Overexpression of thymidylate synthase (TYMS) is associated with aggressive tumor features and early PSA recurrence in prostate cancer

Thymidylate synthase (TYMS) plays a role in DNA synthesis and is a target for 5-fluorouracil. In this study TYMS was analyzed by immunohistochemistry on a tissue microarray containing 11,152 prostate cancers. TYMS expression was higher in neoplastic than in normal prostate epithelium and was detectable in 72.9% of 10,223 interpretable cancers. It was considered strong in 21.9%, moderate in 33.4% and weak in 17.6% of tumors. TYMS overexpression was associated with deletions at 5q21 (p < 0.0001), 6q15 (p < 0.0001) and 3p13 (p = 0.0083) and gradually increased with the total number of these deletions present in the respective cancer sample (p < 0.0001). TYMS expression was unrelated to PTEN deletions (p = 0.9535) but tightly linked to high Gleason grade, advanced pathological tumor stage and early PSA recurrence (p < 0.0001). The prognostic value of TYMS was independent from the ERG status and deletions at 3p13, 5q21, and 6q15. In multivariate analyses the prognostic role of TYMS expression was independent of Gleason grade, pT stage, preoperative PSA, pN stage, or resection margins. TYMS expression analysis might result in clinically useful information in prostate cancer. The striking link to some but not all chromosomal aberrations might suggest a mechanistical link with specific types of DNA damage.