[CMTM3 regulates proliferation and migration of glioblastoma U251 cells via the NF-κB signaling pathway].

Objective: To explore the effects and potential mechanisms of chemokine-like factor-like MARVEL transmembrane domain-containing Protein 3 (CMTM3) on the proliferation and migration of glioblastoma (GBM) cells. Methods: Using CMTM3 expression data from The Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression (GTEx) databases, we analyzed the differential expression of CMTM3 in GBM tissues and its impact on the prognosis of GBM patients. Immunohistochemical staining and protein content determination of CMTM3 was performed on GBM and adjacent non-cancerous tissue samples from 11 GBM patients who underwent surgical treatment at the Affiliated Hospital of Guizhou Medical University between November 3, 2022 and March 15, 2023. Additionally, the expression of CMTM3 was validated in GBM cell lines U87, U251, LN229, and the human astrocyte (NHA) cell line using real-time quantitative polymerase chain reaction (RT-qPCR) and Western blot analyses. Stable cell lines with silenced and overexpressed CMTM3 (sh-CMTM3 group and OE-CMTM3 group) were constructed using U251 cells. The effect of CMTM3 expression on cell proliferation was assessed using the Cell Counting Kit-8 (CCK-8) assay. Flow cytometry was employed to examine the impact of CMTM3 expression on the cell cycle. Transwell assays were conducted to evaluate the influence of CMTM3 expression on cell migration. Bioinformatics analysis, Western blotting, NF-κB activation-nuclear translocation assays, and the NF-κB pathway inhibitor pyrrolidine dithiocarbamate ammonium (PDTC) were used to validate the effect of CMTM3 on the NF-κB pathway. Finally, a subcutaneous tumorigenesis assay in nude mice was performed to observe the impact of CMTM3 expression on the in vivo growth of U251 cells. Results: Bioinformatics analysis revealed that CMTM3 is highly expressed in GBM tissues. Patients with a high CMTM3 expression had lower overall survival (OS) and disease-free survival (DFS) rates compared with those with a low CMTM3 expression (with P values of 0.010 and 0.032, respectively). Among the 11 GBM pathological specimens, 10 samples exhibited higher CMTM3 protein expression levels in the cancerous tissue compared with the adjacent non-cancerous tissue. The average CMTM3 protein expression in these samples was 0.44±0.09, significantly higher than that in the adjacent non-cancerous tissues (0.12±0.02, P＜0.001). In one sample, the difference in CMTM3 protein expression between the cancerous and adjacent non-cancerous tissues was not statistically significant (P=0.750).The RT-qPCR results showed that the mRNA expression level of CMTM3 in NHA cells was 1.0±0.1, whereas in GBM cells U87, LN229, and U251, the levels were 2.1±0.3, 3.4±0.5, and 3.7±0.8, respectively, all significantly higher than that in NHA cells (all P＜0.01). Western blot results demonstrated that the protein expression levels of CMTM3 in GBM cells U87, LN229, and U251 were 1.5±0.2, 1.8±0.2, and 1.9±0.1, respectively, also higher than that in NHA cells (0.7±0.2, all P＜0.01), with the highest level observed in U251 cells. The CCK-8 assay, Flow cytometry, and Transwell migration experiments indicated that cell viability was inhibited in the sh-CMTM3 group, with an increase in the proportion of cells in the G₀/G₁ phase (P＜0.01) and a decrease in the S phase (P＜0.01), and the number of migrated cells was 233.6±35.5, lower than that in the sh-NC group (P＜0.001). Conversely, the OE-CMTM3 group showed enhanced cell viability, a reduction in the proportion of cells in the G₀/G₁ phase (P＜0.01), and an increase in the S phase (P＜0.01), and the number of migrated cells was 1212.0±20.8, higher than that in the OE-NC group (P＜0.001). However, in the OE-CMTM3+PDTC group, cell viability, cell cycle distribution (G₁, S, and G₂ phases), and cell migration numbers showed no significant changes (all P＞0.05). Western blot analysis and NF-κB activation-nuclear translocation assay results indicated that in the sh-CMTM3 group, the p-p65/p65 ratio was 0.51±0.04 and the p-IκBα/IκBα ratio was 0.39±0.03, both lower than those in the sh-NC group (both P＜0.01). The cytoplasmic staining rate was (49.29±1.98)%, higher than that in the sh-NC group (P＜0.01). In the OE-CMTM3 group, the p-p65/p65 ratio was 2.27±0.10 and the p-IκBα/IκBα ratio was 2.14±0.15, both higher than those in the OE-NC group (both P＜0.01). The cytoplasmic staining rate was (18.96±1.44)%, lower than that in the OE-NC group (P＜0.01). In the OE-CMTM3+PDTC group, there were no significant differences in the p-p65/p65 ratio, p-IκBα/IκBα ratio, and cytoplasmic staining rate compared with the OE-NC group (all P＞0.05). The subcutaneous tumorigenesis assay in nude mice showed that the tumor volume in the sh-CMTM3 group was (408.9±96.2) mm³, smaller than that in the sh-NC group (P=0.003). The tumor volume in the OE-CMTM3 group was (1 514.5±251.5) mm³, larger than that in the OE-NC group (P=0.005). Conclusions: In GBM, CMTM3 is highly expressed and negatively correlated with both OS and DFS of patients. CMTM3 regulates the proliferation and migration abilities of U251 cells through the NF-κB signaling pathway.