Human apolipoprotein CI (apoC1) gene locus: DraI dimorphic site

Apolipoprotein C1 (APOC1): A Novel Diagnostic and Prognostic Biomarker for Clear Cell Renal Cell Carcinoma

Background: Apolipoprotein C1 (APOC1) has been proved to play a critical role in gastric, breast, lung, and pancreatic cancer. However, the relationship between APOC1 and urinary tumors remains unclear. This study aimed to assess the diagnostic and prognostic value of APOC1 in urinary tumors.

Methods: We performed a pan analysis of APOC1 mRNA expression in urinary cancer using the Gene Expression Profiling Interactive Analysis (GEPIA) database. To further investigate the prognostic value of APOC1 expression in urinary cancers, the Kaplan-Meier plotter database was used. Furthermore, we collected the tumor and adjacent normal samples of 32 ccRCC patients to perform qRT-PCR and western blotting assays. A total of 72 cases with ccRCC were analyzed using tissue microarrays (TMAs).

Results: Our results based on Kaplan-Meier plotter database indicated that a high expression of APOC1 may lead to poor overall survival (OS, p = 0.0019) in patients with ccRCC. Furthermore, the cancer stages and tumor grade of ccRCC appeared to be strongly linked with APOC1 expression according to UALCAN database. Hence, we reached a preliminary conclusion that APOC1 may play a key role in the tumorigenesis and progression of ccRCC. Furthermore, the Kaplan-Meier survival curve analyses of 72 clinical patients indicated that high expression of APOC1 was associated with poor progression-free survival (PFS, p = 0.007) and OS (p = 0.022). In addition, univariate Cox regression analysis confirmed the significant relationship between APOC1 expression and survival (p = 0.038). The TMAs analysis in combination with the patients' clinicopathological features was also performed. The expression of APOC1 was found to be significantly correlated with the tumor size (p = 0.018) and histological grade (p = 0.016).

Conclusions: In conclusion, the findings of our study suggest that APOC1 may serve as a novel diagnostic and prognostic biomarker for ccRCC. Further evidence on the mechanism of APOC1 promoting tumor progression may transform it to a new therapeutic target for the treatment of ccRCC.

APOC1 T45S polymorphism is associated with reduced obesity indices and lower plasma concentrations of leptin and apolipoprotein C-I in aboriginal Canadians

Apolipoprotein (apo) C-I is a constituent of chylomicrons, very low density lipoprotein, and high density lipoprotein. The role of apo C-I in human metabolism is incompletely defined. We took advantage of a naturally occurring amino acid polymorphism that is present in aboriginal North Americans, namely apo C-I T45S. We assessed the hypothesis that metabolic traits, including obesity-related and lipoprotein-related traits, would differ between carriers and noncarriers of apo C-I T45S. A genotyping assay was developed for APOC1 T45S and genotypes were determined in a sample of 410 Canadian Oji-Cree subjects. The allele frequency of the apo C-I S45 allele was approximately 8% in this sample. We observed the apo C-I S45 allele was significantly associated with 1) lower percent body fat (P < 0.05), 2) lower waist circumference (P = 0.058), 3) lower serum leptin levels (P < 0.05), and 4) lower plasma apo C-I levels (P < 0.0001), using a newly developed ELISA-based method. Taken together, these results suggest that at the whole human phenotype level, apo C-I is associated with the complex metabolic trait of obesity as well as with serum leptin levels.

Variable expression of familial dysbetalipoproteinemia in apolipoprotein E*2 (Lys146-->Gln) Allele carriers

Genetic and biochemical studies were carried out in 96 relatives of six independently ascertained probands with familial dysbetalipoproteinemia (FD) carrying the APOE*2 (Lys146-->Gln) allele. Compared to noncarriers, the 40 heterozygous APOE*2 (Lys146-->Gln) allele carriers exhibited markedly increased mean levels of cholesterol and triglyceride in the very low density lipoproteins (VLDL) (1.89 +/- 0.37 vs 0.30 +/- 0.27 and 1.86 +/- 0.37 vs 0.68 +/- 0.27 mmol/liter, respectively) and plasma apolipoprotein (apo) E levels (28.1 +/- 1.6 vs 4.6 +/- 1.1 mg/dl), which is characteristic for FD. By means of a pedigree-based maximum likelihood method we calculated that carrier-status accounted for 57% and 71%, respectively, of the total variance of the ratio (VLDL + IDL)-cholesterol/plasma triglyceride and plasma apoE levels. APOE*2 (Lys146-->Gln) and APOE*3-Leiden allele carriers were found to differ significantly in: (a) plasma apoE levels, (b) in the amounts of triglycerides in the VLDL and VLDL + IDL fraction, and (c) in the amount of cholesterol in the VLDL and VLDL + IDL fraction relative to the amount of triglyceride in these fractions. In the APOE*2 (Lys146-->Gln) allele carriers the VLDL and VLDL + IDL fraction is relatively rich in triglycerides as compared with that in APOE*3-Leiden carriers. We hypothesize that these two rare mutations of apoE both lead to dominantly inherited forms of FD along different underlying metabolic defects.

Association analysis of lipid levels and apolipoprotein restriction fragment length polymorphisms

We have analyzed the correlation between restriction site variants (RFLPs; restriction fragment length polymorphisms) of the apolipoprotein AI, AII, B, CI and CII genes and serum lipid levels in a sample of male Norwegians. We find no significant association between any of the RFLPs and lipid levels.

Linkage relationships of the apolipoprotein C1 gene and a cytochrome P450 gene (CYP2A) to myotonic dystrophy

We have studied the genetic linkage of two markers, the apolipoprotein C1 (APOC1) gene and a cytochrome P450 (CYP2A) gene, in relation to the gene for myotonic dystrophy (DM). A peak lod score of 9.29 at 2 cM was observed for APOC1-DM, with a lod score of 8.55 at 4 cM for CYP2A-DM. These two markers also show close linkage to each other (theta max = 0.05, Zmax = 9.09). From examination of the genotypes of the recombinant individuals, CYP2A appears to map proximal to DM because in one recombinant individual CYP2A, APOC2 and CKMM had all recombined with DM. Evidence from another CYP2A-DM recombinant individual places CYP2A proximal to APOC2 and CKMM. Localisation of CYP2A on a panel of somatic cell hybrids also suggests that it is proximal to DM and APOC2/C1/E gene cluster.

Myotonia congenita (Thomsen's disease) excluded from the region of the myotonic dystrophy locus on chromosome 19

Linkage analysis has been carried out in six German families with autosomal dominantly inherited myotonia congenita (Thomsen's disease) using five chromosome 19 markers known to be linked to the gene for myotonic dystrophy (DM). Two of the markers, APOC1 and APOC2, are tightly linked to DM. Close linkage between these markers and myotonia congenita (MC) has been excluded to a distance of 9 cM (z = -2.158). These data support the clinical suggestion that MC and DM are non-allelic disorders.

Tight linkage between myotonic dystrophy and apolipoprotein E genes revealed with allele-specific oligonucleotides

In 16 families with myotonic dystrophy (DM) a novel approach based on use of allele-specific oligonucleotides has been employed to study the linkage relationship between the apolipoprotein E (APOE) gene and DM. Synthetic oligonucleotides, designed to discriminate between APOE alleles epsilon 3 and epsilon 4, enabled us to distinguish heterozygous carriers in a hybridization assay. In a subset of families, the relevant segment of the APOE gene was enzymatically amplified to increase the sensitivity of the method. For DM and APOE, a maximum lod score (zmax of 7.47 was obtained at a recombination frequency (theta) of 0.047 (male theta = female theta). No recombination (maximum lod score of 5.61 at theta = 0.0) was found between APOE and the apolipoprotein CII (APOC2) gene. These results suggest that, in addition to APOC2, APOE is a useful marker for presymptomatic DM diagnosis.

DNA polymorphisms of the apolipoprotein genes--their use in the investigation of the genetic component of hyperlipidaemia and atherosclerosis

DNA probes for all eight of the major apolipoprotein genes are now available. The chromosomal location, the basic structure and in many cases the nucleotide sequences of the normal genes are known. Common DNA polymorphisms of all of the genes have been detected. These have been been used in a number of ways to investigate rare inherited defects of the apolipoprotein genes, to study the potential involvement of different variants of the genes in the development of hyperlipidaemia in patients, and to investigate the contribution of common variation in these genes in the determination of serum lipid levels in the normal population.