Abnormal DNA methylation at the C-5 position of cytosine (5mC) of CpG dinucleotides is a well-known epigenetic feature of cancer. Levels of E-cadherin, which is regularly expressed in epithelial tissues, are frequently reduced in epithelial tumors due to transcriptional repression, sometimes accompanied by hypermethylation of the promoter region. δEF1 family proteins (δEF1/ZEB1 and SIP1/ZEB2), key regulators of the epithelial-mesenchymal transition (EMT), suppress E-cadherin expression at the transcriptional level. We recently showed that levels of mRNAs encoding δEF1 proteins are regulated reciprocally with E-cadherin level in breast cancer cells. Here, we examined the mechanism underlying downregulation of E-cadherin expression in three basal-type breast cancer cells in which the E-cadherin promoter region is hypermethylated (Hs578T) or moderately methylated (BT549 and MDA-MB-231). Regardless of methylation status, treatment with 5-aza-2′-deoxycytidine (5-aza), which inhibits DNA methyltransferases, had no effect on E-cadherin expression. Knockdown of δEF1 and SIP1 resulted in recovery of E-cadherin expression in cells lacking hypermethylation, whereas combined treatment with 5-aza synergistically restored E-cadherin expression, especially when the E-cadherin promoter was hypermethylated. Moreover, δEF1 interacted with DNA methyltransferase 1 (DNMT1) through the Smad-binding domain. Sustained knockdown of δEF1 family proteins reduced the number of 5mC sites in the E-cadherin promoter region, suggesting that these proteins maintain 5mC through interaction with DNMT1 in breast cancer cells. Thus, δEF1 family proteins appear to repress expression of E-cadherin during cancer progression, both directly at the transcriptional level and indirectly at the epigenetic level.

Epithelial-mesenchymal transition (EMT) is a crucial event in wound healing, tissue repair, and cancer progression in adult tissues. Transforming growth factor (TGF)-b induces EMT in mouse epithelial cells. During prolonged treatment, TGF-b successively induces myofibroblastic differentiation with increased expression of myofibroblast marker proteins, including smooth muscle a actin and calponin. We recently showed that fibroblast growth factor-2 prevented myofibroblastic differentiation induced by TGF-b, and transdifferentiated the cells to those with much more aggressive characteristics (enhanced EMT). To identify the molecular markers specifically expressed in cells undergoing enhanced EMT induced by the combination of TGF-b and fibroblast growth factor-2, we carried out a microarray-based analysis and found that integrin a3 (ITGA3) and Ret were upregulated. Intriguingly, ITGA3 was also overexpressed in breast cancer cells with aggressive phenotypes and its expression was correlated with that of dEF-1, a key regulator of EMT. Moreover, the expression of both genes was downregulated by U0126, a MEK 1 ⁄ 2 inhibitor. Therefore, ITGA3 is a potential marker protein for cells undergoing enhanced EMT and for cancer cells with aggressive phenotypes, which is positively regulated by dEF-1 and the MEK-ERK pathway. (Cancer Sci 2013; 104: 1189-1197 E pithelial-mesenchymal transition (EMT) serves as a switch directing polarized epithelial cells to transdifferentiate into mesenchymal cells. During the processes of embryonic development, wound healing, and reorganization of adult tissues, epithelial cells have been shown to lose their epithelial polarity and acquire mesenchymal phenotypes.(1) Furthermore, EMT is involved in the process of tumor-cell invasion, which also includes the loss of cell-cell interaction. Thus far, in most cases, EMT appears to be regulated by ECM components and soluble growth factors or cytokines. Of these, transforming growth factor-b (TGF-b) is considered to be the key inducer of EMT during physiological processes.(2) TGF-b is frequently and abundantly expressed in various tumors, and also induces EMT in cancer cells during cancer progression. Several extracellular signaling molecules, including Wnt, epidermal growth factor, fibroblast growth factor (FGF)-2, and tumor necrosis factor-a, cooperate with TGF-b to promote tumor invasion and metastasis as well as EMT. In addition, constitutively active Ras dramatically enhances TGF-binduced expression of Snail, a key mediator of EMT, whereas representative target genes of TGF-b are either unaffected or slightly inhibited by Ras signaling, leading to selective synergism between TGF-b and Ras as well as soluble factors in cancer progression. TGF-b has been found to induce EMT in normal mouse mammary epithelial NMuMG cells, and we recently showed that prolonged treatment of NMuMG cells with TGF-b induces the epithelial-myofibroblastic transition (EMyoT) with the expression of myofibroblast markers, smooth muscle a actin (a-SMA), and calponin.(4) During T...

We present a case of primary hepatic choriocarcinoma in an 83-year-old Japanese woman with gastric wall and lymph node metastases and a splenic vein tumor thrombus. Multiple irregular hepatic tumors with massive necrosis and hemorrhage were observed during autopsy. Syncytiotrophoblast-like and mononucleated cytotrophoblast-like cell morphology with focal hepatocellular carcinoma (HCC)-like trabecular structures was observed. In immunohistochemical analyses, the tumor cells expressed human chorionic gonadotropin (hCG) and cytokeratins (AE1/AE3, CK7, CK19) but were negative for alpha-fetoprotein (AFP), glypican-3, and vimentin. Immunohistochemical findings did not reveal evidence of HCC or angiosarcoma. We concluded the liver tumor was primary hepatic choriocarcinoma.

The epithelial–mesenchymal transition (EMT) is associated with tumor progression. We reported previously that expression of the δEF1 family proteins (δEF1/ZEB1 and SIP1/ZEB2), key regulators of the EMT, is positively correlated with EMT phenotypes and aggressiveness of breast cancer. Here, we show that the expression levels of regulator of G‐protein signaling 16 (RGS16) are negatively correlated with those of the δEF1 family proteins. On the basis of the results of gain‐ and loss‐of‐function analyses, we suggest that δEF1 family proteins promote cell motility of breast cancer cells directly or indirectly through repressing expression of RGS16.

Structural variants (SVs) are responsible for driver events in gastric cancer (GC); however, their patterns and processes remain poorly understood. Here, we examine 170 GC whole genomes to unravel the oncogenic structural aberration landscape in GC genomes and identify six rearrangement signatures (RSs). Non-random combinations of RSs elucidate distinctive GC subtypes comprising one or a few dominant RS that are associated with specific driver events (BRCA1/2 defects, mismatch repair deficiency, and TP53 mutation) and epidemiological backgrounds. Twenty-seven SV hotspots are identified as GC driver candidates. SV hotspots frequently constitute complexly clustered SVs involved in driver gene amplification, such as ERBB2, CCNE1, and FGFR2. Further deconstruction of the locally clustered SVs uncovers amplicon-generating profiles characterized by super-large SVs and intensive segmental amplifications, contributing to the extensive amplification of GC oncogenes. Comprehensive analyses using adjusted SV allele frequencies indicate the significant involvement of extra-chromosomal DNA in processes linked to specific RSs.