title: Inhibition of histone lysine methylation enhances cancer-testis antigen expression in lung cancer cells: implications for adoptive immunotherapy of cancer.
abstract: Cancer-testis antigens (CTA), such as NY-ESO-1, MAGE-A1, and MAGE-A3, are immunogenic proteins encoded by genes, which are normally expressed only in male germ cells but are activated by ill-defined epigenetic mechanisms in human tumors, including lung cancers. Previously, we reported induction of these CTAs in cancer cells, but not normal cells, by DNA-demethylating agents and histone deacetylase inhibitors using clinically achievable exposure conditions. In the present study, we evaluated chromatin alterations associated with repression/activation of cancer-testis genes in lung cancer cells to further develop gene-induction regimens for cancer immunotherapy. Repression of NY-ESO-1, MAGE-A1, and MAGE-A3 coincided with DNA hypermethylation, recruitment, and binding of polycomb-group proteins, and histone heterochromatin modifications within the promoters of these genes. Derepression coincided with DNA demethylation, dissociation of polycomb proteins, and presence of euchromatin marks within the respective promoters. Short hairpin RNAs were used to inhibit several histone methyltransferases (KMT) and histone demethylases (KDM) that mediate histone methylation and repress gene expression. Knockdown of KMT6, KDM1, or KDM5B markedly enhanced deoxyazacytidine (DAC)-mediated activation of these cancer-testis genes in lung cancer cells. DZNep, a pharmacologic inhibitor of KMT6 expression, recapitulated the effects of KMT6 knockdown. Following DAC-DZNep exposure, lung cancer cells were specifically recognized and lysed by allogeneic lymphocytes expressing recombinant T-cell receptors recognizing NY-ESO-1 and MAGE-A3. Combining DNA-demethylating agents with compounds, such as DZNep, that modulate histone lysine methylation may provide a novel epigenetic strategy to augment cancer-testis gene expression as an adjunct to adoptive cancer immunotherapy.
authors.affiliation: Section of Thoracic Oncology, Surgery Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland 20892, USA.
authors.forename: Mahadev
authors.initials: M
authors.lastname: Rao
authors.forename: Nachimuthu
authors.initials: N
authors.lastname: Chinnasamy
authors.forename: Julie A
authors.initials: JA
authors.lastname: Hong
authors.forename: Yuwei
authors.initials: Y
authors.lastname: Zhang
authors.forename: Mary
authors.initials: M
authors.lastname: Zhang
authors.forename: Sichuan
authors.initials: S
authors.lastname: Xi
authors.forename: Fang
authors.initials: F
authors.lastname: Liu
authors.forename: Victor E
authors.initials: VE
authors.lastname: Marquez
authors.forename: Richard A
authors.initials: RA
authors.lastname: Morgan
authors.forename: David S
authors.initials: DS
authors.lastname: Schrump
mesh_terms: D000951:Antigens, Neoplasm / Q000235:genetics*; D045744:Cell Line, Tumor; D002843:Chromatin / Q000737:chemistry; D019175:DNA Methylation; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D020869:Gene Expression Profiling; D000076983:Histone Methyltransferases; D011495:Histone-Lysine N-Methyltransferase / Q000037:antagonists & inhibitors*; D006657:Histones / Q000378:metabolism; D006801:Humans; D016219:Immunotherapy, Adoptive; D008175:Lung Neoplasms / Q000276:immunology / Q000628:therapy*; D008239:Lysine / Q000378:metabolism; D058950:Melanoma-Specific Antigens / Q000235:genetics*; D008565:Membrane Proteins / Q000235:genetics*; D008745:Methylation; D009363:Neoplasm Proteins / Q000235:genetics*
chemical_list: D000951:Antigens, Neoplasm; C104948:CTAG1B protein, human; D002843:Chromatin; D004791:Enzyme Inhibitors; D006657:Histones; C072011:MAGEA1 protein, human; C072013:MAGEA3 protein, human; D058950:Melanoma-Specific Antigens; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D000076983:Histone Methyltransferases; D011495:Histone-Lysine N-Methyltransferase; D008239:Lysine