fumonisin-b1 and Kidney-Neoplasms

The mycotoxin fumonisin B1 (FB1) is an important contaminant of maize and maize-based products. In rodent toxicity studies, FB1 was shown to be hepato- and nephrotoxic, and to induce renal tumors in rats when administered via the diet. Of particular note are the aggressive growth characteristics of FB1-induced tumors with a high potential to metastasize. While genotoxicity does not appear to contribute to FB1 carcinogenicity, it is well established that FB1-mediated disruption of sphingolipid metabolism plays a key role in FB1 toxicity. This review provides an overview on human dietary exposure to FB1, FB1 toxicity and carcinogenicity, and potential mechanisms involved in FB1-mediated tumor formation, with a particular focus on cellular functions of sphingolipids and biological consequences of FB1-mediated perturbation of sphingolipid metabolism.

Topics: Animals; Food Contamination; Fumonisins; Humans; Kidney Neoplasms; Rats

The rates of cell proliferation and cell loss in conjunction with the differentiation status of a tissue are among the many factors contributing to carcinogenesis. Nongenotoxic (non-DNA reactive) chemicals may affect this balance by increasing proliferation through direct mitogenesis or through a regenerative response following loss of cells through cytotoxic (oncotic) or apoptotic necrosis. In a recent NTP study in Fischer rats and B6C3F(1) mice, the mycotoxin fumonisin B(1) caused renal carcinomas in male rats and liver cancer in female mice. In an earlier study in male BD-IX rats, fumonisin B(1) caused hepatic toxicity and hepatocellular carcinomas. An early effect of fumonisin B(1) exposure in these target organs is apoptosis. However, there is also some evidence of oncotic necrosis following fumonisin B(1) administration, especially in the liver. Induction of apoptosis may be a consequence of ceramide synthase inhibition and disruption of sphingolipid metabolism by fumonisin B(1). Fumonisin B(1) is not genotoxic in bacterial mutagenesis screens or in the rat liver unscheduled DNA-synthesis assay. Fumonisin B(1) may be the first example of an apparently nongenotoxic (non-DNA reactive) agent producing tumors through a mode of action involving apoptotic necrosis, atrophy, and consequent regeneration.

Topics: Africa; Animals; Apoptosis; Carboxylic Acids; China; Decision Making; DNA; Esophageal Neoplasms; Female; Fumonisins; Humans; Kidney; Kidney Neoplasms; Liver; Liver Neoplasms; Male; Mice; Mice, Inbred Strains; Mycotoxins; Rats; Rats, Inbred Strains; Risk Factors; Sphingolipids

Renal cell carcinoma is the most common neoplasm occurring in the kidney and is largely resistant to current chemotherapy. Understanding the mechanisms involved in renal carcinoma cell death may lead to novel and more effective therapies. In Cak(i)-1 renal cancer cells, using phosphatidylserine externalization as a marker of apoptosis, the anti-cancer drugs 5-fluorouracil (5-FU), and its pro-drugs, doxifluridine (Dox) and floxuridine (Flox) proceeds via a caspase-dependent mechanism. In contrast, phosphatidylserine externalization produced by staurosporine in the renal cancer cell lines Cak(i)-1 and A-498 proceeds via a caspase-independent mechanism. That is, the pan caspase inhibitor N-benzyloxycabonyl-Val-Ala-Asp-fluoromethylketone (ZVAD) did not ameliorate annexin V binding, cell shrinkage or changes in nuclear morphology. Subsequent experiments were conducted to determine mediators of phosphatidylserine externalization, using annexin V binding, when caspases were inhibited. Prior treatment of A-498 cells with cathepsin B (CA74 methyl ester), cathespsin D (pepstatin A) or calpain inhibitors (calpeptin, E64d) in the presence or absence of ZVAD did not ameliorate annexin V binding. The endonuclease inhibitor aurintricarboxylic acid (ATA), phospholipase A(2) inhibitor bromoenol lactone (BEL), protein synthesis inhibitor cycloheximide (CH) and chloride channel blockers niflumic acid (NFA) and 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) all had no effect on staurosporine-induced annexin V binding in A-498 cells either in the presence or absence of ZVAD. We also modulated sphingomyelin and the de novo pathways of ceramide synthesis and found no amelioration of staurosporine-induced annexin V binding in A-498 cells either in the presence or absence of ZVAD. These results indicate that 5-FU, Dox and Flox induce externalization of phosphatidylserine during apoptosis in Cak(i)-1 renal cancer cells primarily through a caspase-dependent mechanism and that externalization of phosphatidylserine during apoptosis produced by staurosporine in the renal cancer cell line A-498 is independent of many of the common signaling pathways known to be involved in this process.

Topics: Amino Acid Chloromethyl Ketones; Aniline Compounds; Antimetabolites, Antineoplastic; Apoptosis; Benzoic Acid; Benzylidene Compounds; Calpain; Caspases; Cathepsin B; Cathepsin D; Cell Line, Tumor; Cell Size; Ceramides; Cisplatin; Exocytosis; Fumonisins; Humans; Kidney Neoplasms; Naphthalenes; Niflumic Acid; Nitrobenzoates; Phosphatidylserines; Pyrones; Sphingomyelin Phosphodiesterase; Staurosporine; Triterpenes

Fumonisins are fungal metabolites and suspected human carcinogens. They inhibit ceramide synthase in vitro, enhance tumor necrosis factor alpha (TNFalpha) production, and cause apoptosis. Fumonisin B1 (FB1) was fed to rats and mice for 2 years or, in separate studies, given to rats or mice for up to 4 weeks. Kidney tubule adenomas and carcinomas were found in male rats fed > or = 50 ppm, whereas liver adenomas and carcinomas were found in female mice fed > or = 50 ppm for 2 years. In the short-term studies, increases in tissue concentration of the ceramide synthase substrate sphinganine (Sa) and the Sa to sphingosine (So) ratio were correlated with apoptosis. Further, hepatotoxicity was ameliorated in mice lacking either the TNFR1 or the TNFR2 TNFalpha receptors. Thus, FB1 was carcinogenic to rodents and thefindings support the hypothesis that disrupted sphingolipid metabolism and TNFalpha play important roles in its mode of action.

Topics: Adenoma; Animals; Apoptosis; Carcinogens, Environmental; Enzyme Inhibitors; Female; Fumonisins; Fusarium; Kidney; Kidney Neoplasms; Liver; Liver Neoplasms, Experimental; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Mycotoxins; Oxidoreductases; Rats; Rats, Inbred F344; Receptors, Tumor Necrosis Factor; RNA, Messenger; Sphingolipids; Sphingosine

Laboratory studies have described the carcinogenicity of fumonisin B1 (FB1) in rodents and epidemiological evidence suggests an association between FB1 (a mycotoxin produced by Fusarium moniliforme) and cancer in humans. This study was designed to reveal in rainbow trout, a species with very low spontaneous tumor incidence, if FB1 was (i) a complete carcinogen, in the absence of an initiator; (ii) a promoter of liver tumors in fish initiated as fry with aflatoxin B1 (AFB1); and (iii) a promoter of liver, kidney, stomach, or swim bladder tumors in fish initiated as fry with N-methyl-N'-nitro-nitrosoguanidine (MNNG). FB1 was not a complete carcinogen in trout. No tumors were observed in any tissue of fish fed diets containing 0, 3.2, 23, or 104 ppm FB1 for a total of 34 weeks (4 weeks FB1 exposure, 2 weeks outgrowth on control diet, followed by 30 weeks FB1 diet) in the absence of a known initiator. FB1 promoted AFB1 initiated liver tumors in fish fed > or = 23 ppm FB1 for 42 weeks. A 1-week pretreatment of FB1 did not alter the amount of liver [3H]AFB1 DNA adducts, which suggests that short-term exposure to FB1 will not alter phase I or phase II metabolism of AFB1. In MNNG-initiated fish, liver tumors were promoted in the 104 ppm FB1 treatment (42 weeks), but FB1 did not promote tumors in any other tissue. Tumor incidence decreased in kidney and stomach in the 104 ppm FB1 treatment of MNNG-initiated trout. The FB1 promotional activity in AFB1-initiated fish was correlated with disruption of sphingolipid metabolism, suggesting that alterations in associated sphingolipid signaling pathways are potentially responsible for the promotional activity of FB1 in AFB1-initiated fish.

Topics: Aflatoxin B1; Air Sacs; Animals; Carboxylic Acids; Carcinogenicity Tests; Carcinogens; Diet; Drug Synergism; Fumonisins; Kidney Neoplasms; Liver; Liver Neoplasms, Experimental; Methylnitronitrosoguanidine; Mycotoxins; Oncorhynchus mykiss; Sphingosine; Stomach Neoplasms

Fumonisin B1 (FB1) is a mycotoxin isolated from Fusarium fungi that contaminate crops worldwide. A previous study demonstrated that FB1 promoted preneoplastic foci in initiated rats and induced hepatocellular carcinomas in BD IX rats at 50 parts per million (ppm), but fundamental dose-response data were not available to assist in setting regulatory guidelines for this mycotoxin. To provide this information, female and male F344/N/Nctr BR rats and B6C3F1 Nctr BR mice were fed for two years a powdered NIH-31 diet containing the following concentrations of FB1: female rats, 0, 5, 15, 50, and 100 ppm; male rats, 0, 5, 15, 50, and 150 ppm; female mice, 0, 5, 15, 50, and 80 ppm; male mice, 0, 5, 15, 80, and 150 ppm. FB1 was not tumorigenic in female F344 rats with doses as high as 100 ppm. Including FB1 in the diets of male rats induced renal tubule adenomas and carcinomas in 0/48, 0/40, 9/48, and 15/48 rats at 0, 5, 15, 50, and 150 ppm, respectively. Including up to 150 ppm FB1 in the diet of male mice did not affect tumor incidence. Hepatocellular adenomas and carcinomas were induced by FB1 in the female mice, occurring in 5/47, 3/48, 1/48, 19/47, and 39/45 female mice that consumed diets containing 0, 5, 15, 50, and 80 ppm FB1, respectively. This study demonstrates that FB1 is a rodent carcinogen that induces renal tubule tumors in male F344 rats and hepatic tumors in female B6C3F1 mice.

Topics: Animal Feed; Animals; Biological Assay; Body Weight; Carboxylic Acids; Carcinogens, Environmental; Dose-Response Relationship, Drug; Female; Fumonisins; Fusarium; Kidney; Kidney Neoplasms; Kidney Tubules; Liver; Liver Neoplasms, Experimental; Male; Mice; Mice, Inbred Strains; Mycotoxins; Rats; Rats, Inbred F344; Survival Analysis

Fumonisin B1(FB1) is a fungal metabolite of Fusarium verticillioides (= F. moniliforme), a fungus that grows on many crops worldwide. Previous studies demonstrated that male BD IX rats consuming diets containing 50 ppm fumonisin B1 developed hepatocellular carcinomas. In our recent studies, diets containing FB1 at 50 ppm or higher concentrations induced renal tubule carcinomas in male F344/N/Nctr BR rats and hepatocellular carcinomas in female B6C3F1/Nctr BR mice. The carcinogenicity of FB1 in rats and mice is not due to DNA damage, as several laboratories have demonstrated that FB1 is not a genotoxin. FB1 induces apoptosis in cells in vitro. Including FB1 in the diets of rats results in increased hepatocellular and renal tubule epithelial cell apoptosis. In studies with F344/N/Nctr BR rats consuming diets containing up to 484 ppm FB1 for 28 days, female rats demonstrated more sensitivity than male rats in the induction of hepatocellular apoptosis and mitosis. Conversely, induction of renal tubule apoptosis and regeneration were more pronounced in male than in female rats. Induction of renal tubule apoptosis and hyperplasia correlated with the incidence of renal tubule carcinomas that developed in the 2-year feeding study with FB1 in the F344/N/Nctr BR rats. The data are consistent with the hypothesis that the induction of renal tubule carcinomas in male rats could be partly due to the continuous compensatory regeneration of renal tubule epithelial cells in response to the induction of apoptosis by fumonisin B1.

Topics: Animals; Apoptosis; Biological Assay; Carboxylic Acids; Carcinogens, Environmental; Cell Survival; Epithelium; Female; Fumonisins; Hepatocytes; Kidney; Kidney Neoplasms; Kidney Tubules; Liver Neoplasms, Experimental; Male; Mitosis; Mycotoxins; Organ Size; Rats; Rats, Inbred F344; Regeneration