This invention provides pharmaceutical compositions comprising compounds including 5-phenylpenta-2,4-dienoic acid, 3-methyl-3-butenyl caffeic acid, 1,1-dimethylallyl caffeic acid, pinobanksin-3-acetate, tectochrysin, pinostrobin chalcone, benzyl ferulate and benzyl isoferulate. Methods of using such compositions, in particular in the treatment or prevention of gastrointestinal cancers, and the resensitisation of gastrointestinal cancers to therapy are also provided.