Inhibition of P-STAT3 Enhances IFN-alpha Efficacy Against Metastatic Melanoma in a Murine Model

Purpose: Melanoma is a common and deadly tumor that upon metastasis to the central nervous system has a median survival duration of <6 months. Activation of the signal transducer and activator of transcription 3 (STAT3) has been identified as a key mediator that drives the fundamental components of melanoma malignancy, including immune suppression in melanoma patients. We hypothesized that WP1193, a novel inhibitor of STAT3 signaling, would enhance the antitumor activity of IFN-alpha against metastatic melanoma.

Experimental Design: Combinational therapy of STAT3 blockade agents with IFN-alpha was investigated in a metastatic and an established syngeneic intracerebral murine tumor model of melanoma. The immunologic in vivo mechanisms of efficacy were investigated by T-cell and natural killer (NK) cell cytotoxic assays.

Results: IFN-alpha immunotherapy was synergistic with WP1193 showing marked in vivo efficacy against metastatic and established intracerebral melanoma. At autopsy, it was noted that there was a decreased trend in mice with melanoma developing leptomeningeal disease treated with combinational therapy. The combinational approach enhanced both NK-mediated and T-cell-mediated antitumor cytotoxicity.

Conclusions: The immune modulatory effects of STAT3 blockade can enhance the therapeutic efficacy of IFN-alpha immunotherapy by enhancing both innate and adaptive cytotoxic T-cell activities. This combination therapy has the potential in the treatment of metastatic melanoma that is typically refractory to this type of immune therapeutic approach.