Immunohistochemical localization of group II phospholipase A2 in the tumours and mucosa of the colon and rectum

Background: Group II phospholipase A2(PLA2) is an enzyme important in malignant transformation and in the invasion process of malignant cells. The aim of the present study was to investigate the expression of group II PLA2in the cancers of the colorectum, peritumoural mucosa and in the mucosa distant from the tumour. Methods: Resection specimens from 57 patients with colorectal carcinoma (caecum 10, ascending 10, transverse 10, sigmoid colon nine, and rectum 18) were analysed immunohistochemically. Histological slides from paraffin blocks were stained by the human monoclonal group II PLA2antibody («Upstate Biotechnology», Lake Placid, NY 12946, USA. Antibody Class: IgG1k. Immunogen: HPC purifed human sperm phospholipase A2– 14 kDa enzyme) using the standard DAKO peroxidase-labelled streptavidin–biotin method by TechMate 500 stainer. Group II PLA2expression was evaluated semi-quantitatively according to the extensivity and intensivity of the positive cells. For statistical evaluation the Kruskal–Wallis one way analysis of variance on ranks and the Mann–Whitney rank sum tests were used. Results: The highest expression of group II PLA2was found in the peritumoural mucosa (median 4.00), much lower in the mucosa distal from the tumour (median 0.70) and almost no activity in the tumour itself (median 0.00), all differences were statistically significant (all pairwise multiple comparison procedures – Dunnʹs Method P<0.05). The expression of group II PLA2was higher in the left colon and rectum than in the right colon (Mann–Whitney rank sum test P<0.05). Conclusions: Our results suggest that there is variation of the group II PLA2expression throughout the mucosa and tumours of the colorectum, which might reflect the progression of neoplastic process.