Tropomyosin3 overexpression and a potential link to epithelial-mesenchymal transition in human hepatocellular carcinoma.
BACKGROUND
Since hepatocellular carcinoma (HCC) is one of the leading causes of cancer death worldwide, it is still important to understand hepatocarcinogenesis mechanisms and identify effective markers for tumor progression to improve prognosis. Amplification and overexpression of Tropomyosin3 (TPM3) are frequently observed in HCC, but its biological meanings have not been properly defined. In this study, we aimed to elucidate the roles of TPM3 and related molecular mechanisms.


METHODS
TPM3-siRNA was transfected into 2 HCC cell lines, HepG2 and SNU-475, which had shown overexpression of TPM3. Knockdown of TPM3 was verified by real-time qRT-PCR and western blotting targeting TPM3. Migration and invasion potentials were examined using transwell membrane assays. Cell growth capacity was examined by colony formation and soft agar assays.


RESULTS
Silencing TPM3 resulted in significant suppression of migration and invasion capacities in both HCC cell lines. To elucidate the mechanisms behind suppressed migration and invasiveness, we examined expression levels of Snail and E-cadherin known to be related to epithelial-mesenchymal transition (EMT) after TPM3 knockdown. In the TPM3 knockdown cells, E-cadherin expression was significantly upregulated and Snail downregulated compared with negative control. TPM3 knockdown also inhibited colony formation and anchorage independent growth of HCC cells.


CONCLUSIONS
Based on our findings, we formulate a hypothesis that overexpression of TPM3 activates Snail mediated EMT, which will repress E-cadherin expression and that it confers migration or invasion potentials to HCC cells during hepatocarcinogenesis. To our knowledge, this is the first evidence that TPM3 gets involved in migration and invasion of HCCs by modifying EMT pathway.
Choi
Hye-Sun
HS
Department of Microbiology, School of Medicine, The Catholic University of Korea, 505 Banpo-dong, Socho-gu, Seoul 137-701, Korea.
Yim
Seon-Hee
SH
Xu
Hai-Dong
HD
Jung
Seung-Hyun
SH
Shin
Seung-Hun
SH
Hu
Hae-Jin
HJ
Jung
Chan-Kwon
CK
Choi
Jong Young
JY
Chung
Yeun-Jun
YJ
D015820:Cadherins / Q000096:biosynthesis; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D002465:Cell Movement / Q000502:physiology; D004847:Epithelial Cells / Q000473:pathology; D005353:Fibronectins / Q000096:biosynthesis; D055785:Gene Knockdown Techniques; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D008637:Mesenchymoma / Q000473:pathology; D009361:Neoplasm Invasiveness; D034741:RNA, Small Interfering / Q000008:administration & dosage / Q000235:genetics; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors / Q000096:biosynthesis; D014162:Transfection; D014335:Tropomyosin / Q000096:biosynthesis* / Q000235:genetics; D014746:Vimentin / Q000096:biosynthesis
D015820:Cadherins; D005353:Fibronectins; D034741:RNA, Small Interfering; D000071250:Snail Family Transcription Factors; C498783:TPM3 protein, human; D014157:Transcription Factors; D014335:Tropomyosin; D014746:Vimentin