ABSTRACT
DNA hypomethylation may activate oncogene transcription, thus promoting carcinogenesis and tumor development. S-adenosylmethionine (SAM) is a methyl donor in numerous methylation reactions and acts as an inhibitor of intracellular demethylase activity, which results in hypermethylation of DNA. The main objectives of this study were to determine whether DNA hypomethylation correlated with vascular endothelial growth factor-C (VEGF-C) expression, and the effect of SAM on VEGF-C methylation and gastric cancer growth inhibition. VEGF-C expression was assayed by Western blotting and RT-qPCR in gastric cancer cells, and by immunohistochemistry in tumor xenografts. VEGF-C methylation was assayed by bisulfite DNA sequencing. The effect of SAM on cell apoptosis was assayed by flow cytometry analyses and its effect on cancer growth was assessed in nude mice. The VEGF-C promoters of MGC-803, BGC-823, and SGC-7901 gastric cancer cells, which normally express VEGF-C, were nearly unmethylated. After SAM treatment, the VEGF-C promoters in these cells were highly methylated and VEGF-C expression was downregulated. SAM also significantly inhibited tumor growth in vitro and in vivo. DNA methylation regulates expression of VEGF-C. SAM can effectively induce VEGF-C methylation, reduce the expression of VEGF-C, and inhibit tumor growth. SAM has potential as a drug therapy to silence oncogenes and block the progression of gastric cancer.
Subject(s)
Animals , Humans , Male , Antineoplastic Agents/pharmacology , DNA Methylation/drug effects , Down-Regulation/drug effects , Gene Expression Regulation, Neoplastic/drug effects , S-Adenosylmethionine/pharmacology , Stomach Neoplasms/drug therapy , Vascular Endothelial Growth Factor C/metabolism , Apoptosis/drug effects , Blotting, Western , Cell Line, Tumor , Carcinogenesis/drug effects , DNA Methylation/genetics , Flow Cytometry , Gene Expression Regulation, Neoplastic/physiology , Heterografts/drug effects , Immunohistochemistry , Mice, Nude , Oncogenes/drug effects , Promoter Regions, Genetic/drug effects , Real-Time Polymerase Chain Reaction , RNA, Messenger/analysis , Stomach Neoplasms/metabolism , Vascular Endothelial Growth Factor C/drug effects , Vascular Endothelial Growth Factor C/geneticsABSTRACT
We present two acromegalic patients in which clinical and molecular data are discussed in regard to their ability to predict long term octreotide LAR® therapy response. Case reports: Patient 1: female, 36 years old at diagnosis. Basal GH and IGF-I at diagnosis were 133 ng/mL and 181 percent above the upper limit of reference values (ULRV), respectively. Growth hormone during acute test with subcutaneous octreotide decreased from 133 to 13 ng/mL. Patient started on primary octreotide LAR® therapy (20mg q28 days) and achieved biochemical parameters of disease control after 6 months. Molecular analysis of tumor fragments: gsp +; quantitative analysis of SSTR (somatostatin receptor) and DR (dopamine receptor) mRNA - SSTR2 23954; SSTR5 2407; DR2 total 17016 copies. Patient 2: male, 38 years old at diagnosis. Basal GH and IGF-I at diagnosis were 120 ng/mL and 114 percent ULRV, respectively. Patient underwent non-curative trans-sphenoidal surgery. Post-operative GH and IGF-I were 112 ng/mL and 137 percent ULRV, respectively. Growth hormone during acute test with subcutaneous octreotide decreased from 112 to 7 ng/mL. Octreotide LAR® therapy (20 mg q28 days) was then initiated. After 6 months of treatment, patient did not attain biochemical control of disease and displayed increased tumor volume. Molecular analysis of tumor fragments: gsp not done; quantitative analysis of SSTR and DR mRNA - SSTR2 416; SSTR5 3767; DR2 total 3439 copies. In conclusion, these two cases illustrate how laboratory data can be conflicting as predictors of octreotide LAR® responsiveness and how molecular analysis of tumor fragments can help explain different behaviors in clinically similar patients.
Apresentamos dois pacientes acromegálicos nos quais dados clínicos e moleculares são discutidos quanto à sua capacidade de predizer a resposta a longo prazo ao tratamento com octreotide LAR®. Relato dos casos: Paciente 1: Feminina, 36 anos de idade ao diagnóstico. GH e IGF-I ao diagnóstico 133 ng/mL e 181 por cento acima do limite superior do valor de referência (LSVR), respectivamente. GH durante o teste agudo com octreotide subcutâneo diminuiu de 133 para 13 ng/mL. Foi iniciado tratamento primário com octreotide LAR® (20 mg q28 dias) e a paciente alcançou os parâmetros bioquímicos de controle de doença depois de seis meses. Análise molecular do tumor: gsp +; análise quantitativa do mRNA de SSTR (receptores de somatostatina) e DR (receptor de dopamina) - SSTR2 23.954; SSTR5 2.407; DR2 total 17.016 cópias. Paciente 2: Masculino, 38 anos de idade ao diagnóstico. GH e IGF-I ao diagnóstico 120 ng/mL e 114 por cento LSVR, respectivamente. Paciente foi submetido à cirurgia trans-esfenoidal não-curativa. GH e IGF-I pós-operatórios 112 ng/mL e 137 por cento LSVR, respectivamente. GH durante o teste agudo diminuiu de 112 para 7 ng/mL. Foi iniciado tratamento com octreotide LAR® (20 mg q28 dias). Após seis meses o paciente não alcançou controle bioquímico e apresentou aumento do volume tumoral. Análise molecular do tumor: gsp não estudado; análise quantitativa do mRNA de SSTR e DR - SSTR2 416; SSTR5 3.767; DR2 total 3.439 cópias. Em conclusão, estes dois casos ilustram como dados laboratoriais podem ser conflitantes enquanto preditores de resposta ao tratamento com octreotide LAR® e como a análise molecular de fragmentos do tumor pode ajudar a explicar comportamentos diferentes em pacientes clinicamente semelhantes.
Subject(s)
Adult , Female , Humans , Male , Acromegaly/metabolism , Adenoma/drug therapy , Octreotide/therapeutic use , /genetics , Receptors, Somatostatin/genetics , Acromegaly/drug therapy , Adenoma/pathology , Antineoplastic Agents, Hormonal/therapeutic use , Gene Expression , Oncogenes/drug effects , Oncogenes/genetics , Pituitary Neoplasms/drug therapy , Pituitary Neoplasms/pathology , RNA, Messenger/metabolismABSTRACT
La insulina y la somatomedina C (factor insulinoide I) son esenciales para la proliferación y diferenciación de numerosos órganos y tejidos. Ellas ejercen sus efectos a través de receptores localizados en la membrana celular, los cuales son miembros de la familia de oncogenes src. Los productos proteicos de los genes de esta familia se caracterizan por poseer actividad de proteínas Kinasa específica para fosforilación de residuos de tirosina. Esta fosforilación es un mecanismo regulatorio esencial en los procesos de proliferación y diferenciación celular. Alteraciones en los productos de la familia src, incluyendo proto-oncogenes y receptores para insulina y ciertos factores de crecimiento, pueden desempeñar un papel importante en el origen y desarrollo de enfermedades crónicas graves tales como la diabetes mellitus y el cáncer