Deregulation of protein expression and genetic alterations were demonstrated in various cancers, including digestive. Investigations in tissue samples provided a considerable amount of knowledge, identifying altered expressions of proteins associated with tumorigenesis and tumour progression. Over-expression of some tumour-inducing or tumour promoting proteins was demonstrated, as well as expression down-regulation of several tumor suppressor genes. Often mutated and polymorphic alleles were demonstrated to occur in various cancers with high incidence. Several protein biomarkers were also demonstrated to be differentially expressed in groups of patients showing different responsivities to therapies.
Both individual proteins and sets of multiple proteins were set up as candidate biomarkers for diagnostics or monitoring, offered relevant insights on the tumorigenic mechanisms. Proteins and other molecules (mRNAs, miRNAs, lncRNAs) are also providing potential candidates for multifactorial panels of biomarkers.