Characterization of NK Cells Under First Line Advanced Therapy Either as Curative Therapy for Metastatic Melanoma or as Adjuvant Therapy for High-risk of Recurrence

Natural Killer (NK) lymphocytes are cytotoxic effectors of the innate immune response that are involved in different phases of tumor immunosurveillance. These lymphocytes are activated upon contact with tumor cells and exert direct cytotoxic activity without prior immunization. Activated NK lymphocytes produce cytokines, including IFN-γ and TNF-α, which induce and maintain an activation of the adaptive immune response by CD8+ lymphocytes. Numerous studies in various experimental tumor models highlight the role of NK cells in the control of metastasis.

Our previous work has shown that NK cells infiltrate primary melanomas, that metastatic patients have altered blood NKs, and furthermore, that chemotherapy modulates their functional status. Investigators also observed a particular distribution of gene polymorphisms encoding NK activating receptors of stage IV melanoma patients compared to healthy donors. Finally, the investigator described a novel population of NK lymphocytes in metastatic lymph nodes draining melanoma NK cell activation is regulated by a balance between activating receptors (NKG2D, NCR) and inhibitory receptors that bind to modulatory classical and non-classical HLA-I molecules (HLA-E and G). More recently it has been shown that Lc NKs also express checkpoint receptors including CD96/TIGIT, NKG2A, TIM3 and PD-1 (the latter 2 are present on LcTs) that negatively modulate NK activation. The possibility of activating the lytic and secretory function of Lc NKs by interfering with these receptors may represent an alternative yet to be explored in immunotherapy treatments.

More recently, th investigator have developed a program to understand the interactions between tumor mutational profile, treatment with targeted therapies and NK immunogenicity. the investigator have a panel of melanoma lines with and without the BRAF V600E mutation and vemurafenib resistant variants have been obtained from some mutated lines. the investigator evaluated the impact of treatment and resistance to BRAF inhibition on Lc NK recognition and lysis. yhe investigator showed that a BRAF inhibitor, vemurafenib, decreased membrane and soluble expression of MICA/B and ULBP2, ligands for NKG2D, an activating receptor present on Lc NKs and certain populations of Lc T cells, in all BRAF mutated lines treated. For 6 of the 7 mutated lines, modulations of NK ligands expression by vemurafenib correlated with a slight decrease in NK cytotoxic functions.

Vemurafenib-resistant (R) variants were generated and their characteristics were compared to those of sensitive (S) lines. The acquisition of resistance to vemurafenib induces a significant increase in NK functions (IFNg secretion and target lysis). The responsible mechanisms involve both the expression of NK receptor ligands and the modulation of death domain receptors (Fas, TRAILRII). Transcriptome analyses reveal different targets of interest in the three pairs of S/R melanoma lines carrying the BRAF V600E mutation and distinct additional mutations (submitted manuscript).

Based on our recent results our hypothesize that Lc NKs are important players in tumor immunosurveillance during current treatments of melanoma patients. Immunotherapy approaches targeting these effectors may be of interest in combinations with targeted therapies or immunotherapies. The frequency of intratumoral Lc NKs has been shown to correlate with the presence of stimulatory dendritic cells and this environment is required for a response to anti-PD1 immunotherapy. Innovative antibodies are being developed to activate the antitumor functions of NK cells