SMAD4 and neoplasm: Compatible with the complex role TGF-β plays in cancer progression, T cells that remain immunocompetent and succeed in limiting tumour growth have also been shown to require TGF-β signalling, which is thus classified as tumour suppressor signalling; indeed, T cells depend on their TGF-β/Smad4 signalling pathway in order to suppress gastrointestinal cancer, as demonstrated after genetic inactivation of TβRII in T cell progenitors [151].