Search

The disabled homolog 2 (DAB2) gene was recently identified as a tumor suppressor gene with its expression downregulated in multiple cancer types. The role of DAB2 in lung tumorigenesis, however, is not fully characterized, and the mechanisms of DAB2 dysregulation in lung cancer are not defined. Here we show that low DAB2 levels in lung tumor specimens are significantly correlated with poor patient survival, and that DAB2 overexpression significantly inhibits cell growth in cultured lung cancer cells, indicating its potent tumor suppressor function. We next identify that microRNA miR-93 functions as a potent repressor of DAB2 expression by directly targeting the 3'UTR of the DAB2 mRNA. Using in vitro and in vivo approaches, we demonstrate that miR-93 overexpression has an important role in promoting lung cancer cell growth, and that its oncogenic function is primarily mediated by downregulating DAB2 expression. Our clinical investigations further indicate that high tumor levels of miR-93 are correlated with poor survival of lung cancer patients. The correlations of both low DAB2 and high miR-93 expression levels with poor patient survival strongly support the critical role of the miR-93/DAB2 pathway in determining lung cancer progression.

Purpose: Prospectively identifying who will benefit from adjuvant chemotherapy (ACT) would improve clinical decisions for non-small cell lung cancer (NSCLC) patients. In this study, we aim to develop and validate a functional gene set that predicts the clinical benefits of ACT in NSCLC., Experimental Design: An 18-hub-gene prognosis signature was developed through a systems biology approach, and its prognostic value was evaluated in six independent cohorts. The 18-hub-gene set was then integrated with genome-wide functional (RNAi) data and genetic aberration data to derive a 12-gene predictive signature for ACT benefits in NSCLC., Results: Using a cohort of 442 stage I to III NSCLC patients who underwent surgical resection, we identified an 18-hub-gene set that robustly predicted the prognosis of patients with adenocarcinoma in all validation datasets across four microarray platforms. The hub genes, identified through a purely data-driven approach, have significant biological implications in tumor pathogenesis, including NKX2-1, Aurora Kinase A, PRC1, CDKN3, MBIP, and RRM2. The 12-gene predictive signature was successfully validated in two independent datasets (n = 90 and 176). The predicted benefit group showed significant improvement in survival after ACT (UT Lung SPORE data: HR = 0.34, P = 0.017; JBR.10 clinical trial data: HR = 0.36, P = 0.038), whereas the predicted nonbenefit group showed no survival benefit for 2 datasets (HR = 0.80, P = 0.70; HR = 0.91, P = 0.82)., Conclusions: This is the first study to integrate genetic aberration, genome-wide RNAi data, and mRNA expression data to identify a functional gene set that predicts which resectable patients with non-small cell lung cancer will have a survival benefit with ACT.

Kinases can phosphorylate and regulate androgen receptor activity during prostate cancer progression. In particular, we showed that glycogen synthase kinase-3 beta phosphorylates the androgen receptor, thereby inhibiting androgen receptor-driven transcription. Conversely, the glycogen synthase kinase-3 beta inhibitor lithium chloride suppressed the glycogen synthase kinase-3 beta-mediated phosphorylation of the androgen receptor, thereby enabling androgen receptor-driven transcription to occur. The androgen receptor hinge and ligand-binding domains were important for both the phosphorylation and the inhibition of transcriptional activity of the receptor by glycogen synthase kinase-3 beta. Furthermore, androgen receptor phosphorylation was augmented by LY294002, an indirect inhibitor of protein kinase B/Akt that inhibits glycogen synthase kinase-3 beta. We also showed that the mutation of various phosphorylation sites on glycogen synthase kinase-3 beta affected the ability of these mutants to co-distribute with the androgen receptor in the cell nucleus, also that both glycogen synthase kinase-3beta and androgen receptor proteins can be found in cell nuclei of prostate cancer tissue samples. Because glycogen synthase kinase-3 beta activity is suppressed after the enzyme is phosphorylated by protein kinase B/Akt and Akt activity frequently increases during the progression of prostate cancer, nullification of the glycogen synthase kinase-3 beta-mediated suppression of androgen receptor activity by Akt likely contributes to prostate cancer progression.