BackgroundAccumulating data indicated that circRNA plays important roles in regulating many biological processes of the tumor, the present study is designated for exploring roles of the circ-ZEB1.33-miR-200a-3p-CDK6 regulating axis in human hepatocellular carcinoma (HCC).MethodsThe regulation axis as predicted by using online tool circNet, the expression and correlation of circ-ZEB1.33-miR-200a-3p-CDK6 was verified in human HCC. The diagnostic value of both tumor and serum circ-ZEB1.33 was estimated by using clinical samples. The roles of circ-ZEB1.33-miR-200a-3p-CDK6 in regulating cell cycle were explored by using in vitro studies.ResultsOverexpression of circ-ZEB1.33 and CDK6, downregulation of miR-200a-3p were detected in human HCC tissues, negative correlation between circ-ZEB1.33 and miR-200a-3p, positive correlation between circ-ZEB1.33 and CDK6 were confirmed in human HCC tissues. Tissue and serum circ-ZEB1.33 were related to different TMN stages and prognosis in HCC patients. RNA pull-down assay implied that circ-ZEB1.33 could decrease miR-200a-3p by sponging miR-200a-3p, and the luciferase reporter assay indicated that miR-200a-3p could downregulate CDK6 transcription by targeting its 3′UTR. The in vitro assays indicated that circ-ZEB1.33 could promote the proliferation of HCC cells by increasing the percentage of S phase regulated by CDK6/Rb.ConclusionProliferation promotion roles of the circ-ZEB1.33-miR-200a-3p-CDK6 regulating axis are existed and verified in human HCC, both tumor and serum circ-ZEB1.33 can serve as an indicator for the prognosis of HCC patients.Electronic supplementary materialThe online version of this article (10.1186/s12935-018-0602-3) contains supplementary material, which is available to authorized users.

Abstract:In this paper, we show that if G is a 3-edge-connected graph with S V ðGÞ and jSj 12, then either G has an Eulerian subgraph H such that S V ðHÞ, or G can be contracted to the Petersen graph in such a way that the preimage of each vertex of the Petersen graph contains at least one vertex in S. If G is a 3-edge-connected planar graph, then for any jSj 23, G has an Eulerian subgraph H such that S V ðHÞ. As an application, we obtain a new result on Hamiltonian line graphs.

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