate a continuous process of ALT cancer genome
homeostasis that is related to genotoxic therapy resistance and cancer cell stemness.