Digestive tract cancers – gastric-, colorectal-, pancreatic-, hepatocarcinoma- and esophageal are some of the
most frequent cancers; they are characterized by invasivity, metastatic potential and bad outcomes. This group includes
several of the most critical cancers (those ranked 2nd-4th in cancer related mortality), and, despite all efforts, they remain
with low survival rates and lack of success of therapies. Discovery of novel biomarkers may improve disease characterization
and make optimized or personalized therapies possible. The novel biomarkers are expected to provide, hopefully, less
invasive or non-invasive diagnostic tools to make possible earlier detection of disease, and, also, they will provide more
reliable selection in the drug discovery process, and provide guidance for personalized medicine.
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.