In contrast to donor T cells, natural killer (NK) cells are known to mediate anti-cancer effects without the risk of inducing graft-versus-host disease (GvHD). In order to improve cytotoxicity against resistant cancer cells, auspicious efforts have been made with chimeric antigen receptor (CAR) expressing T- and NK cells. These CAR-modified cells express antigen receptors against tumor-associated surface antigens, thus redirecting the effector cells and enhancing tumor-specific immunosurveillance. However, many cancer antigens are also expressed on healthy tissues, potentially leading to off tumor/on target toxicity by CAR-engineered cells. In order to control such potentially severe side effects, the insertion of suicide genes into CAR-modified effectors can provide a means for efficient depletion of these cells. While CAR-expressing T cells have entered successfully clinical trials, experience with CAR-engineered NK cells is mainly restricted to pre-clinical investigations and predominantly to NK cell lines. In this review we summarize the data on CAR expressing NK cells focusing on the possible advantage using these short-lived effector cells and discuss the necessity of suicide switches. Furthermore, we address the compliance of such modified NK cells with regulatory requirements as a new field in cellular immunotherapy.

The purpose of this study was to determine the effect of curcumin on Survivin/BIRC5 and on the role of signal transducer and activator of transcription 3 (STAT3) activation in Survivin/ BIRC5. We incubated two pancreatic cancer cell lines with different amounts of curcumin. This resulted in a downregulation of proliferation in all cell lines tested. The expression of Survivin/BIRC5 on mRNA and protein level was significantly downregulated and the phosphorylation of STAT3 was blocked. Treatment of pancreatic cancer cells with curcumin resulted in an induction of apoptosis. The results indicate that curcumin inhibits several key factors in cancer cellular pathways and may be of interest in pancreatic cancer.

Abbreviations: ADCC, antigen-dependent cellular cytotoxicity; HNSCC, head-and-neck squamous cell carcinoma; HSCT, haploidentical stem cell transplantation; KIR, killer cell immunoglobulin-like receptor; NCR, natural cytotoxicity receptor; NK, natural killer; NKG2D, natural-killer group 2, member D; vitsMICA/NKG2DL, soluble major histocompatibility complex Class I chain-related peptide A; TGFb1, transforming growth factor beta 1; TIEM, tumor immune escape mechanismDisseminated head-and-neck squamous cell carcinoma (HNSCC) escapes immune surveillance and thus frequently manifests as fatal disease. Here, we report on the distribution of distinct immune cell subpopulations, natural killer (NK) cell cytotoxicity and tumor immune escape mechanisms (TIEMs) in 55 HNSCC patients, either at initial diagnosis or present with tumor relapse. Compared to healthy controls, the regulatory NK cells and the ratio of pro/antiinflammatory cytokines were decreased in HNSCC patients, while soluble major histocompatibility complex Class I chain-related peptide A (sMICA) and transforming growth factor b 1 (TGFb 1 ) plasma levels were markedly elevated. Increased sMICA and TGFb 1 concentrations correlated with tumor progression and staging characteristics in 7 follow-up HNSCC patients, with significantly elevated levels of both soluble factors from the time of initial diagnosis to that of relapse. Patient plasma containing elevated sMICA and TGFb 1 markedly impaired NKG2D-dependent cytotoxicity against HNSCC cells upon incubation with patient-derived and IL-2 activated NK cells vs. those derived from healthy donors. Decreased antitumor recognition was accompanied by reduced NKG2D expression on the NK cell surface and an enhanced caspase-3 activity. In-vitro blocking and neutralization experiments demonstrated a synergistic negative impact of sMICA and TGFb 1 on NK cell functionality. Although we previously showed the feasibility and safety of transfer of allogeneic donor NK cells in a prior clinical study encompassing various leukemia and tumor patients, our present results suggest the need for caution regarding the sole use of adoptive NK cell transfer. The presence of soluble NKG2D ligands in the plasma of HNSCC patients and the decreased NK cell cytotoxicity due to several factors, especially TGFb 1 , indicates timely depletion of these immunosuppressing molecules may promote NK cell-based immunotherapy.