Molecular genetics of malignant insulinoma.
Malignant insulinoma is an rare form of cancer with poor prognosis and a reported 5-year survival of 35%. Relatively little is known about the etiology of this disease or of the oncogenes and tumor suppressor genes that participate in its genesis and progression. To address this issue, several protooncogenes, including K-ras, N-ras, erbB-2, erbB-3,c-myc, c-fos, c-jun were examined. Also analyzed was the expression of the growth factors TGF-alpha, EGF, and insulin as well as the EGF receptor (EGF-R), p53 and the putative anti-metastasis gene nm23-H1. These were examined in malignant insulinomas, benign insulinomas, pancreatic B cell hyperplasias and in normal endocrine pancreas. Normal endocrine pancreas showed moderate immunoreaction for c-myc and a strong reaction for insulin. All other parameters were negative. Benign pancreatic B cell hyperplasias were slightly or moderately positive for N-ras and TGF-alpha, and were weakly positive for EGF-R. They were strongly positive for c-myc and insulin. In malignant insulinomas there was strong immunoreaction for c-myc, TGF-alpha, N-ras, K-ras and p53. Insulin reaction was moderate or strong. Molecular genetic studies have been performed for the presence of activating point mutations in codon 12 of the c-K-ras oncogene. Mutations were detected using primer-mediated, mutant-enriched, polymerase chain reaction-restriction fragment length polymorphism analysis and were further characterized by allele-specific oligonucleotide hybridization. Four out of six patients with malignant insulinoma and two out of eight patients with benign insulinoma harbored K-ras point mutations at codon 12. All patients with mutated K-ras oncogene also had elevated levels of p53 protein as well as c-myc and TGF-alpha. In one extremely malignant case we found concomitant mutation at codon 12 of K-ras and codon 61 of the N-ras gene. Our data are consistent with the idea that malignant progression is accompanied by the progressive accumulation of multiple genetic lesions and suggest that activation of myc, TGF-alpha and ras genes may be early events in the development of insulinoma.
Pavelic
K
K
Department of Molecular Medicine, Ruder Boskovic Institute, Zagreb, Croatia.
Hrascan
R
R
Kapitanovic
S
S
Vranes
Z
Z
Cabrijan
T
T
Spaventi
S
S
Korsic
M
M
Krizanac
S
S
Li
Y Q
YQ
Stambrook
P
P
Gluckman
J L
JL
Pavelic
Z P
ZP
D000328:Adult; D000368:Aged; D001483:Base Sequence; D004252:DNA Mutational Analysis; D017931:DNA Primers; D005091:Exons; D005260:Female; D015870:Gene Expression; D016259:Genes, myc; D016158:Genes, p53; D011905:Genes, ras; D006133:Growth Substances / Q000096:biosynthesis*; D006801:Humans; D006965:Hyperplasia; D007150:Immunohistochemistry; D007340:Insulinoma / Q000235:genetics* / Q000473:pathology; D007515:Islets of Langerhans / Q000378:metabolism / Q000473:pathology; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D020559:Monomeric GTP-Binding Proteins; D054778:NM23 Nucleoside Diphosphate Kinases; D009701:Nucleoside-Diphosphate Kinase; D010182:Pancreatic Diseases / Q000235:genetics / Q000473:pathology; D010190:Pancreatic Neoplasms / Q000235:genetics* / Q000473:pathology; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D011519:Proto-Oncogenes; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics*; D016211:Transforming Growth Factor alpha / Q000096:biosynthesis
D017931:DNA Primers; D006133:Growth Substances; D054778:NM23 Nucleoside Diphosphate Kinases; D014157:Transcription Factors; D016211:Transforming Growth Factor alpha; C517938:NME1 protein, human; D009701:Nucleoside-Diphosphate Kinase; D020559:Monomeric GTP-Binding Proteins