Adoptive transfer of Bispecific antibody Armed activated T cells (BATs) showed promising anti-tumor activity in clinical trials in solid tumors. The cytotoxic activity of BATs occurs upon engagement with tumor cells via the bispecific antibody (BiAb) bridge, which stimulates BATs to release cytotoxic molecules, cytokines, chemokines, and other signaling molecules extracellularly. We hypothesized that the release of BATs Induced Tumor-Targeting Effectors (TITE) by this complex interaction of T cells, bispecific antibody, and tumor cells may serve as a potent anti-tumor and immune-activating immunotherapeutic approach. In a 3D tumorsphere model, TITE showed potent cytotoxic activity against multiple breast cancer cell lines compared to control conditioned media (CM): Tumor-CM (T-CM), BATs-CM (B-CM), BiAb Armed PBMC-CM (BAP-CM) or PBMC-CM (P-CM). Multiplex cytokine analysis showed high levels of Th1 cytokines and chemokines; phospho-protein signaling array data suggest that the prominent JAK1/STAT1 pathway may be responsible for the induction and release of Th1 cytokines/chemokines in TITE. In xenograft breast cancer models, IV injections of 10× concentrated TITE (3×/week for 3 weeks; 150 μl TITE/injection) was able to inhibit tumor growth significantly (ICR/scid, p < 0.003; NSG p < 0.008) compared to the control mice. We tested the key components of the TITE for immune activating and anti-tumor activity individually and in combinations, the combination of IFN-γ, TNF-α and MIP-1β recapitulates the key activities of the TITE. In summary, master mix of active components of BATs-Tumor complex-derived TITE can provide a clinically controllable cell-free platform to target various tumor types regardless of the heterogeneous nature of the tumor cells and mutational tumor.
Keywords: 3D culture model; Activated T cells; Bispecific antibody; Breast cancer; Cancer stem cells; Myeloid-derived suppressor cells; Th1 cytokines.