Comprehensive cancer genomics-based screening of new therapeutic targets and biomarkers for lung cancer.

e21031 Background: Since the clinical outcome of advanced lung cancer patients is still poor after standard therapies, development of new anti-cancer drugs with minimum risk of adverse effects and cancer biomarkers for precision medicine is urgently required. Methods: We have been screening new therapeutic target molecules and molecular biomarkers for lung cancers as follows; i) To identify overexpressed genes in lung cancers by the gene expression profile analysis, ii) To verify the target genes for their scarce expression in normal tissues, iii) To validate the clinicopathologic importance of their protein expression by tissue microarray covering 263 lung cancers, and iv) To confirm their function for the growth and/or invasive ability of the lung cancer cells by siRNAs and gene transfection assays. Results: We identified dozens of candidate target molecules and selected a gene encoding protein with a GAP domain, LAPG1 (lung cancer-associated protein with Gap domain 1). Immunohistochemical analysis showed that LAPG1 expression was observed in 69.9% of lung cancers. Moreover positivity of LAPG1 expression was associated with poor prognosis of lung cancer patients. Knockdown of LAPG1 expression by siRNAs suppressed growth of lung cancer cells. Introduction of LAPG1 increased the invasive activity of mammalian cells, indicating that LAPG1 could be a prognostic biomarker and therapeutic target for lung cancers. Conclusions: Comprehensive cancer genomics-based screening could be useful for selection of new cancer biomarkers and molecular targets for developing small molecules, antibodies, nucleic acid drugs, and immunotherapies.