title: IL-6 enriched lung cancer stem-like cell population by inhibition of cell cycle regulators via DNMT1 upregulation.
abstract: Tumors are influenced by a microenvironment rich in inflammatory cytokines, growth factors and chemokines, which may promote tumor growth. Interleukin-6 (IL-6) is a multifunctional cytokine and known as a regulator of immune and inflammation responses. IL-6 has also been reported to be associated with tumor progression and chemoresistance in different types of cancers. In our study, we demonstrated that IL-6 enriches the properties of lung cancer stem-like cells in A549 lung cancer cells cultured in spheroid medium. IL-6 also promotes sphere formation and stem-like properties of A549 cells by enhancing cell proliferation. Methylation-specific polymerase chain reaction (PCR) was performed and revealed that IL-6 increased methylation of p53 and p21 in A549 cancer cells. Western blot analysis and quantitative real-time PCR demonstrated that IL-6 increased the expression of DNA methyltransferase 1 (DNMT1) in A549 cells cultured in spheroid medium, but not the expression of DNMT3a or DNMT3b. Knockdown of DNMT1 eliminated IL-6-mediated hypermethylation of cell cycle regulators and enrichment of lung cancer stem-like properties. In conclusion, our study, for the first time, shows that the IL-6/JAK2/STAT3 pathway upregulates DNMT1 and enhances cancer initiation and lung cancer stem cell (CSC) proliferation by downregulation of p53 and p21 resulting from DNA hypermethylation. Upon blockage of the IL-6/JAK2/STAT3 pathway and inhibition of DNMT1, the proliferation of lung CSCs was reduced and their formation of spheres and ability to initiate tumor growth were decreased. These data suggest that targeting of the IL-6/JAK2/STAT3 signaling pathway and DNMT1 may become important strategies for treating lung cancer.
authors.affiliation: Institute of Clinical Medicine, National Yang-Ming University School of Medicine, Taipei, Taiwan; Department of Emergency, Taipei Veterans General Hospital, Taipei, Taiwan.
authors.forename: Chen-Chi
authors.initials: CC
authors.lastname: Liu
authors.forename: Jiun-Han
authors.initials: JH
authors.lastname: Lin
authors.forename: Tien-Wei
authors.initials: TW
authors.lastname: Hsu
authors.forename: Kelly
authors.initials: K
authors.lastname: Su
authors.forename: Anna Fen-Yau
authors.initials: AF
authors.lastname: Li
authors.forename: Han-Shui
authors.initials: HS
authors.lastname: Hsu
authors.forename: Shih-Chieh
authors.initials: SC
authors.lastname: Hung
mesh_terms: D000818:Animals; D002453:Cell Cycle; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000037:antagonists & inhibitors* / Q000502:physiology; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000502:physiology*; D019175:DNA Methylation; D006801:Humans; D015850:Interleukin-6 / Q000502:physiology*; D053614:Janus Kinase 2 / Q000502:physiology; D008175:Lung Neoplasms / Q000473:pathology*; D051379:Mice; D014411:Neoplastic Stem Cells / Q000473:pathology*; D050796:STAT3 Transcription Factor / Q000502:physiology; D018874:Spheroids, Cellular; D016159:Tumor Suppressor Protein p53 / Q000037:antagonists & inhibitors* / Q000502:physiology; D015854:Up-Regulation
chemical_list: C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; C508600:IL6 protein, human; D015850:Interleukin-6; D050796:STAT3 Transcription Factor; D016159:Tumor Suppressor Protein p53; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases; C000619380:DNMT1 protein, human; C000619381:Dnmt1 protein, mouse; C507924:JAK2 protein, human; D053614:Janus Kinase 2
keywords: DNMT1; IL-6/JAK2/STAT3 pathway; lung cancer stem cell; proliferation