Classic Ras Proteins Promote Proliferation and Survival via Distinct Phosphoproteome Alterations in Neurofibromin-Null Malignant Peripheral Nerve Sheath Tumor Cells

Abstract

Neurofibromin, the tumor suppressor encoded by the neurofibromatosis type 1 (NF1) gene, potentially suppresses the activation of H-Ras, N-Ras and K-Ras. However, it is not known whether these classic Ras proteins are hyperactivated in NF1-null nerve sheath tumors, how they contribute to tumorigenesis and what signaling pathways mediate their effects. Here we show that H-Ras, N-Ras and K-Ras are coexpressed with their activators, (guanine nucleotide exchange factors), in neurofibromin-null malignant peripheral nerve sheath tumor (MPNST) cells and that all 3 Ras proteins are activated. Dominant negative (DN) H-Ras, a pan-inhibitor of the classic Ras family, inhibited MPNST proliferation and survival, but not migration. However, NF1-null MPNST cells were variably dependent on individual Ras proteins. In some lines, ablation of H-Ras, N-Ras and/or K-Ras inhibited mitogenesis. In others, ablation of a single Ras protein had no effect on proliferation; in these lines, ablation of a single Ras protein resulted in compensatory increases in the activation and/or expression of other Ras proteins. Using mass spectrometry-based phosphoproteomics, we identified 7 signaling networks affecting morphology, proliferation and survival that are regulated by DN H-Ras. Thus, neurofibromin loss activates multiple classic Ras proteins that promote proliferation and survival by regulating several distinct signaling cascades.

MicroRNA silencing of CNN1 and CNN2 protein family members regulates biology processes in colorectal cancer by targeting the p53 signal pathway

“…Cyclin D1, a cell cycle promoter, was downregulated by silencing CNN1 and CNN2, explaining that why cell cycle was arrested [27,28]. the K-ras and p53 signal pathways play important roles in colorectal cancer cell lines, as reported in many solid cancers [29][30][31][32][33][34]. We found that the p53 signal pathway was suppressed by upregulating CNN2 or silencing CNN1, which interacted with cyclin D1, arresting the cell cycle.…”

The Challenge of Cancer Genomics in Rare Nervous System Neoplasms

“…However, only classic Ras proteins promote the survival of MPNST cells, whereas R-Ras proteins drive their migration. 29 Within the classic Ras subfamily, though, there appears to be functional redundancy; ablation of one subfamily member results in increased expression and activation of another subfamily member with little, if any, effect on proliferation. Tipifarnib inhibits only H-Ras, because other post-translational modifications such as geranylgeranylation allow K-Ras and N-Ras to be Figure 1 In plexiform neurofibromas and MPNSTs, neurofibromin loss deregulates multiple proteins from both the classic Ras and R-Ras subfamilies.…”

“…Although initial results indicate that this is the case, note that the full repertoire of Ras-dependent signaling pathways activated in NF1-null peripheral nerve sheath tumors has not yet been defined. Indeed, a recent study that examined changes occurring in the phosphoproteome after inhibition of classic Ras signaling 29 showed that classic Ras signaling controlled multiple additional signaling cascades in MPNSTs. It will be important to determine which of these signaling cascades contribute to tumorigenesis and whether they are further dysregulated by additional mutations arising during neurofibroma-MPNST progression.…”

miR-98 functions as a tumor suppressor in salivary adenoid cystic carcinomas

“…The RAS oncogene family is extraordinarily common in diverse cancers, and members of the family play important roles in tumorigenesis. 27 RAS promotes tumorigenesis by activating several intracellular signal transduction cascades, including the RAS/MAPK/ERK and PI3K/AKT pathways. 28 , 29 In gliomas, miR-143 inhibits N-RAS expression by these two pathways.…”