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

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.