Synergistic Effect of Quinacrine with Chemotherapeutics or TRAIL in Hematopoietic Malignant Cells

Quinacrine is a bioactive acridine derivative which has been used for treatment of malaria, giardiasis, systemic lupus erythematosus, and rheumatoid arthritis. In searching for p53 pathway activating agents for cancer therapy, we found that quinacrine stabilizes p53 and induces p53-dependent and p53-independent tumor cell death. Quinacrine also induces expression of TRAIL Death Receptor 5 (DR5) and reduces expression of anti-apoptotic Mcl-1 in tumor cells. These activities predict synergies with TRAIL (tumor necrosis factor-related apoptosis inducing ligand) and chemotherapeutic agents in inducing extrinsic and intrinsic pathway mediated apoptosis. In addition, quinacrine suppresses NFkB activity in tumor cells. Clinical trials have been ongoing for treatment of solid tumors including colon cancer, renal cancer, prostate cancer, and non-small cell lung cancer with quinacrine in combination with chemotherapy or tyrosine-kinase inhibitors, however, the therapeutic potential of quinacrine in blood cancer cells has not been established. We tested quinacrine on hematopoietic malignant cells, which included cell lines of myeloid leukemia, lymphoblastic leukemia, B-cell lymphoma, T-cell lymphoma, and multiple myeloma. We found that quinacrine induces massive cell death in the cell lines tested, at concentrations from as less as 1 microM to 5 microM, 2-10 times lower than required to induce solid tumor cell death. Quinacrine synergizes with TRAIL in inducing cell death of TRAIL-sensitive cells and reverses resistance in TRAIL-resistant cells. Quinacrine also synergizes with chemotherapeutic agents, such as antimetabolites, alkylating agents, and tyrosine kinase inhibitors, in inducing apoptosis of hematopoietic cancer cell lines. Our work supports translational efforts to advance the use of quinacrine from bench to clinic and provides rationale for combination chemotherapeutic regimes for treatment of hematopoietic malignancies.