ORIGINAL ARTICLE

Thymidylate synthase protein expression and activity are related to the cell proliferation rate in human cancer cell lines

M Derenzini¹, L Montanaro¹, D Treré¹, A Chillà¹, P L Tazzari², F Dall’Olio¹ and D Öfner³

¹ Department of Experimental Pathology, University of Bologna, Via S. Giacomo 14, 40126, Bologna, Italy
² Department of Clinical Pathology and Microbiology, S. Orsola Hospital, Via Massarenti 9, 40138 Bologna, Italy
³ Department of Surgery, University Hospital, Anichstraße 35, 6020 Innsbruck, Austria

Correspondence to:
Correspondence to:
Professor M Derenzini, Dipartimento di Patologia Sperimentale, Via San Giacomo 14, 40126 Bologna, Italy;
derenzin{at}med.unibo.it

Aims: To ascertain whether the expression and enzyme activity of thymidylate synthase (TS) are related to the rapidity of cell proliferation in human cancer cell lines.

Methods: Ten asynchronously growing human cancer cell lines of different origin were used, characterised by various doubling times. TS expression was evaluated by western blot analysis using the TS 106 monoclonal antibody. TS activity was determined by the enzyme catalytic assay. The quantitative variation of TS in different phases of the cell cycle was investigated using two parameter flow cytometry for the TS protein and DNA analysis. The number of proliferating cells was evaluated by Ki67 immunostaining.

Results: TS expression and activity were significantly related to each other (r = 0.765; p = 0.01) and to the cell doubling time (r = -0.899; p < 0.001 and r = -0.919; p < 0.001, respectively). Ki67 immunolabelling showed no association between the number of cycling cells and TS protein expression and activity. Two parameter flow cytometry indicated that differences of TS expression in the cell lines were not related to the cell cycle phases or to the proportion of S phase cells.

Conclusions: These results show that the expression and activity of the TS protein in asynchronously growing cancer cells are significantly related to the cell doubling time; the faster the cell proliferation, the greater the expression and activity of TS. These findings could explain why TS values are of prognostic value per se and why tumours with high TS expression benefit more from chemotherapy.

Keywords: cancer cell lines; cell doubling time; thymidylate synthase; 5-FU chemotherapy

Abbreviations: BSA, bovine serum albumin; 5-FU, 5-fluorouracil; LI, labelling index; PBS, phosphate buffered saline; SDS-PAGE, sodium dodecyl sulfate polyacrylamide gel electrophoresis; TS, thymidylate synthase

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

• Ricart, A. D., Berlin, J. D., Papadopoulos, K. P., Syed, S., Drolet, D. W., Quaratino-Baker, C., Horan, J., Chick, J., Vermeulen, W., Tolcher, A. W., Rowinsky, E. K., Rothenberg, M. L. (2008). Phase I, Pharmacokinetic and Biological Correlative Study of OSI-7904L, a Novel Liposomal Thymidylate Synthase Inhibitor, and Cisplatin in Patients with Solid Tumors. Clin. Cancer Res. 14: 7947-7955 [Abstract] [Full Text]  
• Chi, K.-H., Wang, H.-E., Wang, Y.-S., Chou, S.-L., Yu, H.-M., Tseng, Y.-H., Hwang, I.-M., Lui, W.-Y. (2004). Antisense Thymidylate Synthase Electrogene Transfer to Increase Uptake of Radiolabeled Iododeoxyuridine in a Murine Model. JNM 45: 478-484 [Abstract] [Full Text]