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Objective@#SET8 is a member of the SET domain-containing family and the only known lysine methyltransferase (KMT) that monomethylates lysine 20 of histone H4 (H4K20me1). SET8 has been implicated in many essential cellular processes, including cell cycle regulation, DNA replication, DNA damage response, and carcinogenesis. There is no conclusive evidence, however, regarding the effect of SET8 on radiotherapy. In the current study we determined the efficacy of SET8 inhibition on radiotherapy of tumors and the underlying mechanism.@*Methods@#First, we explored the radiotherapy benefit of the SET8 expression signature by analyzing clinical data. Then, we measured a series of biological endpoints, including the xenograft tumor growth in mice and apoptosis, frequency of micronuclei, and foci of 53BP1 and γ-H2AX in cells to detect the SET8 effects on radiosensitivity. RNA sequencing and subsequent experiments were exploited to verify the mechanism underlying the SET8 effects on radiotherapy.@*Results@#Low expression of SET8 predicted a better benefit to radiotherapy in lung adenocarcinoma (LUAD) and invasive breast carcinoma (BRCA) patients. Furthermore, genetic deletion of SET8 significantly enhanced radiation treatment efficacy in a murine tumor model, and A549 and MCF7 cells; SET8 overexpression decreased the radiosensitivity. SET8 inhibition induced more apoptosis, the frequency of micronuclei, and blocked the kinetics process of DNA damage repair as 53BP1 and γ-H2AX foci remained in cells. Moreover, RNF8 was positively correlated with the SET8 impact on DNA damage repair.@*Conclusion@#Our results demonstrated that SET8 inhibition enhanced radiosensitivity by suppressing DNA damage repair, thus suggesting that SET8 potentiated radiotherapy of carcinomas. As new inhibitors of SET8 are synthesized and tested in preclinical and clinical settings, combining SET8 inhibitors with radiation warrants consideration for precise radiotherapy.
Subject(s)
Animals , Humans , Mice , Apoptosis , Carcinogenesis , Carcinoma/radiotherapy , Cell Cycle , Cell Line, Tumor , DNA Damage , DNA Replication , HeLa Cells , Histone-Lysine N-Methyltransferase , RadiotherapyABSTRACT
Objective To investigate the effect of lysine methyltransferase SET8 on regulating cell transdifferentiation of rat vascular smooth muscle cells(VSMCs)into osteoblast-like cells. Methods VSMCs were obtained from rat thoracic aorta,and then randomly divided into control group(non-transfection),the empty plasmid group(transfect NS-shRNA)and SET8-shRNA group. The expression of SET8, runt-related transcription factor 2 (RUNX2) was detected by RT-PCR and Western blot assay. Alkaline phosphatase (ALP) activity was measured by enzyme linked immunoassay. Results The expression of SET8 in VSMCs was effectively inhibited by SET8-shRNA.RT-PCR and Western blot results showed that the expression of RUNX2 was decreased in cells after SET8-shRNA transfection (P<0.05). ALP activity was significantly reduced after SET8-shRNA transfection(P<0.05).Conclusion Interference with SET8 gene expression could inhibit the differentiation of VSMCs into osteo-like cells.
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Objective: To investigate the relationship between the expression of histone lysine methyltransferase SET8 protein and the prognosis of renal clear cell carcinoma. Methods: All of 100 patients with renal clear cell carcinoma who were confirmed by pathology and received nephrectomy in Fourth Hospital of Hebei Medical University from January 2008 to January 2012 were selected. The expression of SET8 protein in renal clear cell carcinoma tissues was detected by immunohistochemical mehtod. The correlation of SET8 protein expression rate with the clinicopathological characteristics (gender, year, TNM stage, tumor size and lymph node metastasis) and five-year survival rate of patients with renal clear cell carcinoma were analyzed. Results: The high expression rate of SET8 protein was 46.00% (46/100) in renal clear cell carcinoma tissues, and its expression was closely associated with tumor diameter and lymph node metastasis (both P 5 cm and the high expression of SET8 protein could increase the death risk of patients with renal clear cell carcinoma by 6.122 and 4.762 times, respectively (both P < 0.05). Conclusion: The high expression of SET8 protein is closely related to tumor diameter and lymph node metastasis of renal clear cell carcinoma, and it is an independent risk factor for the prognosis of patients with renal clear cell carcinoma.
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Objective The occurrence and progression of renal cell carcinoma ( RCC) is complicated process associated with DNA abnormal methylation , histone modification , and Wnt signaling pathway .This study aimed to investigate the expression of histone methylase SET8 in RCC, its relationship with the Wnt signaling pathway , its action mechanism in RCC , and its clinical significance . Methods We selected 50 cases of RCC treated by radical nephrectomy , detected the expression of SET 8 in the RCC and adjacent noncancerous kidney tissues by immunohistochemical EliVision two-step staining with β-catenin.We compared the expression levels of SET8 and β-catenin in the two types of tissue and analyzed their relationship with the patients′clinical information and the pathologic stage and grade of tumor as well as the correlation between the SET 8 andβ-catenin expressions . Results SET8 was mainly express in the cytoplasm of the RCC and noncancerous kidney tissues , partially in the cell membrane and nucleus , while theβ-catenin protein chiefly in the cell membrane of renal tubular epithelial cells in the normal kidney tissue .The expression levels of SET 8 and β-catenin in the RCC tissue were closely related to the TNM stage and tumor grade (P0.05), but that of β-catenin was remarkably higher in the former (68%[34/50]) than in the latter (4%[2/50]) (P<0.01).There was a positive correlation between the positive expression of SET 8 and the abnormal expression of β-catenin (r=0.219, P<0.05). Conclusion SET8-activated H4K20me-1 controls the activation and abnormal activities of the Wnt signaling pathway , affects the gene transcription and cell activity , and participates in the occurrence , progression, and distant metastasis of RCC .