Genotoxic stress leads to centrosome amplification in breast cancer cell lines that have an inactive G1/S cell cycle checkpoint.

Centrosome amplification plays a key role in the origin of chromosomal instability during cancer development and progression. In this study, breast cancer cell lines with different p53 backgrounds were used to investigate the relationship between genotoxic stress, G(1)/S cell cycle checkpoint integrity, and the development of centrosome amplification. Introduction of DNA damage in the MCF-7 cell line by treatment with hydroxyurea (HU) or daunorubicin (DR) resulted in the arrest of both G(1)/S cell cycle progression and centriole duplication. In these cells, which carry functional p53, HU treatment also led to nuclear accumulation of p53 and p21(WAF1), retinoblastoma hypophosphorylation, and downregulation of cyclin A. MCF-7 cells carrying a recombinant dominant-negative p53 mutant (vMCF-7(DNp53)) exhibited a shortened G(1) phase of the cell cycle and retained a normal centrosome phenotype. However, these cells developed amplified centrosomes following HU treatment. The MDA-MB 231 cell line, which carries mutant p53 at both alleles, showed amplified centrosomes at the outset, and developed a hyperamplified centrosome phenotype following HU treatment. In cells carrying defective p53, the development of centrosome amplification also occurred following treatment with another DNA damaging agent, DR. Taken together, these findings demonstrate that loss of p53 function alone is not sufficient to drive centrosome amplification, but plays a critical role in this process following DNA damage through abrogation of the G(1)/S cell cycle checkpoint. Furthermore, these studies have important clinical implications because they suggest that breast cancers with compromised p53 function may develop centrosome amplification and consequent chromosomal instability following treatment with genotoxic anticancer drugs.

Amplified centrosomes in breast cancer: a potential indicator of tumor aggressiveness.

Molecular mechanisms leading to genomic instability and phenotypic variation during tumor development and progression are poorly understood. Such instability represents a major problem in the management of breast cancer because of its contribution to more aggressive phenotypes as well as chemoresistance. In this study we analyzed breast carcinomas and tumor-derived cell lines to determine the relationship between centrosome amplification and established prognostic factors. Our results show that centrosome amplification can arise independent of ER or p53 status and is a common feature of aneuploid breast tumors. Centrosome amplification is associated with mitotic spindle abnormalities in breast carcinomas and thus may contribute to genomic instability and the development of more aggressive phenotypes during tumor progression.