Expression of vascular endothelial growth factor (VEGF) in human thyroid neoplasms

Vascular endothelial growth factor (VEGF), also known as vascular permeabil ity factor (VPF), is an angiogenic factor that plays important roles in tum or growth. Angiogenesis studies on VEGF deal with various types of malignan t tumors, but very little is known about the role or significance of VEGF i n human thyroid neoplasms. Therefore, in the current study, we determined w hether VEGF is found in normal and neoplastic thyroids and whether its expr ession is altered in different histological types of thyroid neoplasms. Rev erse-transcription polymerase chain reaction (RT-PCR) analysis showed that all specimens of thyroid tumors expressed bands corresponding to 121-, 165- , and 189-amino acid forms of VEGF. Northern blot analysis showed an increa se in VEGF mRNA levels in neoplastic tissues in comparison with normal thyr oid samples. By nonisotopic in situ hybridization, most of the tumor cells in follicular adenomas expressed VEGF mRNA, whereas VEGF mRNA expression wa s identified only in epithelium of isolated follicles in normal thyroid tis sues. In papillary thyroid carcinomas, an intense labeling with VEGF probe was often found in overlying tumor cells of neoplastic papillae. VEGF expre ssion was distinctly intensified in undifferentiated carcinoma cells that w ere immediately adjacent to necrotic foci. The immunohistochemical localiza tions of VEGF protein were comparable to the localization of VEGF mRNA. In conclusion, our results suggest that the histological types of thyroid tumo r may determine the vascular pattern through a paracrine mechanism involvin g (C) 1999 by W.B. Saunders Company.