PML and TRF2 protein expression in hereditary and sporadic colon cancer.

The PML (promyelocytic leukemia) protein is concentrated in the PML nuclear bodies. In human cell lines and tumors maintaining their telomeres by alternative lengthening (ALT), the PML protein is colocalized with TRF2 and several other proteins in the so called ALT-associated PML bodies. The aim of this study was to determine if there is any difference in PML protein expression between tumors with stable microsatellites (MSS) and those with high-frequency microsatellite instability (MSI-H), if PML protein expression might be a prognostic factor and if MSI-H tumors more frequently use alternative lengthening of telomeres measured by the presence of ALT-associated PML bodies. Eighty colorectal cancer samples (32 MSI-H and 48 MSS) and 8 human tumor cell lines (Saos-2, U2OS, DU145, LNCaP, U87, HeLa, MCF7 and T98G) were included into the study. Double-colour immunofluorescence staining was used. Downregulation of PML protein expression was found in 7 of 32 (22%) MSI-H and 11 of 48 (23%) MSS tumors (p=0.520). There was no correlation between PML expression and age, histological typing, localization of the tumor in colon, TNM classification, disease-free and overall survival. The Saos-2 and U2OS (ALT using cell lines) and the MCF7 (active telomerase) cell line were characterized by the presence of ALT-associated PML bodies; no such bodies were detected in the DU145, LNCaP, U87, HeLa and T98G cell lines (active telomerase); accumulation of TRF2 was absent or much weaker in these cell lines compared to Saos-2 or U2OS. Accumulation of the TRF2 protein was detected in 16 of 80 (20%) tumors and PML and TRF2 colocalization in 2 MSI-H tumors (6%). In conclusion, the PML protein was downregulated in approximately 20% of tumors; there was no difference between MSS and MSI-H tumors. PML protein expression does not seem to be a prognostic factor.

Immunohistochemical detection of the hMLH1 and hMSH2 proteins in hereditary non-polyposis colon cancer and sporadic colon cancer.

Defects in DNA mismatch repair system are involved in carcinogenesis of sporadic and inherited human cancers. We assessed the feasibility of using immunohistochemistry to detect tumors with DNA mismatch repair deficiency. We analyzed 81 samples (74 colon cancers (CC), 1 colon dysplasia and 6 extracolonic cancers) for hMLH1 and hMSH2 protein expression, microsatellite instability (MSI) and/or mutational analysis. A meta-analysis of the published data on immunohistochemistry of hMLH1/hMSH2 proteins was performed. Sensitivity and specificity of the method was calculated. Twenty four of 29 tumors from hMLH1/hMSH2 mutation carriers and 10 of 13 sporadic high frequency MSI tumors lost one of the proteins. None of the 42 tumors with stable microsatellites or low frequency MSI lost the proteins. Based on literature review of 49 publications on colorectal cancer, hMLH1 immunohistochemistry was able to detect 136 of 154 tumors from hMLH1 germline mutation carriers (the sensitivity of 88.3% [95%CI, 85.8-90.8%]), hMSH2 immunohistochemistry detected 99 of 109 tumors from hMSH2 mutation carriers (the sensitivity of 90.8% [95%CI, 88.5-93.1%]), and hMLH1/hMSH2 immunohistochemistry identified 1262 of 1382 tumors with high-frequency microsatellite instability not correlated with mutational analysis (the sensitivity of 91.3% [95%CI, 90.4-92.2%]). The specificity of the method was 99.4% (95%CI, 99.2-99.6%). In conclusion, immunohistochemistry of hMLH1 and hMSH2 proteins is a useful method to predict the presence of mismatch repair deficiency, although its sensitivity is lower than that of MSI analysis.

[Molecular genetics of Wilms' tumor]. / Molekulární genetika Wilmsova tumoru.

Molecular genetics of the Wilms' tumor plays an important role in the elucidation of the genetic etiology of the tumor disease generally. Contrary to the genesis of retinoblastoma, where a single gene is inactivated by two hits, the biological signalling pathways determining the origin of the Wilms' tumor are more complex and several genes in several loci may participate. Formation of the Wilms' tumor is accompanied with the most frequent genetic alteration, which is the loss of heterozygosity on the short arm of chromosome 11. It indicates inactivation of one or several tumor suppressor genes located at 11p region. The most studied gene of the Wilms' tumor is WT1 gene, which has been cloned and sequenced. Biological function of WT1 protein is complex one and it requires probably an interaction with other proteins, DNA and also RNA. The development of the tumor determines not only the genetic changes, but also epigenetic changes, e.g., hypermethylation of promoter and genome imprinting.

Serum leptin levels in patients with anorexia nervosa before and after partial refeeding, relationships to serum lipids and biochemical nutritional parameters.

Leptin is a protein hormone produced by adipocytes that provide information about the body fat content. It was previously reported that serum leptin levels were decreased in patients with anorexia nervosa in comparison with healthy control subjects. The aim of our study was to compare serum leptin levels in patients with anorexia nervosa (n=11, initial mean BMI=15.4 kg/m2) before and after partial recovery with control age-matched subjects (n=11, mean BMI= 20.3 kg/m2) and to study the relationships of leptin levels, serum lipids and biochemical nutritional parameters. We found that serum leptin concentrations in patients with anorexia nervosa were significantly reduced in comparison with control subjects (3.61 vs 9.37 ng.ml(-1), p<0.01). Serum cholesterol, triglycerides, total protein and albumin in patients with anorexia nervosa either before or after partial recovery did not differ from the control group. After partial recovery, a significant increase in serum leptin was observed (4.83 vs 3.61 ng.ml(-1), p<0.05), but the values still remained significantly lower than in the control group (p<0.01) Leptin levels correlated positively with the body mass index in the control group and anorexia nervosa group before recovery. The correlation with BMI in the anorexia nervosa group after refeeding was not significant. No significant correlation was found between leptin concentrations and serum lipids, total protein, albumin and prealbumin, respectively. Serum leptin thus represents a sensitive parameter that reflects the nutritional status in patients with anorexia nervosa suitable for long-term follow up during refeeding therapy.