Anticancer effects of thymoquinone on prostate cancer cells and natural killer cell activity

Dark cumin, or Nigella sativa, is a well‑known and popular herbal medicine that may be used in the treatment of gastrointestinal issues, diabetes, bronchitis, high blood pressure and cancer. The anticancer action of Nigella sativa may be associated with the immune‑modulatory effect of its activation of human natural killer (NK) cells. NK cells, a subset of lymphocytes, are a component of innate immunity, the body's initial line of defense against infections. To identify potential ways to improve immunotherapy using natural products, the present study aimed to assess the impact of thymoquinone (TQ), a key component of Nigella sativa, on the activity of NK cells through their cytotoxicity and released chemicals. CD56 NK cells that were isolated and positively selected from blood samples, were cultured with PC3‑RFP prostate cancer cells and treated with TQ at different concentrations (25 and 50 µM). Cytotoxicity was measured, and perforin, granzyme B and interferon‑α (IFN‑α) levels were assessed using ELISA. The results demonstrated that the cytotoxic effect of NK cells on PC3‑RFP was significantly increased in the presence of TQ from 55.1 to 85.35%. Furthermore, with 50 µM TQ, there was a significant increase in secretion of perforin (0.80 ng/ml) compared with the control (0.2 ng/ml), and of granzyme B (1.24 ng/ml) compared with the control (0.65 ng/ml). Moreover, the production of IFN‑α by the NK cells significantly increased in the presence of 25 and 50 µM TQ (0.5 and 0.7 ng/ml, respectively) compared with the control (0.3 ng/ml). In summary, TQ increased NK cell cytotoxicity against PC3‑RFP cells, indicating a potential application in the development of cell‑based immunity treatment that requires more research and has promising prospects.