Dataset Information

BRAFV600E cooperates with PI3K signaling, independent of AKT, to regulate melanoma cell proliferation.

ABSTRACT: Mutationally activated BRAF(V600E) cooperates with PTEN silencing in the conversion of normal melanocytes to metastatic melanoma cells, but the mechanism underlying this cooperation is poorly understood. Here, the consequences of pharmacologic blockade of BRAF(V600E) or phosphoinositide 3-kinase (PI3K) signaling were explored using pathway-targeted inhibitors and a panel of human BRAF-mutated melanoma-derived cell lines. Blockade of BRAF(V600E) ? MEK1/2 ? ERK1/2 or class I PI3K inhibited melanoma proliferation, whereas inhibition of AKT had only modest effects, even in cells with mutated or amplified AKT. Although single-agent inhibition of either BRAF(V600E) or PI3K signaling elicited antiproliferative effects, combinatorial inhibition was more potent. Analysis of signaling downstream of BRAF(V600E) or PI3K revealed that these pathways cooperated to regulate protein synthesis through AKT-independent, mTOR complex 1 (mTORC1)-dependent effects on p70(S6K), ribosomal protein S6, and 4E-BP1 phosphorylation. Moreover, inhibition of mTORC1/2 inhibited cell proliferation as profoundly as single-agent inhibition of either BRAF(V600E) or PI3K signaling. These data reveal a mechanism by which BRAF(V600E) and PI3K signaling cooperate to regulate melanoma proliferation through AKT-independent effects on protein translation. Furthermore, this study provides a potential foundation for pathway-targeted combination therapy designed to enhance the therapeutic benefit to patients with melanoma that contain combined alterations in BRAF and PI3K signaling.PI3K, but not AKT, represent potential targets for melanoma therapy.

SUBMITTER: Silva JM

PROVIDER: S-EPMC3966216 | biostudies-literature | 2014 Mar

REPOSITORIES: biostudies-literature

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BRAFV600E cooperates with PI3K signaling, independent of AKT, to regulate melanoma cell proliferation.

Silva Jillian M JM Bulman Christina C McMahon Martin M

Molecular cancer research : MCR 20140114 3

<h4>Unlabelled</h4>Mutationally activated BRAF(V600E) cooperates with PTEN silencing in the conversion of normal melanocytes to metastatic melanoma cells, but the mechanism underlying this cooperation is poorly understood. Here, the consequences of pharmacologic blockade of BRAF(V600E) or phosphoinositide 3-kinase (PI3K) signaling were explored using pathway-targeted inhibitors and a panel of human BRAF-mutated melanoma-derived cell lines. Blockade of BRAF(V600E) → MEK1/2 → ERK1/2 or class I PI3 ...[more]

PMID: 24425783

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Project description:Proliferation is one of the significant hallmarks of gallbladder cancer, which is a relatively rare but fatal malignance. Aim of this study was to examine the biological impact and molecular mechanism of the candidate hub-gene on the proliferation and tumorigenesis of gallbladder cancer. We analyzed the differentially expressed genes and the correlation between these genes with MKI67, and showed that KIF11 is one of the major upregulated regulators of proliferation in gallbladder cancer (GBC). The Gene Ontology, Gene Sets Enrichment Analysis and KEGG Pathway analysis indicated that KIF11 may promote GBC cell proliferation through the ERBB2/PI3K/AKT signaling pathway. Gain-of-function and loss-of-function assay demonstrated that KIF11 regulated GBC cell cycle and cancer cell proliferation in vitro. GBC cells exhibited G2M phase cell cycle arrest, cell proliferation and clone formation ability reduction after treatment with Monastrol, a specific inhibitor of KIF11. Xenograft model showed that KIF11 promotes GBC growth in vivo. Rescue experiments showed that KIF11-induced GBC cell proliferation dependented on ERBB2/PI3K/AKT pathway. Moreover, we found that H3K27ac signals are enriched among the promoter region of KIF11 in the UCSC Genome Browser Database. Differentially expressed analysis showed that EP300, a major histone acetyltransferase modifying H3K27ac signal, is highly expressed in gallbladder cancer and correlation analysis illustrated that EP300 is positively related with KIF11 in almost all the cancer types. We further found that KIF11 was significantly downregulated in a dose-dependent and time-dependent manner after histone acetylation inhibitor treatment. The present results highlight that high KIF11 expression promotes GBC cell proliferation through the ERBB2/PI3K/AKT signaling pathway. The findings may help deepen our understanding of mechanism underlying GBC cancer development and development of novel diagnostic and therapeutic target.

Project description:Glioblastoma is a high-grade glioma with poor prognosis even after surgery and standard therapy. Here, we asked whether carnosine (β-alanyl-L-histidine), a naturally occurring dipeptide, exert its anti-neoplastic effect on glioblastoma cells via PI3K/Akt/mTOR signaling. Therefore, glioblastoma cells from the lines U87 and T98G were exposed to carnosine, to the mTOR inhibitor rapamycin and to the PI3K inhibitor Ly-294,002. Pyruvate dehydrogenase kinase (PDK4) expression, known to be a target of PI3K/Akt/mTOR, and which is also affected by carnosine, was analyzed by RT-qPCR, and reporter gene assays with the human PDK4 promoter were performed. Cell viability was assessed by cell-based assays and mTOR and Akt phosphorylation by Western blotting. Rapamycin and Ly-294,002 increased PDK4 mRNA expression in both cell lines but significance was only reached in U87. Carnosine significantly increased expression in both lines. A significant combinatorial effect of carnosine was only detected in U87 when the dipeptide was combined with Ly-294,002. Reporter gene assays revealed no specific effect of carnosine on the human PDK4 promoter, whereas both inhibitors increased reporter gene expression. Rapamycin reduced phosphorylation of mTOR, and Ly-294,002 that of Akt. A significant reduction of Akt phosphorylation was observed in the presence of carnosine in U87 but not in T98G, and carnosine had no effect on mTOR phosphorylation. Cell viability as determined by ATP in cell lysates was reduced only in the presence of carnosine. We conclude that carnosine's anti-neoplastic effect is independent from PI3K/Akt/mTOR signaling. As the dipeptide reduced viability in tumor cells that do not respond to PI3K or mTOR inhibitors, it appears to be worth to further investigate the mechanisms by which carnosine exerts its anti-tumor effect and to consider it for therapy, especially as it is a naturally occurring compound that has already been used for the treatment of other diseases without indication of side-effects.

Dataset Information

BRAFV600E cooperates with PI3K signaling, independent of AKT, to regulate melanoma cell proliferation.

Publications

BRAFV600E cooperates with PI3K signaling, independent of AKT, to regulate melanoma cell proliferation.

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