BACKGROUND:

The gemcitabine-insensitivity remains the main challenge for pancreatic cancer treatment.Thymoquinone, the predominant bioactive ingredient of Nigella sativa, has been shown to possess promising anti-cancer and chemo-sensitizing effects on pancreatic cancer, however, its meticulous mechanism is still indistinct.

AIM:RESULTS:

Thymoquinone pretreatment following gemcitabine treatment synergistically caused an increase inpancreatic cancer cells apoptosis and tumor growth inhibition both in vitro and in vivo. The novel combinational regimen also contributes to alterations of multiple molecular signaling targets, such as the suppression of Notch1, NICD accompanying with up-regulation of PTEN, the inactivation of Akt/mTOR/S6 signaling pathways, and the suppression of phosphorylation and nuclear translocation of p65 induced by TNF-α. Thymoquinonepretreatment and gemcitabine also induced down-regulation of anti-apoptotic Bcl-2, Bcl-xL, XIAP and up-regulation and activation of pro-apoptotic molecules including Caspase-3, Caspase-9, Bax and increased release of cytochrome c.

CONCLUSIONS:

This novel modality of thymoquinone pretreatment can enhance the anti-cancer activity of gemcitabine and may be a promising option in the treatment of pancreatic cancer.

Gemcitabine, an effective agent in treatment of cancer of pancreas, has undergone failures in many instances after multiple cycles of therapy due to emergence of drug resistance. Combination of dietary compounds with clinically validated drugs has emerged as an effective therapeutic approach to treat pancreatic tumors, refractory to gemcitabine therapy. In order to optimize a possible synergistic combination of Gemcitabine (GCB) with dietary molecules, Betuilnic acid (BA) and Thymoquinone (TQ), stand-alone IC50 dose of GCB, BA and TQ was calculated for pancreatic cancer cell lines. Fixed IC50 dose ratio of the dietary molecules in combination with reduced IC50 dose of GCB was tested on GCB resistant PANC-1 and sensitive MIA PaCa-2 cells for synergism, additive response and antagonism, using calcusyn. Combination index (CI) revealed that pre-treatment of BA and TQ along with GCB synergistically inhibited the cancer cell proliferation in in-vitro experiments. Pyruvate kinase (PK) M2 isoform, a promising target involved in cancer cell metabolism, showed down-regulation in presence of TQ or BA in combination with GCB. GCB with BA acted preferentially on tumor mitochondria and triggered mitochondrial permeability transition. Pre-exposure of the cell lines, MIA PaCa-2 and PANC-1, to TQ in combination with GCB induced apoptosis. Thus, the effectiveness of BA or TQ in combination with GCB to inhibit cell proliferation, induce apoptosis and down-regulate the expression of PKM2, reflects promise in pancreatic cancer treatment

Thymoquinone (TQ), isolated from the seeds of Nigella sativa, show moderate efficacy against pancreatic cancer. In the present work we report synthesis and characterization of novel TQ analogs appended with gallate and fluorogallate pharmacophores and evaluation of their effects against pancreatic cancer cell lines for cell viability and induction of apoptosis. The efficacy of the analogs alone or in combination with Gemcitabine was assessed in vitro. LC-MS spectra of ATQTHB and ATQTFB showed major peaks corresponding to expected M+1 fragment at 316.34 and 322.34 respectively. Molecular docking studies revealed good fit for these analogs in the COX-2 protein cavity with better binding energies compared to parent TQ compound. Present TQ analogs exhibit superior anti-proliferative activity, excellent chemo-sensitizing activity against pancreatic cancer in vitro and in combination with Gemcitabine.

OBJECTIVE:

To explore the anti-neoplastic and anti-metastatic effects of thymoquinone on the model of human pancreatic carcinoma established by surgical orthotopic implantation (SOI) in nude mice.

RESULTS:

The tumor growth-inhibiting rates of L-TQ group, H-TQ group and GEM group were 42.57%, 64.11% and 54.77% respectively. The rates of metastasis in L-TQ group and H-TQ group were 60% and 50% versus GEM group (100%). And the differences had statistical significance (P < 0.05). The positive rates of Ki-67 in group L-TQ and group H-TQ were 37% ± 3% and 32% ± 2% versus group GEM (55% ± 4%). And the differences had statistical significance (P < 0.05). The positive rates of XIAP in group L-TQ and group H-TQ were 30% ± 3% and 28% ± 5% versus group GEM (56% ± 4%). And the differences had statistical significance (P < 0.05). The positive rates of MMP-9 in group L-TQ and group H-TQ were 57% ± 7% and 53% ± 2% versus group GEM (73% ± 4%). And the differences had statistical significance (P < 0.05).

CONCLUSION:

Thymoquinone has the anti-neoplastic and anti-metastatic effects on the human pancreaticcarcinoma in nude mice. And the above effects may be correlated with the down-regulated expressions of XIAP and MMP-9.

Recent studies reported that thymoquinone (TQ), a component derived from the medicinal spice Nigella sativa (also called black cumin), exhibited inhibitory effects on cell proliferation of many cancer cell lines. This study was performed to investigate the anti-metastatic effect of thymoquinone on the pancreatic cancer in vitro and in vivo. The results showed that thymoquinone suppressed the migration and invasion of Panc-1 cells in a does-dependent manner. To investigate the possible mechanisms involved in these events, Western blotting analysis was performed, and found that thymoquinone significantly down-regulates NF-kappaB and MMP-9 in Panc-1 cells. In addition, metastatic model simulating human pancreatic cancer was established by orthotropic implantation of histologically intact pancreatic tumor tissue into the pancreatic wall of nude mice. And administration of thymoquinone significantly reduced tumor metastasis compared to untreated control. Furthermore, the expression of NF-kappaB and MMP-9 in tumor tissues was also suppressed after treatment with thymoquinone. Taken together, the results indicate that thymoquinone exerts anti-metastatic activity onpancreatic cancer both in vitro and in vivo, which may be related to down-regulation of NF-kappaB and its regulated molecules such as MMP-9 protein. Consequently, these results provide important insights intothymoquinone as an antimetastatic agent for the treatment of human pancreatic cancer.

Thymoquinone is an active ingredient isolated from Nigella sativa and has been investigated for its anti-oxidant, anti-inflammatory and anticancer activities in both in vitro and in vivo models since its first extraction in 1960s. Its anti-oxidant/anti-inflammatory effect has been reported in various disease models, including encephalomyelitis, diabetes, asthma and carcinogenesis. Moreover, thymoquinone could act as a free radical and superoxide radical scavenger, as well as preserving the activity of various anti-oxidant enzymes such as catalase, glutathione peroxidase and glutathione-S-transferase. The anticancer effect(s) of thymoquinone are mediated through different modes of action, including anti-proliferation, apoptosis induction, cell cycle arrest, ROS generation and anti-metastasis/anti-angiogenesis. In addition, this quinone was found to exhibit anticancer activity through the modulation of multiple molecular targets, including p53, p73, PTEN, STAT3, PPAR-γ, activation of caspases and generation of ROS. The anti-tumor effects of thymoquinone have also been investigated in tumor xenograft mice models for colon, prostate, pancreatic and lung cancer. The combination of thymoquinone and conventional chemotherapeutic drugs could produce greater therapeutic effect as well as reduce the toxicity of the latter. In this review, we summarize the anti-oxidant/anti-inflammatory and anticancer effects of thymoquinone with a focus on its molecular targets, and its possible role in the treatment of inflammatory diseases and cancer.

Pancreatic cancer is one of the most lethal cancers in the world, as it continues to be resistant to any therapeutic approaches. The high molecular weight glycoprotein mucin 4 (MUC4) is aberrantly expressed in pancreatic cancer and contributes to the regulation of differentiation, proliferation, metastasis, and the chemoresistance of pancreatic cancer cells. The absence of its expression in the normal pancreatic ductal cells makes MUC4 a promising target for novel cancer therapeutics. Natural products have been widely investigated as potential candidates in cancer therapies, and thymoquinone (TQ), extracted from the seeds of Nigella sativa, has shown excellent antineoplastic properties in some systems. In the present study, we evaluated the effect of TQ on pancreatic cancer cells and specifically investigated its effect on MUC4 expression. The MUC4-expressing pancreatic cancer cells FG/COLO357 and CD18/HPAF were incubated with TQ, and in vitro functional assays were done. The results obtained indicate that treatment with TQ downregulated MUC4 expression through the proteasomal pathway and induced apoptosis in pancreatic cancer cells by the activation of c-Jun NH(2)-terminal kinase and p38 mitogen-activated protein kinase pathways. In agreement with previous studies, the decrease in MUC4 expression correlated with an increase in apoptosis, decreased motility, and decreased migration of pancreatic cancer cells. MUC4 transient silencing studies showed that c-Jun NH(2)-terminal kinase and p38 mitogen-activated protein kinase pathways are activated in pancreatic cancer cells, indicating that the activation of these pathways by TQ is directly related to the MUC4 downregulation induced by the drug. Overall, TQ has potential for the development of novel therapies against pancreatic cancer.

BACKGROUND:

Both hereditary and sporadic forms of chronic pancreatitis are associated with an increased risk of developing pancreatic ductal adenocarcinoma (PDA). Inflammation has been identified as a significant factor in the development of solid tumour malignancies. We have recently shown that thymoquinone (Tq), the major constituent of Nigella sativa oil extract, induced apoptosis and inhibited proliferation in PDA cells. Tq also increased p21 WAF1 expression, inhibited histone deacetylase (HDAC) activity, and induced histone hyperacetylation. HDAC inhibitors have been shown to ameliorate inflammation-associated cancer. In this study, we evaluated the anti-inflammatory potential of Tq in PDA cells in comparison with that of a specific HDAC inhibitor, trichostatin A (TSA).

METHODS:

PDA cells were treated with or without Tq (25-75 microM), with or without pre-treatment of tumour necrosis factor (TNF)-alpha (25 ng/ml). The effect of Tq on the expression of different proinflammatory cytokines and chemokines was analysed by real-time polymerase chain reaction (PCR). Luciferase-labelled promoter studies evaluated the effect of Tq on the transcription of monocyte chemoattractant protein-1 (MCP-1) and nuclear factor-kappaB (NF-kappaB). The effect of Tq on the constitutive and TNF-alpha-induced activation and nuclear translocation of NF-kappaB was examined by ELISA and immunohistochemistry.

RESULTS:

Tq dose- and time-dependently significantly reduced PDA cell synthesis of MCP-1, TNF-alpha, interleukin (IL)-1beta and Cox-2. At 24 h, Tq almost completely abolished the expression of these cytokines, whereas TSA had a less dramatic effect. Tq, but not TSA, significantly and dose-dependently reduced the intrinsic activity of the MCP-1 promoter. Tq also inhibited the constitutive and TNF-alpha-mediated activation of NF-kappaB in PDA cells and reduced the transport of NF-kappaB from the cytosol to the nucleus.

CONCLUSIONS:

Our data demonstrate previously undescribed anti-inflammatory activities of Tq in PDA cells, which are paralleled by inhibition of NF-kappaB. Tq as a novel inhibitor of proinflammatory pathways provides a promising strategy that combines anti-inflammatory and proapoptotic modes of action.

Previous studies have shown biological activity of thymoquinone, an active compound extracted from Nigella sativa, in pancreatic cancer cells; however, preclinical animal studies are lacking. Here, we report, for the first time, the chemosensitizing effect of thymoquinone to conventional chemotherapeutic agents both in vitro and in vivo using an orthotopic model of pancreatic cancer. In vitro studies revealed that preexposure of cells withthymoquinone (25 mumol/L) for 48 h followed by gemcitabine or oxaliplatin resulted in 60% to 80% growth inhibition compared with 15% to 25% when gemcitabine or oxaliplatin was used alone. Moreover, we found that thymoquinone could potentiate the killing of pancreatic cancer cells induced by chemotherapeutic agents by down-regulation of nuclear factor-kappaB (NF-kappaB), Bcl-2 family, and NF-kappaB-dependent antiapoptotic genes (X-linked inhibitors of apoptosis, survivin, and cyclooxygenase-2). As shown previously by our laboratory, NF-kappaB gets activated on exposure of pancreatic cancer cells to conventional chemotherapeutic agents; interestingly, thymoquinone was able to down-regulate NF-kappaB in vitro, resulting in chemosensitization. In addition to in vitro results, here we show for the first time, that thymoquinone in combination with gemcitabine and/or oxaliplatin is much more effective as an antitumor agent compared with either agent alone. Most importantly, our data also showed that a specific target, such as NF-kappaB, was inactivated in animal tumors pretreated with thymoquinone followed by gemcitabine and/or oxaliplatin. These results provide strong in vivo molecular evidence in support of our hypothesis that thymoquinone could abrogate gemcitabine- or oxaliplatin-induced activation of NF-kappaB, resulting in the chemosensitization ofpancreatic tumors to conventional therapeutics.

The limited ability of current treatments for pancreatic cancer prompted us to examine the effects of antioxidants on proliferation of pancreatic cancer cells. Antioxidants have been reported to possess antioxidant activity in vitro. The specific aim of this study was to investigate the role of epigallocatechin gallate (EGCG), a major component of green tea and thymoquinone on the proliferation and viability of PANC-1 cell line using a standard method of treatment. The PANC-1 cells were treated with three predetermined doses ofthymoquinone and EGCG (5, 25, and 50 ug/dL) for 24, 48, and 72 hours in culture medium. Determination of viability and morphology was examined microscopically after each 24 hour interval. Data collected from this study indicated a dose dependent relationship with direct administration of EGCG alone or in combination withthymoquinone. However, a rebound effect was observed after 48 and 72 hours during direct administration of both antioxidants. These results indicate that direct administration of EGCG alone or in combination withthymoquinone can limit PANC-1 cell proliferation (p < 0.05). EGCG and thymoquinone may be a potent biologic inhibitor of human pancreatic carcinomas, reducing their propagation activities.

The separate effects of alpha-hederin and thymoquinone, the two principal bioactive constituents of Nigella sativa, on four human cancer cell lines [A549 (lung carcinoma), HEp-2 (larynx epidermoid carcinoma), HT-29 (colon adenocarcinoma) and MIA PaCa-2 (pancreas carcinoma)] were investigated. Alpha-hederin was also examined as a pro-drug. Each assessment quantified both cytotoxic and apoptotic/necrotic effects. Alpha-hederin and thymoquinone separately induced a dose- and time-dependent effect on the cell lines tested. HEp-2 cells were the most sensitive, exhibiting apoptosis with a higher incidence following thymoquinonetreatment. Pre-treatment of cells with alpha-hederin, followed by thymoquinone or cisplatin, did not enhance the cytotoxicity or apoptosis induced by either drug. So, the membrane-perforating properties associated with saponins, here represented by alpha-hederin, enhance neither cytotoxicity nor apoptosis of these cancer cells.

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.