Dataset Information

KSR1 and EPHB4 Regulate Myc and PGC1? To Promote Survival of Human Colon Tumors.

ABSTRACT: Identification and characterization of survival pathways active in tumor cells but absent in normal tissues provide opportunities to develop effective anticancer therapies with reduced toxicity to the patient. We show here that, like kinase suppressor of Ras 1 (KSR1), EPH (erythropoietin-producing hepatocellular carcinoma) receptor B4 (EPHB4) is aberrantly overexpressed in human colon tumor cell lines and selectively required for their survival. KSR1 and EPHB4 support tumor cell survival by promoting the expression of downstream targets, Myc and the transcriptional coactivator peroxisome proliferator-activated receptor gamma coactivator 1? (PGC1?). While KSR1 promotes the aberrant expression of Myc and the PGC1? protein via a posttranscriptional mechanism, EPHB4 has a greater effect on Myc and PGC1? expression via its ability to elevate mRNA levels. Subsequent analysis of the posttranscriptional regulation demonstrated that KSR1 promotes the translation of Myc protein. These findings reveal novel KSR1- and EPHB4-dependent signaling pathways supporting the survival of colorectal cancer cells through regulation of Myc and PGC1?, suggesting that inhibition of KSR1 or EPHB4 effectors may lead to selective toxicity in colorectal tumors.

SUBMITTER: McCall JL

PROVIDER: S-EPMC4985931 | biostudies-literature | 2016 Sep

REPOSITORIES: biostudies-literature

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KSR1 and EPHB4 Regulate Myc and PGC1β To Promote Survival of Human Colon Tumors.

McCall Jamie L JL Gehring Drew D Clymer Beth K BK Fisher Kurt W KW Das Binita B Kelly David L DL Kim Hyunseok H White Michael A MA Lewis Robert E RE

Molecular and cellular biology 20160812 17

Identification and characterization of survival pathways active in tumor cells but absent in normal tissues provide opportunities to develop effective anticancer therapies with reduced toxicity to the patient. We show here that, like kinase suppressor of Ras 1 (KSR1), EPH (erythropoietin-producing hepatocellular carcinoma) receptor B4 (EPHB4) is aberrantly overexpressed in human colon tumor cell lines and selectively required for their survival. KSR1 and EPHB4 support tumor cell survival by prom ...[more]

PMID: 27273865

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Project description:The precise characteristics that distinguish normal and oncogenic RAS signaling remain obscure. Here, we show that oncogenic RAS and BRAF induce perinuclear relocalization of several RAS pathway proteins, including the kinases CK2 and p-ERK1/2 and the signaling scaffold KSR1. This spatial reorganization requires endocytosis, the kinase activities of MEK-ERK and CK2, and the presence of KSR1. CK2? colocalizes with KSR1 and Rab11, a marker of recycling endosomes, whereas p-ERK associates predominantly with a distinct KSR1-positive endosomal population. Notably, these perinuclear signaling complexes (PSC) are present in tumor cell lines, mouse lung tumors, and mouse embryonic fibroblasts undergoing RAS-induced senescence. PSCs are also transiently induced by growth factors (GF) in nontransformed cells with delayed kinetics (4-6 hours), establishing a novel late phase of GF signaling that appears to be constitutively activated in tumor cells. PSCs provide an essential platform for RAS-induced phosphorylation and activation of the prosenescence transcription factor C/EBP? in primary MEFs undergoing senescence. Conversely, in tumor cells, C/EBP? activation is suppressed by 3'UTR-mediated localization of Cebpb transcripts to a peripheral cytoplasmic domain distinct from the PSC region. Collectively, our findings indicate that sustained PSC formation is a critical feature of oncogenic RAS/BRAF signaling in cancer cells that controls signal transmission to downstream targets by regulating selective access of effector kinases to substrates such as C/EBP?.Significance: In addressing the long-standing question of the difference between normal and oncogenic RAS pathway signaling, this study shows that oncogenic RAS specifically triggers constitutive endocytosis-dependent movement of effector kinases to a perinuclear region, thereby creating connections to unique downstream targets such as the core prosenescence and the inflammatory regulatory transcription factor C/EBP?. Cancer Res; 78(4); 891-908. ©2017 AACR.

Dataset Information

KSR1 and EPHB4 Regulate Myc and PGC1? To Promote Survival of Human Colon Tumors.

Publications

KSR1 and EPHB4 Regulate Myc and PGC1β To Promote Survival of Human Colon Tumors.

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