Differences in allelic distribution of two polymorphisms in the VHL-associated gene CUL2 in pheochromocytoma patients without somatic CUL2 mutations

Although the two major familial forms of pheochromocytomas, multiple endocrine neoplasia type 2 and von-Hippel-Lindau disease (VHL), have been associated with mutations of the RET and VHL genes, respectively, the molecular pathogenesis of sporadic pheochromocytomas is largely unknown. Recently, a putative tumor suppressor gene has been identified, CUL2, whose product has been shown to interact with the VHL tumor suppressor. To examine whether CUL2 plays a role in pheochromocytoma pathogenesis, we analyzed a series of 26 distinct tumor samples for mutations in the whole coding region of this gene. There were no somatic pathogenic mutations in CUL2, except for 1 sporadic tumor that had a hemizygous gene deletion. We also found 3 novel polymorphisms in the gene. One of these variants, IVS5-6C/T, as well as another previously described one, c.2057G/A, were overrepresented among the pheochromocytoma patients compared to that in a control population (P < 0.005 and P < 0.01, respectively). Although our findings suggest that CUL2 does not play a major role in the pathogenesis of pheochromocytomas, it is still unknown whether epigenetic mechanisms are involved in its inactivation in VHL-associated tumors. Furthermore, the potential role for the overrepresented alleles in the pheochromocytoma group requires further investigation.