Expression of cyclooxygenase-2 (COX-2) in colorectal carcinoma in an indigenous African population of Kano, Nigeria.

Abstract

Background: cyclooxygenases-2 (COX-2) over-expression has been noticed in colorectal cancers (CRCs) with adverse outcomes, serving as a potential marker for prognosis, targeted therapy and as a window in CRC prevention. Unfortunately, there are scarce data regarding COX-2 expression in CRC in Africa where CRC incidence is on the increase with younger age affectation and unfavourable outcomes.

Aims: This retrospective study aims to determine the proportion of CRCs that over-express COX-2 and document any relationship between COX-2 over-expression with clinicopathological features such as histologic subtype, tumour grade, age and sex.

Methods: All the 139 CRCs that were histologically diagnosed at Aminu Kano Teaching Hospital over a 5-year period were included, but only 124 Formalin-fixed paraffin-embedded tissue blocks were sectioned and stained with COX-2 antibody. COX-2 expression was scored for distribution (no cells = 0, 1%-10% = 1, 11%-50% = 2, 51%-80% = 3, 81%-100% = 4) and intensity (no stain = 0; weak = 1; moderate = 2, strong = 3). The immunoreactive score (IRS) is a product of intensity (I) and distribution (D) as: 9-12 strongly +, 5-8 moderately +, 1-4 weakly + and 0 negative. Over-expression of COX-2 is an IRS of 5-12. Outcomes were statistically evaluated with clinicopathological data.

Results: The CRCs occurred more commonly in males (M: F, 2:1), in the middle age group (mostly between 30 and 59 years), and 51.1% of cases occurred before 50 years and peaked in the 6th decade. Over-expression of COX-2 was observed in 46.8% (58/124) and was strongly associated with adenocarcinoma (ADC) not otherwise specified (NOS) (moderately and poorly differentiated tumours) but not with age or sex.

Conclusion: The over-expression of COX-2 was significantly associated with ADC NOS (moderately and poorly differentiated tumours), indicating that it may influence the outcome of CRCs with possible variation in tumour subtype.