YAP is overexpressed in clear cell renal cell carcinoma and its knockdown reduces cell proliferation and induces cell cycle arrest and apoptosis

Abstract

Yes-associated protein (YAP) has been reported to be an oncogene in a number of malignancies. It constitutes an important regulatory mechanism for the Hippo pathway, a key regulator of cell growth and apoptosis. The present study aimed to investigate the clinical significance and the role of YAP in the development of clear cell renal cell carcinoma (ccRCC). YAP expression levels were compared between ccRCC and adjacent normal renal tissues by RT-PCR and immunohistochemistry, respectively. YAP expression levels were then detected in ccRCC cell lines 786-0 and ACHN, as well as in human embryonic kidney 293 cells (HEK-293) using western blotting. Three specific YAP-shRNA lentiviral vectors were constructed and transfected into 786-0 cells, and then the mRNA and protein levels of YAP and downstream transcription factor TEAD1 were detected. Finally, the effects of YAP silencing on proliferation and the cell cycle distribution of 786-0 cells were detected by Cell Counting Kit-8 (CCK-8) and flow cytometry (FCM), respectively. The apoptosis rate was also analyzed by FCM. It was observed that the expression levels of YAP mRNA and protein in ccRCC tissues were higher than these levels in the adjacent normal renal tissues. The expression of YAP protein in ccRCC tissues was significantly correlated with clinical stage and differentiation. The YAP protein levels in the two ccRCC cell lines 786-0 and ACHN were significantly higher than that in the HEK-293 cells. Additionally, treatment of 786-0 cells with YAP-shRNA lentiviral vectors significantly reduced the expression levels of YAP and TEAD1 mRNA and protein. Further analyses in 786-0 cells in which YAP was decreased, revealed that cell proliferation was inhibited, cell cycle was arrested at the G1 phase and apoptosis was increased. These results indicate that YAP is an underlying oncogene in ccRCC and it may be a promising biomarker and therapeutic target of ccRCC.

YAP1 enhances cell proliferation, migration, and invasion of gastric cancer in vitro and in vivo

“…Taken together with these previous studies, our results suggest that silencing YAP1 increase the expression of α-catenin possibly by a negative feedback effect. In addition, the cell cycle results of the present study are consistent with those observed in different cancers (clear cell renal cell carcinoma [26], osteosarcoma [27], and GC [12]). It has been reported that accumulation of G1 cells was increased in MKN1 and AGS GC cells in which YAP1 expression was silenced [12].…”

Overexpression of the YAP1 oncogene in clear cell renal cell carcinoma is associated with poor outcome

“…Despite the mentioned differences, Cao et al obtained comparable results since the increased YAP1 protein level was associated with higher Fuhrman's and clinical stages (54). They also performed in vitro studies on 786-O and HEK293 kidney cells and found that knockdown of YAP1 inhibited expression of the TEAD1 gene as well as suppressed cell proliferation (54). Most studies on the role of YAP1 in other cancer types such as RCC (39), oral squamous cell carcinoma (55), ovarian cancer (56), head and neck cancer (57), colorectal cancer (58), melanoma (59), lung (18) and breast cancer (23), revealed an association between YAP1 overexpression (mostly at the protein level) and tumor progression.…”

“…Therefore, in this study we aimed to assess the possible role of YAP1 in ccRCC. Although our report is not the first study of YAP1 expression in ccRCC since Cao et al published a similar study in 2014 (54), there are some significant differences: a larger group of patients (86 vs. 30 persons), study on metastasized samples, modern quantitative techniques (qPCR vs. classical PCR) and survival data. Despite the mentioned differences, Cao et al obtained comparable results since the increased YAP1 protein level was associated with higher Fuhrman's and clinical stages (54).…”

“…Although our report is not the first study of YAP1 expression in ccRCC since Cao et al published a similar study in 2014 (54), there are some significant differences: a larger group of patients (86 vs. 30 persons), study on metastasized samples, modern quantitative techniques (qPCR vs. classical PCR) and survival data. Despite the mentioned differences, Cao et al obtained comparable results since the increased YAP1 protein level was associated with higher Fuhrman's and clinical stages (54). They also performed in vitro studies on 786-O and HEK293 kidney cells and found that knockdown of YAP1 inhibited expression of the TEAD1 gene as well as suppressed cell proliferation (54).…”

Hippo signaling in the kidney: the good and the bad

“…Yap mRNA and protein expression levels are also increased in ccRCC tissue and cell lines. Furthermore, Yap silencing in 786-0 ccRCC lines results in cell cycle arrest and increased apoptosis (6). Targeted deletion of the Nf2 gene that encodes the upstream Hippo pathway regulator Merlin in proximal convoluted epithelium results in intratubular neopla-sia that progresses to invasive carcinoma (43).…”