Isoprenylcysteine carboxyl methyltransferase promotes the progression of tongue squamous cell carcinoma via the K-Ras and RhoA signaling pathways

OBJECTIVE

This research investigated the biological role of isoprenylcysteine carboxyl methyltransferase (ICMT) in tongue squamous cell carcinoma (TSCC) progression meanwhile to explore the conceivable mechanism.

METHODS

The mRNA and protein expression were measured using real-time PCR and Western blot. Cell proliferation, apoptosis, cycle distribution, migration and invasion were evaluated by CCK-8 assay, flow cytometry, wound-healing assay and transwell assay. The anti-tumor activity of ICMT silencing was observed in nude mice.

RESULTS

Our results indicated that silencing of ICMT-mediated methylation effectively inhibited TSCC cells proliferation in vitro and reduced tumor growth in vivo. Moreover, ICMT knockdown also induced cell apoptosis and cell cycle arrest of both CAL-27 and SCC-4 cells. In addition, CAL-27 and SCC-4 cells migration and invasion were weakened by ICMT siRNA. Mechanistically, ICMT deficiency significantly decreased the K-Ras and RhoA membrane targeting localization, leading to the suppression of K-Ras- and RhoA-mediated downstream signaling in CAL-27 and SCC-4 cells.

CONCLUSIONS

Altogether, our findings identified a crucial role played by ICMT in the progression of TSCC and the potential mechanisms by which exerted its effects, indicating that targeting ICMT may represent a promising therapeutic strategy for TSCC.

Isoprenylcysteine carboxyl methyltransferase inhibitors exerts anti-inflammatory activity

Isoprenylcysteine carboxylmethyltransferase (ICMT) has been reported to regulate the inflammatory response through the Ras/MAPK/AP-1 pathway. Nevertheless, the potential of ICMT inhibitors as therapeutic agents against inflammatory diseases has not been examined. Therefore, in this study, we investigated the anti-inflammatory properties of two ICMT inhibitors, cysmethynil (CyM) and 3-methoxy-N-[2-2,2,6,6-tetramethyl-4-phenyltetrahydropyran-4-yl)ethyl]aniline (MTPA), using in vitro analyses and in vivo analyses (lipopolysaccharide (LPS)/D-GalN-triggered hepatitis and DSS-induced colitis mouse models). CyM and MTPA inhibited the production of nitric oxide (NO) and prostaglandin E (PGE)₂ and the expression of cyclooxygenase (COX)-2, tumor necrosis factor (TNF)-α and interleukin (IL)-1β in LPS-induced RAW264.7 cells and peritoneal macrophages without cytotoxicity. CyM also reduced AP-1-mediated luciferase activity in LPS-stimulated RAW264.7 cells and MyD88- and TRIF-expressing HEK293 cells. In addition, CyM and MTPA suppressed the translocation of Ras to the cell membrane and ER as well as phosphorylation of Ras-dependent AP-1 signaling molecules including Raf, MEK1/2, ERK p38, and JNK. Consistent with these results, CyM diminished the expression of inflammatory genes (COX-2, TNF-α, IL-1β, and IL-6), AP-1-Luc activity, and phosphorylation of Ras-mediated signaling enzymes in Ras-overexpressing HEK 293 cells. Moreover, CyM and MTPA ameliorated symptoms of hepatitis and colitis in mice and restrained the ICMT/Ras-dependent AP-1 pathway in inflammatory lesions of the mouse model systems. Taken together, our results indicate that CyM and MTPA alleviate the LPS-induced ICMT/Ras/AP-1 signaling pathway, thereby inhibiting the inflammatory response as promising anti-inflammatory drugs.