Autophagy-related CMTM6 promotes glioblastoma progression by activating Wnt/ß-catenin pathway and acts as an onco-immunological biomarker.

BACKGROUND: Glioblastoma multiforme (GBM) is identified as one of the most prevalent and malignant brain tumors, characterized by poor treatment outcomes and a limited prognosis. CMTM6, a membrane protein, has been found to upregulate the expression of programmed cell death 1 ligand 1 protein (PD-L1) and acts as an immune checkpoint inhibitor by inhibiting the programmed death 1 protein/PD-L1 signaling pathway. Recent research has demonstrated a high expression of CMTM6 in GBM, suggesting its potential role in influencing the pathogenesis and progression of GBM, as well as its association with immune cell infiltration in the tumor microenvironment. However, the underlying mechanism of CMTM6 in GBM requires further investigation. METHODS: Data from cancer patients in The Cancer Genome Atlas, Gene Expression Omnibus and Chinese Glioma Genome Atlas cohorts were consolidated for the current study. Through multi-omics analysis, the study systematically examined the expression profile of CMTM6, epigenetic modifications, prognostic significance, biological functions, potential mechanisms of action and alterations in the immune microenvironment. Additionally, the study investigated CMTM6 expression in GBM cell lines and normal cells using reverse transcription PCR and western blot analysis. The impact of CMTM6 on GBM cell proliferation, migration and invasion was evaluated using a combination of cell counting kit-8 assay, clone formation assay, 5-ethynyl-2'-deoxyuridine incorporation assay, wound healing assay and Transwell assay. In order to explore the mechanism of CMTM6, the Wnt/ß-catenin signaling pathway and autophagy-related genes were further verified through western blot analysis. RESULTS: CMTM6 is highly expressed in multiple tumors, particularly GBM. CMTM6 has been shown to be a valuable diagnostic and prognostic biomarker by various bioinformatics approaches. Additionally, CMTM6 plays a pivotal role in the pathogenesis of cancer, specifically GBM, by modulating various biological processes such as DNA methyltransferase expression, RNA modification, copy number variation, genomic heterogeneity, tumor stemness and DNA methylation. The findings of the experiment indicate a significant correlation between elevated CMTM6 expression and the proliferation, invasion, migration and autophagy of GBM cells, with potential key roles mediated through the Wnt/ß-catenin signaling pathway. Furthermore, CMTM6 is implicated in modulating tumor immune cell infiltration and is closely linked to the expression of various immune checkpoint inhibitors and immune modulators, particularly within the context of GBM. High levels of CMTM6 expression also enhance the responsiveness of GBM patients to radiotherapy and chemotherapy, thereby offering valuable insights for guiding treatment strategies for GBM. CONCLUSIONS: Autophagy-related CMTM6 is highly expressed in various types of cancer, especially GBM, and it can regulate GBM progression through the Wnt/ß-catenin signaling pathway and is capable of being used as an underlying target for the diagnosis, treatment selection and prognosis of patients with GBM.

Differential Expression of CKLF-like MARVEL Transmembrane Domain-Containing Protein 6 and Programmed Cell Death Ligand 1 as Prognostic Biomarkers in Upper Tract Urothelial Carcinoma.

Upper tract urothelial carcinoma (UTUC) accounts for 5-10% of all UCs. Immune checkpoint inhibitors (ICIs) have been established for UCs. The prognostic and predictive potential of programmed cell death ligand 1 (PD-L1) expression to stratify patients benefiting from ICIs is not fully understood, and additional markers influencing the impact of PD-L1-mediated ICI response are needed. Previously, the chemokine-like MARVEL transmembrane domain-containing protein 6 (CMTM6) was identified as a positive regulator of PD-L1. Our aim was to investigate the expression profiles and impact of PD-L1 and CMTM6 protein status on the prognostic parameters and survival of UTUC patients. In this retrospective study, the combined positive score (CPS), tumor proportion score (TPS), and immune cell score (ICS) for PD-L1 and CMTM6 were determined. High PD-L1 CPS, ICS, and TPS were found in 77.4%, 58.3%, and 45.2% of cases, and high CMTM6 CPS, ICS, and TPS were seen in 52.5%, 51.5%, and 55.5% of cases, respectively. The scores of both markers had a significant positive correlation. High PD-L1 and CMTM6 expression was coupled with higher pT status, WHO grade, necrosis, and metastasis (p < 0.05, respectively). In the univariate survival analysis, patients with a PD-L1 ICS high and higher degree of intratumoral inflammation showed significantly longer overall survival. Compared to other studies on UC, our study shows a substantially higher rate of PD-L1-positive tumors. CMTM6 was associated with more aggressive tumors.

Transmembrane Protein CMTM6 Alleviates Ocular Inflammatory Response and Improves Corneal Epithelial Barrier Function in Experimental Dry Eye.

Purpose: To investigate the impact of transmembrane protein CMTM6 on the pathogenesis of dry eye disease (DED) and elucidate its potential mechanisms. Methods: CMTM6 expression was confirmed by database analysis, real-time polymerase chain reaction (RT-PCR), western blot, and immunohistochemistry. Tear secretion was measured using the phenol red thread test. Immune cell infiltration was assessed through flow cytometry. Barrier function was evaluated by fluorescein sodium staining, immunofluorescence staining of zonula occludens 1 (ZO-1), and electric cell-substrate impedance sensing (ECIS) assessment. For silencing CMTM6 expression, siRNA and shRNA were employed, along with lentiviral vector-mediated overexpression of CMTM6. Proinflammatory cytokine levels were analyzed by RT-PCR and cytometric bead array (CBA) analysis. Results: CMTM6 showed high expression in healthy human and mouse corneal and conjunctival epithelium but was notably reduced in DED. Notably, this downregulation was correlated with disease severity. Cmtm6-/- dry eye (DE) mice displayed reduced tear secretion, severe corneal epithelial defects, decreased conjunctival goblet cell density, and upregulated inflammatory response. Additionally, Cmtm6-/- DE mice and CMTM6 knockdown human corneal epithelial cell-transformed (HCE-T) cells showed more severe barrier disruption and reduced expression of ZO-1. Knockdown of CMTM6 in HCE-T cells increased inflammatory responses induced by hyperosmotic stress, which was significantly mitigated by CMTM6 overexpression. Moreover, the level of phospho-p65 in hyperosmolarity-stimulated HCE-T cells increased after silencing CMTM6. Nuclear factor kappa B (NF-κB) p65 inhibition (JSH-23) reversed the excessive inflammatory responses caused by hyperosmolarity in CMTM6 knockdown HCE-T cells. Conclusions: The reduction in CMTM6 expression on the ocular surface contributes to the pathogenesis of DED. The CMTM6-NF-κB p65 signaling pathway may serve as a promising therapeutic target for DED.

The role of polyethylenimine-functionalized gold nanoclusters carrying plasmid CMTM5 in impeding the malignant progression of prostate cancer cells by promoting EGFR endocytosis.

In this research, polyethylenimine-functionalized gold nanoclusters (PEI-AuNCs) were synthesized for the delivery of plasmid CMTM5 (pCMTM5) to prostate cancer (PCa) cells, with the objective of elucidating the mechanism underlying its anticancer efficacy. The PEI-AuNCs loaded with pCMTM5 (PEI-AuNCs@pCMTM5) tumor-targeting drug delivery system was established. Subsequently, both the obtained PEI-AuNCs and PEI-AuNCs@pCMTM5 underwent characterization through a transmission electron microscope (TEM) and dynamic light scattering (DLS). Employing RT-qPCR, western blot, flow cytometry, immunofluorescence, and co-immunoprecipitation (co-IP) assays, the consequences of CMTM5 overexpression on the expression of EGFR were investigated. Moreover, the influence of PEI-AuNCs@pCMTM5 on PC-3 cells was assessed through CCK-8, wound healing assay, and Transwell experiments. As a result, the PEI-AuNCs and PEI-AuNCs@pCMTM5 were presented as uniformly dispersed spherical with stable particle sizes and positive charges, showcasing favorable dispersion within the solution. In comparison to Lip2000, the PEI-AuNCs demonstrated superior transfection efficiency and lower cellular toxicity. Following the overexpression of CMTM5, the proliferative capacity of PC-3 cells was markedly suppressed, while both migratory and invasive abilities exhibited noteworthy reduction, with the efficacy of PEI-AuNCs@pCMTM5 consistently outperforming that of free pCMTM5. Subsequent mechanistic investigations unveiled that CMTM5 does not directly inhibit the synthesis of EGFR or facilitate its degradation, but rather influences the endocytic process of EGFR. In conclusion, the PEI-AuNCs nano-delivery system exhibits good biocompatibility and efficaciously conveys pCMTM5 to PCa cells. Crucially, pCMTM5 does not directly interact with EGFR, and CMTM5 governs the malignant progression of PC3 cells by promoting EGFR endocytosis.

CMTM 6 promotes the development of thyroid cancer by inhibiting NIS activity through activating the MAPK signaling pathway.

Thyroid cancer is the most common type of endocrine cancer. Chemokine-like factor (CKLF)-like MARVEL transmembrane domain containing 6 (CMTM6) is recognized as one of its potential immunotherapy targets. The purpose of this study was to investigate the role and molecular mechanism of CMTM6 in regulating the development of thyroid cancer cells. In this study, expression levels of CMTM6 and the sodium/iodide symporter (NIS) were detected by qRT-PCR. Additionally, colony formation assay and flow cytometry were used to detect cell proliferation and apoptosis, while expression levels of various proteins were assessed using Western blotting. Further, the apoptosis and invasion capacity of cells were investigated by scratch and transwell experiments. Finally, the effect of CMTM6 on the epithelial-mesenchymal transition (EMT) of thyroid cancer cells was determined by immunofluorescence assay, which measured the expression levels of epithelial and mesenchymal phenotypic markers. The results of qRT-PCR experiments showed that CMTM6 was highly expressed in thyroid cancer tissues and cells. In addition, knockdown of CMTM6 expression significantly increased NIS expression. Function experiments demonstrated that small interfering (si)-CMTM6 treatment inhibited the proliferation, migration, invasion, and EMT of thyroid cancer cells, while promoting apoptosis of FTC133 cells. Furthermore, mechanistic studies showed that mitogen-activated protein kinase (MAPK) and extracellular signal-regulated kinase (ERK) phosphorylation were inhibited by si-CMTM6, as demonstrated by Western blot experiments. In conclusion, our findings demonstrated the role of CMTM6 in the metastasis of thyroid cancer. Briefly, CMTM6 exerts its tumor-promoting effect through the MAPK signaling pathway and could potentially be used as a valuable biomarker for thyroid cancer diagnosis and prognosis.

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.

Bioinformatics analysis of CMTM family in pan-cancer and preliminary exploration of CMTM6 in bladder cancer.

BACKGROUND: The chemokine-like factor (CKLF)-like Marvel transmembrane structural domain (CMTM) family is widely expressed in the tumor and immune systems and is essential in human cancer progression. However, the multi-omic profile of CMTM family genes and their role in tumor patient prognosis and immune microenvironment have not been explored. METHODS: We collected data from 33 cancers and 33 non-cancers and then comprehensively analyzed the basal expression levels of CMTM family genes in normal human tissues as well as abnormal expression in diseases, genomic alterations, diagnostic and prognostic roles, subcellular localization, pathway enrichment, the immune microenvironment, associations with immune checkpoints, and drug sensitivities as well as to predict the immunotherapeutic response of patients to ICIs and targeting of small molecule drugs, the above results were validated by immunohistochemical staining, pathology sections and experiments. We also performed protein docking of immune checkpoints binding to CMTM6 and screening of small molecule drugs targeting CMTM6 based on mass spectrometry results and molecular docking techniques. Finally, we experimentally confirmed the role of CMTM6 in bladder cancer. RESULTS: We found differential expression and diagnostic biomarker value of the CMTMs family in diseases (cancer and non-cancer). CMTMs were also found to play a key role in pan-cancer with the tumor microenvironment. CMTMs were closely associated with common immune checkpoints, TMB and MSI, so we scored CMTMs based on CMTMs expression in patients undergoing ICI, and patients with lower scores had better survival and showed higher immunotherapy response after immunotherapy. Finally, molecular docking was used to identify small molecule inhibitors that could target CMTM6 and binding poses of CMTM6 to other immune checkpoint genes. Finally, it was determined experimentally that knockdown of CMTM6 gene expression inhibited the proliferation and invasion of bladder cancer cells. CONCLUSIONS: Our findings provide a valuable strategy to guide the diagnostic and therapeutic direction of CMTM family genes in disease.

CMTM3 deficiency induces cardiac hypertrophy by regulating MAPK/ERK signaling.

OBJECTIVES: Cardiac hypertrophy is the heart's compensatory response stimulated by various pathophysiological factors. However, prolonged cardiac hypertrophy poses a significant risk of progression to heart failure, lethal arrhythmias, and even sudden cardiac death. For this reason, it is crucial to effectively prevent the occurrence and development of cardiac hypertrophy. CMTM is a superfamily of human chemotaxis, which is involved in immune response and tumorigenesis. CMTM3 expressed widely in tissues, including the heart, but its cardiac function remains unclear. This research aims to explore the effect and mechanism of CMTM3 in the development of cardiac hypertrophy. METHODS AND RESULTS: We generated a Cmtm3 knockout mouse model (Cmtm3-/-) as the loss-of-function approach. CMTM3 deficiency induced cardiac hypertrophy and further exacerbated hypertrophy and cardiac dysfunction stimulated by Angiotensin Ⅱ infusion. In Ang Ⅱ-infusion stimulated hypertrophic hearts and phenylephrine-induced hypertrophic neonatal cardiomyocytes, CMTM3 expression significantly increased. However, adenovirus-mediated overexpression of CMTM3 inhibited the hypertrophy of rat neonatal cardiomyocytes induced by PE stimulation. In terms of mechanism, RNA-seq data revealed that Cmtm3 knockout-induced cardiac hypertrophy was related to MAPK/ERK activation. In vitro, CMTM3 overexpression significantly inhibited the increased phosphorylation of p38 and ERK induced by PE stimulation. CONCLUSIONS: CMTM3 deficiency induces cardiac hypertrophy and aggravates hypertrophy and impaired cardiac function stimulated by angiotensin Ⅱ infusion. The expression of CMTM3 increases during cardiac hypertrophy, and the increased CMTM3 can inhibit further hypertrophy of cardiomyocytes by inhibiting MAPK signaling. Thus, CMTM3 plays a negative regulatory effect in the occurrence and development of cardiac hypertrophy.

CKLF as a Prognostic Biomarker and Its Association with Immune Infiltration in Hepatocellular Carcinoma.

The Chemokine-like factor (CKLF)-like MARVEL transmembrane domain-containing (CMTM) family, comprising nine members, is involved in the tumorigenesis and progression of various cancers. However, the expression profiles and clinical significance of CMTM family members in hepatocellular carcinoma (HCC) are not fully clarified. In this study, the RNA-sequencing and clinical data were downloaded from The Cancer Genome Atlas (TCGA) databases. The Kaplan-Meier method and the Cox proportional hazards regression analysis were used to evaluate the prognostic significance of CMTM family members. Single-sample gene set enrichment analysis (ssGSEA) and ESTIMATE algorithms were employed to explore the relationship between CMTM family genes and the tumor microenvironment in HCC. Finally, the prognostic CMTM family gene expression was further validated by quantitative real-time polymerase chain reaction (qRT-PCR) and immunohistochemical (IHC) staining in clinical HCC tissue specimens. The results indicated that, compared with normal tissues, the expression of CKLF, CMTM1, CMTM3, CMTM4, CMTM7, and CMTM8 were significantly upregulated in HCC, while the expression of CMTM2, CMTM5, and CMTM6 were significantly downregulated in HCC. Univariate and multivariate Cox regression analysis demonstrated that CKLF was an independent prognostic biomarker for the overall survival (OS) of HCC patients. In HCC, the expression of CKLF was found to be correlated with immune cell infiltration, immune-related functions, and immune checkpoint genes. The qRT-PCR and IHC confirmed that CKLF was highly expressed in HCC. Overall, this research suggested that CKLF is involved in immune cell infiltration and may serve as a critical prognostic biomarker, which provides new light on the therapeutics for HCC.

[Advances in the Study of Chemokine-like Factor Superfamily Members in Tumors].

Chemokine-like factor-like MARVEL transmembrane domain containing member/chemokine-like factor superfamily member (CMTM/CKLFSF) including CKLF and CMTM1-CMTM8 are a new family of proteins linking chemokines and transmembrane superfamilies. CMTM not only have broad chemotactic activities, but also associate with hematopoietic system, immune system, and tumor development and metastasis closely. CMTM proteins are involved in key biological processes of cancer development, which include activation and recycling of growth factor receptors, cell proliferation and metastasis, and regulation of the tumor immune microenvironment. This is a new focus of research on the relationship between CMTM and tumors, because CMTM4/CMTM6 can be considered as a regulator for programmed cell death ligand 1 (PD-L1). This paper reviews the role of CMTM family members on cancer, especially in tumor growth, metastasis and immune escape, summarize the latest findings on the relationship between CMTM and non-small cell lung cancer, and explores the potential clinical value of CMTM as a novel drug target or biomarker.
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CMTM7 inhibits breast cancer progression by regulating Wnt/ß-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/ß-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 (ß-catenin), and TCF3, which play essential roles in breast cancer progression. CONCLUSION: These findings reveal the emerging character of CMTM7 in Wnt/ß-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 overexpression confers trastuzumab resistance in HER2-positive breast cancer.

Human epidermal growth factor receptor 2-positive (HER2+) breast cancer is characterized by invasive growth, rapid metastasis and chemoresistance. Trastuzumab is an effective treatment for HER2+ breast cancer; however, trastuzumab resistance leads to cancer relapse and metastasis. CKLF-like MARVEL transmembrane domain-containing 6 (CMTM6) has been considered as a new immune checkpoint for tumor-induced immunosuppression. The role of CMTM6 in trastuzumab resistance remains unknown. Here, we uncover a role of CMTM6 in trastuzumab-resistant HER2+ breast cancer. CMTM6 expression was upregulated in trastuzumab-resistant HER2+ breast cancer cell. Patients with high CMTM6 expressing HER2+ breast cancer had worse overall and progression-free survival than those with low CMTM6 expression. In vitro, CMTM6 knockdown inhibited the proliferation and migration of HER2+ breast cancer cells, and promoted their apoptosis, while CMTM6 overexpression reversed these effects. CMTM6 and HER2 proteins were co-localized on the surface of breast cancer cells, and CMTM6 silencing reduced HER2 protein levels in breast cancer cells. Co-immunoprecipitation revealed that CMTM6 directly interacted with HER2 in HER2+ breast cancer cells, and CMTM6 overexpression inhibited HER2 ubiquitination. Collectively, these findings highlight that CMTM6 stabilizes HER2 protein, contributing to trastuzumab resistance and implicate CMTM6 as a potential prognostic marker and therapeutic target for overcoming trastuzumab resistance in HER2+ breast cancer.

CMTM4 is a subunit of the IL-17 receptor and mediates autoimmune pathology.

Interleukin-17A (IL-17A) is a key mediator of protective immunity to yeast and bacterial infections but also drives the pathogenesis of several autoimmune diseases, such as psoriasis or psoriatic arthritis. Here we show that the tetra-transmembrane protein CMTM4 is a subunit of the IL-17 receptor (IL-17R). CMTM4 constitutively associated with IL-17R subunit C to mediate its stability, glycosylation and plasma membrane localization. Both mouse and human cell lines deficient in CMTM4 were largely unresponsive to IL-17A, due to their inability to assemble the IL-17R signaling complex. Accordingly, CMTM4-deficient mice had a severe defect in the recruitment of immune cells following IL-17A administration and were largely resistant to experimental psoriasis, but not to experimental autoimmune encephalomyelitis. Collectively, our data identified CMTM4 as an essential component of IL-17R and a potential therapeutic target for treating IL-17-mediated autoimmune diseases.

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.

Prognostic significance and immune characteristics of CMTM4 in hepatocellular carcinoma.

BACKGROUND: Previous study has shown that chemokine-like factor (CKLF)-like MARVEL transmembrane domain-containing family member 4 (CMTM4) can bind and maintain programmed cell death ligand 1 (PD-L1) expression to promote tumor progression by alleviating the suppression of tumor-specific T cell activity, suggesting its potential role in tumor immunotherapy. However, the role of CMTM4 in tumor immunity has not been well clarified, especially in hepatocellular carcinoma (HCC). METHODS: The protein expression of CMTM4/PD-L1/CD4/CD8 was detected by immunohistochemistry (IHC) detection in 90 cases of HCC tissues. The mRNA expression profiles and related prognosis data were obtained from The Cancer Genome Atlas-Liver Hepatocellular Carcinoma (TCGA-LIHC). Two immune therapy cohorts were from Imvigor210 and GSE176307. RESULTS: Though the single protein expression of CMTM4, PD-L1, CD4 or CD8 in HCC tissues by IHC detection didn't show a significant relationship with the prognosis of HCC patients, we found that high co-expression of CMTM4/PD-L1/CD4 showed a good prognosis of HCC patients. Further Timer 2.0 analysis identified that HCC patients with high expression of CMTM4/PD-L1 and high infiltration of CD4+ T cells had a better overall survival than those with low infiltration of CD4+ T cells. Moreover, a series of bioinformatics analyses revealed that CMTM4-related genes posed important effects on prognosis and immunity in HCC patients, and CMTM4 had a positive correlation with infiltration of CD4+ and CD8+ T cells in HCC. At last, we used two immunotherapy cohorts to verify that the combination of CMTM4 with PD-L1 could improve the prognosis of tumor patients underwent immunotherapy. CONCLUSIONS: CMTM4 and PD-L1 co-expression with T cell infiltration shows prognostic significance in HCC, suggesting combined effect from multiple proteins should be considered in HCC treatment.

Exosomal miR-224-5p from Colorectal Cancer Cells Promotes Malignant Transformation of Human Normal Colon Epithelial Cells by Promoting Cell Proliferation through Downregulation of CMTM4.

Background: Interactions between malignant cells and neighboring normal cells are important for carcinogenesis. In addition, cancer cell-derived exosomes have been shown to promote the malignant transformation of recipient cells, but the mechanisms remain unclear. Methods: The level of miR-224-5p in CRC cell-derived exosomes was determined by RT-qPCR assay. In addition, PKH26 dye-labeled exosomes were used to assess the efficacy of the transfer of exosomes between SW620 and normal colon epithelial cell line CCD 841 CoN. Results: In this study, we found that overexpression of miR-224-5p significantly promoted the proliferation, migration, and invasion and inhibited the oxidative stress of SW620 cells. In addition, miR-224-5p can be transferred from SW620 cells to CCD 841 CoN cells via exosomes. SW620 cell-derived exosomal miR-224-5p markedly promoted proliferation, migration, and invasion of CCD 841 CoN cells. Meanwhile, SW620 cell-derived exosomal miR-224-5p notably decreased the expression of CMTM4 in CCD 841 CoN cells. Furthermore, SW620 cell-derived exosomal miR-224-5p significantly promoted tumor growth in a xenograft model in vivo. Conclusion: These findings suggested that SW620 cell-derived exosomal miR-224-5p could promote malignant transformation and tumorigenesis in vitro and in vivo via downregulation of CMTM4, suggesting that miR-224-5p might be a potential target for therapies in CRC.

MarvelD3 Is Upregulated in Ulcerative Colitis and Has Attenuating Effects during Colitis Indirectly Stabilizing the Intestinal Barrier.

In inflammatory bowel disease (IBD), the impaired intestinal barrier is mainly characterized by changes in tight junction protein expression. The functional role of the tight junction-associated MARVEL protein MARVELD3 (MD3) in IBD is yet unknown. (i) In colon biopsies from IBD patients we analyzed MD3 expression and (ii) in human colon HT-29/B6 cells we studied the signaling pathways of different IBD-relevant cytokines. (iii) We generated a mouse model with intestinal overexpression of MD3 and investigated functional effects of MD3 upregulation. Colitis, graded by the disease activity index, was induced by dextran sodium sulfate (DSS) and the intestinal barrier was characterized electrophysiologically. MD3 was upregulated in human ulcerative colitis and MD3 expression could be increased in HT-29/B6 cells by IL-13 via the IL13Rα1/STAT pathway. In mice DSS colitis, MD3 overexpression had an ameliorating, protective effect. It was not based on direct enhancement of paracellular barrier properties, but rather on regulatory mechanisms not solved yet in detail. However, as MD3 is involved in regulatory functions such as proliferation and cell survival, we conclude that the protective effects are hardly targeting the intestinal barrier directly but are based on regulatory processes supporting stabilization of the intestinal barrier.

CMTM6 and CMTM7: New leads for PD-L1 regulation in breast cancer cells undergoing EMT.

Programmed death-ligand 1 (PD-L1) expression has long been used as a biomarker to stratify patients with cancer who will benefit from anti-PD-1/PD-L1 immunotherapy. However, the use of PD-L1 as a biomarker to guide treatment decisions has recently been called into question due to its dynamic and heterogeneous expression within each tumor and among different tumors as well as during tumor cell plasticity. Therefore, understanding the molecular basis of PD-L1 expression would enable delineating its value as a reliable biomarker in the clinic. Here, we provide our perspective on the involvement of CMTM6 and CMTM7 as new lead candidates for the regulation of PD-L1 in breast tumors undergoing an epithelial to mesenchymal transition.