Abstract 234: A novel, small molecule inhibitor of dihydroorotate dehydrogenase (DHODH), RP7214, potentiates activity of chemotherapeutics in breast and colorectal cancers
Authors: Azmi Asfar S. , Aboukameel Amro , Al-Hallak Mohammad Najeeb , Philip Philip A. , Penmetsa Kumar , Visvanadha Srikant , Mpilla Gabriel , Sexton Rachel , Mohammad Ramzi M. 
Published: September 2020

Abstract
Background: Dihydroorotate dehydrogenase (DHODH) is an enzyme which is critically involved in process of de novo pyrimidine biosynthesis. Therefore, it plays important roles in cell proliferation, mitosis and cellular metabolism. Importantly, overexpression of DHODH has been found in various types of malignant tumors including melanoma, myeloma, and lymphoma. Moreover, from Oncomine database, we observed that colorectal and kidney cancers and lymphoma have much higher expression of DHODH compared to normal cells. These findings suggest that DHODH could be a promising target for cancer therapy. Recently, we have designed and synthesized a novel small molecule inhibitor (RP7214) of DHODH and found that it has potent inhibitory effects in acute myeloid leukemia. However, the inhibitory effect of RP7214 on solid tumor-derived cell lines and the downstream oncogenic markers is not completely understood.
Methods: In vitro studies aimed at elucidating the effects of RP7214 on cell proliferation and the underlying molecular mechanisms were conducted using breast adenocarcinoma (MDA-MB-231) and colorectal carcinoma cell lines (HT-29 and HCT-116). We also investigated whether RP7214 could potentiate the anti-cancer activities of proven chemotherapeutics such as Verzenio, Doxorubicin, and Oxaliplatin, for the treatment of breast and colorectal cancers.
Results: RP7214 significantly (P&lt;0.05) inhibited proliferation and suppressed colony formation in MDA-MB-231, HT-29, and HCT-116 cells. Isobologram analysis showed that RP7214 synergistically enhanced the inhibitory effects of Verzenio and Doxorubicin on MDA-MB-231 cells proliferation. RP7214 and Oxaliplatin also showed synergistic inhibitory effects on the growth of HT-29 and HCT-116 colorectal cancer cells. Up-regulation of p21 with concomitant down-regulation of Bcl-2, myc, CDK6, and UAP1 in MDA-MB-231 cells treated with RP7214 alone or in combination with Doxorubicin was observed. Similarly, RP7214 also up-regulated the expression of p21 and Bax, and down-regulated the expression of CDK4, Akt, HOXA9, EZH2, and snail in HT-29 or HCT-116 cells treated with or without Oxaliplatin. These results suggest that the inhibitory effects of RP7214 on cancer cells could be mediated through the regulation of cell cycle, apoptosis, and metabolism pathways.
Conclusions: Based on these results, we conclude that RP7214 could be a promising DHODH inhibitor used in combination with conventional chemotherapeutics for better treatment of breast and colorectal cancers. We are now conducting animal experiment to confirm the value of RP7214 in vivo in combination treatment of breast and colorectal cancers.
Citation Format: Asfar S. Azmi, Amro Aboukameel, Mohammad Najeeb Al-Hallak, Philip A. Philip, Kumar Penmetsa, Srikant Visvanadha, Gabriel Mpilla, Rachel Sexton, Ramzi M. Mohammad. A novel, small molecule inhibitor of dihydroorotate dehydrogenase (DHODH), RP7214, potentiates activity of chemotherapeutics in breast and colorectal cancers [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 234.