Temporal changes within the (bladder) tumor microenvironment that accompany the therapeutic effects of the immunocytokine NHS-IL12

Background While significant strides in the treatment of metastatic bladder cancer have been made with immune checkpoint inhibitors, the treatment of carcinoma in situ and non-muscle invasive, non-metastatic (superficial) human urothelial carcinoma, also termed non-muscle invasive bladder cancer (NMIBC), remains intractable with bacillus Calmette-Guerin (BCG) employed as the standard of care. In this study, an immunocytokine, NHS-muIL12, which consists of two molecules of murine IL-12 fused to NHS76, a tumor necrosis-targeting human IgG1, was examined as an immunotherapeutic in an orthotopic MB49 luc bladder tumor model. Methods The antitumor activity of systemic administration of NHS-muIL12 was investigated on MB49 luc tumors, an aggressive, bioluminescent orthotopic bladder cancer model. Temporal studies were carried out on MB49 luc bladder tumors harvested during various time points during NHS-muIL12 treatment and cellular changes associated with the reduction in tumor burden following NHS-muIL12 were determined by flow cytometry. Effects of those changes on the proliferation/activation of lymphoid cells were also determined. Results Studies revealed a significant reduction in MB49 luc bladder tumor burden occurring between days 3 and 6 after the third and final systemic administration of NHS-muIL12. Temporal analyses of the MB49 luc bladder tumor microenvironment (TME) initially revealed a large accumulation of myeloid-derived suppressor cells (MDSCs) and macrophages that elicited potent immunosuppression. Immunosuppression was characterized by the inability of CD4 + and CD8 + T cells to respond to broad-based immune stimulants. NHS-muIL12 administration resulted in temporal-dependent reductions in the number of MDSCs, macrophages and tumor-associated TGF - β, which culminated in a re-ignition of CD4 + and CD8 + T cells to elicit potent antitumor responses against MB49 luc bladder tumors. Conclusions These findings provide strong evidence that the systemic administration of an immunocytokine consisting of a tumor-targeting Ig through recognition of DNA and DNA-histone complexes coupled to muIL-12 can effectively target the bladder TME; this significantly reduces the myeloid cellular compartment and reverts an immunosuppressive to an immunopermissive TME, ultimately resulting in antitumor effects. These studies provide further rationale for the employment of NHS-IL12 as an immunomodulator and clinical immunotherapeutic for NMIBC.