Inhibition of angiogenesis as a mechanism for inhibition by 1alpha-hydroxyvitamin D3 and 1,25-dihydroxyvitamin D3 of colon carcinogenesis induced by azoxymethane in Wistar rats

Angiogenesis as a biomarker and target in cancer chemoprevention

Angiogenesis, the formation of new blood vessels from existing vasculature, is essential to the late stages of carcinogenesis, allowing tumours to grow beyond 1-2 mm in diameter, invade surrounding tissue, and metastasise. However, more than two decades ago, angiogenesis that preceded neoplastic transformation was seen. Indeed, it can be detected in inflammatory and infectious diseases that increase the risk of developing cancer. Recent advances in fluorescence endoscopy and histological assessment suggest that, for certain cancers, the degree of new blood-vessel formation may differ between the early and late stages of carcinogenic progression. The association between angiogenesis and cancer occurrence, and ease of detection of this process in accessible tissues early in carcinogenesis, mean that angiogenesis fulfils the criteria for a biomarker of the effectiveness of chemopreventive intervention. There is also some evidence that biochemical assays of angiogenic growth factors may offer similar potential as surrogate biomarkers. Many natural and synthetic chemopreventive agents in development or in clinical use inhibit new vessel formation in vivo. Validation of angiogenesis as a biomarker for the effectiveness of chemoprevention should further the advancement of some chemopreventive agents.

Isolation of an antitumor compound from Agaricus blazei Murill and its mechanism of action

The Basidiomycete fungus Agaricus blazei Murill has traditionally been used as a health food for the prevention of cancer, diabetes, hyperlipidemia, arteriosclerosis and chronic hepatitis. In the present study, we examined the antitumor activities of various substances isolated from the lipid fraction of A. blazei. Tumor growth was retarded by the oral administration of the lipid fraction extracted from A. blazei with a chloroform/methanol mixture in sarcoma 180-bearing mice. The substance with the antitumor activity in the lipid fraction was isolated via silica gel column chromatography, eluted with an acetonitrile/methanol (3:2) mixture and identified as ergosterol by direct comparison of the (1)H NMR and mass spectrometry spectral data of an authentic sample. The oral administration of ergosterol to sarcoma 180-bearing mice significantly reduced tumor growth at doses of 400 and 800 mg/kg administered for 20 d without side effects, such as the decreases in body, epididymal adipose tissue, thymus, and spleen weights and leukocyte numbers induced by cancer chemotherapy drugs. Ergosterol had no cytotoxicity against tumor cells. To clarify the antitumor activity of ergosterol, we examined the effects of ergosterol on tumor-induced angiogenesis using two in vivo models. Intraperitoneal administration of ergosterol at doses of 5, 10 and 20 mg/kg for 5 consecutive d inhibited the neovascularization induced by Lewis lung carcinoma cell-packed chambers, suggesting that either ergosterol or its metabolites may be involved in the inhibition of tumor-induced neovascularization. Therefore, we further examined the inhibitory effects of ergosterol on Matrigel-induced neovascularization. Female C57BL/6 mice were subcutaneously inoculated with Matrigel containing acidic fibroblast growth factor and heparin with or without ergosterol. Ergosterol inhibited the Matrigel-induced neovascularization, suggesting that ergosterol directly inhibits Matrigel-induced neovascularization. From these results, it seems likely that the antitumor activity of ergosterol might be due to direct inhibition of angiogenesis induced by solid tumors. This is the first report of ergosterol as an antiangiogenic substance.

The role of vitamin D in normal and pathologic processes in the colon

Vitamin D(3) metabolites and analogues have recently been shown to play an important role in the regulation of a number of important cellular processes, including proliferation, differentiation, and apoptosis, in addition to their established roles in mineral homeostasis. The actions of these secosteroids involve both rapid, nongenomic effects and genomic effects; the latter mediated via the vitamin D receptor and other transcription factors. Their effects have been described in a variety of cell types, including normal and malignant colonocytes. This article summarizes the rapid and genomic actions of vitamin D(3) metabolites and analogues on normal and pathologic processes in the colon, with particular emphasis on the potential of these secosteroids to prevent colon cancer.

Effectiveness of the near-infrared electronic endoscope for diagnosis of the depth of involvement of gastric cancers

BACKGROUND

Near-infrared light penetrates deeply into tissue but is not visible with a conventional endoscope. We developed a new infrared electronic endoscope system and evaluated its usefulness for assessing the depth of involvement of gastric cancers.

METHODS

A total of 61 patients with depressed or ulcerated gastric cancers underwent infrared endoscopy after intravenous injection of indocyanine green.

RESULTS

Intramucosal cancers were observed as tumors with or without a homogeneous tumor stain, whereas submucosal or deeper cancers were observed as tumors with an inhomogeneous stain or with pooling of the dye. Histologic examination showed staining properties of gastric cancers were significantly correlated with the characteristics of the vascular bed. The accuracy for depth of cancer invasion was 89% for mucosal cancers and 89% for submucosal or deeper cancers.

CONCLUSION

Our new infrared electronic endoscope system was useful for distinguishing mucosal cancers from submucosal or deeper cancers either with or without ulcerative changes.

Recent developments in the use of vitamin D analogues

The non-classical effects of 1alpha,25-dihydroxyvitamin D(3) (1alpha, 25(OH)(2)D(3)) create possible therapeutic applications for immune modulation (e.g., autoimmune diseases and graft rejection), inhibition of cell proliferation (e.g., psoriasis, cancer) and induction of cell differentiation (e.g., cancer). The major drawback related to the use of 1alpha,25(OH)(2)D(3) is its calcaemic effect, which prevents the application of pharmacological concentrations. Intensive research has led to the development of analogues of 1(2)D(3) characterised by a clear dissociation of the antiproliferative and prodifferentiating capacity from the calcaemic effects. Due to this dissociation, these analogues can be used not only for the treatment of bone disorders but also for non-classical applications. In the present review, a summary is given on the use of the 1alpha,25(OH)(2)D(3) analogues for the treatment of cancer, skin and immune disorders and for the prevention of graft rejection. Moreover a brief overview is given on the use of analogues for secondary hyperparathyroidism.

The significance of thymidine phosphorylase activity in hepatocellular carcinoma and chronic diseased livers: a special reference to liver fibrosis and multicentric tumor occurrence

The role of thymidine phosphorylase (TP), an angiogenic factor, in hepatocellular carcinoma (HCC) remains unclear. The aim of this study was to clarify the significance of TP in HCC. Thirty-seven patients with HCC, who underwent hepatectomy, were included. The TP activity in both cancerous and non-cancerous parts of livers were measured by an enzyme-linked immunosorbent assay. Another 11 patients without HCC were used to evaluate the TP activity in the non-cancerous parts of livers. Both the cancerous and non-cancerous TP activities were clinico-pathologically investigated with special reference to the multicentric occurrence of HCCs and the degree of liver fibrosis; consisting of normal, fibrosis and cirrhosis. The TP activity in the cancerous part was 94.6 +/- 70.2 U/mg protein, while that in non-cancerous parts of the liver was 80.9 +/- 48.8 U/mg protein. No significant difference was observed. The TP activity in the cancerous part did not correlate with any clinicopathological variables, such as tumor differentiation, portal vein invasion, intrahepatic metastases and prognosis. However, the TP activity in the non-cancerous parts of the liver correlated with the degree of fibrosis (normal/fibrosis/cirrhosis = 34:74:90 U/ mg protein, respectively). Furthermore, regarding the correlation between TP activity in the non-cancerous parts and the simultaneously multicentric occurrence of HCC, the TP activity in the multicentric group (n = 8; 121 U/mg protein) was significantly higher than that in the non-multicentric group (n = 29; 70 U/mg protein). The TP activity in the non-cancerous parts increased in proportion to the degree of liver fibrosis. Furthermore, it is suggested that the higher TP activity in the non-cancerous part is related to the multicentric occurrence of HCCs.