RESUMO
Cancer chemotherapy resistance (MDR) is the innate and/or acquired ability of cancer cells to evade the effects of chemotherapeutics and is one of the most pressing major dilemmas in cancer therapy. Chemotherapy resistance can arise due to several host or tumor-related factors. However, most current research is focused on tumor-specific factors and specifically genes that handle expression of pumps that efflux accumulated drugs inside malignantly transformed types of cells. In this work, we suggest a wider and alternative perspective that sets the stage for a future platform in modifying drug resistance with respect to the treatment of cancer.
RESUMO
We and others have shown central roles of the Na(+)/H(+) exchanger NHE1 in cell motility. The aim of this study was to determine the roles of NHE1 and of the Na(+), HCO(3)(-) cotransporter NBCn1 in motility of serum-starved MCF-7 breast cancer cells expressing constitutively active ErbB2 (ΔNErbB2). ΔNErbB2 expression elicited NBCn1 upregulation, Ser(703)-phosphorylation of NHE1, and NHE1-inhibitor (EIPA)-sensitive pericellular acidification, in conjunction with increased expression of ß1 integrin and ERM proteins. Active ERM proteins and NHE1 colocalized strongly to invadopodial rosettes, the diameter of which was increased by ΔNErbB2. Adhesion and migration on collagen-I were augmented by ΔNErbB2, unaffected by the NBC inhibitor S0859, and further stimulated by EIPA in a manner potentiated by PI3K-Akt-inhibition. These findings demonstrate that NHE1 inhibition can enhance cancer cell motility, adding an important facet to the understanding of NHE1 in cancer.
Assuntos
Proteínas de Transporte de Cátions/metabolismo , Movimento Celular/fisiologia , Receptor ErbB-2/metabolismo , Simportadores de Sódio-Bicarbonato/metabolismo , Trocadores de Sódio-Hidrogênio/metabolismo , Amilorida/análogos & derivados , Amilorida/farmacologia , Benzamidas/farmacologia , Neoplasias da Mama/genética , Neoplasias da Mama/metabolismo , Neoplasias da Mama/patologia , Proteínas de Transporte de Cátions/genética , Adesão Celular/efeitos dos fármacos , Adesão Celular/genética , Adesão Celular/fisiologia , Linhagem Celular Tumoral , Movimento Celular/efeitos dos fármacos , Movimento Celular/genética , Cromonas/farmacologia , Meios de Cultura Livres de Soro/farmacologia , Proteínas do Citoesqueleto/metabolismo , Inibidores Enzimáticos/farmacologia , Feminino , Humanos , Concentração de Íons de Hidrogênio , Immunoblotting , Integrina beta1/metabolismo , Proteínas de Membrana/metabolismo , Proteínas dos Microfilamentos/metabolismo , Morfolinas/farmacologia , Fosfatidilinositol 3-Quinases/metabolismo , Fosforilação , Proteínas Proto-Oncogênicas c-akt/antagonistas & inibidores , Proteínas Proto-Oncogênicas c-akt/metabolismo , Receptor ErbB-2/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Transdução de Sinais/efeitos dos fármacos , Simportadores de Sódio-Bicarbonato/antagonistas & inibidores , Simportadores de Sódio-Bicarbonato/genética , Trocador 1 de Sódio-Hidrogênio , Trocadores de Sódio-Hidrogênio/genética , Sulfonamidas/farmacologiaRESUMO
We previously demonstrated that the primary cilium coordinates platelet-derived growth factor (PDGF) receptor (PDGFR) alpha-mediated migration in growth-arrested fibroblasts. In this study, we investigate the functional relationship between ciliary PDGFR-alpha and the Na(+)/H(+) exchanger NHE1 in directional cell migration. NHE1 messenger RNA and protein levels are up-regulated in NIH3T3 cells and mouse embryonic fibroblasts (MEFs) during growth arrest, which is concomitant with cilium formation. NHE1 up-regulation is unaffected in Tg737(orpk) MEFs, which have no or very short primary cilia. In growth-arrested NIH3T3 cells, NHE1 is activated by the specific PDGFR-alpha ligand PDGF-AA. In wound-healing assays on growth-arrested NIH3T3 cells and wild-type MEFs, NHE1 inhibition by 5'-(N-ethyl-N-isopropyl) amiloride potently reduces PDGF-AA-mediated directional migration. These effects are strongly attenuated in interphase NIH3T3 cells, which are devoid of primary cilia, and in Tg737(orpk) MEFs. PDGF-AA failed to stimulate migration in NHE1-null fibroblasts. In conclusion, stimulation of directional migration in response to ciliary PDGFR-alpha signals is specifically dependent on NHE1 activity, indicating that NHE1 activation is a critical event in the physiological response to PDGFR-alpha stimulation.
