Cl-Amidine and Rapamycin Combination as a Novel Synergistic Co-therapy For Ovarian Cancer

Peptidyl arginine deiminases (PADs) are a family of calcium-binding enzymes that catalyze the citrullination of arginine and methylarginine residues as a form of gene regulation. The overexpression of PAD4 in cancer cells contributes to tumorigenesis and metastasis through the accelerated formation of neutrophil extracellular traps (NETs) and the downregulation of the p53 pathway. Significantly elevated PAD4 levels have been observed in various ovarian cancer subtypes, and it has been proposed that this elevation is a significant contributor to the malignancy of these cancers. Thus, the purpose of this research was to explore the effect of Cl-amidine, a small organic compound and irreversible inhibitor of PAD4, on human ovarian adenocarcinoma cell lines. In addition, Cl-amidine has been indicated to have potentially synergistic interactions with rapamycin, an established anticancer drug, against breast cancer cells. Therefore, the potential for Cl-amidine and rapamycin to act synergistically against ovarian cancer was also explored. Cl-amidine alone ultimately resulted in 70% cancer cell death, while Cl-amidine in combination with rapamycin resulted in nearly 90% cancer cell death. Cl-amidine and rapamycin showed significant synergistic activity (FIC50< 0.5) and up to 90% of ovarian cancer cells were in apoptosis following cotreatment. Cl-amidine alone and in combination with rapamycin significantly upregulated the expression of tumor suppressor genes TP53 and CDKN1A. Both compounds were shown to have negligible effects on noncancerous cell lines. Thus, Cl-amidine as a monotherapy and as a co-therapy with rapamycin showed significant antiproliferative, cytotoxic, and pro-apoptotic properties, and may be a promising candidate for the treatment of ovarian cancer.