Heterodimeric interaction between GKN2 and TFF1 entails synergistic antiproliferative and pro-apoptotic effects on gastric cancer cells.
BACKGROUND
GKN2 and TFF1 form a heterodimer that is only generated in the mucus-secreting cells of the normal stomach. The formation of this heterodimer is frequently disrupted in gastric cancer. However, the precise roles of GKN2 alone and in the heterodimer with TFF1 as well as the contributions of GKN2 and the heterodimer to gastric carcinogenesis are poorly understood.


METHODS
Cell viability, proliferation, and apoptosis were analyzed in AGS, MKN1, MKN28, and MKN45 gastric cancer cells transfected with GKN2 and/or TFF1 using MTT, BrdU incorporation, and apoptosis assays, respectively. In addition, cell viability was examined in HFE-145 non-neoplastic gastric epithelial cells after GKN2 and/or TFF1 silencing. Furthermore, the cell cycle and the expression of cell cycle and apoptosis related proteins were assessed. The interaction between GKN2 and TFF1 was confirmed by co-immunoprecipitation. Immunohistochemistry was employed to explore TFF1 expression in 169 gastric cancer tissues.


RESULTS
Co-transfection with GKN2 and TFF1 significantly inhibited cell viability and proliferation by inducing G1/S cell cycle arrest and suppressing positive cell cycle regulators. Simultaneous knockdown of GKN2 and TFF1 in HFE-145 cells resulted in markedly increased cell viability. Moreover, the interaction of GKN2 and TFF1 promoted cell death by enhancing caspase-3/7 activity and upregulating pro-apoptotic proteins. At the mRNA level, GKN2 and TFF1 were found to be positively correlated in non-tumor and tumor samples. Immunohistochemistry revealed loss of TFF1 expression in 128 (75.73%) of 169 gastric cancers. There was a borderline-significant association between GKN2 and TFF1 protein expression in gastric cancers (P = 0.0598).


CONCLUSIONS
Collectively, our data demonstrated that the interaction between GKN2 and TFF1 can have synergistic antiproliferative and pro-apoptotic effects on gastric cancer.
Department of Pathology, College of Medicine, The Catholic University of Korea, 505 Banpo-dong, Seocho-gu, Seoul, 137-701, Korea.
Olga
O
Kim
Department of Pathology, College of Medicine, The Catholic University of Korea, 505 Banpo-dong, Seocho-gu, Seoul, 137-701, Korea.
Jung Hwan
JH
Yoon
Department of Pathology, College of Medicine, The Catholic University of Korea, 505 Banpo-dong, Seocho-gu, Seoul, 137-701, Korea.
Won Suk
WS
Choi
Department of Medicine, Howard University, Washington, DC, 20060, USA.
Hassan
H
Ashktorab
Department of Medicine, Howard University, Washington, DC, 20060, USA.
Duane T
DT
Smoot
Department of Pathology, College of Medicine, The Catholic University of Korea, 505 Banpo-dong, Seocho-gu, Seoul, 137-701, Korea.
Suk Woo
SW
Nam
Department of Pathology, College of Medicine, The Catholic University of Korea, 505 Banpo-dong, Seocho-gu, Seoul, 137-701, Korea.
Jung Young
JY
Lee
Department of Pathology, College of Medicine, The Catholic University of Korea, 505 Banpo-dong, Seocho-gu, Seoul, 137-701, Korea. wonsang@catholic.ac.kr.
Won Sang
WS
Park
D017209:Apoptosis / Q000235:genetics*; D002352:Carrier Proteins / Q000235:genetics*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000235:genetics; D002470:Cell Survival / Q000235:genetics; D059585:G1 Phase Cell Cycle Checkpoints / Q000235:genetics; D055785:Gene Knockdown Techniques; D006801:Humans; D047468:Immunoprecipitation; D012333:RNA, Messenger / Q000378:metabolism; D013274:Stomach Neoplasms / Q000235:genetics* / Q000473:pathology; D014162:Transfection; D000071163:Trefoil Factor-1 / Q000235:genetics*
D002352:Carrier Proteins; C503073:GKN2 protein, human; D012333:RNA, Messenger; C051838:TFF1 protein, human; D000071163:Trefoil Factor-1
Apoptosis; GKN2; Gastric cancer; Proliferation; TFF1