Characterization of the input material quality for the production of tisagenlecleucel by multiparameter flow cytometry and its relation to the clinical outcome

Tisagenlecleucel (tisa-cel) is a CD19^-specific CAR-T cell product approved for the treatment of relapsed/refractory (r/r) DLBCL or B-ALL. We have followed a group of patients diagnosed with childhood B-ALL (n = 5), adult B-ALL (n = 2), and DLBCL (n = 25) who were treated with tisa-cel under non-clinical trial conditions. The goal was to determine how the intensive pretreatment of patients affects the produced CAR-T cells, their in vivo expansion, and the outcome of the therapy. Multiparametric flow cytometry was used to analyze the material used for manufacturing CAR-T cells (apheresis), the CAR-T cell product itself, and blood samples obtained at three timepoints after administration. We present the analysis of memory phenotype of CD4/CD8 CAR-T lymphocytes (CD45RA, CD62L, CD27, CD28) and the expression of inhibitory receptors (PD-1, TIGIT). In addition, we show its relation to the patients' clinical characteristics, such as tumor burden and sensitivity to prior therapies. Patients who responded to therapy had a higher percentage of CD8⁺CD45RA⁺CD27⁺ T cells in the apheresis, although not in the produced CAR-Ts. Patients with primary refractory aggressive B-cell lymphomas had the poorest outcomes which was characterized by undetectable CAR-T cell expansion in vivo. No clear correlation of the outcome with the immunophenotypes of CAR-Ts was observed. Our results suggest that an important parameter predicting therapy efficacy is CAR-Ts' level of expansion in vivo but not the immunophenotype. After CAR-T cells' administration, measurements at several timepoints accurately detect their proliferation intensity in vivo. The outcome of CAR-T cell therapy largely depends on biological characteristics of the tumors rather than on the immunophenotype of produced CAR-Ts.

NPM1 and DNMT3A mutations are associated with distinct blast immunophenotype in acute myeloid leukemia

The immune system is important for elimination of residual leukemic cells during acute myeloid leukemia (AML) therapy. Anti-leukemia immune response can be inhibited by various mechanisms leading to immune evasion and disease relapse. Selected markers of immune escape were analyzed on AML cells from leukapheresis at diagnosis (N = 53). Hierarchical clustering of AML immunophenotypes yielded distinct genetic clusters. In the absence of DNMT3A mutation, NPM1 mutation was associated with decreased HLA expression and low levels of other markers (CLIP, PD-L1, TIM-3). Analysis of an independent cohort confirmed decreased levels of HLA transcripts in patients with NPM1 mutation. Samples with combined NPM1 and DNMT3A mutations had high CLIP surface amount suggesting reduced antigen presentation. TIM-3 transcript correlated not only with TIM-3 surface protein but also with CLIP and PD-L1. In our cohort, high levels of TIM-3/PD-L1/CLIP were associated with lower survival. Our results suggest that AML genotype is related to blast immunophenotype, and that high TIM-3 transcript levels in AML blasts could be a marker of immune escape. Cellular pathways regulating resistance to the immune system might contribute to the predicted response to standard therapy of patients in specific AML subgroups and should be targeted to improve AML treatment.

The Relationship of Kynurenine and Neopterin Levels and Their Association with a Selection of Other Immune Markers in Chronic Myeloid Leukaemia Patients

Among malignant diseases, chronic myeloid leukaemia (CML) is one of the best suited candidates for immunotherapy. For this purpose it is necessary to broaden the present knowledge on the immunology of this disease. As a part of such a project, the levels of kynurenine (KYN) and neopterin (NPT) were studied in 28 CML patients and in the same number of healthy subjects. At diagnosis, both KYN and NPT levels were found to be elevated in a significant portion of the patients and dependent on their leukocyte count. As in the case of KYN, increased NPT levels dropped after achieving remission. When correlating KYN and NPT levels with a selection of other markers tested, significant association was revealed only in the case of CRP and IL-6. However, there were several patients with increased KYN levels in whom NPT was not detected, and vice versa. The relapse of the disease observed in two patients was accompanied by an increased level of NPT in both cases, but by an increased level of KYN in only one of them. No significant correlation was found between KYN and NPT levels in sera taken at diagnosis. However, when the whole set of sera was taken into consideration, the association became statistically significant. Although the data obtained revealed a number of similarities between KYN and NPT production in CML patients, it also suggested a difference in the kinetics of these two biomarkers' production.

Immunology of chronic myeloid leukemia: current concepts and future goals

Although chronic myeloid leukemia is a rare malignancy, it has developed into a model system for the study of a variety of aspects of cancer biology and immunology. The introduction of tyrosine kinase inhibitors has resulted in a significant prolongation of the survival rates of chronic myeloid leukemia patients but has not resulted in a cure. There is a growing conviction that this aim can be achieved through immunotherapy. For this concept to be successful, a considerable increase in the present understanding of chronic myeloid leukemia immunology is required. The authors attempt to review and evaluate the current findings that demonstrate a number of immunological aberrations in patients prior to the start of any therapy and their normalization after achieving remission. They also discuss the recent clinical trials with experimental therapeutic vaccines and then present their own strategy on how to address the problem.

Properties of bcr-abl-transformed mouse 12B1 cells secreting interleukin-2 and granulocyte-macrophage colony-stimulating factor: I. Derivation, genetic stability, oncogenicity and immunogenicity

The highly oncogenic bcr-abl-transformed mouse (Balb/c) 12B1 cells were transfected with plasmids carrying genes for either mouse interleukin-2 (IL‑2) or the mouse granulocyte-macrophage colony-stimulating factor (GM‑CSF) and the gene for blasticidine resistance. From the transduced cells several clones widely differing in the production of either cytokine were isolated. For further experiments, clones with the highest secretion of the cytokines were selected. When administered subcutaneously to mice, the IL-2-secreting cell line was approximately hundred times less pathogenic than the parental cells. A portion of animals developed small, spontaneously regressing tumours and most of them became resistant to challenge with the parental cells. Cell populations from either solid tumours or from organs infiltrated by the tumour cells predominantly consisted of cells which did not produce IL-2 and had lost resistance to blasticidine. This indicated that the IL-2 secreting cells were genetically unstable in the course of their propagation in vivo. On the other hand, the GM‑CSF‑secreting cells were more pathogenic than the parental cells, induced extensive organ damage and remained genetically stable in the course of their growth in vivo. The pathogenicity of different GM‑CSF secreting clones directly depended on the magnitude of production of this cytokine. When used in the form of inactivated vaccines, the GM-CSF-secreting cells were more immunogenic than the IL-2-secreting cells. In comparative experiments, similar results were obtained with GM‑CSF- and IL-2-secreting cells derived from B210 cells, another bcr-abl transformed cell line.

Unexpected properties of endostatin-producing mouse BCR-ABL-transformed cells

We investigated whether a genetic modification of BCR-ABL-transformed mouse cells that resulted in endostatin (ES) production altered their oncogenic potential. Mouse B210 cells, which express p210bcr-abl fusion protein and induce leukemia-like disease and extremely rarely solid tumors after intravenous (i.v.) administration, were used. The cells were transfected with a plasmid carrying genes for mouse ES and resistance to blasticidine. Transduced cells were isolated in media supplemented with blasticidine. Production of ES was determined by Western blotting. For further tests, two clones were selected, and their pathogenicity after i.v. inoculation was tested. Compared with the parental B210 cells, the capability of both gene-modified cell clones to induce lethal leukemia was reduced. However, mice that did not succumb to leukemia subsequently developed solid tumors. They were composed of poorly differentiated cells with irregular nuclei and roughly granular chromatin and were well vascularized. FISH revealed the presence of the BCR-ABL fusion gene both in tumors and spleens. Immunohistological investigation of the tumors demonstrated the production of ES in vivo and the cell lines derived from the tumors produced detectable amounts of ES, this demonstrating that the formation of solid tumors was not associated with the loss or silencing of the ES gene.