Interleukin-2 activated NK cells do not use the CD95L- and TRAIL-pathways in the rapid induction of apoptosis of rat colon carcinoma CC531s cells

Secretory TRAIL-Armed Natural Killer Cell-Based Therapy: In Vitro and In Vivo Colorectal Peritoneal Carcinomatosis Xenograft

Since its discovery in 1995, TNF-related apoptosis-inducing ligand (TRAIL) has sparked growing interest among oncologists due to its remarkable ability to induce apoptosis in malignant human cells, but not in most normal cells. However, one major drawback is its fast clearance rate in vivo Thus, the development of an alternative means of delivery may increase the effectiveness of TRAIL-based therapy. In this study, we developed a secretory TRAIL-armed natural killer (NK) cell-based therapy and assessed its cytotoxic effects on colorectal cancer cells and its tumoricidal efficacy on colorectal peritoneal carcinomatosis xenograft. We generated genetically modified NK cells by transduction with a lentiviral vector consisting of a secretion signal domain, a trimerization domain, and an extracellular domain of the TRAIL gene. These NK cells secreted a glycosylated form of TRAIL fusion protein that induced apoptotic death. Intraperitoneally, but not intravenously, injected NK cells effectively accumulated at tumor sites, infiltrated tumor tissue, induced apoptosis, and delayed tumor growth. These results shed light on the therapeutic potential of genetically engineered NK cells to treat peritoneal carcinomatosis. Mol Cancer Ther; 15(7); 1591-601. ©2016 AACR.

Retention of viability, cytotoxicity, and response to IL-2, IL-15, or IFN-alpha by human NK cells after CD107a degranulation

NK cells represent a critical component of the host innate immune response to viral infection and tumor transformation. Nevertheless, the fate of recently degranulated NK cells subsequent to a primary target cell interaction remains largely unexplored. Here, we investigated the long-term viability and killing potential of human NK cells following target cell lysis using live-sorting of CD107a-degranulated NK cells. We observed that sorted CD107a+ NK cells exhibited continued lytic potential against a wide variety of target cells, including tumor and virally infected target cells. CD107a-positive- and CD107a-negative-sorted NK cells displayed similar long-term viability, killing potential, and response to inflammatory cytokines such as IL-2, IL-15, and IFN-alpha. Interestingly, we observed that the CD107a signature is remarkably stable over time and that recently degranulated NK cells exhibit an amplification of CD107 expression immediately following a target cell interaction. Together, our data expand previous data showing that NK cells retain the capacity to kill multiple target cells in succession and reveal that NK viability, cytotoxicity, and response to inflammatory cytokines are not altered following a primary target cell interaction. Overall, our data argue for the strength of the NK cell compartment in the continuous surveillance of tumor and virally infected cells in the body and highlight the use of using CD107a expression as a stable marker for NK cytotoxicity.

An improved method to study NK-independent mechanisms of MTLn3 breast cancer lung metastasis

To study the tumor cell autonomous processes of metastasis, an in vivo tumor metastasis model is required that excludes the involvement of the innate immune system. For this purpose we used the established syngeneic MTLn3 cell - Fischer 344 tumor model. MTLn3 cells are efficiently eradicated by NK cells in vivo. Using isolated cell systems, we provide evidence for apoptosis-induction by IL-2 activated NK cells, but not T-cells, despite the expression of MHC class I. This is largely mediated by the perforin/granzyme B pathway in MTLn3 cells in a caspase-dependent manner. Temporal in vivo depletion of NK cells by an antibody-based method, dramatically improved colonization of the lungs by MTLn3 cells, from 5 metastases in the untreated animals to 130 metastases in the NK-depleted animals. Thus, we improved the syngeneic MTLn3-Fischer 344 tumor model by temporal depletion of NK cells of which the advantages over the use of immunodeficient animals are evident.

Rat colon carcinoma cells that survived systemic immune surveillance are less sensitive to NK-cell mediated apoptosis

In order to form distant metastases, cells from the primary tumor have to detach, enter the blood- or lymph-compartment and escape immune surveillance. Here, we describe the selection of rat colon carcinoma cell lines (CC531s-m1 and CC531s-m2) that escaped from systemic immune surveillance; CC531s cells were injected into the v. jugularis of Wag/Rij rats, after three weeks the lung tumors were isolated, the tumor cells were cultured, characterized and injected again. The m1- and m2-cell lines were less susceptible for killing by syngeneic NK cells. Further characterization of this cell line showed a decreased sensitivity towards TRAIL- and CD95L-, but not to granzyme B-mediated apoptosis. In the m1- and m2-cells log-phase growth started earlier as compared to the parental cell line, whereas no changes were found in anchorage-dependent or anchorage-independent growth. After subcapsular injection of the m2-cell line into the liver of rats much more lung metastases were formed in comparison to injection of the parental cell line. In conclusion, the results suggest that the resistance of the m1- and m2-cells to NK cell-mediated apoptosis was associated with their capability to survive systemic immune surveillance and form metastases in vivo.