Targeting Mitochondrial And Cytosolic One-Carbon Metabolism In Epithelial Ovarian Cancer Via Folate Receptor Alpha.

Abstract Epithelial ovarian cancer (EOC) is the most lethal gynecologic malignancy. Though most patients initially respond to platinum-based therapy, the likelihood of disease reoccurrence is nearly 100%. Thus, new tumor-selective therapies for EOC are urgently needed. One such treatment option involves targeting tumors via folate receptor α (FRα), which is overexpressed in up to 90% of EOCs and shows increasing expression with higher stage and grade of disease. Our laboratory discovered novel 5-substituted pyrrolo[3,2-d]pyrimidine analogs (AGF347, AGF359, AGF362 and AGF363) that inhibit mitochondrial one-carbon (C1) metabolism at serine hydroxymethyltransferase (SHMT) 2, with secondary inhibition at cytosolic enzyme targets including those in de novo purine biosynthesis. Potent inhibition was seen with several FRα-expressing EOC tumor cells. Inhibitory potencies were in order, AGF347 > AGF359 > AGF362 > AGF363. Drug effects were substantially reduced with excess folic acid (FA), confirming FRα-mediated drug uptake. Toward cisplatin resistant SKOV3, TOV112D and A2780 EOC cells, inhibition in the nanomolar range was detected with all compounds. Targeted metabolomics, using L-[2,3,3-2H]serine as a tracer in wild-type or SHMT2 knockdown SKOV3 cells, confirmed all compounds inhibited cytosolic and mitochondrial C1-metabolism (at SHMT2). Apoptosis was detected for all compounds by Annexin V/PI, with partial rescue of apoptosis observed upon addition of glutathione (GSH). Glutathione pools (GSH and total GSH+GSSG) were significantly perturbed by drug treatment with all inhibitors in SKOV3 cells, comparable to GSH levels observed in SHMT2 KD cells. In vivo efficacy studies with SKOV3 xenografts treated with either AGF347 or cisplatin in SCID mice showed cisplatin resistance, while AGF347 demonstrated efficacy and delay in disease progression with a median tumor growth delay of 10 days, with the longest delay being 15 days. Our studies describe a series of novel inhibitors targeting mitochondrial and cytosolic C1-metabolism, selectively delivered via FRα, which show direct cytotoxic effects against cisplatin resistant EOC in vitro and in vivo, and display additional mechanisms of cytotoxicity mediated through glycine depletion. Citation Format: Adrianne C. Wallace-Povirk, Carrie O'Connor, Xun Bao, Jade Katinas, Jennifer Wong-Roushar, Aamod Dekhne, Zhanjun Hou, Md. Junayed Nayeen, Khushbu Shah, Jose Cardiel Nunez, Jing Li, Seongho Kim, Lisa Polin, Charles E. Dann, Aleem Gangjee, Larry H. Matherly. Targeting mitochondrial and cytosolic one-carbon metabolism in epithelial ovarian cancer via folate receptor alpha [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2348.