KAT5 and KAT6B are in positive regulation on cell proliferation of prostate cancer through PI3K-AKT signaling

Abstract

Histone modifications play important roles in the tumorigenesis and progression of prostate cancer (PCa) and genes involved in histone modifications are seemed as ideal targets for treatment of PCa patients. However, clinical trials have shown that those existing drugs exert the minimal antitumor activity and excess adverse effects on PCa patients. Therefore, it is of great interest to figure out novel specific biomarkers to guide the development of new drugs. In present study, an RNAi screening with 44 genes involved in histone modifications was applied to a PCa cell line, Du145. The results showed that nine genes were in positive regulation of Du145 cell growth. Then four selected genes (KAT2B, KAT5, KAT6B and HDAC1) were found to exert this effect by a gene-specific manner when silenced. And then KAT5 or KAT6B silenced cells were subjected to DNA microarray analysis. The common differentially expressed genes were analyzed by Ingenuity Pathway Analysis (IPA) and found that PDEF signaling, EIF2 signaling and PI3K signaling was suppressed following by KAT5 or KAT6B silencing. Subsequent immunoblotting assay showed that AKT signaling was inhibited, which suggested that KAT5 or KAT6B regulates cancer cell growth through PI3K-AKT signaling. Together with our published data [31] that AURKA inhibitoin increased drug sensitivity of DU145, our work demonstrated the underlying mechanism that how the acetylation enzyme regulates cancer cells survial and might provide potential therapeutic targets for prostate cancer patients in future epigenetic drug development.

Keywords: KAT5; KAT6B; PI3K-AKT signaling; Prostate cancer; RNAi screening; histone modifications.

Figure 1

RNAi screening in Du145 cells. A: Primary screening results. shRNA library of 44 genes involved in histone modifications was applied to Du145 cells, the cell viability was detected by MTS assay and plotted. The red line in figure represented the relative cell viability was 0.8; dots under the red line represented the positive hits in screening. B: Histogram shown the relative cell viability of the positive hits.

Figure 2

Four genes-specific knockdown inhibits the growth of Du145 cells. A: Cell viability following each gene silencing. B: Relative expression of each gene after it was silenced by the corresponding shRNAs.

Figure 3

PI3K signaling was predicted to be suppressed following KAT5/KAT6B silencing. Based on the downregulation of PIK3CA when KAT5/KAT6B silenced, IPA predicted that the downstream AKT, ERK and NF-κB signaling were all inhibited, and hence repressed Du145 cell growth.

Figure 4

Immunoblotting of AKT/p-AKT for KAT5/KAT6B silenced cells. Proteins from cells treated with negative control (NC) shRNAs or KAT5/KAT6B shRNAs were used to investigate the protein expression of phosphorylation of AKT. The total AKT protein and GAPDH were used as loading control.