MYO5B Is Epigenetically Silenced and Associated with MET Signaling in Human Gastric Cancer
Our previous study has shown that MYO5B is downregulated in gastric cancer. However, the mechanism by which the expression of MYO5B was inhibited remains unknown.
Inspection of the human MYO5B locus uncovered a large and dense CpG island within the 5′ region of this gene. Methylation-specific PCR (MSP) and bisulfite sequencing (BSP) were used for determination of MYO5B promoter methylation in gastric cancer cell lines and gastric cancer samples. Involvement of histone H3 methylation in those cell lines were examined by ChIP assay.
The densely methylated MYO5B promoter region was confirmed by MSP and BSP. Enhanced gene expression was detected when the cells were treated with the DNA-demethylating agent 5-aza-2′-deoxycytidine (DAC) and trichostatin A (TSA), a histone deacetylase inhibitor. Knockdown of MYO5B expression in gastric cancer cells expressing endogenous MYO5B inhibits HGF-stimulated MET degradation, concomitant with sustained c-MET levels and signaling.
The results of our study showed for the first time that MYO5B is epigenetically silenced in gastric cancer cells by aberrant DNA methylation and histone modification. Inactivation of MYO5B expression in gastric cancer cells expressing endogenous MYO5B inhibits HGF-stimulated MET degradation, concomitant with sustained c-MET levels and signaling.
KeywordsMYO5B MET Methylation Gastric cancer
This work was supported by the youth innovation fund of the first affiliated hospital of Zhengzhou University.
Conflict of interest
After treatments with DAC or/and TSA, the MKN45 and MKN28 cells were harvested. The protein levels of MYO5B were determined by Western blot, with Actin serving as internal control.
Immunohistochemical staining for MYO5B with anti- MYO5B in the 4 gastric cancer tissues (T6, T13, T35 and T60). The nuclei were countered stained with hematoxylin. Case numbers are shown on top. (B) Demonstration of MYO5B promoter methylation by sequencing of sodium bisulfite–modified DNA from the 4 cancerous tissues. The case numbers are shown on left.