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

Predictive Role of Cluster Bean (Cyamopsis tetragonoloba) Derived miRNAs in Human and Cattle Health

MicroRNAs (miRNAs) are small non-coding conserved molecules with lengths varying between 18-25nt. Plants miRNAs are very stable, and probably they might have been transferred across kingdoms via food intake. Such miRNAs are also called exogenous miRNAs, which regulate the gene expression in host organisms. The miRNAs present in the cluster bean, a drought tolerant legume crop having high commercial value, might have also played a regulatory role for the genes involved in nutrients synthesis or disease pathways in animals including humans due to dietary intake of plant parts of cluster beans. However, the predictive role of miRNAs of cluster beans for gene-disease association across kingdoms such as cattle and humans are not yet fully explored. Thus, the aim of the present study is to (i) find out the cluster bean miRNAs (cb-miRs) functionally similar to miRNAs of cattle and humans and predict their target genes' involvement in the occurrence of complex diseases, and (ii) identify the role of cb-miRs that are functionally non-similar to the miRNAs of cattle and humans and predict their targeted genes' association with complex diseases in host systems. Here, we predicted a total of 33 and 15 functionally similar cb-miRs (fs-cb-miRs) to human and cattle miRNAs, respectively. Further, Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed the participation of targeted genes of fs-cb-miRs in 24 and 12 different pathways in humans and cattle, respectively. Few targeted genes in humans like LCP2, GABRA6, and MYH14 were predicted to be associated with disease pathways of Yesinia infection (hsa05135), neuroactive ligand-receptor interaction (hsa04080), and pathogenic Escherichia coli infection (hsa05130), respectively. However, targeted genes of fs-cb-miRs in humans like KLHL20, TNS1, and PAPD4 are associated with Alzheimer's, malignant tumor of the breast, and hepatitis C virus infection disease, respectively. Similarly, in cattle, targeted genes like ATG2B and DHRS11 of fs-cb-miRs participate in the pathways of Huntington disease and steroid biosynthesis, respectively. Additionally, the targeted genes like SURF4 and EDME2 of fs-cb-miRs are associated with mastitis and bovine osteoporosis, respectively. We also found a few cb-miRs that do not have functional similarity with human and cattle miRNAs but are found to target the genes in the host organisms and as well being associated with human and cattle diseases. Interestingly, a few genes such as NRM, PTPRE and SUZ12 were observed to be associated with Rheumatoid Arthritis, Asthma and Endometrial Stromal Sarcoma diseases, respectively, in humans and genes like SCNN1B associated with renal disease in cattle.

Research insights into the chemokine-like factor (CKLF)-like MARVEL transmembrane domain-containing family (CMTM): their roles in various tumors

The chemokine-like factor (CKLF)-like MARVEL transmembrane domain-containing (CMTM) family includes CMTM1-8 and CKLF, and they play key roles in the hematopoietic, immune, cardiovascular, and male reproductive systems, participating in the physiological functions, cancer, and other diseases associated with these systems. CMTM family members activate and chemoattract immune cells to affect the proliferation and invasion of tumor cells through a similar mechanism, the structural characteristics typical of chemokines and transmembrane 4 superfamily (TM4SF). In this review, we discuss each CMTM family member's chromosomal location, involved signaling pathways, expression patterns, and potential roles, and mechanisms of action in pancreatic, breast, gastric and liver cancers. Furthermore, we discuss several clinically applied tumor therapies targeted at the CMTM family, indicating that CMTM family members could be novel immune checkpoints and potential targets effective in tumor treatment.

Current Opinions on the Relationship Between CMTM Family and Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a typically malignant tumor in the digestive system. The mortality of HCC ranks third place in the world, second only to lung cancer and colorectal cancer. For the characteristics of high invasiveness, high metastasis, high recurrence rate as well as short survival time, HCC treatment has always been difficult in clinical practice. Many causes have contributed to the appearance of these features, including insidious onset, high degree of malignancy, lack of effective early molecular diagnostic markers, and disease prediction models. The human chemokine-like factor superfamily (CMTMs) is a new gene family consisting of CKLF and CMTM1-CMTM8. CMTMs have a marvel domain which can activate and chemotaxis immune cells. Many studies have reported that CMTMs are involved in the regulation of cell growth and development, and play an important role in the malignant progression of the immune system and reproductive system, especially in the development of tumors. In this review, we summarized the structure and function of the human CMTMs, the relationship between its family members and HCC, the prognostic value, potential functions, and mechanisms in HCC. CMTMs could provide a new diagnostic and therapeutic target in clinical practice for patients with HCC.

Loss of the Novel Myelin Protein CMTM5 in Multiple Sclerosis Lesions and Its Involvement in Oligodendroglial Stress Responses

This study comprehensively addresses the involvement of the protein CKLF-like Marvel transmembrane domain-containing family member 5 (CMTM5) in the context of demyelination and cytodegenerative autoimmune diseases, particularly multiple Sclerosis (MS). An observed reduction in CMTM5 expression in post-mortem MS lesions prompted further investigations in both in vitro and in vivo animal models. In the cuprizone animal model, we detected a decrease in CMTM5 expression in oligodendrocytes that is absent in other members of the CMTM protein family. Our findings also confirm these results in the experimental autoimmune encephalomyelitis (EAE) model with decreased CMTM5 expression in both cerebellum and spinal cord white matter. We also examined the effects of a Cmtm5 knockdown in vitro in the oligodendroglial Oli-neu mouse cell line using the CRISPR interference technique. Interestingly, we found no effects on cell response to thapsigargin-induced endoplasmic reticulum (ER) stress as determined by Atf4 activity, an indicator of cellular stress responses. Overall, these results substantiate previous findings suggesting that CMTM5, rather than contributing to myelin biogenesis, is involved in maintaining axonal integrity. Our study further demonstrates that the knockdown of Cmtm5 in vitro does not modulate oligodendroglial responses to ER stress. These results warrant further investigation into the functional role of CMTM5 during axonal degeneration in the context of demyelinating conditions.

CMTM7 inhibits breast cancer progression by regulating Wnt/β-catenin signaling

BACKGROUND

Breast cancer is the major cause of death in females globally. Chemokine-like factor like MARVEL transmembrane domain containing 7 (CMTM7) is reported as a tumor suppressor and is involved in epidermal growth factor receptor degradation and PI3K/AKT signaling in previous studies. However, other molecular mechanisms of CMTM7 remain unclear.

METHODS

The expression level of CMTM7 in breast cancer cells and tissues was detected by qRT-PCR and western blot, and the methylation of CMTM7 promoter was detected by BSP sequencing. The effect of CMTM7 was verified both in vitro and in vivo, including MTT, colony formation, EdU assay, transwell assay and wound healing assay. The interaction between CMTM7 and CTNNA1 was investigated by co-IP assay. The regulation of miR-182-5p on CMTM7 and TCF3 on miR-182-5p was detected by luciferase reporter assay and ChIP analysis.

RESULTS

This study detected the hypermethylation levels of the CMTM7 promoter region in breast cancer tissues and cell lines. CMTM7 was performed as a tumor suppressor both in vitro and in vivo. Furthermore, CMTM7 was a direct miR-182-5p target. Besides, we found that CMTM7 could interact with Catenin Alpha 1 (CTNNA1) and regulate Wnt/β-catenin signaling. Finally, transcription factor 3 (TCF3) can regulate miR-182-5p. We identified a feedback loop with the composition of miR-182-5p, CMTM7, CTNNA1, CTNNB1 (β-catenin), and TCF3, which play essential roles in breast cancer progression.

CONCLUSION

These findings reveal the emerging character of CMTM7 in Wnt/β-catenin signaling and bring new sights of gene interaction. CMTM7 and other elements in the feedback loop may serve as emerging targets for breast cancer therapy.

CMTM6 and CMTM4 as two novel regulators of PD-L1 modulate the tumor microenvironment

The tumor microenvironment (TME) plays crucial roles in regulating tumor occurrence, progress, metastasis and drug resistance. However, it remains largely elusive how the components of TME are regulated to govern its functions in tumor biology. Here, we discussed how the two novel functional proteins, chemokine-like factor (CKLF)-like MARVEL transmembrane domain-containing 6 (CMTM6) and CMTM4, which involved in the post-translational regulation of PD-L1, modulate the TME functions. The roles of CMTM6 and CMTM4 in regulating TME components, including immune cells and tumor cells themselves were discussed in this review. The potential clinical applications of CMTM6 and CMTM4 as biomarkers to predict therapy efficacy and as new or combined immunotherapy targets are also highlighted. Finally, the current hot topics for the biological function of CMTM6/4 and several significant research directions for CMTM6/4 are also briefly summarized in the review.

ordinalbayes: Fitting Ordinal Bayesian Regression Models to High-Dimensional Data Using R

The stage of cancer is a discrete ordinal response that indicates the aggressiveness of disease and is often used by physicians to determine the type and intensity of treatment to be administered. For example, the FIGO stage in cervical cancer is based on the size and depth of the tumor as well as the level of spread. It may be of clinical relevance to identify molecular features from high-throughput genomic assays that are associated with the stage of cervical cancer to elucidate pathways related to tumor aggressiveness, identify improved molecular features that may be useful for staging, and identify therapeutic targets. High-throughput RNA-Seq data and corresponding clinical data (including stage) for cervical cancer patients have been made available through The Cancer Genome Atlas Project (TCGA). We recently described penalized Bayesian ordinal response models that can be used for variable selection for over-parameterized datasets, such as the TCGA-CESC dataset. Herein, we describe our ordinalbayes R package, available from the Comprehensive R Archive Network (CRAN), which enhances the runjags R package by enabling users to easily fit cumulative logit models when the outcome is ordinal and the number of predictors exceeds the sample size, P > N, such as for TCGA and other high-throughput genomic data. We demonstrate the use of this package by applying it to the TCGA cervical cancer dataset. Our ordinalbayes package can be used to fit models to high-dimensional datasets, and it effectively performs variable selection.

CMTM Family and Gastrointestinal Tract Cancers: A Comprehensive Review

Gastrointestinal tract cancers are a highly heterogeneous group of malignant diseases, contributing significantly to the burden of death worldwide. Chemokine-like factor (CKLF)-like MARVEL transmembrane domain-containing family (CMTMs) plays important roles in cancer development and progression. Since the first member was cloned, there have been abundant studies on the relationships between the CMTM family and human cancers. It has been reported that the CMTM family has a large potential prognostic value for multiple cancers. Meanwhile, upregulated or downregulated expression of the family members was related to advanced tumor stage, metastasis, and overall survival. Studies have also reported that these proteins play critical roles in antitumor immunity. We performed a systematic review to sum up the latest advances of CMTM family’ roles in gastrointestinal tract cancers, with a primary focus on hepatocellular carcinoma and gastric carcinoma.

Progressive axonopathy when oligodendrocytes lack the myelin protein CMTM5

Oligodendrocytes facilitate rapid impulse propagation along the axons they myelinate and support their long-term integrity. However, the functional relevance of many myelin proteins has remained unknown. Here, we find that expression of the tetraspan-transmembrane protein CMTM5 (chemokine-like factor-like MARVEL-transmembrane domain containing protein 5) is highly enriched in oligodendrocytes and central nervous system (CNS) myelin. Genetic disruption of the Cmtm5 gene in oligodendrocytes of mice does not impair the development or ultrastructure of CNS myelin. However, oligodendroglial Cmtm5 deficiency causes an early-onset progressive axonopathy, which we also observe in global and tamoxifen-induced oligodendroglial Cmtm5 mutants. Presence of the Wld^S mutation ameliorates the axonopathy, implying a Wallerian degeneration-like pathomechanism. These results indicate that CMTM5 is involved in the function of oligodendrocytes to maintain axonal integrity rather than myelin biogenesis.

Identification of Novel Lung Cancer Driver Genes Connecting Different Omics Levels With a Heat Diffusion Algorithm

Cancer driver gene is a type of gene with abnormal alterations that initiate or promote tumorigenesis. Driver genes can be used to reveal the fundamental pathological mechanisms of tumorigenesis. These genes may have pathological changes at different omics levels. Thus, identifying cancer driver genes involving two or more omics levels is essential. In this study, a computational investigation was conducted on lung cancer driver genes. Four omics levels, namely, epigenomics, genomics, transcriptomics, and post-transcriptomics, were involved. From the driver genes at each level, the Laplacian heat diffusion algorithm was executed on a protein–protein interaction network for discovering latent driver genes at this level. A following screen procedure was performed to extract essential driver genes, which contained three tests: permutation, association, and function tests, which can exclude false-positive genes and screen essential ones. Finally, the intersection operation was performed to obtain novel driver genes involving two omic levels. The analyses on obtained genes indicated that they were associated with fundamental pathological mechanisms of lung cancer at two corresponding omics levels.

Epigenetic modifications inhibit the expression of MARVELD1 and in turn tumorigenesis by regulating the Wnt/β-catenin pathway in pan-cancer

MARVEL domain-containing 1 (MARVELD1) is one of the MARVEL domain-containing proteins. Expression of MARVELD1 in tumor and non-tumor tissues, the relationship between its expression and cancer prognosis, and upstream regulation of MARVELD1 were examined using pan-cancer data from The Cancer Genome Atlas. MARVELD1 expression was significantly downregulated in tissues used for pan-cancer analysis compared to that in normal tissues. Low expression of MARVELD1 was associated with poor disease outcomes in pan-cancer. Colon cancer patients with low expression of MARVELD1 had worse progression free survival and overall survival than those with high expression levels in our cohort. Hypermethylation and histone modification in the MARVELD1 promoter locus synergistically affected its expression in pan-cancer. The function of MARVELD1 in colon cancer remains to be studied. Gene Ontology enrichment analysis revealed that MARVELD1 may modulate processes associated with inhibition of tumorigenesis in colon cancer. Both upstream transcription factors and downstream functional enrichment of MARVELD1 were related to the Wnt/β-catenin signaling pathway. Overexpression of MARVELD1 inhibited the expression of β-catenin and its entry into the nucleus. MARVELD1 also inhibited the proliferation, migration, and invasion of colon cancer cells. With Wnt/β-catenin activator LiCl treatment, rescue experiments demonstrated that the role of MARVELD1 in colon cancer progression was dependent on the Wnt/β-catenin pathway. These results indicate that MARVELD1 acts as a tumor suppressor and inhibits tumorigenesis via the Wnt/β-catenin pathway.

CMTM5 inhibits the development of prostate cancer via the EGFR/PI3K/AKT signaling pathway

Prostate cancer (PCa) endangers the life and health of older men. Most PCa cases develop into castration-resistant PCa (CRPC) within 2 years. At present, the molecular mechanisms of the occurrence and development of PCa and its transformation to CRPC remain unknown. The present study aimed to investigate the role of CKLF-like Marvel transmembrane domain containing family member 5 (CMTM5) in PCa and its molecular mechanism in vitro. PCa tissues and paired adjacent normal prostate tissues from 70 patients were collected to examine the expression levels of CMTM5 and EGFR via immunohistochemistry, reverse transcription-quantitative PCR and western blotting. Then, CMTM5-overexpressing DU145 cells were constructed, and CMTM5 expression in these transfected cells and vector control cells was examined via western blotting. Cell Counting Kit-8 and plate clone formation assays were used to evaluate the proliferation and colony number of CMTM5-overexpressing cells and vector control cells. Then, cell migration and invasion were assessed using wound healing assay, Transwell assay and immunofluorescence analysis with DAPI staining. The effect of CMTM5 on apoptosis and its underlying molecular mechanism were examined using western blotting and flow cytometry. The results demonstrated that CMTM5 expression in PCa tissues and cell lines was significantly downregulated, while EFGR expression was significantly upregulated. The proportion of high CMTM5 expression in PCa tissues was significantly lower compared with that in normal prostate tissues. By contrast, the proportion of high EGFR expression in PCa tissues was significantly increased compared with that in normal prostate tissues. Moreover, CMTM5 overexpression significantly inhibited cell proliferation, migration and invasion, and promoted cell apoptosis compared with vector control cells in vitro. Furthermore, the regulation of PCa by CMTM5 was associated with the downregulation of PI3K/AKT and its downstream Bcl-2 expression, as well as the upregulation of Bax expression. In conclusion, CMTM5 may be an effective tumor suppressor gene for PCa, especially for castration-resistant PCa, by downregulating EGFR and PI3K/AKT signaling pathway components.

CMTM6, a potential immunotherapy target

The CKLF-like MARVEL transmembrane domain-containing protein 6 (CMTM6), which binds to the programmed death ligand 1 (PD-L1) and stabilizes the expression of PD-L1 on the cell surface, has been recently discovered as a novel regulator of PD-L1 expression in cancer. PD-L1 is an immune checkpoint inhibitory molecule that can mediate the immune escape of tumor cells in various tumors and has been studied intensively in recent years. In 2017, two articles simultaneously reported that CMTM6 can stabilize the expression of PD-L1 on the plasma membrane and prevent PD-L1 from being degraded by lysosomes; therefore, CMTM6 may play an important role in tumor cell immune escape and immunosuppression. At present, there are few studies on the relationship between the expression of CMTM6 and PD-L1 in different tumors and diseases. These studies together suggested that CMTM6 may be a potential novel immunotherapy target. In this review, we briefly describe the latest research progresses of CMTM6 in various cancers and other diseases.

Early and late stage MPN patients show distinct gene expression profiles in CD34+ cells

Myeloproliferative neoplasms (MPN), comprising essential thrombocythemia (ET), polycythemia vera (PV), and primary myelofibrosis (PMF), are hematological disorders of the myeloid lineage characterized by hyperproliferation of mature blood cells. The prediction of the clinical course and progression remains difficult and new therapeutic modalities are required. We conducted a CD34⁺ gene expression study to identify signatures and potential biomarkers in the different MPN subtypes with the aim to improve treatment and prevent the transformation from the rather benign chronic state to a more malignant aggressive state. We report here on a systematic gene expression analysis (GEA) of CD34⁺ peripheral blood or bone marrow cells derived from 30 patients with MPN including all subtypes (ET (n = 6), PV (n = 11), PMF (n = 9), secondary MF (SMF; post-ET-/post-PV-MF; n = 4)) and six healthy donors. GEA revealed a variety of differentially regulated genes in the different MPN subtypes vs. controls, with a higher number in PMF/SMF (200/272 genes) than in ET/PV (132/121). PROGENγ analysis revealed significant induction of TNFα/NF-κB signaling (particularly in SMF) and reduction of estrogen signaling (PMF and SMF). Consistently, inflammatory GO terms were enriched in PMF/SMF, whereas RNA splicing–associated biological processes were downregulated in PMF. Differentially regulated genes that might be utilized as diagnostic/prognostic markers were identified, such as AREG, CYBB, DNTT, TIMD4, VCAM1, and S100 family members (S100A4/8/9/10/12). Additionally, 98 genes (including CLEC1B, CMTM5, CXCL8, DACH1, and RADX) were deregulated solely in SMF and may be used to predict progression from early to late stage MPN.

CMTM7 as a novel molecule of ATG14L-Beclin1-VPS34 complex enhances autophagy by Rab5 to regulate tumorigenicity

Background

CMTM7 is a tumor suppressor that positively regulates EGFR degradation by promoting Rab5 activation, and plays a vital role in tumor progression. Rab5 forms complexes with Beclin1 and VPS34, and acts in the early stage of autophagy. However, the affects of CMTM7 on autophagy and its mechanism are still unclear.

Methods

The effect of CMTM7 on autophagy induction was confirmed by western blotting, confocal microscopy and transmission electron microscopy. Co-immunoprecipitation was used to analyse the interaction of CMTM7 with autophagy initiation complex and Rab5. The xenograft model in nude mice was used to elucidate the function of CMTM7 in tumorigenicity and autophagy in vivo.

Results

In this study, we first demonstrated that CMTM7 facilitated the initiation of autophagosome formation, which consequently promoted the subsequent multistage process of autophagic flux, i.e. from autophagosome assembly till autolysosome formation and degradation. Confocal and co-immunoprecipitation showed that CMTM7 interacted with Rab5, VPS34, Beclin1, and ATG14L, but not with ULK1, UVRAG and LC3B. CMTM7 also increased the activity of ATG14L-linked VPS34 complex and its association with Rab5. Both in vitro and in vivo experiments demonstrated that knockdown of CMTM7 enhanced tumor growth by impairing autophagy.

Conclusion

These findings highlighted the role of CMTM7 in the regulation of autophagy and tumorigenicity, revealing it as a novel molecule that is associated with the interaction of Rab5 and ATG14L-Beclin1-VPS34 complex.

CMTM5/7 are biomarkers and prognostic factors in human breast carcinoma

BACKGROUND

The CKLF-like MARVEL transmembrane domain-containing family (CMTM) is the protein product of at least one splice variant of each gene contained a Marvel (MAL and related proteins for vesicle trafficking and membrane link) domain, involved in a variety of cellular processes and the pathogenesis of diseases, including tumorigenesis. However, the diverse expression patterns and prognostic values of eight CMTMs have yet to be elucidated.

OBJECTIVE

We analyzed the expressions and impacts on survival of different CMTM factors in BC patients to determine their potential diagnosis and prognosis values in BC.

METHODS

In the current study, we examined the transcriptional and survival data of CMTMs in patients with breast carcinoma (BC) from ONCOMINE, GEPIA, Kaplan-Meier Plotter, and cBioPortal databases.

RESULTS

It was found that CMTM5/7 were down-regulated, whereas CMTM1/6 were up-regulated in BC patients compared with the normal tissues. In survival analyses through the Kaplan-Meier plotter database, increased mRNA expressions of CMTM5/6/7 and decreased mRNA expression of CMTM4 were associated with better relapse-free survival (RFS) of BC patients.

CONCLUSIONS

These data provided CMTM5/7 as new biomarker and prognostic factors in BC.

CMTM4 regulates epithelial-mesenchymal transition and PD-L1 expression in head and neck squamous cell carcinoma

The epithelial-mesenchymal transition (EMT) is a pivotal step involved in cancer recurrence and metastasis. In addition, the activation of the EMT program can induce a cancer stem cell (CSC)-like phenotype and programmed death-ligand 1 (PD-L1) expression in head and neck squamous cell carcinoma (HNSCC). The CMTM family has reported as an important regulator in this process. Here, we investigated the role of CMTM4 in HNSCC. We indicated that CMTM4 was overexpressed in human and mouse HNSCC samples and in HNSCC cell lines by immunohistochemistry and Western blot. A high expression level of CMTM4 was correlated with advanced lymph node metastasis and a negative prognosis. CMTM4-knockdown by small interfering RNA downregulated the EMT process and inhibited the migration and invasion abilities of tumor cells. Moreover, knockdown of CMTM4 decreased CSC-associated markers via the protein kinase B pathway. Notably, CMTM4-knockdown inhibited the expression of interferon-γ induced PD-L1 in HNSCC cells. A positive correlation was found between CMTM4 expression and CD8⁺ and PD-1⁺ cell density in the stroma. Our findings indicated that CMTM4 may play an important role in regulating EMT/CSC phenotypes and PD-L1 expression. This study may reinforce the interest in CMTM4 as a potential target for the prognosis and treatment of HNSCC.

Comprehensive analysis of the prognostic value of the chemokine-like factor-like MARVEL transmembrane domain-containing family in gastric cancer

Background

The chemokine-like factor (CKLF)-like MARVEL transmembrane domain-containing (CMTM) family refers to a family of transcriptional repressor genes. CMTMs are closely associated with the epigenetic regulatory mechanisms and development of multiple malignancies, including gastric cancer. However, their specific biological functions and prognostic values in gastric cancer have yet to be elucidated.

Methods

Tumor sample datasets were retrieved and analyzed using databases including Oncomine, STRING, GEPIA2, cBioportal, and Kaplan-Meier plotter. To investigate the prognostic role of CMTMs in gastric cancer, we applied unsupervised hierarchical clustering analysis of CMTM gene expression patterns.

Results

While the mRNA levels of CMTM1/3/6/7/8 were upregulated in gastric cancer, CMTM2/4/5 showed no statistically significant difference at the mRNA level in patients with gastric cancer. Moreover, the mRNA expressions of different CMTMs exhibited strong correlations with various clinical parameters of patients with gastric cancer, including tumor stage, metastatic lymph node status, H. pylori status, and tumor grade. Also, the results suggested that elevated levels of CMTM3/5 mRNA had a significant association (P<0.05) with poor overall survival, progression-free survival, and post-progression survival. Conversely, elevated expression of CMTM2/4/6 mRNA had a significant association with better overall survival, progression-free survival, and post-progression survival. Unsupervised hierarchical clustering analysis successfully identified 2 major clusters of patients as follows: signature #1: CMTM4/6/8 and signature #2: CMTM1/2/3/5/7. Signature #2 was closely correlated with poorer overall survival, which indicated that the expression pattern of the CMTM family could be a novel prognostic factor for patients with gastric cancer.

Conclusions

These results suggest that the expression levels of CMTM genes possibly have prognostic value as a biomarker of gastric cancer.

Chemokine-Like Factor-Like MARVEL Transmembrane Domain-Containing Family in Hepatocellular Carcinoma: Latest Advances

Chemokine-like factor (CKLF)-like MARVEL transmembrane domain-containing family (CMTMs) is a new gene family, consisting of CKLF and CMTM1 to CMTM8, which plays an important role in hematopoiesis system, autoimmune diseases, male reproduction etc. Abnormal expression of CMTMs is also associated with tumor genesis, development and metastasis. In this review, we briefly describe the characteristics of CMTM family, outline its functions in multiple kinds of carcinomas, and summarize the latest research on their roles in hepatocellular carcinoma which are mainly related to the expression, prognostic effect, potential functions, and mechanism of action. The CMTM family is expected to provide new ideas and targets for HCC diagnosis and treatment.

Chemokine-like factor 1: A promising therapeutic target in human diseases

IMPACT STATEMENT

CKLF1, a recently identified chemokine, has been reported by a number of studies to play important roles in quite many diseases. However, the potential pathways that CKLF1 may be involved are not manifested well yet. In our review, we showed the basic molecular structure and major functions of this novel chemokine, and implication in human diseases, such as tumors. To attract more attention, we summarized its signaling pathways and clearly present them in a set of figures. With the overview of the experimental trial of CKLF1-targeting medicines in animal models, we hope to provide a few important insights about CKLF1 to both medical researchers and pharmacy.

CMTM5-v1 inhibits cell proliferation and migration by downregulating oncogenic EGFR signaling in prostate cancer cells

Anomalous epidermal growth factor receptor (EGFR) signaling plays an important role in the progression of prostate cancer (PCa) and the transformation to castration-resistant PCa (CRPC). A novel tumor suppressor CKLF-like MARVEL transmembrane domain-containing member 5(CMTM5) has a MARVEL domain and may regulate transmembrane signaling. Thus, we postulated that CMTM5 could regulate EGFR and its downstream molecules to affect the biological behaviors of PCa cells. In this study, we found that CMTM5 was expressed in benign prostatic hyperplasia (BPH) tissues but was undetectable in PCa cells. However, the EGFR was upregulated in PCa cells, especially in two metastatic CRPC cell lines, PC3 and DU145. Furthermore, ectopic expression of CMTM5-v1 suppressed cell proliferation and migration and p-EGFR levels. Further investigation revealed that restoration of CMTM5-v1 inhibited not only EGF-mediated proliferation but also chemotactic migration by EGF in PC3 and DU145 cells. Moreover, mechanistic studies showed that CMTM5-v1 attenuated EGF-induced receptor signaling by repressing EGFR and Akt phosphorylation in PCa cells, which were essential for malignant features. Finally, CMTM5-v1can promote the sensitivity of PC3 cells to Gefetinib, a tyrosine kinase inhibitor (TKI) targeting the EGFR. These observations indicate that CMTM5-v1 suppressed PCa cells through EGFR signaling. The loss of CMTM5 may participate in the progression of PCa resulting from deregulated EGFR, and CMTM5 might be associated with the efficacy of TKIs in terms of their potent inhibition of EGFR and human epidermal growth factor-2 (HER2) activation.

Bioinformatics-Based Discovery of CKLF-Like MARVEL Transmembrane Member 5 as a Novel Biomarker for Breast Cancer

Chemokine-like factor (CKLF)-like MARVEL transmembrane members (CMTMs) represent a novel protein family linking the chemokine and transmembrane-4 superfamily families, which potentially play several roles in diverse physiological and pathological processes. The detailed functions and underlying molecular mechanisms of CMTMs remain elusive in breast cancer. Herein, we performed a comprehensive bioinformatic analysis to investigate the prognostic effect, potential functions, and biomolecular regulatory network of CMTMs in breast cancer. The mRNA expression level of CMTM5, in particular, was significantly downregulated in breast cancer; moreover, high mRNA expression level of CMTM5 was significantly associated with better relapse-free survival. DNA promoter hypermethylation of CMTM5 was negatively correlated with its mRNA expression levels. Furthermore, CMTM5 strongly associated with pathway in MARVEL domains, chemotaxis, cytokines, transmembrane structures, and integral component of membrane. For example, genes related to MARVEL domains, transmembrane structures, and chemokines were significantly enriched. Our findings indicate that CMTM5 can be used as a prognostic biomarker and potential therapeutic target for breast cancer.

CMTM family proteins 1-8: roles in cancer biological processes and potential clinical value

The CKLF-like MARVEL transmembrane domain containing (CMTM) family of genes comprises CKLF and CMTM1–8 (previously called chemokine-like factor superfamily 1–8, CKLFSF1–8). The CMTM family proteins contain a structurally conserved MAL and related proteins for vesicle trafficking and membrane linking (MARVEL) domain. Dysregulated expression of multiple CMTM family members is a common feature in many human cancer types. CMTM proteins control critical biological processes in cancer development, including growth factor receptor activation and recycling, cell proliferation, apoptosis, metastasis, and immune evasion. Emerging in vivo and in vitro evidence indicates that the mechanisms of action of most CMTM proteins are complex and multifactorial. This review highlights new findings regarding the roles of CMTM1–8 in cancer, particularly in tumor growth, metastasis, and immune evasion. Additionally, the potential clinical value of CMTMs as novel drug targets or biomarkers is discussed.

Research Advances in CKLF-like MARVEL Transmembrane Domain-containing Family in Non-small Cell Lung Cancer

CKLF-like MARVEL transmembrane domain-containing member (CMTM) is a new gene family first cloned and reported in 2001. The CMTM family consists of nine members including CKLF and CMTM1-CMTM8, which are located on different chromosomes. Besides exhibiting extensive chemotactic activity, the CMTM family plays an important role in the hematopoiesis system, the immune system, the cardiovascular system and the male reproductive system. Recent in-depth research has also revealed that CMTM is closely associated with the genesis, development and metastasis of tumors, displaying opposing activities in diverse human tumors. In this review, we discuss the structural and functional characteristics of the CMTM family and summarize latest research findings of the relationship between several CMTM members and non-small cell lung cancer.

Integrated Analyses of Phenotype and Quantitative Proteome of CMTM4 Deficient Mice Reveal Its Association with Male Fertility

The chemokine-like factor (CKLF)-like MARVEL transmembrane domain-containing family (CMTM) is a gene family that has been implicated in male reproduction. CMTM4 is an evolutionarily conserved member that is highly expressed in the testis. However, its function in male fertility remains unknown. Here, we demonstrate that CMTM4 is associated with spermatogenesis and sperm quality. Using Western blotting and immunohistochemical analyses, we found CMTM4 expression to be decreased in poor-quality human spermatozoa, old human testes, and testicular biopsies with nonobstructive azoospermia. Using CRISPR-Cas9 technology, we knocked out the Cmtm4 gene in mice. These Cmtm4 knockout (KO) mice showed reduced testicular daily sperm production, lower epididymal sperm motility and increased proportion of abnormally backward-curved sperm heads and bent sperm midpieces. These mice also had an evident sub-fertile phenotype, characterized by low pregnancy rates on prolonged breeding with wild type female mice, reduced in vitro fertilization efficiency and a reduced percentage of acrosome reactions. We then performed quantitative proteomic analysis of the testes, where we identified 139 proteins to be downregulated in Cmtm4-KO mice, 100 (71.9%) of which were related to sperm motility and acrosome reaction. The same proteomic analysis was performed on sperm, where we identified 3588 proteins with 409 being differentially regulated in Cmtm4-KO mice. Our enrichment analysis showed that upregulated proteins were enriched with nucleosomal DNA binding functions and the downregulated proteins were enriched with actin binding functions. These findings elucidate the roles of CMTM4 in male fertility and demonstrates its potential as a promising molecular candidate for sperm quality assessment and the diagnosis or treatment of male infertility.

Overexpression of CMTM7 inhibits cell growth and migration in liver cancer

Chemokine-like factor (CKLF)-like, MAL and related proteins for vesicle trafficking and membrane link (MARVEL) transmembrane domain-containing family proteins (CMTMs) have significant roles in the immune system, in male reproduction, as well as in tumorigenesis. Previous studies have shown that CMTM family member 7 (CMTM7) was broadly expressed in various normal tissues, but not in lung, gastric, esophageal, pancreas, and cervix cancers. To explore its relationship with liver cancer, we examined the expression of CMTM7 in liver cancers and its correlation with clinical and pathological conditions. We found that CMTM7 expression was markedly reduced in liver cancer tissues, and negatively correlated with TNM staging and tumor metastasis. In vitro studies showed that enforced expression of CMTM7 inhibited the cell growth and migration of liver cancer cells. Further analysis revealed that CMTM7 suppressed AKT signaling and induced cell cycle arrest at the G0/G1 phase in the liver cancer cells, likely as the consequent of decreased levels of cyclin D1, cyclin-dependent kinase 4 (CDK4), and CDK6, and increased p27 expression. Thus, CMTM7 functions as a tumor suppressor in liver cancer through suppressing cell cycle progression.

Association Between Polymorphisms in CMTM Family Genes and Hepatocellular Carcinoma in Guangxi of China

Polymorphisms in genes may affect its expression and alter individual susceptibility to cancer. In this study, we investigate associations between CMTM family gene polymorphisms and hepatocellular carcinoma (HCC) in a southern Chinese population. Ten selected single-nucleotide polymorphisms (SNPs) in CMTM family genes were genotyped in 315 HCC patients and 315 cancer-free controls using Sequenom MassARRAY platform and the associations of the selected SNPs with HCC risk were evaluated. We found individuals with the rs164207 AA genotypes had a significantly increased risk of HCC than those with CC genotypes (adjusted OR = 2.794, 95% CI = 1.143-6.828). Also, individuals with the rs3811178 GG genotypes showed a significant association with increased risk of HCC when compared with the AA genotypes (adjusted OR = 2.578, 95% CI = 1.114-5.969). Furthermore, there was also a significantly increased risk of HCC when combined risk genotypes of these loci, i.e., rs164207 AA, CA and rs3811178 GG, GA. Compared with the low-risk group (0 risk genotypes), the high-risk group (2 risk genotypes) was at significantly increased risk of HCC (adjusted OR = 3.339, 95% CI = 1.119-9.964, p = 0.031). Our results suggest that polymorphisms of rs3811178 in CMTM5 and rs164207 in CMTM6 might contribute to the genetic susceptibility of HCC in the southern Chinese population. Further well-designed studies with larger sample sizes are needed to confirm our findings.

Up-regulation of miR-10b-3p promotes the progression of hepatocellular carcinoma cells via targeting CMTM5

In this study, we investigated how miR‐10b‐3p regulated the proliferation, migration, invasion in hepatocellular carcinoma (HCC) at both in vitro and in vivo levels. CMTM5 was among the differentially expressed genes (data from TCGA). The expression of miR‐10b‐3p and CMTM5 was detected by qRT‐PCR and Western blot (WB). TargetScan was used to acquire the binding sites. Dual‐luciferase reporter gene assay was used to verify the direct target relationship between miR‐10b‐3p and CMTM5. WB analysis proved that miR‐10b‐3p suppressed CMTM5 expression. Furthermore, proliferation, invasion and migration of HCC cells were measured by MTT assay, colony formation assay, transwell assay and wound‐healing assay, respectively. Kaplan‐Meier plotter valued the overall survival of CMTM5. Finally, xenograft assay was also conducted to verify the effects of miR‐10b‐3p/CMTM5 axis in vivo. Up‐regulation of miR‐10b‐3p and down‐regulation of CMTM5 were detected in HCC tissues and cell lines. CMTM5 was verified as a target gene of miR‐10b‐3p. The overexpression of CMTM5 contributed to the suppression of the proliferative, migratory and invasive abilities of HCC cells. Moreover, the up‐regulation of miR‐10b‐3p and down‐regulation of CMTM5 were observed to be associated with worse overall survival. Lastly, we have confirmed the carcinogenesis‐related roles of miR‐10b‐3p and CMTM5 in vivo. We concluded that the up‐regulation of miR‐10b‐3p promoted the progression of HCC cells via targeting CMTM5.

CMTM5 is downregulated and suppresses tumour growth in hepatocellular carcinoma through regulating PI3K-AKT signalling

Background

Human chemokine like factor (CKLF)-like MAL and related proteins for vesicle trafficking transmembrane, domain-containing member 5 (CMTM5) has been shown to involved and may function as a tumour suppressor in tumorigenesis. The current study aimed to investigate the expression and function of CMTM5 in human hepatocellular carcinoma (HCC).

Methods

CMTM5 expression was examined by immunohistochemistry, and its clinical significance was analysed in 76 HCC specimens. The role and molecular mechanisms of CMTM5 in cell proliferation, apoptosis and invasion were examined in vitro and in vivo.

Results

CMTM5 expression was significantly downregulated in HCC tissues as well as cell lines. The expression of CMTM5 was absent in 77.6% of HCC tissues compared with 3.9% in normal liver tissues. Low CMTM5 expression was significantly correlated with poor overall survival in patients with HCC (P = 0.009). Restoring CMTM5 expression in Huh7 cells significantly inhibited cell growth, promoted cell apoptosis, and reduced cell metastatic and invasion ability compared with mock transfected cells in vitro. Overexpression of CMTM5 also suppressed xenograft tumour growth in vivo in a HCC xenograft model. Reduced cell growth and metastasis ability mediated by CMTM5 overexpression was associated with downregulation of PI3K/AKT and its downstream Bcl2, cyclinD1, cyclinE, MMP2 and MMP9 expressions, and an upregulation of p21, Bax, Bad, cleaved caspase3 expressions.

Conclusions

Our data suggest that CMTM5 might function as a tumour suppressor in human HCC, and represent a valuable potential therapeutic target for HCC.

Electronic supplementary material

The online version of this article (10.1186/s12935-017-0485-8) contains supplementary material, which is available to authorized users.

CMTM5 inhibits renal cancer cell growth through inducing cell-cycle arrest and apoptosis

CKLF-like MARVEL transmembrane domain-containing 5 (CMTM5) has been reported to function as a potential tumor suppressor in several human cancers. However, the involvement of CMTM5 in human renal cell carcinoma (RCC) remains unclear. The current study aimed to detect its expression pattern in RCC tissues and cells, and to determine its anti-proliferative functions in this malignancy. The mRNA and protein expression levels of CMTM5 in RCC tissues and cells were detected by reverse transcription-quantitative polymerase chain reaction, immunohistochemistry and western blotting. Following the transfection with CMTM5 lentivirus or control lenti-EGFP lentivirus into the RCC cell line ACHN, the viability, migration, apoptosis and cell cycle of these cells were detected by Cell Counting kit-8 assay, Transwell assay and flow cytometry, respectively. Compared with the adjacent non-malignant kidney tissue samples, CMTM5 expression was significantly downregulated in RCC tissues (P<0.05). In addition, enforced expression of CMTM5 could efficiently inhibit the cell growth of ACHN cells, which were arrested in G0/G1 phase. Furthermore, the migration and invasion of ACHN cells were also inhibited by restoration of CMTM5 expression. The present data suggest that CMTM5 may function as a tumor suppressor in human RCC by suppressing the viability of RCC cells, implying its potential as a therapeutic target for this malignancy.

Chemokine-like factor-like MARVEL transmembrane domain-containing 3 expression is associated with a favorable prognosis in esophageal squamous cell carcinoma

Decreased expression of human chemokine-like factor-like MARVEL transmembrane domain-containing 3 (CMTM3) has been identified in a number of human tumors and tumor cell lines, including gastric and testicular cancer, and PC3, CAL27 and Tca-83 cell lines. However, the association between CMTM3 expression and the clinicopathological features and prognosis of esophageal squamous cell carcinoma (ESCC) patients remains unclear. The aim of the present study was to investigate the correlation between CMTM3 expression and clinicopathological parameters and prognosis in ESCC. CMTM3 mRNA and protein expression was analyzed in ESCC and paired non-tumor tissues by quantitative real-time polymerase chain reaction, western blotting and immunohistochemical analysis. The Kaplan-Meier method was used to plot survival curves and the Cox proportional hazards regression model was also used for univariate and multivariate survival analysis. The results revealed that CMTM3 mRNA and protein expression levels were lower in 82.5% (30/40) and 75% (30/40) of ESCC tissues, respectively, when compared with matched non-tumor tissues. Statistical analysis demonstrated that CMTM3 expression was significantly correlated with lymph node metastasis (P=0.002) and clinical stage (P<0.001) in ESCC tissues. Furthermore, the survival time of ESCC patients exhibiting low CMTM3 expression was significantly shorter than that of ESCC patients exhibiting high CMTM3 expression (P=0.01). In addition, Kaplan-Meier survival analysis revealed that the overall survival time of patients exhibiting low CMTM3 expression was significantly decreased compared with patients exhibiting high CMTM3 expression (P=0.010). Cox multivariate analysis indicated that CMTM3 protein expression was an independent prognostic predictor for ESCC after resection. This study indicated that CMTM3 expression is significantly decreased in ESCC tissues and CMTM3 protein expression in resected tumors may present an effective prognostic biomarker.

CMTM7 knockdown increases tumorigenicity of human non-small cell lung cancer cells and EGFR-AKT signaling by reducing Rab5 activation

The dysregulation of epidermal growth factor receptor (EGFR) signaling has been well documented to contribute to the progression of non-small cell lung cancer (NSCLC), the leading cause of cancer death in the world. EGF-stimulated EGFR activation induces receptor internalization and degradation, which plays an important role in EGFR signaling. This process is frequently deregulated in cancer cells, leading to enhanced EGFR levels and signaling. Our previous study on CMTM7 is only limited to a brief description of the relationship of overexpressed CMTM7 with EGFR-AKT signaling. The biological functions of endogenous CMTM7 and its molecular mechanism remained unclear. In this study, we show that the stable knockdown of CMTM7 augments the malignant potential of NSCLC cells and enhances EGFR-AKT signaling by decreasing EGFR internalization and degradation. Mechanistically, CMTM7 knockdown reduces the activation of Rab5, a protein known to be required for early endosome fusion. In NSCLC, the loss of CMTM7 would therefore serve to sustain aberrant EGFR-mediated oncogenic signaling. Together, our findings highlight the role of CMTM7 in the regulation of EGFR signaling in tumor cells, revealing CMTM7 as a novel molecule related to Rab5 activation.

Biological implications and therapeutic significance of DNA methylation regulated genes in cervical cancer

Cervical cancer is the second most common cancer among women worldwide. About 528,000 women are diagnosed with cervical cancer contributing to around 266,000 deaths, across the globe every year. Out of these, the burden of 226,000 (85%) deaths occurs in the developing countries, who are less resource intensive to manage the disease. This is despite the fact that cervical cancer is amenable for early detection due to its long and relatively well-known natural history prior to its culmination as invasive disease. Infection with high risk human papillomavirus (hrHPVs) is essential but not sufficient to cause cervical cancer. Although it was thought that genetic mutations alone was sufficient to cause cervical cancer, the current epidemiological and molecular studies have shown that HPV infection along with genetic and epigenetic changes are frequently associated and essential for initiation, development and progression of the disease. Moreover, aberrant DNA methylation in host and HPV genome can be utilized not only as biomarkers for early detection, disease progression, diagnosis and prognosis of cervical cancer but also to design effective therapeutic strategies. In this review, we focus on recent studies on DNA methylation changes in cervical cancer and their potential role as biomarkers for early diagnosis, prognosis and targeted therapy.

CMTM4 is frequently downregulated and functions as a tumour suppressor in clear cell renal cell carcinoma

BACKGROUND

Chemokine-like factor (CKLF)-like MARVEL transmembrane domain-containing family (CMTM) is a gene family involved in multiple malignancies. CMTM4 is a member of this family and is located at chromosome 16q22.1, a locus that harbours a number of tumour suppressor genes. It has been defined as a regulator of cell cycle and division in HeLa cells; however, its roles in tumourigenesis remain poorly studied.

METHODS

An integrated bioinformatics analysis based on the array data from the GEO database was conducted to view the differential expression of CMTM4 across multiple cancers and their corresponding control tissues. Primary clear cell renal cell carcinoma (ccRCC) and the paired adjacent non-tumour tissues were then collected to examine the expression of CMTM4 by western blotting, immunohistochemistry, and quantitative RT-PCR. The ccRCC cell lines A498 and 786-O and the normal renal tubular epithelial cell line HK-2 were also tested for CMTM4 expression by western blotting. Cell Counting Kit-8 (CCK-8) and viable cell counting assays were used to delineate the growth curves of 786-O cells after CMTM4 overexpression or knockdown. Wound healing and transwell assays were performed to assess the cells' ability to migrate. The effects of CMTM4 on cellular apoptosis and cell cycle progression were analysed by flow cytometry, and cell cycle hallmarks were detected by western blotting and RT-PCR. The xenograft model in nude mice was used to elucidate the function of CMTM4 in tumourigenesis ex vivo.

RESULTS

By omic data analysis, we found a substantial downregulation of CMTM4 in ccRCC. Western blotting then confirmed that CMTM4 was dramatically reduced in 86.9 % (53/61) of ccRCC tissues compared with the paired adjacent non-tumour tissues, as well as in the 786-O and A498 ccRCC cell lines. Restoration of CMTM4 significantly suppressed 786-O cell growth by inducing G2/M cell cycle arrest and p21 upregulation, and cell migration was also inhibited. However, knockdown of CMTM4 led to a completely opposite effect on these cell behaviours. Overexpression of CMTM4 also markedly inhibited the tumour xenograft growth in nude mice.

CONCLUSIONS

CMTM4 is downregulated and exhibits tumour-suppressor activities in ccRCC, and could be exploited as a target for ccRCC treatment.

Novel roles and therapeutic targets of Epstein-Barr virus-encoded latent membrane protein 1-induced oncogenesis in nasopharyngeal carcinoma

Epstein-Barr virus (EBV) was first discovered 50 years ago as an oncogenic gamma-1 herpesvirus and infects more than 90% of the worldwide adult population. Nasopharyngeal carcinoma (NPC) poses a serious health problem in southern China and is one of the most common cancers among the Chinese. There is now strong evidence supporting a role for EBV in the pathogenesis of NPC. Latent membrane protein 1 (LMP1), a primary oncoprotein encoded by EBV, alters several functional and oncogenic properties, including transformation, cell death and survival in epithelial cells in NPC. LMP1 may increase protein modification, such as phosphorylation, and initiate aberrant signalling via derailed activation of host adaptor molecules and transcription factors. Here, we summarise the novel features of different domains of LMP1 and several new LMP1-mediated signalling pathways in NPC. When then focus on the potential roles of LMP1 in cancer stem cells, metabolism reprogramming, epigenetic modifications and therapy strategies in NPC.

Systematic investigation of CMTM family genes suggests relevance to glioblastoma pathogenesis and CMTM1 and CMTM3 as priority targets

The novel CKLF-like Marvel Transmembrane Domain-containing gene family (CMTM) consists of 8 members (CMTM1-8). As little is known about the oncogenic impact of these genes, we aimed to systematically investigate the relevance of CMTMs to glioblastoma pathogenesis. We performed mRNA expression analyses and survival correlations in glioblastoma patients. Moreover, we analyzed the impact of RNAi-based silencing and overexpression of CMTM family genes on tumor cell proliferation and invasion in vitro. CMTMs appeared to be widely regulated in the group of glioblastomas relative to non-neoplastic brain (NB) tissue (significant upregulation for CMTM2, 3, and 6 and significant downregulation for CMTM 4 and 8). For CMTM1, 5 and 7, we found aberrant expression levels in individual tumors. Functionally, CMTM1, 3, and 7 promoted tumor cell invasion, while CMTM1 additionally enhanced cell proliferation. In a large clinically annotated dataset, higher CMTM1 and 3 expression was significantly correlated with shorter overall survival. Our data thus suggest CMTM1 and 3 as priority targets in glioblastomas. Using a human phosphokinase protein expression profiling assay, we can provide first insights into signalling of these two genes that might be conveyed by growth factor receptor, Src family kinase and WNT activation.

CMTM5 is reduced in prostate cancer and inhibits cancer cell growth in vitro and in vivo

PURPOSE

A novel tumor suppressor CKLF-like MARVEL transmembrane domain-containing member 5 (CMTM5) is reduced or undetectable in many kinds of cancers and inhibits tumor cells' malignant features. To explore its role in prostate cancer (PCa), we detected its expression patterns in prostate tissues and PCa cells, and determined its anti-proliferation functions in PCa cells in vitro and in vivo.

METHODS

The expression of CMTM5 in prostate tissue microarray, specimens and cell lines was evaluated by immunohistochemistry and Western blot, respectively. After being transfected with CMTM5 adenovirus or vector, the proliferation and migration of DU145 cells were detected by MTT assay and transwell assay, respectively. Furthermore, the effects of CMTM5 on tumor growth were performed in nude mice xenograft in vivo.

RESULTS

We found CMTM5 was reduced in PCa tissues and cells compared with BPH tissues, and its expression in PCa tissues was related to the Gleason score. Moreover, after being transfected with adenovirus, ectopic expression of CMTM5-v1 in DU145 cells led to significant inhibition of cell proliferation and migration compared with the control, which may be attributed to decreased Akt activity. Finally, restoration of CMTM5 significantly suppressed tumor growth in vivo.

CONCLUSIONS

These results indicate that CMTM5 is down-regulated in PCa and exhibit tumor suppressor activities in androgen-independent PCa cells. Loss of CMTM5 protein may be contributed to the development of PCa and it is a potential therapeutic target for castration-resistant prostate cancer.

V‑set and transmembrane domain‑containing 1 is silenced in human hematopoietic malignancy cell lines with promoter methylation and has inhibitory effects on cell growth

Numerous leukocyte differentiation antigens act as important markers for research, diagnosis, triage and eventually treatment targets for hematopoietic malignancies. V‑set and transmembrane domain‑containing 1 (VSTM1) was identified by immunogenomic analysis as a potential leukocyte differentiation antigen gene. VSTM1 is located at 19q13.4 on human chromosomes, an important genomic region prone to genetic and epigenetic modifications in numerous hematopoietic malignancies. VSTM1‑v1, a primary splicing form encoded by VSTM1, is a type I transmembrane molecule with an extracellular immunoglobulin V‑like domain and two cytoplasmic immunoreceptor tyrosine-based inhibitory motifs. In the present study, VSTM1 expression was examined in normal human peripheral leukocytes and hematopoietic tumor cell lines; in addition, the aberrant methylation of the VSTM1 gene was evaluated using methylation‑specific polymerase chain reaction (MSP). The results of the present study demonstrated that VSTM1 was widely expressed in normal human peripheral blood leukocytes, including granulocytes and monocytes, in concurrence with previous studies, as well as lymphocytes; in addition, the molecular size and expression levels of VSTM1 varied considerably between leukocytes. However, VSTM1 was undetectable in numerous hematopoietic tumor cell lines following promoter hypermethylation. The effects of pharmacologically‑induced demethylation of the VSTM1 gene and promoter region were analyzed using MSP and biosulfite genomic sequencing, and the results revealed that VSTM1 expression was restored in methylation‑silenced Jurkat cells. In addition, CKK‑8 assays revealed that VSTM1‑v1 overexpression in Jurkat cells resulted in growth suppression. Furthermore, the inhibitory effect on cell growth was enhanced following antibody‑induced cross‑linking of VSTM1‑v1. In conclusion, the results of the present study indicated that promoter methylation silenced VSTM1 and negatively regulated cell growth in human hematopoietic malignancy cell lines.

CMTM3 inhibits human testicular cancer cell growth through inducing cell-cycle arrest and apoptosis

Human CMTM3 has been proposed as a putative tumor suppressor gene. The loss of CMTM3 has been found in several carcinomas. However, the regulation of CMTM3 expression and its function in tumor progression remain largely unknown. Here, we investigated the regulation of CMTM3 expression, function and molecular mechanism in human testicular cancer cells. CMTM3 was frequently downregulated or silenced in testicular cancer cell lines and tumor tissues but highly expressed in normal testis tissues. The re-expression of CMTM3 significantly suppressed the colony formation, proliferation, and migration capacity of testicular cancer cells by inducing a G2 cell cycle arrest and apoptosis. Moreover, the re-expression of CMTM3 activated the transcription of p53, induced p53 accumulation, up-regulated the expression of p21, and increased the cleavage of caspase 9, 8, 3, and PARP. The downregulation of CMTM3 in clinical tumor tissues was associated with the methylation of a single CpG site located within the Sp1/Sp3-responsive region of the core promoter. These results indicate that CMTM3 can function as tumor suppressor through the induction of a G2 cell cycle arrest and apoptosis. CMTM3 is thus involved in testicular cancer pathogenesis, and it is frequently at least partially silenced by the methylation of a single, specific CpG site in tumor tissues.

CMTM3 inhibits cell migration and invasion and correlates with favorable prognosis in gastric cancer

The CKLF-like MARVEL transmembrane domain containing 3 (CMTM3) gene is a novel tumor suppressor with frequent epigenetic inactivation. In this study, we showed the role played by CMTM3 in gastric cancer cells as a tumor suppressor gene, and examined the correlation between CMTM3 expression and clinicopathological parameters using immunohistochemistry in gastric cancer patients with different pathological stages (n = 350). We found that CMTM3 expression was reduced or silenced by epigenetic regulation in gastric cell lines, and dramatically downregulated in primary gastric cancer tissues. Restoration of CMTM3 significantly affected migration and invasion of AGS and SGC-7901 cells (P < 0.001). In vivo experiments showed that peritoneal disseminated metastases were significantly suppressed by CMTM3 (P < 0.001). We further showed that the expression of MMP2 and the phosphorylation of Erk1/2 were decreased when CMTM3 was restored. In addition, by immunohistochemical staining, we found that the expression of CMTM3 was remarkably weaker in gastric cancer tissues than in normal mucosae (P = 0.008), and was significantly correlated with gender (P = 0.033), tumor depth (P = 0.049), stage (P = 0.021), and histological grade (P = 0.022). More importantly, CMTM3 expression was associated with prognosis in gastric cancer patients (P = 0.041), and was a significant independent prognostic indicator (hazard ratio = 0.704, 95% confidence interval, 0.498–0.994; P = 0.046). Our findings indicate that CMTM3 regulates migration and invasion of gastric cancer cells. Moreover, CMTM3 is a candidate marker for prognosis of gastric cancer in the clinic.

CMTM3 is frequently reduced in clear cell renal cell carcinoma and exhibits tumor suppressor activities

PURPOSE

CKLF-like MARVEL transmembrane domain containing member 3 (CMTM3) is silenced in many kinds of cancers and inhibits tumor cells growth. We investigated the expression and role of CMTM3 in clear cell renal cell carcinoma (ccRCC).

METHODS

The expression of CMTM3 was detected in ccRCC tissue microarray, specimens, and cell lines by immunohistochemistry, quantitative real-time polymerase chain reaction (qRT-PCR) and western blot, respectively. After transfected with CMTM3 plasmid or vector, the proliferation and migration of ccRCC 786-0 cells were determined by MTT assay and transwell assay, respectively. Furthermore, the anchorage-independent growth of transfected cells was assessed using soft agar colony formation assay.

RESULTS

CMTM3 was down-regulated in 84 % (63/75) of ccRCC tissues and its expression had no correlation with the gender, age, clinical staging and histologic grade. CMTM3 protein was undetectable by western blot in most detected ccRCC specimens and two RCC cell lines (786-0 and ACHN). qRT-PCR analysis showed that CMTM3 mRNA was dramatically down-regulated in 40 ccRCC cancer tissues as compared with the paired adjacent normal ones. Restoration of CMTM3 significantly suppressed the anchorage-independent growth, proliferation and migration of 786-0 cells.

CONCLUSION

These results indicate that CMTM3 is significantly down-regulated in ccRCC and exerts remarkable tumor-suppressive functions in 786-0 cells. Reduction of CMTM3 expression may contribute to the pathogenesis of ccRCC and CMTM3 may be a potentially target for therapeutic strategy.

A novel 3p22.3 gene CMTM7 represses oncogenic EGFR signaling and inhibits cancer cell growth

Deletion of 3p12-22 is frequent in multiple cancer types, indicating the presence of critical tumor-suppressor genes (TSGs) at this region. We studied a novel candidate TSG, CMTM7, located at the 3p22.3 CMTM-gene cluster, for its tumor-suppressive functions and related mechanisms. The three CMTM genes, CMTM6, 7 and 8, are broadly expressed in human normal adult tissues and normal epithelial cell lines. Only CMTM7 is frequently silenced or downregulated in esophageal and nasopharyngeal cell lines, but uncommon in other carcinoma cell lines. Immunostaining of tissue microarrays for CMTM7 protein showed its downregulation or absence in esophageal, gastric, pancreatic, liver, lung and cervix tumor tissues. Promoter CpG methylation and loss of heterozygosity were both found contributing to CMTM7 downregulation. Ectopic expression of CMTM7 in carcinoma cells inhibits cell proliferation, motility and tumor formation in nude mice, but not in immortalized normal cells, suggesting a tumor inhibitory role of CMTM7. The tumor-suppressive function of CMTM7 is associated with its role in G1/S cell cycle arrest, through upregulating p27 and downregulating cyclin-dependent kinase 2 (CDK2) and 6 (CDK6). Moreover, CMTM7 could promote epidermal growth factor receptor (EGFR) internalization, and further suppress AKT signaling pathway. Thus, our findings suggest that CMTM7 is a novel 3p22 tumor suppressor regulating G1/S transition and EGFR/AKT signaling during tumor pathogenesis.

Inhibition of Ca(2+)-activated Cl(-) channel ANO1/TMEM16A expression suppresses tumor growth and invasiveness in human prostate carcinoma

The etiology of prostatic adenocarcinoma remains unclear. Prostate cancer cells of varying metastatic potential and apoptotic resistance show altered expression of plasma membrane ion channels and unbalanced Ca2+ homeostasis. Ca(2+)-activated Cl(-) channels (CaCCs) are robustly expressed in epithelial cells and function to regulate epithelial secretion and cell volume for maintenance of ion and tissue homeostasis in proliferation, differentiation and apoptosis. ANO1/TMEM16A was recently identified as a CaCC, and it is of interest to determine whether ANO1 plays a role in development and metastasis of prostate carcinoma. Here we show that ANO1 mRNA and protein are highly expressed in human metastatic prostate cancer LNCaP and PC-3 cells by quantitative analysis of real-time PCR and Western blot. These findings were confirmed by whole-cell patch clamp recording of LNCaP and PC-3 cells with increased current density of ANO1 channels. Immunohistochemistry staining further revealed overexpression of ANO1 in human prostate cancer tissues, which correlated with the clinical TNM stage and Gleason score. Experiments with small hairpin RNAs (shRNAs) targeting human ANO1 resulted in a significant reduction of proliferation, metastasis and invasion of PC-3 cells using WST-8, colony formation, wound-healing and transwell assays. Moreover, intratumoral injection of ANO1 shRNA completely inhibited established tumor growth and survival in orthotopic nude mice implanted with PC-3 cells. Our findings provide compelling evidence that upregulation of CaCC ANO1 is involved in the proliferation, progression and pathogenesis of metastatic prostate cancer. Membrane ANO1 protein may therefore serve as a biomarker, and inhibition of overexpressed ANO1 has potential for use in prostate cancer therapy.

Promoter methylation of tumor suppressor genes in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is a prevalent and fatal cancer in China and other Asian countries. Epigenetic silencing of key tumor suppressor genes (TSGs) is critical to ESCC initiation and progression. Recently, many novel TSGs silenced by promoter methylation have been identified in ESCC, and these genes further serve as potential tumor markers for high-risk group stratification, early detection, and prognosis prediction. This review summarizes recent discoveries on aberrant promoter methylation of TSGs in ESCC, providing better understanding of the role of disrupted epigenetic regulation in tumorigenesis and insight into diagnostic and prognostic biomarkers for this malignancy.