OR27 Monoclonal antibody RL41A recognizes cisplatin resistant ovarian cancer cells via HLA-A2

Abstract

Cisplatin is widely used as a chemotherapeutic drug in the treatment of ovarian cancer. Resistance to cisplatin occurs in about one-third of women during the primary course of treatment and in all patients treated for recurrent disease. We hypothesized that the HLA class I of cisplatin-resistant ovarian cancer cells presents peptides distinct to these cells as compared to sensitive cells and that HLA/peptide complexes unique to cisplatin-resistant cells would be valuable targets for immunotherapeutic intervention. To identify peptides that are uniquely presented by the HLA of cisplatin resistant ovarian cancer cells, the intrinsic cisplatin-resistant cells (SKOV3) and sensitive cells (A2780, OV90, FHIOSE) were transfected to express soluble HLA-A*02:01. Transfected resistant and sensitive cells were grown in separate bioreactors. Harvested HLA were purified by immunoaffinity chromatography, and high throughput comparative mass spectrometry was employed to identify the peptids unique to cisplatin-resistant cells. A T cell receptor mimic monoclonal antibody (TCRm mAb) was then generated against cisplatin resistant peptide/HLA-A*02:01 complex, using mouse immunization and hybridoma technology. Peptide sequences distinct to cisplatin-resistant cells were identified including a peptide (VMF11) derived from thioredoxin interacting protein (TXNIP) that was present in abundance in SKOV3. Next a TCRm mAb (RL41A) was produced against A*02:01/VMF11 complex. The specificity and affinity of RL41A toward VMF11/A*02:01 complex was shown by staining peptide-pulsed T2 cells and surface plasmon resonance respectively. Staining of ovarian cancer cells by flow cytometry also showed that RL41A was able to only stain cisplatin-resistant cells and not the sensitive ones. We therefore report the successful development of a TCRm mAb that could be an attractive candidate for further validation using cisplatin-resistant and sensitive primary ovary tissues. W. Hildebrand: Scientific/Medical Advisor; Company/Organization; Pure MHC, LLC.