N. Sativa L., an oriental spice, has long been used as a natural medicine for treatment of many acute as well as chronic conditions. It has been used in the treatment of diabetes, hypertension, and dermatological conditions. There has been very few studies on the effects of N. Sativa as cancer prevention/therapy. Our objective therefore, was to expose MCF-7 breast cancer cells to aqueous and alcohol extracts and in combination with H2O2 as an oxidative stressor. Measurement of cell survival under various concentrations and combinations was conducted using standard cell culture techniques, exposure protocols in 96 well plates and Fluoro-spectrosphotometry. Following cellular growth to 90% confluency, exposure to water (WE) and ethanol (AE) extracts of N. sativa and H2O2 was performed. Toxicity index (LC50) was calculated from percent survival using regression analysis. Results showed that the alcohol extract and its combinations were able to completely inactivate the MCF-7 cells (LC50 ranged from 377.16-573.79 in descending potency for H2O2 + AE, AE and Mix of WE and AE). H2O2 alone effectively inactivated MCF-7 cells (LC50 = 460.94). The least effective combinations in descending potency were WE + H2O2, WE + AE + H2O2, and WE (LC50 were 725.79, 765.94, and 940.5 respectively. Combinations other than AE + H2O2 showed possible interactions, which lead to reduction in their potency. In conclusion, N. Sativa alone or in combination with oxidative stress were found to be effective in vitro in inactivating MCF-7 breast cancer cells, unveiling opportunities for promising results in the field of prevention and treatment of cancer.

The potential antitumor effect of thymoquinone (TQ), the main constituent of the volatile oil of Nigella sativa seed, on fibrosarcoma induced by 20-methylcholanthrene (MC) in male Swiss albino mice was investigated in vivo and in vitro. Administration of TQ (0.01% in drinking water) I week before and after MC treatment significantly inhibited the tumor incidence and tumor burden by 43% and 34%, respectively, compared with the results in the group receiving MC alone. Moreover, TQ delayed the onset of MC-induced fibrosarcoma tumors that appeared at 12 weeks and produced less MC-induced mortality. Lipid peroxide accumulation, decreased glutathione (GSH) content, and decreased activities of glutathione S-transferase (GST) and quinone reductase (QR) were observed in the liver of MC-induced tumor-bearing mice. TQ alone showed a significant induction in the enzyme activities of hepatic GST and QR. Mice treated with TQ along with MC showed reduction in hepatic lipid peroxides and increased GSH content and increased enzyme activities of GST and QR as compared to results of the control group. The in vitro studies showed that TQ inhibited the survival of fibrosarcoma cells with IC50 of 15 microM. Conversely, TQ inhibited the incorporation of [3H] thymidine in fibrosarcoma cells with IC50 of microM. Our data indicate the potential of TQ as a powerful chemopreventive agent against MC-induced fibrosarcoma tumors. The possible modes of action of TQ may be through its antioxidant activity and interference with the DNA synthesis coupled with enhancement of detoxification processes.

A crude gum, a fixed oil and two purified components of Nigella sativa seed, thymoquinone (TQ) and dithymoquinone (DIM), were assayed in vitro for their cytotoxicity for several parental and multi-drug resistant (MDR) human tumor cell lines. Although as much as 1% w/v of the gum or oil was devoid of cytotoxicity, both TQ and DIM were cytotoxic for all of the tested cell lines (IC50’s 78 to 393 microM). Both the parental cell lines and their corresponding MDR variants, over 10-fold more resistant to the standard antineoplastic agents doxorubicin (DOX) and etoposide (ETP), as compared to their respective parental controls, were equally sensitive to TQ and DIM. The inclusion of the competitive MDR modulator quinine in the assay reversed MDR Dx-5 cell resistance to DOX and ETP by 6- to 16-fold, but had no effect on the cytotoxicity of TQ or DIM. Quinine also increased MDR Dx-5 cell accumulation of the P-glycoprotein substrate 3H-taxol in a dose-dependent manner. However, neither TQ nor DIM significantly altered cellular accumulation of 3H-taxol. The inclusion of 0.5% v/v of the radical scavenger DMSO in the assay reduced the cytotoxicity of DOX by as much as 39%, but did not affect that of TQ or DIM. These studies suggest that TQ and DIM, which are cytotoxic for several types of human tumor cells, may not be MDR substrates, and that radical generation may not be critical to their cytotoxic activity.

The active principle of Nigella sativa seeds containing certain fatty acids was studied for antitumour activities against Ehrlich ascites carcinoma (EAC), Dalton’s lymphonia ascites (DLA) and Sarcoma-180 (S-180) cells. In vitro cytotoxic studies showed 50% cytotoxicity to Ehrlich ascites carcinoma, Dalton’s lymphoma ascites and Sarcoma-180 cells at a concentration of 1.5 micrograms, 3 micrograms and 1.5 micrograms respectively with little activity against lymphocytes. The cell growth of KB cells in culture was inhibited by the active principle while K-562 cells resumed near control values on day 2 and day 3. Tritiated thymidine incorporation studies indicated the possible action of an active principle at DNA level. In vivo EAC tumour development was completely inhibited by the active principle at the dose of 2 mg/mouse per day x 10.

Topical application of Nigella sativa and Crocus sativus extracts (common food spices) inhibited two-stage initiation/promotion [dimethylbenz[a]anthracene (DMBA)/croton oil] skin carcinogenesis in mice. A dose of 100 mg/kg body wt of these extracts delayed the onset of papilloma formation and reduced the mean number of papillomas per mouse, respectively. The possibility that these extracts could inhibit the action of 20-methylcholanthrene (MCA)-induced soft tissue sarcomas was evaluated by studying the effect of these extracts on MCA-induced soft tissue sarcomas in albino mice. Intraperitoneal administration of Nigella sativa (100 mg/kg body wt) and oral administration of Crocus sativus (100 mg/kg body wt) 30 days after subcutaneous administration of MCA (745 nmol x 2 days) restricted tumor incidence to 33.3% and 10%, respectively, compared with 100% in MCA-treated controls.