Adoptive transfer of natural killer cells promotes the anti-tumor efficacy of T cells

Abstract

The density of NK cells in tumors correlates positively with prognosis in many types of cancers. The average number of infiltrating NK cells is, however, quite modest (approximately 30 NK cells/sq.mm), even in tumors deemed to have a “high” density of infiltrating NK cells. It is unclear how such low numbers of tumor-infiltrating NK cells can influence outcome. Here, we used ovalbumin-expressing tumor cell lines and TCR transgenic, OVA-specific cytotoxic T lymphocytes (OT-I-CTLs) to determine whether the simultaneous attack by anti-tumor CTLs and IL-2-activated NK (A-NK) cells synergistically increases the overall tumor cell kill and whether upregulation of tumor MHC class-I by NK cell-derived interferon-gamma (IFNγ) improves tumor-recognition and kill by anti-tumor CTLs. At equal E:T ratios, A-NK cells killed OVA-expressing tumor cells better than OT-I-CTLs. The cytotoxicity against OVA-expressing tumor cells increased by combining OT-I-CTLs and A-NK cells, but the increase was additive rather than synergistic. A-NK cells adenovirally-transduced to produce IL-12 (A-NKIL-12) produced high amounts of IFNγ. The addition of a low number of A-NKIL-12 cells to OT-I-CTLs resulted in a synergistic, albeit modest, increase in overall cytotoxicity. Pre-treatment of tumor cells with NK cell-conditioned medium increased tumor MHC expression and sensitivity to CTL-mediated killing. Pre-treatment of CTLs with NK cell-conditioned medium had no effect on CTL cytotoxicity. In vivo, MHC class-I expression by OVA-expressing B16 melanoma lung metastases increased significantly within 24–48 hours after adoptive transfer of A-NKIL-12 cells. OT-I-CTLs and A-NKIL-12 cells localized selectively and equally well into OVA-expressing B16 lung metastases and treatment of mice bearing 7-days-oldOVA-B16 lung metastases with both A-NKIL-12 cells and OT-I-CTLs lead to a significant prolongation of survival. Thus, an important function of tumor-infiltrating NK cells may be to increase tumor cell expression of MHC class-I through secretion of IFNγ, to prepare them for recognition by tumor-specific CTLs.

A natural killer–dendritic cell axis defines checkpoint therapy–responsive tumor microenvironments

“…It has long been acknowledged that NK cells can have a greater effect on tumors than their ability to kill cancer cells alone 21,25 but their role as critical producers of Flt3L and the formation of an apparently non-lytic interaction was not known. Our studies suggest that targeting NK cells by either increasing the numbers in the TME or activating these cells should increase the levels of FLT3LG in the tumor and in turn increase the levels of protective SDCs in the TME, either through skewed differentiation of precursor DCs in the tissue or prolonged survival of differentiated SDCs, providing increased responses to anti-PD-1 immunotherapy.…”

Localized Interleukin-12 for Cancer Immunotherapy

“…In particular, NK IL−12 plus IL-2 treatment increased survival by 11.5 days, while NK IL−12 plus CTL and IL-2 prolonged survival for 16.5 days. Nevertheless, all mice eventually succumbed to the disease and no stable tumor regressions were reported (319).…”

“…Natural killer (NK) cells and chimeric antigen receptor (CAR) T cells have also been transduced to produce IL-12. In one recent study, primary NK cells isolated from C57BL/6 mice and transduced to express IL-12 (NK IL−12 ) increased MHC class I expression in Ova-transfected melanoma cells (B16M05) compared to mock plasmid transduced NK cells (319). Combination treatment studies involving tumor-specific cytotoxic T lymphocytes (CTLs), PEGylated IL-2, and activated NK IL−12 revealed that only groups containing activated NK IL−12 demonstrated statistically significant prolonged survival over mock constructs, untreated, and CTL alone controls in B16-OVA tumor bearing mouse models.…”

Adoptive Cell Therapy in Treating Pediatric Solid Tumors

“…Since NK cells are the primary effector cells in antibody-dependent cell cytotoxicity, studies have combined adoptively transferred NK cells with anti-GD2 mAb therapy to improve responses [53, 54]. An advantage of using NK cells is that, as mediators of innate immunity, they induce local release of Type-I interferons, which induce MHC upregulation by neuroblastoma cells, thus eliciting recognition of infiltrating CTLs [23, 55]. In a phase 2 clinical trial, relapsed or refractory neuroblastoma patients receiving a combination of chemotherapy, antibody therapy, cytokines and haplo-identical NK cells achieved a response rate of 61.5% [53].…”