The human
tissue kallikrein (KLK1) and
kallikrein-related
peptidases (KLKs) are secreted
serine proteases with diverse expression patterns and physiological roles in different systems, including the digestive system. The aberrant expression of KLKs in gastrointestinal
malignancies as well as their implication in
carcinogenesis including cell growth regulation, angiogenesis, invasion, and
metastasis, has prompted scientists to investigate their potential as
cancer biomarkers. Expression of distinct KLKs is associated with various clinic-pathological parameters of patients with gastric, colorectal, pancreatic, hepatic, and
esophageal cancer. Moreover, several KLKs possess significant favourable or unfavourable prognostic value in these human
malignancies. Identification of novel diagnostic, prognostic and predictive
biomarkers will contribute utmost to clinical decision-making, since early diagnosis of
gastrointestinal cancer and early detection of recurrence following surgery are critical for the effective treatment of patients and for a positive clinical outcome. The current review provides a brief overview of the functional role of KLKs in gastric, colorectal, pancreatic, hepatic, and
esophageal cancer, and describes the current status of KLKs as potential tumour
biomarkers in these human
malignancies.