HuR up-regulates cell surface PD-L1 via stabilizing CMTM6 transcript in cancer.
Ontology highlight
ABSTRACT:
SUBMITTER: Liu Y
PROVIDER: S-EPMC7994200 | biostudies-literature |
REPOSITORIES: biostudies-literature
Similar Datasets
Project description:CMTM6 is a critical regulator of cell surface expression of PD-L1 in tumor cells, but little is known about the transcriptional regulation of CMTM6. Here we report that the expression of CMTM6 positively correlates with the epithelial to mesenchymal transition (EMT) score in breast cancer cell lines and with the major EMT marker Vimentin in triple-negative breast cancers (TNBC). We showed that CMTM6 is concomitantly overexpressed with PD-L1 in breast mesenchymal compared with the epithelial cells. Driving a mesenchymal phenotype in SNAI1-inducible MCF-7 cells (MCF-7Mes cells) increased both PD-L1 and CMTM6. CMTM6 silencing in MCF-7Mes cells partially reduced cell surface expression of PD-L1, indicating that a proportion of the PD-L1 on the surface of MCF-7Mes cells depends on CMTM6. We also found a positive correlation between CMTM3 and CMTM7 expression with EMT score in breast cancer cells, and with Vimentin in TNBC patients. Dual knockdown of CMTM6 and CMTM7 significantly decreased PD-L1 surface expression in MCF-7Mes cells, indicating that both CMTM6 and CMTM7 regulate the expression of PD-L1. This study highlights the importance of CMTM6 and CMTM7 in EMT-induced PD-L1 and suggests that EMT, CMTM6 or CMTM7 modulators can be combined with anti-PD-L1 in patients with highly aggressive breast cancer.
| S-EPMC7963182 | biostudies-literature
Project description:Cancer cells exploit the expression of the programmed death-1 (PD-1) ligand 1 (PD-L1) to subvert T-cell-mediated immunosurveillance. The success of therapies that disrupt PD-L1-mediated tumour tolerance has highlighted the need to understand the molecular regulation of PD-L1 expression. Here we identify the uncharacterized protein CMTM6 as a critical regulator of PD-L1 in a broad range of cancer cells, by using a genome-wide CRISPR-Cas9 screen. CMTM6 is a ubiquitously expressed protein that binds PD-L1 and maintains its cell surface expression. CMTM6 is not required for PD-L1 maturation but co-localizes with PD-L1 at the plasma membrane and in recycling endosomes, where it prevents PD-L1 from being targeted for lysosome-mediated degradation. Using a quantitative approach to profile the entire plasma membrane proteome, we find that CMTM6 displays specificity for PD-L1. Notably, CMTM6 depletion decreases PD-L1 without compromising cell surface expression of MHC class I. CMTM6 depletion, via the reduction of PD-L1, significantly alleviates the suppression of tumour-specific T cell activity in vitro and in vivo. These findings provide insights into the biology of PD-L1 regulation, identify a previously unrecognized master regulator of this critical immune checkpoint and highlight a potential therapeutic target to overcome immune evasion by tumour cells.
| S-EPMC5706633 | biostudies-literature
Project description:BackgroundCircular RNAs (circRNAs) have been shown to play diverse biological functions in the progression of multiple diseases. However, the impacts of circRNAs on breast cancer (BC) progression remains unclear. Therefore, the objective of this paper is to investigate the role and mechanisms of a functional circRNA in BC metastasis and immune escape.MethodsThis study used a circRNA microarray and identified a novel circRNA hsa_circ_0067842. The validation and characteristics of hsa_circ_0067842 were investigated using qRT-PCR, sanger sequencing, RNase R treatment, actinomycin D treatment and fluorescence in situ hybridization (FISH). Gain- and loss-of-function assays were performed to evaluate the biological function of hsa_circ_0067842 in BC progression and immune escape. Mechanistically, the interaction between hsa_circ_0067842 and HuR was explored by RNA pull down, mass spectrometry (MS), subcellular component protein extraction and immunofluorescence (IF). The regulatory mechanisms of hsa_circ_0067842/HuR/CMTM6/PD-L1 axis were investigated by qRT-PCR, western blot, FISH, immunoprecipitation and rescue assays.ResultsThe expression of hsa_circ_0067842 was upregulated in BC tissues and cells, which was found to be significantly associated with poor prognosis, regardless of other clinical covariates. Function assays showed that hsa_circ_0067842 promoted the migration and invasion capacities of BC cells. Moreover, co-culture experiment with peripheral blood mononuclear cells (PBMCs) showed that hsa_circ_0067842 played a role in the immune escape of BC cells. Mechanistically, our study showed that hsa_circ_0067842 interacted with HuR, affecting its nuclear translocation, thus enhancing the stability of CMTM6. CMTM6 not only enhances the migration and invasion ability of BC cells, but also affects the ubiquitination of PD-L1 and inhibits its degradation.ConclusionCollectively, our results demonstrated that hsa_circ_0067842 promoted BC progression through the HuR/CMTM6/PD-L1 axis, providing new insight and a potential target for BC prognosis and therapy.
| S-EPMC10436663 | biostudies-literature
Project description:Modulation of Immune check point regulators, especially the PD-1/PD-L1 axis, plays a critical role in successful management of a small proportion of lung cancer patients, but not so effective in the rest of lung cancer patients. A better understanding of immunotherapy non-responsive or resistant patients therefore warranted for future development of novel therapeutics. The newly identified regulator CMTM6 (CKLF-like MARVEL transmembrane domain containing 6) has been reported to serves as the stabilizer of PD-L1 and enhances the inhibitory effect of PD-L1 on immune system in both cell line and animal models, but its clinical relevance associated with PD-L1 is unknown and the current study is designed to address this question. The study using immunohistochemistry demonstrated that CMTM6 positivity from 15 out of 19 types of cancers with our in-house tissue microarray, and PD-L1 expression is always found only in CMTM6 positive cancers. CMTM6 and PD-L1 expression were analyzed in 81 lung cancer patient sample, and we observed that CMTM6 expression correlated with cancer histotypes and inversely correlated with cancer metastases, but not with patients' age and gender. No PD-L1 expression was observed in negative CMTM6 samples. Higher expression PD-L1 is also associated with higher CMTM6 expression. In summary, CMTM6 expression is associated with PD-L1 expression, as well as lung cancer histotypes and metastasis. The results thus for the first time confirmed earlier reports on CMTM6/PD-L1 connection, from a clinical aspect of analysis.
| S-EPMC6804456 | biostudies-literature
Project description:The clinical benefit for patients with diverse types of metastatic cancers that has been observed upon blockade of the interaction between PD-1 and PD-L1 has highlighted the importance of this inhibitory axis in the suppression of tumour-specific T-cell responses. Notwithstanding the key role of PD-L1 expression by cells within the tumour micro-environment, our understanding of the regulation of the PD-L1 protein is limited. Here we identify, using a haploid genetic screen, CMTM6, a type-3 transmembrane protein of previously unknown function, as a regulator of the PD-L1 protein. Interference with CMTM6 expression results in impaired PD-L1 protein expression in all human tumour cell types tested and in primary human dendritic cells. Furthermore, through both a haploid genetic modifier screen in CMTM6-deficient cells and genetic complementation experiments, we demonstrate that this function is shared by its closest family member, CMTM4, but not by any of the other CMTM members tested. Notably, CMTM6 increases the PD-L1 protein pool without affecting PD-L1 (also known as CD274) transcription levels. Rather, we demonstrate that CMTM6 is present at the cell surface, associates with the PD-L1 protein, reduces its ubiquitination and increases PD-L1 protein half-life. Consistent with its role in PD-L1 protein regulation, CMTM6 enhances the ability of PD-L1-expressing tumour cells to inhibit T cells. Collectively, our data reveal that PD-L1 relies on CMTM6/4 to efficiently carry out its inhibitory function, and suggest potential new avenues to block this pathway.
| S-EPMC6333292 | biostudies-literature
Project description:PD-L1 (programmed death ligand 1) and PD-L2 are cell-surface glycoproteins that interact with programmed death 1 (PD-1) on T cells to attenuate inflammation. PD-1 signaling has attracted intense interest for its role in a pathophysiological context: suppression of anti-tumor immunity. Similarly, vitamin D signaling has been increasingly investigated for its non-classical actions in stimulation of innate immunity and suppression of inflammatory responses. Here, we show that hormonal 1,25-dihydroxyvitamin D (1,25D) is a direct transcriptional inducer of the human genes encoding PD-L1 and PD-L2 through the vitamin D receptor, a ligand-regulated transcription factor. 1,25D stimulated transcription of the gene encoding PD-L1 in epithelial and myeloid cells, whereas the gene encoding the more tissue-restricted PD-L2 was regulated only in myeloid cells. We identified and characterized vitamin D response elements (VDREs) located in both genes and showed that 1,25D treatment induces cell-surface expression of PD-L1 in epithelial and myeloid cells. In co-culture experiments with primary human T cells, epithelial cells pretreated with 1,25D suppressed activation of CD4+ and CD8+ cells and inhibited inflammatory cytokine production in a manner that was abrogated by anti-PD-L1 blocking antibody. Consistent with previous observations of species-specific regulation of immunity by vitamin D, the VDREs are present in primate genes, but neither the VDREs nor the regulation by 1,25D is present in mice. These findings reinforce the physiological role of 1,25D in controlling inflammatory immune responses but may represent a double-edged sword, as they suggest that elevated vitamin D signaling in humans could suppress anti-tumor immunity.
| S-EPMC5733602 | biostudies-literature
Project description:The cell-autonomous balance of immune-inhibitory and -stimulatory signals is a critical process in cancer immune evasion. Using patient-derived co-cultures, humanized mouse models, and single-cell RNA-sequencing of patient melanomas biopsied before and on immune checkpoint blockade, we find that intact cancer cell-intrinsic expression of CD58 and ligation to CD2 is required for anti-tumor immunity and is predictive of treatment response. Defects in this axis promote immune evasion through diminished T cell activation, impaired intratumoral T cell infiltration and proliferation, and concurrently increased PD-L1 protein stabilization. Through CRISPR-Cas9 and proteomics screens, we identify and validate CMTM6 as critical for CD58 stability and upregulation of PD-L1 upon CD58 loss. Competition between CD58 and PD-L1 for CMTM6 binding determines their rate of endosomal recycling over lysosomal degradation. Overall, we describe an underappreciated yet critical axis of cancer immunity and provide a molecular basis for how cancer cells balance immune inhibitory and stimulatory cues.
| S-EPMC10524902 | biostudies-literature
Project description:The cell-autonomous balance of immune-inhibitory and -stimulatory signals is a critical process in cancer immune evasion. Using patient-derived co-cultures, humanized mouse models, and single cell RNA-sequencing of patient melanomas biopsied before and on immune checkpoint blockade, we find that intact cancer-cell-intrinsic expression of CD58 and ligation to CD2 is required for anti-tumor immunity and is predictive of treatment response. Defects in this axis promote immune evasion through diminished T cell activation, impaired intratumoral T cell infiltration and proliferation, and concurrently increased PD-L1 protein stabilization. Through CRISPR-Cas9 and proteomics screens, we identify and validate CMTM6 as critical for CD58 maintenance and upregulation of PD-L1 upon CD58 loss. Competition by CD58 and PD-L1 for CMTM6 (via both extracellular loop domains) determines their rate of endosomal recycling over lysosomal degradation. Overall, we describe an underappreciated yet critical axis of cancer immunity and provide a molecular basis for how cancer cells balance immune inhibitory and stimulatory cues.
2023-07-06 | PXD039710 | Pride
Project description:Programmed cell death ligand 1 (PD-L1) is an immunosuppressive molecule expressed on tumor cells. By interacting with programmed cell death-1 (PD-1) on T cells, it inhibits immune responses. Because PD-L1 expression on cancer cells increases their chemoresistance, we investigated the correlation between PD-L1 and multidrug resistance 1/ P-glycoprotein (MDR1/P-gp) expression in breast cancer cells. Analysis of breast cancer tissues using tissue microarrays revealed a significant correlation between PD-L1 and MDR1/P-gp protein levels. Increased expression of PD-L1 was associated with lymph node metastasis and histological tumor grade. In addition, interaction of PD-L1 with PD-1 induced phosphorylation of AKT and ERK, resulting in the activation of PI3K/AKT and MAPK/ERK pathways and increased MDR1/P-gp expression in breast cancer cells. The PD-1/PD-L1 interaction also increased survival of breast cancer cells incubated with doxorubicin. These findings suggest that the PD-1/PD-L1 inhibition may increase chemotherapy efficacy by inhibiting the MDR1/P-gp expression in breast cancer cells.
| S-EPMC5725139 | biostudies-literature
Project description:BackgroundCKLF 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.MethodsThe 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.ResultsThe 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).ConclusionThe combined detection of CMTM6 and PD-L1 may be used as an indicator for judging the prognosis of gastric cancer patients.
| S-EPMC7842018 | biostudies-literature