The underlying mechanism behind age-induced wastage of the human ovarian follicle reserve is unknown. In this study, we identify impaired ATM (ataxia-telengiectasia mutated)-mediated DNA double strand break (DSB) repair as a cause of aging in mouse and human oocytes. We show that DSBs accumulate in primordial follicles with age. In parallel, expression of key DNA DSB repair genes BRCA1, MRE11, Rad51, and ATM, but not BRCA2, decline in single mouse and human oocytes. In BRCA1-deficient mice, reproductive capacity was impaired, primordial follicle counts were lower, and DSBs were increased in remaining follicles with age relative to wild-type mice. Furthermore, oocyte-specific knockdown of BRCA1, MRE11, Rad51 and ATM expression increased DSBs and reduced survival while BRCA1 overexpression enhanced both parameters. Likewise, ovarian reserve was impaired in young women with germline BRCA1 mutations compared to controls as determined by serum concentrations of anti-mullerian hormone. These data implicate DNA DSB repair efficiency as an important determinant of oocyte aging in women.

SummaryWe have shown previously that distinct Mena isoforms are expressed in invasive and migratory tumor cells in vivo and that the invasion isoform (Mena INV ) potentiates carcinoma cell metastasis in murine models of breast cancer. However, the specific step of metastatic progression affected by this isoform and the effects on metastasis of the Mena11a isoform, expressed in primary tumor cells, are largely unknown. Here, we provide evidence that elevated Mena INV increases coordinated streaming motility, and enhances transendothelial migration and intravasation of tumor cells. We demonstrate that promotion of these early stages of metastasis by Mena INV is dependent on a macrophage-tumor cell paracrine loop. Our studies also show that increased Mena11a expression correlates with decreased expression of colony-stimulating factor 1 and a dramatically decreased ability to participate in paracrine-mediated invasion and intravasation. Our results illustrate the importance of paracrine-mediated cell streaming and intravasation on tumor cell dissemination, and demonstrate that the relative abundance of Mena INV and Mena11a helps to regulate these key stages of metastatic progression in breast cancer cells. Journal of Cell Science metastatic progression. Mena is a member of the Ena/VASP family of proteins and binds actin to regulate the geometry and assembly of filament networks through: (1) an anti-capping protein activity (Bear et al., 2002;Barzik et al., 2005; Hansen and Mullins, 2010) that involves binding to profilin and both G-and F-actin; (2) Mena tetramerization, and (3) reduction in the density of actin-related proteins 2 and 3 (Arp2/3)-mediated branching (Gertler et al., 1996;Barzik et al., 2005;Ferron et al., 2007;Pasic et al., 2008;Bear and Gertler, 2009; Hansen and Mullins, 2010). Alternative splicing for the Mena gene has been reported: a 19 amino acid residue insertion just after the EVH1 domain generates the Mena invasion isoform (Mena INV , formerly Mena +++ ) (Gertler et al., 1996;Philippar et al., 2008), whereas a 21 residue insertion in the EVH2 domain generates the Mena11a isoform (Di Modugno et al., 2007). A comparison of the invasive and migratory tumor cells collected in vivo, with primary tumor cells isolated from mouse, rat and human cell-line-derived mammary tumors, revealed that Mena INV expression is upregulated and Mena11a is downregulated selectively in the invasive and migrating carcinoma cell population (Goswami et al., 2009). The differential regulation of Mena isoforms across species suggests that these two isoforms have important roles in invasion and metastasis.In previous studies, we showed that expression of Mena INV in a xenograft mouse mammary tumor promotes increased formation of spontaneous lung metastases from orthotopic tumors and alters the sensitivity of tumor cells to epidermal growth factor (EGF) . We undertook the current study to identify the step(s) in the metastatic cascade that are affected by Mena INV expression and investigate the effect of expression of...

Mena, an actin regulatory protein, functions at the convergence of motility pathways that drive breast cancer cell invasion and migration in vivo. The tumor microenvironment spontaneously induces both increased expression of the MenaINV and decreased expression of Mena11a isoforms in invasive and migratory tumor cells. Tumor cells with this Mena expression pattern participate with macrophages in migration and intravasation in mouse mammary tumors in vivo. Consistent with these findings, anatomical sites containing tumor cells with high levels of Mena expression associated with perivascular macrophages were identified in human invasive ductal breast carcinomas and called TMEM. The number of TMEM sites positively correlated with the development of distant metastasis in humans. Here we demonstrate that mouse mammary tumors generated from EGFP-MenaINV expressing tumor cells are significantly less cohesive and have discontinuous cell-cell contacts compared to Mena11a xenografts. Using the mouse PyMT model we show that metastatic mammary tumors express 8.7 fold more total Mena and 7.5 fold more MenaINV mRNA than early non-metastatic ones. Furthermore, MenaINV expression in fine needle aspiration biopsy (FNA) samples of human invasive ductal carcinomas correlate with TMEM score while Mena11a does not. These results suggest that MenaINV is the isoform associated with breast cancer cell discohesion, invasion and intravasation in mice and in humans. They also imply that MenaINV expression and TMEM score measure related aspects of a common tumor cell dissemination mechanism and provide new insight into metastatic risk.

Oocyte aging has a significant impact on reproductive outcomes both quantitatively and qualitatively. However, the molecular mechanisms underlying the age-related decline in reproductive success have not been fully addressed. BRCA is known to be involved in homologous DNA recombination and plays an essential role in double-strand DNA break repair. Given the growing body of laboratory and clinical evidence, we performed a systematic review on the current understanding of the role of DNA repair in human reproduction. We find that BRCA mutations negatively affect ovarian reserve based on convincing evidence from in vitro and in vivo results and prospective studies. Because decline in the function of the intact gene occurs at an earlier age, women with BRCA1 mutations exhibit accelerated ovarian aging, unlike those with BRCA2 mutations. However, because of the still robust function of the intact allele in younger women and because of the masking of most severe cases by prophylactic oophorectomy or cancer, it is less likely one would see an effect of BRCA mutations on fertility until later in reproductive age. The impact of BRCA2 mutations on reproductive function may be less visible because of the delayed decline in the function of normal BRCA2 allele. BRCA1 function and ataxia-telangiectasia-mutated (ATM)-mediated DNA repair may also be important in the pathogenesis of age-induced increase in aneuploidy. BRCA1 is required for meiotic spindle assembly, and cohesion function between sister chromatids is also regulated by ATM family member proteins. Taken together, these findings strongly suggest the implication of BRCA and DNA repair malfunction in ovarian aging.

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DNA damage is one of the most common insults that challenge all cells, and more so in resting cell-like oocytes. Increased DNA damage in aged oocyte has been shown to negatively impact the reproductive outcomes. The underlying molecular mechanism is still not completely comprehended, but based on the literature, this decline in the aging oocyte is attributed to impaired DNA repair and epigenetic modifications of these genes with increasing age. In this review, we discuss these molecular alterations and the epigenetic modifications in the DNA double strand break repair gene expressions as a mechanism of oocyte aging.

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Background: Breast cancer mortality is largely attributable to the development of systemic, hematogenous metastatic disease. Although nearly 10-15% of patients have an aggressive form disease that metastasizes within three years after initial diagnosis, the clinical manifestations of metastatic disease can appear ten or more years later. To decrease the risk for the emergence of metastatic tumors, nearly 80% of the patients are treated with adjuvant chemotherapy. The clinical benefit is a 3-10% increase in 15-yr survival, depending upon patient age at diagnosis. Currently established prognostic criteria such as the histopathological grade of the tumor or tumor size do not successfully predict systemic metastatic potential. An enrichment of cancer stem cells in the primary tumor has been shown to be a poor prognostic marker in patients. Epithelial to Mesenchymal Transition (EMT) in breast cancer cells have been shown to give rise to cells that have cancer stem cell like properties. Both of these cells types have been shown to be highly invasive. We have identified invasion markers that can predict EMT, drug and radio resistance in breast cancer cells. In this study we are using biomarkers for cancer stem cells (CD44+/CD24−) and markers of invasion (Mena/Mena11a) to identify cancer initiating cells in Fine Needle Aspiration (FNA). We correlate these ratios with a microanatomical structure called Tumor Microenvironment of Metastasis (TMEM) comprising of a direct apposition of an endothelial cell, a cancer cell and a stromal macrophage in the breast cancer tissue. TMEM has been previously reported to strongly correlate with metastasis. Hypothesis: The percentage of CD44+/CD24− expression can be used to estimate the number of cancer stem cells in FNA samples. The ratio of Mena to Mena11a protein can be used as a measurement of tumor cell response to the microenvironment and its metastatic phenotype. Measuring the stem cell biomarkers and Mena isoforms in cells collected by FNA biopsy using FACS and combining that with the assessment of TMEM density we will be able to develop a simple, quick and inexpensive method of determining metastatic potential of an individual tumor. Methods: FNA was conducted on lumpectomy or mastectomy tissues using fine needles, quality of FNA determined by smear staining. Cells were enzymatically digested, fixed and permeabilized. They were then be subjected to flowcytometry analysis using antibodies against stem cell and invasion markers. Rest of the tumor was processed for histopathology and TMEM analysis. Statistical analysis was performed to identify correlation. Results: Our initial results show that there is a strong correlation between CD44+/CD24− cells in the FNA with TMEM scores. We also report a very high correlation with can also be predicted by the ratios of different splice variants of Mena. This method can be easily used in the clinical setting and applied to a number of different biomarkers. 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 4219.