Deletion at 3p25.3-p23 is frequently encountered in endocrine pancreatic tumours and is associated with metastatic progression.

For several reasons, chromosome 3p is thought to be involved in the pathogenesis of sporadic endocrine pancreatic tumours (EPTs): von Hippel-Lindau's disease (VHL gene at 3p25.5) is associated with EPTs; 3p is frequently involved in solid human tumours; and comparative genomic hybridization has identified frequent losses at 3p in EPTs. This study investigated 99 benign and malignant tumours, including 20 metastases, from 82 patients, by microsatellite loss of heterozygosity (LOH) analysis and fluorescence in situ hybridization (FISH) in order to evaluate the importance of chromosome 3p deletions in the molecular pathogenesis and biological behaviour of EPTs, to elaborate a common region of deletion, and to narrow down putative tumour suppressor gene loci. Allelic losses of 3p were found in 58/99 (58.6%) of tumours in 45/82 (54.9%) patients; analysis of seven microsatellite markers (3p26-p21) revealed a common region of LOH at 3p25.3-p23. The LOH frequency was significantly higher in malignant than in benign neoplasms (70.2% versus 28.0%; p=0.001). In addition, a strong correlation was found between the loss of alleles on chromosome 3p and clinically metastatic disease (LOH of 73.7% in metastasizing versus 41.5% in non-metastasizing tumours; p=0.008). EPTs from these patients showed a tendency towards losing large parts or the entire short arm of chromosome 3 with tumour progression. Furthermore, FISH analysis revealed complete loss of chromosome 3 in ten out of 37 EPTs (27%). These results indicate that a putative tumour suppressor gene at 3p25.3-p23 may play a role in the oncogenesis of sporadic EPTs and that losses of larger centromeric regions are associated with metastatic progression.

Genetic differences in endocrine pancreatic tumor subtypes detected by comparative genomic hybridization.

The molecular pathogenesis as well as histogenesis of endocrine pancreatic tumors (EPTs) is not well understood, and the clinical behavior of EPTs is difficult to predict using current morphological criteria. Thus, more accurate markers of risk and better understanding of tumor initiation and progression are needed to allow a precise classification of EPTs. We have studied 44 benign and malignant EPTs by comparative genomic hybridization to correlate the overall number of genetic alterations with clinical and histopathological parameters and to identify chromosomal regions which might harbor genes involved in EPT pathogenesis and progression. Aberrations were found in 36 EPTs, and chromosomal losses (mean, 5.3) were slightly more frequent than gains (mean, 4. 6). The most frequent losses involved Y (45% of male EPTs), 6q (39%), 11q (36%), 3p, 3q, 11p (each 30%), 6p (27%), and 10q and Xq (each 25%), whereas most common gains included 7q (43%), 17q (41%), 5q and 14q (each 32%), 7p, 9q, 17p, 20q (each 27%), and 12q and Xp (each 25%). A correlation was found between the total number of genetic changes per tumor and both tumor size and disease stage. In particular, losses of 3p and 6 and gains of 14q and Xq were found to be associated with metastatic disease. Furthermore, characteristic patterns of genetic changes were found in the various EPT subtypes, eg, 6q loss in malignant insulinomas, indicating that these groups might evolve along genetically different pathways. The highlighted genetic aberrations, including the newly found involvement of 6q losses and sex chromosome alterations, should stimulate the further analysis of these chromosomal regions, which may lead to the discovery of novel genes important in the tumorigenesis and evolution of EPTs.

Analysis of genomic alterations in sporadic adrenocortical lesions. Gain of chromosome 17 is an early event in adrenocortical tumorigenesis.

Genetic changes underlying the tumorigenesis of sporadic adrenocortical tumors are poorly characterized. To search for characteristic genomic imbalances involved in adrenocortical tumors, we examined 41 adrenocortical lesions (12 carcinomas, 23 adenomas, and 6 hyperplasias) by comparative genomic hybridization. Our results show that genetic alterations are more frequent in malignant than in benign lesions and that they rarely occur in hyperplastic lesions. The most frequent DNA copy number changes in adrenocortical carcinomas included losses of 1p21-31, 2q, 3p, 3q, 6q, 9p, and 11q14-qter, as well as gains and amplifications of 5q12, 9q32-qter, 12q, and 20q. The genomic aberrations prevalently occurring in adrenocortical adenomas were gains of 17q, 17p, and 9q32-qter. Gains found in 2 of 6 adrenocortical hyperplastic lesions involved chromosome 17 or 17q only. These data indicate that oncogenes determining the early tumorigenesis of adrenocortical tumors may exist on chromosome 17 and that the number of genomic alterations is closely associated with tumor behavior in adrenocortical tumors.

Mutations and allelic deletions of the MEN1 gene are associated with a subset of sporadic endocrine pancreatic and neuroendocrine tumors and not restricted to foregut neoplasms.

Endocrine pancreatic tumors (EPT) and neuroendocrine tumors (NET) occur sporadically and rarely in association with multiple endocrine neoplasia type 1 (MEN1). We analyzed the frequency of allelic deletions and mutations of the recently identified MEN1 gene in 53 sporadic tumors including 30 EPT and 23 NET (carcinoids) of different locations and types. Allelic deletion of the MEN1 locus was identified in 18/49 (36.7%) tumors (13/30, 43.3% in EPT and 5/19, 26.3% in NET) and mutations of the MEN1 gene were present in 8/52 (15.3%) tumors (4/30 (13.3%) EPT and 4/22 (18.1%) NET). The somatic mutations were clustered in the 5' region of the coding sequence and most frequently encompassed missense mutations. All tumors with mutations exhibited a loss of the other allele and a wild-type sequence of the MEN1 gene in nontumorous DNA. In one additional patient with a NET of the lung and no clinical signs or history of MEN1, a 5178-9G-->A splice donor site mutation in intron 4 was identified in both the tumor and blood DNA, indicating the presence of a thus far unknown MEN1 syndrome. In most tumor groups the frequency of allelic deletions at 11q13 was 2 to 3 times higher than the frequency of identified MEN1 gene mutations. Some tumor types, including rare forms of EPT and NET of the duodenum and small intestine, exhibited mutations more frequently than other types. Furthermore, somatic mutations were not restricted to foregut tumors but were also detectable in a midgut tumor (15.2% versus 16.6%). Our data indicate that somatic MEN1 gene mutations contribute to a subset of sporadic EPT and NET, including midgut tumors. Because the frequency of mutations varies significantly among the investigated tumor subgroups and allelic deletions are 2 to 3 times more frequently observed, factors other than MEN1 gene inactivation, including other tumor-suppressor genes on 11q13, may also be involved in the tumorigenesis of these neoplasms.