cp-673-451 and Carcinoma--Non-Small-Cell-Lung

Platelet-derived growth factor receptors (PDGFRs) are abundantly expressed by stromal cells in the non-small cell lung cancer (NSCLC) microenvironment, and in a subset of cancer cells, usually with their overexpression and/or activating mutation. However, the effect of PDGFR inhibition on lung cancer cells themselves has been largely neglected. In this study, we investigated the anticancer activity of CP-673451, a potent and selective inhibitor of PDGFRβ, on NSCLC cell lines (A549 and H358) and the potential mechanism. The results showed that inhibition of PDGFRβ by CP-673451 induced a significant increase in cell apoptosis, accompanied by ROS accumulation. However, CP-673451 exerted less cytotoxicity in normal lung epithelial cell line BEAS-2B cells determined by MTT and apoptosis assay. Elimination of ROS by NAC reversed the CP-673451-induced apoptosis in NSCLC cells. Furthermore, CP-673451 down-regulated the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) probably through inhibition of PI3K/Akt pathway. Rescue of Nrf2 activity counteracted the effects of CP-673451 on cell apoptosis and ROS accumulation. Silencing PDGFRβ expression by PDGFRβ siRNA exerted similar effects with CP-673451 in A549 cells, and when PDGFRβ was knockdowned by PDGFRβ siRNA, CP-673451 produced no additional effects on cell viability, ROS and GSH production, Nrf2 expression as well as PI3K/Akt pathway activity. Specifically, Nrf2 plays an indispensable role in NSCLC cell sensitivity to platinum-based treatments and we found that combination of CP-673451 and cisplatin produced a synergistic anticancer effect and substantial ROS production in vitro. Therefore, these results clearly demonstrate the effectiveness of inhibition of PDGFRβ against NSCLC cells and strongly suggest that CP-673451 may be a promising adjuvant chemotherapeutic drug.

Topics: A549 Cells; Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Benzimidazoles; Carcinoma, Non-Small-Cell Lung; Cell Survival; Cisplatin; Dose-Response Relationship, Drug; Drug Synergism; Gene Expression Regulation, Neoplastic; Glutathione; Humans; Lung Neoplasms; NF-E2-Related Factor 2; Oxidative Stress; Phosphatidylinositol 3-Kinase; Proto-Oncogene Proteins c-akt; Quinolines; Reactive Oxygen Species; Receptor, Platelet-Derived Growth Factor beta; RNA Interference; Signal Transduction

NSCLC cells with a mesenchymal phenotype have shown a marked reduction in sensitivity to EGFR inhibitors, though the molecular rationale has remained obscure. Here we find that in mesenchymal-like tumor cells both tyrosine phosphorylation of EGFR, ErbB2, and ErbB3 signaling networks and expression of EGFR family ligands were decreased. While chronic activation of EGFR can promote an EMT-like transition, once having occurred EGFR family signaling was attenuated. We investigated the mechanisms by which mesenchymal-like cells bypass EGFR signaling and acquire alternative routes of proliferative and survival signaling. Mesenchymal-like NSCLC cells exhibit aberrant PDGFR and FGFR expression and autocrine signaling through these receptors can activate the MEK-ERK and PI3K pathways. Selective pharmacological inhibition of PDGFR or FGFR receptor tyrosine kinases reduced cell proliferation in mesenchymal-like but not epithelial NSCLC cell lines. A metastable, reversible EMT-like transition in the NSCLC line H358 was achieved by exogenous TGFbeta, which served as a model EMT system. The H358/TGFbeta cells showed many of the attributes of established mesenchymal-like NSCLC cells including a loss of cell-cell junctions, a loss of EGF-family ligand expression, a loss of ErbB3 expression, increased EGFR-independent Mek-Erk pathway activation and reduced sensitivity to EGFR inhibition. Notably an EMT-dependent acquisition of PDGFR, FGFR and TGFbeta receptors in H358/TGFbeta cells was also observed. In H358/TGFbeta cells both PDGFR and FGFR showed functional ligand stimulation of their intrinsic tyrosine kinase activities. The findings of kinase switching and acquired PDGFR and FGFR signaling suggest investigation of new inhibitor combinations to target NSCLC metastases.

Topics: Benzimidazoles; Carcinoma, Non-Small-Cell Lung; Cell Proliferation; Chromatography, Liquid; Drug Resistance, Neoplasm; ErbB Receptors; Erlotinib Hydrochloride; Humans; Immunoblotting; Lung Neoplasms; Mesoderm; Mitogen-Activated Protein Kinase Kinases; Mitogen-Activated Protein Kinases; Phosphorylation; Protein Kinase Inhibitors; Protein-Tyrosine Kinases; Proto-Oncogene Proteins c-akt; Pyrimidines; Quinazolines; Quinolines; Receptor, ErbB-2; Receptor, ErbB-3; Receptors, Fibroblast Growth Factor; Receptors, Platelet-Derived Growth Factor; Respiratory Mucosa; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Signal Transduction; Spectrometry, Mass, Electrospray Ionization; Thiophenes; Transforming Growth Factor beta; Tumor Cells, Cultured