Interleukin-12 (
IL12) enhances anti-
tumor immunity when delivered to the tumor microenvironment. However, local immunoregulatory elements dampen the efficacy of
IL12. The identity of these local mechanisms used by
tumors to suppress immunosurveillance represents a key knowledge gap for improving
tumor immunotherapy. From a systems perspective, local suppression of anti-
tumor immunity is a closed-loop system - where system response is determined by an unknown combination of external inputs and local cellular cross-talk. Here, we recreated this closed-loop system in vitro and combined quantitative high content assays, in silico model-based inference, and a proteomic workflow to identify the biochemical cues responsible for immunosuppression. Following an induction period, the
B16 melanoma cell model, a transplantable model for spontaneous
malignant melanoma, inhibited the response of a T helper cell model to
IL12. This paracrine effect was not explained by induction of apoptosis or creation of a
cytokine sink, despite both mechanisms present within the co-culture assay.
Tumor-derived Wnt-inducible signaling protein-1 (WISP-1) was identified to exert paracrine action on immune cells by inhibiting their response to
IL12. Moreover, WISP-1 was expressed in vivo following intradermal challenge with B16F10 cells and was inferred to be expressed at the
tumor periphery. Collectively, the data suggest that (1) biochemical cues associated with epithelial-to-mesenchymal transition can shape anti-
tumor immunity through paracrine action and (2) remnants of the immunoselective pressure associated with evolution in
cancer include both sculpting of
tumor antigens and expression of
proteins that proactively shape anti-
tumor immunity.