Expression of TMBIM6 in Cancers: The Involvement of Sp1 and PKC

Cell-type-specific alternative polyadenylation promotes oncogenic gene expression in non-small cell lung cancer progression

Disrupted alternative polyadenylation (APA) is frequently involved in tumorigenesis and cancer progression by regulating the gene expression of oncogenes and tumor suppressors. However, limited knowledge of tumor-type- and cell-type-specific APA events may lead to novel APA events and their functions being overlooked. Here, we compared APA events across different cell types in non-small cell lung cancer (NSCLC) and normal tissues and identified functionally related APA events in NSCLC. We found several cell-specific 3'-UTR alterations that regulate gene expression changes showed prognostic value in NSCLC. We further investigated the function of APA-mediated 3'-UTR shortening through loss of microRNA (miRNA)-binding sites, and we identified and experimentally validated several oncogene-miRNA-tumor suppressor axes. According to our analyses, we found SPARC as an APA-regulated oncogene in cancer-associated fibroblasts in NSCLC. Knockdown of SPARC attenuates lung cancer cell invasion and metastasis. Moreover, we found high SPARC expression associated with resistance to several drugs except cisplatin. NSCLC patients with high SPARC expression could benefit more compared to low-SPARC-expression patients with cisplatin treatment. Overall, our comprehensive analysis of cell-specific APA events shed light on the regulatory mechanism of cell-specific oncogenes and provided opportunities for combination of APA-regulated therapeutic target and cell-specific therapy development.

STRIP2 motivates non-small cell lung cancer progression by modulating the TMBIM6 stability through IGF2BP3 dependent

BACKGROUND

Striatin interacting protein 2 (STRIP2) is a core component of the striatin-interacting phosphatase and kinase (STRIPAK) complexes, which is involved in tumor initiation and progression via the regulation of cell contractile and metastasis. However, the underlying molecular mechanisms of STRIP2 in non-small cell lung cancer (NSCLC) progression remain largely unknown.

METHODS

The expressions of STRIP2 and IGF2BP3 in human NSCLC specimens and NSCLC cell lines were detected using quantitative RT-PCR, western blotting, and immunohistochemistry (IHC) analyses. The roles and molecular mechanisms of STRIP2 in promoting NSCLC progression were investigated in vitro and in vivo.

RESULTS

Here, we found that STRIP2 expression was significantly elevated in NSCLC tissues and high STRIP2 expression was associated with a poor prognosis. Knockdown of STRIP2 suppressed tumor growth and metastasis in vitro and in vivo, while STRIP2 overexpression obtained the opposite effect. Mechanistically, P300/CBP-mediated H3K27 acetylation activation in the promoter of STRIP2 induced STRIP2 transcription, which interacted with insulin-like growth factor 2 mRNA-binding protein 3 (IGF2BP3) and upregulated IGF2BP3 transcription. In addition, STRIP2-IGF2BP3 axis stimulated m6A modification of TMBIM6 mRNA and enhanced TMBIM6 stability. Consequently, TMBIM6 involved NSCLC cell proliferation, migration and invasion dependent on STRIP2 and IGF2BP3. In NSCLC patients, high co-expression of STRIP2, IGF2BP3 and TMBIM6 was associated with poor outcomes.

CONCLUSIONS

Our findings indicate that STRIP2 interacts with IGF2BP3 to regulate TMBIM6 mRNA stability in an m6A-dependent manner and may represent a potential prognostic biomarker and therapeutic target for NSCLC.

miR‑302d‑3p regulates the viability, migration and apoptosis of breast cancer cells through regulating the TMBIM6‑mediated ERK signaling pathway

MicroRNAs (miRs/miRNAs) play important roles in the occurrence, metastasis and prognosis of multiple types of cancers. However, the specific role of miR-302d-3p and its underlying mechanism in breast cancer (BC) have not yet been reported. The present study aimed to identify the role of miR-302D-3p in BC and its potential mechanism using BC cell lines MCF7 and MDA-MB-231 and normal breast epithelial cell MCF-10A. Cancer and paracancerous tissue from patients with BC were also used. Reverse transcription-quantitative PCR was performed to detect the expression of miR-302d-3p and transmembrane Bax inhibitor motif containing 6 (TMBIM6). Dual-luciferase reporter assays verified the binding sites of miR-302d-3p and TMBIM6. Immunohistochemistry was used to measure the expression of TMBIM6. Cell transfection techniques were used to overexpress or interfere with miR-302d-3p and TMBIM6. A Cell Counting Kit-8 assay was performed to detect cell viability, and migration was measured using a wound healing assay. Apoptosis was detected by flow cytometry. The expression levels of apoptosis-related proteins and pathway-related proteins were detected by western blotting. The expression of miR-302d-3p in BC cell lines was found to be downregulated. It was also demonstrated that miR-302d-3p could inhibit cell viability and migration and promote apoptosis. The expression of TMBIM6 in BC cell lines and tissues was upregulated. Upregulated miR-302d-3p was shown to inhibit viability and migration, and promote apoptosis by targeting TMBIM6, during which extracellular signal-regulated kinase (ERK) and its phosphorylation were inhibited in the ERK signaling pathway in cells. Overall, the present study demonstrated that miR-302d-3p could regulate the viability, migration and apoptosis of BC cells through regulating TMBIM6-mediated ERK signaling pathway.

Quercetin Improves Cardiomyocyte Vulnerability to Hypoxia by Regulating SIRT1/TMBIM6-Related Mitophagy and Endoplasmic Reticulum Stress

Cardiomyocyte apoptosis is an important pathological mechanism underlying cardiovascular diseases and is commonly caused by hypoxia. Moreover, hypoxic injury occurs not only in common cardiovascular diseases but also following various treatments of heart-related conditions. One of the major mechanisms underlying hypoxic injury is oxidative stress. Quercetin has been shown to exert antioxidant stress and vascular protective effects, making it a promising candidate for treating cardiovascular diseases. Therefore, we examined the protective effect of quercetin on human cardiomyocytes subjected to hypoxia-induced oxidative stress damage and its underlying mechanism. Human cardiomyocytes were subjected to hypoxia/reoxygenation (H/R) in vitro with or without quercetin pretreatment; thereafter, flow cytometry, Cell Counting Kit-8 assay, laser scanning confocal microscopy, quantitative PCR, western blotting, and enzyme-linked immunosorbent assay were performed to analyze the effects of quercetin on cardiomyocytes. We found that H/R induced reactive oxygen species overproduction and endoplasmic reticulum stress, as well as inhibited the function of the mitochondria/endoplasmic reticulum and mitophagy, eventually leading to apoptosis and decreasing the viability of human cardiomyocytes. Quercetin pretreatment inhibited H/R-mediated overproduction of reactive oxygen species and damage caused by oxidative stress, increased mitophagy, regulated mRNA and protein expression of transmembrane BAX inhibitor-1 motif-containing 6 (TMBIM6), regulated endoplasmic reticulum stress, and improved the vulnerability of human cardiomyocytes to H/R. Furthermore, transfection with short interfering RNA against silent information regulator protein 1 (SIRT1) counteracted the protective effects of quercetin on cardiomyocytes. Thus, quercetin was predicted to regulate mitophagy and endoplasmic reticulum stress through SIRT1/TMBIM6 and inhibit H/R-induced oxidative stress damage. These findings may be useful for developing treatments for hypoxic injury-induced cardiovascular diseases and further highlight the potential of quercetin for regulating mitochondrial quality control and endoplasmic reticulum function.

TMBIM6/BI-1 contributes to cancer progression through assembly with mTORC2 and AKT activation

Transmembrane B cell lymphoma 2-associated X protein inhibitor motif-containing (TMBIM) 6, a Ca²⁺ channel-like protein, is highly up-regulated in several cancer types. Here, we show that TMBIM6 is closely associated with survival in patients with cervical, breast, lung, and prostate cancer. TMBIM6 deletion or knockdown suppresses primary tumor growth. Further, mTORC2 activation is up-regulated by TMBIM6 and stimulates glycolysis, protein synthesis, and the expression of lipid synthesis genes and glycosylated proteins. Moreover, ER-leaky Ca²⁺ from TMBIM6, a unique characteristic, is shown to affect mTORC2 assembly and its association with ribosomes. In addition, we identify that the BIA compound, a potentialTMBIM6 antagonist, prevents TMBIM6 binding to mTORC2, decreases mTORC2 activity, and also regulates TMBIM6-leaky Ca²⁺, further suppressing tumor formation and progression in cancer xenograft models. This previously unknown signaling cascade in which mTORC2 activity is enhanced via the interaction with TMBIM6 provides potential therapeutic targets for various malignancies.

TMBIM6, a member of the transmembrane BI-1 motif-containing family of proteins, is overexpressed in many cancer types. Here, the authors show that TMBIM6 regulates AKT activation through mTORC2 assembly and ribosome association and identify an antagonist of TMBIM6 with anti-tumor properties.