Identification of lysine methylation in the core GTPase domain by GoMADScan.

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.

Correction: Identification of lysine methylation in the core GTPase domain by GoMADScan.

[This corrects the article DOI: 10.1371/journal.pone.0219436.].

IMP dehydrogenase-2 drives aberrant nucleolar activity and promotes tumorigenesis in glioblastoma.

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. 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 glioblastoma 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 glioblastoma cells even in the absence of functional p53. Our results reveal that upregulation of IMPDH2 is a prerequisite for the occurance of aberrant nucleolar function and increased anabolic processes in glioblastoma, which constitutes a primary event in gliomagenesis.

Efficacy and Toxicity of Every 2 Weeks Docetaxel Regimen in Comparison With Weekly or Every 3 Weeks in Metastatic Prostate Cancer: A Retrospective Analysis.

OBJECTIVES: The aim of this study was to compare weekly (q1w), 2 weekly (q2w), and 3 weekly (q3w) regimens of docetaxel in metastatic castration-resistant prostate cancer (CRPC). MATERIALS AND METHODS: We retrospectively studied patients treated with q1w, q2w, or q3w docetaxel regimens at 30, 60, and 75 mg/m, respectively. The choice and duration of treatment was decided by their oncologist. Patients were assessed for response, progression-free survival (PFS), and overall survival (OS), and toxicity. RESULTS: Twelve, 14, and 15 patients were in the q1w, q2w, and q3w arms, respectively. Patients' age, metastases, and mean prostate-specific antigen at start and nadir were similar among groups. Mean total dose (MTD) was higher (not significantly) in the q2w group. Response rates, mean, and median PFS and OS ranked q2w>q3w>q1w (not significantly). However, hazard ratios for PFS for the q2w and q3w arms were statistically superior to the q1w arm when adjusted for age and total dose. The same was true for OS when q3w was compared with q1w. There were no significant differences between the q2w and q3w arms. Toxicities were not different between any of the arms, save for grade 1/2 neuropathy (lower in q1w compared with q2w). CONCLUSIONS: The MTD, response rates, PFS, and OS in the q1w and q3w arms were similar to published reports. Although we had a small number of patients, our findings suggest that both dose concentration and total docetaxel dose may be important in the treatment of CRPC and q2w dosing is an option in patients intolerant of a higher dose concentration.

Oncolytic virotherapy for head and neck cancer: current research and future developments.

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.