Quinacrine in endometrial cancer: Repurposing an old antimalarial drug

Objective Generate preclinical data on the effect of quinacrine (QC) in inhibiting tumorigenesis in endometrial cancer (EC) in vitro and explore its role as an adjunct to standard chemotherapy in an EC mouse model. Methods Five different EC cell lines (Ishikawa, Hec-1B, KLE, ARK-2, and SPEC-2) representing different histologies, grades of EC, sensitivity to cisplatin and p53 status were used for the in vitro studies. MTT and colony formation assays were used to examine QC's ability to inhibit cell viability in vitro. The Chou-Talalay methodology was used to examine synergism between QC and cisplatin, carboplatin or paclitaxel. A cisplatin-resistant EC subcutaneous mouse model (Hec-1B) was used to examine QC's role as maintenance therapy. Results QC exhibited strong synergism in vitro when combined with cisplatin, carboplatin or paclitaxel with the highest level of synergism in the most chemo-resistant cell line. Neither QC monotherapy nor carboplatin/paclitaxel significantly delayed tumor growth in xenografts. Combination treatment (QC plus carboplatin/paclitaxel) significantly augmented the antiproliferative ability of these agents and was associated with a 14-week survival prolongation compared to carboplatin/paclitaxel. Maintenance with QC resulted in further delay in tumor progression and survival prolongation compared to carboplatin/paclitaxel. QC was not associated with weight loss and the yellow skin discoloration noted during treatment was reversible upon discontinuation. Conclusions QC exhibited significant antitumor activity against EC in vitro and was successful as maintenance therapy in chemo-resistant EC mouse xenografts. This preclinical data suggest that QC may be an important adjunct to standard chemotherapy for patients with chemo-resistant EC.