CD20 expression regulates CD37 levels in B-cell lymphoma - implications for immunotherapies.

Rituximab (RTX) plus chemotherapy (R-CHOP) applied as a first-line therapy for lymphoma leads to a relapse in approximately 40% of the patients. Therefore, novel approaches to treat aggressive lymphomas are being intensively investigated. Several RTX-resistant (RR) cell lines have been established as surrogate models to study resistance to R-CHOP. Our study reveals that RR cells are characterized by a major downregulation of CD37, a molecule currently explored as a target for immunotherapy. Using CD20 knockout (KO) cell lines, we demonstrate that CD20 and CD37 form a complex, and hypothesize that the presence of CD20 stabilizes CD37 in the cell membrane. Consequently, we observe a diminished cytotoxicity of anti-CD37 monoclonal antibody (mAb) in complement-dependent cytotoxicity in both RR and CD20 KO cells that can be partially restored upon lysosome inhibition. On the other hand, the internalization rate of anti-CD37 mAb in CD20 KO cells is increased when compared to controls, suggesting unhampered efficacy of antibody drug conjugates (ADCs). Importantly, even a major downregulation in CD37 levels does not hamper the efficacy of CD37-directed chimeric antigen receptor (CAR) T cells. In summary, we present here a novel mechanism of CD37 regulation with further implications for the use of anti-CD37 immunotherapies.

Hypermethylation of CD19 promoter enables antigen-negative escape to CART-19 in vivo and in vitro.

BACKGROUND: Anti-CD19 chimeric antigen receptor T cells (CART-19) frequently induce remissions in hemato-oncological patients with recurred and/or refractory B-cell tumors. However, malignant cells sometimes escape the immunotherapeutic targeting by CD19 gene mutations, alternative splicing or lineage switch, commonly causing lack of CD19 expression on the surface of neoplastic cells. We assumed that, in addition to the known mechanisms, other means could act on CD19 to drive antigen-negative relapse. METHODS: Herein, we studied the mechanism of antigen loss in an in vivo CD19-negative recurrence model of chronic lymphocytic leukemia (CLL) to CART-19, established using NOD-scid IL2Rgnull mice and HG3 cell line. We validated our findings in vitro in immortalized B-cell lines and primary CLL cells. RESULTS: In our in vivo CLL recurrence model, up to 70% of CART-19-treated mice eventually recurred with CD19-negative disease weeks after initial positive response. We found that the lack of CD19 expression was caused by promoter DNA hypermethylation. Importantly, the expression loss was partially reversible by treatment with a demethylating agent. Moreover, this escape mechanism was common for 3 B-cell immortalized lines as well as primary CLL cells, as assessed by in vitro coculture experiments. CONCLUSIONS: Epigenetically driven antigen escape could represent a novel, yet at least partially reversible, means of CD19 loss to CART-19 in B-cell tumors.

Self-stigma in psychiatric patients--standardization of the ISMI scale.

OBJECTIVE: Self-stigma in psychiatric patients is an issue deserving both research and therapeutic attention. The objective of the present study was to evaluate the psychometric properties of a Czech version of the Internalized Stigma of Mental Illness (ISMI) scale assessing the levels of self-stigma in individuals with mental disorders. METHODS: It consists of 29 items classified into 5 subscales, namely alienation, stereotype endorsement, perceived discrimination, social withdrawal and stigma resistance. The study group comprised 369 patients with a mean age of 41.5±13.3 years, of whom 210 (56.6%) were females. RESULTS: The most frequent diagnosis was neurotic disorders (46.1%), followed by affective disorders (18.4%), substance use disorders (13.3%), psychotic disorders (10.8%), personality disorders (9.5%) and organic disorders (1.6%). Reliability of the scale was evaluated by internal consistency analysis (α=0.91), the split-half method (Spearman-Brown coefficient: 0.93) and test-retest at 3 weeks from the first measurement (N=17; r=0.90, p<0.05). CONCLUSION: Exploratory factor analysis of the scale was performed, its validity was verified and norms were established that were based on T-scores and sten scores for the entire scale and individual subscales. The Czech translation of the ISMI has adequate psychometric properties.