title: Enhanced MAPK signaling drives ETS1-mediated induction of miR-29b leading to downregulation of TET1 and changes in epigenetic modifications in a subset of lung SCC.
abstract: Non-small-cell lung cancer is the leading cause of cancer death worldwide and is comprised of several histological subtypes, the two most common being adenocarcinoma (AC) and squamous cell carcinoma (SCC). Targeted therapies have successfully improved response rates in patients with AC tumors. However, the majority of SCC tumors lack specific targetable mutations, making development of new treatment paradigms for this disease challenging. In the present study, we used iterative non-negative matrix factorization, an unbiased clustering method, on mRNA expression data from the cancer genome atlas (TCGA) and a panel of 24 SCC cell lines to classify three disease segments within SCC. Analysis of gene set enrichment and drug sensitivity identified an immune-evasion subtype that showed increased sensitivity to nuclear factor-κB and mitogen-activated protein kinase (MAPK) inhibition, a replication-stress associated subtype that showed increased sensitivity to ataxia telangiectasia inhibition, and a neuroendocrine-associated subtype that showed increased sensitivity to phosphoinositide 3-kinase and fibroblast growth factor receptor inhibition. Additionally, each of these subtypes exhibited a unique microRNA expression profile. Focusing on the immune-evasion subtype, bioinformatic analysis of microRNA promoters revealed enrichment for binding sites for the MAPK-driven ETS1 transcription factor. Indeed, we found that knockdown of ETS1 led to upregulation of eight microRNAs and downregulation of miR-29b in the immune-evasion subtype. Mechanistically, we found that miR-29b targets the DNA-demethylating enzyme, TET1, for downregulation resulting in decreased 5-hmC epigenetic modifications. Moreover, inhibition of MAPK signaling by gefitinib led to decreased ETS1 and miR-29b expression with a corresponding increase in TET1 expression and increase in 5-hmC. Collectively, our work identifies three subtypes of lung SCC that differ in drug sensitivity and shows a novel mechanism of miR-29b regulation by MAPK-driven ETS1 expression which leads to downstream changes in TET1-mediated epigenetic modifications.
authors.affiliation: AstraZeneca, R&D Oncology iMed, Alderley Park, Macclesfield, UK.
authors.forename: M A
authors.initials: MA
authors.lastname: Taylor
authors.affiliation: AstraZeneca, R&D Oncology iMed, Alderley Park, Macclesfield, UK.
authors.forename: M
authors.initials: M
authors.lastname: Wappett
authors.affiliation: AstraZeneca, R&D Oncology iMed, Alderley Park, Macclesfield, UK.
authors.forename: O
authors.initials: O
authors.lastname: Delpuech
authors.affiliation: Personalised Healthcare and Biomarkers, AstraZeneca, Alderley Park, Macclesfield, UK.
authors.forename: H
authors.initials: H
authors.lastname: Brown
authors.affiliation: AstraZeneca, R&D Oncology iMed, Alderley Park, Macclesfield, UK.
authors.forename: C M
authors.initials: CM
authors.lastname: Chresta
mesh_terms: D044503:5-Methylcytosine / Q000031:analogs & derivatives / Q000378:metabolism; D001374:Azacitidine / Q000494:pharmacology; D002294:Carcinoma, Squamous Cell / Q000235:genetics*; D045744:Cell Line, Tumor; D019295:Computational Biology; D015536:Down-Regulation; D044127:Epigenesis, Genetic; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics*; D020935:MAP Kinase Signaling System / Q000502:physiology*; D035683:MicroRNAs / Q000502:physiology*; D006899:Mixed Function Oxygenases / Q000235:genetics*; D050784:Proto-Oncogene Protein c-ets-1 / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D019139:Tumor Escape
chemical_list: C494041:ETS1 protein, human; C532045:MIRN29a microRNA, human; D035683:MicroRNAs; D050784:Proto-Oncogene Protein c-ets-1; D011518:Proto-Oncogene Proteins; C011865:5-hydroxymethylcytosine; D044503:5-Methylcytosine; D006899:Mixed Function Oxygenases; C462539:TET1 protein, human; D001374:Azacitidine