Henry L. Chang

Normal ovarian surface epithelial label-retaining cells exhibit stem/progenitor cell characteristics

Ovulation induces cyclic rupture and regenerative repair of the ovarian coelomic epithelium. This process of repeated disruption and repair accompanied by complex remodeling typifies a somatic stem/progenitor cell-mediated process. Using BrdU incorporation and doxycycline inducible histone2B-green fluorescent protein pulse–chase techniques, we identify a label-retaining cell population in the coelomic epithelium of the adult mouse ovary as candidate somatic stem/progenitor cells. The identified population exhibits quiescence with asymmetric label retention, functional response to estrous cycling in vivo by proliferation, enhanced growth characteristics by in vitro colony formation, and cytoprotective mechanisms by enrichment for the side population. Together, these characteristics identify the label-retaining cell population as a candidate for the putative somatic stem/progenitor cells of the coelomic epithelium of the mouse ovary.

Adult Mouse Myometrial Label‐Retaining Cells Divide in Response to Gonadotropin Stimulation

Conditional deletion of β‐catenin in the Müllerian duct mesenchyme results in a degenerative uterus characterized by replacement of the myometrial smooth muscle with adipose tissue. We hypothesized that the mouse myometrium houses somatic smooth muscle progenitor cells that are hormonally responsive and necessary for remodeling and regeneration during estrous cycling and pregnancy. We surmise that the phenotype observed in β‐catenin conditionally deleted mice is the result of dysregulation of these progenitor cells. The objective of this study was to identify the mouse myometrial smooth muscle progenitor cell and its niche, define the surface marker phenotype, and show a functional response of these cells to normal myometrial cycling. Uteri were labeled with 5‐bromo‐2′‐deoxyuridine (BrdU) and chased for up to 14 weeks. Myometrial label‐retaining cells (LRCs) were observed in the myometrium and stroma throughout the chase period. After 12 weeks, phenotypic analysis of the LRCs by immunofluorescence demonstrated that the majority of LRCs colocalized with α‐smooth muscle actin, estrogen receptor‐α, and β‐catenin. Flow cytometry of myometrial cells identified a myometrial Hoechst 33342 effluxing “side population” that expresses MISRII‐Cre‐driven YFP. Functional response of LRCs was investigated by human chorionic gonadotropin stimulation of week 12 chase mice and demonstrated sequential proliferation of LRCs in the endometrial stroma, followed by the myometrium. These results suggest that conventional myometrial regeneration and repair is executed by hormonally responsive stem or progenitor cells derived from the Müllerian duct mesenchyme.

Müllerian inhibiting substance preferentially inhibits stem/progenitors in human ovarian cancer cell lines compared with chemotherapeutics

Cancer stem cells are proposed to be tumor-initiating cells capable of tumorigenesis, recurrence, metastasis, and drug resistance, and, like somatic stem cells, are thought to be capable of unlimited self-renewal and, when stimulated, proliferation and differentiation. Here we select cells by expression of a panel of markers to enrich for a population with stem cell-like characteristics. A panel of eight was initially selected from 95 human cell surface antigens as each was shared among human ovarian primary cancers, ovarian cancer cell lines, and normal fimbria. A total of 150 combinations of markers were reduced to a panel of three—CD44, CD24, and Epcam—which selected, in three ovarian cancer cell lines, those cells which best formed colonies. Cells expressing CD44, CD24, and Epcam exhibited stem cell characteristics of shorter tumor-free intervals in vivo after limiting dilution, and enhanced migration in invasion assays in vitro. Also, doxorubicin, cisplatin, and paclitaxel increased this enriched population which, conversely, was significantly inhibited by Müllerian inhibiting substance (MIS) or the MIS mimetic SP600125. These findings demonstrate that flow cytometry can be used to detect a population which shows differential drug sensitivity, and imply that treatment of patients can be individualized to target both stem/progenitor cell enriched and nonenriched subpopulations. The findings also suggest that this population, amenable to isolation by flow cytometry, can be used to screen for novel treatment paradigms, including biologic agents such as MIS, which will improve outcomes for patients with ovarian cancer.

Uterine leiomyomas exhibit fewer stem/progenitor cell characteristics when compared with corresponding normal myometrium

Uterine leiomyomas (also known as uterine fibroids) are the most common benign tumors of female reproductive tract and are the single most common indication for hysterectomies. Despite their high prevalence, the exact pathogenesis of these benign tumors is still unknown. One possible mechanism for leiomyoma formation is dysregulation of mesenchymal stem cell activity. Mesenchymal stem cells have been identified in both human and murine uteri and cancer stem cells have been identified in female reproductive malignancies. We compared stem/progenitor cell characteristics in both normal myometrium and the corresponding leiomyoma of patient’s undergoing hysterectomies. We found that leiomyoma cells form fewer mesenchymal stem cell colonies and exhibit less Hoechst dye-excluding side population (SP) activity, which is a function associated with progenitor cells in other tissues, than cells isolated from normal myometrium. Whereas in normal myometrium, we observed heterogeneous expression of CD90, a cell surface marker associated the with differentiation potential of uterine fibroblasts, in leiomyomas, we observed homogenous expression of CD90, suggesting leiomyoma cells are more terminally differentiated. Furthermore, we found that while leiomyoma cells could only produce CD90 expressing cells, both CD90+ and CD90— myometrial cells could reestablish their original heterogeneous CD90 profile when expanded in vitro. These results suggest that normal myometrium contains cells with stem/progenitor cell activities that are absent in leiomyomas.

Mullerian Inhibiting Substance inhibits invasion and migration of epithelial cancer cell lines

OBJECTIVE Given the fact that Mullerian Inhibiting Substance (MIS) causes complex remodeling of the urogenital ridge and regression of the Mullerian ducts during male embryonic development, we examined whether MIS could affect similar cell properties such as migration and invasion that could contribute ultimately to micro-metastasis of cancers arising from Mullerian tissues. MIS receptor expressing cell lines found to be invasive and migratory in vivo are examined in an in vivo assay that is cost-effective. METHODS We designed in vitro and in vivo experiments to determine if MIS inhibited the movement of cancer lines IGROV-1, HEp3, MDA-MB-231, and HT1080 in cell culture invasion/migration chamber assays and in chick embryo metastasis assays. RESULTS MIS, at concentrations below those that inhibit cell proliferation, blocked in vitro invasion and in vivo migration of epithelial cancer cells that express the MIS receptor. CONCLUSIONS While our laboratory has previously established MIS as an inhibitor of cancer cell proliferation using in vitro assays and in vivo xenografts, we now show that MIS can also inhibit in vivo tumor migration.

Serum Müllerian Inhibiting Substance/Anti-Müllerian Hormone levels in patients with adult granulosa cell tumors directly correlate with aggregate tumor mass as determined by pathology or radiology

OBJECTIVES Granulosa cell tumors (GCTs) comprise 2-5% of ovarian tumors. Serum Müllerian Inhibiting Substance (MIS, also known as anti-Müllerian hormone, or AMH) levels have been validated as a marker of GCT recurrence and progression. There has been little correlation between serum MIS/AMH levels and several clinical parameters in GCTs, including tumor burden. We have performed a retrospective review correlating aggregate tumor mass as reported by pathologic examination or by radiology with serum MIS/AMH levels drawn on the date of examination. METHODS We retrospectively identified 32 GCT patients at our institution over the last 15 years who had serum MIS/AMH measurements. Patients who had serum MIS/AMH measurements within three days of surgery or on the same day as abdominal computerized tomography scan (CT) or magnetic resonance imaging (MRI) were further evaluated. RESULTS We found a significant direct correlation between patient serum MIS/AMH levels and gross aggregate tumor mass determined by pathology (slope=15.4+/-6.06, r=0.65, p<0.04) or by radiographic aggregate tumor mass for all data points identified (slope=0.07+/-0.03, r=0.33, p<0.04) and after correcting for selection bias (slope=1.45+/-0.17, r=0.93, p<0.01). We also identified a significant difference between serum MIS/AMH levels between samples drawn the same day as negative and positive abdominal CT or MRI scans (8.16+/-1.54 vs. 158.7+/-32.2 ng/ml, p<0.0001). CONCLUSIONS These data indicate a significant direct correlation between serum MIS/AMH levels and both gross and radiographic aggregate tumor mass in GCT patients. Together with the current literature, the present data argue for a more prominent role for serum MIS/AMH in the management of GCTs.