N6-methyladenosine (m6A) is the most abundant epitranscriptome modification in mammalian mRNA. Recent years have seen substantial progress in m6A epitranscriptomics, indicating its crucial roles in the initiation and progression of cancer through regulation of RNA stabilities, mRNA splicing, microRNA processing and mRNA translation. However, by what means m6A is dynamically regulated or written by enzymatic components represented by methyltransferase-like 3 (METTL3) and how m6A is significant for each of the numerous genes remain unclear. We focused on METTL3 in pancreatic cancer, the prognosis of which is not satisfactory despite the development of multidisciplinary therapies. We established METTL3-knockdown pancreatic cancer cell line using short hairpin RNA. Although morphologic and proliferative changes were unaffected, METTL3-depleted cells showed higher sensitivity to anticancer reagents such as gemcitabine, 5-fluorouracil, cisplatin and irradiation. Our data suggest that METTL3 is a potent target for enhancing therapeutic efficacy in patients with pancreatic cancer. In addition, we performed cDNA expression analysis followed by gene ontology and protein-protein interaction analysis using the Database for Annotation, Visualization, and Integrated Discovery and Search Tool for the Retrieval of Interacting Genes/Proteins databases, respectively. The results demonstrate that METTL3 was associated with mitogen-activated protein kinase cascades, ubiquitin-dependent process and RNA splicing and regulation of cellular process, suggesting functional roles and targets of METTL3.

Although cancer is a disease with genetic and epigenetic origins, the possible effects of reprogramming by defined factors remain to be fully understood. We studied the effects of the induction or inhibition of cancer-related genes and immature status-related genes whose alterations have been reported in gastrointestinal cancer cells. Retroviral-mediated introduction of induced pluripotent stem (iPS) cell genes was necessary for inducing the expression of immature status-related proteins, including Nanog, Ssea4, Tra-1-60, and Tra-1-80 in esophageal, stomach, colorectal, liver, pancreatic, and cholangiocellular cancer cells. Induced cells, but not parental cells, possessed the potential to express morphological patterns of ectoderm, mesoderm, and endoderm, which was supported by epigenetic studies, indicating methylation of DNA strands and the histone H3 protein at lysine 4 in promoter regions of pluripotency-associated genes such as NANOG . In in vitro analysis induced cells showed slow proliferation and were sensitized to differentiation-inducing treatment, and in vivo tumorigenesis was reduced in NOD/SCID mice. This study demonstrated that pluripotency was manifested in induced cells, and that the induced pluripotent cancer (iPC) cells were distinct from natural cancer cells with regard to their sensitivity to differentiation-inducing treatment. Retroviral-mediated introduction of iPC cells confers higher sensitivity to chemotherapeutic agents and differentiation-inducing treatment.

Oncogene c-Myc promotes epitranscriptome m6A reader YTHDF1 expression in colorectal cancer

Significance: Our study shows that pyruvate kinase M2 (PKM2), an alternatively spliced variant of the pyruvate kinase gene, mediates epithelial–mesenchymal transition (EMT), which is critical for cancer cells to acquire invasive potential. Our study demonstrates that EMT stimulates nuclear translocation of PKM2 and decreases epithelial cadherin transcription (a requirement for EMT induction). Our results also demonstrate that PKM2 interacts with the transcriptional factor TGF-β–induced factor homeobox 2, which induces the deacetylation of histone H3, resulting in repressed E-cadherin expression. The precise understanding of nuclear PKM2 function suggests the potential for a model preventing cancer metastasis.

The biological significance of micro (mi)RNAs has traditionally been evaluated according to their RNA expression levels based on the assumption that miRNAs recognize and regulate their targets in an unvarying fashion. Here we show that a fraction of mature miRNAs including miR-17-5p, -21-5p, and -200c-3p and let-7a-5p harbor methyl marks that potentially alter their stability and target recognition. Importantly, methylation of these miRNAs was significantly increased in cancer tissues as compared to paired normal tissues. Furthermore, miR-17-5p methylation level in serum samples distinguished early pancreatic cancer patients from healthy controls with extremely high sensitivity and specificity. These findings provide a basis for diagnostic strategies for early-stage cancer and add a dimension to our understanding of miRNA biology.

Widespread alteration of the genomic DNA is a hallmark of tumors, and alteration of genes involved in DNA maintenance have been shown to contribute to the tumorigenic process. The DNA polymerase ζ of Saccharomyces cerevisiae is required for error-prone repair following DNA damage and consists of a complex between three proteins, scRev1, scRev3, and scRev7. Here we describe a candidate human homolog of S. cerevisiae Rev7 (hREV7), which was identified in a yeast two-hybrid screen using the human homolog of S. cerevisiae Rev3 (hREV3). The hREV7 gene product displays 23% identity and 53% similarity with scREV7, as well as 23% identity and 54% similarity with the human mitotic checkpoint protein hMAD2. hREV7 is located on human chromosome 1p36 in a region of high loss of heterozygosity in human tumors, although no alterations of hREV3 or hREV7 were found in primary human tumors or human tumor cell lines. The interaction domain between hREV3 and hREV7 was determined and suggests that hREV7 probably functions with hREV3 in the human DNA polymerase ζ complex. In addition, we have identified an interaction between hREV7 and hMAD2 but not hMAD1. While overexpression of hREV7 does not lead to cell cycle arrest, we entertain the possibility that it may act as an adapter between DNA repair and the spindle assembly checkpoint.