CLONAL COMPOSITION OF HUMAN ADRENOCORTICAL NEOPLASMS

The mechanisms of tumorigenesis of adrenocortical neoplasms are still not understood. Tumor formation may be the result of spontaneous trans formation of adrenocortical cells by somatic mutations. Another factor stimulating adrenocortical cell growth and potentially associated wit h formation of adrenal adenomas and, less frequently, carcinomas is th e chronic elevation of proopiomelanocortin-derived peptides in disease s like ACTH-dependent Cushing's syndrome and congenital adrenal hyperp lasia. To further investigate the pathogenesis of adrenocortical neopl asms, we studied the clonal composition of such tumors using X-chromos ome inactivation analysis of the highly polymorphic region Xcen-Xp11.4 with the hybridization probe M27 beta, which maps to a variable numbe r of tandem repeats on the X-chromosome. In addition, polymerase chain reaction amplification of a phosphoglycerokinase gene polymorphism wa s performed. After DNA extraction from tumorous adrenal tissue and nor mal leukocytes in parallel, the active X-chromosome of each sample was digested with the methylation-sensitive restriction enzyme HpaII. A s econd digestion with an appropriate restriction enzyme revealed the po lymorphism of the region Xcen-Xp11.4 and the phosphoglycerokinase locu s. Whereas in normal polyclonal tissue both the paternal and maternal alleles are detected, a monoclonal tumor shows only one of the parenta l alleles. A total of 21 female patients with adrenal lesions were ana lyzed; 17 turned out to be heterozygous for at least one of the loci. Our results were as follows: diffuse (n = 4) and nodular (n = 1) adren al hyperplasia in patients with ACTH-dependent Cushing's syndrome, pol yclonal pattern; adrenocortical adenomas (n = 8), monoclonal (n = 7), as well as polyclonal (n = 1); adrenal carcinomas (n = 3), monoclonal pattern. One metastasis of an adrenocortical carcinoma showed a patter n most likely due to tumor-associated loss of methylation. In the spec ial case of a patient with bilateral ACTH-independent macronodular hyp erplasia, diffuse hyperplastic areas and a small nodule showed a polyc lonal pattern, whereas a large nodule was monoclonal. We conclude that most adrenal adenomas and carcinomas are monoclonal, whereas diffuse and nodular adrenal hyperplasias are polyclonal. The clonal compositio n of ACTH-independent massive macronodular hyperplasia seems to be het erogeneous, consisting of polyclonal and monoclonal areas.