RESUMEN
Inhibitor of DNA binding 4 (ID4) is a helix-loop-helix protein that heterodimerizes with basic helix-loop-helix transcription factors inhibiting their function. ID4 expression is important for adipogenic differentiation of the 3T3-L1 cell line, and inhibition of ID4 is associated with a concomitant decrease in CCAAT/enhancer-binding protein alpha and peroxisome proliferator-activated receptor gamma mRNA and protein expression. Mice with a homozygous deletion of Id4 (Id4(-/-)) have reduced body fat and gain much less weight compared with wild-type littermates when placed on diets with high fat content. Mouse embryonic fibroblasts (MEFs) isolated from Id4(-/-) mice have reduced adipogenic potential when compared with wild-type MEFs. In agreement with changes in morphological differentiation, the levels of CCAAT/enhancer-binding protein alpha and peroxisome proliferator-activated receptor gamma were also reduced in MEFs from Id4(-/-) mice. Our results demonstrate the importance of ID4 in adipocyte differentiation and the implications of this regulation for adipose tissue formation.
Asunto(s)
Adipocitos/citología , Tejido Adiposo/metabolismo , Proteínas Inhibidoras de la Diferenciación/fisiología , Células 3T3-L1 , Animales , Peso Corporal , Diferenciación Celular , Dimerización , Fibroblastos/metabolismo , Eliminación de Gen , Genotipo , Homocigoto , Proteínas Inhibidoras de la Diferenciación/metabolismo , Ratones , Ratones Endogámicos C57BL , Modelos BiológicosRESUMEN
Most patients with BRAF(V600)-mutant metastatic melanoma develop resistance to selective RAF kinase inhibitors. The spectrum of clinical genetic resistance mechanisms to RAF inhibitors and options for salvage therapy are incompletely understood. We performed whole-exome sequencing on formalin-fixed, paraffin-embedded tumors from 45 patients with BRAF(V600)-mutant metastatic melanoma who received vemurafenib or dabrafenib monotherapy. Genetic alterations in known or putative RAF inhibitor resistance genes were observed in 23 of 45 patients (51%). Besides previously characterized alterations, we discovered a "long tail" of new mitogen-activated protein kinase (MAPK) pathway alterations (MAP2K2, MITF) that confer RAF inhibitor resistance. In three cases, multiple resistance gene alterations were observed within the same tumor biopsy. Overall, RAF inhibitor therapy leads to diverse clinical genetic resistance mechanisms, mostly involving MAPK pathway reactivation. Novel therapeutic combinations may be needed to achieve durable clinical control of BRAF(V600)-mutant melanoma. Integrating clinical genomics with preclinical screens may model subsequent resistance studies.