Melanoma response to anti-PD-L1 immunotherapy requires JAK1 signaling, but not JAK2

Area of Science:

• Immunology
• Oncology
• Molecular Biology

Background:

• Immunotherapies targeting PD-1/PD-L1 improve melanoma survival but response rates are limited.
• Tumor response to interferon-gamma (IFN-γ) correlates with anti-PD-1 efficacy.
• Resistance to immunotherapy can be linked to JAK/STAT pathway dysfunction downstream of IFNGR1/2.

Purpose of the Study:

• To investigate the specific roles of JAK/STAT pathway members in mediating IFN-γ responses.
• To identify key mediators of IFN-γ-induced signaling relevant to immunotherapy.

Main Methods:

• Dissection of individual JAK/STAT pathway member functions.
• Assessment of IFN-γ-induced expression of MHC-I, MHC-II, and PD-L1.
• Evaluation of JAK inhibition in a mouse melanoma model combined with anti-PD-L1 therapy.
• Genetic manipulation of PTPN2 to amplify JAK/STAT signaling.

Main Results:

• JAK1 was identified as the primary mediator of IFN-γ signaling, crucial for inducing MHC-I, MHC-II, PD-L1, and cytostatic effects.
• JAK2 played a largely dispensable role in most IFN-γ-mediated effects.
• Combined JAK1/2 inhibition with anti-PD-L1 therapy partially impaired anti-tumor immune responses.
• Selective JAK2 inhibition appeared to enhance anti-PD-L1 therapy.
• Inhibition of PTPN2 potentiated IFN-γ responses both in vitro and in vivo.

Conclusions:

• JAK1 is a critical regulator of IFN-γ responses and PD-L1 expression in melanoma.
• JAK2 inhibition may enhance immunotherapy, while JAK1/2 inhibition could be detrimental.
• Enhancing JAK/STAT signaling, for example by inhibiting PTPN2, could be a strategy to improve immunotherapy efficacy in melanoma.