A paradoxical outcome of dietary

A paradoxical outcome of dietary SPI exposure is the shorter latency of Wnt1-generated mammary tumors, despite the significant reduction in tumor incidence in SPI-fed mice. We previously reported that in female rats exposed to SPI and administered with the direct acting carcinogen N-methyl-nitrosourea (to induce mammary tumors), SPI reduction of tumor incidence was associated with higher grade tumors in rats that developed tumors (Simmen et al., 2005). Herein, we suggest a plausible explanation for this paradox based on the distinct functional responses of the MaSC-enriched (CD29hiCD24+Lin) epithelial subpopulation to diet. We found that relative to the control diet, exposure to SPI can reduce basal (MaSC-enriched) cell expansion (measured by mammosphere-forming ability) while enhancing its proliferative phenotype (measured by colony-formation assay). The molecular basis for the opposing actions of dietary soy on the same target population is currently unknown, but may involve distinct biological effects of associated bioactive components. Our findings highlight the complex nature of foods and their context-dependent effects and provide a cautionary note when considering dietary/nutritional strategies for the management of breast cancer patients or in women at high risk for the disease. Our approach of utilizing hyperplastic MEC ANA 12 for evaluating dietary effects on the expansion of the basal-enriched (CD29hiCD24+Lin−) MaSC and CSC (CD29hiThy1+CD24+) populations allowed us to demonstrate a potential (predictive) correlation between the sizes of these populations and subsequent risk for mammary tumors. Given this focus, dietary effects on the size of the CSC population in mammary tumors were not assessed. In a recent report, early Wnt1 overexpression was found to drastically alter the epithelial ontogeny of the mammary gland and hence, the developmental fate of mammary stem and progenitor cells (Van Amerongen et al., 2012). Hence, future studies will address whether the dietary effects shown here are recapitulated in normal MaSC of adult mammary glands in wildtype mice, utilizing similar approaches described herein, including limiting dilution transplantation studies for quantitative determination of stem cell frequency. We consider the absence of the latter data as a limitation to the present study. In summary, our in vivo and ex vivo studies provide evidence for the functional impact of diet on specific epithelial subpopulations that may relate to breast cancer risk. Moreover, our findings raise the interesting possibility that by blocking key regulatory nodes linking steroid hormone signaling and inflammation, early dietary interventions can interfere with the expansion of specific epithelial subpopulations with high regenerative/renewal capacity. Our results suggest that diet-regulated cues can be further explored for breast cancer risk assessment and prevention. The following are the supplementary data related to this article.
Acknowledgments The authors thank Dr. Jeffrey M. Rosen (Baylor College of Medicine) for valuable insights and training on mammary stem cell biology and for critical comments on this manuscript, Dr. Frank A. Simmen (UAMS) for helpful discussions during the course of this study, Dr. Andrea Harris (UAMS Flow Core) for assistance with flow cytometry, and Dr. Kartik Shankar (UAMS/ACNC) for technical assistance with gene array analyses. This study was supported by grants from the United States Department of Agriculture [CRIS 6251-5100002-06S, Arkansas Children\'s Nutrition Center]; Department of Defense Breast Cancer Research Program (W81XWH-08-1-0548); University of Arkansas for Medical Sciences (UAMS) Children\'s University Medical Group; and UAMS Translational Research Institute (UL1 RR029884) to R.C.M.S. O.M.R. was supported by a pre-doctoral fellowship from the Department of Defense Breast Cancer Research Program (W81XWH-10-1-0047).
Introduction Most adult tissues are believed to contain adult stem cells that are able to compensate for tissue loss by generating new cells. In renal pathologies, the presence and function of adult renal stem cells may have clinical relevance. In recent years, sources of renal stem/progenitor cells have been suggested to be localized in different portions of the nephron, based on CD133 alone (Bussolati et al., 2005) or coupled with the CD24 surface marker (Sagrinati et al., 2006), or based on the aldehyde dehydrogenase (ALDH) activity (Lindgren et al., 2011). However, markers can fall victim to their promiscuity. In fact, they may be expressed either by stem or more differentiated cells, and often they do not permit the identification of a homogeneous stem cell population. Moreover, for medical applications, it is also crucial to understand the physiological behavior of renal stem cells to appreciate how they change in specific pathological situations, such as renal cell carcinoma. Therefore, it is necessary to source a purified stem cell population. Recent reviews (Snippert and Clevers, 2011; McCampbell and Wingert, 2012) have stressed the importance of selecting the correct approach for the identification of adult stem cells. They proposed that the dual capacity of self-renewal and multipotency should be the only criteria used for stem cell definition, instead of an exclusive initial use of surface markers or signatures. The capacity of self-renewal and multipotency can be evidenced by in vitro clonal growth of cellular spheres from individual stem cells. The sphere-forming assay has already been described for the isolation of normal and cancer stem cells from various tissues, such as the brain (Reynolds and Weiss, 1992), breast (Dontu et al., 2003), pancreas (Rovira et al., 2010) and prostate (Lawson et al., 2007). The model has also been applied to embryonic renal murine cells obtaining clonal spheres that, however, were not able to differentiate towards an epithelial lineage. The same authors never obtained nephrospheres from postnatal murine kidney (Lusis et al., 2010). The sphere-forming assay has also been applied to adult human renal cells, obtaining aggregation of epithelial cells in 3D spheroids unable to display clonal self-renewal and with only tubulogenic potency (Buzhor et al., 2011). Starting from these data, the aim of this paper was to obtain a population enriched with adult renal stem cells through the formation of clonal spheres with an adaptation of sphere-forming assay to human renal tissue. Within the clonal spheres, the quiescent cells have been identified by using PKH26 lyophilic fluorescent dye which is retained by the cells that have a lower tendency to divide (Cicalese et al., 2009; Pece et al., 2010). Among these cells, a subpopulation displaying self-renewal and multipotency has been identified. By exploiting the functional feature of asymmetrical division that define stem cells it allowed the isolation of a purified, homogeneous and more defined human renal stem cell population. These isolated stem cells might become a tool for regenerative medicine in kidney diseases and could represent an important step for a better comprehension of the cellular and molecular bases of renal pathologies, including renal cell carcinoma according to the cancer stem cell theory.