ABSTRACT
INTRODUCTION: Anaplastic lymphoma kinase (ALK) rearrangements are present in an important subset of non-small-cell lung cancer (NSCLC) and predict for response to the tyrosine kinase inhibitor crizotinib. In this study, we evaluated the yet unknown frequency and functional role of ALK splicing isoforms in NSCLC. METHODS: We analyzed 270 cases of NSCLC for ALK kinase domain splicing aberrations and in addition generated constructs with full-length echinoderm microtubule-associated protein-like 4 (EML4)-ALK (E13;A20) and a splicing isoform. RESULTS: Splicing isoforms of the kinase domain of ALK-including complete skipping of exon 23 (ALKdel23, ALK p.I1171fs*42) and exon 27 (ALKdel27, ALK p.T1312fs*0)-were identified in 11.1% (30 of 270 cases) of NSCLC, and these changes coexisted with ALK rearrangements, KRAS mutations, and EGFR mutations. ALK splicing isoforms were observed with full-length EML4-ALK in crizotinib-naive and treated NSCLCs. ALK T1312fs*0 was unable to render cells solely dependent on ALK signaling. Unlike EML4-ALK and EML4-ALK p.L1196M, EML4-ALK T1312fs*0 did not autophosphorylate ALK or other phosphotyrosine sites. Coexpression of equal amounts of EML4-ALK T1312fs*0 and EML4-ALK did not result in resistance to crizotinib, whereas coexpression of EML4-ALK L1196M with EML4-ALK resulted in resistance to inhibition of ALK by crizotinib. CONCLUSIONS: ALK kinase splicing isoforms were present in NSCLC and even if translated seemed to be nonfunctional variants of ALK.
Subject(s)
Adenocarcinoma/genetics , Alternative Splicing/genetics , Carcinoma, Non-Small-Cell Lung/genetics , Carcinoma, Squamous Cell/genetics , Lung Neoplasms/genetics , Oncogene Proteins, Fusion/genetics , Receptor Protein-Tyrosine Kinases/genetics , Adenocarcinoma/drug therapy , Adenocarcinoma/pathology , Adult , Aged , Aged, 80 and over , Anaplastic Lymphoma Kinase , Blotting, Western , Carcinoma, Non-Small-Cell Lung/drug therapy , Carcinoma, Non-Small-Cell Lung/pathology , Carcinoma, Squamous Cell/drug therapy , Carcinoma, Squamous Cell/pathology , Crizotinib , Exons/genetics , Female , Follow-Up Studies , Humans , Immunoprecipitation , Isoenzymes , Lung Neoplasms/drug therapy , Lung Neoplasms/pathology , Male , Middle Aged , Neoplasm Staging , Prognosis , Protein Kinase Inhibitors/therapeutic use , Pyrazoles/therapeutic use , Pyridines/therapeutic use , Retrospective StudiesABSTRACT
OBJECTIVE: To estimate and compare the frequency of CYP1A1*2A gene polymorphisms in a Brazilian population and determine the possible contribution of these genetic variations to lung cancer risk. METHODS: The study population included 200 patients with lung cancer, and the control group consisted of 264 blood donors. Genomic DNA was obtained from peripheral blood samples. The PCR-RFLP method was used for analysis of the CYP1A1*2A gene. RESULTS: There was no statistically significant difference between the lung cancer patients and the controls in terms of the distribution of CYP1A1*2A polymorphisms (p = 0.49). A multivariate logistic regression model analysis by ethnic group revealed that, within the lung cancer group, the CYP1A1*2A genotype CC plus TC was more common among the African-Brazilian patients than among the White patients (adjusted OR = 3.19; 95% CI: 1.53-6.65). CONCLUSIONS: The CYP1A1*2A gene cannot be linked with lung cancer risk in Brazilian patients at this time. Larger epidemiologic studies are needed in order to establish whether the CC plus TC polymorphism increases the risk of lung cancer in African-Brazilians.
Subject(s)
Cytochrome P-450 CYP1A1/genetics , Lung Neoplasms/genetics , Polymorphism, Genetic , Black People/genetics , Brazil/ethnology , Disease Susceptibility , Epidemiologic Methods , Female , Genotype , Humans , Lung Neoplasms/ethnology , Male , Middle Aged , White People/geneticsABSTRACT
OBJECTIVE: To estimate and compare the frequency of CYP1A1*2A gene polymorphisms in a Brazilian population and determine the possible contribution of these genetic variations to lung cancer risk. METHODS: The study population included 200 patients with lung cancer, and the control group consisted of 264 blood donors. Genomic DNA was obtained from peripheral blood samples. The PCR-RFLP method was used for analysis of the CYP1A1*2A gene. RESULTS: There was no statistically significant difference between the lung cancer patients and the controls in terms of the distribution of CYP1A1*2A polymorphisms (p = 0.49). A multivariate logistic regression model analysis by ethnic group revealed that, within the lung cancer group, the CYP1A1*2A genotype CC plus TC was more common among the African-Brazilian patients than among the White patients (adjusted OR = 3.19; 95 percent CI: 1.53-6.65). CONCLUSIONS: The CYP1A1*2A gene cannot be linked with lung cancer risk in Brazilian patients at this time. Larger epidemiologic studies are needed in order to establish whether the CC plus TC polymorphism increases the risk of lung cancer in African-Brazilians.
OBJETIVO: Estimar e comparar a frequência do gene polimórfico CYP1A1*2A na população brasileira e determinar uma possível contribuição dessas variações genéticas no risco para câncer de pulmão. MÉTODOS: A população estudada incluiu 200 pacientes com câncer de pulmão e o grupo controle consistiu em 264 doadores de sangue. O DNA genômico foi obtido de amostras de sangue periférico. O método usado para a análise do gene CYP1A1*2A foi a PCR-RFLP. RESULTADOS: A distribuição do gene CYP1A1*2A polimórfico não foi estatisticamente diferente entre os pacientes com câncer de pulmão e os controles (p = 0,49). Uma análise multivariada utilizando-se o modelo de regressão logística por grupo étnico revelou uma maior frequência do genótipo CC + TC do gene CYP1A1*2A no grupo de pacientes afro-brasileiros do que no grupo de pacientes caucasoides com câncer de pulmão (OR ajustada = 3,19; IC95 por cento: 1,53-6,65). CONCLUSÕES: O gene CYP1A1*2A não pode ser associado ao risco de câncer de pulmão nesta amostra de pacientes. Um extenso estudo epidemiológico é necessário para estabelecer se os genótipos CC + TC aumentam o risco de câncer de pulmão em afro-brasileiros.
