The haplotype of three polymorphisms in the SATB1 promoter region impacts survival in breast cancer patients

Special AT-rich sequence binding protein 1 (SATB1) has regulatory effects on gene expression and appears to play an important role in tumor progression. The present study screened the promoter region of the SATB1 gene for polymorphisms, evaluated the corresponding haplotypes regarding alterations in promoter activity in vitro and analyzed the impact of these haplotypes on the clinical course of breast cancer patients. A cohort of 241 female Caucasian breast cancer patients who had been treated was enrolled in this retrospective analysis. The median follow-up time was 93 months (range, 4-155 months). PCR products from DNA of 10 healthy, unrelated volunteers were analyzed to identify new polymorphisms within the promoter region. Genotyping was conducted using restriction fragment length polymorphism and pyrosequencing. PCR constructs with the respective alleles from the four most frequent haplotypes were cloned into the vector pGEM®-T Easy and then transferred into the luc2-containing reporter vector pGl 4.10® for transfection of HEK293 cells. The pGl 4.73® vector, containing hRluc, was used for normalizing the transfection rates. Sequencing the region -3807 to -2828 bp upstream of ATG from ten healthy blood donors, three single nucleotide polymorphisms consisting of base exchanges were identified: -3600T>C, -3363A>G and -2984C>T. The SATB1 -3600T/-3363A/-2984C haplotype had lower promoter activity than all other constructs in vitro and exhibited a significant association with nodal status (P<0.05). Kaplan-Meier survival analysis revealed significantly improved overall survival for homozygous SATB1 -3600T/-3363A/-2984C haplotype carriers compared with heterozygous carriers or the other haplotypes (P=0.033). The SATB1 -3600T/-3363A/-2984C haplotype is associated with lower promoter activity and appears to impact upon survival in breast cancer patients.