The mechanisms by which Myc overexpression or Pten loss promotes prostate cancer development are poorly understood. We identified the chromatin remodeling protein, ING4, as a crucial switch downstream of Myc and Pten that is required for human prostate epithelial differentiation. Myc-induced transient expression of ING4 is required for the differentiation of basal epithelial cells into luminal cells, while sustained ING4 expression induces apoptosis. ING4 expression is lost in >60% of human primary prostate tumors. ING4 or Pten loss prevents epithelial cell differentiation, which was necessary for tumorigenesis. Pten loss prevents differentiation by blocking ING4 expression, which is rescued by ING4 re-expression. Pten or ING4 loss generates tumor cells that co-express basal and luminal markers, indicating prostate oncogenesis occurs through disruption of an intermediate step in the prostate epithelial differentiation program. Thus, we identified a new epithelial cell differentiation switch involving Myc, Pten, and ING4, which when disrupted leads to prostate tumorigenesis. Myc overexpression and Pten loss are common genetic abnormalities in prostate cancer, whereas loss of the tumor suppressor ING4 has not been reported. This is the first demonstration that transient ING4 expression is absolutely required for epithelial differentiation, its expression is dependent on Myc and Pten, and it is lost in the majority of human prostate cancers. This is the first demonstration that loss of ING4, either directly or indirectly through loss of Pten, promotes Myc-driven oncogenesis by deregulating differentiation. The clinical implication is that Pten/ING4 negative and ING4-only negative tumors may reflect two distinct subtypes of prostate cancer. Cancer Res; 74(12); 1–12. ©2014 AACR.

Hepatocellular carcinoma (HCC), one of the leading causes of cancer-related death, develops from premalignant lesions in chronically damaged livers. Although it is well established that FGF19 acts through the receptor complex FGFR4-β-Klotho (KLB) to regulate bile acid metabolism, FGF19 is also implicated in the development of HCC. In humans, FGF19 is amplified in HCC and its expression is induced in the liver under cholestatic and cirrhotic conditions. In mice, ectopic overexpression of FGF19 drives HCC development in a process that requires FGFR4. In this study, we describe an engineered FGF19 (M70) that fully retains bile acid regulatory activity but does not promote HCC formation, demonstrating that regulating bile acid metabolism is distinct and separable from tumor-promoting activity. Mechanistically, we show that FGF19 stimulates tumor progression by activating the STAT3 pathway, an activity eliminated by M70. Furthermore, M70 inhibits FGF19-dependent tumor growth in a rodent model. Our results suggest that selectively targeting the FGF19–FGFR4 pathway may offer a tractable approach to improve the treatment of chronic liver disease and cancer. Cancer Res; 74(12); 1–11. ©2014 AACR.

The tumor suppressor p53 and miRNAs are linked through a complex network. Several miRNAs modulate p53 expression, while p53 regulates the transcription and/or biogenesis of several other miRNAs. Here, we report the development of a cell-based assay used with a library of human miRNA mimics in a high-throughput screen for miRNAs that modulate p53 expression. Overexpression of miRNA (miR)-542-3p in cancer cells elevated p53 expression, stimulated the expression of p53 targets, and inhibited cell proliferation. Mechanistically, miR-542-3p increased p53 protein stability by weakening interactions between p53 and its negative regulator MDM2. Furthermore, miR-542-3p suppressed ribosome biogenesis by downregulating a subset of ribosomal proteins such as RPS23, leading to upregulation of RPL11 and stabilization of p53. The 3′untranslated region in the RPS23 transcript contained a miR-542-3p–binding site, suggesting that RPS23 is a direct target of miR-542-3p. Our results define miR-542-3p as an important new positive regulator of p53 with potential applications in cancer treatment. Cancer Res; 74(12); 1–10. ©2014 AACR.

Prostate cancer remains the second leading cause of cancer death in American men and there is an unmet need for biomarkers to identify patients with aggressive disease. In an effort to identify biomarkers of recurrence, we performed global RNA sequencing on 106 formalin-fixed, paraffin-embedded prostatectomy samples from 100 patients at three independent sites, defining a 24-gene signature panel. The 24 genes in this panel function in cell-cycle progression, angiogenesis, hypoxia, apoptosis, PI3K signaling, steroid metabolism, translation, chromatin modification, and transcription. Sixteen genes have been associated with cancer, with five specifically associated with prostate cancer (BTG2, IGFBP3, SIRT1, MXI1, and FDPS). Validation was performed on an independent publicly available dataset of 140 patients, where the new signature panel outperformed markers published previously in terms of predicting biochemical recurrence. Our work also identified differences in gene expression between Gleason pattern 4 + 3 and 3 + 4 tumors, including several genes involved in the epithelial-to-mesenchymal transition and developmental pathways. Overall, this study defines a novel biomarker panel that has the potential to improve the clinical management of prostate cancer. Cancer Res; 74(12); 1–10. ©2014 AACR.

Women with benign proliferative breast disease (BPBD) are at increased risk for developing breast cancer. Evidence suggests that accumulation of adipose tissue can influence breast cancer development via hyperinsulinemia, increased estrogen, and/or inflammation. However, there are limited data investigating these pathways with respect to risk of BPBD. We evaluated serologic markers from these pathways in a case–control study of postmenopausal women nested within the Women’s Health Initiative Clinical Trial. Cases were the 667 women who developed BPBD during follow-up, and they were matched to 1,321 controls. Levels of insulin, estradiol, C-reactive protein (CRP), and adiponectin were measured in fasting serum collected at baseline. Conditional logistic regression models were used to estimate ORs for the association of each factor with BPBD risk. Among nonusers of hormone therapy, fasting serum insulin was associated with a statistically significant increase in risk of BPBD (OR for highest vs. lowest quartile = 1.80; 95% confidence interval, CI, 1.16–2.79; Ptrend = 0.003) as were levels of estradiol (OR for highest vs. lowest tertile = 1.89; 95% CI, 1.26–2.83; Ptrend = 0.02) and CRP (OR for highest vs. lowest quartile = 2.46; 95% CI, 1.59–3.80; Ptrend < 0.001). Baseline adiponectin level was inversely associated with BPBD risk (OR for highest vs. lowest quartile = 0.47; 95% CI, 0.31–0.71; Ptrend < 0.001). These associations persisted after mutual adjustment, but were not observed among users of either estrogen alone or of estrogen plus progestin hormone therapy. Our results indicate that serum levels of estrogen, insulin, CRP, and adiponectin are independent risk factors for BPBD and suggest that the estrogen, insulin, and inflammation pathways are associated with the early stages of breast cancer development. Cancer Res; 74(12); 1–11. ©2014 AACR.