Ulcerative colitis (UC) and Crohn’s disease (CD) constitute the two major groups of idiopathic disorders in inflammatory bowel disease (IBD). Environmental factors, genetic factors and immune responses have been considered as the major etiology of IBD. Despite the diversified pathogenesis of the disease, no guaranteed curative therapeutic regimen has been developed so far. This review summarizes the knowledge on the pathophysiology and current treatment approaches of IBD. Since IBD is caused by excessive and tissue- disruptive inflammatory reactions of the gut wall, down-regulation of the immune responses may allow the damaged mucosa to heal and reset the physiological functions of the gut back to normal. Current pharmacotherapy through modulation of neutrophil-derived factors, cytokines, adhesion molecules and reactive oxygen/nitrogen metabolites has been utterly described. Categories of treatment modalities include corticosteroids, aminosalicylates, immunomodulators, antibiotics, probiotics, and a series of unique novel agents. The use of anti-tumor necrosis factor monoclonal antibody (Infliximab), recombinant anti-inflammatory cytokines and related gene therapy has been covered. In addition, discussions on dietary supplementation and heparin treatment are also included. The anti-inflammatory and immunoregulatory potential of investigational agents such as nicotine and the filtered protective compounds from tobacco smoke, as well as active herbal medicinal compounds were tested in our previous experimental works, whereas promising findings have been presented here. With the discovery of novel target-oriented agents, more effective and relatively harmless approaches of IBD therapy could be established to achieve a curative outcome. Indeed, more experimental and clinical studies are needed to confirm the relevance of these therapies.

Formononetin is a novel herbal isoflavonoid isolated from Astragalus membranaceus, a medicinal plant that possesses antitumorigenic properties. Our previous findings demonstrated that formononetin initiates growth-inhibitory and pro-apoptotic activities in human colon cancer cells. In the present study, we aimed to further examine the potential of formononetin in controlling angiogenesis and tumor cell invasiveness in human colon cancer cells and tumor xenografts. The results showed that formononetin downregulated the expression of the key pro-angiogenic factors, including vascular endothelial growth factor (VEGF) and matrix metalloproteinases. We also discovered that the invasiveness of metastatic colon cancer cells was alleviated following drug treatment. The potential anti-angiogenic effect of formononetin was examined in nude mouse xenografts. The tumor size and the number of proliferating cells were reduced in the tumor tissues obtained from the formononetin-treated group. The serum VEGF level was also reduced in the drug-treated animals when compared to the controls. These findings suggest that formononetin inhibits angiogenesis and tumor cell invasion, and thus support its use in the treatment of advanced and metastatic colon cancers.

Background: Our ongoing research has revealed that total saponins extracted from the medicinal herb Radix Astragali (AST) exhibits significant growth-inhibitory and proapoptotic effects in human cancer cells. In the present study, the potential of AST in controlling angiogenesis was further investigated with elaboration of the underlying molecular mechanism in human colon cancer cell and tumor xenograft. Results: AST decreased the protein level of VEGF and bFGF in HCT 116 colon cancer cells in a time- and dose-dependent manner. Among the Akt/mTOR signal transduction molecules being examined, AST caused PTEN upregulation, reduction in Akt phosphorylation and subsequent activation of mTOR. AST also suppressed the induction of HIF-1α and VEGF under CoCl₂-mimicked hypoxia. These effects were intensified by combined treatment of AST with the mTOR inhibitor rapamycin. Despite this, our data also indicate that AST could attenuate cobalt chloride-evoked COX-2 activation, while such effect on COX-2 and its downstream target VEGF was intensified when indomethacin was concurrently treated. The anti-carcinogenic action of AST was further illustrated in HCT 116 xenografted athymic nude mice. AST significantly suppressed tumor growth and reduced serum VEGF level in vivo. In the tumor tissues excised from AST-treated animals, protein level of p-Akt, p-mTOR, VEGF, VEGFR1 and VEGFR2 was down-regulated. Immunohistochemistry has also revealed that AST effectively reduced the level of COX-2 in tumor sections when compared with that in untreated control. Conclusion: Taken together, these findings suggest that AST exerts anti-carcinogenic activity in colon cancer cells through modulation of mTOR signaling and downregulation of COX-2, which together reduce VEGF level in tumor cells that could potentially suppress angiogenesis.

Astragalus membranaceus has been used to ameliorate the side effects of antineoplastic drugs because of its immunomodulating nature. We had recently demonstrated that total Astragalus saponins (AST) possess anticarcinogenic and proapoptotic properties in human colon cancer cells and tumor xenograft. In this study, we identified NSAID‐activated gene (NAG‐1) as a potential molecular target of AST. The growth‐inhibitory and proapoptotic effects of AST were assessed in a panel of human cancer cell lines. Hoechst 33342 nuclear staining, Annexin V‐FITC/propidium iodide staining, Western immunoblotting, real‐time PCR, luciferase reporter assay and electrophoretic mobility shift assay were conducted to determine the association of NAG‐1 and related transcription factors with AST during its regulation of apoptotic activities. Moreover, the combined proapoptotic and NAG‐1 promoting activities of AST and/or inhibitors of the PI3K‐Akt pathway were also examined. AST caused overexpression of NAG‐1, leading to PARP cleavage and apoptosis. The induction of NAG‐1 promoter activity by the drug was associated with increased gene expression, in addition to prior increase in Egr‐1 expression and DNA binding activity. AST‐induced NAG‐1 activation was intensified when PI3K inhibitor LY294002 or Akt inhibitor was co‐treated and reversed by NAG‐1 siRNA transfection. Nevertheless, the extent of NAG‐1 induction could not be altered by the ERK inhibitor PD98059. Our results indicate that NAG‐1 is a potential molecular target of AST in its antitumorigenic and proapoptotic actions, which would have additive effects when used along with PI3K‐Akt inhibitors. The information obtained could facilitate future development of a novel target‐specific chemotherapeutic agent with known molecular pathway. © 2009 UICC

Glucose-regulated proteins (GRP) are induced in the cancer microenvironment to promote tumor survival, metastasis and drug resistance. AST was obtained from the medicinal plant Astragalus membranaceus, which possesses anti-tumor and pro-apoptotic properties in colon cancer cells and tumor xenograft. The present study aimed to investigate the involvement of GRP in endoplasmic reticulum (ER) stress-mediated apoptosis during colon cancer development, with focus on the correlation between AST-evoked regulation of GRP and calpain activation. The effects of AST on GRP and apoptotic activity were assessed in HCT 116 human colon adenocarcinoma cells. Calpain activity was examined by using a fluorescence assay kit. Immunofluorescence staining and immunoprecipitation were employed to determine the localization and association between calpains and GRP. GRP78 gene silencing was performed to confirm the importance of GRP in anticancer drug activities. The modulation of GRP and calpains was also studied in nude mice xenograft. ER stress-mediated apoptosis was induced by AST, as shown by elevation in both spliced XBP-1 and CHOP levels, with parallel up-regulation of GRP. The expression of XBP-1 and CHOP continued to increase after the peak level of GRP was attained at 24 h. Nevertheless, the initial increase in calpain activity as well as calpain I and II protein level was gradually declined at later stage of drug treatment. Besides, the induction of GRP was partly reversed by calpain inhibitors, with concurrent promotion of AST-mediated apoptosis. The knockdown of GRP78 by gene silencing resulted in higher sensitivity of colon cancer cells to AST-induced apoptosis and reduction of colony formation. The association between calpains and GRP78 had been confirmed by immunofluorescence staining and immunoprecipitation. Modulation of GRP and calpains by AST was similarly demonstrated in nude mice xenograft, leading to significant inhibition of tumor growth. Our findings exemplify that calpains, in particular calpain II, play a permissive role in the modulation of GRP78 and consequent regulation of ER stress-induced apoptosis. Combination of calpain inhibitors and AST could exhibit a more pronounced pro-apoptotic effect. These results help to envisage a new therapeutic approach in colon cancer by targeting calpain and GRP.