RESUMO
BACKGROUND/AIM: Genomic imprinting is a chromosomal modification causing differential expression of maternal and paternal alleles. Loss of imprinting (LOI) of IGF-II and H19 has been suggested to be an early oncogenic event in cancerogenesis. Aim of the present study was to describe the status of IGF-II and H19 imprinting in adult human pancreatic tissues. METHODS: Allele-specific gene expression was studied using RNA and DNA from human pancreatic cancer, chronic pancreatitis, and normal pancreas tissues heterozygous for ApaI (IGF-II) or RsaI (H19) restriction fragment length polymorphism. Reverse-transcriptase polymerase chain reaction products were digested with either ApaI or RsaI and analyzed on agarose gels to study the status of allelic expression. The expression level of H19 and IGF-II was studied on Northern blots or by polymerase chain reaction. RESULTS: H19 was imprinted in normal pancreas and in chronic pancreatitis. H19 LOI was observed in 1 of 4 informative cancer tissues and was not associated with increased H19 transcript levels. Biallelic expression of IGF-II was found in 6 of 10 informative cancer tissues and in 6 of 9 informative normal tissues. In chronic pancreatitis, the IGF-II gene was imprinted in all informative samples. IGF-II mRNA was not overexpressed in the tissues showing LOI. CONCLUSION: Low frequencies of H19 LOI and the lack of correlation between biallelic expression and overexpression observed for both H19 and IGF-II suggest that LOI of H19 and IGF-II is not a relevant oncogenic factor during human exocrine pancreatic cancerogenesis.
Assuntos
Genes Supressores de Tumor/genética , Impressão Genômica , Fator de Crescimento Insulin-Like II/genética , Proteínas Musculares/genética , Pâncreas/metabolismo , Neoplasias Pancreáticas/genética , Pancreatite/genética , RNA não Traduzido , Adenocarcinoma/genética , Adulto , Alelos , Northern Blotting , Regulação Neoplásica da Expressão Gênica , Heterozigoto , Humanos , Polimorfismo de Fragmento de Restrição , RNA Longo não Codificante , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
HISTORY AND CLINICAL FINDINGS: A 71-year-old woman was admitted with the suspected diagnosis of pancreatic carcinoma. As a child she had had repeated attacks of abdominal pain of undetermined cause. When aged 48 years she had developed diabetes mellitus. Her now 42-year-old daughter had from the age of 9 years suffered from repeated attacks of acute pancreatitis that had finally led to chronic pancreatitis. The patient's 15-year-old grandchild was having recurrent bouts of abdominal pain. INVESTIGATIONS: Imaging procedures revealed calcifications in the pancreas and an infiltrating space-occupying lesion, about 3 cm in diameter, in the head of the pancreas with lymph node and liver metastases. Cytological analysis of material aspirated from the space-occupying mass showed typical findings of ductal pancreatic carcinoma. FURTHER TESTS, TREATMENT AND COURSE: At first the patient's course was not typical for a genetically-determined disease, but the family history raised the suspicion of hereditary pancreatitis. A genetic test (Afl-III-RFLP test) demonstrated the mutation Arg 117 His in the cationic trypsinogen gene in all diseased or symptomatic family members. The patient died of the complications of the pancreatic cancer. CONCLUSION: Genetic tests are valuable in the diagnosis of hereditary pancreatitis, because the increased cancer risk can be met by frequent examinations in affected family members.
