DNA Hypermethylation Inhibits the CD82 Metastasis Suppressor Gene in Gastric Cancer.

BACKGROUND/AIM: Gastric cancer, with its high global incidence and mortality rates, poses a significant challenge due to the rapid decline in patient survival upon metastasis. Understanding and combating metastasis are crucial in improving outcomes. The metastasis suppressor gene CD82 has demonstrated efficacy in inhibiting metastasis across various carcinomas but is frequently down-regulated. However, its role and regulatory mechanisms in gastric cancer remain elusive. MATERIALS AND METHODS: Utilizing public data, we assessed patient survival in relation to CD82 expression. CD82 expression in gastric cancer cell lines was evaluated via western blotting, and its impact on cell mobility was assessed through wound healing and Transwell assays. The demethylation of CD82 was induced using 5-aza-deoxycytidine, while methylation levels were detected via methylation-specific PCR. RESULTS: Low CD82 expression correlated with poor prognosis in patients, and down-regulation and over-expression of CD82 significantly affected cell mobility. Treatment with 5-aza-deoxycytidine restored CD82 expression in low-expressing cell lines, highlighting its methylation-dependent regulation. CONCLUSION: CD82 serves as a pivotal regulator of cell mobility in gastric cancer by suppressing metastasis. Its expression is attenuated in gastric cancer cells through promoter hypermethylation.

A Potential Role of CD82/KAI1 during Uterine Decidualization in Mice.

The tumor metastasis suppressor gene CD82/KAI1 has been demonstrated to impact human trophoblast invasion and migration. Communication between trophoblasts and decidual stromal cells plays a crucial role in controlling the normal invasiveness of trophoblasts. However, whether CD82/KAI1 is involved in decidualization and what role it plays remain unclear. CD82/KAI1 demonstrates specific spatiotemporal expression patterns in stromal cells undergoing decidualization during pregnancy. This is observed in both naturally pregnant females post-implantation and pseudopregnant mice undergoing induced decidualization, as detected through in situ hybridization and immunofluorescence. CD82/KAI1 expression showed a significant time-dependent increase in cultured stromal cells after 24 and 48 h of progesterone (P4) and estrogen (E2) treatment. This was accompanied by a notable upregulation of decidualization markers, including cyclin D3 and PR. After transducing stromal cells with the adenovirus-overexpressing CD82/KAI1 for 48 h, the expression of cyclin D3 protein increased. Meanwhile, there was an attenuated expression of CD82/KAI1 due to an adenovirus siRNA knockdown, whereas cyclin D3 and PR expressions were not affected. Our findings suggest a potential role of CD82/KAI1 in regulating the process of decidualization, providing insights into stromal cell differentiation.

Exosomal protein CD82 as a diagnostic biomarker for precision medicine for breast cancer.

CD82, a member of the tetraspanin superfamily, has been proposed to exert its activity via tetra-transmembrane protein enriched microdomains (TEMs) in exosomes. The present study aimed to explore the potential of the exosome protein CD82 in diagnosing breast cancers of all stages and various histological subtypes in patients. The results strongly suggest that CD82 expression in breast cancer tissue was significantly lower than that in healthy and benign breast disease tissues. There was a significant negative correlation between CD82 expression in tissues and CD82 content in exosomes, which indicated that CD82 expression was redistributed from tissues to the blood with the development and metastasis of breast cancer.

The metastasis suppressor CD82/KAI1 regulates cell migration and invasion via inhibiting TGF-ß 1/Smad signaling in renal cell carcinoma.

The tetraspanin KAI1/CD82 was identified as a tumor metastasis suppressor that downregulated in various malignant cell types. However, the function of CD82 and its underlying anti-metastasis role in renal cell carcinoma (RCC) is still unraveled. Here, we investigated the expression of CD82 in RCC and explored its regulatory mechanism in RCC cell lines. We found that CD82 was down-regulated in RCC tissues and cells and its expression was significantly associated with histological grade(p=0.041), tumour stage (p=0.036) and tumor size(p=0.020) by analyzing tissue microarrays. After upregulation of CD82 through lentivirus, reduced ability of migration and invasion in Caki-1 cells were detected. In contrast, gene silencing of CD82 by small interfering RNA promoted metastatic and invasive potential of 786-O cells. Furthermore, Western blot was performed to identify the influence of CD82 on MMP family and TGF-ß1/Smad pathway in RCC. Subsequently, upregulating protein level of TGF-ß1 with the overexpression of CD82 could rescue the malignant behaviors inhibited by CD82 which indicated that CD82 played its inhibitory role in RCC partially by attenuating the expression of TGF-ß1. Taken together, CD82 played a prominent role in migration and invasion of RCC cells and it might exhibit its inhibitory role in RCC metastasis via block TGF-ß1/Smad signaling pathway.

CD82/KAI1 Maintains the Dormancy of Long-Term Hematopoietic Stem Cells through Interaction with DARC-Expressing Macrophages.

Hematopoiesis is regulated by crosstalk between long-term repopulating hematopoietic stem cells (LT-HSCs) and supporting niche cells in the bone marrow (BM). Here, we examine the role of CD82/KAI1 in niche-mediated LT-HSC maintenance. We found that CD82/KAI1 is expressed predominantly on LT-HSCs and rarely on other hematopoietic stem-progenitor cells (HSPCs). In Cd82(-/-) mice, LT-HSCs were selectively lost as they exited from quiescence and differentiated. Mechanistically, CD82-based TGF-ß1/Smad3 signaling leads to induction of CDK inhibitors and cell-cycle inhibition. The CD82 binding partner DARC/CD234 is expressed on macrophages and stabilizes CD82 on LT-HSCs, promoting their quiescence. When DARC(+) BM macrophages were ablated, the level of surface CD82 on LT-HSCs decreased, leading to cell-cycle entry, proliferation, and differentiation. A similar interaction appears to be relevant for human HSPCs. Thus, CD82 is a functional surface marker of LT-HSCs that maintains quiescence through interaction with DARC-expressing macrophages in the BM stem cell niche.

Synergistic inhibition of cell migration by tetraspanin CD82 and gangliosides occurs via the EGFR or cMet-activated Pl3K/Akt signalling pathway.

The metastasis suppressor CD82/KAI-1, which is a member of the tetraspanin superfamily, has been proposed to exert its activity together with glycosphingolipids. However, the mechanism of CD82 inhibition has not been fully elucidated. The present study aimed to investigate the synergistic inhibition of cell migration by the tetraspanin CD82 and gangliosides and to correlate this inhibition with activation of epidermal growth factor receptor (EGFR) and hepatocyte growth factor receptor (HGFR/cMet) in Hepa1-6 cell lines, whose motility and migration is stimulated by epidermal growth factor (EGF) and hepatocyte growth factor (HGF) in vitro. We found that Hepa1-6 cells transfected with the CD82 gene exhibited decreased migration in response to EGF and HGF. EGF-stimulated phosphorylation of EGFR at Tyr1173 was inhibited in these cells, which contributed to the attenuation of EGFR. Ectopic expression of CD82 in Hepa1-6 cells inhibited HGF-stimulated tyrosine phosphorylation of cMet at Tyr1313 and Tyr1365 without affecting the expression of cMet. These inhibitory effects were enhanced when CD82 was introduced with Ganglioside GM3 alone or GM2/GM3. Reduction of CD82 expression by RNA interference together with depletion of glycosphingolipids with P4 significantly enhanced cell motility and increased the expression of EGFR and its phosphorylation at Tyr1173 in response to EGF. Increased cell motility and HGF-dependent activation of cMet at Tyr1313 and Tyr1365 resulted from decreased CD82 levels and increased GM3. Furthermore, CD82 expression selectively attenuated EGFR and cMet signalling via phosphatidylinositol 3-kinase/Akt but had no affect on the activity of the MAPK signalling pathway. These results suggest that the synergistic effects of CD82 and GM3 or GM2/GM3 on EGFR expression and phosphorylation and cMet activation are responsible for CD82 inhibition of EGF- and HGF-dependent cell motility and migration of Hepa1-6 cells.