(866) Investigating immune checkpoint blockade of LY-6A protein as cancer immunotherapy in mice.

Introduction/Rationale: Ly-6A is a potential immune checkpoint on T cells. Evidence suggests that overexpression of Ly-6A diminishes T cell responses; ligand interaction induces the intrinsic apoptotic pathway, whereas the loss of this expression leads to moderate hyperresponsiveness. Notably, Ly-6A-/- mice exhibit reduced B16-F10 tumor growth compared with wild-type controls. This study evaluated the therapeutic efficacy of four anti-Ly-6A monoclonal antibodies in the B16-F10 mouse model using wild-type C57Bl/6 mice.

Methods: A B16-F10 melanoma model was established in C57BL/6 mice. 100 µg of each antibody was injected intraperitoneally. 3 days post initial treatment, tumor cells were injected subcutaneously. Tumor volume was measured starting at palpability and calculated as V = ½ x {(Length) x (Width²)}. Efficacy was assessed using three parameters: overall survival, terminal tumor weight, and day 12 tumor volume. Following euthanasia, tumors were cryopreserved in liquid nitrogen. Statistical analysis of volume and weight was performed via one-way ANOVA. Harvested tumor and spleen sections were processed for immunohistochemical analysis of T-cell markers.

Results: While most mice exhibited progressive tumor kinetics, one antibody clone demonstrated superior therapeutic efficacy. In this cohort, 80% of mice had no palpable tumors by day 12. Although mean growth rates did not reach statistical significance across all time points, the reduction in early tumor burden and the increase in overall survival (p < 0.05) highlight the efficacy of this specific Ly-6A clone.

Conclusion: This study established the therapeutic efficacy of anti-Ly-6A antibodies and identified one candidate with superior tumor growth suppression. Ongoing research will evaluate the synergy of a dual Ly-6A and PD-1 blockade. To elucidate the underlying mechanisms, we will utilize multi-parameter FACS and RNA-seq of tumor-infiltrating lymphocytes to identify cellular changes associated with this novel checkpoint inhibition.