RESUMO
ERBB2, a receptor tyrosine kinase amplified in breast cancer, is a well established regulator of tumor growth in vivo and anoikis resistance leading to disruption of architecture in three-dimensional mammary epithelial acinar structures in vitro. ERBB2 promotes anoikis resistance by maintaining signaling pathways and by rescuing metabolic defects and thus inhibiting accumulation of deleterious reactive oxygen species. Recent evidence suggests that hypoxia, via hypoxia-inducible factors (HIFs), can inhibit anoikis; thus, we hypothesized that HIF-1 may play a role in ERBB2-mediated anoikis resistance and oncogenesis. Indeed, tumors isolated from MMTV-Neu mice contain elevated HIF-1α levels and tumor cells created from MMTV-Neu mice harboring deletion of Hif1α alleles reduced primary tumor growth in vivo. ERBB2 overexpressing cancer cells stabilize HIF under normoxic conditions and require HIF-1 for ERBB2-mediated anchorage-independence, three-dimensional culture growth and anoikis resistance. HIF-1 reduction in ERBB2 cells was associated with induction of the pro-anoikis protein BIM and decreased ERK and AKT signaling during cell detachment. ERBB2-mediated inhibition of metabolic defects, including decreased reactive oxygen species generation in suspension, required HIF-1 expression that was critical for ERBB2-mediated oncogenesis. Gene expression profiling of hypoxic three-dimensional acinar structures identified a number of genes elevated in response to hypoxia that are known ERBB2 targets, suggesting that hypoxic conditions and ERBB2 overexpression share both phenotypic and genetic components via HIF-1 regulation. Thus, our data demonstrate that ERBB2 requires HIF-1 for tumor growth and suggest that HIF is a major downstream regulator of ERBB2 that protects cells from anoikis and metabolic stress caused by decreased matrix adhesion.
Assuntos
Anoikis , Regulação Neoplásica da Expressão Gênica , Subunidade alfa do Fator 1 Induzível por Hipóxia/metabolismo , Sistema de Sinalização das MAP Quinases , Neoplasias Mamárias Animais/metabolismo , Receptor ErbB-2/biossíntese , Animais , Adesão Celular/genética , Feminino , Deleção de Genes , Subunidade alfa do Fator 1 Induzível por Hipóxia/genética , Neoplasias Mamárias Animais/genética , Neoplasias Mamárias Animais/patologia , Camundongos , Camundongos Knockout , Proteínas Proto-Oncogênicas c-akt/genética , Proteínas Proto-Oncogênicas c-akt/metabolismo , Receptor ErbB-2/genética , Estresse Fisiológico/genéticaRESUMO
ERBB2/HER2 belongs to the EGFR-family of receptor tyrosine kinases and its overexpression can promote tumor progression. Breast cancer patients with ERBB2 amplifications are currently treated with lapatinib, a small-molecule kinase inhibitor that specifically blocks EGFR/ERBB2 signaling. Here, we show that hypoxia, via HIF-1, induces resistance to lapatinib-mediated effects in ERBB2-expressing mammary epithelial and ERBB2-positive breast cancer cells. Lapatinib-mediated growth inhibition and apoptosis in three-dimensional (3D) cultures are decreased under hypoxic conditions. Hypoxia can maintain activation of signaling pathways downstream from ERBB2 including AKT and ERK in the presence of lapatinib. HIF-1 is both required and sufficient to induce lapatinib resistance as overexpression of stable HIF-1 in ERBB2-expressing cells blocks lapatinib-mediated effects and maintains ERBB2-downstream signaling under normoxic conditions. Under hypoxia, activation of ERK signaling is required for lapatinib resistance as treatment with MEK inhibitor trametinib reverses hypoxia-mediated lapatinib resistance. HIF-1 can bypass the lapatinib-treated inhibition of the ERK pathway via inhibition of the dual-specificity phosphatase 2 (DUSP2). Indeed, overexpression of DUSP2 in ErbB2-positve breast cancer cells reverses hypoxia-mediated lapatinib resistance. Thus, our results provide rationale for therapeutic evaluation of the treatment of hypoxic ERBB2 expressing breast tumors with a combination of lapatinib and MEK inhibitors.
Assuntos
Fosfatase 2 de Especificidade Dupla/metabolismo , Subunidade alfa do Fator 1 Induzível por Hipóxia/metabolismo , Quinazolinas/farmacologia , Receptor ErbB-2/metabolismo , Apoptose/efeitos dos fármacos , Apoptose/genética , Neoplasias da Mama/genética , Neoplasias da Mama/metabolismo , Neoplasias da Mama/patologia , Hipóxia Celular , Linhagem Celular , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Proliferação de Células/genética , Resistencia a Medicamentos Antineoplásicos/efeitos dos fármacos , Resistencia a Medicamentos Antineoplásicos/genética , Fosfatase 2 de Especificidade Dupla/genética , MAP Quinases Reguladas por Sinal Extracelular/metabolismo , Feminino , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Humanos , Subunidade alfa do Fator 1 Induzível por Hipóxia/genética , Immunoblotting , Estimativa de Kaplan-Meier , Lapatinib , Prognóstico , Inibidores de Proteínas Quinases/farmacologia , Proteínas Proto-Oncogênicas c-akt/metabolismo , Piridonas/farmacologia , Pirimidinonas/farmacologia , Interferência de RNA , Receptor ErbB-2/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/genéticaRESUMO
Hypoxic tumors are associated with poor clinical outcome for multiple types of human cancer. This may be due, in part, to hypoxic cancer cells being resistant to anticancer therapy, including radiation therapy, chemotherapy, and targeted therapy. Hypoxia inducible factor 1, a major regulator of cellular response to hypoxia, regulates the expression of genes that are involved in multiple aspects of cancer biology, including cell survival, proliferation, metabolism, invasion, and angiogenesis. Here, we review multiple pathways regulated by hypoxia/hypoxia inducible factor 1 in cancer cells and discuss the latest advancements in overcoming hypoxia-mediated tumor resistance.