The Prognostic Effect of MAC30 Expression on Patients With Non-Small Cell Lung Cancer Receiving Adjuvant Chemotherapy

Meningioma-associated protein 30 accelerates the proliferation and invasion of hepatocellular carcinoma by modulating Wnt/GSK-3β/β-catenin signaling

Meningioma-associated protein 30 (MAC30) has been recently identified as a new tumor-associated protein that is implicated in multiple tumor types. However, the role of MAC30 in hepatocellular carcinoma (HCC) has not been studied. In the current study, we explored the expression, biological function and underlying mechanism of MAC30 in HCC. We found that MAC30 expression was significantly elevated in HCC tissues and cell lines. Functional in vitro assays demonstrated that the knockdown of MAC30 inhibited the proliferation and invasion of HCC cells, while MAC30 overexpression facilitated these biological behaviors. Moreover, the knockdown of MAC30 decreased glycogen synthase kinase (GSK)-3β phosphorylation level and β-catenin expression, leading to the inactivation of Wnt/β-catenin signaling in HCC cells. The inhibition of GSK-3β or reactivation Wnt/β-catenin signaling markedly reversed MAC30 knockdown-mediated inhibitory effects on the proliferation and invasion of HCC cells. Notably, the inhibition of Wnt/β-catenin signaling abrogated the MAC30-evoked oncogenic role in HCC cells. In addition, the knockdown of MAC30 impeded tumor formation and the growth rate of HCC cells in vivo. Taken together, our data recognized MAC30 as a potential tumor-promotion factor in HCC, which accelerated the proliferation and invasion of HCC through the up-regulation of Wnt/β-catenin signaling. Our study suggests MAC30 as a potential anticancer target for HCC.

TMEM206 is a potential prognostic marker of hepatocellular carcinoma

Transmembrane proteins are involved in the transportation of materials into and out of cells. The transmembrane protein (TMEM) family is a collection of poorly described transmembrane proteins that serve important roles in tumor development and progression. A number of TMEM proteins have been discovered. A newly discovered TMEM protein, TMEM206, transports ions across the membrane under physiological and pathological conditions, generating an acidic environment, which serves an important role in the microenvironment. However, the prognostic value and regulatory mechanisms of action of TMEM206 in tumors is unclear. The aim of the present study was to evaluate the prognostic value and regulation mechanisms of TMEM206 in tumors. Firstly, the expression of TMEM206 in tumors and normal tissues was assessed using the GEPIA and Oncomine databases and the results revealed that TMEM206 expression increased or decreased depending on the type of tumor. Subsequently, using the Human Protein Atlas and the Kaplan-Meier plotter, the findings of the present study revealed that TMEM206 is related to the prognosis of hepatocellular carcinoma. In order to explore the mechanism of TMEM206 in promoting tumor progression, GEO and cBioPortal were used to determine genes that may be co-expressed with TMEM206. MetaScape was used to identify the signaling pathways that TMEM206 may participate in. Finally, miRWalk, miRDB and TargetScan were used to identify miRNAs that may regulate the expression of TMEM206 and the findings revealed that 2 miRNA (hsa-miR-325 and hsa-miR-510-5p) were involved. In conclusion, upregulation of TMEM206 is associated with poor prognosis in patients with hepatocellular carcinoma.

The Biological Function of Sigma-2 Receptor/TMEM97 and Its Utility in PET Imaging Studies in Cancer

The sigma-2 receptor was originally defined pharmacologically and recently identified as TMEM97. TMEM97 has been validated as a biomarker of proliferative status and the radioligand of TMEM97, [18F]ISO-1, has been developed and validated as a PET imaging biomarker of proliferative status of tumors and as a predictor of the cancer therapy response. [18F]ISO-1 PET imaging should be useful to guide treatment for cancer patients. TMEM97 is a membrane-bound protein and localizes in multiple subcellular organelles including endoplasmic reticulum and lysosomes. TMEM97 plays distinct roles in cancer. It is reported that TMEM97 is upregulated in some tumors but downregulated in other tumors and it is required for cell proliferation in certain tumor cells. TMEM97 plays important roles in cholesterol homeostasis. TMEM97 expression is regulated by cholesterol-regulating signals such as sterol depletion and SREBP expression levels. TMEM97 regulates cholesterol trafficking processes such as low density lipoprotein (LDL) uptake by forming complexes with PGRMC1 and low density lipoprotein receptor (LDLR), as well as cholesterol transport out of lysosome by interacting with and regulating NPC1 protein. Understanding molecular functions of TMEM97 in proliferation and cholesterol metabolism will be important to develop strategies to diagnose and treat cancer and cholesterol disorders using a rich collection of TMEM97 radiotracers and ligands.

Small-Molecule Modulators of Sigma1 and Sigma2/TMEM97 in the Context of Cancer: Foundational Concepts and Emerging Themes

There are two known subtypes of the so-called sigma receptors, Sigma1 and Sigma2. Sigma1 (encoded by the SIGMAR1 gene and also known as Sigma-1 receptor, S1R) is a unique pharmacologically regulated integral membrane chaperone or scaffolding protein that allosterically modulates the activity of its associated proteins. Sigma2, recently identified as transmembrane protein 97 (TMEM97), is an integral membrane protein implicated in cellular cholesterol homeostasis. A number of publications over the past two decades have suggested a role for both sigma proteins in tumor biology. Although there is currently no clinically used anti-cancer drug that targets Sigma1 or Sigma2/TMEM97, a growing body of evidence supports the potential of small-molecule compounds with affinity for these proteins, putative sigma ligands, as therapeutic agents to treat cancer. In preclinical models, these compounds have been reported to inhibit cancer cell proliferation, survival, adhesion, and migration; furthermore, they have been demonstrated to suppress tumor growth, to alleviate cancer-associated pain, and to exert immunomodulatory properties. Here, we will address the known knowns and the known unknowns of Sigma1 and Sigma2/TMEM97 ligand actions in the context of cancer. This review will highlight key discoveries and published evidence in support of a role for sigma proteins in cancer and will discuss several fundamental questions regarding the physiological roles of sigma proteins in cancer and sigma ligand mechanism of action.

Transmembrane (TMEM) protein family members: Poorly characterized even if essential for the metastatic process

The majority of cancer-associated deaths are related to secondary tumor formation. This multistep process involves the migration of cancer cells to anatomically distant organs. Metastasis formation relies on cancer cell dissemination and survival in the circulatory system, as well as adaptation to the new tissue notably through genetic and/or epigenetic alterations. A large number of proteins are clearly identified to play a role in the metastatic process but the structures and modes of action of these proteins are essentially unknown or poorly described. In this review, we detail the involvement of members of the transmembrane (TMEM) protein family in the formation of metastases or in the mechanisms leading to cancer cell dissemination such as migration and extra-cellular matrix remodelling. While the phenotype associated with TMEM over or down-expression is clear, the mechanisms by which these proteins allow cancer cell spreading remain, for most of them, unclear. In parallel, the 3D structures of these proteins are presented. Moreover, we proposed that TMEM proteins could be used as prognostic markers in different types of cancers and could represent potential targets for cancer treatment. A better understanding of this heterogeneous family of poorly characterized proteins thus opens perspectives for better cancer patient care.

TMEM Proteins in Cancer: A Review

A transmembrane protein (TMEM) is a type of protein that spans biological membranes. Many of them extend through the lipid bilayer of the plasma membrane but others are located to the membrane of organelles. The TMEM family gathers proteins of mostly unknown functions. Many studies showed that TMEM expression can be down- or up-regulated in tumor tissues compared to adjacent healthy tissues. Indeed, some TMEMs such as TMEM48 or TMEM97 are defined as potential prognostic biomarkers for lung cancer. Furthermore, experimental evidence suggests that TMEM proteins can be described as tumor suppressors or oncogenes. TMEMs, such as TMEM45A and TMEM205, have also been implicated in tumor progression and invasion but also in chemoresistance. Thus, a better characterization of these proteins could help to better understand their implication in cancer and to allow the development of improved therapy strategies in the future. This review gives an overview of the implication of TMEM proteins in cancer.

Pleural MAC30 as a prognostic marker in NSCLC with malignant pleural effusion

Over-expressed meningioma-associate protein (MAC30) in tissues was associated with malignant tumor differentiation, metastasis and poor prognosis. However, the attention of MAC30 in pleural effusion from lung tumor is insufficient. Our retrospective study was prepared to explore the clinical values on diagnosis and prognosis of MAC30 from malignant pleural effusion (MPE) in non-small cell lung cancer (NSCLC). Levels of MAC30 were confirmed in MPE from 48 NSCLC patients and in benign pleural effusion (BPE) from 45 controls via enzyme-linked immunosorbent assay (ELISA). The association of MAC30 in MPE with clinical significance was further determined. We found that the levels of MAC30 in MPE were obviously higher than those in BPE (p < 0.05). Moreover, with a cutoff point (17.5 ng/ml), we confirmed the sensitivity and specificity of MAC30 for MPE were 82.7% and 85.3% using ROC curve analysis. Indeed, longer overall survival (OS) was present in NSCLC patients with low MAC30 expression in MPE. Multivariate analysis explicated that elevated MAC30 in MPE was an independent prognostic factor for shorter OS of NSCLC. Our data suggests that MAC30 in pleural effusion could be a potential prognostic marker in NSCLC with MPE.

The prognostic role of MAC30 in advanced gastric cancer patients receiving platinum-based chemotherapy

AIM

We aimed to investigate a practical profile of MAC30 on chemotherapeutic response in gastric cancer (GC).

PATIENTS & METHODS

We elected 87 GC patients receiving platinum-based chemotherapy in this study. MAC30 levels in tumor and adjuvant nontumor tissues were confirmed via reverse transcription-PCR to identify the clinical profile in GC and the correlation with therapeutic response.

RESULTS

We found elevated MAC30 in GC compared with the matched adjacent nontumor tissues. GC with enhanced MAC30 exhibited poorer survival by Kaplan-Meier analysis and poor response to adjuvant platinum-based chemotherapy. A multivariate analysis showed that MAC30 was an independent prognostic factor of overall survival in GC receiving platinum-based chemotherapy.

CONCLUSION

MAC30 could play as a potential biomarker for prognosis of GC with platinum-based chemotherapy.