Poznanski et al. demonstrated that NK cells harvested from lung cancer patients could be activated and expanded ex vivo. Once activated, these NK cells (exNK) acquired direct antitumor cytotoxicity and the pro-inflammatory capability to upregulate PD-L1 expression on tumor cells (via IFNγ), salvaging tumor killing by exhausted TILs. Adoptive transfer of human exNK cells in an NRG mouse tumor model resulted in reduced tumor burden, and combined exposure to exNK and PD-1 blockade resulted in robust synergistic ex vivo tumor cell killing, suggesting a potential therapeutic benefit of autologous exNKs for patients undergoing PD-1 blockade therapy.

Contributed by Margot O’Toole

ABSTRACT: Lung cancer remains the leading cause of cancer death worldwide despite the significant progress made by immune checkpoint inhibitors, including programmed death receptor-1 (PD1)/PD ligand 1 (PDL1)-blockade therapy. PD1/PDL1-blockade has achieved unprecedented tumor regression in some patients with advanced lung cancer. However, the majority of patients fail to respond to PD1/PDL1 inhibitors. The high rate of therapy non-response results from insufficient PDL1 expression on most patients' tumors and the presence of further immunosuppressive mechanisms in the tumor microenvironment. Here, we sensitize non-responding tumors from patients with lung cancer to PD1-blockade therapy using highly cytotoxic expanded natural killer (NK) cells. We uncover that NK cells expanded from patients with lung cancer dismantle the immunosuppressive tumor microenvironment by maintaining strong antitumor activity against both PDL1+ and PDL1- patient tumors. In the process, through a contact-independent mechanism involving interferon γ, expanded NK cells rescued tumor killing by exhausted endogenous TILs and upregulated the tumor proportion score of PDL1 across patient tumors. In contrast, unexpanded NK cells, which are susceptible to tumor-induced immunosuppression, had no effect on tumor PDL1. As a result, combined treatment of expanded NK cells and PD1-blockade resulted in robust synergistic tumor destruction of initially non-responding patient tumors. Thus, expanded NK cells may overcome the critical roadblocks to extending the prodigious benefits of PD1-blockade therapy to more patients with lung cancer and other tumor types.

Author Info: (1) McMaster Immunology Research Centre, Department of Medicine, McMaster University, Hamilton, Ontario, Canada. (2) McMaster Immunology Research Centre, Department of Medicine, Mc

Author Info: (1) McMaster Immunology Research Centre, Department of Medicine, McMaster University, Hamilton, Ontario, Canada. (2) McMaster Immunology Research Centre, Department of Medicine, McMaster University, Hamilton, Ontario, Canada. (3) McMaster Immunology Research Centre, Department of Medicine, McMaster University, Hamilton, Ontario, Canada. (4) McMaster Immunology Research Centre, Department of Medicine, McMaster University, Hamilton, Ontario, Canada. (5) McMaster Immunology Research Centre, Department of Medicine, McMaster University, Hamilton, Ontario, Canada. (6) Surgery, McMaster University, Hamilton, Ontario, Canada. (7) McMaster Immunology Research Centre, Department of Medicine, McMaster University, Hamilton, Ontario, Canada. (8) McMaster Immunology Research Centre, Department of Medicine, McMaster University, Hamilton, Ontario, Canada. (9) Surgery, McMaster University, Hamilton, Ontario, Canada. (10) McMaster Immunology Research Centre, Department of Medicine, McMaster University, Hamilton, Ontario, Canada ashkara@mcmaster.ca.