Promoter methylation and expression of Raf kinase inhibitory protein in esophageal squamous cell carcinoma

Abstract

Abstract. Raf kinase inhibitory protein (RKIP) regulates multiple cellular processes, and its downregulation is associated with distinct human cancers. In the present study, the status of RKIP promoter methylation, as well as its expression and clinical significance in esophageal squamous cell carcinoma (ESCC), were examined. The promoter methylation status in the 5'-CpG island of the RKIP gene and the expression level of the RKIP protein were examined using a modified methylation-specific polymerase chain reaction (MSP) method and immunohistochemical staining, respectively, in 77 ESCC samples and matched paratumor normal tissues. The incidence of RKIP promoter methylation was significantly higher in tumor samples (75.3%) than in the matched normal tissues (27.3%; P<0.001). A higher incidence of promoter methylation was also detected in poorly differentiated cancers (93.5%) compared with well-differentiated cancers (50.0%; P<0.001), as well as in tumor samples with positive lymph node metastasis (86.7%) compared with those with negative lymph node metastasis (59.4%; P<0.001). Consistent with the promoter methylation status, the expression level of RKIP was significantly reduced in cancer tissues (36.4%) compared with matched normal tissues (76.6%; P<0.01), as well as in cancers with positive lymph node metastasis (24.4%) compared with those with negative lymph node metastasis (53.1%; P=0.01). Promoter methylation-induced gene silencing significantly correlated with the down regulation of RKIP and the development of ESCC. The results of the present study suggested that the methylation status of the RKIP promoter, when combined with its expression level, may serve as a biomarker for predicting the biological behaviors of ESCC.

RAF Kinase Inhibitor Protein in Myeloid Leukemogenesis

“…Particularly, the absence of hypermethylation within the RKIP promoter is of therapeutic relevance, as this suggests that demethylating agents, including azacitidine and decitabine, do not display a promising therapeutic approach to restore RKIP expression. These data are in contrast to results from several solid tumors, where hypermethylation of RKIP has been demonstrated [68,69,70], and that show that the reasons for RKIP loss might be tissue-specific. To shed more light on the reasons for RKIP loss in AML, we screened for the deregulation of micro-RNAs (miRs).…”

RKIP: A Key Regulator in Tumor Metastasis Initiation and Resistance to Apoptosis: Therapeutic Targeting and Impact

“…RKIP loss also serves as a predictive marker for the progression and metastasis of liver [ 226 , 227 ], kidney [ 228 ], breast [ 229 ], ovarian [ 230 ], and colorectal cancers [ 231 ], as well as pancreatic ductal adenocarcinoma (PDAC) [ 232 ]. Combined with its promoter’s methylation, RKIP expression was further suggested as a biomarker of ESCC [ 233 ]. Phospho-RKIP was also reported as a predictive indicator of survival in lung cancer [ 234 ].…”

Targeting Raf Kinase Inhibitory Protein Regulation and Function

“…Promoter methylation: Promoter methylation is a well-characterized mechanism for epigenetic silencing by which gene transcription is halted through transcription factor inaccessibility, without any genetic alterations. Several studies of tumors, including gastric adenocarcinomas [ 18 , 19 ], esophageal squamous cell carcinomas [ 20 , 21 ], colorectal cancers [ 22 , 23 ], and breast cancers [ 24 ], reported that methylation status of the RKIP promoter determined by MSP (methylation specific PCR) strongly correlated with low RKIP expression levels in various advanced stages of the tumors. In gastric and esophageal cancers, carcinoma tissue showed significantly higher incidence rates of hypermethylated RKIP promoters than the adjacent normal mucosal tissue [ 19 , 21 ].…”

“…In gastric and esophageal cancers, carcinoma tissue showed significantly higher incidence rates of hypermethylated RKIP promoters than the adjacent normal mucosal tissue [ 19 , 21 ]. In esophageal cancers, methylated promoter status also correlated with poorly differentiated tumors, as well as lymph node metastases [ 21 ]. In agreement with these findings, patients whose tumors had hypermethylated RKIP showed worse overall survival rates compared to unmethylated RKIP cases in gastric cancers [ 19 ], implicating RKIP as an independent prognostic marker for survival.…”