Combinatorial Optimization of Chemotherapeutic Agents on T-Cell Acute Lymphoblastic Leukemia

Introduction: Up to now, treatment options for T-cell acute lymphoblastic leukemia (T-ALL) remain quite limited. This study aims to assess the efficacy of monotherapies and combination of chemotherapeutic agents for T-ALL. Jurkat, CCRF-CEM are late T-cell progenitor (LTP) cell lines, while Loucy is early T-cell progenitor (ETP) cell line characterized by an immature phenotype. The drugs under evaluation include venetoclax, a selective BCL-2 inhibitor; cytarabine, a cytosine analog with established antineoplastic activity; bendamustine, an alkylating agent; and azacitidine, a DNA methyltransferase inhibitor. Given the notable tumor heterogeneity observed in T-ALL, the comprehensive assessment of these therapeutic agents on Jurkat, CCRF-CEM, and Loucy may render valuable insights for treatment strategies in T-ALL.

Methods: Cell lines were cultured in RPMI-1640 medium supplemented with 10% FBS and 1% penicillin-streptomycin at 37°C with 5% CO2. Venetoclax, bendamustine, and azacitidine were prepared as stock solutions in DMSO, while cytarabine was prepared in distilled water. Monotherapies (venetoclax, cytarabine, bendamustine and azacitidine) and combination therapies (venetoclax plus cytarabine, venetoclax plus bendamustine and venetoclax plus azacitidine) were administered. A control group received DMSO or distilled water only. Cell viability was assessed after 48 hours by using Trypan blue and colorimetric method (MTS assay) on cells treated with various drug concentrations. Statistical analysis was conducted using the SynergyFinder Plus and drc R package, with significance set at p < 0.05.

Results: Our study demonstrated that T-ALL cell lines displayed a different pattern of drug sensitivities according to combination of chemotherapeutic agents. Loucy showed greater sensitivity to venetoclax while Jurkat and CCRF-CEM exhibited higher sensitivity to cytarabine, bendamustine, and azacitidine. When conducting drug combinations on Jurkat and CCRF-CEM, the addition of venetoclax to cytarabine, bendamustine, or azacitidine resulted in an additive effect, with Loewe synergic scores ranging from -10 to 10 for each combination. On the other hand, Loucy demonstrated a distinct pattern of response; the combination of venetoclax with cytarabine showed additivity (Loewe synergic score: 8.45 and 5.82 with MTS and trypan blue assays, respectively), while venetoclax combined with bendamustine or azacitidine showed a synergistic effect (Loewe synergic score > 10 with MTS assay). Notably, among these combination treatments on Loucy, the pairing of venetoclax with bendamustine showed the most significant synergistic effects, with a Loewe score of 16.6.

Conclusion: Venetoclax-based chemotherapeutic combinations exhibited various responses in T-ALL cell lines. Of note, the combination of venetoclax plus bendamustine showed potent synergistic effects in all T-ALL cell lines. These findings warrant further study to develop fundamentally curative therapeutic strategies in T-ALL.