The role of VEGFR-2 genetic variation in breast cancer progression.

Abstract

Abstract Abstract #904 Background: Substantial laboratory and clinical data have demonstrated the critical role of angiogenesis in breast tumor progression. A significant correlation between vascular endothelial growth factor receptor-2 (VEGFR-2) expression and cell proliferation has been described in invasive breast carcinomas, suggesting that VEGF stimulates mammary cell growth through VEGFR-2. We sought to examine whether variability in VEGFR-2 expression and activation in tumors might be due to individual genetic variations, which may also play a role in response to anti-angiogenic therapy. To our knowledge, no study has correlated genetic variation in VEGFR-2 to expression and activity in primary breast tumors.
 Methods: DNA from 42 primary breast tumors was extracted from fresh frozen tissue. The core promoter, 5'-untranslated region (UTR), 3'-UTR, exons and intron-exon boundary regions of VEGFR-2 were sequenced for all tumors. Tissue microarrays were constructed, and tumor and paired normal breast tissue were stained with anti-VEGFR-2 antibody (Calbiochem). Microvessel density (MVD) was determined by immunohistochemical staining using a primary antibody against platelet endothelial cell adhesion molecule (anti-CD34, Novocastra). Semiquantitative analysis was performed independently by two pathologists. VEGFR-2 expression was correlated with genotype and MVD using the Mann-Whitney test. VEGFR-2 expression in normal and tumor tissue was compared using the Wilcoxon signed-rank test.
 Results: Two-thirds of tumors were from self-reported African Americans (AA), and the majority were ER positive. Twenty-three different single nucleotide polymorphisms (SNPs) were identified; ten were previously reported in dbSNP. Three of these SNPs were common (minor allele frequency >10%): one was located in the core promoter region and the other two were located in exons 7 and 11 (both non-synonymous SNPs). Using PolyPhen prediction software (http://genetics.bwh.harvard.edu/pph/), the two non-synonymous SNPs were predicted to affect protein function. Of the 23 different SNPs identified, 11 were only seen in tumors from AA and 3 were only observed in tumors from Caucasians. Thirty-six of the 42 tumors (86%) had at least one SNP. VEGFR-2 expression in tumor was significantly higher than in paired normal tissue (p=0.0002). VEGFR-2 expression was significantly lower in tumors with the AA genotype of the 4032 A/G core promoter SNP as compared to those with the AG and GG genotypes combined (p=0.02). VEGFR-2 expression was significantly associated with MVD in tumor tissues (p=0.04).
 Discussion: Our preliminary study suggests an association between genetic variations in the VEGFR-2 gene and protein expression in tumor tissue. Future work will examine the spectrum of these genetic variations in diverse populations and their potential role in predicting response to anti-angiogenic therapy.
 This study was funded by the University of Chicago Breast SPORE NCI P50 CA125183. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 904.