Effects of isoprenylcysteine carboxyl methyltransferase silencing on the proliferation and apoptosis of tongue squamous cell carcinoma.

OBJECTIVES

This study aimed to explore the effects of silencing isoprenylcysteine carboxyl methyltransfe-rase (Icmt) through small interfering RNA (siRNA) interference on the proliferation and apoptosis of tongue squamous cell carcinoma (TSCC).

METHODS

Three siRNA were designed and constructed for the Icmt gene sequence and were then transfected into TSCC cells CAL-27 and SCC-4 to silence Icmt expression. The tested cells were divided as follows: RNA interference groups Icmt-siRNA-1, Icmt-siRNA-2, and Icmt-siRNA-3, negative control group, and blank control group. The transfection efficiency of siRNA was detected by the fluorescent group Cy3-labeled siRNA, and the expression of Icmt mRNA was screened by quantitive real-time polymerase chain reaction (qRT-PCR) selected the experimental group for subsequent experiments. The expression of Icmt, RhoA, Cyclin D1, p21, extracellular regulated protein kinases (ERK), and phospho-extracellular regulated protein kinases (p-ERK) were analyzed by Western blot. The proliferation abilities of TSCC cells were determined by cell counting kit-8 assay. The change in apoptosis was detected by AnnexinV-APC/propidium staining (PI) assay. Cell-cycle analysis was conducted by flow cytometry.

RESULTS

The expression of Icmt mRNA and protein in TSCC cells significantly decreased after Icmt-siRNA transfection (<0.05). No significant difference in RhoA mRNA and protein expression was detected (>0.05), but the expression of RhoA membrane protein decreased compared with the negative control group and blank control groups (<0.05). Cyclin D1 expression decreased, whereas p21 expression significantly increased and the relative expression of ERK protein in the experimental group did not significantly different that in the control group (>0.05). However, the phosphorylation level of ERK was significantly reduced (<0.05). The cell cycles of TSCC CAL-27 and SCC-4 were altered in G1/S, cell proliferation activity was inhibited, and apoptosis was induced (<0.05).

CONCLUSIONS

Silencing Icmt can effectively downregulate its expression in TSCC cells, reduce the RhoA membrane targeting localization and cell proliferation, and induce apoptosis. Thus, Icmt may be a potential gene therapy target for TSCC.