Short- and long-term effects of Streptozotocin on mammalian telomeres

BOLZAN, A.D.

Montevideo

Congreso; X Congreso de la Asociación Latinoamericana de Mutagénesis, Carcinogénesis y Teratogénesis Ambiental (ALAMCTA); 2016

ALAMCTA

Telomeres are specialized nucleoproteic complexes localized at the physical ends of linear eukaryotic chromosomes that maintain their stability and integrity, protecting them from degradation, recombination or fusion with other chromosomes. Since telomeres play a fundamental role in maintaining genomic stability, the studyof telomere instability in cells exposed to antineoplastic drugs is of great importance to understand the genomic instability associated with chemotherapy regimens. Therefore, we carried out several studies aimed to determine whether antineoplastic drugs induce short- (first division cells after treatment) and long-term (up to 28 days after treatment) telomere instability in mammalian cells. In this lecture, we will summarize our main results obtained with the antineoplastic and diabetogenic drug streptozotocin (STZ) in Chinese hamster, rat and human cells, and provide some insights into their significance for chemotherapeutic regimens against cancer based on this compound. To this end, we analyzed chromosomal aberrations involving telomeres in several mammalian cell lines exposed to different concentrations of STZ. Chromosomal aberrations were detected using PNA-FISH with a pan-telomeric probe [Cy3(CCCTAA)3] to detect (TTAGGG)n repeats. Insome cases, we also determined the activity of telomerase (by the TRAP assay) and telomere length (by Flow-FISH or RT-PCR). Cytogenetic analysis revealed a higher frequency of chromosomal aberrations involving telomeres in STZ-exposed cells vs. untreated cells, both in short- and long-term cell cultures. Long-term studies (up to 15 days after treatment) in rat cells showed induction of telomere dysfunction-related aberrations by STZ, mainly in the form of telomere FISH signal loss and duplications, most of them chromatid-type aberrations. Overall, our results show that STZ induces short-term (by chromosome breakage at one or both ends, causing telomere loss) and long-term telomere instability (by telomere dysfunction) in mammalian cells. Neither telomere length nor telomerase activity is related to the telomere dysfunction induced by STZ.