| Better diagnostic and therapeutic targets are needed for lung cancer in order to improve clinical outcomes. Towards this goal, we developed a MALDI-TOF mass spectrometry protein profiling platform to identify proteins which would differentiate tumor from normal lung. Of the proteins we found to be overexpressed, CypA had not been previously implicated in lung cancer and represented a possible novel target for diagnostics and therapeutics.; CypA is a peptidyl-prolyl isomerase (PPIase) with roles in protein folding, subcellular localization, and meiosis. Neoplastic roles may include binding Rb, modulation of historic deacetylase complex activity, resistance to oxidative stress, apoptosis, and aberrant cell signaling via binding of proline residues. CypA is widely expressed, but contains promoter regions which indicate developmental stage- or tissue-specific expression.; Having observed CypA overexpression in tumors, we hypothesized that CypA expression in primary lung tumors might be useful as a prognostic or diagnostic biomarker. No correlation with survival was found with CypA tissue microarray IHC on 234 tumors. However, ubiquitous expression was observed in the tumors. This indicated CypA might be crucial to lung tumorigenesis, and its inhibition might be useful therapeutically.; To determine its tumor biologic relevance, we knocked CypA down with RNAi in 5M2 lung cancer cell lines. In vitro assays showed a modest effect on proliferation and growth in soft agar, but when grown in vivo a prominent decrease in tumor growth was observed. Overexpression of CypA in the S1LEK transformed primary airway epithelial line demonstrated a striking increase in tumor growth in vivo.; We then characterized CypA's role more precisely by quantifying proliferation, angiogenesis and apoptosis in the xenograft tumors by Ki67, CD31, and TUNEL lHC, respectively. Both in vivo and in vitro CypA knockdown correlated with significantly greater apoptosis and less proliferation, and was not correlated with angiogenesis.; To characterize the global in vivo phenotype of CypA knockdown, we compared gene expression between knockdown and scramble control xenograft tumors by cDNA microarray analysis. The resulting differentially expressed genes indicated CypA's involvement in a wide variety of tumor biologic processes.; Finally, in vivo studies using cyclosporine A (CsA), an inhibitor of CypA PPIase activity, showed marked retardation of tumor growth comparable to that induced by CypA knockdown, indicating that CypA may be a potential therapeutic target for NSCLC. |
