Background: The tumour suppressor gene 'mutated in colorectal cancer' (MCC) is silenced through promoter methylation in colorectal cancer and has been implicated as a regulator of the nuclear factor kappa B (NFκB) pathway. Therefore, we aimed to determine whether MCC modulates NFκB activation in colorectal canc er. Materials and Methods: NFκB activation was assessed using luciferase reporter assays in colorectal cancer cells in vitro. MCC methylation was analysed in primary tumour specimens from patients with inflammatory bowel disease. Results: Re-expression of MCC reduced NFκB-dependent transcription in tumour necrosis factor alpha (TNFα)- or lipopolysaccharide (LPS)-stimulated cells. Conversely, knockdown of MCC resulted in accumulation of the inhibitor of kappa B alpha (IκBα) protein, encoded by NFKBIA, a first response gene specifically and rapidly regulated by NFκB pathway activation. The MCC gene is methylated in up to 6/16 of inflammatory bowel disease-associated tissue specimens, and myosin-10 and valosin-containing protein were identified as MCC-interacting proteins. Conclusion: These findings suggest that MCC modulates NFκB pathway signalling indirectly in colorectal cancer cells.