Jun Young Choi

The p53-reactivating small-molecule RITA enhances cisplatin-induced cytotoxicity and apoptosis in head and neck cancer

We evaluated whether the restoration of p53 function by the p53-reactivating small molecule RITA (reactivation of p53 and induction of tumor cell apoptosis enhances cisplatin-induced cytotoxicity and apoptosis in head-and-neck cancer (HNC). RITA induced prominent accumulation and reactivation of p53 in a wild-type TP53-bearing HNC cell line. RITA showed maximal growth suppression in tumor cells showing MDM2-dependent p53 degradation. RITA promoted apoptosis in association with upregulation of p21, BAX, and cleaved caspase-3; notably, the apoptotic response was blocked by pifithrin-α, demonstrating its p53 dependence. With increasing concentrations, RITA strongly induced apoptosis rather than G2-phase arrest. In combination therapy, RITA enhanced cisplatin-induced growth inhibition and apoptosis of HNC cells invitro and in vivo. Our data suggest that the restoration of p53 tumor-suppressive function by RITA enhances the cytotoxicity and apoptosis of cisplatin, an action that may offer an attractive strategy for treating HNC.

HSP90 inhibitor (NVP-AUY922) enhances the anti-cancer effect of BCL-2 inhibitor (ABT-737) in small cell lung cancer expressing BCL-2

Small cell lung cancer (SCLC) cannot be efficiently controlled using existing chemotherapy and radiotherapy approaches, indicating the need for new therapeutic strategies. Although ABT-737, a B-cell lymphoma-2 (BCL-2) inhibitor, exerts anticancer effects against BCL-2-expressing SCLC, monotherapy with ABT-737 is associated with limited clinical activity because of the development of resistance and toxicity. Here, we examined whether combination therapy with ABT-737 and heat shock protein 90 (HSP90) inhibitor NVP-AUY922 exerted synergistic anticancer effects on SCLC. We found that the combination of ABT-737 and NVP-AUY922 synergistically induced the apoptosis of BCL-2-expressing SCLC cells. NVP-AUY922 downregulated the expression of AKT and ERK, which activate MCL-1 to induce resistance against ABT-737. The synergistic effect was also partly due to blocking NF-κB activation, which induces anti-apoptosis protein expressions. However, interestingly, targeting BCL-2 and MCL-1 or BCL2 and NF-κB did not induce the cytotoxicity. In conclusion, our study showed that combination of BCL2 inhibitor with HSP90 inhibitor increased activity in inxa0vitro and inxa0vivo study in only BCL-2 expressing SCLC compared to either single BCL2 inhibitor or HSP inhibitor. The enhanced activity might be led by blocking several apoptotic pathways simultaneously rather than a specific pathway.

Abstract 2022: Hsp90 inhibitor (NVP-AUY922) enhances anti-cancer effect of Bcl-2 inhibitor (ABT-737) in small cell lung cancer

Background: Bcl-2 family is a group of apoptosis regulators that plays an anti-apoptotic role for cell survival and is known to contribute to induce chemotherapy resistance in small cell lung cancer (SCLC). ABT-737 is an anti-cancer drug that induces apoptosis by selectively blocking the activities of Bcl-2 and Bcl-xL, but not Mcl-1. Consequently, the efficacy of ABT-737 is largely restricted in the presence of Mcl-1. Heat-shock-protein 90 (Hsp90) is highly expressed in most tumors and Hsp90 inhibitors induce the proteasomal degradation of Hsp90 client proteins. In addition, Hsp90 inhibitor can reduce Mcl-1 expression, a down-stream of Akt and Erk pathway. Furthermore, Hsp90 inhibitor inhibits activities of NF-κB by degradation of IKK. Thus, we show that downregulation of Mcl-1 and NF-κB by Hsp90 inhibitor can lead to synergistic pro-apoptotic effects with ABT-737. Materials and methods: The proliferative activity, apoptotic activities, and expression of apoptotic proteins were assessed in SCLC cell lines after treatment with ABT-737, NVP-AUY922, or both drugs. The synergy effects of ABT-737 and NVP-AUY922 were analyzed by cell viabilities with different concentrations in SCLC cell lines, and the combination index values were Results: Here, we show that NVP-AUY922, an Hsp90 inhibitor, can potentiate the pro-apoptotic effects of ABT-737 not only by reducing the levels of Akt but also by inhibiting pNF-κB, both of which are proteins regulating apoptosis signaling. Western blot analysis revealed that proteins associated with apoptosis such as PARP, Caspase 3 and 7 were more upregulated in SCLC cells exposed to the drug combination than in cells exposed to NVP-AUY922 or ABT-737 alone. In addition, Annexin V & dead cell assay showed dual inhibition of the Hsp90 and Bcl-2 signaling pathways more increased apoptotic cells and dead cells in SCLC. In our result, ABT-737 induced apoptosis by blocking Bcl-2 activation, and NVP-AUY922 blocked the levels of Hsp90 client proteins, Akt and pErk, ultimately leading to decreased level of Mcl-1. In addition, NVP-AUY922 induced degradation of IKK, and increased IκB-α inhibited activation of NF-κB. And this combination treatment showed higher BIM and BID expression, pro-apoptotic proteins, than single treatment. Furthermore, synergy effects of combination were verified in xenograft model with human SCLC cell line. Conclusions: Consequently, NVP-AUY922 synergizes with ABT-737 to induce apoptosis by reducing activities of Mcl-1 and NF-κB in SCLC. This study suggests that adopting an appropriate combination of drugs can lead to better outcomes compared with monotherapy in SCLC. Citation Format: Hannah Yang, Kang-Seo Park, Junyoung Choi, Sang-We Kim Kim, Dae Ho Lee. Hsp90 inhibitor (NVP-AUY922) enhances anti-cancer effect of Bcl-2 inhibitor (ABT-737) in small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2022. doi:10.1158/1538-7445.AM2017-2022

The HSP90 inhibitor, NVP-AUY922, attenuates intrinsic PI3K inhibitor resistance in KRAS-mutant non-small cell lung cancer

More than 25% of non-small cell lung cancers (NSCLCs) carry mutations in KRAS, one of the most common oncogenic drivers in this disease. KRAS-mutant NSCLC responds poorly to currently available therapies; therefore, novel treatment strategies are needed. Here, we describe a particularly promising targeted therapeutic strategy against KRAS mutation-harboring NSCLC intrinsically resistant to treatment by PI3K inhibition. We found that intrinsic resistance to PI3K inhibition derived from RAF/MEK/ERK and RSK activation, bypassing blockage of the PI3K/AKT/mTOR pathway. The HSP90 inhibitor AUY922 suppressed both PI3K/AKT/mTOR and RAF/MEK/ERK signaling, rendering cells sensitive to a PI3K inhibitor (omipalisib, GSK458). Combining these two drugs achieved a synergistic effect, even using only sub-therapeutic concentrations. Dual inhibition of the HSP90 and PI3K signaling pathways with sub-therapeutic doses of these combined anticancer drugs may represent a potent treatment strategy for KRAS-mutant NSCLC with intrinsic resistance to PI3K inhibition.

Abstract 1768: Enhanced cytotoxicity and apoptosis of cisplatin by p53-reactivating small molecule RITA in head and neck cancer

Overexpression of MDM2 inactivates the tumor suppressive function of p53 and a small-molecule reactivation of p53 and induction of tumor cell apoptosis (RITA) disrupts the MDM2-p53 interaction. We evaluated whether the restoration of p53 function by RITA enhances cytotoxicity and apoptosis of cisplatin in head-and-neck cancer (HNC). RITA was tested in four human HNC cell lines differing in TP53 status. In vitro and in vivo growth suppression, cell cycle arrest, apoptosis after RITA treatment individually or in combination with cisplatin were assessed. RITA induced prominent accumulation and reactivation of p53 in a wild-type TP53-bearing tumor cell line. RITA showed maximal growth suppression in tumor cells showing MDM2-dependent p53 degradation. RITA upregulated p21, BAX, and cleavage of caspase-3 but the p53-dependent apoptosis was blocked by pifithrin-μ. Strong induction of apoptosis rather than G2-phase arrest was observed along with increased dose of RITA. In combination therapy, RITA enhanced the growth inhibition and apoptosis of HNC by cisplatin in vitro and in vivo. Our data suggest that the restoration of p53 tumor suppressive function by RITA enhances cytotoxicity and apoptosis of cisplatin, which may offer an attractive strategy for treating HNC. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1768. doi:1538-7445.AM2012-1768