Abstract 6793: In vivo effects and molecular mechanisms of Minnelide mediated enhancement of measles virus oncolysis in human colorectal cancer
Authors: Chavez Valery A. , Bustamante Floritza , Merchan-Mendes Carolina , Saluja Ashok , Merchan Jaime 
Published: April 2023

Background: The development of novel biotherapies for metastatic colorectal cancer (CRC), a fatal disease when advanced, is an urgent medical need. Oncolytic viruses (OVs) are novel cancer biotherapies, and the oncolytic measles virus (MV) has demonstrated safety and antitumor activity in early clinical studies. Triptolide (TRP), a diterpenoid epoxide extracted from the thunder god vine, and Minnelide (MN), its water-soluble compound, are novel agents associated with potent antitumor, anti-proliferative, pro-apoptotic, antiangiogenic, and ER stress inducing effects. The objectives of this study are to characterize the in vitro and in vivo effects and molecular mechanisms of measles virotherapy in combination with TRP and MN in CRC.

Methods: The in vitro effects of TRP, MV-GFP (Edmonston strain of Measles virus expressing eGFP), MV-CD46-muPA (dual targeted MV against the murine uPA receptor and human CD46), or virus-triptolide combinations on tumor cell cytotoxicity were assessed on HT-29, HCT116 and SW620 CRC cells. Molecular and mechanistic characterization of TRP’s effects alone and combination with MV in HT29 cells was analyzed by the Reverse Phase Protein Array (RPPA) and validated by western blot analysis. In vivo effects (tumor progression and survival) of MN alone and in combination with MV vectors using different treatment schemes were assessed in HT-29 tumor bearing NSG mice, and tumor correlative studies were performed.

Results: MV and TRP had single agent antitumor activity against human CRC cell lines. MV-TRP combinations were associated with increased in vitro cytotoxicity compared to single agent treatments. Functional proteomics analysis showed that TRP-MV combinations were associated with inhibition of survival and proliferation pathways, such as AKT, ERK, inhibition of HSP70 as well as induction of autophagy, at a higher level than each agent alone. In vivo, both a 7-days MN treatment and a 21-days MN treatment significantly improved long term tumor control and significantly improved survival, compared to each agent alone. Tumor studies showed that MN increased MV tumor deposition, as well as enhancement in apoptosis and inhibition of proliferation. Molecular characterization of oncogenic pathways modulated by MV-Minnelide combinations (Nanostring) are underway and will be presented at the meeting.

Conclusions: Our results demonstrated that, in human CRC xenografts, Minnelide safely and significantly enhances measles virus oncolysis in vivo, leading to improved antitumor effects and prolonged survival. These effects were associated with enhanced antiproliferative and pro-apoptotic effects with the MV-Minnelide combination, suggesting in vivo synergy. Studies characterizing the molecular mechanisms of in vivo synergy and assessing this promising combination in immunocompetent CRC models are underway.

Citation Format: Valery A. Chavez, Floritza Bustamante, Carolina Merchan-Mendes, Ashok Saluja, Jaime Merchan. In vivo effects and molecular mechanisms of Minnelide mediated enhancement of measles virus oncolysis in human colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6793.