HuR status is a powerful marker for prognosis and response to gemcitabine-based chemotherapy for resected pancreatic ductal adenocarcinoma patients.

BACKGROUND: Pancreatic ductal adenocarcinoma (PDA) is a devastating disease that killed nearly 38,000 people in the United States this past year. OBJECTIVE: Treatment of PDA typically includes surgery and/or chemotherapy with gemcitabine. No reliable biomarker exists for prognosis or response to chemotherapy. Two previously proposed prognostic markers, cyclooxygenase-2 (COX-2) and vascular endothelial growth factor (VEGF), are regulated by Hu protein antigen R (HuR), an mRNA binding protein that we have previously demonstrated to be a promising predictive marker of gemcitabine response. This study was designed to evaluate the clinical utility of HuR, COX-2, and VEGF as potential prognostic and predictive biomarkers for PDA. METHODS: A tissue microarray of 53 PDA specimens from patients who underwent potentially curative pancreatic resection was analyzed. HuR, COX-2, and VEGF status were correlated with clinicopathologic and survival data. We also performed ribonucleoprotein immunoprecipitation assays using an HuR antibody to assess VEGF and COX-2 mRNA binding to HuR in pancreatic cancer cells. RESULTS: Roughly 50% (27/53) of patients had high cytoplasmic HuR expression. These patients had worse pathologic features as assessed by T staging (P = 0.005). Only cytoplasmic HuR status correlated with tumor T staging, whereas VEGF (P = 1.0) and COX-2 (P = 0.39) expression did not correlate with T staging. Additionally, HuR status was an unprecedented positive predictive marker for overall survival in patients treated with gemcitabine, pushing median survival over 45 months in the high cytoplasmic HuR expressing patient population compared with less than 23 months in the low cytoplasmic HuR expressing patient group (P = 0.033 for log-rank test and P = 0.04 in a Cox regression model) for the low versus high cytoplasmic HuR expressing group. We also validated that mRNA transcripts for both VEGF and the gemcitabine metabolizing enzyme, deoxycytidine kinase, are specifically bound by HuR in pancreatic cancer cells. CONCLUSIONS: HuR is a useful prognostic biomarker for PDA patients as indicated by its association with higher tumor T stage. Additionally, HuR status is a robust predictor of outcome for patients with resected PDA in the setting of adjuvant gemcitabine therapy. Finally, HuR binds to VEGF mRNA implying that HuR, in part, regulates VEGF expression in PDA. This study supports the notion that HuR status should be used by clinicians for the individualized treatment of PDA in the future.

An miRNA Expression Signature for the Human Colonic Stem Cell Niche Distinguishes Malignant from Normal Epithelia.

Malignant transformation of tissue stem cells (SC) may be the root of most cancer. Accordingly, we identified miRNA expression patterns in the normal human colonic SC niche to understand how cancer stem cells (CSC) may arise. In profiling miRNA expression in SC-enriched crypt subsections isolated from fresh, normal surgical specimens, we identified 16 miRNAs that were differentially expressed in the crypt bottom, creating an SC signature for normal colonic epithelia (NCE). A parallel analysis of colorectal cancer tissues showed differential expression of 83 miRNAs relative to NCE. Within the 16 miRNA signature for the normal SC niche, we found that miR-206, miR-007-3, and miR-23b individually could distinguish colorectal cancer from NCE. Notably, miR-23b, which was increased in colorectal cancer, was predicted to target the SC-expressed G protein-coupled receptor LGR5. Cell biology investigations showed that miR-23b regulated CSC phenotypes globally at the level of proliferation, cell cycle, self-renewal, epithelial-mesenchymal transition, invasion, and resistance to the colorectal cancer chemotherapeutic agent 5-fluorouracil. In mechanistic experiments, we found that miR-23b decreased LGR5 expression and increased ALDH+ CSCs. CSC analyses confirmed that levels of LGR5 and miR-23b are inversely correlated in ALDH+ CSCs and that distinct subpopulations of LGR5+ and ALDH+ CSCs exist. Overall, our results define a critical function for miR-23b, which, by targeting LGR5, contributes to overpopulation of ALDH+ CSCs and colorectal cancer. Cancer Res; 77(14); 3778-90. ©2017 AACR.