1. ¹Gray Cancer Institute, Mount Vernon Hospital, Northwood, Middlesex HA6 2RN, UK
2. ²Department of Radiotherapy, Mount Vernon Hospital, Northwood, Middlesex HA6 2RN, UK
3. ³Colorectal Cancer Unit, St Mark's Hospital, Harrow HA1 3UJ, UK
4. ⁴Karmanos Cancer Institute, Wayne State University, Detroit, MI 48201-2013, USA

Correspondence: Dr G Atkin, 70 Rosebery Rd, Muswell Hill, London N10 2LA, UK. E-mail: gkatkin@blueyonder.co.uk

Received 15 September 2005; Accepted 15 November 2005; Published online 13 December 2005.

Abstract

Delays in tissue fixation following tumour vascular clamping and extirpation may adversely affect subsequent protein and mRNA analysis. This study investigated the effect of surgically induced ischaemia in a xenograft model of a colorectal cancer on the expression of a range of prognostic, predictive, and hypoxic markers, with a particular emphasis on thymidylate synthase. Vascular occlusion of human tumour xenografts by D-shaped metal clamps permitted defined periods of tumour ischaemia. Alterations in protein expression were measured by immunohistochemistry and spectral imaging, and changes in mRNA were measured by reverse transcriptase–polymerase chain reaction. Thymidylate synthase expression decreased following vascular occlusion, and this correlated with cyclin A expression. A similar reduction in dihydropyrimidine dehydrogenase was also seen. There were significant changes in the expression of several hypoxic markers, with carbonic anhydrase-9 showing the greatest response. Gene transcriptional levels were also noted to change following tumour clamping. In this xenograft model, surgically induced tumour ischaemia considerably altered the gene expression profiles of several prognostic and hypoxic markers, suggesting that the degree of tumour ischaemia should be minimised prior to tissue fixation.