Summary
Serine proteases are proteolytic enzymes with an active serine residue in their catalytic
site. Kallikreins are a subgroup of the serine protease family and are known to have
diverse physiological functions. The human tissue kallikrein gene family has now been
fully characterized and includes 15 members, clustered in a 300 kb region on chromosome
19q13.4. In this review, we discuss the common structural features of kallik-reins
at the DNA, mRNA and protein levels. Kallikreins are secreted as inactive zymogens
and are activated by cleavage of an N-terminal peptide. Some kallikreins can undergo
autoactivation while others may be activated by other kallikreins or other proteases.
Most kallikreins are predicted to have trypsin-like enzymatic activity except for
three members which may have chymotrypsin-like activity. Circumstantial evidence suggests
that at least some kallikreins may be part of an enzymatic cascade pathway which is
activated in aggressive forms of ovarian and probably other cancers. Accumulating
evidence suggests potential diagnostic and/or prognostic roles of kallikreins in diverse
malignancies. In addition to PSA, many other kallik-reins show differential expression
in malignancy. For example, hK6, 10 and 11 are promising serological markers for ovarian
cancer diagnosis. KLK10 may act as a tumor suppressor. In addition to their diagnostic and prognostic values,
kallikreins may also be good therapeutic targets.
Part of this paper was originally presented at the joint meetings of the 16th International
Congress of the International Society of Fibrinolysis and Proteolysis (ISFP) and the
17th International Fibrinogen Workshop of the International Fibrinogen Research Society
(IFRS) held in Munich, Germany, September, 2002.
Keywords
Kallikreins - tumor markers - prostate cancer - breast cancer - ovarian cancer - serine
proteases - prognostic and predictive markers