First discovered as an oncogene in leukaemia, recent reports highlight an emerging role for the proto‑oncogene BCL‑3 in solid tumours. Importantly, BCL‑3 expression is upregulated in >30% of colorectal cancer cases and is reported to be associated with a poor prognosis. However, the mechanism by which BCL‑3 regulates tumorigenesis in the large intestine is yet to be fully elucidated. In the present study, it was shown for the first time that knocking down BCL‑3 expression suppressed cyclooxygenase‑2 (COX‑2)/prostaglandin E2 (PGE2) signalling in colorectal cancer cells, a pathway known to drive several of the hallmarks of cancer. RNAi‑mediated suppression of BCL‑3 expression decreased COX‑2 expression in colorectal cancer cells both at the mRNA and protein level. This reduction in COX‑2 expression resulted in a significant and functional reduction (30‑50%) in the quantity of pro‑tumorigenic PGE2 produced by the cancer cells, as shown by enzyme linked immunoassays and medium exchange experiments. In addition, inhibition of BCL‑3 expression also significantly suppressed cytokine‑induced (TNF‑α or IL‑1β) COX‑2 expression. Taken together, the results of the present study identified a novel role for BCL‑3 in colorectal cancer and suggested that expression of BCL‑3 may be a key determinant in the COX‑2‑meditated response to inflammatory cytokines in colorectal tumour cells. These results suggest that targeting BCL‑3 to suppress PGE2 synthesis may represent an alternative or complementary approach to using non‑steroidal anti‑inflammatory drugs [(NSAIDs), which inhibit cyclooxygenase activity and suppress the conversion of arachidonic acid to prostaglandin], for prevention and/or recurrence in PGE2‑driven tumorigenesis.
Keywords: COX-2; PGE2; BCL-3; colorectal cancer; hallmarks of cancer.