Development and characterisation of novel monoclonal antibodies against ovarian cancer for potential diagnostic and therapeutic use

Despite the recent advances in cytoreductive surgery and chemotherapy, ovarian cancer is one of the most lethal gynaecological malignancies and the eighth most diagnosed cancer among women in the world. Ovarian cancer incidence rates are projected to rise 5% in the UK between 2023-2025 and 2038-2040, with 9400 new cases every year by 2038-2040. Ovarian cancer is sensitive to chemotherapy agents like platinum-based drugs and most patients enter a period of remission after initial treatment. However, disease-recurrence is a major challenge. In the past few decades, several monoclonal antibody (mAb)-based drugs have been approved for the treatment of patients with a wide range of cancers. Of these, only two of mAbs have been approved for the treatment of patients with ovarian cancer. Moreover, the duration of response can be short in many patients with ovarian cancer. Therefore, further research is needed for the discovery and development of novel therapeutic antibodies for the treatment of ovarian cancer.

In addition to the therapeutic applications of mAb products, mAb technology is an excellent tool for the discovery of overexpressed cell surface antigens of biological and clinical significance in cancer patients. Using the hybridoma technology, this project aimed to develop mAbs in ovarian cancer and investigate their potential in antibody-based immunotherapy of ovarian cancer. It also aimed to discover overexpressed cell surface antigens in ovarian cancer.

Using human ovarian cancer cells SKOV3, ES2 and OVCAR-3 as sources of immunogens, a panel of six monoclonal antibodies were developed. The differential binding of these mAbs to a panel of human ovarian and breast cancer cell lines suggest that these may be directed against different target antigens. Following purification, the antibodies were isotyped and two (KU97.71B.81.19 and KU97.91A.57.32) were found to be of IgG3Κ isotype. The other four antibodies (KU103.46B.8.60; KU103.65B.8.22; KU97.75B.3.39; KU107.72B.81.3) were IgG1Κ isotype. The expression levels of the target antigens were determined by ELISA and flow cytometry, they were found to be highly expressed in some cell lines. Immunofluorescence staining of the cancer cell lines showed the mAbs are presumably directed against cell surface antigens. Even at the maximum antibody concentration of 300nM, the antibodies did not inhibit the growth of human cancer cell lines in vitro although bands were detected in immunoprecipitation studies except with the monoclonal antibody KU103.65B.8.22. Immunoprecipitation followed by mass spectrometry showed the target antigen of KU107.72.81.3 is membrane tyrosine kinase HER-2. Further optimisation of immunoprecipitation studies followed by mass spectrometry analysis could determine the target antigens of the other mAbs and whether they are cancer neoantigens.

Future investigation using immunohistochemical staining of tumour cells and tissue microarrays from patients may confirm the potential of these mAbs to be developed into diagnostic kits for the selection of specific population of patients who can benefit from therapy with such antibodies.