Suppression of immune reactivity by increased expression of co-inhibitory receptors has been discussed as a major reason as to why the immune system fails to control tumor development. Elucidating the co-inhibitory expression pattern of tumor-infiltrating lymphocytes in different cancer types will help to develop future treatment strategies. We characterized markers reflecting and affecting T-cell functionality by flow cytometry on lymphocytes isolated from blood, ascites and tumor from advanced ovarian cancer patients (n = 35). Significantly higher proportions of CD4+ and CD8+ T-cells expressed co-inhibitory receptors LAG-3, PD-1 and TIM-3 in tumor and ascites compared to blood. Co-expression was predominantly observed among intratumoral CD8+ T-cells and the most common combination was PD-1 and TIM-3. Analysis of 26 soluble factors revealed highest concentrations of IP-10 and MCP-1 in both ascites and tumor. Correlating these results with clinical outcome revealed the proportion of CD8+ T-cells without expression of LAG-3, PD-1 and TIM-3 to be beneficial for overall survival. In total we identified eight immune-related risk factors associated with reduced survival. Ex vivo activation showed tumor-derived CD4+ and CD8+ T-cells to be functionally active, assessed by the production of IFN-γ, IL-2, TNF-α, IL-17 and CD107a. Blocking the PD-1 receptor resulted in significantly increased release of IFN-γ suggesting potential reinvigoration. The ovarian tumor environment exhibits an inflammatory milieu with abundant presence of infiltrating immune cells expressing inhibitory checkpoints. Importantly, we found subsets of CD8+ T-cells with double and triple expression of co-inhibitory receptors, supporting the need for multiple checkpoint-targeting agents to overcome T-cell dysfunction in ovarian cancer.

There is a strong biological rationale for the augmentation of allogeneic natural killer (NK) cell therapies with a chimeric antigen receptor (CAR) to enhance acute myeloid leukemia (AML) targeting. CD38 is an established immunotherapeutic target in multiple myeloma and under investigation as a target antigen in AML. CD38 expression on NK cells and its further induction during ex vivo NK cell expansion represents a barrier to the development of a CD38 CAR-NK cell therapy. We set out to develop a CD38 CAR-NK cell therapy for AML, first by using an NK cell line which has low baseline CD38 expression and subsequently healthy donor expanded NK cells. To overcome anticipated fratricide due to NK cell CD38 expression when using primary expanded NK cells, we applied CRISPR/Cas9 genome editing to disrupt the CD38 gene during expansion achieving a mean knockdown efficiency of 84%. The resulting CD38 KD expanded NK cells, after expression of an affinity optimized CD38 CAR, showed reduced NK cell fratricide and an enhanced ability to target primary AML blasts. Furthermore, the cytotoxic potential of CD38 CAR-NK cells was augmented by pre-treatment of the AML cells with all-trans retinoic acid which drove enhanced CD38 expression offering a rational combination therapy. These findings support the further investigation of CD38 KD - CD38 CAR-NK cells as a viable immunotherapeutic approach to the treatment of AML.

Chronic graft-versus-host disease (cGVHD) is a debilitating complication arising in around half of all patients treated with an allogeneic hematopoietic stem cell transplantation. Even though treatment of severe cGVHD has improved during recent years, it remains one of the main causes of morbidity and mortality in affected patients. Biomarkers in blood that could aid in the diagnosis and classification of cGVHD severity are needed for the development of novel treatment strategies that can alleviate symptoms and reduce the need for painful and sometimes complicated tissue biopsies. Methods that comprehensively profile complex biological systems such as the immune system can reveal unanticipated markers when used with the appropriate methods of data analysis. Here, we used mass cytometry, flow cytometry, enzyme-linked immunosorbent assay, and multiplex assays to systematically profile immune cell populations in 68 patients with varying grades of cGVHD. We identified multiple subpopulations across T, B, and NK-cell lineages that distinguished patients with cGVHD from those without cGVHD and which were associated in varying ways with severity of cGVHD. Specifically, initial flow cytometry demonstrated that patients with more severe cGVHD had lower mucosal-associated T cell frequencies, with a concomitant higher level of CD38 expression on T cells. Mass cytometry could identify unique subpopulations specific for cGVHD severity albeit with some seemingly conflicting results. For instance, patients with severe cGVHD had an increased frequency of activated B cells compared to patients with moderate cGVHD while activated B cells were found at a reduced frequency in patients with mild cGVHD compared to patients without cGVHD. Moreover, results indicate it may be possible to validate mass cytometry results with clinically viable, smaller flow cytometry panels. Finally, no differences in levels of blood soluble markers could be identified, with the exception for the semi-soluble combined marker B-cell activating factor/B cell ratio, which was increased in patients with mild cGVHD compared to patients without cGVHD. These findings suggest that interdependencies between such perturbed subpopulations of cells play a role in cGVHD pathogenesis and can serve as future diagnostic and therapeutic targets.