In many cancers, high proliferation rates correlate with elevation of rRNA and tRNA levels, and nucleolar hypertrophy. However, the underlying mechanisms linking increased nucleolar transcription and tumorigenesis are only minimally understood. Here we show that IMP dehydrogenase-2 (IMPDH2), the rate-limiting enzyme for de novo guanine nucleotide biosynthesis, is overexpressed in the highly lethal brain cancer, glioblastoma (GBM). This leads to increased rRNA and tRNA synthesis, stabilization of the nucleolar GTP-binding protein, Nucleostemin, and enlarged, malformed nucleoli. Pharmacological or genetic inactivation of IMPDH2 in GBM reverses these effects and inhibits cell proliferation, whereas untransformed glia cells are unaffected by similar IMPDH2 perturbations. Impairment of IMPDH2 activity triggers nucleolar stress and growth arrest of GBM cells even in the absence of functional p53. Our results reveal that upregulation of IMPDH2 is a prerequisite for aberrant nucleolar function and increased anabolic processes in GBM, which constitutes a primary event in gliomagenesis.

RAS is the founding member of a superfamily of GTPases and regulates signaling pathways involved in cellular growth control. While recent studies have shown that the activation state of RAS can be controlled by lysine ubiquitylation and acetylation, the existence of lysine methylation of the RAS superfamily GTPases remains unexplored. In contrast to acetylation, methylation does not alter the side chain charge and it has been challenging to deduce its impact on protein structure by conventional amino acid substitutions. Herein, we investigate lysine methylation on RAS and RAS-related GTPases. We developed GoMADScan (Go language-based Modification Associated Database Scanner), a new user-friendly application that scans and extracts posttranslationally modified peptides from databases. The GoMADScan search on PhosphoSitePlus databases identified methylation of conserved lysine residues in the core GTPase domain of RAS superfamily GTPases, including residues corresponding to RAS Lys-5, Lys-16, and Lys-117. To follow up on these observations, we immunoprecipitated endogenous RAS from HEK293T cells, conducted mass spectrometric analysis and found that RAS residues, Lys-5 and Lys-147, undergo dimethylation and monomethylation, respectively. Since mutations of Lys-5 have been found in cancers and RASopathies, we set up molecular dynamics (MD) simulations to assess the putative impact of Lys-5 dimethylation on RAS structure. Results from our MD analyses predict that dimethylation of Lys-5 does not significantly alter RAS conformation, suggesting that Lys-5 methylation may alter existing protein interactions or create a docking site to foster new interactions. Taken together, our findings uncover the existence of lysine methylation as a novel posttranslational modification associated with RAS and the RAS superfamily GTPases, and putative impact of Lys-5 dimethylation on RAS structure.

Head and neck cancer (HNC) is the sixth most common malignancy worldwide. Despite recent advancements in surgical, chemotherapy, and radiation treatments, HNC remains a highly morbid and fatal disease. Unlike many other cancers, local control rather than systemic control is important for HNC survival. Therefore, novel local therapy in addition to systemic therapy is urgently needed. Oncolytic virotherapy holds promise in this regard as viruses can be injected intratumorally as well as intravenously with excellent safety profiles. This review will discuss the recent advancements in oncolytic virotherapy, highlighting some of the most promising candidates and modifications to date.

e16087 Background: Standard treatment for metastatic CRPC is docetaxel 75 mg/m2q3weeks. Methods: We retrospectively studied patients treated with q 1, 2, or 3 weeks docetaxel regimens at 30, 60 and 75 mg/m2, respectively. The choice of regimen and duration of treatment was decided by their oncologist. Patients who had been in a clinical trial previously, or treated with any other chemotherapy before docetaxel were excluded. On this basis 41 patients were studied. Prostate specific antigen (PSA) was used as the primary method to assess response and progression. Response was a decline of >/=50% from baseline value with no clinical or radiographic evidence of disease progression. For patients whose PSA did not decrease, progression was a >/= 25% increase from baseline. If the PSA decreased without reaching response criteria, progression was a >/= 25% increase from nadir. In those who responded, progression was a >/= 50% increase from nadir. The increase had to be at least 5ng/ml. Toxicity was graded on the basis of CTCAE version 4.0. Response rate and toxicity in the 3 arms was compared using a two by two square t-test. Results: There were 12, 14 and 15 patients in the q1w, q2w and q3w arms, respectively. Response rates, mean progression free survival (PFS), median PFS, mean overall survival (OS), median OS, mean cumulative dose (MCD) and toxicity are shown in table 1. Toxicity was similar in the q1w, q2w and q3w arms, except grade 1/2 neuropathy was higher in the q2w arm vs. the q1w arm (p=0.005). Conclusions: The MCD, response rates, PFS and OS in the q1w and q3w arms were similar to previously published reports. Patients in the q2w arm received a statistically significant higher MCD. Our data suggest a better outcome in the q2w arm as compared to the q1w and q3w arms. However, given the small number of patients studied, the results are not statistically significant. Toxicity was similar save for grade1/2 neuropathy. [Table: see text]

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