title: Alterations in mitochondrial and apoptosis-regulating gene expression in photodynamic therapy-resistant variants of HT29 colon carcinoma cells.
abstract: Photodynamic therapy (PDT) is a novel cancer therapy inducing irreversible photodamage to tumor tissue via photosensitizer-mediated oxidative cytotoxicity. The cellular and molecular responses associated with PDT are only partially understood. We have reported previously the generation of several photosensitizer-specific PDT-resistant cell variants of HT29 human colon adenocarcinoma cells by selecting cells from sequential PDT treatment using different photosensitizers. In this report, we describe the use of messenger RNA (mRNA) differential display to identify genes that were differentially expressed in the parental HT29 cells compared with their resistant variants. In comparison with parental HT29 cells, mRNA expression was increased in the PDT-resistant cell variants for BNIP3, estrogen receptor-binding fragment-associated gene 9, Myh-1c, cytoplasmic dynein light chain 1, small membrane protein I and differential dependent protein. In contrast, expression in the PDT-resistant variants was downregulated for NNX3, human HepG2 3' region Mbol complementary DNA, glutamate dehydrogenase, hepatoma-derived growth factor and the mitochondrial genes coding for 16S ribosomal RNA (rRNA) and nicotinamide adenine dinucleotide (NADH) dehydrogenase subunit 4. The reduction for mitochondrial 16S rRNA in the PDT-resistant variants was confirmed by Northern blotting, and the elevated expression of the proapoptotic BNIP3 in the PDT-resistant variants was confirmed by Northern and Western blotting analysis. We also examined the expression of some additional apoptosis-regulating genes using Western blotting. We show an increased expression of Bcl-2 and heat shock protein 27 and a downregulation of Bax in the PDT-resistant variants. In addition, the mutant p53 levels in the parental HT29 cells were reduced substantially in the PDT-resistant variants. We suggest that the altered expression in several mitochondrial and apoptosis-regulating genes contributes to PDT resistance.
authors.affiliation: Department of Pathology and Molecular Medicine, McMaster University, Hamilton, ON, Canada.
authors.forename: Xiao Yun
authors.initials: XY
authors.lastname: Shen
authors.forename: Natalie
authors.initials: N
authors.lastname: Zacal
authors.forename: Gurmit
authors.initials: G
authors.lastname: Singh
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Rainbow
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D003110:Colonic Neoplasms / Q000235:genetics* / Q000378:metabolism; D019008:Drug Resistance, Neoplasm; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects* / Q000528:radiation effects; D055551:HSP27 Heat-Shock Proteins; D019073:HT29 Cells; D006360:Heat-Shock Proteins / Q000187:drug effects / Q000235:genetics; D006801:Humans; D008928:Mitochondria / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D018832:Molecular Chaperones; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000187:drug effects / Q000235:genetics; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000494:pharmacology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000187:drug effects / Q000235:genetics; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000187:drug effects / Q000235:genetics; D051028:bcl-2-Associated X Protein
chemical_list: C494826:BAX protein, human; D055551:HSP27 Heat-Shock Proteins; C057725:HSPB1 protein, human; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D009363:Neoplasm Proteins; D017319:Photosensitizing Agents; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein