Sanaz Memarzadeh

Basal epithelial stem cells are efficient targets for prostate cancer initiation

Prevailing theories suggest that luminal cells are the origin of prostate cancer because it is histologically defined by basal cell loss and malignant luminal cell expansion. We introduced a series of genetic alterations into prospectively identified populations of murine basal/stem and luminal cells in an in vivo prostate regeneration assay. Stromal induction of FGF signaling, increased expression of the ETS family transcription factor ERG1, and constitutive activation of PI3K signaling were evaluated. Combination of activated PI3K signaling and heightened androgen receptor signaling, which is associated with disease progression to androgen independence, was also performed. Even though luminal cells fail to respond, basal/stem cells demonstrate efficient capacity for cancer initiation and can produce luminal-like disease characteristic of human prostate cancer in multiple models. This finding provides evidence in support of basal epithelial stem cells as one target cell for prostate cancer initiation and demonstrates the propensity of primitive cells for tumorigenesis.

Bmi-1 is a crucial regulator of prostate stem cell self-renewal and malignant transformation.

The Polycomb group transcriptional repressor Bmi-1 is often upregulated in prostate cancer, but its functional roles in prostate stem cell maintenance and prostate cancer are unclear. Loss- and gain-of-function analysis in a prostate sphere assay indicates that Bmi-1 expression is required for self-renewal activity and maintenance of p63(+) stem cells. Loss of Bmi-1 blocks the self-renewal activity induced by heightened β-catenin signaling, suggesting that Bmi-1 is required for full activity of another self-renewal pathway. In vivo, Bmi-1 expression is necessary for normal prostate tubule regeneration. Altered self-renewal and proliferation through Bmi-1 modulation diminishes the susceptibility of prostate cells to transformation. In an in vivo prostate regeneration system, Bmi-1 inhibition protects prostate cells from FGF10-driven hyperplasia and slows the growth of aggressive Pten-deletion-induced prostate cancer. We conclude that Bmi-1 is a crucial regulator of self-renewal in adult prostate cells and plays important roles in prostate cancer initiation and progression.

Expression of colony-stimulating factor 1 receptor during prostate development and prostate cancer progression

Colony-stimulating factor-1 receptor (CSF-1R) is the major regulator of macrophage development and is associated with epithelial cancers of the breast and ovary. Immunohistochemistry analysis of murine prostate development demonstrated epithelial expression of CSF-1R during the protrusion of prostatic buds from the urogenital sinus, during the prepubertal and androgen-driven proliferative expansion and branching of the gland, with a decline in older animals. Models of murine prostate cancer showed CSF-1R expression in areas of carcinoma- and tumor-associated macrophages. Several human prostate cancer cell lines and primary cultures of human prostate epithelial cells had low but detectable levels of CSF-1R. Human prostatectomy samples showed low or undetectable levels of receptor in normal glands or benign prostatic hypertrophy specimens. Staining was strongest in areas of prostatic intraepithelial neoplasia or carcinoma of Gleason histological grade 3 or 4. The activated form of the receptor reactive with antibodies specific for phosphotyrosine modified peptide sequences was observed in samples of metastatic prostate cancer. Immunohistochemistry showed strong expression of CSF-1R by macrophage lineage cells, including villous macrophages and the syncytiotrophoblast layer of placenta, Kupper cells in the liver, and histiocytes infiltrating near prostate cancers. These observations correlate CSF-1R expression with changes in the growth and development of the normal and neoplastic prostate.

Urokinase plasminogen activator receptor: Prognostic biomarker for endometrial cancer

Endometrial adenocarcinoma is the most common gynecologic malignancy in the United States. However, reliable diagnostic or prognostic tumor markers have not been identified for endometrial cancer. In this study, we examined whether urokinase plasminogen activator receptor (UPAR), a glycosyl-phosphatidylinositol-linked membrane protein, is a candidate diagnostic or prognostic marker for patients with cancer of the endometrium. Sixty-five surgically excised, formalin-fixed endometrial tissue specimens were accessioned through the Department of Pathology Registry at the University of California, Los Angeles, and analyzed for UPAR expression by using immunohistochemical techniques. A retrospective review was also performed to determine stage and histopathologic grade of disease, recurrence, and mortality. No expression of UPAR protein was present in seven patients with benign neoplasia of the endometrium. UPAR protein expression highly correlated with stage of disease (ungrouped Spearman correlation = 0.625, P < 0.0001): 40% of patients with stage I, 66% of patients with stage II, 100% of patients with stage III, and 85% with stage IV demonstrated the highest level of UPAR expression. Moreover, high UPAR expression positively correlated with grade of disease (ungrouped Spearman correlation = 0.71, P < 0.0001): 29% of grade 1 specimens, 57% of grade 2, and over 90% of specimens with grade 3, the majority representing uterine papillary serous carcinoma and mixed malignant mesodermal tumor. Finally, UPAR protein expression also positively correlated with rate of recurrence and mortality in patients with adenocarcinoma of the endometrium (ungrouped P = 0.034). Our data suggest that UPAR is a useful prognostic marker for biologically aggressive forms of endometrial cancer.

Stem‐Like Epithelial Cells Are Concentrated in the Distal End of the Fallopian Tube: A Site for Injury and Serous Cancer Initiation

The reproductive role of the fallopian tube is to transport the sperm and egg. The tube is positioned to act as a bridge between the ovary where the egg is released and the uterus where implantation occurs. Throughout reproductive years, the fallopian tube epithelium undergoes repetitive damage and regeneration. Although a reservoir of adult epithelial stem cells must exist to replenish damaged cells, they remain unidentified. Here, we report isolation of a subset of basally located human fallopian tube epithelia (FTE) that lack markers of ciliated (β‐tubulin; TUBB4) or secretory (PAX8) differentiated cells. These undifferentiated cells expressed cell surface antigens: epithelial cell adhesion molecule, CD44, and integrin α 6. This FTE subpopulation was fivefold enriched for cells capable of clonal growth and self‐renewal suggesting that they contain the FTE stem‐like cells (FTESCs). A twofold enrichment of the FTESC was found in the distal compared to the proximal end of the tube. The distal fimbriated end of the fallopian tube is a well‐characterized locus for initiation of serous carcinomas. An expansion of the cells expressing markers of FTESC was detected in tubal intraepithelial carcinomas and in fallopian tubes from patients with invasive serous cancer. These findings suggest that FTESC may play a role in the initiation of serous tumors. Characterization of these stem‐like cells will provide new insight into how the FTE regenerate, respond to injury, and may initiate cancer. STEM CELLS2012;30:2487–2497

Differential transformation capacity of Src family kinases during the initiation of prostate cancer

Src family kinases (SFKs) are pleiotropic activators that are responsible for integrating signal transduction for multiple receptors that regulate cellular proliferation, invasion, and metastasis in a variety of human cancers. Independent groups have identified increased expression of individual SFK members during prostate cancer progression, raising the question of whether SFKs display functional equivalence. Here, we show that Src kinase, followed by Fyn kinase and then Lyn kinase, exhibit ranked tumorigenic potential during both paracrine-induced and cell-autonomous–initiated prostate cancer. This quantitative variation in transformation potential appears to be regulated in part by posttranslational palmitoylation. Our data indicate that development of inhibitors against specific SFK members could provide unique targeted therapeutic strategies.

Lymphovascular and perineural invasion in the parametria: A prognostic factor for early-stage cervical cancer

OBJECTIVE To estimate the impact of parametrial lymphovascular and perineural involvement on nodal metastasis and failure pattern of women with early-stage, surgically treated cervical cancer. METHODS Clinical records and pathologic slides of 93 patients with early-stage cervical cancer (2 IA2, 52 IB1, 31 IB2, and 8 IIA) treated with radical hysterectomy and pelvic lymphadenectomy with or without paraaortic lymphadenectomy were reviewed. The study group comprised 80 patients with squamous cell carcinoma and 13 patients with adenocarcinoma of the cervix. Median follow-up time was 33 months. The association among the various histopathologic predictors of outcome was determined with χ2 analysis. The influence of the predictors on outcome was examined with log rank survival methods and the Cox regression model. RESULTS The presence of parametrial lymphovascular space invasion is a predictor of disease in the pelvic (P < .001) and paraaortic (P < .05) lymphatics independently. Large tumor size (greater than 4 cm), parametrial perineural invasion, cervical lymphovascular space invasion, and tumor depth (greater than two thirds) were found to be simultaneous predictors of recurrence on multivariate analysis (P < .05). Using these four binary predictor variables, we have computed a model-based relative risk. Based on this model, the presence of perineural invasion in the parametria more than doubles the risk of recurrence in the cohort of patients with large (greater than 4 cm) tumors (P < .05). In a subset analysis of patients with negative nodal disease, parametrial perineural invasion and tumor size were independent predictors of poor outcome (P < .05). CONCLUSION Presence of parametrial lymphovascular space invasion correlates significantly with the risk of nodal metastasis in women with early-stage cervical cancer. Parametrial perineural invasion is an independent poor prognostic factor. Histopathologic findings within the parametria are a valuable independent predictor of recurrence and thus may influence the selection of patients for adjuvant treatment.

Cell-autonomous activation of the PI3-kinase pathway initiates endometrial cancer from adult uterine epithelium

Epithelial-specific activation of the PI3-kinase pathway is the most common genetic alteration in type I endometrial cancer. In the majority of these tumors, PTEN expression is lost in the epithelium but maintained in tumor stroma. Currently reported PTEN knockout mouse models initiate type I endometrial cancer concomitant with loss of PTEN in both uterine epithelium and stroma. Consequently, the biologic outcome of selectively activating the PI3-kinase pathway in the endometrial epithelium remains unknown. To address this question, we established a malleable in vivo endometrial regeneration system from dissociated murine uterine epithelium and stroma. Regenerated endometrial glands responded to pharmacologic variations in hormonal milieu similar to the native endometrium. Cell-autonomous activation of the PI3-kinase pathway via biallelic loss of PTEN or activation of AKT in adult uterine epithelia in this model was sufficient to initiate endometrial carcinoma. AKT-initiated tumors were serially transplantable, demonstrating permanent genetic changes in uterine epithelia. Immunohistochemistry confirmed loss of PTEN or activation of AKT in regenerated hyperplastic glands that were surrounded by wild-type stroma. We demonstrate that cell-autonomous activation of the PI3-kinase pathway is sufficient for the initiation of endometrial carcinoma in naive adult uterine epithelia. This in vivo model provides an ideal platform for testing the response of endometrial carcinoma to targeted therapy against this common genetic alteration.

Role of autonomous androgen receptor signaling in prostate cancer initiation is dichotomous and depends on the oncogenic signal

The steroid hormone signaling axis is thought to play a central role in initiation and progression of many hormonally regulated epithelial tumors. It is unclear whether all cancer-initiating signals depend on an intact hormone receptor signaling machinery. To ascertain whether cell autonomous androgen receptor (AR) is essential for initiation of prostate intraepithelial neoplasia (PIN), the response of AR-null prostate epithelia to paracrine and cell autonomous oncogenic signals was assessed in vivo by using the prostate regeneration model system. Epithelial-specific loss of AR blocked paracrine FGF10-induced PIN, whereas the add back of exogenous AR restored this response. In contrast, PIN initiated by cell-autonomous, chronic-activated AKT developed independent of epithelial AR signaling. Our findings demonstrate a selective role for AR in the initiation of PIN, dependent on the signaling pathways driving tumor formation. Insights into the role of hormone receptor signaling in the initiation of epithelial tumors may help define this axis as a target for chemoprevention of carcinomas.

An apoptosis-enhancing drug overcomes platinum resistance in a tumour-initiating subpopulation of ovarian cancer.

High-grade serous ovarian cancers (HGSCs) are deadly malignancies that relapse despite carboplatin chemotherapy. Here we show that 16 independent primary HGSC samples contain a CA125-negative population enriched for carboplatin-resistant cancer initiating cells. Transcriptome analysis reveals upregulation of homologous recombination DNA repair and anti-apoptotic signals in this population. While treatment with carboplatin enriches for CA125-negative cells, co-treatment with carboplatin and birinapant eliminates these cells in HGSCs expressing high levels of the inhibitor of apoptosis protein cIAP in the CA125-negative population. Birinapant sensitizes CA125-negative cells to carboplatin by mediating degradation of cIAP causing cleavage of caspase 8 and restoration of apoptosis. This co-therapy significantly improves disease-free survival in vivo compared with either therapy alone in tumour-bearing mice. These findings suggest that therapeutic strategies that target CA125-negative cells may be useful in the treatment of HGSC. Despite normalization of the CA125 serum biomarker at the completion of carboplatin therapy the vast majority of patients with high grade serous ovarian cancers relapse. Here, Janzen et al., identify a sub-population of tumor cells that are CA125 negative, cancer initiating and platinum resistant but readily eliminated with the addition of apoptosis enhancing drugs to carboplatin.