Mutations in the genes encoding
succinate dehydrogenase (SDH) have been associated with susceptibility to
pheochromocytoma. However, few reports have examined the level of SDH mRNAs expression. In this study, we examined the level of expression of mRNAs encoding SDHB, SDHC, and SDHD in
pheochromocytoma,
pheochromocytoma subgroups, and normal adrenal gland, and compared the expression of these genes to the level of expression of related genes in the same tissues. The mean relative level of expression of SDHB, SDHC, SDHD and VHL
mRNA was 28.7+/-6.2%, 16.6+/-4.8%, 214+/-47.5% and 25.9+/-8.2%, respectively, in
pheochromocytoma tissues compared to normal adrenal gland. Furthermore, the mean relative level of the RET proto-oncogene
mRNA was 707+/-149% in
pheochromocytoma compared to normal adrenal gland. The level of expression of the SDH genes was highly correlated in each individual sample (P<0.0001). The level of expression of the SDH mRNAs correlated with the level of VHL
mRNA (P<0.0001), but not with the level of RET
mRNA. The level of SDH mRNAs expression also correlated with the expression of phenylethanolamine N-methyl
transferase (PNMT), an
adrenaline synthesizing
enzyme (P<0.01), which may explain the correlation between SDH expression and
adrenaline content (P<0.05). The level of SDH mRNAs expression correlated strongly with the expression of
VEGF mRNA (P<0.0001). In
multiple endocrine neoplasia (
MEN) 2a, the expression of the SDH genes and VHL
mRNA was significantly higher than that observed in adrenal or
extra-adrenal pheochromocytoma. The expression of the
corticotropin-releasing hormone (CRH)
mRNA was significantly higher in
extra-adrenal pheochromocytoma than in adrenal
pheochromocytoma or
MEN2a. Thus,
tumor-specific gene expression exists in
pheochromocytoma, which may explain the characteristics of the
tumor.