A mutation in POLE predisposing to a multi-tumour phenotype

Somatic mutations in the POLE gene encoding the catalytic subunit of DNA polymerase epsilon have been found in sporadic colorectal cancers (CRCs) and are most likely of importance in tumour development and/or progression. Recently, families with dominantly inherited colorectal adenomas and colorectal cancer were shown to have a causative heterozygous germline mutation in the proofreading exonuclease domain of POLE. The highly penetrant mutation was associated with predisposition to CRC only and no extra-colonic tumours were observed. We have identified a mutation in a large family in which the carriers not only developed CRC, they also demonstrate a highly penetrant predisposition to extra-intestinal tumours such as ovarian, endometrial and brain tumours. The mutation, NM_006231.2:c.1089C>A, p.Asn363Lys, also located in the proofreading exonuclease domain is directly involved in DNA binding. Theoretical prediction of the amino acid substitution suggests a profound effect of the substrate binding capability and a more severe impairment of the catalytic activity compared to the previously reported germline mutation. A possible genotype to phenotype correlation for deleterious mutations in POLE might exist that needs to be considered in the follow-up of mutation carriers

Expanding the genotype-phenotype spectrum in hereditary colorectal cancer by gene panel testing

Hereditary syndromes causing colorectal cancer include both polyposis and non-polyposis syndromes. Overlapping phenotypes between the syndromes have been recognized and this make targeted molecular testing for single genes less favorable, instead there is a gaining interest for multi-gene panel-based approaches detecting both SNVs, indels and CNVs in the same assay. We applied a panel including 19 CRC susceptibility genes to 91 individuals of six phenotypic subgroups. Targeted NGS-based sequencing of the whole gene regions including introns of the 19 genes was used. The individuals had a family history of CRC or had a phenotype consistent with a known CRC syndrome. The purpose of the study was to demonstrate the diagnostic difficulties linked to genotype-phenotype diversity and the benefits of using a gene panel. Pathogenicity classification was carried out on 46 detected variants. In total we detected sixteen pathogenic or likely pathogenic variants and 30 variants of unknown clinical significance. Four of the pathogenic or likely pathogenic variants were found in BMPR1A in patients with unexplained familial adenomatous polyposis or atypical adenomatous polyposis, which extends the genotype-phenotype spectrum for this gene. Nine patients had more than one variant remaining after the filtration, including three with truncating mutations in BMPR1A, PMS2 and AXIN2. CNVs were found in three patients, in upstream regions of SMAD4, MSH3 and CTNNB1, and one additional individual harbored a 24.2 kb duplication in CDH1 intron1

Serum Calcium to Phosphorous (Ca/P) Ratio is a simple, inexpensive, and accurate tool in the diagnosis of primary hyperparathyroidism

Primary hyperparathyroidism (PHPT) diagnosis is challenging and is based on serum calcium (Ca) and parathyroid hormone (PTH). Because serum Ca and phosphorous (P) are inversely related in PHPT, we investigated the diagnostic value of the serum Ca/P ratio in the diagnosis of PHPT. We report a single-center, case-controlled, retrospective study including 97 patients with documented PHPT and compared them with those of 96 controls (C). The main outcome measures were: serum PTH, 25-OH vitamin D, Ca, P, albumin, and creatinine. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of the serum Ca/P ratio were calculated. The results were verified using an independent, anonymous set of data extracted from a laboratory database containing over 900 million entries. A total of 35 (36.1%) PHPT patients had normocalcemic PHPT (NCHPT). Ca and PTH were significantly higher in PHPT than in C (p < 0.0001). P was significantly lower in PHPT than in C (p < 0.0001). The Ca/P ratio was significantly higher in PHPT than in C (p < 0.0001). Receiver-operating characteristic (ROC) curves analyses identified a cutoff of 2.71 (3.5 if Ca and P are expressed in mg/dL) for Ca/P ratio with a sensitivity and specificity of 86% and 87%, respectively (p < 0.0001), confirmed by the independent, big data approach. In conclusion, Ca/P is a valuable tool for the diagnosis of PHPT and is of superior value compared to serum Ca alone, especially in NCPHT. Because Ca/P is simple, inexpensive, and easily accessible worldwide, this ratio is useful for PHPT diagnosis, especially in laboratory/medical settings relying on limited resources, such as low-income countries. © 2017 The Authors. JBMR Plus is published by Wiley Periodicals, Inc. on behalf of the American Society for Bone and Mineral Research

Relationship between apolipoprotein(a) size polymorphism and coronary heart disease in overweight subjects

BACKGROUND: Overweight is associated with an increased cardiovascular risk which is only partially explained by conventional risk factors. The objective of this study was to evaluate lipoprotein(a) [Lp(a)] plasma levels and apolipoprotein(a) [apo(a)] phenotypes in relation to coronary heart disease (CHD) in overweight subjects. METHODS: A total of 275 overweight (BMI ≥ 27 kg/m(2)) subjects, of which 155 had experienced a CHD event, 337 normal weight subjects with prior CHD and 103 CHD-free normal weight subjects were enrolled in the study. Lp(a) levels were determined by an ELISA technique and apo(a) isoforms were detected by a high-resolution immunoblotting method. RESULTS: Lp(a) levels were similar in the three study groups. Overweight subjects with CHD had Lp(a) concentrations significantly higher than those without [median (interquartile range): 20 (5–50.3) versus 12.6 (2.6–38.6) mg/dl, P < 0.05]. Furthermore, overweight subjects with CHD showed a higher prevalence of low molecular weight apo(a) isoforms than those without (55.5% versus 40.8%, P < 0.05) and with respect to the control group (55.5% versus 39.8%, P < 0.05). Stepwise regression analysis showed that apo(a) phenotypes, but not Lp(a) levels, entered the model as significant independent predictors of CHD in overweight subjects. CONCLUSIONS: Our data indicate that small-sized apo(a) isoforms are associated with CHD in overweight subjects. The characterization of apo(a) phenotypes might serve as a reliable biomarker to better assess the overall CHD risk of each subject with elevated BMI, leading to more intensive treatment of modifiable cardiovascular risk factors

Lipoprotein(a) in cardiovascular disease

The atherosclerotic process is continuous and starts early in life. Risk factors for atherosclerosis include hyperlipidemia, hypertension, smoking and diabetes mellitus. Fatty streaks characterised by lipid-laden macrophages are early signs of atherosclerosis. Binding of LowDensityLipoproteins(LDL) to proteoglycans is believed to be one of the first steps in atherosclerosis. After many years the plaques are more complex with aggregations of lipids, extracellular matrix, and necrotic cells with variable content of inflammatory cells. The etiology of atherosclerosis is complex and multifactorial. Several new risk factors have been studied recently. On such factor may be lipoprotein(a)(Lp(a)). Lp(a) has been associated to cardiovascular disease in several studies. Lp(a) is an LDL-like particle with an apolipoprotein(a) part attached to apoB by a disulfide bridge.The regulation of serum levels of Lp(a) has been studied in this thesis. It has earlier been shown that Growth Hormone increases the levels of Lp(a). It has been speculated that this effect could be mediated by Insulin-like Growth Factor-1(IGF-1). Effects of IGF-1 treatment were tested in the present study during a two weeks period. The results demonstrate that IGF-1 treatment resulted in decreased levels of Lp(a)(-18.5%). Lowered levels of cholesterol and triglycerides were also seen. We also studied the effects of N-acetylcysteine treatment. No effect of N-acetylcysteine treatment on Lp(a) was seen during treatment. There was a reduction of homocysteine, cysteinylglycine and glycine as a response to the treatment. The interactions of Lp(a) and LDL with extracellular matrix have been investigated. In studies with human arterial smooth muscle cell derived extracellular matrix we saw an increased binding of 125I-LDL in the presence of Lp(a). This binding was reduced after treatment of the matrix with chondroitinase ABC, implying an involvement of proteoglycans in the interaction. In addition the interaction of 125I-LDL with matrix was stronger in the presence of Lp(a). In a population with coronary heart disease (n=964) Lp(a)levels and apo(a) isoforms was studied as a prognostic factor during a twelve years follow-up.A total of 363 patients died during follow-up. The smallest isoform of apo(a) was associated with a two-fold increase in risk. High levels of lipoprotein(a) were not associated with increased risk. In women, but not in men the risk decreased with increasing molecular weight of the apo(a) isoforms. These results support the endocrine regulation of serum Lp(a) levels, specifically a reduction by IGF-1 was seen. Lp(a) increases the binding of LDL to human arterial smooth muscle cell derived extracellular matrix in vitro. More LDL particles are bound in the presence of Lp(a) and the interaction is stronger. Apo(a) isoforms but not Lp(a) levels were found to be risk factors in patients with CHD, especially among women. These findings emphasize the importance of a gender-specific analysis of risk factors for CHD