The Expression Of SETD2 In Renal Cell Carcinoma:Correlation With Clinical Significance

Background:SET domain-containing protein 2(SETD2) as a member of superfamily of lysine methyltransferases was first discovered in 1998. The important role of SETD2 in some human malignant tumors such as lymphoblastic leukaemia; high-grade astrocytomas, non-small cell lung carcinomas, human breast cancer was gradually discovered these years.Clear cell RCC (ccRCC) as the most common subtype accounting for 80-90% of RCCs. Systematic sequencing in recent studies have identified recurrent mutations in histone modifying gene SETD2 (3-12%) in sporadic ccRCC patients. Subsequent research discovered SETD2 mutations (6%-12%) is likely to associated with worse cancer-specific survival (CSS) and poor overall survival (OS) but the sample size is small and the outcomes in different studys is contradictory.SETD2 as a Histone-lysine N-methyltransferase is responsible for lysine-36 of histone H3 (H3K36) trimethylation(H3K36me3) through the SET domain. H3K36me3 is associated with active transcription through recruitment of a histone deacetylase complex and also participate in hyperphosphorylation of RNA polymerase Ⅱ which involves in transcriptional elongation. And SETD2 and H3K36me3 may play directly or indirectly role in the occurrence and development of ccRCC.The studies about clinical and pathological impact of SETD2 in ccRCC are fairly scant and inconsistent. The mechanism and downstream pathways of SETD2 mutation causing ccRCC remains unclear.Objective:Investigate and compare the expression of SET domain containing protein 2 (SETD2) in renal cell carcinoma patients in QiLu hospital and Weihai city hospital Hospital urology department. Discuss the possible mechanism and clinical significance between SETD2, H3K36me3 and renal cell carcinoma.Methods:1. Subjects:Collect the RCC tumor tissues from 135 cases from surgical patients in urology department of QiLu Hospital and Weihai city hospital. The data of 500 RCC cases in TCGA(The Cancer Genome Atlas).2. Test:(1) Immunohistochemistry (IHC) was used to detect the expression of SETD2 protein and its modified productin H3K36me3. To clarify its localization in carcinoma tissues.(2) Statistical method was used to analyze the relationship between protein expression of tumor suppressor gene SETD2, H3K36me3 and the clinical and pathological parameters such as clinical stage, nuclear grading and prognosis.(3) Apply statistics to compare the SETD2 mutations and the clinical parameters of RCC cases in TCGA (The Cancer Genome Atlas) database.Results:1. Immunohistochemistry results showed SETD2 expressed in renal clear cell cancer cells within the nucleus. And the expression is heterogeneity. Its express negative rate is 34.5%.2. Immunohistochemistry and statistics results showed the high expression of protein of SETD2 is associated with higher malignant degree, poor OS and PFS.3. TCGA database hints that RCC combine with SETD2 mutation is associatied with poor OS which is in conformity with the experimental results.4. The correlativity between SETD2 protein expression and H3K36me3 expression is not high (P= 0.066).5. There is no significant correlation between H3K36me3 expression and prognosis of RCC (P= 0.8018).Conclusion:1. This study demonstrated that SETD2 expression levels, and predict poor prognosis in ccRCC patients in two independent cohorts, and validated by a large cohort from TCGA. These findings are consistent with the tumor suppressor function of SETD2.2. There may be other factors lead to three methylation modification of H3K36. SETD2 may inhibit kidney cancer through other than H3K36 three methylation modification pathway.3. SETD2 can be used as independent prognostic factor for kidney and the mechanism of SETD2 mutations lead to kidney cancer is still not clear.