Abstract
Thymoquinone (TQ) and piperine, the active ingredients in cumin (Nigella sativa) and black pepper (Piper longum), respectively, exhibit various bioactivities including anticancer effects. The aim of the present study is to investigate the antineoplastic activity of a combination of TQ and piperine against breast cancer implanted in mice. The antiproliferative effects of TQ, piperine, and a combination of both agents were tested against mouse epithelial breast cancer cell line (EMT6/P) using MTT assay. The isobolographic method was used to calculate the combination index (CI). Degree of angiogenesis inhibition was detected by measuring vascular endothelial growth factor (VEGF) levels in tissue culture for all treatments. EMT6/P cells were inoculated in Balb/C mice and the antitumor effect of TQ, piperine, and their combination was assessed. Changes in tumor size were calculated for all treatments. Tumor histology was examined using the hematoxylin/eosin staining protocol. Terminal deoxynucleotidyl transferase (TdT) dUTP Nick-End Labeling (TUNEL) colorimetric assay and caspase-3 activity assays were used to detect apoptosis. Serum levels of interferon (INF)-γ, interleukin (IL)-4, IL-2, and IL-10 were measured using ELISA and treatment toxicity was evaluated by measuring serum levels of aspartate transaminase (AST), alanine transaminase (ALT), and creatinine. A clear synergistic antiproliferative interaction between TQ and piperine was observed with CI value of 0.788. The combination therapy resulted in significant reduction in tumor size with percentage cure of 60% and percentage death of 0%. High degrees of apoptosis and geographical necrosis were induced in tumors treated with the combination therapy. Combination therapy caused significant decrease in VEGF expression and increased serum INF-γ levels. Normal serum levels of AST, ALT, and creatinine were observed in tumor-bearing mice treated with the combination therapy. The combination of TQ and piperine acts synergistically to target breast cancer in vitro and in vivo. This novel combination exerts its effect by angiogenesis inhibition, apoptosis induction, and shifting the immune response toward T helper1 response. This combination therapy deserves further investigation (including measurement of hypoxia-inducible factor (HIF)1α to be used in clinical studies.