New insights on how melanoma cells resist cancer immunotherapy

How would you summarize your study for a lay audience? 

Immune checkpoint inhibitors are cancer fighting drugs that help the immune system do its job of detecting and attacking tumor cells. Programmed Cell Death 1 (PD-1) is a common target for this type of drug-;it is a protein that sits on the surface of T cells and helps regulate the immune system's response to neighboring cells, both normal and cancerous. While most research efforts to date have focused on PD-1's role in T cells, it is also active in many other kinds of cells-;including cancer cells as first demonstrated by the Schatton laboratory.

We aimed to define the molecular mechanisms controlling PD-1 expression and its therapeutic targeting in melanoma cells. Our team identified a melanoma cell-intrinsic type I interferon-JAK/STAT signaling circuit regulating the amount of PD-1 in tumor cells. We further discovered that inhibition of this pathway not only reversed induction of PD-1 on melanoma cells, but also reduced the efficacy of PD-1 checkpoint therapy. Our work thus cautions against combining JAK or IFNAR antagonists with PD-1 inhibitors, given that this regimen may weaken the effectiveness of immune checkpoint monotherapy. 

What knowledge gaps does your study help to fill? 

This work builds off our previously published studies identifying PD-1 as a tumor cell-intrinsic growth promoting receptor in melanoma and Merkel cell carcinoma, the inhibition of which suppresses cancer progression. Here, we newly define a regulatory pathway controlling PD-1 levels on melanoma cells and how inhibition of this pathway unintentionally disrupts therapeutic efficacy of immune checkpoint blockade. We can use these findings to optimize immunotherapeutic responses for patients with melanoma, and potentially even other cancer types. 

How did you conduct your study? 

To understand the mechanisms that govern PD-1 checkpoint expression in melanoma cells, we focused on established cytokine networks known to regulate PD-1 in immune cells. We hypothesized that these mediators would have a similar role in modulating melanoma cell-PD-1 levels. Through our work, we discovered that a type I interferon cytokine pathway intrinsic to melanoma cells critically controls tumor cell-PD-1 expression. We also found that disruption of type I interferon signaling reduces melanoma-PD-1 expression and resultant efficacy of immune checkpoint therapy. 

What are the implications? 

Type I interferon antagonists, including JAK inhibitors and IFNAR1 antibodies, currently prescribed in the clinic for multiple autoimmune conditions such as psoriasis, atopic dermatitis, vitiligo and lupus may potentially suppress efficacy of PD-1 immune checkpoint therapy. Our work thus raises concern over using PD-1 checkpoint antibodies (e.g. nivolumab or pembrolizumab) with JAK inhibitors (e.g. ruxolitinib, utabacitinib, deucravacitinib) or IFNAR1 antibodies (e.g. anifrolumab). 

What are the next steps? 

Next steps include dissecting roles of type I interferon signaling and inhibition not only on melanoma cell-PD-1 expression, targeting, and checkpoint efficacy, but also in additional cancer types as well as in diverse immune and non-immune cell lineages within the tumor microenvironment. Identifying additional regulatory networks controlling tumor cell-PD-1 expression and their effects on immunotherapeutic outcomes are also major thrusts of our ongoing research. Our overall goal is to leverage these findings to improve immune checkpoint therapeutic responses in cancer patients. 

Authorship: In addition to Drs. Schatton and Barthel, other BWH authors include Julia Holzgruber, Christina Martins, Zsofi Kulcsar, Alexandra Duplaine, Erik Rasbach, Laure Migayron, Praveen Singh, Edith Statham, and Matthew R. Ramsey. Additional non-BWH authors include Jennifer Landsberg, Katia Boniface, Julien Seneschal, Wolfram Hoetzenecker, Emma Berdan and Shannah Ho Sui. 

Funding: This work was support by a Research Grant from the Dermatology Foundation, Milstein Research Scholar Award from the American Skin Association, Fund to Sustain Research Excellence from the Brigham Research Institute at Brigham and Women's Hospital and NIH/NCI grants (R01CA190838, R01CA247957 and R01CA258637). Partial support was provided by a Developmental Project Grant from the Harvard Stem Cell Institute, Klaus-Wolff Fellowships from the Austrian Society of Dermatology and Venereology, Marietta Blau-Grant from Austria's Agency for Education and Internationalisation, Research Fellowship from the European Academy of Dermatology and Venereology, and a Walter Benjamin Scholarship from the German Research Foundation.