RESUMO
Therapies targeting the tyrosine kinase activity of Epidermal Growth Factor Receptor (EGFR) have been proven to be effective in treating a subset of non-small cell lung cancer (NSCLC) patients harboring activating EGFR mutations. Inevitably these patients develop resistance to the EGFR-targeted tyrosine kinase inhibitors (TKIs). Here, we performed integrated genomic analyses using an in vitro system to uncover alternative genomic mechanisms responsible for acquired resistance to EGFR-TKIs. Specifically, we identified 80 genes whose expression is significantly increased in the erlotinib-resistant clones. RNAi-based systematic synthetic lethal screening of these candidate genes revealed that suppression of one upregulated transcript, SCRN1, a secernin family member, restores sensitivity to erlotinib by enhancing inhibition of PI3K/AKT signaling pathway. Furthermore, immunohistochemical analysis revealed increased levels of SCRN1 in 5 of 11 lung tumor specimens from EGFR-TKIs resistant patients. Taken together, we propose that upregulation of SCRN1 is an additional mechanism associated with acquired resistance to EGFR-TKIs and that its suppression serves as a novel therapeutic strategy to overcome drug resistance in these patients.
Assuntos
Carcinoma Pulmonar de Células não Pequenas/genética , Resistencia a Medicamentos Antineoplásicos/genética , Receptores ErbB/genética , Cloridrato de Erlotinib/farmacologia , Genômica/métodos , Neoplasias Pulmonares/genética , Mutação , Proteínas do Tecido Nervoso/genética , Animais , Apoptose , Biomarcadores Tumorais/genética , Carcinogênese , Carcinoma Pulmonar de Células não Pequenas/tratamento farmacológico , Carcinoma Pulmonar de Células não Pequenas/patologia , Proliferação de Células , Receptores ErbB/antagonistas & inibidores , Humanos , Neoplasias Pulmonares/tratamento farmacológico , Neoplasias Pulmonares/patologia , Masculino , Camundongos , Camundongos Nus , Inibidores de Proteínas Quinases/farmacologia , RNA Interferente Pequeno/genética , Transdução de Sinais , Células Tumorais Cultivadas , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
Mig6 is a feedback inhibitor that directly binds, inhibits and drives internalization of ErbB-family receptors. Mig6 selectively targets activated receptors. Here we found that the epidermal growth factor receptor (EGFR) phosphorylates Mig6 on Y394 and that this phosphorylation is primed by prior phosphorylation of an adjacent residue, Y395, by Src. Crystal structures of human EGFR-Mig6 complexes reveal the structural basis for enhanced phosphorylation of primed Mig6 and show how Mig6 rearranges after phosphorylation by EGFR to effectively irreversibly inhibit the same receptor that catalyzed its phosphorylation. This dual phosphorylation site allows Mig6 to inactivate EGFR in a manner that requires activation of the target receptor and that can be modulated by Src. Loss of Mig6 is a driving event in human cancer; analysis of 1,057 gliomas reveals frequent focal deletions of ERRFI1, the gene that encodes Mig6, in EGFR-amplified glioblastomas.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/química , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Receptores ErbB/antagonistas & inibidores , Receptores ErbB/química , Processamento de Proteína Pós-Traducional , Proteínas Supressoras de Tumor/química , Proteínas Supressoras de Tumor/metabolismo , Proteínas Adaptadoras de Transdução de Sinal/genética , Cristalografia por Raios X , Deleção de Genes , Glioma/patologia , Humanos , Modelos Moleculares , Fosforilação , Ligação Proteica , Conformação Proteica , Proteínas Supressoras de Tumor/genética , Quinases da Família src/metabolismoRESUMO
BACKGROUND: Inhibition of the activated epidermal growth factor receptor (EGFR) with either enzymatic kinase inhibitors or anti-EGFR antibodies such as cetuximab, is an effective modality of treatment for multiple human cancers. Enzymatic EGFR inhibitors are effective for lung adenocarcinomas with somatic kinase domain EGFR mutations while, paradoxically, anti-EGFR antibodies are more effective in colon and head and neck cancers where EGFR mutations occur less frequently. In colorectal cancer, anti-EGFR antibodies are routinely used as second-line therapy of KRAS wild-type tumors. However, detailed mechanisms and genomic predictors for pharmacological response to these antibodies in colon cancer remain unclear. FINDINGS: We describe a case of colorectal adenocarcinoma, which was found to harbor a kinase domain mutation, G724S, in EGFR through whole genome sequencing. We show that G724S mutant EGFR is oncogenic and that it differs from classic lung cancer derived EGFR mutants in that it is cetuximab responsive in vitro, yet relatively insensitive to small molecule kinase inhibitors. Through biochemical and cellular pharmacologic studies, we have determined that cells harboring the colon cancer-derived G719S and G724S mutants are responsive to cetuximab therapy in vitro and found that the requirement for asymmetric dimerization of these mutant EGFR to promote cellular transformation may explain their greater inhibition by cetuximab than small-molecule kinase inhibitors. CONCLUSION: The colon-cancer derived G719S and G724S mutants are oncogenic and sensitive in vitro to cetuximab. These data suggest that patients with these mutations may benefit from the use of anti-EGFR antibodies as part of the first-line therapy.
