Clinicopathologic and biological significance of kallikrein 6 overexpression in human gastric cancer.
OBJECTIVE
Human kallikrein genes (KLK) have been reported to be involved in human malignancies and several KLKs are promising biomarkers of prostate, ovarian, testicular, and breast cancers. Herein, we investigated the clinicopathologic and biological significance of KLK6 gene expression in human gastric cancer.


METHODS
Using real-time reverse transcription-PCR, we analyzed the KLK6 expression status with respect to various clinicopathologic variables in 66 patients with gastric cancer. In addition, we established a KLK6 stably suppressed gastric cancer cell line (MKN28) using small interfering RNA-mediated gene silencing, and investigated its effects on the cell proliferation rate, cell cycle, and invasiveness.


RESULTS
The KLK6 gene expression in cancerous tissue (0.37 +/- 0.53) was significantly (P < 0.000001) higher than that in noncancerous tissue (0.026 +/- 0.060). Elevated KLK6 expression was significantly associated with lymphatic invasion (P = 0.03). Furthermore, patients with a high KLK6 expression had a significantly poorer survival rate than those with a low KLK6 expression (P = 0.03). Therefore, we showed that KLK6 gene silencing with KLK6 small interfering RNA effectively suppressed the cell proliferation rate (P = 0.002), cell population in the S phase (P < 0.01), and invasiveness (P < 0.01) in comparison to mock-transfected cells.


CONCLUSIONS
The KLK6 gene is markedly overexpressed in gastric cancer tissue and its expression status may be a powerful prognostic indicator for patients with gastric cancer. Our findings also suggest that KLK6 may possibly be a novel target for gastric cancer therapy by gene-silencing procedures.
Nagahara
Hisashi
H
Department of Surgery, Medical Institute of Bioregulation, Kyushu University, Tsurumihara, Beppu, Japan.
Mimori
Koshi
K
Utsunomiya
Tohru
T
Barnard
Graham F
GF
Ohira
Masaichi
M
Hirakawa
Kosei
K
Mori
Masaki
M
D014408:Biomarkers, Tumor; D015153:Blotting, Western; D002453:Cell Cycle; D045744:Cell Line, Tumor; D002465:Cell Movement; D049109:Cell Proliferation; D017931:DNA Primers / Q000737:chemistry; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D006801:Humans; D007150:Immunohistochemistry; D007610:Kallikreins / Q000096:biosynthesis*; D008207:Lymphatic Metastasis; D008297:Male; D009361:Neoplasm Invasiveness; D011379:Prognosis; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013274:Stomach Neoplasms / Q000378:metabolism* / Q000628:therapy; D013997:Time Factors; D014162:Transfection; D016896:Treatment Outcome
D014408:Biomarkers, Tumor; D017931:DNA Primers; D012333:RNA, Messenger; D034741:RNA, Small Interfering; C103551:KLK6 protein, human; D007610:Kallikreins