Kallikrein (KLK) 5 and KLK7 were reported to be overexpressed in several
cancers, but underexpressed in prostate and breast
cancers. However, the expression levels of KLK5 and KLK7 in benign breast tissues and
metastases, and the relationship between KLK5 and KLK7, have not been reported. In addition, the value of KLK5 and KLK7 in the diagnosis and prognosis prediction of
breast cancer patients is far from clear. To further determine their role and clinical significance in
breast cancer and to explore the relationship between KLK5 and KLK7, the
mRNA levels of KLK5 and KLK7 in normal breast tissues, benign breast tissues, primary
tumors, and
lymph node metastases were detected by real-time reverse transcription-polymerase chain reaction and microarray. The relationship between KLK5 and KLK7 expression and clinicopathological parameters, and the correlation between the
mRNA levels of KLK5 and KLK7 as well as the 5'-uncoding regions of KLK5 and KLK7 were analyzed. The
mRNA levels of KLK5 and KLK7 were both downregulated in breast
cancers relative to normal and benign tissues, and downregulated in
metastases compared to primary
cancers. Underexpression of KLK5 and KLK7 was correlated with postmenopausal status and positive
estrogen receptor status. The
mRNA levels of KLK5 and KLK7 were positively correlated in breast
malignancies. Moreover, four homologous sequences and 10
transcription factors as potential regulators were found on the control regions of both KLK5 and KLK7. Thus, KLK5 and KLK7 were underexpressed in parallel, potentially with the same regulation pathways, in breast
malignancies, which might contribute to the
carcinogenesis and development of
breast cancer. They are potential
biomarkers for
breast cancer.