The Clinical Prognostic Value Of DOT1L Expression In Colorectal Cancer Patients And Its Effect On The Proliferation And Apoptosis Of Colorectal Cancer Cells

[Objective]DOT1L is a class of histone lysine methyltransferase,which can specifically methylate H3K79.DOT1L expression and H3K79me2 status are considered to be related to the development of tumors.In this study,we detected the expression of DOT1L and H3K79me2 to analyse their relationship with clinicopathological parameters and prognosis in colorectal cancer(CRC)patients.Moreover,we detected their expression in eight CRC cell lines and investigate their effects on proliferation and apoptosis of these cells.[Methods]We firstly refered to DOT1L expression and its relationship with prognosis in CRC patients from the public database.Secondly,we examined the expression levels of DOT1L and H3K79me2 by immunohistochemistry(IHC)to analyse its relationship with the clinicopathological characteristics and prognosis in 78 CRC patients.Protein levels and mRNA expression of DOT1L in CRC cell lines were detected by western blot(WB)and qRT-PCR,and protein expression of H3K79me2 was detected by WB as well.We also use flow cytometry to detect the proportion of H3K79me2 positive cells.Then CCK8 and flow cytometry were used to investigate the effect on proliferation and apoptosis after DOT1L was inhibited.[Results]According to the public database,protein levels and mRNA expression of DOT1L in CRC tissues were higher than that of most other tumors,and high DOT1L expression was related to the poor prognostis.In the study of 78 CRC patients,DOT1L expression in CRC tissues was much higher than that in normal tissues(P<0.001),and so was H3K79me2(P<0.001).DOT1L expression in CRC tissues was correlated with differentiation,T stage and N stage(P<0.05).and H3K79me2 expression was correlated with T stage,N stage and TNM stage(P<0.05).There was a obviously positive correlation between DOT1L and H3K79me2 expression(r=0.570,P=0.01).Survival rates of CRC patients with high expression of DOT1L and H3K79me2 were significantly lower than those with low expression(P<0.05),and multivariate analysis suggested that the expression of DOT1L and H3K79me2 were independent prognostic factors in CRC patients.In the study of eight CRC cell lines,Protein levels and mRNA expression of DOT1L were detected in each cell lines,and the proportion of H3K79me2 positive cells was high in most cell lines.The cell proliferation was significantly inhibited by DOT1L inhibitor SGC0946 in most CRC cell lines,but the apoptosis was not affected or slight affected.[Conclusions]The expression of DOT1L and H3K79me2 were closely related to the clinical characteristics and prognosis in CRC patients,and the proliferation was inhibited by DOT1L inhibitor in most cell lines.In conclusion,the high expression of DOT1L and H3K79me2 can promote the development of CRC,and can be used as an important prognostic indicator for colorectal cancer.