Clonal analysis of sporadic pancreatic endocrine tumours

The clonal composition of 34 benign and malignant sporadic pancreatic endoc rine tumours (PETs) of female patients was studied using a sensitive polyme rase chain reaction (PCR)-mediated non-isotopic clonality analysis, which i s based on the inactivation patterns of polymorphic X-linked genes encoding the androgen receptor (AR) and phosphoglycerate kinase (PGK-I) proteins. P redigestion of DNA with the methylation-sensitive restriction endonuclease Hpa II permitted selective PCR amplification of the methylated (uncleaved) allele. Amplification was successful in 27 of 34 samples, Twenty patient sa mples were heterozygous for the AR microsatellite region or Bst XI polymorp hic site of the PGK-I gene, permitting analysis of clonality. A monoclonal pattern of X-chromosome inactivation was found in 7 of 20 PETs (35 per cent ), since DNA pretreatment with Hpa II blocked amplification of one of the t wo AR or PGK-1 alleles, One additional tumour exhibited an oligoclonal inac tivation pattern and two others a loss of heterozygosity (LOH) at the AR lo cus, indicative of monoclonality. A random pattern of X-chromosome inactiva tion and polyclonal cellular composition was observed in the remaining ten PETs (50 per cent), When comparing informative benign and malignant PETs, o nly 2/7 (29 per cent) benign tumours showed a monoclonal pattern and 8/13 ( 61 per cent) malignant tumours a monoclonal (5), oligoclonal (1), or LOH (2 ) pattern. The clonal composition of PETs was not associated with a particu lar growth pattern, proliferation index or immunohistochemical expression p attern, These findings suggest that PETs might initially represent poly-/ol igoclonal neoplastic lesions which are eventually outgrown by a single, mor e aggressive cell clone with the potential for invasive growth and metastat ic spread, (C) 1998 John Wiley & Sons, Ltd.