Neoadjuvant immunotherapy approaches to early stage melanoma

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Project Summary – Project 3 There is an unmet need to improve the survival of patients with high-risk Stage II melanoma. Currently, the treatment for Stage II melanoma is surveillance despite unacceptably high recurrence and mortality rates observed with surgery alone. The sentinel lymph node (SLN) is the first lymph node drained by a primary tumor and is not only a target for metastasizing cancer cells but also an immunological sensor of tumor antigens released by primary cutaneous melanoma. Our preliminary data in a draining lymph node (LN) metastasis model shows striking increases in myeloid cell populations prior to and during melanoma metastasis to the LN. We propose that these changes in the LN may compromise its ability to act (i) as a gatekeeper to prevent melanoma spread via the lymphatics and (ii) as an instructor of antigen-specific T cell immunity capable of controlling local disease and intervening on hematogenous spread. Thus, our overall hypothesis is that the capacity of the SLN to protect against locoregional and distant melanoma spread is dependent on its immune health, which is pliable and determined by the immunostimulatory capacity of lymph node-resident myeloid cells. In Aim 1, Drs. Karakousis (Clinical co-Project Leader (PL)) and Schuchter (co-Investigator (I)) will conduct an investigator-initiated Phase II clinical trial of neoadjuvant pembrolizumab in clinical Stage IIB/C melanoma. Using primary tumors and sentinel LNs (SLN) from both this clinical trial and stage-matched historical cohorts, we will determine the effects of immunotherapy on the immunophenotype and anti-metastatic capacity of the SLN. We will use a combination of unbiased global profiling strategies pioneered by Dr. Wherry (co-I) and hypothesis-driven approaches guided by our discoveries into the role of macrophages in preparing the metastatic niche (Beatty, Applied co-PL) to determine therapy-associated changes in SLN-positive and -negative patients. Studies in syngeneic models will then inform the role of myeloid cell subsets in directing changes in LN biology triggered by melanoma development and their impact on anti-PD1 therapy. Aim 2 will test the hypothesis that the immunostimulatory capacity of lymph node dendritic cells determines the likelihood of response to anti-PD1 therapy. Under the leadership of co-PLs Drs. Herlyn and Beatty , we will use multiplex tissue- and cell-based assays to analyze samples collected from our Phase II trial and stage-matched historical controls with the goal to define T cell interactions with myeloid cells, including dendritic cells, and their impact on treatment response and clinical outcomes. In addition, we will determine if clinically-available TLR agonists can enhance the immunostimulatory capacity of the draining LN and in doing so, improve the efficacy of anti-PD-1 therapy using humanized mice challenged with patient-derived xenografts which model early stage melanoma with high fidelity. Impact: We anticipate neoadjuvant immunotherapy will substantially reduce SLN positivity rates warranting future randomized studies designed to change clinical practice. We expect to identify the SLN as an important determinant of melanoma pathogenesis and clinical outcomes to immunotherapy.