RESUMO
Lemur tyrosine kinase 3 (LMTK3) is an oncogenic kinase that is involved in different types of cancer (breast, lung, gastric, colorectal) and biological processes including proliferation, invasion, migration, chromatin remodeling as well as innate and acquired endocrine resistance. However, the role of LMTK3 in response to cytotoxic chemotherapy has not been investigated thus far. Using both 2D and 3D tissue culture models, we found that overexpression of LMTK3 decreased the sensitivity of breast cancer cell lines to cytotoxic (doxorubicin) treatment. In a mouse model we showed that ectopic overexpression of LMTK3 decreases the efficacy of doxorubicin in reducing tumor growth. Interestingly, breast cancer cells overexpressing LMTK3 delayed the generation of double strand breaks (DSBs) after exposure to doxorubicin, as measured by the formation of γH2AX foci. This effect was at least partly mediated by decreased activity of ataxia-telangiectasia mutated kinase (ATM) as indicated by its reduced phosphorylation levels. In addition, our RNA-seq analyses showed that doxorubicin differentially regulated the expression of over 700 genes depending on LMTK3 protein expression levels. Furthermore, these genes were found to promote DNA repair, cell viability and tumorigenesis processes / pathways in LMTK3-overexpressing MCF7 cells. In human cancers, immunohistochemistry staining of LMTK3 in pre- and post-chemotherapy breast tumor pairs from four separate clinical cohorts revealed a significant increase of LMTK3 following both doxorubicin and docetaxel based chemotherapy. In aggregate, our findings show for the first time a contribution of LMTK3 in cytotoxic drug resistance in breast cancer.
Assuntos
Neoplasias da Mama/tratamento farmacológico , Resistencia a Medicamentos Antineoplásicos/fisiologia , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Proteínas de Membrana/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Animais , Antineoplásicos/farmacologia , Proteínas Mutadas de Ataxia Telangiectasia/metabolismo , Neoplasias da Mama/patologia , Quebras de DNA de Cadeia Dupla/efeitos dos fármacos , Docetaxel/farmacologia , Doxorrubicina/farmacologia , Resistencia a Medicamentos Antineoplásicos/efeitos dos fármacos , Feminino , Histonas/metabolismo , Humanos , Proteínas de Membrana/genética , Camundongos Nus , Proteínas Serina-Treonina Quinases/genética , Células Tumorais Cultivadas , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
BACKGROUND: Estrogen Receptor α (ERα), a member of the nuclear receptor superfamily of transcription factors, plays a central role in breast cancer development. More than two-thirds of patients with breast cancer are ERα-positive; however, a proportion becomes resistant. Phosphorylation of ERα is one of the mechanisms associated with resistance to endocrine therapy. In a kinome screen, we have identified the large tumor suppressor homolog-2 (LATS2) as a potential kinase, acting on ERα. MATERIALS AND METHODS: The role of LATS2 on activation of ERα transcription and its functional consequences was examined by various molecular and cellular biology techniques. RESULTS: LATS2 co-localises with ERα in the nucleus. LATS2-silencing increases expression of ERα-regulated genes and inhibits proliferation. At the protein level, inhibition of LATS2 reduces the expression of cyclin-D1 and Nuclear Receptor Co-Repressor (NCoR) while increasing the expression of p27. CONCLUSION: Identifying novel kinases which modulate ERα activity is relevant to therapeutics. LATS2 modulates ERα-regulated gene transcription, through direct and/or indirect interactions with ERα.