Frequent loss of heterozygosity at 6q in pheochromocytoma

Multiple genetic alterations have been associated with pheochromocytoma (PCC). Most PCCs are sporadic, but they also occur in inherited tumor syndromes, including von Hippel-Lindau disease. Although the etiology of most inherited PCCs is well documented, little is known about the etiology of sporadic tumors. Mutations of those genes that harbor germ-line mutations in familial cases cover only 10% to 15% of somatic mutations in sporadic PCCs. A previous cytogenetic analysis indicated frequent loss of 6q in sporadic PCCs. We therefore investigated in detail 18 PCCs using 22 microsatellite markers spanning 6q to search for the presence of allele deletions and identify specific regions likely to contain tumor suppressor genes involved in PCC. Moreover, we sought to compare PCC with capillary hemangioblastoma, another von Hippel-Lindau disease-associated tumor that we previously found to harbor frequent loss of heterozygosity (LOH) at 6q. Our study revealed a high frequency (13/18; 72%) of overall 6q LOH in PCCs. Loss of heterozygosity at 6q was observed in 6 benign (6/9; 67%) and 7 borderline (7/9; 78%) tumors. We identified 2 regions where LOH or allelic imbalance was common (ie, 6q14 [9/18; 50%] and 6q23-24 [6/18; 33%]). We further focused the search using markers specific for the ZAC1 gene region located at 6q24-25. Altogether, for all 6q23-25 markers, including the ZAC1-specific ones, LOH or allelic imbalance was observed in 50% (9/18) of the PCCs. Similar to our findings for capillary hemangioblastomas, our data for the first time suggest that one or several tumor suppressor genes located at 6q, particularly at 6q23-24, may play a role in the tumorigenesis of PCCs.