PIMREG expression level predicts glioblastoma patient survival and affects temozolomide resistance and DNA damage response.

PIMREG expression strongly correlates with cellular proliferation in both malignant and normal cells. Throughout embryo development, PIMREG expression is prominent in the central nervous system. Recent studies have described elevated PIMREG expression in different types of tumors, which correlates with patient survival and tumor aggressiveness. Given the emerging significance of PIMREG in carcinogenesis and its putative role in the context of the nervous system, we investigated the expression and function of PIMREG in gliomas, the most common primary brain tumors. We performed an extensive analysis of PIMREG expression in tumors samples from glioma patients. We then assessed the effects of PIMREG silencing and overexpression on the sensitivity of glioblastoma cell lines treated with genotoxic agents commonly used for treating patients and assessed for treatment response, proliferation and migration. Our analysis shows that glioblastoma exhibits the highest levels of PIMREG expression among all cancers analyzed and that elevated PIMREG expression is a biomarker for glioma progression and patient outcome. Moreover, PIMREG is induced by genotoxic agents, and its silencing renders glioblastoma cells sensitive to temozolomide treatment and affects ATR- and ATM-dependent signaling. Our data demonstrate that PIMREG is involved in DNA damage response and temozolomide resistance of glioblastoma cells and further supports a role for PIMREG in tumorigenesis.

The U2AF homology motif kinase 1 (UHMK1) is upregulated upon hematopoietic cell differentiation.

UHMK1 (KIS) is a nuclear serine/threonine kinase that possesses a U2AF homology motif and phosphorylates and regulates the activity of the splicing factors SF1 and SF3b155. Mutations in these components of the spliceosome machinery have been recently implicated in leukemogenesis. The fact that UHMK1 regulates these factors suggests that UHMK1 might be involved in RNA processing and perhaps leukemogenesis. Here we analyzed UHMK1 expression in normal hematopoietic and leukemic cells as well as its function in leukemia cell line. In the normal hematopoietic compartment, markedly higher levels of transcripts were observed in differentiated lymphocytes (CD4+, CD8+ and CD19+) compared to the progenitor enriched subpopulation (CD34+) or leukemia cell lines. UHMK1 expression was upregulated in megakaryocytic-, monocytic- and granulocytic-induced differentiation of established leukemia cell lines and in erythrocytic-induced differentiation of CD34+ cells. No aberrant expression was observed in patient samples of myelodysplastic syndrome (MDS), acute myeloid (AML) or lymphoblastic (ALL) leukemia. Nonetheless, in MDS patients, increased levels of UHMK1 expression positively impacted event free and overall survival. Lentivirus mediated UHMK1 knockdown did not affect proliferation, cell cycle progression, apoptosis or migration of U937 leukemia cells, although UHMK1 silencing strikingly increased clonogenicity of these cells. Thus, our results suggest that UHMK1 plays a role in hematopoietic cell differentiation and suppression of autonomous clonal growth of leukemia cells.