Analysis Of Promoter Methylation Status And Expression Of RASSF2A Gene In Renal Cell Carcinoma

Objective: Renal Cell Carcinoma(Renal Cell Carcinoma,RCC)is one of the most common malignant tumor in urinary system,and it is a serious threat to the health of the people in our country.With the deepening research on tumor etiology,people find that epigenetics plays a very important role in tumor procession.Epigenetics mainly includes DNA methylation,histone modification,chromatin remodeling,RNA interference,genetic imprinting and random chromosome inactivation(X).At present,there is a deep understanding of the relationship between tumor suppressor gene DNA promoter methylation and tumor.It has been confirmed that RASSF2 A gene promoter methylation is one of the reasons for the occurrence and development of nasopharyngeal carcinoma,mammary cancer and other malignant tumors.Whether RASSF2 A methylation is related to RCC has not been reported.The object of this experiment is to explore the relationship between the RASSF2 A gene and tumor accurance by detecting RASSF2 A gene mRNA expression levels and its promoter region methylation status in RCC tissue,tumor-adjacent tissues and normal kidney tissues,and to provide theory basis for early diagnosis and treatment of RCC.Methods:The RASSF2 A gene promoter methylation status in 60 cases of RCC tissues,tumor-adjacent tissues and normal kidney tissues were examined by Methylation-specific PCR(Methylation Specific PCR,MSP).RASSF2 A gene mRNA relative expression quantity in RCC tissues,tumor-adjacent tissues and normal kidney tissues were examined by reverse transcription-PCR(RT-PCR).At the same time,processing the results by statistical software SPSS20.0 and analysising the relationship between the results and clinical data.Results:1 There were three methylation state of RASSF2 A gene in RCC tissues,tumor-adjacent tissues and normal kidney tissues: unmethylated state,hemimethylated state and methylated state.2 Positive rate of RASSF2 A gene promoter methylation in 60 cases of RCC tissues,tumor-adjacent tissues and normal kidney tissues were 36.7%(22/60),13.3%(8/60),11.7%(7/60),RCC tissues methylation positive rate was significantly higher than the tumor-adjacent tissue(χ2=8.711 P=0.003)and the normal kidney tissues(χ2=10.231 P=0.001);There was no significant difference between tumor-adjacent tissues and normal kidney tissues in the methylation positive rate(χ2=0.076 P=0.783).In the 60 RCC tissues,there was no obviously relationship between RASSF2 A promoter methylation state and gender(χ2=0.191 P=0.662),age(χ2=0.463 P=0.496),tumor diameter(χ2=0.301 P=0.583),Fuhrman nuclear classification(χ2 =0.935 P=0.621);but,related to smoking(χ2=6.962 P=0.008),clinical stage(stage I,II and III,IV)(P=0.003).3 The relative expression quantity of RASSF2 A mRNA in 60 cases of RCC tissues,tumor-adjacent tissues and normal kidney tissues were 0.35±0.07,0.55±0.09,0.59±0.09.It was obviously that RASSF2 A mRNA relative expression quantity in RCC tissues was lower than in tumor-adjacent tissues(P=0.000)and normal kidney tissues(P=0.000).However,the RASSF2 A mRNA relative expression quantity in tumor-adjacent tissues and normal kidney tissues has no significant difference(P=0.247).In the 60 RCC tissues,there was no obviously relationship between RASSF2 A m RNA relative expression quantity and gender(t=0.624,P=0.538),age(t=-0.392,P=0.698),tumor size(t=-0.328,P=0.745);but,related to smoking(t=-3.186,P=0.002),clinical stage(stage I,II and III,IV)(t=-3.592,P=0.001).4 The relative expression quantity of RASSF2 A in methylation group was 0.37±0.07,which was lower than in unmethylation group 0.57±0.11.There was significant difference between methylation group and unmethylation group.Conclusions:1 The hypermethylation of RASSF2 A gene promoter is a frequent event in RCC.Epigenetic inactivation of RASSF2 A gene may play an important role in the formation of RCC.2 RASSF2 A mRNA relative expression quantity in RCC tissues was lower than in tumor-adjacent tissues and normal kidney tissues.The result suggests that downregulation of the RASSF2 A gene expression may cause the tumorigenesis of RCC.3 The relative expression quantity of RASSF2 A mRNA in methylation group was lower than that in unmethylation group.The result suggests that RASSF2 A gene promoter region hypermethylation could be the main reason for its transcriptional silencing.