Correlation between selected XRCC2, XRCC3 and RAD51 gene polymorphisms and primary breast cancer in women in Pakistan

Genetic polymorphisms in homologous recombination repair genes cause an abnormal development of cancerous cells. In the present study we evaluated the possibility of breast cancer association with single nucleotide polymorphisms of RAD51, XRCC2 and XRCC3 genes. Polymorphisms selected in this study were RAD51 135G/C, XRCC2 Arg188His; and XRCC3 Thr241Met. Each polymorphism was genotyped using Polymerase chain reaction-restriction fragment length polymorphism in study cohort of 306 females (156 breast cancer patients and 150 controls). We observed that heterozygous variant genotype (GC) of RAD51 135 G/C polymorphism was associated with a significantly (OR=2.70; 95%CI (0.63-1.79); p<0.03) increased risk of breast cancer. In case of the XRCC3 gene we observed that frequency of heterozygous (OR=2.88; 95%CI (1.02-8.14); p<0.02) and homozygous (OR=1.46; 95%CI (0.89-2.40); p<0.04) genotype of Thr241Met polymorphism were significantly higher in breast cancer patients. For the Arg188His polymorphism of XRCC2, ~2fold increase in breast cancer risk (OR=1.6, 95%CI = 0.73-3.50) was associated with GA genotype with a p value for trend of 0.03. Our results suggest that the 135G/C polymorphism of the RAD51, Thr241Met polymorphism of XRCC3 and Arg188His polymorphism of XRCC2 can be independent markers of breast cancer risk in Pakistan.

Upregulation of RAD51 expression is associated with progression of thyroid carcinoma

AIMS

RAD51 participates in homologous recombination repair (HRR) of double-stranded DNA breaks (DSBs) which may cause genomic instability and cancer. The aim of this study was to investigate RAD51 gene expression at transcriptional and translational levels to measure mRNA and protein level and to correlate its relationship with proliferation marker, Ki67 in thyroid cancer patients. This study also explored correlation of these genes with different clinicopathological parameters of the study cohort by Spearman's rank correlation coefficient.

METHODS

Quantitative real time polymerase chain reaction (qRT-PCR) and immunohistochemistry were used to detect mRNA transcript levels and protein expression of RAD51 and Ki67 in 102 cases of thyroid cancer tissues and equal number of uninvolved healthy thyroid tissue controls.

RESULTS

Data showed that expression for both RAD51 and Ki67 was significantly increased in thyroid cancer (p<0.001). High RAD51 and Ki67 expression was associated with later stages, poor tissue differentiation, large tumor size, positive lymph node metastasis and distant metastasis. The correlation analysis demonstrated a strong positive correlation (r=0.461) between RAD51 and Ki67 on mRNA level and on protein level (r=0.866). Strong correlation was observed between clinicopathological characteristics and selected molecules.

CONCLUSION

The present study concluded that upregulation of RAD51 and overexpression of Ki67 may be associated with the progression of thyroid cancer.