Acquired resistance mechanisms to afatinib in HER2-amplified gastric cancer cells

Cancer treatment, especially that for breast and lung cancer, has entered a new era and continues to evolve, with the development of genome analysis technology and the advent of molecular targeted drugs including tyrosine kinase inhibitors. Nevertheless, acquired drug resistance to molecular targeted drugs is unavoidable, creating a clinically challenging problem. We recently reported the antitumor effect of a pan-HER inhibitor, afatinib, against human epidermal growth factor receptor 2 (HER2)-amplified gastric cancer cells. The purpose of the present study was to identify the mechanisms of acquired afatinib resistance and to investigate the treatment strategies for HER2-amplified gastric cancer cells. Two afatinib-resistant gastric cancer cell lines were established from 2 HER2-amplified cell lines, N87 and SNU216. Subsequently, we investigated the molecular profiles of resistant cells. The activation of the HER2 pathway was downregulated in N87-derived resistant cells, whereas it was upregulated in SNU216-derived resistant cells. In the N87-derived cell line, both MET and AXL were activated, and combination treatment with afatinib and cabozantinib, a multikinase inhibitor that inhibits MET and AXL, suppressed the cell growth of cells with acquired resistance both in vitro and in vivo. In the SNU216-derived cell line, YES1, which is a member of the Src family, was remarkably activated, and dasatinib, a Src inhibitor, exerted a strong antitumor effect in these cells. In conclusion, we identified MET and AXL activation in addition to YES1 activation as novel mechanisms of afatinib resistance in HER2-driven gastric cancer. Our results also indicated that treatment strategies targeting individual mechanisms of resistance are key to overcoming such resistance

YES1 activation induces acquired resistance to neratinib in HER2-amplified breast and lung cancers

Molecular-targeted therapies directed against human epidermal growth factor receptor 2 (HER2) are evolving for various cancers. Neratinib is an irreversible pan-HER tyrosine kinase inhibitor and has been approved by the FDA as an effective drug for HER2-positive breast cancer. However, acquired resistance of various cancers to molecular-targeted drugs is an issue of clinical concern, and emergence of resistance to neratinib is also considered inevitable. In this study, we established various types of neratinib-resistant cell lines from HER2-amplified breast and lung cancer cell lines using several drug exposure conditions. We analyzed the mechanisms of emergence of the resistance in these cell lines and explored effective strategies to overcome the resistance. Our results revealed that amplification of YES1, which is a member of the SRC family, was amplified in two neratinib-resistant breast cancer cell lines and one lung cancer cell line. Knockdown of YES1 by siRNA and pharmacological inhibition of YES1 by dasatinib restored the sensitivity of the YES1-amplified cell lines to neratinib in vitro. Combined treatment with dasatinib and neratinib inhibited tumor growth in vivo. This combination also induced downregulation of signaling molecules such as HER2, AKT and MAPK. Our current results indicate that YES1 plays an important role in the emergence of resistance to HER2-targeted drugs, and that dasatinib enables such acquired resistance to neratinib to be overcome

Drug repositioning of tranilast to sensitize a cancer therapy by targeting cancer-associated fibroblast

Cancer-associated fibroblasts (CAFs) are a major component of the tumor microenvironment that mediate resistance of cancer cells to anticancer drugs. Tranilast is an antiallergic drug that suppresses the release of cytokines from various inflammatory cells. In this study, we investigated the inhibitory effect of tranilast on the interactions between non-small cell lung cancer (NSCLC) cells and the CAFs in the tumor microenvironment. Three EGFR-mutant NSCLC cell lines, two KRAS-mutant cell lines, and three CAFs derived from NSCLC patients were used. To mimic the tumor microenvironment, the NSCLC cells were cocultured with the CAFs in vitro, and the molecular profiles and sensitivity to molecular targeted therapy were assessed. Crosstalk between NSCLC cells and CAFs induced multiple biological effects on the NSCLC cells both in vivo and in vitro, including activation of the STAT3 signaling pathway, promotion of xenograft tumor growth, induction of epithelial-mesenchymal transition (EMT), and acquisition of resistance to molecular-targeted therapy, including EGFR-mutant NSCLC cells to osimertinib and of KRAS-mutant NSCLC cells to selumetinib. Treatment with tranilast led to inhibition of IL-6 secretion from the CAFs, which, in turn, resulted in inhibition of CAF-induced phospho-STAT3 upregulation. Tranilast also inhibited CAF-induced EMT in the NSCLC cells. Finally, combined administration of tranilast with molecular-targeted therapy reversed the CAF-mediated resistance of the NSCLC cells to the molecular-targeted drugs, both in vitro and in vivo. Our results showed that combined administration of tranilast with molecular-targeted therapy is a possible new treatment strategy to overcome drug resistance caused by cancer-CAF interaction

Overcoming epithelial-mesenchymal transition-mediated drug resistance with monensin-based combined therapy in non-small cell lung cancer

Background The epithelial-mesenchymal transition (EMT) is a key process in tumor progression and metastasis and is also associated with drug resistance. Thus, controlling EMT status is a research of interest to conquer the malignant tumors. Materials and methods A drug repositioning analysis of transcriptomic data from a public cell line database identified monensin, a widely used in veterinary medicine, as a candidate EMT inhibitor that suppresses the conversion of the EMT phenotype. Using TGF-β-induced EMT cell line models, the effects of monensin on the EMT status and EMT-mediated drug resistance were assessed. Results TGF-β treatment induced EMT in non-small cell lung cancer (NSCLC) cell lines and the EGFR-mutant NSCLC cell lines with TGF-β-induced EMT acquired resistance to EGFR-tyrosine kinase inhibitor. The addition of monensin effectively suppressed the TGF-β-induced-EMT conversion, and restored the growth inhibition and the induction of apoptosis by the EGFR-tyrosine kinase inhibitor. Conclusion Our data suggested that combined therapy with monensin might be a useful strategy for preventing EMT-mediated acquired drug resistance

SNPs within the Intron-less TAF7 Gene Encoding a General Transcription Factor in Japanese Males

TAF7 は転写開始と伸長に必須な転写開始前複合体に含まれる｡精巣において､TAF7 は細胞の増殖を伴う精原細胞と第一精母細胞の核に局在し､また､TAF7 の精巣特異的ｱｲｿｻﾞｲﾑである TAF7L は､精子細胞分化過程で核に局在する｡このことから､雄性生殖細胞では､細胞増殖を伴う精原細胞では TAF7 が､その後の精子分化過程では TAF7L が転写調節に機能していることが考えられる｡今回私たちは､細胞増殖をともなう精原細胞で発現する TAF7 ｲﾝﾄﾛﾝﾚｽ遺伝子について､男性不妊症と TAF7 の遺伝子多型の関係を調べるため､282人の日本人男性不妊症患者と96人の妊孕性が確認された日本人男性ﾎﾞﾗﾝﾃｨｱの遺伝子多型を調べた｡その結果､男性不妊症性患者において､5\u27 非翻訳領域に CTC の3塩基欠失と､ｱﾐﾉ酸置換を伴う一塩基多型がそれぞれﾍﾃﾛ接合型として各々一人づつ検出された｡ The National Center for Biotechnology Information には TAF7 に関して多くの一塩基多型が登録されているが､日本人男性に関してそれらの遺伝子多型はほとんどが検出されなかった｡新たに同定されたこれらの遺伝子多型は､体質と遺伝子多型の大規模な解析に役立つものと考えられる｡TAF7 is a part of the protein complex that is indispensable for the start of transcription. In the testis, TAF7 localizes on nuclei in spermatogonia and primary spermatocytes during proliferation. To examine whether genetic polymorphisms of the intron-less TAF7 gene are associated with male infertility, we screened TAF7 for genetic polymorphisms using DNA from 282 sterile and 96 fertile male volunteers. We identified 11 genetic polymorphisms in the TAF7 region. Although many single nucleotide polymorphisms (SNPs) have been reported in the SNP database of the National Center for Biotechnology Information, we found a novel CTC deletion and one SNP with an amino acid substitution in the TAF7 genomic region in infertile patients. These genetic polymorphisms might be causes of male sterility. These results will be useful for analyzing the association of traits and genetic polymorphisms in further large-scale genetic analyses