1. ¹Department of Pathology, GROW – School for Oncology and Developmental Biology, University Hospital Maastricht, PO Box 5800, 6202 AZ Maastricht, The Netherlands
2. ²Ontario Cancer Institute/PMH, Toronto, Canada
3. ³Department of Molecular Cell Biology, GROW – School for Oncology and Developmental Biology, University Hospital Maastricht, PO Box 5800, 6202 AZ Maastricht, The Netherlands

Correspondence: Dr AP de Bruïne, E-mail: adb@lpat.azm.nl

Received 14 April 2008; Revised 1 July 2008; Accepted 10 July 2008; Published online 19 August 2008.

Abstract

Stromal expression of hypoxia inducible factor 2 (HIF-2) and carbonic anhydrase 9 (CA9) are associated with a poorer prognosis in colorectal cancer (CRC). Tumour cell death, regulated by a hypoxic stromal microenvironment, could be of importance in this respect. Therefore, we correlated apoptosis, TP53 mutational status and BNIP3 promoter hypermethylation of CRC cells with HIF-2- and CA9-related poor outcome. In a series of 195 CRCs, TP53 mutations in exons 5–8 were analysed by direct sequencing, and promoter hypermethylation of BNIP3 was determined by methylation-specific PCR. Expressions of HIF-2, CA9, p53, BNIP3 and M30 were analysed immunohistochemically. Poorer survival of HIF-2 and CA9 stromal-positive CRCs was associated with wild-type TP53 (P=0.001 and P=0.0391), but not with BNIP3 methylation. Furthermore, apoptotic levels were independent of the TP53 status, but lower in unmethylated BNIP3 CRCs (P=0.004). It appears that wild-type TP53 in CRC cells favours the progression of tumours expressing markers for hypoxia in their stroma, rather than in the epithelial compartment. Preserved BNIP3 function in CRC cells lowers apoptosis, and may thus be involved in alternative cell death pathways, such as autophagic cell death. However, BNIP3 silencing in tumour cells does not impact on hypoxia-driven poorer prognosis.

These results suggest that the biology of CRC cells can be modified by alterations in the tumour microenvironment under conditions of tumour hypoxia.