Abstract 1062: Inhibition of ovarian and endometrial cancer cell proliferation by an anti-ROR1 monoclonal antibody
Authors: Dongli Liu, Gunnar F. Kaufmann, James B. Breitmeyer, Kristie-Ann Dickson, Deborah J. Marsh, Caroline E. Ford
Journal: Cancer Research (2021)

Abstract The non-canonical Wnt signalling receptor ROR1 has been shown to be aberrantly expressed in numerous cancers, including ovarian and endometrial cancer (EC). Cirmtuzumab is a humanised monoclonal antibody against ROR1 that blocks Wnt5a-induced ROR1 signalling. It has demonstrated safety and efficacy in several Phase I/II clinical trials for chronic lymphocytic leukemia (CLL), mantle cell lymphoma (MCL) and Her2-negative breast cancer. The aim of this study was to investigate any anti-proliferative effect of cirmtuzumab in combination with commonly-used gynaecological cancer therapies (cisplatin, paclitaxel and the PARP inhibitor, olaparib) on high grade serous ovarian cancer (HGSOC) and EC cell lines including models of platinum resistance. The ROR1 positive HGSOC cells lines CaOV3, CaOV3CisR PEO1, PEO4 and EC cell lines Ishikawa, KLE were used in this study. First, IC50 for cisplatin, paclitaxel and olaparib in each cell line at 72h was determined using the cell counting kit 8 (CCK-8). Then, cells were seeded in 12-well plates and treated with cirmtuzumab at 25µg/ml or 50µg/ml for 4h prior to the addition of the chemotherapeutic agents at IC70 concentration. The effect of cirmtuzumab +/- agents was quantified using the IncuCyte S3 Live Cell Analysis System. Phase contrast cell images were obtained using a 10x objective lens within the instrument every 3h for 72h in total. The average confluence of each well was calculated and normalised against the baseline (time 0). Two-way ANOVA followed by Bonferroni post-test was performed to evaluate the effect of treatments. RNA and protein were extracted at the end of the incubation for qRTPCR and Western blot analysis. Single dose cirmtuzumab at both 25µg/ml and 50µg/ml significantly inhibited proliferation of CaOV3, CaOV3cisR, PEO1 and Ishikawa cells. 50µg/ml of cirmtuzumab decreased proliferation of KLE. Compared to paclitaxel alone, addition of 50µg/ml of cirmtuzumab significantly inhibited proliferation of CaOV3, CaOV3CisR, PEO1 and PEO4. Compared to cisplatin alone, addition of 25µg/ml of cirmtuzumab significantly inhibited proliferation of CaOV3CisR, PEO4; addition of 50µg/ml of cirmtuzumab significantly inhibited proliferation of CaOV3, CaOV3CisR, PEO4. Compared to olaparib alone, addition of 25µg/ml of cirmtuzumab significantly inhibited proliferation of CaOV3CisR; addition of 50µg/ml of cirmtuzumab significantly inhibited proliferation of CaOV3 and CaOV3CisR. No significant change in ROR1 or ROR2 expression levels was observed following cirmtuzumab treatment, however treatment did result in alterations to markers of epithelial-mesenchymal transition (EMT). Cirmtuzumab alone inhibited proliferation of ovarian cancer and EC cells in vitro, and could enhance the activity of commonly-used chemotherapeutic agents. This study supports the potential of cirmtuzumab or other ROR1 targeting therapies for treating women with HGSOC and EC. Citation Format: Dongli Liu, Gunnar F. Kaufmann, James B. Breitmeyer, Kristie-Ann Dickson, Deborah J. Marsh, Caroline E. Ford. Inhibition of ovarian and endometrial cancer cell proliferation by an anti-ROR1 monoclonal antibody [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 1062.