Non-invasive fluorescence imaging for tracking immune cells in preclinical models of immunotherapy.

The field of cellular immunotherapy for cancer has experienced exponential growth over the last decade. Several chimeric antigen receptor T cell products have already received FDA approval, which has stimulated growth and enthusiasm for other cellular therapies. Preclinical models are critical steps in the development of these products, and understanding their in vivo trafficking and persistence are critical components of their efficacy and toxicity analogous to volume of distribution and tissue penetration in small molecule therapeutics. Thus, well-established preclinical methodologies for following cells after adoptive transfer are important to understanding immune cell trafficking to, and persistence in, tumors or organs of interest. Here, we describe a quick and reliable method for labeling and in vivo tracking of immune cells adoptively transferred into small animal models by using in vivo fluorescent imaging.

CD38 deletion of human primary NK cells eliminates daratumumab-induced fratricide and boosts their effector activity.

Multiple myeloma (MM) is a plasma cell neoplasm that commonly expresses CD38. Daratumumab (DARA), a human monoclonal antibody targeting CD38, has significantly improved the outcome of patients with relapsed or refractory MM, but the response is transient in most cases. Putative mechanisms of suboptimal efficacy of DARA include downregulation of CD38 expression and overexpression of complement inhibitory proteins on MM target cells as well as DARA-induced depletion of CD38high natural killer (NK) cells resulting in crippled antibody-dependent cellular cytotoxicity (ADCC). Here, we tested whether maintaining NK cell function during DARA therapy could maximize DARA-mediated ADCC against MM cells and deepen the response. We used the CRISPR/Cas9 system to delete CD38 (CD38KO) in ex vivo expanded peripheral blood NK cells. These CD38KO NK cells were completely resistant to DARA-induced fratricide, showed superior persistence in immune-deficient mice pretreated with DARA, and enhanced ADCC activity against CD38-expressing MM cell lines and primary MM cells. In addition, transcriptomic and cellular metabolic analysis demonstrated that CD38KO NK cells have unique metabolic reprogramming with higher mitochondrial respiratory capacity. Finally, we evaluated the impact of exposure to all-trans retinoic acid (ATRA) on wild-type NK and CD38KO NK cell function and highlighted potential benefits and drawbacks of combining ATRA with DARA in patients with MM. Taken together, these findings provide proof of concept that adoptive immunotherapy using ex vivo expanded CD38KO NK cells has the potential to boost DARA activity in MM.

Natural killer cell adoptive immunotherapy: Coming of age.

Cell therapy is a promising alternative to harsh chemotherapy and radiation therapy for cancer. Natural killer (NK) cells in particular have great potential for direct use in adoptive immunotherapy (AI) for cancer and to improve the graft-vs-leukemia (GVL) effect of hematopoietic stem cell transplants (HSCTs). NK cell number and function are associated with a strong GVL effect without inducing graft-versus-host disease in most settings. Clinical trials demonstrating the therapeutic role of NK cells in HSCT recipients or testing the safety and efficacy of AI with NK cells have been primarily directed at treating acute myeloid leukemia, although investigators have used NK cells for treatment of other hematological diseases, sarcomas, carcinomas, and brain tumors. Major challenges must be overcome in making NK cell-based therapy cost-effective, the most important being the need to collect or generate an adequate number of effector cells. In this review, we discuss protocols for isolation, expansion, and in vitro propagation of large quantities of functional NK cells that meet the criteria for clinical applications. Among the methods described are the use of bioreactors for scaling up production and expansion of NK cells in the presence of interleukins and feeder cells. We also discuss novel methodologies that optimize the generation of clinical grade NK-cell products for AI.

IL-12 and IL-27 sequential gene therapy via intramuscular electroporation delivery for eliminating distal aggressive tumors.

Eradication of residual malignancies and metastatic tumors via a systemic approach is the key for successfully treating cancer and increasing cancer patient survival. Systemic administration of IL-12 protein in an acute large dose is effective but toxic. Systemic administration of IL-12 gene by persistently expressing a low level of IL-12 protein may reduce the systemic toxicity but only eradicates IL-12-sensitive tumors. In this study, we discovered that sequential administration of IL-12- and IL-27-encoding DNA, referred to as sequential IL-12-->IL-27 (IL-12 administration followed by IL-27 administration 10 d after) gene therapy, not only eradicated IL-12-sensitive CT26 tumors from 100% of mice but also eradicated the highly malignant 4T1 tumors from 33% of treated mice in multiple independent experiments. This IL-12-->IL-27 sequential gene therapy is not only superior to IL-12-encoding plasmid DNA given a total of two times at a 10-d interval sequential gene therapy for eliminating tumors but also for inducing CTL activity, increasing T cell infiltration into tumors, and yielding a large number of tumor-specific IFN-gamma-positive CD8 T cells. Notably, depletion of either T or NK cells during the IL-27 treatment phase reverses tumor eradication, suggesting an NK cell requirement for this sequential gene therapy-mediated tumor eradication. Both reversal of the administration sequence and coadministration of IL-12 and IL-27 impaired tumor eradication in 4T1 tumor-bearing mice. This IL-12-->IL-27 sequential gene therapy, via sequential administration of IL-12- and IL-27-encoding plasmid DNA into tumor-bearing mice through i.m. electroporation, provides a simple but effective approach for eliminating inaccessible residual tumors.