Background VEGF receptor-2 (VEGFR-2) is a key receptor in VEGF-mediated angiogenesis. It plays a significant role in tumor growth and development of metastases. A few studies suggested the angiogenic feature of bronchioalveolar cell carcinoma (BAC), a rare subtype of adenocarcinoma. However the biology of VEGFR-2 in BAC has not been clearly characterized, probably due to its rarity. We sought to determine whether differences in VEGFR-2 expression and microvessel density (MVD) in adenocarcinoma with BAC features (AWBF) might be due to heritable genetic variation in the VEGFR-2 gene. Differences in VEGFR-2 expression and MVD between the pure BAC component of tumor and AWBF, and their comparison with adjacent normal tissue, were also investigated.

Methods DNA was extracted from 46 formalin-fixed paraffin embedded AWBF tissues. Four single-nucleotide polymorphisms (SNPs) and four in/dels were genotyped in all tumors. Tissue microarrays (TMAs) were constructed with tumor tissue (pure BAC component and AWBF component for each tumor) and paired adjacent normal lung tissue. TMAs were stained with anti-VEGFR-2 and anti-phosphorylated-VEGFR-2 (pVEGFR-2) antibodies (scoring: 0-9). MVD was determined by staining with an antibody against CD105, and 95% of the samples had either diffused high or focal high staining.

Results The −271G>A genotype showed a clear gene-dosage effect on pVEGFR-2 expression (GG>GA>AA, p=0.04, linear trend analysis) in AWBF but not in BAC (p>0.1). The −271G>A genotype does not affect the MVD in both BAC and AWBF (linear trend analysis and Kruskal-Wallis, p>0.1). The other SNPs and in/dels did not show any significant association with VEGFR-2, pVEGFR-2, and MVD (p>0.1). VEGFR-2 and pVEGFR-2 expression in tumor (AWBF and pure BAC) was more than 10 times higher the paired normal tissue (p<0.001, Wilcoxon matched pairs test). A trend for higher VEGFR-2 expression in AWBF compared to pure BAC (mean score 4.2 vs. 3.8, p=0.08, Wilcoxon matched pairs test) was observed, while no difference was observed for pVEGFR-2 (p>0.1). For MVD, although the proportion of diffused high staining was higher in BAC (60%) vs. AWBF (47%), this difference is not statistically significant (p>0.1, Fisher's exact test).

Discussion Our study shows that heritable gene variation of −271G>A in VEGFR-2 might reduce the expression of VEGFR-2 in AWBF. This is consistent with the effect of −271G>A in a luciferase assay (Ye et al., AACR 2007), as well as its effect on VEGFR-2 and pVEGFR-2 staining in breast cancer (Cerri et al., SABCS 2009, abstract #904). Although our data are suggestive of different pattern of angiogenesis between pure BAC and AWBF, our sample size is too small to draw any definitive conclusions. Additional studies are ongoing to replicate these findings that will establish the role of genetic variation as a determinant of VEGFR-2 expression in BAC, and the biology of angiogenesis in this rare tumor.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2176.