Chinatsu Arima

PURPOSE: In order to aid the development of patient-tailored therapeutics, we attempted to identify a relapse-related signature that allows selection of a group of adenocarcinoma patients with a high probability of relapse. PATIENTS AND METHODS: Whole-genome expression profiles were analyzed in 117 lung adenocarcinoma samples using microarrays consisting of 41,000 probes. A weighted voting classifier for identifying patients with a relapse-related signature was constructed with an approach that allowed no information leakage during each training step, using 10-fold cross-validation and 100 random partitioning procedures. RESULTS: We identified a relapse-related molecular signature represented by 82 probes (RRS-82) through genome-wide expression profiling analysis of a training set of 60 patients. The robustness of RRS-82 in the selection of patients with a high probability of relapse was then validated with a completely blinded test set of 27 adenocarcinoma patients, showing a clear association of high risk RRS-82 with very poor patient prognosis regardless of disease stage. The discriminatory power of RRS-82 was further validated using an additional independent cohort of 30 stage I patients who underwent surgery at a distinct period of time as well as with the Duke data set on a different platform. Furthermore, completely separate training and validation procedures using another data set recently reported by the Director's Challenge Consortium also successfully confirmed the predictive power of the genes comprising RRS-82. CONCLUSION: RRS-82 may be useful for identifying adenocarcinoma patients at very high risk for relapse, even those with cancer in the early stage.

Lung cancers with neuroendocrine (NE) features are often very aggressive but the underlying molecular mechanisms remain elusive. The transcription factor ASH1/ASCL1 is a master regulator of pulmonary NE cell development that is involved in the pathogenesis of lung cancers with NE features (NE-lung cancers). Here we report the definition of the microRNA miR-375 as a key downstream effector of ASH1 function in NE-lung cancer cells. miR-375 was markedly induced by ASH1 in lung cancer cells where it was sufficient to induce NE differentiation. miR-375 upregulation was a prerequisite for ASH1-mediated induction of NE features. The transcriptional coactivator YAP1 was determined to be a direct target of miR-375. YAP1 showed a negative correlation with miR-375 in a panel of lung cancer cell lines and growth inhibitory activities in NE-lung cancer cells. Our results elucidate an ASH1 effector axis in NE-lung cancers that is functionally pivotal in controlling NE features and the alleviation from YAP1-mediated growth inhibition.

We previously identified PSMD2, a subunit of the 19S regulatory complex of proteasomes, as a constituent of a signature associated with the acquisition of metastatic phenotype and poor prognosis in lung cancers. In the present study, we found that knockdown of PSMD2 decreased proteasome activity, and induced growth inhibition and apoptosis in lung cancer cell lines. These effects of siRNA-mediated PSMD2 inhibition were associated with changes in the balance between phosphorylated AKT and p38, as well as with induction of p21. In addition, patients with higher PSMD2 expression had poorer prognosis and a small fraction of lung cancer specimens carried increased copies of PSMD2. Notably, our findings clearly illustrate that lung adenocarcinomas can be divided into two groups; those with and without general upregulation of proteasome pathway genes including PSMD2. This general upregulation was significantly more prevalent in the non-terminal respiratory unit (non-TRU)-type, a recently proposed genetically and clinicopathologically relevant expression profile-defined classification of adenocarcinomas (P < 0.001 by Fisher's exact test). Patients with adenocarcinomas with general upregulation had significantly shorter survival after potentially curative resection (P = 0.0001 by log-rank test) independent of disease stage, as shown by multivariate Cox regression analysis. Our results suggest that PSMD2 may be a good molecular target candidate and that other co-regulated proteasome pathway genes and/or their common regulator(s) might also be potential targets, warranting future study including elucidation of the underlying common regulatory mechanism.