title: Suppression of p53 and p21CIP1/WAF1 reduces arsenite-induced aneuploidy.
abstract: Aneuploidy and extensive chromosomal rearrangements are common in human tumors. The role of DNA damage response proteins p53 and p21(CIP1/WAF1) in aneugenesis and clastogenesis was investigated in telomerase immortalized diploid human fibroblasts using siRNA suppression of p53 and p21(CIP1/WAF1). Cells were exposed to the environmental carcinogen sodium arsenite (15 and 20 microM), and the induction of micronuclei (MN) was evaluated in binucleated cells using the cytokinesis-block assay. To determine whether MN resulted from missegregation of chromosomes or from chromosomal fragments, we used a fluorescent in situ hybridization with a centromeric DNA probe. Micronuclei were predominantly of clastogenic origin in control cells regardless of p53 or p21(CIP1/WAF1) expression. MN with centromere signals in cells transfected with NSC siRNA or Mock increased 30% after arsenite exposure, indicating that arsenite induced aneuploidy in the tGM24 cells. Although suppression of p53 increased the fraction of arsenite-treated cells with MN, it caused a decrease in the fraction with centromeric DNA. Suppression of p21(CIP1/WAF1) like p53 suppression decreased the fraction of MN with centromeric DNA. Our results suggest that cells lacking normal p53 function cannot become aneuploid because they die by mitotic arrest-associated apoptosis, whereas cells with normal p53 function that are able to exit from mitotic arrest can become aneuploid. Furthermore, our current results support this role for p21(CIP1/WAF1) since suppression of p21(CIP1/WAF1) caused a decrease in aneuploidy induced by arsenite, suggesting that p21(CIP1/WAF1) plays a role in mitotic exit.
authors.affiliation: Instituto de Investigaciones Biomedicas, Universidad Nacional Autonoma de Mexico, Mexico, D.F., Mexico.
authors.forename: Ana María
authors.initials: AM
authors.lastname: Salazar
authors.forename: Heather L
authors.initials: HL
authors.lastname: Miller
authors.forename: Samuel C
authors.initials: SC
authors.lastname: McNeely
authors.forename: Monserrat
authors.initials: M
authors.lastname: Sordo
authors.forename: Patricia
authors.initials: P
authors.lastname: Ostrosky-Wegman
authors.forename: J Christopher
authors.initials: JC
authors.lastname: States
mesh_terms: D000782:Aneuploidy; D018053:Arsenites / Q000633:toxicity*; D015153:Blotting, Western; D049109:Cell Proliferation; D002478:Cells, Cultured; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics* / Q000378:metabolism; D003703:Demecolcine / Q000633:toxicity; D005347:Fibroblasts; D055785:Gene Knockdown Techniques; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D016685:Mitomycin / Q000633:toxicity; D013723:Teratogens / Q000633:toxicity; D016159:Tumor Suppressor Protein p53 / Q000235:genetics* / Q000378:metabolism
chemical_list: D018053:Arsenites; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D013723:Teratogens; D016159:Tumor Suppressor Protein p53; D016685:Mitomycin; C015001:arsenite; D003703:Demecolcine