Kallikrein 4 (KLK4), a New Member of the Human Kallikrein Gene Family is Upregulated by Estrogen and Progesterone in the Human Endometrial Cancer Cell Line, KLE

Endometrial cancer is the fourth most common female malignancy in women in developed countries. Estrogen, and to a lesser degree, progesterone, regulate specific target genes that are involved in endometrial tumorigenesis. A family of proteases involved in cellular proliferation, extracellular matrix degradation and thus, implicated in tumorigenesis, and regulated by estrogen and progesterone in a number of systems, are the tissue kallikreins (KLKs). KLK4, a new member of the KLK gene family, was found to be expressed to varying levels in a number of endometrial cancer cell lines- HEC1A, HEC1B, Ishikawa, RL95-2 and KLE- at both the mRNA and protein level. On the addition of 10 nmol/L estradiol, progesterone, or a combination of both over a 48 h period, an increase in the intracellular protein levels of K4 were observed when compared to the control (untreated) cells. We have also identified a novel KLK4 transcript with a complete exon 4 deletion. The significance of this alternative transcript, which would give rise to a truncated protein without a serine residue (which is essential for catalytic activity), is yet to be established. These cell lines now provide a model system to study the role of KLK4 and the molecular mechanisms of KLK4 regulation by estrogen and progesterone, in endometrial tumorigenesis.