Modulation of BCL-2 in Both T Cells and Tumor Cells to Enhance Chimeric Antigen Receptor T-cell Immunotherapy against Cancer

Abstract

Chimeric Antigen Receptor T-cell (CART) immunotherapy led to unprecedented responses in patients with refractory/relapsed B-cell non-Hodgkin lymphoma (NHL); nevertheless, two-thirds of patients fail this treatment. Resistance to apoptosis is a key feature of cancer cells that associates with treatment failure. In 87 NHL patients treated with anti-CD19 CART, we found that chromosomal alteration of BCL-2, a critical anti-apoptotic regulator, in lymphoma cells was associated with reduced survival. Therefore, we combined CART19 with the FDA-approved BCL-2-inhibitor, venetoclax, and demonstrated in vivo synergy in venetoclax-sensitive NHL. However, higher venetoclax doses for venetoclax-resistant lymphomas resulted in CART toxicity. To overcome this limitation, we developed venetoclax-resistant CART by overexpressing mutated BCL-2(F104L) which is not recognized by venetoclax. Notably, BCL-2(F104L)-CART19 synergized with venetoclax in multiple lymphoma xenograft models. Furthermore, we uncovered that BCL-2 overexpression in T cells per se enhanced CART anti-tumor activity in preclinical models and in patients by prolonging CART persistence.

Apoptosis: aJanus bifronsin T-cell immunotherapy

“…Recently we reported that patients with lymphoma receiving venetoclax during bridging therapy prior CAR-T cell infusion achieved significant improvement in clinical response compared with patients treated with no venetoclax-included bridging therapy. 33 In line with our clinical observations, pretreatment of cancer cells with venetoclax enhanced CAR-T cell-mediated anticancer activity in vitro. 67 These preclinical and clinical data strongly suggest that pre-sensitizing cancer cells with anti-apoptotic inhibitors could enhance the anticancer effect of T cell-based immunotherapy while reducing toxicity to T cells.…”

“…Using a combination of venetoclax and CAR-T therapy, we demonstrated a significant improvement in CAR-T cells’ anticancer activity against various lymphoma and leukemia xenograft models (eg, OCI-Ly18, MINO, NALM6, KG-1, and MOLM-14). 33 In addition to venetoclax, the combinatory effect of different BCL-2 inhibitors (ie, ABT737) with CAR-T therapy was tested, and it was found that adding ABT737 to CART19 resulted in an increase in Caspase 3/7 activity in cancer cells, leading to cancer killing enhancement. 65 …”

“… 66 Moreover, although Lee et al and Kohlhapp et al demonstrated that venetoclax augmented the anticancer response of CAR-T therapy and anti-PD-1 treatment, they also found that co-culture of venetoclax with genetically non-modified T cells and CAR-T cells potently reduced their viability. 33 64 These observations strongly suggest that careful design of combination therapies and the sequence of administration are required to avoid T-cell toxicity and ensure long-term therapeutic efficacy. One possible administration strategy to avoid bystander effects on T cells is to pretreat the cancer cells with cytotoxic drugs.…”

“… 139 Our group further demonstrates that higher levels of BCL-2 expression in CAR-T cells of patients with lymphoma significantly correlate with enhanced clinical response (ie, CAR-T persistence and overall survival) of CAR-T therapy, suggesting that modulating intrinsic apoptosis in T cells is an important strategy to enhance CAR-T therapy. 33 In addition to BCL-2, there are other critical anti-apoptotic regulators (ie, MCL-1 and BCL-xL) affecting T-cell survival and differentiation. Studies using transgenic expression of these anti-apoptotic regulators have suggested their potential implications in T cell-based immunotherapy.…”

Hypoxia drives CD39-dependent suppressor function in exhausted T cells to limit antitumor immunity

“…This triad likely evolved to prevent immunopathology in inflamed and damaged tissues, promoting immune tolerance, but only to newly activated, CD73 hi T cells; however, in the deregulated TME, this drives immune dysfunction and immunotherapy resistance. While tT ex cells have been characterized by high cell turnover via apoptosis 2,20 , several groups have reported that maintenance of T cell viability through overexpression of BCL-2 not only augments antitumor responses, but also lessens immune tolerance in the TME 40,41 . Indeed, enforced expression of BCL-2 in chimeric antigen receptor T cells improved persistence and response in both preclinical models and in human trials.…”