JAK inhibition synergistically potentiates BCL2, BET, HDAC, and proteasome inhibition in advanced CTCL

Abstract

Cutaneous T-cell lymphoma (CTCL) is a malignancy of skin-homing T lymphocytes that is more likely to involve the peripheral blood in advanced stages. For such patients with advanced disease, there are few available systemic treatment options, and prognosis remains poor. Exome sequencing studies of CTCL have suggested therapeutic targets, including within the JAK/STAT pathway, but JAK inhibition strategies may be limited by patient-specific mutational status. Because our recent research has highlighted the potential roles of single and combination approaches specifically using BCL2, bromodomain and extra-terminal domain (BET), and histone deacetylase (HDAC) inhibition, we aimed to investigate the effects of JAK inhibition on CTCL cells and established CTCL cell lines when paired with these and other targeting agents. Peripheral blood malignant CTCL isolates exhibited differential responses to JAK inhibition, with JAK2 expression levels negatively correlating to 50% inhibitory concentration (IC50) values. Regardless of single-agent sensitivity, JAK inhibition potentiated malignant cell cytotoxicity in combination with BCL2, BET, HDAC, or proteasome inhibition. Combination inhibition of JAK and BCL2 showed the strongest potentiation of CTCL cytotoxicity, driven by both intrinsic and extrinsic apoptosis pathways. JAK inhibition decreased expression of BCL2 in the high-responder samples, suggesting a putative mechanism for this combination activity. These results indicate that JAK inhibition may have major effects on CTCL cells, and that combination strategies using JAK inhibition may allow for more generalized cytotoxic effects against the malignant cells from patients with CTCL. Such preclinical assessments help inform prioritization for combination targeted drug approaches for clinical utilization in the treatment of CTCL.

B-cell lymphoma 2 inhibitor venetoclax treatment of a patient with cutaneous T-cell lymphoma

“…Responders to venetoclax monotherapy for chronic lymphocytic leukemia had progression-free survival of approximately 70% at 12 to 15 months. 7 , 9 , 10 Evidence of clinical efficacy in our patient, supported by our previously reported in vitro viability assays and CTCL patient malignant cell BCL-2 expression profiles, 4 , 5 suggests venetoclax as a potential oral therapy for CTCL that warrants further investigation of clinical safety, dosing, and efficacy.…”

“… 3 We also recently reported that patient-derived CTCL cells exhibited variable sensitivity to venetoclax, with a portion showing picomolar-range 50% inhibitory concentrations, and that venetoclax sensitivity was correlated with baseline BCL-2 expression. 4 , 5 Herein, we present a CTCL patient with skin and blood involvement treated with daily venetoclax.…”

Research Techniques Made Simple: Preclinical Development of Combination Antitumor Targeted Therapies in Dermatology

“…Established tumor cell lines may be passaged in vitro, frozen and stored for later use, and transplanted into syngeneic and/or immunecompromised laboratory animals to grow as tumors. Limitations to the use of passaged tumor cell lines include the potential for further development and selection of mutations in vitro, and that limited lines may not reflect the heterogeneity of disease in patients (Gillet et al, 2013;Yumeen et al, 2020). Alternatively, primary tumor cell isolates from patients may be short-term cultured, and their genomic and transcriptional profiles are likely a more accurate representation of the spectrum of disease.…”

“…Chromatin organization can be altered in malignant cells to result in an aberrant transcriptional profile, and thus DNA methylation or histone deacetylation can also be targeted. (Created with biorender.com and adapted with permission from Yumeen et al, 2020). GPCR, G-protein coupled receptor; HDAC, histone deacetylase; SMI, small molecule inhibitor; STAT, signal transducer and activator of transcription; TRAIL, TNF-related apoptosis-inducing ligand.…”

“…Such combinations nonetheless would still necessitate major evaluation and validation clinically. We have recently utilized these methods for preclinical development of combination therapies for CTCL in vitro (Mirza et al, 2020;Yumeen et al, 2020). We found that the combination of Jak inhibition and BCL2 inhibition shows synergistic activity in vitro and that combinations of natural and over-the-counter compounds, including gentian violet and salinomycin, may be effective in synergistic combinations (Mirza et al, 2020;Yumeen et al, 2020).…”