Thromboxane synthase expression and correlation with VEGF and angiogenesis in non-small cell lung cancer

Background: Thromboxane synthase (TXS) metabolizes prostaglandin H2 into thromboxanes, which are biologically active on cancer cells. TXS over-expression has been reported in a range of cancers, and associated with angiogenesis and poor outcome. TXS has been identified as a potential therapeutic target in NSCLC. This study examines a link between TXS expression, angiogenesis, and survival in NSCLC. Methods: TXS and VEGF metabolite levels were measured in NSCLC serum samples (n = 46) by EIA. TXB₂ levels were correlated with VEGF. A 204-patient TMA was stained for TXS, VEGF, and CD-31 expression. Expression was correlated with a range of clinical parameters, including overall survival. TXS expression was correlated with VEGF and CD-31. Stable TXS clones were generated and the effect of overexpression on tumor growth and angiogenesis markers was examined in-vitro and in-vivo (xenograft mouse model). Results: Serum TXB₂ levels were correlated with VEGF (p < 0.05). TXS and VEGF were expressed to a varying degree in NSCLC tissue. TXS was associated with VEGF (p < 0.0001) and microvessel density (CD-31; p < 0.05). TXS and VEGF expression levels were higher in adenocarcinoma (p < 0.0001) and female patients (p < 0.05). Stable overexpression of TXS increased VEGF secretion in-vitro. While no significant association with patient survival was observed for either TXS or VEGF in our patient cohort, TXS overexpression significantly (p < 0.05) increased tumor growth in-vivo. TXS overexpression was also associated with higher levels of VEGF, microvessel density, and reduced apoptosis in xenograft tumors. Conclusion: TXS promotes tumor growth in-vivo in NSCLC, an effect which is at least partly mediated through increased tumor angiogenesis.