Ex vivo-expanded NK cells from blood and ascites of ovarian cancer patients are cytotoxic against autologous primary ovarian cancer cells.

Ovarian cancer (OC) is the leading cause of gynecological cancer-related death in North America. Most ovarian cancer patients (OCPs) experience disease recurrence after first-line surgery and chemotherapy; thus, there is a need for novel second-line treatments to improve the prognosis of OC. Although peripheral blood-derived NK cells are known for their ability to spontaneously lyse tumour cells without prior sensitization, ascites-derived NK cells (ascites-NK cells) isolated from OCPs exhibit inhibitory phenotypes, impaired cytotoxicity and may play a pro-tumourigenic role in cancer progression. Therefore, it is of interest to improve the cytotoxic effector function of impaired OCP ascites-NK cells at the tumour environment. We investigated the efficacy of using an artificial APC-based ex vivo expansion technique to generate cytotoxic, expanded NK cells from previously impaired OCP ascites-NK cells, for use in an autologous model of NK cell immunotherapy. We are the first to obtain a log-scale expansion of OCP ascites-NK cells that upregulate the surface expression of activating receptors NKG2D, NKp30, NKp44, produce robust amounts of anti-tumour cytokines in the presence of OC cells and mediate direct tumour cytotoxicity against ascites-derived, primary OC cells obtained from autologous patients. Our findings demonstrate that it is possible to generate cytotoxic OCP ascites-NK cells from previously impaired OCP ascites-NK cells, which presents a promising immunotherapeutic target for the second-line treatment of OC. Future work should focus on evaluating the in vivo efficacy of autologous NK cell immunotherapy through the intraperitoneal delivery of NK cell expansion factors to a preclinical xenograft mouse model of human OC.

Type I interferon signalling is not required for the induction of endotoxin tolerance.

Endotoxin, or LPS tolerance, is an immunomodulatory mechanism that results in a significantly diminished response to secondary LPS exposure, which may serve to protect the host against endotoxic shock. Type I interferons (IFNs) are cytokines released upon LPS binding to TLR4 and have been shown to have immunomodulatory properties. Due to this regulatory function of type I IFN, we aimed to investigate the role of type I IFN signalling in LPS tolerance. Our data suggests that type I IFN does not play a role in LPS tolerance in vitro, as both wild type and IFNAR1-/- peritoneal macrophages showed reduced cytokine production after secondary LPS exposure. Furthermore, both wild type and IFNAR1-/- mice were protected from a lethal dose of LPS after receiving three small doses to induce tolerance. However, IFNAR-/- mice seemed to recover faster than wild type mice, suggesting type I IFN signalling plays a detrimental role in LPS-induced sepsis. Although type I IFN may have a regulatory function in microbial infections, it does not seem to play a role in endotoxin tolerance. Type I IFN involvement in bacterial infection remains complex and further studies are needed to define the regulatory function of type I IFN signalling.

Type I IFN signaling on dendritic cells is required for NK cell-mediated anti-tumor immunity.

NK cells play a vital role in innate anti-tumor immunity. Crosstalk between NK cells and dendritic cells (DCs) has come to the forefront in protection against tumors in the context of DC vaccines. We previously discovered that NK cell activation mediates the anti-tumor activity elicited by DC vaccines in response to melanoma tumor challenge in a murine lung metastasis model. In this study, we sought to explore the mechanism behind this NK-DC communication, specifically looking at the involvement of IL-15 and type I IFN signaling. Using DCs from IL-15(-/-) and IL-15Rα(-/-) mice, we found that the anti-tumor effect of the vaccine remained comparable with DCs from wild type mice. Moreover, DCs derived from IFN-α/ßR(-/-) mice also maintained their anti-tumor effect. Interestingly, endogenous DCs were found to accumulate in the draining lymph nodes post-immunization and their depletion abolished the anti-tumor effect of the vaccine. Our findings suggest the important role that type I IFN signaling and endogenous DCs play in DC vaccine-mediated anti-tumor protection. Our data suggest that type I IFNs from vaccine DCs activate host DCs to provide NK cell-mediated anti-tumor immunity.