Genomics screen in transformed stem cells reveals RNASEH2A, PPAP2C, and ADARB1 as putative anticancer drug targets

Abstract

Since the sequencing of the human genome, recent efforts in cancer drug target discovery have focused more on the identification of novel functions of known genes and the development of more appropriate tumor models. In the present study, we investigated in vitro transformed human adult mesenchymal stem cells (MSC) to identify novel candidate cancer drug targets by analyzing the transcriptional profile of known enzymes compared with non-transformed MSC. The identified enzymes were compared with published cancer gene expression data sets. Surprisingly, the majority of up-regulated enzymes are already known cancer drug targets or act within known druggable pathways. Only three enzymes (RNASEH2A, ADARB1, and PPAP2C) are potentially novel targets that are up-regulated in transformed MSC and expressed in numerous carcinomas and sarcomas. We confirmed the overexpression of RNASEH2A, PPAP2C, and ADARB1 in transformed MSC, transformed fibroblasts, and cancer cell lines MCF7, SK-LMS1, MG63, and U2OS. In functional assays, we show that small interfering RNA knockdown of RNASEH2A inhibits anchorage-independent growth but does not alter in vitro proliferation of cancer cell lines, normal MSC, or normal fibroblasts. Knockdown of PPAP2C impaired anchorage-dependent in vitro growth of cancer cell lines and impaired the in vitro growth of primary MSC but not differentiated human fibroblasts. We show that the knockdown of PPAP2C decreases cell proliferation by delaying entry into S phase of the cell cycle and is transcriptionally regulated by p53. These in vitro data validate PPAP2C and RNASEH2A as putative cancer targets and endorse this in silico approach for identifying novel candidates.

DNA-Sensing and Nuclease Gene Expressions as Markers for Colorectal Cancer Progression

“…Of note, we detected the heterogeneous RNase H2 subunit's mRNA expression in colon cancer tissues: while RNASEH2C was suppressed, RNASEH2A was upregulated. Such a finding is in agreement with the findings of Flanagan et al [34] , which showed RNASEH2A upregulation in breast/bladder/brain/head and neck cancers, in seminomas, and in leukemia and which further suggested a pro-survival role of RNASEH2A in cancers. Although RNASEH2A encodes the main catalytic subunit of RNase H2, which cleaves misincorporated ribonucleotide during DNA replication [6,35] , RNASEH2B and RNASEH2C could form a stable complex without RNASEH2A , and they could interact with other proteins to exert cellular functions beyond enzymatic activity [36,37] .…”

Genome-wide reprogramming of the chromatin landscape underlies endocrine therapy resistance in breast cancer

“…This highlights the need to further investigate the molecular mechanisms that contribute to resistance. Transcriptional profiles have previously helped identify druggable pathways in cancer (78)(79)(80)(81), and recent sequencing efforts have identified mutated molecular pathways involved in ETR in breast cancer (77). However, epigenetic reprogramming of regulatory elements is increasingly being recognized for its contribution to cancer development (82).…”

Lipid phosphate phosphatases and their roles in mammalian physiology and pathology

“…These investigators also compared data from a genomic screen between normal and transformed mesenchymal stem cells. PPAP2C / LPP2 was identifi ed as one target whose expression is elevated in numerous carcinomas and sarcomas ( 100 ). In contrast to the targeting of LPP1 and LPP2, knockdown of LPP3 (Ppap2C) in mice produces a very severe phenotype resulting in embryo death around E9.5 ( 101 ).…”