CMTM5 exhibits tumor suppressor activities and is frequently silenced by methylation in carcinoma cell lines

MARVELD1 inhibited cell proliferation and enhance chemosensitivity via increasing expression of p53 and p16 in hepatocellular carcinoma

We have previously found that expression of MARVELD1 was remarkably downregulated in multiple tumor tissues, but unclear in hepatocellular carcinoma (HCC) and its function has not been explored yet. In the present study, to uncover the underlying mechanism of MARVELD1 in the pathogenesis and development of HCC, we investigated the expression pattern of MARVELD1 and its effect on tumor proliferation in HCC. The results indicated the frequent downregulation of MARVELD1 in clinic samples and cell lines of HCC resulted from promoter methylation, as well as genetic deletion. Furthermore, treatment of MARVELD1 unexpressing Hep3B2.1-7 and PLC/PRF/5 cells with the demethylating agent 5-aza-2' deoxycytidine restored its expression. Overexpression of MARVELD1 suppressed the proliferation of HCC cells in vitro and in vivo, whereas downregulation of endogenous MARVELD1 by shRNAs significantly enhanced these characters. MARVELD1 overexpression could enhance chemosensitivity of HCC cells to epirubicin and 10-hydroxycamptothecin. Corresponding to these results, the expression of p-ERK1/2 and cyclin D1 were decreased, whereas p16 and p53 were increased in MARVELD1-transfected cells. We also demonstrated that knockdown of MARVELD1 resulted in upregulation of p-ERK1/2 and cyclin D1, and downregulation of p16 and p53. Moreover, the effect of the decreased cell growth rate was significantly reversed when MARVELD1-overexpressing cells were trasfected with p53 or p16 siRNA. Our findings suggest that MARVELD1 is a tumor suppressor by negatively regulating proliferation, tumor growth and chemosensitivity of HCC cells via increasing p53 and p16 in vitro and in vivo. MARVELD1 may be a potential target for HCC therapy.

Expression profiling after induction of demethylation in MCF-7 breast cancer cells identifies involvement of TNF-α mediated cancer pathways

Epigenetic methylation change is a major process that occurs during cancer development. Even though many tumor-related genes have been identified based on their relationship between methylation and expression, few studies have been conducted to investigate the relevant biological pathways involved in these changes. To identify essential pathways likely to be affected by methylation in breast cancer, we examined a pool of genes in which expression was upregulated after induction of demethylation by 5-Aza-2'-deoxycytidine (Aza) in the MCF-7 breast cancer cell line. Genome-wide demethylation was confirmed by monitoring the demethylation of a previously known gene, SULT1A1. Overall, 210 and 213 genes were found to be upregulated and downregulated (fold change ≥ 2), respectively, in common in cells treated with 5 and 10 μM of Aza. Network analysis of these 423 genes with altered expression patterns identified the involvement of a cancer related network of genes that were heavily regulated by TNF-α in breast tumorigenesis. Our results suggest that epigenetic dysregulation of cellular processes relevant to TNF-α-dependent apoptosis may be intimately involved in tumorigenesis in MCF-7 cells.

Quantitative and integrative proteome analysis of peripheral nerve myelin identifies novel myelin proteins and candidate neuropathy loci

Peripheral nerve myelin facilitates rapid impulse conduction and normal motor and sensory functions. Many aspects of myelin biogenesis, glia-axonal interactions, and nerve homeostasis are poorly understood at the molecular level. We therefore hypothesized that only a fraction of all relevant myelin proteins has been identified so far. Combining gel-based and gel-free proteomic approaches, we identified 545 proteins in purified mouse sciatic nerve myelin, including 36 previously known myelin constituents. By mass spectrometric quantification, the predominant P0, periaxin, and myelin basic protein constitute 21, 16, and 8% of the total myelin protein, respectively, suggesting that their relative abundance was previously misestimated due to technical limitations regarding protein separation and visualization. Focusing on tetraspan-transmembrane proteins, we validated novel myelin constituents using immuno-based methods. Bioinformatic comparison with mRNA-abundance profiles allowed the categorization in functional groups coregulated during myelin biogenesis and maturation. By differential myelin proteome analysis, we found that the abundance of septin 9, the protein affected in hereditary neuralgic amyotrophy, is strongly increased in a novel mouse model of demyelinating neuropathy caused by the loss of prion protein. Finally, the systematic comparison of our compendium with the positions of human disease loci allowed us to identify several candidate genes for hereditary demyelinating neuropathies. These results illustrate how the integration of unbiased proteome, transcriptome, and genome data can contribute to a molecular dissection of the biogenesis, cell biology, metabolism, and pathology of myelin.

Aberrant promoter CpG methylation and its translational applications in breast cancer

Breast cancer is a complex disease driven by multiple factors including both genetic and epigenetic alterations. Recent studies revealed that abnormal gene expression induced by epigenetic changes, including aberrant promoter methylation and histone modification, plays a critical role in human breast Carcinogenesis. Silencing of tumor suppressor genes (TSGs) by promoter CpG methylation facilitates cells growth and survival advantages and further results in tumor initiation and progression, thus directly contributing to breast tumorigenesis. Usually, aberrant promoter methylation of TSGs, which can be reversed by pharmacological reagents, occurs at the early stage of tumorigenesis and therefore may serve as a potential tumor marker for early diagnosis and therapeutic targeting of breast cancer. In this review, we summarize the epigenetic changes of multiple TSGs involved in breast pathogenesis and their potential clinical applications as tumor markers for early detection and treatment of breast cancer.

Identification and characterization of CMTM4, a novel gene with inhibitory effects on HeLa cell growth through Inducing G2/M phase accumulation

Human CMTM is a novel gene family consisting of CKLF and CMTM1-8. CMTM4 is the most conserved gene and has three RNA splicing forms designated as CMTM4-v1, -v2 and -v3, but in many types of tissue and cell lines, only CMTM4-v1 and -v2 could be detected. CMTM4-v2 is the full length cDNA product, which has been highly conserved during evolution. CMTM4-v1 and -v2 are broadly expressed in normal types of tissue. They are distributed on the cell membrane and across the cytoplasm in a speckled pattern. Overexpression of CMTM4-v1 and -v2 can inhibit HeLa cell growth via G2/M phase accumulation without inducing apoptosis. Therefore, CMTM4 might be an important gene involved in cell growth and cell cycle regulation.

CMTM3, located at the critical tumor suppressor locus 16q22.1, is silenced by CpG methylation in carcinomas and inhibits tumor cell growth through inducing apoptosis

Closely located at the tumor suppressor locus 16q22.1, CKLF-like MARVEL transmembrane domain-containing member 3 and 4 (CMTM3 and CMTM4) encode two CMTM family proteins, which link chemokines and the transmembrane-4 superfamily. In contrast to the broad expression of both CMTM3 and CMTM4 in normal human adult tissues, only CMTM3 is silenced or down-regulated in common carcinoma (gastric, breast, nasopharyngeal, esophageal, and colon) cell lines and primary tumors. CMTM3 methylation was not detected in normal epithelial cell lines and tissues, with weak methylation present in only 5 of 35 (14%) gastric cancer adjacent normal tissues. Furthermore, immunohistochemistry showed that CMTM3 protein was absent in 12 of 35 (34%) gastric and 1 of 2 colorectal tumors, which was well correlated with its methylation status. The silencing of CMTM3 is due to aberrant promoter CpG methylation that could be reversed by pharmacologic demethylation. Ectopic expression of CMTM3 strongly suppressed the colony formation of carcinoma cell lines. In addition, CMTM3 inhibited tumor cell growth and induced apoptosis with caspase-3 activation. Thus, CMTM3 exerts tumor-suppressive functions in tumor cells, with frequent epigenetic inactivation by promoter CpG methylation in common carcinomas.

Identification and characterization of MARVELD1, a novel nuclear protein that is down-regulated in multiple cancers and silenced by DNA methylation

MARVELD1 (MARVEL domain-containing 1) is a member of MARVEL domain-containing proteins and located on human chromosome 10q24.2. MARVELD1 has no significant similarity with other members of MARVEL domain family at amino acid level. Gene expression arrays demonstrated that MARVELD1 is widely expressed in normal human tissues and is down-regulated in primary multiple tumors derived from ovary, vulva, uterus, cervix, breast, testis, kidney, bladder and liver. The down-regulation of MARVELD1 was further identified by real-time PCR and immunohistochemical staining in primary breast cancer. In addition, we identified the reduced expression of MARVELD1 is owing to DNA methylation and could be reversed by pharmacologic demethylation. Finally, our results showed that MARVELD1 protein is located in nucleus instead of cell membrane.

Epigenetic dysregulation of the host cell genome in Epstein-Barr virus-associated neoplasia

Epstein-Barr virus (EBV), a human herpesvirus, is associated with a wide variety of malignant tumors. The expression of the latent viral RNAs is under strict, host-cell dependent transcriptional control. This results in an almost complete transcriptional silencing of the EBV genome in memory B-cells. In tumor cells, germinal center B-cells and lymphoblastoid cells, distinct viral latency promoters are active. Epigenetic mechanisms contribute to this strict control. In EBV-infected cells, epigenetic mechanisms also alter the expression of cellular genes, including tumor suppressor genes. In Nasopharyngeal Carcinoma, the hypermethylation of certain cellular promoters is attributed to the upregulation of DNA methyltransferases by the viral oncoprotein LMP1 (latent membrane protein 1) via JNK/AP1-signaling. The role of other viral latency products in the epigenetic dysregulation of the cellular genome remains to be established. Analysis of epigenetic alterations in EBV-associated neoplasms may result in a better understanding of their pathogenesis and may facilitate the development of new therapies.

The preclinical activity of the histone deacetylase inhibitor PXD101 (belinostat) in hepatocellular carcinoma cell lines

The activity of the histone deacetylase inhibitor PXD101 was investigated in three hepatocellular carcinoma (HCC) cell lines. PXD101 was found to inhibit cell growth at a dose-dependent manner and induce histone acetylation in PLC/PRF/5, Hep3B and HepG2 cells. In PLC/PRF/5 and Hep3B cells which express hepatitis B-related genes (HBx, HBc and HBc), treatment with PXD101 resulted in apoptosis without a significant effect on viral gene expression. Exposure to PXD101 for up to 48 h had varying effects on the expression of 12 cellular genes with tumor suppressor functions, including p21, SOCS1, CMTM5, RASAL1, DLEC1, SFRP (-1, -2, -4 and -5), ADAMTS (-8 and -9). This study provided the basis for a phase II clinical trial of PXD101 in inoperable hepatitis-B associated HCC.