AU-1 from Agavaceae plants causes transient increase in p21/Cip1 expression in renal adenocarcinoma ACHN cells in an miR-34-dependent manner

Abstract

Here, we show that AU-1, spirostanol saponin isolated from Agavaceae plants, causes a transient increase in cyclin-dependent kinase inhibitor (CDKI) p21/Cip1 through the upregulation of miRNAs, miR-34 and miR-21. AU-1 stimulated p21/Cip1 expression without exerting cytotoxicity against different types of carcinoma cell lines. In renal adenocarcinoma ACHN cells, AU-1 transiently elevated the expression level of p21/Cip1 protein without marked increases in p21/Cip1 mRNA levels. Rapid and transient increases in miR-34 and miR-21, both of which are known to upregulate p21/Cip1, were observed in AU-1-treated cells. Inhibitor for miR-34 and for miR-21 significantly blocked the AU-1-caused increase in p21/Cip1, indicating that elevation of p21/Cip1 protein by AU-1 is dependent on these microRNAs. We further clarified that NAD-dependent deacetylase SIRT1, a direct target of miR-34, is decreased by the treatment with AU-1. Furthermore, we found that SIRT1-knockdown increases p21/Cip1 protein levels in an miR-21-dependent manner. On the other hand, ectopic expression of p21/Cip1 resulted in the lowered expression of miR-34 and miR-21, suggesting that reciprocal regulation exists between p21/Cip1 and these miRNAs. We propose that the following feedback network composed of miR-34/SIRT1/miR-21/p21 is triggered by the treatment with AU-1: in cells treated with AU-1, transient elevation of miR-34 leads to the downregulation of SIRT1, thereby miR-21 is freed from SIRT1-dependent suppression. Then, elevated miR-21 upregulates p21/Cip1 protein, followed by the suppression of miR-34 expression.

Exportin 1 (XPO1) inhibition leads to restoration of tumor suppressor miR-145 and consequent suppression of pancreatic cancer cell proliferation and migration

“…The let-7 and miR-34 miRNA families are down-regulated in PDAC [ 49 , 50 ]. Studies found that both let-7 and miR-34 could contribute to the up-regulation of p21 WAF1 , leading to cell cycle arrest and inhibition of cell proliferation [ 51 , 52 ]. In addition, selinexor has been found to increase the expression and nuclear accumulation of p53 [ 53 , 54 ] which, in turn, induces p21 WAF1 .…”

Cyclin-dependent kinase inhibitor p21/Cip1 down-regulates the expression of proteasome activator PA28γ in normal hepatocyte-derived cells

“…Therefore, in hepatocellular carcinoma cells, FXR knockdown-mediated up-regulation of p21/Cip1 mRNA expression results in an increase in p21/Cip1 protein levels. In normal hepatocyte-derived cells, p21/Cip1 does not down-regulate miR-34 (Fujino et al, 2017). Moreover, although SIRT1 level are reduced by FXR knockdown in a miR-34-dependent manner, SIRT1 down-regulation does not cause an increase in p21/Cip1 levels (Fujino et al, 2018).…”

“…Importantly, we previously reported that p21/Cip1 protein down-regulates its own expression in microRNA miR-34-and NAD + -dependent deacetylase SIRT1-dependent manner (Fujino et al, 2017). That is, p21/Cip1 down-regulates the expression of miR-34, resulting in an increase in SIRT1, a direct target of miR-34 (Yamakuchi et al, 2008), and SIRT1 reduces p21/Cip1 protein levels.…”

MicroRNA-34a: A Versatile Regulator of Myriads of Targets in Different Cancers

“…Since EMT has been implicated in cancer metastasis and resistance to therapy, this is an exciting observation that needs to be further tested in pre-clinical models. Further, AU-1, a spirostanol saponin present in Agavaceae plants, was noted to inhibit SIRT1 (silent expression regulator-1), an NAD-dependent deacetylase [ 30 ]. AU-1 upregulated miR-34 to effectively reduce SIRT1 levels in renal adenocarcinoma ACHN cells.…”

“…AU-1 upregulated miR-34 to effectively reduce SIRT1 levels in renal adenocarcinoma ACHN cells. SIRT1-knockdown induced transient but significantly increased p21/Cip1 protein levels [ 30 ]. Please check and confirm.…”