Truncated PPM1D impairs stem cell response to genotoxic stress and promotes growth of APC-deficient tumors in the mouse colon.

Protein phosphatase magnesium-dependent 1 delta (PPM1D) terminates cell response to genotoxic stress by negatively regulating the tumor suppressor p53 and other targets at chromatin. Mutations in the exon 6 of the PPM1D result in production of a highly stable, C-terminally truncated PPM1D. These gain-of-function PPM1D mutations are present in various human cancers but their role in tumorigenesis remains unresolved. Here we show that truncated PPM1D impairs activation of the cell cycle checkpoints in human non-transformed RPE cells and allows proliferation in the presence of DNA damage. Next, we developed a mouse model by introducing a truncating mutation in the PPM1D locus and tested contribution of the oncogenic PPM1DT allele to colon tumorigenesis. We found that p53 pathway was suppressed in colon stem cells harboring PPM1DT resulting in proliferation advantage under genotoxic stress condition. In addition, truncated PPM1D promoted tumor growth in the colon in Apcmin mice and diminished survival. Moreover, tumor organoids derived from colon of the ApcminPpm1dT/+ mice were less sensitive to 5-fluorouracil when compared to ApcminPpm1d+/+and the sensitivity to 5-fluorouracil was restored by inhibition of PPM1D. Finally, we screened colorectal cancer patients and identified recurrent somatic PPM1D mutations in a fraction of colon adenocarcinomas that are p53 proficient and show defects in mismatch DNA repair. In summary, we provide the first in vivo evidence that truncated PPM1D can promote tumor growth and modulate sensitivity to chemotherapy.

The Gene Score for Predicting Hypertriglyceridemia: New Insights from a Czech Case-Control Study.

BACKGROUND: Plasma triglyceride (TG) values are significant predictors of cardiovascular and total mortality. The plasma levels of TGs have an important genetic background. We analyzed whether 32 single nucleotide polymorphisms (SNPs) identified in genome-wide association studies are discriminators of hypertriglyceridemia (HTG) in the Czech population. OBJECTIVES: The objective of this study was to replicate and test the original findings in an independent study and to re-analyze the gene score leading to HTG. METHODS: In total, we analyzed 32 SNPs in 209 patients with plasma TG levels over 10 mmol/L (HTG group) and compared them in a case-control design with 524 treatment-naïve controls (normotriglyceridemic [NTG] group) with plasma TG values below 1.8 mmol/L. RESULTS: Sixteen SNPs were significantly associated with an increased risk of HTG development, with odds ratios (ORs) (95% confidence interval [CI]) varying from 1.40 (1.01-1.95) to 4.69 (3.29-6.68) (rs964184 within the APOA5 gene). Both unweighted (sum of the risk alleles) and weighted gene scores (WGS) (log of the achieved ORs per individual genotype) were calculated, and both gene scores were significantly different between groups. The mean score of the risk alleles was significantly increased in the HTG group compared to the NTG group (18.5 ± 2.5 vs. 15.7 ± 2.3, respectively; P < 0.00001). Subjects with a WGS over 9 were significantly more common in the HTG group (44.5%) than in the NTG group, in which such a high score was observed in only 4.7% of subjects (OR 16.3, 95% CI 10.0-36.7; P < 0.0000001). CONCLUSIONS: An increased number of risk genetic variants, calculated both in a weighted or unweighted manner, significantly discriminates between the subjects with HTG and controls. Population-specific sets of SNPs included into the gene score seem to yield better discrimination power.

[MedPed - the reality of familial hypercholesterolemia care at the biggest center]. / MedPed - realita péce o familiární hypercholesterolemie v nejvetsím centru.

The MedPed project (Make Early Diagnosis to Prevent Early Deaths) aiming at screening, diagnosis and treatment of patients with familial hypercholesterolemia (FH) was initiated more than 19 years ago. More than 60 cooperating centers and a large number of health care professionals have been involved. Till November 15, 2017 the nationwide database has comprised 7 567 entries of individual FH patients, 439 of these being children up to 19 years of age. Given the recently corrected estimated population frequency of FH of 1 to 250 this number represents 18.9 % of the predicted number of 40 000 FH individuals in the Czech Republic. Although the number of patients captured by the database seems to be relatively low, it is the third highest number in the world. This review describes working procedures of one of the national leading centers for FH in the Czech Republic. Additionally, a comparison of the up-to-date data set of 558 FH individuals being actively followed in the center to the original FH cohort (n = 190) as described by prof. Sobra in the late 1960 s. is being discussed.Key words: familial hypercholesterolemia - heterozygous - homozygous - project Medped.

[Hyperlipoproteinemia and dyslipidemia as rare diseases. Diagnostics and treatment]. / Hyperlipoproteinemie a dyslipidemie jako vzácná onemocnení: diagnostika a lécba.

Hyperlipoproteinemia (HLP) and dyslipidemia (DLP) are of course mainly perceived as diseases of common incidence and are typically seen as the greatest risk factors (RF) in the context of the pandemic of cardiovascular diseases. This is certainly true and HLP or DLP overall affect tens of percents of adults. However we cannot overlook the fact that disorders (mostly congenital) of lipid metabolism exist which, though not formally defined as such, amply satisfy the conditions for classification as rare diseases. Our account only includes a brief overview of the rare HLPs based on the dominant disorder of lipid metabolism, i.e. we shall mention the rare primary forms of hypercholesterolemia, primary forms of hypertriglyceridemia and the rare primary combined forms of HLP. In recent years an amazing progress has been reached relating to these diseases, in particular in the area of exact identification of the genetic defect and the mechanism of defect formation, however each of these diseases would require a separate article, though outside the field of clinical internal medicine. Therefore we shall discuss homozygous familial hypercholesterolemia (FH) in greater depth, partially also the "severe" form of heterozygous FH and in the following part the lipoprotein lipase deficiency; that means, diseases which present an extreme and even fatal risk for their carriers at a young age, but on the other hand, new therapeutic possibilities are offered within their treatment. An internist then should be alert to the suspicion that the described diseases may be involved, know about their main symptoms, where to refer the patient and how to treat them. Also dysbetalipoproteinemia (or type III HLP) will be briefly mentioned. Homozygous FH occurs with the frequency of 1 : 1 000 000 (maybe even more frequently, 1 : 160 000), it is characterized by severe isolated hypercholesterolemia (overall cholesterol typically equal to 15 mmol/l or more), xanthomatosis and first of all by a very early manifestation of a cardiovascular disease. Myocardial infarction is not an exception even in childhood. The therapy is based on high-dose statins, statins in combination with ezetimib and now also newly on PCSK9 inhibitors. Lomitapid and partly also mipomersen hold great promise for patients. LDL apheresis then represents an aggressive form of treatment. Lipoprotein lipase deficiency (type I HLP) is mainly characterized by severe hypertriglyceridemia, serum milky in colour, and xanthomatosis. A fatal complication is acute recurrent pancreatitis. A critical part of the treatment is diet, however it alone is not enough to control a genetic disorder. The only approved treatment is gene therapy. Experimentally, as an "off label" therapy, it is used in case studies with a lomitapid effect. We have our own experience with this experimental therapy. Dysbetalipoproteinemia is a congenital disorder of lipoprotein metabolism, characterized by high cholesterol (CH) and triglyceride (TG) levels. The underlying cause of this disease is the defect of the gene providing for apolipoprotein E. It is clinically manifested by xanthomatosis, however primarily by an early manifestation of atherosclerosis (rather peripheral than coronary).Key words: Lipoprotein lipase deficiency - dysbetalipoproteinemia - familial hypercholesterolemia - gene therapy - homozygous FH - LDL apheresis - lomitapid - mipomersen - PCSK9 inhibitors - rare diseases.

[Molecular genetics of hypercholesterolemia]. / Molekulární genetika hypercholesterolemie.

The review focuses on the molecular background of an inborn error of lipid metabolism -familial hypercholesterolemia. FH describes a group of genetic defects resulting in severe elevations of blood cholesterol levels and increased risk of premature coronary heart disease. Most cases are due to the mutations decreasing and/or destroying the function of the LDL receptor (85-90 % of cases), smaller portion of cases is caused by defects in the gene encoding the ligand for LDL receptor - apolipoprotein B-100 (5-10 %). Less than 5 % of cases has gain-of-function station of the PCSK9 gene that increases the rate of degradation of the LDL receptor molecules. Autosomal recessive form of the disease, caused by the mutations in LDLR adaptor protein 1 gene, is extremely rare.Key words: APOB - familial hypercholesterolemia - LDLR - LDLRAP1 - PCSK9.

A novel c. 204 Ile68Met germline variant in exon 2 of the mutL homolog 1 gene in a colorectal cancer patient.

Mutations in the mutL homolog 1 (MLH1) gene are frequent in patients with hereditary non-polyposis colorectal cancer (CRC). The MLH1 gene was screened for mutations in patients with sporadic CRC. The nucleotide sequences for all 19 exons of MLH1 were analyzed by high resolution melting and sequenced in a group of 104 sporadic CRC patients, and the results were verified in a replication group of 1,095 patients and 1,469 controls. Different melting profiles for exon 2 of the MLH1 gene were observed in the germline DNA of one patient. Sequencing of the patient's DNA resulted in the identification of a heterozygous C>G variant at c.204, which resulted in an Ile68Met change in the amino acid. A detailed search of the National Center for Biotechnology Information and the 1000 Genomes databases indicated that the detected variant was unique. According to the SIFT and PolyPhen-2 algorithms, the substitution of Ile to Met was predicted to decrease the activity of the MLH1 protein. The newly identified, functional germline variant was not present in any other CRC patient or control. Thus, a novel germline variant in the MLH1 gene was identified, representing a rare event in sporadic CRC. The occurrence and relevance of this mutation in other types of cancer requires additional investigation.

Synchronous gastric and sebaceous cancers, a rare manifestation of MLH1-related Muir-Torre syndrome.

Muir-Torre syndrome (MTS), a rare variant of the hereditary non polyposis colorectal cancer syndrome, is an autosomal dominant genodermatosis characterised by coincidence of sebaceous gland neoplasms (sebaceous adenoma, epithelioma, or carcinoma) and at least one internal malignancy. The underlying cause of MTS is a germline mutation in DNA mismatch repair genes MSH2, MLH1 and MSH6. We report the case of a 52-year-old caucasian woman with the development of metachronous colon cancer at the age of 38 years, uterine cancer at the age of 43 years, and unique occurrence of synchronous gastric and sebaceous carcinomas related to germline point mutation c. 2194A>T in the last exon of MLH1 gene, resulting in truncated protein in C-terminal region p. Lys732X due to premature stop codon. This mutation, not previously reported in MTS, disrupts the function of MutL complexes presumably by preventing the interaction with PMS1/PMS2 and impairing the endonuclease active site. This case points out the importance of sebaceous neoplasia, especially sebaceous adenocarcinoma, as cutaneous markers of MTS for timely implementation of cancer screening programs.

HOTAIR long non-coding RNA is a negative prognostic factor not only in primary tumors, but also in the blood of colorectal cancer patients.

Colorectal cancer (CRC) is one of the main causes of death of neoplasia. Demand for predictive and prognostic markers to reverse this trend is increasing. Long non-coding RNA HOTAIR (Homeobox Transcript Antisense Intergenic RNA) overexpression in tumors was previously associated with poor prognosis and higher mortality in different carcinomas. We analyzed HOTAIR expression levels in tumor and blood of incident sporadic CRC patients in relation to their overall survival with the aim to evaluate surrogate prognostic marker for CRC. Tissue donor group consisted of 73 CRC patients sampled for tumor and normal tissue. Blood donor group was represented by 84 CRC patients compared with 40 healthy controls. Patients were characterized for tumor-node-metastasis stage, tumor grade, microsatellite instability and tumor penetration by stromal cells. HOTAIR levels were assessed by real-time quantitative PCR. CRC patients had higher HOTAIR expression in blood than healthy controls (P = 0.0001), whereas there was no difference in HOTAIR levels between tumor and adjacent mucosa of CRC patients. HOTAIR levels positively correlated between blood and tumor (R = 0.43, P = 0.03). High HOTAIR levels in tumors were associated with higher mortality of patients [Cox's proportional hazard, hazard ratio = 4.4, 95% confidence interval: 1.0-19.2, P = 0.046]. The hazard ratio was even higher when blood HOTAIR levels were taken into account (hazard ratio = 5.9, 95% confidence interval: 1.3-26.1, P = 0.019). Upregulated HOTAIR relative expression in primary tumors and in blood of CRC patients is associated with unfavorable prognosis. Our data suggest that HOTAIR blood levels may serve as potential surrogate prognostic marker in sporadic CRC.

Molecular characteristics of mismatch repair genes in sporadic colorectal tumors in Czech patients.

BACKGROUND: Mismatch repair (MMR) genes are known to be frequently altered in colorectal cancer (CRC). Both genetics and epigenetics modifications seems to be relevant in this phenomenon, however it is still not clear how these two aspects are interconnected. The present study aimed at characterizing of epigenetic and gene expression profiles of MMR genes in sporadic CRC patients from the Czech Republic, a country with one of the highest incidences of this cancer all over Europe. METHODS: Expression levels and CpG promoter methylation status of all MMR genes were evaluated in DNA from tumor and adjacent mucosal samples of 53 incident CRC patients. RESULTS: We have found significantly increased transcription levels in EXO1 gene in tumor tissues (P = 0.05) and significant over-expression of MSH3 gene in colon tumors when compared to adjacent mucosal tissues (P = 0.02). Interestingly, almost all MMR genes were differently expressed when localization of tumors was compared. In particular, colon tumors showed an up-regulation of EXO1, MSH2, MSH3, MSH6, and PMS2 genes in comparison to rectal tumors (P = 0.02). Expression levels of all MMR genes positively correlated between each other. The promoter methylation of MLH1 gene was observed in 9% of CRC tissues only. CONCLUSIONS: In our study, we have observed different pattern of MMR genes expression according to tumor localization. However, a lack of association between methylation in MMR genes and their corresponding expressions was noticed in this study, the relationship between these two aspects is worthy to be analyzed in larger population studies and in pre-malignant stages.

Novel mutations of the APC gene and genetic consequences of splicing mutations in the Czech FAP families.

Familial adenomatous polyposis (FAP) is an autosomal dominant syndrome with almost 100 % risk of colorectal cancer. The typical FAP is characterized by hundreds to thousands of colorectal adenomatous polyps and by extracolonic manifestations, later onset and lower number of polyps in colon is characteristic of an attenuated form (AFAP). We analyzed the APC gene for germline mutations in 90 FAP/AFAP patients. Mutation screening was performed using Denaturing Gradient Gel Electrophoresis. DNA fragments showing an aberrant electrophoretic banding pattern were sequenced. APC-mutation-negative probands were screened for large deletions of the APC gene using multiplex ligation dependent probe amplification. Analysis of mRNA variants followed in probands with possible splicing mutation by PCR amplification of target site flanking exons and sequencing the normal and aberrant products. We identified 30 germline variants among 36 unrelated probands including large deletions. Eleven APC variants detected last two years have not been reported yet. At all, fifteen of them are expected to cause errors in mRNA splicing. Analysis of mRNA in ten of these patients revealed exon skipping in seven cases, exonisation of intron in one of these as well, change of the amount of alternatively spliced product in one case, and no effect was found in three cases. In two of the patients, the biopsy of colon mucosa and polyp enabled us to examine the effect of the mutation on splicing pattern in colon cells directly. The comparison of alternative and standard transcript amount showed similar transcription pattern of exon 14 in control colon mucosa tissue (9 samples) as in 51 blood control samples.

Integration of a tick-borne encephalitis virus and Borrelia burgdorferi sensu lato into mountain ecosystems, following a shift in the altitudinal limit of distribution of their vector, Ixodes ricinus (Krkonose mountains, Czech Republic).

The altitudinal shift in the limit of Ixodes ricinus occurrence above the previously established altitude of 750 m above sea level has been monitored over the long-term (2002-2008) in the Krkonose Mts. (Giant Mts.), the highest in the Czech Republic, along two vertical transects in their eastern and central parts (600-1020 and 600-1270 m). Ticks were collected by flagging three times annually, and examined individually by PCR or RT-PCR for the presence of Borrelia burgdorferi sensu lato or tick-borne encephalitis virus (TBEV). A total of 5999 I. ricinus ticks were tested. TBEV RNA was detected in 26 ticks at up to 1140 m. Demonstration of TBEV in two larvae of I. ricinus indicates transovarial transmission. Similar infection rates in larvae and nymphs show vertical transmission in TBEV circulation to be very important under these mountain conditions. B. burgdorferi sensu stricto was found at up to 1040-1065 m, Borrelia garinii and Borrelia afzelii up to 1080-1140 m, and Borrelia valaisiana up to 1270 m. The total infection rates of nymphs and larvae were 7.3% and 2%, respectively. B. garinii was the most prevalent (37%), followed by B. afzelii (29%), B. burgdorferi s.s. (11%), and B. valaisiana (9%). Double to quadruple coinfections were detected in 32% of the infected ticks, most frequently B. garinii/B. afzelii. Predominance of B. garinii and B. valaisiana over B. afzelii suggests that small passerine birds moving on the ground are responsible for permanent local populations of I. ricinus in mountain localities with low numbers of small terrestrial mammals. The detection of B. burgdorferi sensu lato and TBEV in host-seeking larvae indicates an autochthonic infection. Upon analysis of the local climate we consider climate warming to be responsible for the spreading of ticks and tick-transmitted pathogens to higher altitudes.

Extension of Ixodes ricinus ticks and agents of tick-borne diseases to mountain areas in the Czech Republic.

Along with the shift of the hard tick Ixodes ricinus to higher altitudes observed in the Czech Republic a corresponding shift of tick-borne infections to higher altitudes has been expected. Therefore, I. ricinus ticks, mainly nymphs, were investigated for the presence of tick-borne viruses, tick-borne encephalitis (TBE), Tribec and Eyach, and the spirochaete Borrelia burgdorferi sensu lato in the Sumava and Krkonose Mountains (Czech Republic). The TBE virus and different genospecies of B. burgdorferi s.l. were detected by RT-PCR and PCR, respectively. TBE virus was detected in ticks at 620 and 720 m above sea level (a.s.l.), B. burgdorferi s.l. was detected in ticks up to 1065 m a.s.l. Four genospecies of B. burgdorferi s.l. were identified, B. afzelii, B. garinii, B. burgdorferi sensu stricto, and B. valaisiana. Some nymphs carried multiple Borrelia infections. The conditions of tick-borne agents' distribution and potential epidemiological consequences are discussed.