Oestrogen promotes tumorigenesis of bladder cancer by inducing the enhancer RNA-eGREB1

Abstract

In recent years, studies have shown that enhancer RNAs (eRNAs) can be transcribed from enhancers. Increasing evidence has revealed that eRNAs play critical roles in the development of various cancers. Oestrogen-associated eRNAs are closely related to breast cancer. In view of the gender differences in bladder cancer (BCa), we suppose that oestrogen-associated eRNAs are also involved in tumorigenesis of BCa. In our study, we first demonstrated that eGREB1 derived from the enhancer of an oestrogen-responsive gene-GREB1 was up-regulated in BCa tissues, and the expression level of eGREB1 is positively associated with the histological grade and TNM stage of BCa. Knockdown of eGREB1 by CRISPR-Cas13a could inhibit cell proliferation, migration and invasion and induce apoptosis in BCa cells T24 and 5637. Besides, we exhibited the promoting effect of oestrogen on BCa cells. What's more, down-regulation of eGREB1 could improve the malignant biological characteristics of BCa cells induced by oestrogen. In conclusion, our data indicated that eGREB1 plays oncogenic role and oestrogen may promote the occurrence and progression of BCa by inducing eGREB1 production. Our findings provide new insights into the prevention of BCa and develop a novel therapeutic target for the treatment of BCa.

Keywords: bladder cancer; eGREB1; enhancer RNAs; oestrogen.

Figure 1

(A) The relative expression levels of eGREB1 were measured by RT‐qPCR in 38 BCa patients. (B) The expression levels of eGREB1 were increased in BCa tissues compared to paired normal tissues. (C) There is no significant change in eGREB1 expression after transfection of siRNA. (D) eGREB1 expression was significantly down‐regulated by Cas13a‐eGREB1. (E) After stimulation with oestrogen for 1 h, the relative expression of eGREB1 was remarkably increased in BCa cells. Data are shown as mean ± SD (*P < 0.05, **P < 0.01, ***P < 0.001)

Figure 2

(A, B) Cell proliferation was detected by CCK8 in T24 and 5637 after transfection for 24 h. Knockdown of eGREB1 by Cas13a inhibited cell growth of BCa cells. (C‐E) Wound healing assay was used to measure cell migration. Down‐regulation of eGREB1 suppressed migration of BCa cells. (F, G) Down‐regulation of eGREB1 decreased cell invasion detected by transwell assays. (H) Down‐regulation of eGREB1 increased cell apoptosis measured by Caspase 3 ELISA assay. Experiments were performed in triplicate. Data were shown as mean ± SD (*P < 0.05, **P < 0.01)

Figure 3

(A, B) Oestrogen promoted cell proliferation and eGREB1 knockdown reduced the pro‐proliferative effects of oestrogen in T24 and 5637. (C‐E) Oestrogen facilitated cell migration of T24 and 5637. eGREB1 knockdown impaired cell migration induced by oestrogen. Experiments were performed in triplicate. Data were shown as mean ± SD (*P < 0.05, **P < 0.01, ***P < 0.001)

Figure 4

(A‐C) Oestrogen promoted the proliferation and down‐regulation of eGREB1 attenuated oestrogen‐induced invasion of BCa cells. (D) Oestrogen reduced BCa cell apoptosis. (E) eGREB1 knockdown with oestrogen treatment increased cell invasion compared to the control group. Experiments were performed in triplicate. Data were shown as mean ± SD (*P < 0.05, **P < 0.01, ***P < 0.001)