Abstract 3469: Effect of age and mutagen on the enriched murine mammary epithelial stem and progenitor cell population

Abstract

Abstract Epidemiological studies indicated that aging is a significant risk factor for breast cancer. Yet, there is insufficient knowledge on the mechanisms affecting breast cancer initiation and promotion in older women. Recent studies indicated epithelial stem/progenitor cell population, responsible for lifelong tissue maintenance and regeneration, as a target of transformation. It has been reported earlier by serial transplantation of murine mammary tissues that functional mammary outgrowths indicating stem cell function is unaffected by the age of the donor. But it is unclear that whether spontaneous or induced mutagenesis in the aging stem/progenitor cell population has the potential to impair stem/progenitor functions and/or to initiate tumorigenesis. In this study, first we have isolated lineage negative (CD31−CD45−Ter119−) mammary epithelial cells (Lin−MEC) from the thoracic/inguinal mammary glands of young (6 months, n=7) and old (28 months, n=6) mice by serial enzymatic dissociation followed by magnetic nanoparticle separation method (StemCell Technology). These cells were utilized to form mammospheres, representing mammary stem/early progenitor cells. Although the frequency of mammosphere formation remained the same, the number of larger mammospheres (>60µm) from old mice were significantly lower than the young mice, probably indicating decreased stem cell activity in the older population. To study the effect of mutagen in vivo, we treated two young and two old mice with methyl nitrosourea (MNU, 25mg/kg body weight) once a week for three consecutive weeks. Animals were sacrificed one week after the last treatment. Both total and larger mammospheres (>60µm) from the isolated Lin−MEC of the treated older mice were observed in significantly higher number than the treated younger mice. In a recent clinical study larger mammospheres (>50µm) obtained from metastatic breast cancer cells has been correlated to their ability to induce tumors. These Lin−MEC cells were also analyzed and compared for DNA damage by alkaline comet assay and a higher percentage of cells (>10%) with irreversible DNA damage in the older population were observed compared to younger population (<2%) indicating probable lower DNA repair capacity of the former cells. Thus, our preliminary study indicated that enriched stem/progenitor cells in the old mice with decreased in vitro stem cell activity might have the potential to be vulnerable to DNA damage by mutagens and subsequent tumorigenesis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3469.