Transcriptional factor nuclear factor-kappaB (NF-κB) plays a crucial role in human breast cancer cell invasion and metastasis. The carboxyl terminus of Hsc70-interacting protein (CHIP) is a U-box-type ubiquitin ligase that induces ubiquitination and proteasomal degradation of its substrate proteins. In this study, we investigated the role of CHIP in the NF-κB pathway in the invasion of MDA-MB-231 cells, a highly aggressive breast cancer cell line. We showed that overexpression of CHIP significantly inhibits the invasion of the MDA-MB-231 cells. The overexpression of CHIP suppressed expression of urokinase plasminogen activator (uPA) and matrix metalloproteinase-9 (MMP-9) in MDA-MB-231 cells. Moreover, CHIP strongly inhibited the nuclear localization and the transcriptional activity of NF-κB. The activation of the IkappaB kinase complex (IKK) was also blocked by CHIP overexpression. Importantly, CHIP overexpression resulted in a significant decrease in the level of TNF receptor-associated factor 2 (TRAF2), an upstream key player in the NF-κB pathway. However, the level of TRAF2 was restored after treatment with a proteasome inhibitor, MG-132. Moreover, CHIP overexpression promoted the ubiquitination of TRAF2. We also found cell invasion significantly decreased in cells transfected with TRAF2 small interfering RNA (siRNA). In contrast, when CHIP expression was suppressed by siRNA in poorly invasive MCF-7 cells, cell invasion significantly increased in conjunction with enhanced NF-κB activation and TRAF2 levels. Taken together, these results suggest that CHIP regulates NF-κB-mediated cell invasion via the down-regulation of TRAF2.

Based on these findings, we conclude that CHIP is a suppressor of Met function, serving to regulate cellular receptor levels by promoting Met receptor degradation.

Dacomitinib, an irreversible pan-HER inhibitor, had shown modest clinical activity in squamous cell carcinoma of head and neck (SCCHN) patients. Therefore, validated predictive biomarkers are required to identify patients most likely to benefit from this therapeutic option. To characterize the genetic landscape of cisplatin-treated SCCHN genomes and identify potential predictive biomarkers for dacomitinib sensitivity, we performed whole exome sequencing on 18 cisplatin-resistant metastatic SCCHN tumors and their matched germline DNA. Platinum-based chemotherapy elevated the mutation rates of SCCHN compared to chemotherapy-naïve SCCHNs. Cisplatin-treated SCCHN genomes uniquely exhibited a novel mutational signature characterized by C:G to A:T transversions at CCR sequence contexts that may have arisen due to error-prone translesional synthesis. Somatic mutations in REV3L, the gene encoding the catalytic subunit of DNA polymerase ζ involved in translesional synthesis, are significantly enriched in a subset of patients who derived extended clinical benefit to dacomitinib (P = 0.04). Functional assays showed that loss-of-function of REV3L dramatically enhanced the sensitivity of SCCHN cells to dacomitinib by the loss of both translesion synthesis and homologous recombination pathways. Our data suggest that the ‘platinum’ mutational signature and inactivation of REV3L may inform treatment options in patients of recurrent SCCHN.

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RET rearrangement is a newly identified oncogenic mutation in lung adenocarcinoma (LADC). Activity of dovitinib (TKI258), a potent inhibitor of FGFR, VEGFR, and PDGFR, in RET-rearranged LADC has not been reported. The aims of the study are to explore antitumor effects and mechanisms of acquired resistance of dovitinib in RET-rearranged LADC. Using structural modeling and in vitro analysis, we demonstrated that dovitinib induced cell-cycle arrest at G 0 -G 1 phase and apoptosis by selective inhibition of RET kinase activity and ERK1/2 signaling in RET-rearranged LC-2/ad cells. Strong antitumor effect of dovitinib was observed in an LC-2/ad tumor xenograft model. To identify the acquired resistance mechanisms to dovitinib, LC-2/ad cells were exposed to increasing concentrations of dovitinib to generate LC-2/ad DR cells. Gene-set enrichment analysis of gene expression and phosphor-kinase revealed that Src, a central gene in focal adhesion, was activated in LC-2/ad DR cells. Saracatinib, an src kinase inhibitor, suppressed ERK1/2 phosphorylation and growth of LC-2/ad DR cells. Taken together, these findings suggest that dovitinib can be a potential therapeutic option for RET-rearranged LADC, in which acquired resistance to dovitinib can be overcome by targeting Src.