Xiao-Ling Ding

Enhancing antitumor effects in pancreatic cancer cells by combined use of COX-2 and 5-LOX inhibitors.

Cyclooxygenase (COX)-2 and lipoxygenase (LOX)-5 are involved in carcinogenesis of pancreatic cancer. COX-2 inhibitor celecoxib displays inhibitory effects in pancreatic cancer cell growth. Recently, it has been reported that COX-2 inhibitor may not be able to suppress pancreatic tumor growth in vivo and its application is further limited by untoward side effects. The present study provides evidence that combined use of celecoxib and 5-LOX inhibitor MK886 markedly suppresses pancreatic tumor cell growth in vitro. Compared to the single inhibitor treatment, dual treatment with celecoxib and MK886 exerted additive antitumor effects in pancreatic tumor cells. We found that MK886 reversed celecoxib-induced increases in 5-LOX gene expression and Erk1/2 activation in pancreatic tumor cells. Moreover, Dual treatment of pancreatic tumor cells with celecoxib and MK886 inhibited the levels of LBT4 receptor BLT1 and vascular endothelial growth factor. Our results imply that combined use of celecoxib and MK886 might be an effective way to treat clinical patients with pancreatic cancer.

Triptolide suppresses proliferation, hypoxia-inducible factor-1α and c-Myc expression in pancreatic cancer cells.

Triptolide (TL) is known to suppress the proliferation of a number of pancreatic cancer cell lines in vitro. Marked antitumor effects were also observed in a xenograft model of pancreatic cancer. Hypoxia‑inducible factor‑1α (HIF‑1α) is highly expressed in pancreatic cancer cells lines. The present study therefore tested the hypothesis that suppression of HIF‑1α is associated with the antitumor activity of TL. Quantitative polymerase chain reaction and western blot analysis were used to determine the level of gene expression. A xenograft tumor model of pancreatic cancer was established in athymic nude mice and the tumor size was measured to evaluate the outcome of TL treatment. Immunohistochemistry was used to detect the expression of HIF‑1α and vascular endothelial growth factor (VEGF), and to assess microvessel density. Microarray was used to investigate gene expression in pancreatic cancer cells following TL treatment. The expression of HIF‑1α was shown to be reduced in pancreatic cell lines following treatment with TL, and this effect occurred in a dose‑dependent manner. In a xenograft model of pancreatic cancer, reduced levels of HIF‑1α were also observed in mice that were treated with TL. Furthermore, the expression of VEGF, which is a direct target of HIF‑1α, was also suppressed, and the microvessel density of tumor tissues was consequently reduced. A microarray analysis of gene expression was performed in order to investigate the potential mechanisms underlying the antitumor activity of TL. The results showed that 11 genes, including c‑Myc, SOX9 and Ets2, were downregulated at an early stage following treatment with TL. A recent study indicated that overexpression of c‑Myc in colon cancer cells promotes increased expression of HIF‑1α and VEGF. Therefore, TL may suppress HIF‑1α through a c‑Myc‑dependent mechanism, which is involved in antitumor effects in mouse models of pancreatic cancer.

Inhibition of 5-lipoxygenase triggers apoptosis in pancreatic cancer cells

The 5-lipoxygenase (5-LOX) pathway has been associated with a variety of inflammatory diseases including asthma, atherosclerosis, rheumatoid arthritis, cancer and liver fibrosis. Several classes of 5-LOX inhibitors have been identified, but only one drug, zileuton, a redox inhibitor of 5-LOX, has been approved for clinical use. In the present study, 5-LOX was found to be overexpressed not only in pancreatic cancer cell lines but also in tissue samples of patients suffering from pancreatic adenocarcinoma. There was a close correlation between the tumor expression levels of 5-LOX mRNA and protein and the clinicopathological patient characteristics including lymph node metastasis and TNM stage. Zileuton suppressed the proliferation of SW1990 cells in a concentration- and time‑dependent manner. In addition, zileuton induced SW1990 cells to undergo apoptosis and significantly decreased 5-LOX expression. The number of apoptotic cells, estimated by flow cytometry, Annexin V/PI assay, TUNEL staining and sub‑diploid population was significantly higher than that of the control. These results suggest that the level of 5-LOX expression was increased in pancreatic cancer tissues and may be related to lymph node metastasis and TNM stage.

β2-adrenergic receptor signaling promotes pancreatic ductal adenocarcinoma (PDAC) progression through facilitating PCBP2-dependent c-myc expression.

The β2-adrenergic receptor (β2-AR) plays a crucial role in pancreatic ductal adenocarcinoma (PDAC) progression. In this report, we identified poly(rC)-binding protein 2 (PCBP2) as a novel binding partner for β2-AR using immunoprecipitation-mass spectrometry (IP-MS) approach. The association between β2-AR and PCBP2 was verified using reciprocal immunoprecipitation. Importantly, we found significant interaction and co-localization of the two proteins in the presence of β2-AR agonist in Panc-1 and Bxpc3 PDAC cells. β2-AR-induced recruitment of PCBP2 led to augmented protein level of c-myc in PDAC cells, likely as a result of enhanced internal ribosome entry segment (IRES)-mediated translation of c-myc. The activation of β2-AR accelerated cell proliferation and colony formation, while knockdown of PCBP2 or c-myc restrained the effect. Furthermore, overexpression of PCBP2 was observed in human PDAC cell lines and tissue specimens compared to the normal pancreatic ductal epithelial cells and the non-cancerous tissues respectively. Overexpression of β2-AR and PCBP2 was associated with advanced tumor stage and significantly worsened prognosis in patients with PDAC. Our results elucidate a new molecular mechanism by which β2-AR signaling facilitates PDAC progression through triggering PCBP2-dependent c-myc expression.

Triptolide augments the effects of 5-lipoxygenase RNA interference in suppressing pancreatic tumor growth in a xenograft mouse model

PurposePancreatic cancer has one of the highest fatality rates of all cancers, and new strategies or reagents to tackle this disease are needed. Triptolide (TL) is able to potently inhibit the growth of pancreatic tumor cells in vitro. On the other hand, blockage of 5-LOX pathway might be useful for treatment of pancreatic cancer. In the current study, we tested the effects of 5-LOX RNA interference and TL individually or in combination in suppressing human pancreatic tumor growth in xenograft mouse model.Methods5-LOX short hairpin RNA (shRNA) vectors were developed and screened out for their efficacy in human pancreatic cancer cell line SW1990 in vitro. Their antitumor effects were also evaluated by measuring cell proliferation and apoptosis. An effective 5-LOX shRNA was given alone or in combination with TL to treat pancreatic tumor xenograft. Expression levels of 5-LOX and VEGF were measured with Western blotting and immunohistology.ResultsKnocking down 5-LOX gene suppressed cancer cell growth in vitro and intra-tumoral delivering of 5-LOX shRNA inhibited growth of transplanted tumor in vivo. TL treatment induced tumor suppression and greatly enhanced antitumor effects of 5-LOX shRNA in the mouse model. 5-LOX RNA interference or TL treatment suppresses VEGF expression in tumor tissue, and combined treatment further reduces its expression.ConclusionsBoth treatments exerted antitumor effects in vivo, and combined use of the two approaches produced more powerful antitumor effects. Synergistic effects of combined treatment in VEGF expression may contribute to the mechanisms of the strong antitumor effects.

Therapeutic effects of triptolide via the inhibition of IL-1β expression in a mouse model of ulcerative colitis

The present study aimed to investigate the effect of triptolide (TL) on ulcerative colitis (UC) and explore the potential association between the therapeutic effects of TL and IL-1β expression using a 4,4-dimethyl-4-silapentane-1-sulfonic acid (DSS)-induced mouse model to simulate human UC. A total of 70 BALB/c female mice were randomly allocated into seven equal groups: Group A, blank control; group B, normal saline injection; group C, propylene glycol injection; group D (TL1), 0.2 mg/kg TL; group E (TL2), 0.4 mg/kg TL; group F (TL3), 0.6 mg/kg TL; and group G, dexamethasone injection. Mice activity, diet and stool characteristics were recorded daily. Mice were sacrificed by cervical dislocation on day 8, and disease activity indices, colon tissue histological scores and colonic histopathological scores were subsequently calculated. Serum levels of IL-1β were evaluated by enzyme-linked immunosorbent assay, and IL-1β expression levels were examined by reverse transcription-quantitative polymerase chain reaction with colonic mucosa specimen at the gene level and western blot analysis at the protein level. The IL-1β mRNA and protein expression levels were significantly elevated in the normal saline injection and propylene glycol injection groups compared with the blank control group and (P<0.01). In TL (TL2 and TL3)- and dexamethasone-treated mice, IL-1β expression levels were significantly decreased, as compared with the normal saline and propylene glycol injection groups (P<0.05). No significant difference was detected between TL (TL2 and TL3) and dexamethasone treatments. The results of the present study indicated that IL-1β expression was upregulated in the UC mouse model, which may be associated with the development and progression of UC. Furthermore, TL inhibited IL-1β expression, suggesting that TL may be a novel therapeutic target for the treatment of UC.

Expression of chemokine CCL20 in ulcerative colitis

The aim of the current study was to investigate the expression of chemokine CCL20 in ulcerative colitis (UC) patients and in dextran sulfate sodium (DSS)-induced experimental colitis in mice. The expression of the CCL20 protein in colonic mucosa was detected in 65 UC patients and in 30 normal patients. A total of 40 female BALB/c mice were divided into a control and model group; the latter was fed a 5% DSS solution ad libitum for 7 days to induce experimental colitis. The disease activity index (DAI) and histological score were assessed and the expression of CCL20 mRNA and protein was determined. CCL20 was expressed in the UC group. It was either weakly expressed or not expressed in the normal control group. Additionally, the expression of CCL20 in the UC group was significantly higher compared with that in the control groups (P<0.01). The expression levels of CCL20 mRNA and protein were significantly increased in the model group compared with those in the control group (P<0.01) and positively correlated with the severity of colonic inflammation. The results from the present study demonsrtate that CCL20 positively correlates with UC. CCL20 may play a significant role in local damage and pathological changes in UC and may serve as a potential target for therapy.