A comment on article “microRNA-34a inhibits epithelial mesenchymal transition in human cholangiocarcinoma by targeting Smad4 through transforming growth factor-beta/Smad pathway” Pengfei Qiao, the Second Affiliated Hospital of Harbin Medical University 9 July 2015 This comment is being published to correct a mistake in the authors‘ contributions part of the article. All of the authors of this article declare that the sentence “GL and PQ contributed equally as first author. GL and DW contributed equally as corresponding author” in the authors’ contributions part is canceled and invalid. We confirm that Pengfei Qiao is the only first author, Dequan Wu is the only corresponding author in this article. We apologize for our carelessness. Competing interests The authors declare that they have no conflicts of interest.