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PURPOSE: As a novel candidate in cancer immunotherapy, siglec-15-targeting antibodies hold promise for providing alternative therapeutic strategies to tumors unresponsive to programmed death ligand 1 (PD-L1) antibody therapy. To date, pharmacological development targeting siglec-15 has not yet achieved significant breakthroughs or clinical approval. Therefore, this study aims to develop a novel anti-siglec-15 antibody designed to restore tumor immune normalization.

METHODS

In this study, we constructed a phage immune library derived from lymphoid tissues of lung cancer patients using phage display technology and screened the fully human antibodies against siglec-15 antigen from this library. The antibody affinity was detected by Bio-Layer Interferometry, the binding rate of antibody to positively expressing siglec-15 tumor cells was examined by flow cytometry, and the activity of antibody-mediated killer cells against tumor cells was reflected by Antibody-Dependent Cellular Cytotoxicity (ADCC) action. The blockage of proliferation inhibition caused by siglec-15 antigen by antibodies was investigated by t-lymphocyte proliferation assays, and CD8+ T cells were collected from malignant pleural effusion specimens derived from lung cancer patients to determinewhether antibodies could alleviate the immunosuppression present in the tumor microenvironment (TME). The anti-tumor efficacy of the antibody was investigated in vivo by constructing a zebrafish tumor model and a humanized mouse tumor model.

RESULTS

The antibody demonstrated nanomolar affinity and specificity, enhanced antibody-dependent cellular cytotoxicity (ADCC) against tumor cells, reversed T-cell suppression, and reduced CD8+ T-cell exhaustion in vitro analyses. In vivo models confirmed tumor growth inhibition via increased lymphocyte infiltration and activation.

CONCLUSION

Antibody immune libraries from lymphoid tissues of lung cancer patients can screen specific antibodies against siglec-15 target antigens and exert certain biological functions in vitro and in vivo.