Increased CMTM6 can predict the clinical response to PD-1 inhibitors in non-small cell lung cancer patients

sRNA binding protein RALY facilitates colorectal cancer metastasis via enhancing exosome biogenesis in m6A dependent manner

Tumor metastasis is the leading cause of cancer-related death in patients with colorectal cancer (CRC). Heterogeneous nuclear ribonucleoproteins (hnRNPs) are RNA-binding proteins, involved in the tumorigenesis and metastasis of various cancers. However, the molecular mechanisms of hnRNPs in CRC metastasis remain unclear. This study aims to uncover the pivotal roles and molecular mechanisms of hnRNPs in CRC metastasis. Clinical database analysis suggested that the expression of hnRNP-Associated with Lethal Yellow (RALY, an important member of hnRNPs) was strongly correlated with the aggressiveness and survival of CRC patients. Gain- and loss-of-function studies demonstrated that RALY promotes the production of exosomes by increasing the formation of multivesicular bodies (MVBs) and enhancing the fusion of MVBs with the plasma membrane. Notably, RALY directly interacts with phospholipase D2 (PLD2) to enable exosome biogenesis, and cooperates with RBM15b to control PLD2 mRNA stability in an m6A-dependent manner. RALY-mediated exosome secretion activates pro-tumor macrophages and further facilitates CRC metastasis, while rescue experiments in vivo further confirmed that RALY-mediated exosome biogenesis facilitates CRC metastasis. Collectively, our findings demonstrate that RALY promotes exosome biogenesis and facilitates colorectal cancer metastasis by upregulating PLD2 and enhancing exosome production in an m6A-dependent manner, suggesting potential therapeutic strategies for combating CRC metastasis.

ALYREF m5C RNA methylation reader predicts bladder cancer prognosis by regulating the tumor immune microenvironment

BACKGROUND

5-Methylcytidine (m5C) methylation is a recently emerging epigenetic modification that is closely related to tumor proliferation, occurrence, and metastasis. This study aimed to investigate the clinicopathological characteristics and prognostic value of m5C regulators in bladder cancer (BLCA), and their correlation with the tumor immune microenvironment.

METHODS

Thirteen m5C RNA methylation regulators were analyzed using RNA-sequencing and corresponding clinical information obtained from the TCGA database. The Cluster Profiler package was used to analyze the gene ontology function of potential targets and enriched the Kyoto Encyclopedia of Genes and Genomes pathway. Kaplan-Meier survival analysis was used to compare survival differences using the log-rank test and univariate Cox proportional hazards regression. The correlation between signature prognostic m5C regulators and various immune cells was analyzed. Univariate and multivariate Cox regression analyses identified independence of the ALYREF gene signature.

RESULTS

Nine out of the 13 m5C RNA methylation regulators were differentially expressed in BLCA and normal samples and were co-expressed. These 9 regulators were associated with clinicopathological tumor characteristics, particularly high or low tumor risk, pT or pTNM stage, and migration. Consensus clustering analysis divides the BLCA samples into 4 clusters. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment annotation and gene ontology function analysis identified 273 upregulated and 594 downregulated genes in BLCA. Notably, only ALYREF was significantly correlated with OS (P < .05). ALYREF exhibited significant infiltration levels in macrophage cells. Therefore, we constructed a nomogram for ALYREF as an independent prognostic factor. Additionally, we observed that both the mRNA and protein levels of ALYREF were upregulated, and immunofluorescence showed that ALYREF was mainly distributed in nuclear speckles. ALYREF overexpression was significantly associated with poor OS.

CONCLUSION

Our findings demonstrated the potential of ALYREF to predict clinical prognostic risks in BLCA patients and regulate the tumor immune microenvironment. As such, ALYREF may serve as a novel prognostic indicator in BLCA patients.

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.

Searching for Essential Genes and Targeted Drugs Common to Breast Cancer and Osteoarthritis

BACKGROUND

It is documented that osteoarthritis can promote the progression of breast cancer (BC).

OBJECTIVE

This study aims to search for the essential genes associated with breast cancer (BC) and osteoarthritis (OA), explore the relationship between epithelial-mesenchymal transition (EMT)- related genes and the two diseases, and identify the candidate drugs.

METHODS

The genes related to both BC and OA were determined by text mining. Protein-protein Interaction (PPI) analysis was carried out, and as a result, the exported genes were found to be related to EMT. PPI and the correlation of mRNA of these genes were also analyzed. Different kinds of enrichment analyses were performed on these genes. A prognostic analysis was performed on these genes for examining their expression levels at different pathological stages, in different tissues, and in different immune cells. Drug-gene interaction database was employed for potential drug discovery.

RESULTS

A total number of 1422 genes were identified as common to BC and OA and 58 genes were found to be related to EMT. We found that HDAC2 and TGFBR1 were significantly poor in overall survival. High expression of HDAC2 plays a vital role in the increase of pathological stages. Four immune cells might play a role in this process. Fifty-seven drugs were identified that could potentially have therapeutic effects.

CONCLUSION

EMT may be one of the mechanisms by which OA affects BC. Using the drugs can have potential therapeutic effects, which may benefit patients with both diseases and broaden the indications for drug use.

Clinicopathologic and prognostic significance of CMTM6 and PD-L1 expression in cervical squamous cell carcinoma

It has been demonstrated that interfering with the expression of chemokine-like factor-like MARVEL transmembrane domain-containing family member 6 (CMTM6) results in impaired programmed death 1 ligand 1 (PD-L1) protein expression in human tumor cells. PD-L1 relies on CMTM6 to inhibit T cell responses and promote tumor cell proliferation. The aim of the present study was to investigate the expression of CMTM6 and PD-L1 in cervical cancer and their clinical significance. Immunohistochemistry was used to detect the expression of CMTM6 and PD-L1 in 50 normal cervical tissues and 102 cervical cancer tissue samples. The results showed that CMTM6 and PD-L1 expression was associated with clinical staging, lymph node metastasis, distant metastasis, and tumor differentiation. In addition, there was a positive association between the expression of CMTM6 and that of PD-L1 in cervical cancer tissue. Survival analysis results showed that high expression of CMTM6 and PD-L1 was positively correlated with poor prognosis in patients. Univariate analysis showed that lymph node metastasis was associated with the prognosis of cervical cancer patients. Cox analysis indicated that PD-L1 is a risk factor affecting the survival time of cervical cancer patients. In conclusion, the expression of CMTM6 and PD-L1 is elevated in cervical cancer tissue and closely related to poor prognosis. Therefore, CMTM6 and PD-L1 may be new molecular targets for the treatment of cervical cancer.

Metabolism-related biomarkers, molecular classification, and immune infiltration in diabetic ulcers with validation

Diabetes mellitus (DM) can lead to diabetic ulcers (DUs), which are the most severe complications. Due to the need for more accurate patient classifications and diagnostic models, treatment and management strategies for DU patients still need improvement. The difficulty of diabetic wound healing is caused closely related to biological metabolism and immune chemotaxis reaction dysfunction. Therefore, the purpose of our study is to identify metabolic biomarkers in patients with DU and construct a molecular subtype-specific prognostic model that is highly accurate and robust. RNA-sequencing data for DU samples were obtained from the Gene Expression Omnibus (GEO) database. DU patients and normal individuals were compared regarding the expression of metabolism-related genes (MRGs). Then, a novel diagnostic model based on MRGs was constructed with the random forest algorithm, and classification performance was evaluated utilizing receiver operating characteristic (ROC) analysis. The biological functions of MRGs-based subtypes were investigated using consensus clustering analysis. A principal component analysis (PCA) was conducted to determine whether MRGs could distinguish between subtypes. We also examined the correlation between MRGs and immune infiltration. Lastly, qRT-PCR was utilized to validate the expression of the hub MRGs with clinical validations and animal experimentations. Firstly, 8 metabolism-related hub genes were obtained by random forest algorithm, which could distinguish the DUs from normal samples validated by the ROC curves. Secondly, DU samples could be consensus clustered into three molecular classifications by MRGs, verified by PCA analysis. Thirdly, associations between MRGs and immune infiltration were confirmed, with LYN and Type 1 helper cell significantly positively correlated; RHOH and TGF-β family remarkably negatively correlated. Finally, clinical validations and animal experiments of DU skin tissue samples showed that the expressions of metabolic hub genes in the DU groups were considerably upregulated, including GLDC, GALNT6, RHOH, XDH, MMP12, KLK6, LYN, and CFB. The current study proposed an auxiliary MRGs-based DUs model while proposing MRGs-based molecular clustering and confirmed the association with immune infiltration, facilitating the diagnosis and management of DU patients and designing individualized treatment plans.

CMTM6 as a potential therapy target is associated with immunological tumor microenvironment and can promote migration and invasion in pancreatic adenocarcinoma

CMTM6 has been connected to the development of several malignancies. However, it is still unknown what function CMTM6 serves in pancreatic adenocarcinoma (PAAD). We obtained RNA sequencing information of PAAD from public datasets and predicted statistical significance of CMTM6 survival in accordance with Kaplan-Meier curves. Gene set enrichment assessment (GSEA) was employed to analyze changes in pathways. Then, we systematically investigated the association involving CMTM6 and the immunological traits within the tumor microenvironment (TME) of PAAD, including immune pathways, immunomodulators, immune infiltrating cells, inflammatory activities, and immunotherapy response prediction. To demonstrate the biologically malignant properties of CMTM6 expression, the Cell Counting Kit-8, transwell experiments, colony formation, and wound healing were utilized. Upregulated CMTM6 expression was revealed within PAAD tissues, which was associated with more frequent somatic mutations and worse survival outcomes. Specifically, CMTM6 expression represented stronger immune infiltration, inflammatory activity, and better immunotherapeutic response in TME. Functional studies revealed that CMTM6 promoted the ability to proliferate, migrate, and invade. Additionally, CMTM6 and PD-L1 had a positive relationship, and CMTM6 can co-immunocoprecipitate with PD-L1 protein in pancreatic cell lines. CMTM6 overexpression shapes the inflammatory TME with a strong immune response. These findings support that CMTM6 is an immunotherapeutic target with promising effect to treat PAAD.

Comprehensive analysis of the prognostic and immunological signature of eight Tripartitemotif (TRIM) family molecules in human gliomas

BACKGROUND

TRIM family molecules have been identified as being involved in the tumor progression of various cancer types. Increasingly, experimental evidence indicates that some of TRIM family molecules are implicated in glioma tumorigenesis. However, the diverse genomic changes, prognostic values and immunological landscapes of TRIM family of molecules have yet to be fully determined in glioma.

METHODS

In our study, employing the comprehensive bioinformatics tools, we evaluated the unique functions of 8 TRIM members including TRIM5/17/21/22/24/28/34/47 in gliomas.

RESULTS

The expression levels of 7 TRIM members (TRIM5/21/22/24/28/34/47) were higher in glioma as well as its diverse cancer subtypes than in normal tissues, whereas the expression level of TRIM17 was the opposite, lower in the former than in the latter. In addition, survival analysis revealed that the high expression profiles of TRIM5/21/22/24/28/34/47 were associated with poor overall survival (OS), disease-specific survival (DSS) and progress-free interval (PFI) in glioma patients, whereas TRIM17 displayed adverse outcomes. Moreover, the 8 TRIM molecules expression as well as methylation profiles remarkably correlated with different WHO grades. And genetic alterations, including mutations and copy number alterations (CNAs), in the TRIM family were correlated with longer OS, DSS and progress-free survival (PFS) in glioma patients. Furthermore, through Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis results of these 8 molecules and their related genes, we found that these molecules may change the immune infiltration of the tumor microenvironment and regulate the expression of immune checkpoint molecules (ICMs), affecting the occurrence and development of gliomas. The correlation analyses between the 8 TRIM molecules and TMB (tumor mutational burden)/MSI (microsatellite instability)/ICMs discovered that as the expression level of TRIM5/21/22/24/28/34/47 increased, the TMB score also increased significantly, while TRIM17 showed an opposite outcome. Further, a 6-gene signature (TRIM 5/17/21/28/34/47) for predicting overall survival (OS) in gliomas was built by using the least absolute shrinkage and selection operator (LASSO) regression, and the survival and time-dependent ROC analyses all were found to perform well in testing and validation cohorts. Results of multivariate COX regression analysis showed that TRIM5/28 are both expected to become independent risk predictors to guide clinical treatment.

CONCLUSION

In general, the results indicate that TRIM5/17/21/22/24/28/34/47 might exert a crucial influence on gliomas tumorigenesis and might be putative prognostic markers and therapeutic targets for glioma patients.

Suppression of Tumor or Host Intrinsic CMTM6 Drives Antitumor Cytotoxicity in a PD-L1-Independent Manner

CKLF-like MARVEL transmembrane domain-containing protein 6 (CMTM6) is known to be a regulator of membranal programmed death ligand 1 (PD-L1) stability and a factor associated with malignancy progression, but the effects and mechanisms of CMTM6 on tumor growth, as well as its potential as a target for therapy, are still largely unknown. Here, we show that CMTM6 expression increased with tumor progression in both patients and mice. Ablation of CMTM6 significantly reduced human and murine tumor growth in a manner dependent on T-cell immunity. Tumor CMTM6 suppression broke resistance to immune-checkpoint inhibitors and remodeled the tumor immune microenvironment, as specific antitumor cytotoxicity was enhanced and contributed primarily to tumor inhibition. Without the PD-1/PD-L1 axis, CMTM6 suppression still significantly dampened tumor growth dependent on cytotoxic cells. Furthermore, we identified that CMTM6 was widely expressed on immune cells. T-cell CMTM6 levels increased with sustained immune activation and intratumoral immune exhaustion and affected T cell-intrinsic PD-L1 levels. Host CMTM6 knockout significantly restrained tumor growth in a manner dependent on CD8+ T cells and not entirely dependent on PD-L1. Thus, we developed and evaluated the antitumor efficacy of CMTM6-targeting adeno-associated virus (AAV), which effectively mobilized antitumor immunity and could be combined with various antitumor drugs. Our findings reveal that both tumor and host CMTM6 are involved in antitumor immunity with or without the PD-1/PD-L1 axis and that gene therapy targeting CMTM6 is a promising strategy for cancer immunotherapy.

Biomarkers Associated with Immune Checkpoint, N6-Methyladenosine, and Ferroptosis in Patients with Restenosis

Purpose

This study aimed to identify potential diagnostic markers of restenosis after stent implantation and to determine their association with immune checkpoint, ferroptosis, and N6-methyladenosine (m6A).

Patients and methods

Microarray data were downloaded from the National Center for Biotechnology Information (NCBI: GSE46560 and GSE48060 datasets) to identify differentially expressed genes (DEGs) between in-stent restenosis and no-restenosis samples. We then conducted systematic functional enrichment analyses of the DEGs based on Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG), and further predicted the interactions of different proteins using the Search Tool for the Retrieval of Interacting Genes (STRING). We used the MCC and MCODE algorithms in the cytoHubba plug-in to screen three key genes in the network, and employed receiver operating characteristic (ROC) curves to determine their diagnostic significance using a multiscale curvature classification algorithm. Next, we investigated the relationships between these target genes, immune checkpoint, ferroptosis, and m6A. Finally, quantitative real-time polymerase chain reaction (qRT-PCR) was used to verify the above results.

Results

We identified 62 upregulated genes and 243 downregulated genes. Based on GO, KEGG, and screening results, EEF1D, RPL36, and RPSA are promising genes for predicting restenosis. In addition, the methylation of YTHDF2, the ferroptosis-related gene GLS2, and the immune checkpoint-related gene CTLA4 were observed to be associated with restenosis. The qRT-PCR test confirmed that RPSA and RPL36 are useful diagnostic markers of the restenosis that can provide new insights for future studies on its occurrence and molecular mechanisms.

Conclusion

We found that RPSA and RPL36, as useful diagnostic markers of restenosis, can provide new insights for future studies on its occurrence and molecular mechanisms.

[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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CMTM6 is highly expressed in lung adenocarcinoma and can be used as a biomarker of a poor diagnosis

Background

CMTM6 which is chemokine-like factor (CKLF)-like Marvel transmembrane domain containing family member 6 is involved in the occurrence and progression of various tumors. However, the role of CMTM6 is still unclear in lung adenocarcinoma (LUAD).

Methods

Immunohistochemical, Western blotting and RT‒PCR methods were used to detect the expression of CMTM6 in LUAD. Cox regression and the Kaplan‒Meier method were performed to assess overall survival. Immunogenic features were evaluated according to immune cell infiltrations, immune checkpoints. The sensitivity to chemotherapy agents was estimated using the pRRophetic package.

Results

In LUAD, the expression of CMTM6 was obviously upregulated and was significantly associated with T stage (p = 0.008) and lymph node metastasis (p = 0.018). Multivariate Cox regression analysis demonstrated that CMTM6 was a specialty prognostic risk factor. Based on GSEA enrichment analysis, we found that high expression of CMTM6 is associated with multiple immune signaling pathways. The group with high CMTM6 expression showed a positive association with various types of tumor-infiltrating cells. Moreover, a total of 36 chemotherapeutic drugs were significantly correlated with the expression of CMTM6. Among them, two chemotherapeutic drugs had better therapeutic effects in the high CMTM6 expression group, while 34 chemotherapeutic drugs had therapeutic effects in the low CMTM6 expression group.

Conclusion

This study confirmed that CMTM6 is highly expressed in LUAD and is a new independent poor prognostic factor. In addition, the high expression of CMTM6 is closely related to the tumor microenvironment and immunotherapy, providing new ideas for the treatment of posterior LUAD.

High expression of CMTM6 is a risk factor for poor prognosis of gastrointestinal tumors: A meta-analysis

Previous research on the link between CMTM6 expression dysregulation and tumor prognosis has been conflicting. In this study, the predictive effect of CMTM6 in malignant tumors was carefully evaluated using meta-analysis. The literature on the relationship between CMTM6 expression level and malignant tumor prognosis was searched in PubMed, Medline, Embase, and Web of Science databases until April 2021. Data were extracted from eligible studies and analyzed using RevMan5.3 and STATA 12.0 software. The HR and 95%CI were used to analyze the link between CMTM6 expression and OS. And the correlation between CMTM6 expression and clinicopathological features LNM and DM was evaluated by OR and 95%CI. Literature screening eventually included 12 studies involving 2133 patients with malignant tumors. High CMTM6 expression was found to be strongly linked with shorter OS and PFS in cancer patients (HR = 1.84,95%CI: 1.28-2.63, P = 0.001). High CMTM6 expression in gastrointestinal cancers was found to be significantly related with a shorter OS (HR = 2.21, 95%CI: 1.75-2.78, P 0.001). PFS was observed to be related with high CMTM6 expression in cancer patients (HR = 2.029, 95%CI: 1.263-3.26, P = 0.003). Meanwhile, high CMTM6 expression was highly associated to LNM (OR = 1.64, 95%CI: 1.02-2.64, P = 0.043) and DM (OR = 4.07, 95%CI: 1.73-9.56, P = 0.001). However, the expression level of CMTM6 in non-gastrointestinal tumors was not statistically significant with OS or LNM. High CMTM6 expression in gastrointestinal cancers is linked to shorter OS and PFS, as well as LNM and DM, suggesting that high CMTM6 expression could be employed as a new diagnosis for poor prognosis and metastasis.

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.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09999-y.

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.

Expression and Clinical Significance of CMTM6 and PD-L1 in Triple-Negative Breast Cancer

The CKLF-like MARVEL transmembrane domain containing 6 (CMTM6) plays an extremely important role of the programed death receptor ligand-1 (PD-L1) protein. Our study is aimed at investigating the expression of CMTM6 and PD-L1 proteins in triple-negative breast cancer and their correlation with the clinical pathological data of patients. We selected 89 cases of triple-negative breast cancer and 62 cases of normal breast tissue specimens. Immunohistochemical methods were used to detect the expression levels of CMTM6 and PD-L1 and to carefully study differences in their expression. The expression of CMTM6 and PD-L1 in TNBC was higher than that in normal breast tissue, and the expression of the two was positively correlated (p < 0.05). In TNBC, CMTM6 expression is positively correlated with tumor size, lymph node metastasis, Ki67 proliferation index, and TNM stage (p < 0.05). PD-L1 expression is positively correlated with tumor size, lymph node metastasis, Ki67 proliferation index, TNM stage, and vascular infiltration (p < 0.05). Kaplan-Meier analysis showed that the positive expression of CMTM6 and PD-L1 had no correlation with the survival rate of patients (p > 0.05). According to KM-plotter, we found that a higher CMTM6 expression was positively related with relapse-free survival rate of patients (p < 0.05). A higher PD-L1 expression was positively correlated with relapse-free, overall, and distant metastasis survival rate of patients (p < 0.05). In timer database, we found a positive correlation between the expression of CMTM6 and PD-L1 in triple-negative breast cancer. Both CMTM6 and PD-L1 are highly expressed in TNBC, and their expressions are positively related. In the future, the two gene might become targets for the treatment of TNBC, providing a basis of clinical treatment of TNBC.

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.

CMTM6 as a master regulator of PD-L1

Immune checkpoint proteins, such as programmed cell death receptor 1 (PD-1) and its ligand (PD-L1), play critical roles in the pathology of chronic inflammatory pathological conditions, particularly cancer. In addition, the activation of PD-1/PD-L1 pathway is involved in mediating resistance to certain anti-cancer chemo- and immuno-therapeutics. Unfortunately, targeting the PD-1/PD-L1 pathway by the available anti-PD-1/PD-L1 drugs can benefit only a small proportion of cancer patients. Thus, studying the factors that regulate the expression of these immune checkpoint proteins is of central importance in this context. Recent investigations have identified CMTM6 and, to a lesser extent, CMTM4, as master regulators of PD-L1 expression in various cancer cells. Understanding the mechanisms by which such proteins upregulate the expression of PD-L1 in tumor cells, and determining the potential regulators of CMTM6 expression in different types of cancers will accelerate the development of new therapeutic targets and/or lead to the enhancement of the currently available PD-1/PD-L1 blockade therapies.

The clinical and prognostic significance of CMTM6/PD-L1 in oncology

The recent discovery of CMTM6 and to a lesser extent CMTM4, two members of the chemokine-like factor (CKLF)-like MARVEL transmembrane domain-containing family, as master positive regulators of PD-L1 expression, the primary ligand of programmed cell death 1 (PD-1), on tumor and immune cells has opened new horizons for investigating the role of CMTM6/CMTM4 in different aspects of oncology including their clinical and prognostic values in different cancer types. The absence of a specific review article addressing the available results about the clinical and prognostic roles of CMTM6 alone and/or in combination with PD-L1 in cancer has encouraged us to write this paper.

Predicting Diagnostic Gene Biomarkers Associated With Immune Checkpoints, N6-Methyladenosine, and Ferroptosis in Patients With Acute Myocardial Infarction

This study aimed to determine early diagnosis genes of acute myocardial infarction (AMI) and then validate their association with ferroptosis, immune checkpoints, and N6-methyladenosine (m6A), which may provide a potential method for the early diagnosis of AMI. Firstly, we downloaded microarray data from NCBI (GSE61144, GSE60993, and GSE42148) and identified differentially expressed genes (DEGs) in samples from healthy subjects and patients with AMI. Also, we performed systematic gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses and used STRING to predict protein interactions. Moreover, MCC and MCODE algorithms in the cytoHubba plug-in were used to screen nine key genes in the network. We then determined the diagnostic significance of the nine obtained DEGs by plotting receiver operating characteristic curves using a multiscale curvature classification algorithm. Meanwhile, we investigated the relationship between AMI and immune checkpoints, ferroptosis, and m6A. In addition, we further validated the key genes through the GSE66360 dataset and consequently obtained nine specific genes that can be used as early diagnosis biomarkers for AMI. Through screening, we identified 210 DEGs, including 53 downregulated and 157 upregulated genes. According to GO, KEGG, and key gene screening results, FPR1, CXCR1, ELANE, TLR2, S100A12, TLR4, CXCL8, FPR2 and CAMP could be used for early prediction of AMI. Finally, we found that AMI was associated with ferroptosis, immune checkpoints, and m6A and FPR1, CXCR1, ELANE, TLR2, S100A12, TLR4, CXCL8, FPR2 and CAMP are effective markers for the diagnosis of AMI, which can provide new prospects for future studies on the pathogenesis of AMI.

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.

Impact of CKLF-like MARVEL transmembrane domain containing 6 (CMTM6) expression in gastric cancer

Background : CKLF-like MARVEL transmembrane domain containing 6 (CMTM6) is the master regulator of programmed cell death-ligand 1 (PD-L1). We aimed to clarify the significance of CMTM6 expression in gastric cancer (GC). Methods : A total of 105 patients who had undergone curative surgical resection for stage II / III GC at Tokushima University Hospital were included in this study. The expression of CMTM6 was examined by immunohistochemistry. Additionally, the relationship of each expression level to several prognostic factors was examined using univariate and multivariate analyses. Results : CMTM6 was not positively correlated with any of the factors examined. The overall survival (OS) rates were significantly poorer in the CMTM6 high-expression group than in the CMTM low-expression group (5-year OS : 57.2% vs. 79.2%, respectively ; p < 0.05). Disease-free survival (DFS) was significantly poorer in the CMTM high-expression group than in the CMTM6 low-expression group (5-year DFS : 52.8% vs. 72.4%, respectively ; p < 0.05). Multivariate analysis confirmed CMTM6 expression as an independent prognostic factor in DFS (p < 0.05). CMTM6 expression tended to be correlated with PD-L1 expression (p = 0.07). Conclusions : CMTM6 is associated with a poor prognosis and immunotolerance through PD-L1 in GC. J. Med. Invest. 68 : 362-367, August, 2021.

ARID1A, ARID1B, and ARID2 Mutations Serve as Potential Biomarkers for Immune Checkpoint Blockade in Patients With Non-Small Cell Lung Cancer

Worldwide, non-small cell lung cancer (NSCLC) has the highest morbidity and mortality of all malignancies. The lack of responsiveness to checkpoint inhibitors is a central problem in the modern era of cancer immunotherapy, with the rapid development of immune checkpoint inhibitors (ICIs) in recent years. The human switch/sucrose nonfermentable (SWI/SNF) chromatin-remodeling complex has been reported to be recurrently mutated in patients with cancer, and those with SWI/SNF mutations have been reported to be sensitive to ICIs. Six reported cohorts, a total of 3416 patients, were used to analyze the mutation status of ARID1A, ARID1B, ARID2 and SMARCA4 in patients with NSCLC and the effect of mutations on prognosis after ICIs. Finally, a nomogram was established to guide the clinical use of ICIs. The results show that patients with NSCLC who have ARID1A, ARID1B, and ARID2 mutations of the SWI/SNF complex were more likely to benefit from ICI therapy.

CMTM6 expression in M2 macrophages is a potential predictor of PD-1/PD-L1 inhibitor response in colorectal cancer

Background

CMTM6 is a novel key regulator of PD-L1. High expression of both CMTM6 and PD-L1 may predict the benefit of PD-1 axis blockade in lung cancer. We aimed to investigate the expression pattern of CMTM6 between mismatch repair-defective (dMMR) and mismatch repair-proficient (pMMR) colorectal cancer (CRC) tissues and assess its correlation with the response to PD-1/PD-L1 pathway blockade.

Methods

Immunohistochemistry (IHC) was used to analyze CMTM6 and PD-L1 expression and immune cell density in dMMR/pMMR CRC. Quantitative multiplex immunofluorescence (IF) was performed to detect CMTM6, PD-L1, CD4, CD8, CD68 and CD163 expression in CRC patients treated with PD-1/PD-L1 inhibitors.

Result

IHC analysis showed that CMTM6 and PD-L1 were both expressed in tumor cells (TCs) and invasion front immune cells (ICs). CMTM6 and PD-L1 expression and CD4⁺, CD8⁺, CD68⁺ or CD163⁺ cell density were significantly higher in dMMR CRC patients than in pMMR CRC patients. CMTM6 expression was positively correlated with PD-L1 expression and CD163⁺ M2 macrophage density in dMMR CRC. IF analysis showed that the coexpression rate of CMTM6/PD-L1 and the expression rate of CMTM6 in CD8⁺ T cells and CD163⁺ M2 macrophages were significantly increased in the group that exhibited clinical benefit. CMTM6 expression in M2 macrophages was identified as the best biomarker for predicting the responsiveness to PD-1/PD-L1 inhibitors.

Conclusions

CMTM6 expression in M2 macrophages may predict the PD-1/PD-L1 inhibitor response rate in CRC patients more accurately than dMMR/microsatellite instability-high (MSI-H) status. It can also identify pMMR CRC patients who could benefit from PD-1/PD-L1 inhibitors.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00262-021-02931-6.

The association between the expression of PD-L1 and CMTM6 in undifferentiated pleomorphic sarcoma

BACKGROUND

Undifferentiated pleomorphic sarcoma (UPS) is a sarcoma with a poor prognosis. A clinical trial, SARC028, revealed that treatment with anti-PD-1 drugs was effective against UPS. Studies have reported that UPS expresses PD-L1, sometimes strongly (≥ 50%). However, the mechanism of PD-L1 expression in UPS has remained unclear. CKLF-like MARVEL transmembrane domain containing 6 (CMTM6) was identified as a novel regulator of PD-L1 expression. The positive relationship between PD-L1 and CMTM6 has been reported in several studies. The aim of this study was thus to examine CMTM6 expression in UPS and evaluate the relationship between PD-L1 and CMTM6 in this disease.

MATERIALS AND METHODS

Fifty-one primary UPS samples were subjected to CMTM6 and PD-L1 immunostaining. CMTM6 expression was assessed using proportion and intensity scores. CMTM6 gene copy number was also evaluated using a real-time PCR-based copy number assay. We also analyzed the mRNA expression and copy number variation of PD-L1 and CMTM6 in The Cancer Genome Atlas (TCGA) data.

RESULTS

TCGA data indicated that the mRNAs encoded by genes located around 3p22 were coexpressed with CMTM6 mRNA in UPS. Both proportion and intensity scores of CMTM6 positively correlated with strong PD-L1 expression (≥ 50%) (both p = 0.023). CMTM6 copy number gain increased CMTM6 expression. Patients with UPS with a high CMTM6 intensity score had a worse prognosis for overall survival.

CONCLUSIONS

UPS showed variation in CMTM6 copy number and CMTM6 expression. CMTM6 expression was significantly correlated with PD-L1 expression, especially with strong PD-L1 expression.

CMTM6 promotes migration, invasion, and EMT by interacting with and stabilizing vimentin in hepatocellular carcinoma cells

Background

CKLF like MARVEL transmembrane domain containing 6 (CMTM6) has been associated with the development in many kinds of cancers. However, the roles of CMTM6 in hepatocellular carcinoma (HCC) are largely unknown. Thus, the present study aimed to investigate the function of CMTM6 in HCC.

Methods

We analysed CMTM6 levels and functions using human HCC cell lines, paired HCC and adjacent non-tumorous tissues, and a tissue microarray. CMTM6 expression was silenced using short hairpin RNAs and its was overexpressed from a lentivirus vector. CMTM6 mRNA and protein levels were determined using quantitative real-time reverse transcription PCR and western blotting, respectively. Proliferation, colony formation, migration, and invasion were assessed using a Cell counting kit-8, colony formation, wound-healing, and Matrigel invasion assays, respectively. Immunohistochemistry was used to score the expression of CMTM6 in tissue samples. The localization and binding partners of CMTM6 were investigated using immunofluorescence and coimmunoprecipitation experiments, respectively. A mouse xenograft model was used for in vivo studies.

Results

Compared with that in adjacent, non-cancerous tissue, Here, CMTM6 levels were increased in HCC tissue samples. Silencing of CMTM6 suppressed the proliferation, migration, and invasion of HCC cells. Conversely, CMTM6 overexpression enhanced HCC cell invasion, migration, and proliferation. Mechanistically, CMTM6 physically interacts with and stabilizes vimentin, thus inducing epithelial–mesenchymal transition (EMT), which promotes proliferation, migration and invasion. Importantly, in HCC tissues, CMTM6 expression correlated positively with vimentin levels. Poor prognosis of HCC was associated significantly with higher CMTM6 expression.

Conclusions

CMTM6 has an important function in HCC proliferation, migration, and invasion, via its interaction with and stabilization of vimentin. CMTM6 might represent a potential biomarker and therapeutic target to treat HCC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-02787-5.

CMTM6 and PD-1/PD-L1 overexpression is associated with the clinical characteristics of malignancy in oral squamous cell carcinoma

OBJECTIVES

This study aimed to evaluate the expression of chemokine-like factor superfamily 6 (CMTM6) and programmed cell death 1 (PD-1)/programmed death ligand 1 (PD-L1) in oral squamous cell carcinoma (OSCC) and to further explore its clinical significance in OSCC.

STUDY DESIGN

Samples of 44 OSCC and paracancerous tissues were investigated. We estimated the expression of the 3 proteins by immunohistochemistry and further detected mRNA expression by quantitative real-time polymerase chain reaction (qRT-PCR).

RESULTS

Immunohistochemistry results demonstrated that the positive expression of CMTM6 and PD-1/PD-L1 in OSCC tissues was significantly higher than that in paracancerous tissues. Statistical significance was found between the 2 groups (all P < .05). Moreover, PD-L1 expression was related to OSCC clinical stage and lymph node metastasis (P < .05). The qRT-PCR results confirmed that the relative expression of CMTM6 and PD-1/PD-L1 mRNA in OSCC tissues was significantly higher than that in paracancerous tissues (all P < .05), and Spearman rank correlation showed that there was a significant relationship between mRNA and protein expression (all P < .05).

CONCLUSIONS

CMTM6 and PD-1/PD-L1 were upregulated in OSCC, and CMTM6 may play a synergistic role with PD-1/PD-L1 in the immune pathway. Therefore, we believe that CMTM6 and PD-1/PD-L1 will become checkpoints for immunotherapy of OSCC.

CMTM6 drives cisplatin resistance by regulating Wnt signaling through the ENO-1/AKT/GSK3β axis

Rewiring tumor cells to undergo drug-induced apoptosis is a promising way to overcome chemoresistance. Therefore, identifying causative factors for chemoresistance is of high importance. Unbiased global proteome profiling of sensitive, early, and late cisplatin-resistant oral squamous cell carcinoma (OSCC) lines identified CMTM6 as a top-ranked upregulated protein. Analyses of OSCC patient tumor samples demonstrated significantly higher CMTM6 expression in chemotherapy (CT) nonresponders as compared with CT responders. In addition, a significant association between higher CMTM6 expression and poorer relapse-free survival in esophageal squamous cell carcinoma, head and neck squamous cell carcinoma, and lung squamous cell carcinoma was observed from Kaplan-Meier plot analysis. Stable knockdown (KD) of CMTM6 restored cisplatin-mediated cell death in chemoresistant OSCC lines. Upon CMTM6 overexpression in CMTM6-KD lines, the cisplatin-resistant phenotype was rescued. The patient-derived cell xenograft model of chemoresistant OSCC displaying CMTM6 depletion restored the cisplatin-induced cell death and tumor burden substantially. The transcriptome analysis of CMTM6-KD and control chemoresistant cells depicted enrichment of the Wnt signaling pathway. We demonstrated that CMTM6 interaction with membrane-bound Enolase-1 stabilized its expression, leading to activation of Wnt signaling mediated by AKT–glycogen synthase kinase-3β. CMTM6 has been identified as a stabilizer of programmed cell death ligand 1. Therefore, as CMTM6 facilitates tumor cells for immune evasion and mediates cisplatin resistance, it could be a promising therapeutic target for treating therapy-resistant OSCC.

CMTM6 Stabilizes PD-L1 Expression and Is a New Prognostic Impact Factor in Hepatocellular Carcinoma

CKLF-like MARVEL transmembrane domain containing 6 (CMTM6) was identified as a regulator of programmed death ligand 1 (PD-L1), which induces antitumor immunity in several cancers. This study aimed to clarify the relationship between CMTM6 and PD-L1 expression and clinical outcomes in patients with hepatocellular carcinoma (HCC). In total, 259 patients with HCC who had undergone hepatic resection were enrolled. Immunohistochemical staining for CMTM6 and PD-L1 was performed. The relationships between CMTM6 expression and the clinicopathological characteristics and outcomes were analyzed. Additionally, the stabilization of PD-L1 expression and regulation of malignant activities by CMTM6 were examined in vitro. Our patients were divided into high (n = 65, 25.1%) and low (n = 194, 74.9%) CMTM6 expression groups. High CMTM6 expression was significantly associated with malignant aggregates, including poor differentiation (P < 0.0001), microscopic intrahepatic metastasis (P = 0.0369), and multiple intrahepatic recurrences (P = 0.0211). CMTM6 expression was significantly correlated with PD-L1 expression in HCC tissues (P < 0.0001). The patients were classified into three groups: high CMTM6/PD-L1 positive (n = 21), high CMTM6/ PD-L1 negative (n = 44), and low CMTM6 (n = 194) expression pattern groups. Overall survival was significantly different among the three groups (P < 0.0001). Additionally, immunohistochemical double staining revealed that CMTM6 and PD-L1 were co-expressed on HCC cells. In vitro, PD-L1 expression was enhanced at late time points in the presence of CMTM6 expression. CMTM6 also regulated epithelial-to-mesenchymal transition and stemness phenotypes in HCC cells. Conclusion: Our large cohort study found that CMTM6 co-expressed with PD-L1 was strongly associated with the clinical outcome in patients with HCC. The evaluation of CMTM6 combined with PD-L1 in HCC might be useful for patient selection in immune checkpoint therapy.

Co-expression of CMTM6 and PD-L1: a novel prognostic indicator of gastric cancer

BACKGROUND

CKLF Like MARVEL Transmembrane Domain Containing 6 (CMTM6) is involved in the epigenetic regulation of genes and tumorigenesis. Programmed cell death ligand 1 (PD-L1) is closely related to the prognosis of some human cancers. CMTM6 is a key regulator of PD-L1 in many cancers. The purpose of this study was to investigate the expressions of these proteins in gastric cancer and the correlations with clinicopathological features and survival.

METHODS

The expression levels of CMTM6 and PD-L1 were examined in 185 gastric cancer specimens using immunohistochemistry, quantitative real-time PCR and Western blot. Immunofluorescence was used to examine the localizations of CMTM6 and PD-L1. Chi-square test was used to analyze the relationship between CMTM6 and PD-L1 expressions and clinicopathological characteristics. Kaplan-Meier method and log-rank test were used to analyze the survival data of patients.

RESULTS

The positive expression rates of CMTM6 and PD-L1 in gastric cancers were 78.38% (145/185) and 75.68% (140/185), respectively. CMTM6 and PD-L1 were both mainly expressed in the cell membrane and nucleus of gastric cancer tumor cells. High expression of CMTM6 and PD-L1 was correlated with Borrmann type (P < 0.001), N stage (P = 0.002), peritoneal metastasis (P = 0.007) and TNM stage (P = 0.038). CMTM6 and PD-L1 expression in gastric cancer tissues showed a positive correlation (Pearson's coefficient test, r = 0.260; P < 0.001). CMTM6 may positively regulate PD-L1 expression. High expression of CMTM6 was correlated with poor prognosis of gastric cancer patients (HR = 1.668; 95% CI = 1.032-2.695; P = 0.037). High expression of both CMTM6 and PD-L1 may be an independent factor for overall survival (HR = 1.554; 95% CI = 1.011-2.389; P = 0.044).

CONCLUSION

The combined detection of CMTM6 and PD-L1 may be used as an indicator for judging the prognosis of gastric cancer patients.

Prognostic Implications of Pan-Cancer CMTM6 Expression and Its Relationship with the Immune Microenvironment

CKLF-like MARVEL transmembrane domain-containing 6 (CMTM6) reportedly stabilizes programmed death-ligand 1 (PD-L1) and enhances the efficacy of immunotherapy. However, correlations between CMTM6 expression and the immune microenvironment and its prognostic value remain unknown in a variety of tumors. CMTM6 expression data were obtained from The Cancer Genome Atlas (TCGA) for 33 cancer types classified into high and low expression subgroups according to the median CMTM6 expression value. Pan-cancer analysis of CMTM6 protein expression in 20 tumor types was performed using a cohort from the Human Protein Atlas (HPA). PD-L1 protein expression data were obtained from The Cancer Proteome Atlas (TCPA) for 32 cancer types. Frequencies of CMTM6 copy number alterations and mutations were analyzed using cBioPortal. MANTIS was employed to estimate microsatellite instability in the TCGA cohort. CIBERSORT and the ESTIMATE algorithm were applied to estimate the relative fractions of infiltrating immune cell types and immune scores, respectively. Kaplan-Meier survival curve analysis was performed to assess the pan-cancer prognostic value of CMTM6.CMTM6 is heterogeneously expressed in diverse cancers. Further, the results revealed low CMTM6 mutation frequencies in multiple cancers. Among them, CMTM6 mutation frequency was the highest in uterine cancer. Additionally, CMTM6 expression was related to PD-L1 protein expression in breast invasive carcinoma, cervical squamous cell carcinoma and endocervical adenocarcinoma, cholangiocarcinoma, glioblastoma multiforme (GBM), head and neck squamous cell carcinoma, kidney renal papillary cell carcinoma, sarcoma (SARC), stomach adenocarcinoma, and uterine carcinosarcoma. Increased CMTM6 expression may be associated with increased infiltration of neutrophils in some types of cancer. Finally, pan-cancer analysis indicated that CMTM6 expression was closely related to overall survival in adrenocortical carcinoma, GBM, acute myeloid leukemia, liver hepatocellular carcinoma, mesothelioma, SARC, thymoma, and uveal melanoma. Taken together, these findings highlight that CMTM6 plays an important role in the tumor immune microenvironment, and CMTM6 has been identified to have prognostic value in some types of cancers. Thus, CMTM6 is a potential target for cancer immunotherapy and effective prognostic biomarker.

Emerging Role of Ubiquitination in the Regulation of PD-1/PD-L1 in Cancer Immunotherapy

A growing amount of evidence suggests that ubiquitination and deubiquitination of programmed death 1 (PD-1)/programmed death-ligand 1 (PD-L1) play crucial roles in the regulation of PD-1 and PD-L1 protein stabilization and dynamics. PD-1/PD-L1 is a major coinhibitory checkpoint pathway that modulates immune escape in cancer patients, and its engagement and inhibition has significantly reshaped the landscape of tumor clearance. The abnormal ubiquitination and deubiquitination of PD-1/PD-L1 influence PD-1/PD-L1-mediated immunosuppression. In this review, we describe the ubiquitination- and deubiquitination-mediated modulation of PD-1/PD-L1 signaling through a variety of E3 ligases and deubiquitinating enzymes (DUBs). Moreover, we briefly expound on the anticancer potential of some agents that target related E3 ligases, which further modulate the ubiquitination of PD-1/PD-L1 in cancers. Therefore, this review reveals the development of a highly promising therapeutic approach for cancer immunotherapy by targeting PD-1/PD-L1 ubiquitination.

The association of CMTM6 expression with prognosis and PD-L1 expression in triple-negative breast cancer

Background

Immune checkpoint inhibitors play a vital role in triple-negative breast cancer (TNBC) immunotherapy. A recent study showed that chemokine-like factor (CKLF)-like MARVEL transmembrane domain containing 6 (CMTM6) has a crucial role in programmed death-ligand 1 (PD-L1) stability. The aim of this study was to investigate the relationship between CMTM6 and PD-L1 in TNBC and the association with clinical characteristics.

Methods

A total of 143 patients, including 75 with human epidermal growth factor receptor 2 (HER2)-driven breast cancer and 68 with TNBC, were included in this study. In 83 paired primary breast cancers (PBCs) and metastatic breast cancers (MBC) comprising 45 HER2-driven breast cancers and 38 TNBC, CMTM6 and PD-L1 were detected based on immunohistochemistry (IHC) with FFPE tissues. Another 60 PBCs comprising 30 HER2-driven breast cancers and 30 TNBC in order to detect CMTM6 and PD-L1 mRNA expressions based on real-time polymerase chain reaction (RT-PCR) using frozen tissues. Furthermore, 153 patients comprising 30 TNBC and 123 HER2-driven breast cancer based on The Cancer Genome Atlas (TCGA) database were used to confirm the difference mRNA expression.

Results

The expression of CMTM6 in patients with TNBC was significantly higher than in those with HER2-driven PBC (IHC, P=0.036, mRNA, P=0.036, TCGA dataset, P=0.039). CMTM6 was correlated with PD-L1 based on IHC in triple-negative MBC (P=0.004); the same result was found based on mRNA data in triple- negative PBC (P=0.021). Moreover, a high expression of CMTM6 in TNBC was associated with poor progression-free survival (PFS) (P=0.030, 95% CI: 1.08-4.57, HR =2.22). After multiple Cox regression analysis, CMTM6 in TNBC emerged as an independent risk factor for PFS (P=0.027, 95% CI: 1.11-5.20, HR =2.40). The expression of PD-L1 was negatively correlated with lymph node metastasis (P=0.026) and was not associated with PFS.

Conclusions

The expression of CMTM6 was higher in TNBC than in HER2-driven breast cancer. In TNBC, CMTM6 was correlated with PD-L1 expression, and potentially could be used as an independent risk factor for predicting PFS.

Quantitative analysis of CMTM6 expression in tumor microenvironment in metastatic melanoma and association with outcome on immunotherapy

Chemokine-like factor (CKLF)-like MARVEL transmembrane domain containing 6 (CMTM6) modulates degradation of a number of proteins, including programmed death ligand-1 (PD-L1) by protecting it from ubiquitin-mediated degradation. In this role, it could modulate the effectiveness of immunotherapy. Here, for the first time, we characterize CMTM6 expression in melanoma and evaluate its association with response to immune checkpoint inhibitors (ICI). We evaluated the expression of CMTM6, PD-L1 and other immune-related proteins in 60 pretreatment biopsies from metastatic melanoma patients who received immunotherapy, in a tissue microarray (TMA) using quantitative immunofluorescence (QIF). Expression of mRNA from control patients obtained from The Cancer Genome Atlas (TCGA) database was also compared. CMTM6 expression was positively correlated with PD-L1, CD3, CD20, and CD68 markers, at protein (Pearson's r = 0.53-0.81, all P < .0001) and mRNA (Spearman's r = 0.15-0.44, all P < .002, except for CD68 where P = .26) levels. CMTM6 protein was associated with longer survival after immunotherapy when measured in the stromal (P = .007) and all the immune compartments tested (T cells, B cells, and macrophages). Multivariable analyses also revealed significant CMTM6 survival associations when measured in stromal (Hazard Ratio (HR) = 0.12, P = .001) and CD68-positive (HR = 0.30, P = .043) compartments. Additionally, PD-L1 but not CMTM6 showed prognostic value in control patients. Finally, high CMTM6 and PD-L1 co-expression in the stromal compartment was significantly associated with longer survival in treated patients (P = .028). Consequently, CMTM6 expression shows potential as a predictive factor for ICI treatments.

Role of PD-L1 Expression during the Progression of Submucosal Gastric Cancer

INTRODUCTION

Programmed death-ligand 1 (PD-L1) expression is a prognostic marker for gastric cancer that correlates with tumor diameter and depth of penetration. But the role of PD-L1 and mechanism(s) employed in the initial phase of invasion in early gastric cancer is yet to be understood.

OBJECTIVE

This study aims to elucidate the role of PD-L1 during the progression of gastric cancer, specifically invading the submucosa beyond the lamina muscularis mucosa.

METHODS

Using 107 patients with pathological submucosal gastric cancer, we determined the expression of PD-L1 based on the staining of the cell membrane or cytoplasm of tumor cells in the central and invasive front of the tumor. Samples were categorized into 3 groups based on the intensity of PD-L1 expression. CD8+ lymphocytes expressing PD-1 and CD163+ macrophages were used to determine the number of cell nuclei at the invasive front, similar to PD-L1. CMTM6 levels were determined and used to stratify samples into 3 groups.

RESULTS

PD-L1 expression was higher in the invasive front (26.2%) than in the central portion of the tumors (7.4%; p < 0.001). Moreover, lymphatic and vascular invasion were more frequently observed in samples with high levels of PD-L1 (lymphatic invasion: 60.7 vs. 35.4%, p = 0.0026, and vascular invasion: 39.3 vs. 16.5%, p = 0.0018). There was no correlation between PD-L1 expression and the levels of PD-1, CD8, CD163, and CMTM6.

CONCLUSIONS

PD-L1-expressing cancer cells at the invasive front of gastric cancer influence the initial stages of tumor invasion and lymphovascular permeation in early-stage gastric cancers. Immune checkpoint signaling may be the driving force in the invasive front during the invasion of the submucosa beyond the lamina muscularis mucosa.

Expression and Clinical Significance of CMTM6 in Nonsmall Cell Lung Cancer

Chemokine-like factor (CKLF)-like MARVEL transmembrane domain containing protein 6 (CMTM6) is a ubiquitously expressed protein, which plays a critical role in the stability of programmed death-ligand 1. However, the expression of CMTM6 in a variety of cancer pathological tissues is not clear. Therefore, 109 patients who were diagnosed with nonsmall cell lung cancer (NSCLC) and underwent surgical resection were included in this retrospective study. The expression of CMTM6 in NSCLC patients' tissue samples were measured by immunohistochemistry and the results showed that 60 cases (55.05%) had high CMTM6 expression. The chi-square test showed that the expression of CMTM6 in NSCLC was significantly related to smoking (p = 0.017) and differentiation (p = 0.029). The Kaplan-Meier survival analysis suggested that the high expression of CMTM6 was associated with better prognosis of NSCLC patients. The univariate analysis revealed that the prognosis of NSCLC patients was correlated with T stage (p = 0.042), lymph node metastasis (p = 0.007), metastasis (p = 0.009), pathological differentiation (p = 0.001), and CMTM6 expression level (p < 0.001). In addition, multivariate analysis indicated that CMTM6 was an independent prognostic factor for NSCLC patients (p = 0.002). CMTM6 expression may have the potential to be a biomarker assisting in disease monitoring and prognosis in NSCLC.

CMTM6 is positively correlated with PD-L1 expression and immune cells infiltration in lung squamous carcinoma

BACKGROUND

The aim of this study was to clarify the association between CMTM6 and PD-L1 expression as well as microenvironment in lung squamous carcinoma (LUSC).

MATERIAL AND METHODS

Using Spearman's correlation and Tumor Immune Estimation Resource (TIMER), we analyzed the relationship between CMTM6 and PD-L1 mRNA in LUSC. Immunohistochemistry (IHC) assay was applied to validate the correlation between CMTM6 and PD-L1 protein level in 80 LUSC samples originated from Shandong Provincial Hospital. Then, using The Cancer Genome Atlas (TCGA) database and fisher test, we analyzed the differential mutation genes in high and low CMTM6 expression group. TISIDB was used to explore the distribution of CMTM6 across immune- and molecular-subtypes. TCGA database and Gene Set variation analysis (GSVA) were used to analyze the relationship between CMTM6 and immune genes, immune related pathways.

RESULT

Positive correlation between CMTM6 and PD-L1 in mRNA and protein level was found in LUSC patients. More gene mutations were found in CMTM6 high expression group compared with low expression group. Meanwhile, we also found the correlation between CMTM6 expression and molecular subtypes, immune genes, immune related pathways. Furthermore, our result revealed that B cells memory, T cells memory testing, T cells folicular helper, macrophages M0, macrophages M1 and neutrophils varied significantly between patients with CMTM6 high and low expression group. Finally, we found that CMTM6 expression was positively related to CD8 + T cell, macrophage, neutrophil and dendtritic cell (all, P < 0.05) and negatively related to CD4 + T cell (P = 0.018).

CONCLUSION

CMTM6 is positively associated with PD-L1 expression and correlates with infiltration of immune cells in microenvironment of lung squamous carcinoma.

CMTM6 significantly relates to PD-L1 and predicts the prognosis of gastric cancer patients

Background

The CKLF-like MARVEL transmembrane domain containing 6 (CMTM6) is a key regulator of the programed death receptor ligand-1 (PD-L1) protein. However, the usefulness of CMTM6 expression as a prognostic indicator and the relationship between CMTM6 and PD-L1 expression in gastric cancer (GC) remains unclear.

Objectives

We evaluated the expression and prognostic implications of CMTM6 in GC tissue and its relationship with PD-L1 expression.

Patients and methods

The protein expressions of CMTM6 and PD-L1 were detected in 122 cases of postoperative GC tissue using immunohistochemical (IHC) assays. Kaplan-Meier survival analysis was used to calculate the survival probability and a log-rank test was used to compare the survival curves. Univariate and multivariate Cox proportional hazard regression analyses were used to evaluate the clinically-related factors associated with survival. Pearson's correlation was used to determine the correlation analysis and estimate the statistical significance. The univariate and multivariate logistic regression analyses were used to analyze the relationship between clinically-related factors and PD-L1 expression.

Results

Kaplan-Meier survival analysis showed that patients with high CMTM6 expression had shorter overall survival (OS) than those with low expression (P < 0.001). The expression of CMTM6 was an independent risk factor for prognosis in multivariate Cox proportional hazard regression analyses (HR:2.221, CI% [1.36-3.628], P = 0.001). The OS of patients with positively expressed PD-L1 was significantly shorter than those with negatively expressed PD-L1 (P = 0.003). The expression of CMTM6 was significantly related to the positive expression of PD-L1 in gastric cancer tissues (r = 0.186, P = 0.041). The expression of CMTM6 was the independent risk factor for PD-L1 expression in multivariate logistic regression analysis (OR:2.538, CI% [1.128-5.714], P = 0.024).

Conclusion

CMTM6 expression is significantly related to PD-L1 and may be a useful prognostic indicator and a specific therapeutic target for cancer immunotherapy for GC patients.

Coexpression of CMTM6 and PD-L1 as a predictor of poor prognosis in macrotrabecular-massive hepatocellular carcinoma

The "macrotrabecular-massive" (MTM) pattern of hepatocellular carcinoma (HCC) has been suggested to represent a distinct HCC subtype and is associated with specific molecular features. Since the immune microenvironment is heterogenous in HCC, it is important to evaluate the immune microenvironment of this novel variant. CMTM6, a key regulator of PD-L1, is an important immunocheckpoint inhibitor. This study aimed to evaluate the prognostic effect of CMTM6/PD-L1 coexpression and its relationship with inflammatory cells in HCC. We analyzed 619 HCC patients and tumors were classified into MTM and non-MTM HCC subtypes. The expression levels of CMTM6 and PD-L1 in tumor and inflammatory cells were evaluated by immunohistochemistry. The density of inflammatory cells in the cancer cell nest was calculated. Tumoral PD-L1 expression and inflammatory cell density were higher in the MTM type than in the non-MTM type. CMTM6-high expression was significantly associated with shorter OS and DFS than CMTM6-low expression in the whole HCC patient population and the MTM HCC patient population. Moreover, MTM HCC patients with CMTM6/PD-L1 coexpression experienced a higher risk of HCC progression and death. In addition, CMTM6/PD-L1 coexpression was shown to be related to a high density of inflammatory cells. Notably, a new immune classification, based on CMTM6/PD-L1 coexpression and inflammatory cells, successfully stratified OS and DFS in MTM HCC. CMTM6/PD-L1 coexpression has an adverse effect on the prognosis of HCC patients, especially MTM HCC patients. Our study provides evidence for the combination of immune status assessment with anti-CMTM6 and anti-PD-L1 therapy in MTM HCC patients.

HIP1R Expression and Its Association with PD-1 Pathway Blockade Response in Refractory Advanced NonSmall Cell Lung Cancer: A Gene Set Enrichment Analysis

Huntingtin-interacting protein 1-related protein (HIP1R) plays an important role in the regulation of programmed death-ligand 1 (PD-L1). The aim of this study was to investigate the expression of HIP1R and confirm its predictive or prognostic roles in anti-PD-1 therapy in nonsmall cell lung cancer (NSCLC) patients. HIP1R and PD-L1 immunohistochemical expression was examined in 52 refractory advanced NSCLC patients treated with anti-PD-1 inhibitors. We performed gene set enrichment analysis (GSEA) to detect HIP1R-specific gene sets. Patients in the PD-1 inhibitor responder group had lower HIP1R expression by univariate logistic regression analysis (odds ratio (OR) = 0.235, p = 0.015) and multivariate logistic regression analysis (OR = 0.209, p = 0.014). Patients with high HIP1R expression had poorer progression-free survival (PFS) than patients with low HIP1R expression in univariate analysis (p = 0.037) and multivariate Cox analysis (hazard ratio = 2.098, p = 0.019). The web-based mRNA dataset also showed that high HIP1R expression correlated with inferior overall survival in lung adenocarcinoma (p = 0.026). GSEA revealed that HIP1R levels correlate with a set of genes that reflect PD-L1-related immune pathways. HIP1R expression may be a promising predictor for determination of patient responses to anti-PD-1 treatment.

Molecular and immune characteristics for lung adenocarcinoma patients with CMTM6 overexpression

BACKGROUND

CMTM6 was identified as an important regulator of the PD-L1 protein. The role of CMTM6 in lung adenocarcinoma (LUAD) has so far remained unclear. We aimed at investigating the role of CMTM6 in LUAD at transcriptome and genomic levels and its relationship with tumor-infiltrating immune cells (TIICs).

METHODS

We downloaded the data sets of LUAD from TCGA. The genomic profiles containing somatic mutations were analyzed and the transcriptome level of CMTM6 was also obtained. Gene set variation analysis (GSVA) was used to predict the pathway change. In addition, we explored the association between CMTM6 and LUAD immune infiltrates by means of CIBERSORT. The association between CMTM6 and PD-L1 mRNA was analyzed using an integrated repository portal for tumor-immune system interactions (TISIDB) and was further validated in 80 LUAD patients. Kaplan-Meier survival curve and the log-rank test was used to analyze the survival significance of CMTM6.

RESULTS

We found that CMTM6 was downregulated in LUAD. Patients with low CMTM6 expression were more likely to be frequent with somatic mutations. Moreover, GSVA analysis exhibited that CMTM6 was associated with immune responses and inflammatory activities. Specifically, a positive correlation between increased CMTM6 expression and immune infiltrating level of Dendritic cells resting, Eosinophils, Macrophages M1, Macrophages M2, Neutrophils, T cells CD4 memory activated and T cells CD4 memory resting was established. The CMTM6 expression was positively correlated with PD-L1 in both mRNA and protein level. Clinically, patients with high expression of CMTM6 tended to have a better survival.

CONCLUSION

CMTM6 expression likely had an important effect on TIICs composition and prognosis in LUAD patients. The CMTM6 expression was positively correlated with PD-L1 in LUAD. These findings establish CMTM6 as a promising target for immunotherapeutic prospects.

Proteasomal and lysosomal degradation for specific and durable suppression of immunotherapeutic targets

Cancer immunotherapy harness the body’s immune system to eliminate cancer, by using a broad panel of soluble and membrane proteins as therapeutic targets. Immunosuppression signaling mediated by ligand-receptor interaction may be blocked by monoclonal antibodies, but because of repopulation of the membrane via intracellular organelles, targets must be eliminated in whole cells. Targeted protein degradation, as exemplified in proteolysis targeting chimera (PROTAC) studies, is a promising strategy for selective inhibition of target proteins. The recently reported use of lysosomal targeting molecules to eliminate immune checkpoint proteins has paved the way for targeted degradation of membrane proteins as crucial anti-cancer targets. Further studies on these molecules’ modes of action, target-binding “warheads”, lysosomal sorting signals, and linker design should facilitate their rational design. Modifications and derivatives may improve their cell-penetrating ability and the in vivo stability of these pro-drugs. These studies suggest the promise of alternative strategies for cancer immunotherapy, with the aim of achieving more potent and durable suppression of tumor growth. Here, the successes and limitations of antibody inhibitors in cancer immunotherapy, as well as research progress on PROTAC- and lysosomal-dependent degradation of target proteins, are reviewed.

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.