Vorinostat Enhances Cytotoxicity of SN-38 and Temozolomide in Ewing Sarcoma Cells and Activates STAT3/AKT/MAPK Pathways

Abstract

Histone deacetylase inhibitors (HDACi) have been evaluated in patients with Ewing sarcoma (EWS) but demonstrated limited activity. To better understand the potential for HDACi in EWS, we evaluated the combination of the HDACi vorinostat, with DNA damaging agents SN-38 (the active metabolite of irinotecan and topoisomerase 1 inhibitor) plus the alkylating agent temozolomide (ST). Drugs were evaluated in sequential and simultaneous combinations in two EWS cell lines. Results demonstrate that cell viability, DNA damage and reactive oxygen species (ROS) production are dependent on the sequence of drug administration. Enhanced cytotoxicity is exhibited in vitro in EWS cell lines treated with ST administered before vorinostat, which was modestly higher than concomitant treatment and superior to vorinostat administered before ST. Drug combinations downregulate cyclin D1 to induce G0/G1 arrest and promote apoptosis by cleavage of caspase-3 and PARP. When ST is administered before or concomitantly with vorinostat there is activation of STAT3, MAPK and the p53 pathway. In contrast, when vorinostat is administered before ST, there is DNA repair, increased AKT phosphorylation and reduced H2B acetylation. Inhibition of AKT using the small molecule inhibitor MK-2206 did not restore H2B acetylation. Combining ST with the dual ALK and IGF-1R inhibitor, AZD3463 simultaneously inhibited STAT3 and AKT to enhance the cytotoxic effects of ST and further reduce cell growth suggesting that STAT3 and AKT activation were in part mediated by ALK and IGF-1R signaling. In summary, potent antiproliferative and proapoptotic activity were demonstrated for ST induced DNA damage before or simultaneous with HDAC inhibition and cell death was mediated through the p53 pathway. These observations may aid in designing new protocols for treating pediatric patients with high-risk EWS.

Epidermal Growth Factor Receptor Regulation of Ewing Sarcoma Cell Function

“…Knockdown of EWS/FLI1 was also coupled to decreases in cyclin D1 and promotion of p53 expression [38, 39] which were observed after EGFR inhibition in our experiments. Thus, activities displayed by an EGFR inhibitor are consistent with other experimental agents that induce antiproliferative effects in ES associated with stimulation of p53 expression [40-42]. The combined actions of inhibiting protein kinase signaling and reducing cyclin D1 expression while promoting expression of p53 highlight the potential of EGFR inhibition to target both growth and cell cycle progression pathways, which are required for EWS/FLI1-induced malignant transformation [43].…”

Cytisine exerts anti-tumour effects on lung cancer cells by modulating reactive oxygen species-mediated signalling pathways

“…During the cell cycle, the G2/ M checkpoint is a possible target for cancer therapy, and CDK/cyclin are critical and complex regulators of the G2/M phase [20]. Recent studies have demonstrated that various anticancer drugs induce G2/M arrest accompanied by downregulating the expression levels of AKT [21]. In our study, the results showed that cytisine treatment resulted in G2/M arrest and decreased expression of p-AKT, CDK1/2, and cyclin B1, and increased the expression of p27 and p21, suggesting that the AKT signalling pathway may be the molecular mechanism through which cytisine induced G2/M phase arrest (Figure 3).…”

Clinical significance and biological function of fucosyltransferase 2 in lung adenocarcinoma

“…In recent years, the research direction of cancer has been transferred into protein molecular level. Aberrant protein glycosylation is known to be associated with the development of cancers [ 20 - 23 ]. FUTs are key enzymes have been implicated in differentiation, development and malignancy of human cancer through the fucosylation of proteins [ 15 ].…”