Phenotypic and functional analysis in HER2+targeted therapy of human NK cell subpopulation according to the expression of FcεRIγ and NKG2C in breast cancer patients

Adaptive NK cells constitute an NK cell subpopulation, which expands after human cytomegalovirus (HCMV) infection. This subpopulation has stronger production of cytokines after CD16 stimulation, longer life and persistence than conventional NK cells and are, therefore, interesting tools for cancer immunotherapy. Since there is limited information on adaptive NK cells in cancer patients, we described this population phenotypically and functionally, by flow cytometry, in the context of HER2 + breast cancer (BC) directed therapy. We assessed HCMV status in 78 patients with BC. We found that, similarly to healthy donors (HD), a high proportion of BC patients were HCMV-positive, and nearly 72% of them had an adaptive NK cell subpopulation characterized by the loss of Fc epsilon RI gamma intracellular adaptor protein or the presence of NKG2C receptor. However, in BC patients, Fc epsilon RI gamma- and NKG2C + NK cell populations overlapped to a lesser extent than in HD. Otherwise, no profound phenotypic differences were found between BC patients and HD. Although Fc epsilon RI gamma- or NKG2C + NK cell subsets from BC patients produced more IFN-gamma than their Fc epsilon RI gamma + or NKG2C- NK cell counterparts, IFN-gamma production increased only when NK cells simultaneously expressed Fc epsilon RI gamma- and NKG2C + , whereas in HD the presence of NKG2C marker was sufficient to display greater functionality. Furthermore, in a group of patients treated with chemotherapy and Trastuzumab plus Pertuzumab, Fc epsilon RI gamma-NKG2C + and Fc epsilon RI gamma-NKG2C- NK cells retained greater functionality after treatment than Fc epsilon RI gamma + NKG2C- NK cells. These results suggest that the presence or magnitude of adaptive NK cell subsets might serve as a key determinant for therapeutic approaches based on antibodies directed against tumor antigens.

Automated summary

Adaptive NK cells, which expand after HCMV infection, have stronger cytokine production, longer life and persistence compared to conventional NK cells, making them valuable for cancer immunotherapy. In this study, adaptive NK cell subpopulations were characterized in HER2+ breast cancer patients and found to overlap to a lesser extent than in healthy donors. However, no significant phenotypic differences were observed between patients and donors. Additionally, the presence of both Fc epsilon RI gamma- and NKG2C+ was necessary for increased IFN-gamma production in patients, while the presence of NKG2C alone was sufficient in donors. These findings suggest that adaptive NK cell subsets may play a role in therapeutic approaches targeting tumor antigens.