Hardi Luehrs

Beneficial health effects of low-digestible carbohydrate consumption.

Low-digestible carbohydrates represent a class of enzyme-resistant saccharides that have specific effects on the human gastrointestinal tract. in the small bowel, they affect nutrient digestion and absorption, glucose and lipid metabolism and protect against known risk factors of cardiovascular disease. In the colon they are mainly degraded by anaerobic bacteria in a process called fermentation. As a consequence, faecal nitrogen excretion is enhanced, which is used clinically to prevent or treat hepatic encephalopathy. Low-digestible carbohydrates are trophic to the epithelia of the ileum and colon, which helps to avoid bacterial translocation. Short-chain fatty acids are important fermentation products and are evaluated as new therapeutics in acute colitis. They are considered in the primary prevention of colorectal cancer. The bifidogenic effect of fructo-oligosaccharides merits further attention, Unfermented carbohydrates increase faecal bulk and play a role in the treatment of chronic functional constipation, symptomatic diverticulosis and, possibly, the irritable bowel syndrome. In conclusion, low-digestible carbohydrates may play a role in the maintenance of human digestive health. However, the strength of evidence differs between disease entities.

Spectral karyotype analysis of colon cancer cell lines of the tumor suppressor and mutator pathway.

Background and aims: Microsatellite instability (MSI) is characterized by the size variation of microsatellites in tumor DNA as compared to matching normal DNA due to defects in the mismatch repair system. To examine the chromosomal differences in microsatellite-stable (MSS) and -unstable (MSI) tumors in detail, we analyzed MSS (Caco-2, Colo-205, SW948) and MSI (HCT-15, HCT-116, LoVo) cell lines by spectral karyotyping (SKY). Methods: SKY is a sensitive method to detect chromosome aberrations by visualizing each chromosome in a different color. Metaphases were hybridized with a SKY probe mixture. Images were visualized with the SpectraCube system and analyzed with the SKYview imaging software. Results: The average number of chromosomes was 49 in LoVo, 45 in HCT-116, 46 in HCT-15, 71 in Colo-205, 89 in Caco-2 and 66 in SW-948. Three aberrant chromosomes were detected in LoVo, three in HCT-116, two in HCT-15, seventeen in Colo-205, fourteen in Caco-2 and nine in SW948. Conclusion: The karyotypes of MSS colon cancer cells displayed complex numerical and structural aberrations. In contrast the chromosomes of MSI colon cancer cells were mostly unaltered but displayed a few isolated numerical and structural aberrations. We speculate that these isolated aberrations may be specifically involved in the pathogenesis of MSI tumors.

Spectral karyotyping and SNP microarray analysis define uniparental disomy (UPD) as a novel mutational mechanism in MSI- and CSI-colorectal cancers ∗

Spectral karyotyping greatly improves recognition and definition of chromosomal aberrations [1]. In previous studies, we applied spectral karyotyping to a number of colorectal cancer cell lines derived from metastatic and primary tumors [2]. As expected, we observed complex marker chromosomes and pronounced chromosomal instability (CSI) in tumors devoid of microsatellite instability. In contrast, microsatellite instable (MSI) tumors uniformly displayed stable karyotypes [3]. Likewise, a newly characterized adenoma cell line lacked karyotypic alterations [4]. Recently, we complemented our spectral karyotyping studies by SNP-array analyses of multiple MSIand CSI-cell lines [5]. Results were verified by the analysis of 15 primary MSIand 15 CSI-tumors (unpublished data). SNP analysis greatly facilitated the interpretation of complex chromosomal alterations of CSI-cell lines. Monoallelic regions could be correlated with sites of inactivated tumor suppressor genes and activated oncogenes. Some of the genes relevant for colon carcinogenesis are inactivated by allelic loss (e.g. p53, SMAD4). Monoallelic regions with increased copy number may represent oncogene loci activated by allele-specific amplification (e.g. Cyclin D1 in CSI-cell lines). Monoallelic regions without copy number alterations fulfill the criteria of uniparental disomy (UPD). In the tested colorectal cell lines and primary tumors, UPD appears to instrumental in the inactivation of early-acting tumor suppressor genes, including APC in CSIand hMLH1/hMSH2 in MSI-cellular phenotypes. Our results suggest that following initial mutational inactivation of one of the APC or hMLH1/hMSH2 alleles the remaining wildtype allele is deleted, concomitant with re-duplication of the mutated allele. Alternatively, UPD may have arisen through some type of gene conversion. In addition to the APC and hMLH1/hMSH2 chromosomal

Abstract 2248: Oncogenic actions of HDGF (hepatoma-derived growth factor) in colorectal cancer: Implication for tumor biology/ patient prognosis and modulation by butyrate

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL HDGF was identified as an oncogene relevant for colon cancer carcinogenesis by cDNA-array analysis, RT-PCR and immunohistochemistry. The analysis were performed in colonic adenoma (Geki2), carcinoma (HT29) and metastasis (SW620) cell lines, and in 50 colorectal cancer tissues and corresponding normal mucosa. By incubation of the cell lines with the short chain fatty acid butyrate (4mM), it was possible to (down-) regulate the HDGF-expression level. In the patients we analysed, HDGF overexpression was not associated with a worse prognosis or any other clinical parameter. To study the mechanisms of action of HDGF we stably transfected a HDGF-siRNA containing plasmid into HT29 colon carcinoma cells, resulting in a almost complete inactivation of HDGF-expression. This blocking leads to altered growth characteristics and cell differentiation and the cells exhibit potent pro-apoptotic properties. An affymetrix-expression array was performed and first results will me shown at the meeting. In conclusion, HDGF might be a potential therapeutic target for human colorectal cancer and a modulation of expression is possible by the short chain fatty acid butyrate. These findings may have major implications in the treatment of colorectal cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2248. doi:10.1158/1538-7445.AM2011-2248