IL-2 decreased PU.1 and PD-1 expression in NK-cells in NSCLC patients

The transcription factor PU box binding-1 (PU.1), which is encoded by the SPI1 gene, is required for the development of most myeloid cell lineages as well as B- and T cells. Consequently, an alteration of the SPI1 gene and thus PU.1 can have severe impact on the immune system. However, the role of PU.1 in cancer is not yet fully understood. In this study, we were looking for a hint on the influence of PU.1 expression on various cell types during non-small cell lung cancer (NSCLC). To start the investigation, we isolated peripheral blood mononuclear cells (PBMCs) from patients with NSCLC as well as from healthy controls. The PBMCs were cultured with different cytokines for 4 days and subsequently analyzed by flow cytometry. Furthermore, RNA was isolated from the PBMCs and qPCR was performed. The qPCR results showed induced PU.1 mRNA levels in NSCLC patients in relation to GAPDH, compared to control patients. By flow cytometry, we could detect higher PU.1 expression in CD56+ Natural killer (NK) cells from lung cancer patients compared to the healthy donors. Moreover, NK-cells from lung cancer patients, in contrast to healthy controls, expressed the immunosuppressive protein Programmed Death 1 (PD-1). Furthermore, PBMCs from NSCLC patients that were cultured with aCD3/aCD28 antibodies, showed suppression of PU.1 as well as PD-1 in NK-cells, which was even more prominent after addition of IL-2. These preliminary data suggest, that conditions inducing T cell activation like IL-2 and antiCD3/antiCD28 stimulation, can downregulate both the transcription factor PU.1 and PD-1 in NK-cells in tumor patients. Thus, improvement of current immunotherapy could use additional IL-2, which targets PU-1 as well as PD-1 in NK cells in lung cancer.