Context-dependent roles of mutant B-Raf signaling in melanoma and colorectal carcinoma cell growth

Abstract

Mutational activation of Ras and a key downstream effector of Ras, the B-Raf serine/threonine kinase, has been observed in melanomas and colorectal carcinomas. These observations suggest that inhibition of B-Raf activation of mitogen-activated protein kinase (MAPK)/ extracellular signal-regulated kinase kinase (MEK) and the extracellular signal-regulated kinase MAPK cascade may be an effective approach for the treatment of RAS and B-RAF mutation-positive melanomas and colon carcinomas. Although recent studies with interfering RNA (RNAi) and pharmacologic inhibitors support a critical role for B-Raf signaling in melanoma growth, whether mutant B-Raf has an equivalent role in promoting colorectal carcinoma growth has not been determined. In the present study, we used both RNAi and pharmacologic approaches to further assess the role of B-Raf activation in the growth of human melanomas and additionally determined if a similar role for mutant B-Raf is seen for colorectal carcinoma cell lines. We observed that RNAi suppression of mutant B-Raf (V600E) expression strongly suppressed the anchoragedependent growth of B-RAF mutation-positive melanoma, but not colorectal carcinoma, cells. However, the anchorageindependent and tumorigenic growth of B-RAF mutationpositive colorectal carcinomas was dependent on mutant B-Raf function. Finally, pharmacologic inhibition of MEK and Raf was highly effective at inhibiting the growth of B-RAF mutation-positive melanomas and colorectal carcinoma cells, whereas inhibitors of other protein kinases activated by Ras (AKT, c-Jun NH 2 -terminal kinase, and p38 MAPK) were less effective. Our observations suggest that Raf and MEK inhibitors may be effective for the treatment of B-RAF mutation-positive colorectal carcinomas as well as melanomas. [Mol Cancer Ther 2007;6(8):2220 -9]

Design, synthesis, in-vitro antiproliferative activity and kinase profile of new picolinamide based 2-amido and ureido quinoline derivatives

“…In consistence with the aforementioned biochemical assay results, compound 9d exerted high potencies over the cell lines overexpressing mutant BRAF V600E like COLO 205 and HT29 colon cancer cell lines [40], and MALME-3M [40], SK-MEL-28 [41], SK-MEL-5 [41], and UACC-62 [42] melanoma cell lines. C-RAF is commonly over-expressed in the absence of oncogenic mutations in 50% of RCC (50%) [43], and is associated with poor prognosis in ovarian cancer [44].…”

Role of EIF5A2, a downstream target of Akt, in promoting melanoma cell invasion

“…We also transfected melanoma MMRU, A375, MMLH, SK-mel-3, SK-mel-28, SK-mel-31 and SK-mel-93 cells with EIF5A2 overexpression vector and found that cell invasion in these cell lines increased significantly compared with the vector control (Figure 4B and Supplementary Figures S5B–F and S6B, respectively). Out of these cell lines, MMRU (unpublished sequencing data from our lab), A375 (Chen et al , 2012a), SK-mel-28 and SK-mel-3 (Hao et al , 2007) carry BRAFV600E mutation and SK-mel-31 (Chow et al , 2012) carries NRASQ61K mutation. As MMP-2 was shown to have a crucial role in cell invasion (Vaisanen et al , 1996; Li et al , 2008), we then carried out the zymography assay to compare the activity of MMP-2 in EIF5A2-KD- or EIF5A2-overexpressing MMRU cells compared with respective controls.…”

Sorafenib Inhibits Non–Small Cell Lung Cancer Cell Growth by Targeting B-RAF in KRAS Wild-Type Cells and C-RAF in KRAS Mutant Cells

“…However, as far as we are aware, no previous study has compared sorafenib sensitivity among a panel of tumor cell lines of different KRAS mutational status. We have now evaluated the effects of sorafenib on the growth of NSCLC cells harboring wild-type or mutant forms of KRAS with two different assay systems, the MTT assay and anchorage-independent colony formation assay, given that previous studies have revealed differences in the sensitivity of cells to tested drugs between these two assay systems (29). The IC 50 values for inhibition of cell growth by sorafenib in these assays have generally been found to be well below 15 Amol/L, the maximum achievable plasma concentration of this drug (17).…”