CD36 - a plausible modifier of disease phenotype in familial adenomatous polyposis

Role of CD36 rs1761667 AA genotype in the expression of inflammatory cytokines and Parkinson's disease progression: A case-control study in a northern Han Chinese population

OBJECTIVE

This study aimed to investigate the effect of CD36 rs1761667 gene polymorphisms on the expression of CD36 and inflammatory cytokines and the progression of Parkinson's disease (PD).

METHODS

A total of 138 patients with PD (60 men and 78 women) and 132 healthy controls (48 men and 84 women) from a northern Han Chinese population were enrolled in this case-control study. Polymerase chain reaction-restriction fragment length polymorphism was used to detect the CD36 rs1761667 genotype. An enzyme-linked immunosorbent assay was used to determine the expression of CD36, interleukin (IL)-6, IL-1β, and tumor necrosis factor (TNF)-α in the plasma.

RESULTS

The frequency of the rs1761667 AA genotype was significantly higher in patients with PD than that in healthy controls, suggesting AA genotype to be a risk factor for PD. When compared with those in healthy controls, CD36 levels were significantly lower in patients with PD, whereas IL-6, IL-1β, and TNF-α levels were significantly higher in patients with PD. Furthermore, GA and AA carriers with PD showed lower levels of CD36, and GG, GA, and AA carriers showed higher levels of IL-6, IL-1β, and TNF-α than those in healthy controls. In the PD patient group, AA and GA carriers had lower expression levels of CD36 than GG carriers did, and CD36 levels were lower in AA carriers than in GA carriers. Conversely, AA carriers had elevated expression levels of IL-6 compared with that of GG and GA carriers. Logistic regression analysis revealed that IL-6, IL-1β, and TNF-α levels were risk factors for PD in a northern Han Chinese population.

CONCLUSION

The CD36 rs1761667 AA genotype may increase susceptibility to PD and the expression of inflammatory cytokines.

CD36 polymorphisms and the age of disease onset in patients with pathogenic variants within the mutation cluster region of APC

Background

Familial adenomatous polyposis (FAP) is an autosomal dominant condition that predisposes patients to colorectal cancer. FAP is the result of a loss of APC function due to germline pathogenic variants disrupting gene expression. Genotype-phenotype correlations are described for FAP. For example attenuated forms of the disease are associated with pathogenic variants at the 5’ and 3’ ends of APC whilst severe forms of the disease appear to be linked to variants occurring in the mutation cluster region (MCR) of the gene. Variants occurring in the MCR are phenotypically associated with hundreds to thousands of adenomas carpeting the colon and rectum and patients harbouring changes in this region have a high propensity to develop colorectal cancer. Not all patients who carry pathogenic variants in this region have severe disease which may be a result of environmental factors. Alternatively, phenotypic variation observed in these patients could be due to modifier genes that either promote or inhibit disease expression. Mouse models of FAP have provided several plausible candidate modifier genes, but very few of these have survived scrutiny. One such genetic modifier that appears to be associated with disease expression is CD36. We previously reported a weak association between a polymorphism in CD36 and a later age of disease onset on a relatively small FAP patient cohort.

Methods

In the current study, we enlarged the FAP cohort. 395 patients all carrying pathogenic variants in APC were tested against three CD36 Single Nucleotide Polymorphisms (SNP)s (rs1049673, rs1761667 rs1984112), to determine if any of them were associated with differences in the age of disease expression.

Results

Overall, there appeared to be a statistically significant difference in the age of disease onset between carriers of the variant rs1984112 and wildtype. Furthermore, test equality of survivor functions for each SNP and mutation group suggested an interaction in the Log Rank, Wilcoxon, and Tarone-Ware methods for rs1049673, rs1761667, and rs1984112, thereby supporting the notion that CD36 modifies disease expression.

Conclusions

This study supports and strengthens our previous findings concerning CD36 and an association with disease onset in FAP, AFAP and FAP-MCR affected individuals. Knowledge about the role CD36 in adenoma development may provide greater insight into the development of colorectal cancer.

Advances in Identification of Susceptibility Gene Defects of Hereditary Colorectal Cancer

Colorectal cancer (CRC) is a common malignant tumor of the digestive system worldwide, associated with hereditary genetic features. CRC with a Mendelian genetic predisposition accounts for approximately 5-10% of total CRC cases, mainly caused by a single germline mutation of a CRC susceptibility gene. The main subtypes of hereditary CRC are hereditary non-polyposis colorectal cancer (HNPCC) and familial adenomatous polyposis (FAP). With the rapid development of genetic testing methods, especially next-generation sequencing technology, multiple genes have now been confirmed to be pathogenic, including DNA repair or DNA mismatch repair genes such as APC, MLH1, and MSH2. Since familial CRC patients have poor clinical outcomes, timely clinical diagnosis and mutation screening of susceptibility genes will aid clinicians in establishing appropriate risk assessment and treatment interventions at a personal level. Here, we systematically summarize the susceptibility genes identified to date and the potential pathogenic mechanism of HNPCC and FAP development. Moreover, clinical recommendations for susceptibility gene screening, diagnosis, and treatment of HNPCC and FAP are discussed.