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Banville, Allyson C.

University of British Columbia

Current cancer immunotherapies primarily leverage prognostically favourable tumour-infiltrating T cells (TIL-Ts); however, optimal anti-tumour immunity additionally requires tumour-infiltrating B cells (TIL-Bs). Many solid cancers such as high-grade serous ovarian cancer (HGSC) remain resistant to immunotherapies despite harbouring TIL-Ts and TIL-Bs, suggesting that further research is needed to devise optimal immunotherapeutic strategies for these cancers. One of the most successful T cell-based immunotherapies, chimeric antigen receptor (CAR)-T cell therapy, ideally targets a surface antigen that is exclusively and uniformly expressed by tumours; however, no such antigen is known for HGSC. Therefore, we investigated the potential for multi-antigenic targeting with antigens commonly over-expressed in HGSC: CA125, mesothelin, and folate receptor alpha. We used immunofluorescence to quantify co-expression patterns of these antigens in HGSC. We identified that a CAR-T cell strategy targeting CA125 and/or mesothelin was the most promising approach, yet no approach would target 100% of tumour cells in all cases, prompting further research into immunotherapeutic strategies for HGSC. While TIL-Ts are positively prognostic, the best prognosis is observed with additional presence of TIL-Bs; however, the target antigens and mechanisms through which TIL-Bs confer this beneficial effect remain poorly understood. We endeavoured to decipher the role of TIL-Bs in anti-tumour immunity to guide the development of better immunotherapies that leverage the prognostic benefit associated with TIL-Bs. We performed single-cell RNA sequencing using TIL-Bs from patient-derived HGSC tumours. We identified 1,379 TIL-B B cell receptors (BCRs) and produced 51 of the most expanded, somatically hypermutated, class-switched BCRs as recombinant antibodies (rAbs). Flow cytometry, western blotting, and immunohistochemistry revealed that TIL-B-derived rAbs frequently recognize intracellular antigens across normal, embryonic, and cancerous cells/tissues. By phage-based cDNA library immunoscreening and immunoprecipitation-mass spectrometry, we identified three TIL-B target antigens, which are all intracellular self-antigens over-expressed in cancer. By ELISA, a substantial proportion of TIL-B-derived rAbs were polyreactive, yet matched patient serum did not display elevated levels of autoreactivity. Overall, my results highlight the opportunities and shortcomings of existing CAR-T cell strategies while providing critical insights into TIL-B-mediated immunity in HGSC, suggesting multiple avenues through which to develop future immunotherapies that harness the positive prognosis associated with TIL-Bs.

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2024-10-24

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/89499

Interdisciplinary Oncology

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/