RESUMEN
INTRODUCTION: Genetic factors contribute as major determinants in the pathophysiological mechanisms of chronic obstructive pulmonary disease (COPD). Therefore, identification of candidate genes and various gene polymorphisms have improved our understanding of COPD. OBJECTIVES: Clarify the genes, including HIF1A, that contribute to the development of COPD. METHODS: We compared the genotype frequencies of 12 polymorphisms in seven detoxification-related genes (GSTM1, GSTT1, GSTP1 exon 5, CYP1A1 exon 7, CYP1A1 3'-flanking, CYP2E1 intron 6, CYP2E1 5'-flanking, EPHX1 exon 3, EPHX1 exon 4 and HMOX1 promoter) and the hypoxia-related HIF1A (C1772T and G1790A) genes between 48 Japanese patients with work-related COPD who had a working history in a poison gas factory during World War II and two control groups (n=172 and 110 subjects, respectively). RESULTS: As expected, wild homozygotes for GSTP1 Ile105Val and EPHX1 slow/very slow phenotypes were associated with susceptibility (P=0.031) and severity (P=0.036) of COPD, respectively. Moreover, compound heterozygosity of transcription-activating HIF1A polymorphisms was observed in two patients with COPD, but not in control individuals (P=0.091). CONCLUSION: This is the first report that examined HIF1A polymorphisms in COPD and demonstrated a possible role of HIF-1α in COPD, as well as GSTP1 and EPHX1.
Asunto(s)
Pueblo Asiatico/genética , Epóxido Hidrolasas/genética , Gutatión-S-Transferasa pi/genética , Subunidad alfa del Factor 1 Inducible por Hipoxia/genética , Enfermedad Pulmonar Obstructiva Crónica/genética , Adulto , Anciano , Anciano de 80 o más Años , Citocromo P-450 CYP1A1/genética , Citocromo P-450 CYP2E1/genética , Femenino , Frecuencia de los Genes , Variación Genética , Genotipo , Glutatión Transferasa/genética , Hemo-Oxigenasa 1/genética , Humanos , Japón , Masculino , FenotipoRESUMEN
BACKGROUND AND OBJECTIVE: The transcription factor, hypoxia-inducible factor-1 (HIF-1), is a master regulator of hypoxia, including repression of DNA repair systems, resulting in genomic instability in cancer cells. The roles of the polymorphic HIF-1α variants, C1772T (P582S) and G1790A (A588T), which are known to enhance transcriptional activity, were evaluated in lung cancers. METHODS: HIF-1α polymorphisms were assessed by direct sequencing in a total of 83 lung cancer patients (42 adenocarcinomas, 30 squamous cell, four adenosquamous cell and seven small cell lung carcinomas) and in 110 healthy control subjects. The relationship between these polymorphisms and the frequently observed genetic and/or epigenetic aberrations, TP53 loss of heterozygosity (LOH), 1p34 LOH, retinoblastoma-1 (RB1) LOH, p16 inactivation and epidermal growth factor receptor aberrations, was then assessed. RESULTS: There were no significant differences in genotype frequencies for either C1772T or G1790A between lung cancer patients and healthy controls. However, the frequency of the HIF1A C1772T variant allele was significantly higher in lung cancer patients with TP53 LOH (P = 0.015). Among adenocarcinoma patients, individuals with variant alleles of either polymorphism showed significantly higher frequencies of TP53 LOH (P = 0.047), 1p34 LOH (P = 0.009), or either of these (P = 0.008) in the tumours. The in vitro transcriptional activity of these HIF1A variants in A549 lung cancer cells was significantly greater than that of the wild type under either normoxic or hypoxic conditions, especially for P582S in cells containing mutant p53 (P < 0.0005 and P < 0.005, respectively). CONCLUSIONS: These findings indicate that functional polymorphisms in the HIF-1α gene may have an important impact on lung carcinogenesis, especially in adenocarcinomas, possibly by increasing genomic instability.
Asunto(s)
Adenocarcinoma/genética , Carcinoma Adenoescamoso/genética , Carcinoma de Células Escamosas/genética , Subunidad alfa del Factor 1 Inducible por Hipoxia/genética , Neoplasias Pulmonares/genética , Polimorfismo Genético/genética , Carcinoma Pulmonar de Células Pequeñas/genética , Anciano , Estudios de Casos y Controles , Frecuencia de los Genes/genética , Predisposición Genética a la Enfermedad/genética , Inestabilidad Genómica/genética , Genotipo , Humanos , Pérdida de Heterocigocidad/genética , Masculino , Persona de Mediana Edad , Mutación/genética , Proteína p53 Supresora de Tumor/genéticaRESUMEN
Existence of cancer stem cells (CSCs) is still hypothetical and their practical marker is not available yet in lung cancer. To verify the possible existence of CSCs and to find their markers in lung cancer, we compared the p16/Rb and telomerase status in 83 lung cancer tissues and 15 lung cancer cell lines, since inactivation of p16/Rb pathway is considered to be a prerequisite for normal somatic cells to become immortal cancer cells. We found that 7 of 14 adenocarcinoma, but not squamous cell carcinoma, tissues with high telomerase activity and 3 adenocarcinoma cell lines likely had intact p16/Rb. Such cell lines showed higher colony formation capacity in soft agar compared with inactivated ones with similar growth rate. Moreover, cisplatin-resistant cell line PC9/CDDP with intact p16/Rb, but not PC14/CDDP with its inactivation, increased the colony formation capacity compared with the parent cells. Since CSCs are considered to be resistant to conventional anticancer drugs, they could have been concentrated as long as CSCs existed. We propose that half of immortal lung adenocarcinomas are derived from innately telomerase-positive stem cells, which might be the origin of CSCs, and that high telomerase activity with intact p16/Rb could be a marker of stem cell origin.
Asunto(s)
Adenocarcinoma/metabolismo , Carcinoma de Células Escamosas/metabolismo , Resistencia a Antineoplásicos , Regulación Neoplásica de la Expresión Génica , Neoplasias Pulmonares/metabolismo , Proteínas de Neoplasias/genética , Anciano , Antineoplásicos/farmacología , Línea Celular Tumoral , Cisplatino/farmacología , Inhibidor p16 de la Quinasa Dependiente de Ciclina , Femenino , Humanos , Pérdida de Heterocigocidad , Neoplasias Pulmonares/patología , Masculino , Persona de Mediana Edad , Proteína de Retinoblastoma/metabolismo , Células Madre/citología , Telomerasa/metabolismoRESUMEN
The prognosis of lung cancer remains poor, and biological heterogeneity is largely responsible, especially in adenocarcinoma. We previously found that only one third of non-small cell lung cancer (NSCLC) but most small cell lung cancer (SCLC) tissues have strong telomerase activity, representing the difference in the history of multiple clonal selections. To reveal the genes differentially involved in telomerase activation mechanisms, we analyzed the relationship between common genetic aberrations and telomerase activity in 83 lung cancer tissues. We found that half (7 of 14) of lung adenocarcinomas with high telomerase activity showed neither TP53 nor RB1 deletion, while all squamous cell carcinomas and SCLCs with high telomerase activity showed loss of heterozygosity of at least one, if not both, of these suppressor oncogenes, indicating that these genetic aberrations are not required in activation of telomerase in a unique subset of adenocarcinoma. Furthermore, whereas the aberrations in TP53, RB1 and 1p34-pter were mutually related in 42 adenocarcinoma tissues, EGFR aberrations showed no relationship to either of them. These findings indicate that EGFR activating aberrations occur independently of other common genetic aberrations or telomerase activation mechanisms in lung adenocarcinoma, and that the distinct subset of lung adenocarcinoma with high telomerase activity without any common genetic aberrations may possibly have arisen from a telomerase-positive or telomerase-competent normal cell.