Genetic and epigenetic alterations are involved in the regulation of TPM1 in cholangiocarcinoma
Authors: Wei Yang
Xiaoyuan Wang
Kedong Li
Yueming Sun
Wei Zheng
Haofeng Liu
Journal: International Journal of Oncology (2013)
Discipline: CLINICAL MEDICINE
Keywords: Cholangiocarcinoma; TPM1; regulation mechanism; cell lines; tumor tissues
Affiliations: Department of Minimally Invasive Surgery, The First Affiliated                     Hospital of Nanjing Medical University, Nanjing 210029, P.R. China.

Abstract:  Cholangiocarcinoma is a malignant tumor originating from biliary epithelial cells. The tumor suppressor gene tropomyosin 1 (TPM1) is downregulated in several human cancer types; however, its expression status in cholangiocarcinoma is still unknown. We elucidated TPM1 expression and its regulation mechanism in cholangiocarcinoma. Real-time (RT)-PCR, western blot analysis and immunohistochemistry were performed to examine TPM1 expression levels in cholangiocarcinoma cell lines and tumor tissues. Cell lines were treated with lentiviral vector containing the miR-21 knockdown and inhibitors of genetic and epigenetic mechanisms (manumycin A, LY294002, U0126, DAC and TSA), and the TPM1 expression change was observed by RT-PCR and western blot analyses. Cell proliferation, apoptosis and migration were evaluated by water-soluble tetrazolium salt (WST-1) assay, flow cytometry and wound healing experiments, respectively. TPM1 was downregulated in the intrahepatic cholangiocarcinoma cells (HuCCT1) and upregulated in the extrahepatic cholangiocarcinoma cells (QBC939) compared with normal intrahepatic biliary epithelial cells (HIBEC). TPM1 stained negative in the intrahepatic cholangiocarcinoma tissues, as revealed by immunohistochemistry, although there was no significant difference in staining of the intrahepatic cholangiocarcinoma tissues and adjacent non-cancer tissues. RAS and two important downstream signaling pathways (RAS/PI3K/AKT and RAS/MEK/ERK) were involved in TPM1 regulation and inhibition of the epigenetic mechanisms such as DNA methylation, histone deacetylation and miR-21 upregulation upregulated TPM1 expression. Inhibitors of genetic and epigenetic mechanisms (manumycin A, LY294002, U0126, DAC and TSA) inhibited cell proliferation and migration and induced apoptosis. These data indicated that TPM1 is downregulated in HuCCT1 cells and that the Ras signaling pathway as well as DNA methylation, histone deacetylation and miR-21 upregulation play important roles in the suppression of TPM1 expression in HuCCT1 cells. Thus, compounds that inhibit genetic and epigenetic mechanisms may be promising agents in treating cholangiocarcinoma. 

Retracted: No

PubPeer comments:
 Figure 2 and 3. * Red boxes: The tubulin panels of the manumycin A and U0126 treatments in Figures 2A and 2B, as well as the LV treatments in Figure 3D all appear to look similar. * Blue boxes: The tubulin panels of the DAC and TSA treatments in Figures 2D and 2E appear to look similar. ![file] These concerns have been reported to the journal in 2015 and a corrigendum was published in 2017, which reads:  After having re-examined our original data, we realize that the figure was compiled incorrectly, and have returned to our source data. A corrected version of Fig. 2 is presented here, showing the correct control u03b1-tubulin data for Fig. 2A and E, as they ought to have appeared. This error did not overall affect the conclusions reported in the study. We sincerely apologize for this mistake, and thank the reader of our article who drew this matter to our attention. Furthermore, we regret any inconvenience this mistake has caused. The corrigendum is barely visible however, from the paper at the journal s website. You have to scroll all the way down to see a tiny notice. ,