Expression of tyrosinase-related protein 2/DOPAchrome tautomerase in the retinoblastoma.
Tyrosinase-related protein 2 (TRP-2), also known as DOPAchrome tautomerase, is an enzyme in melanin biosynthesis and may play an important role in detoxification of a metabolite derived from DOPA. TRP-2 is expressed in melanocytes of neural crest origin and retinal pigment epithelium (RPE), derived from the optic cup. TRP-2 has been established as an early differentiation marker for melanoblasts and RPE. It is therefore of significance to study the regulation of TRP-2/DOPAchrome tautomerase expression. Here we show that TRP-2 mRNA is expressed in Y79 human retinoblastoma cell line, derived from a primitive multipotential retinal cell. Retinoblastoma is the common primary intraocular tumor of childhood. Basal expression levels in Y79 retinoblastoma cells of TRP-2 mRNA and protein are comparable to those in melanoma cells, whereas mRNA for tyrosinase, the rate-limiting enzyme in melanogenesis, is undetectable in retinoblastoma cells. Transient transfection assays showed that the TRP-2 gene promoter efficiently directs the reporter gene expression in retinoblastoma cells as it does in melanoma cells. Moreover, the expression of TRP-2 mRNA was induced by retinoic acid in retinoblastoma cells but not noticeably affected by forskolin, a cAMP-elevating reagent, whereas in melanoma cells its expression was induced by forskolin but not by retinoic acid. These results suggest a difference in the regulation of TRP-2 expression between retinoblastoma and melanoma cells. Moreover, TRP-2 mRNA is expressed in the excised retinoblastoma specimens, as assessed by RT-PCR. The present study shows unexpected features of TRP-2 and may enhance our understanding of the pathophysiology of retinoblastoma.
Udono
T
T
Department of Molecular Biology and Applied Physiology, Tohoku University School of Medicine, Aoba-ku, Sendai, Miyagi 980-8575, Japan.
Takahashi
K
K
Yasumoto
K
K
Yoshizawa
M
M
Takeda
K
K
Abe
T
T
Tamai
M
M
Shibahara
S
S
D005576:Colforsin / Q000494:pharmacology; D015870:Gene Expression; D017930:Genes, Reporter; D006801:Humans; D008545:Melanoma / Q000201:enzymology; D014442:Monophenol Monooxygenase / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D019572:Retinal Neoplasms / Q000201:enzymology*; D012175:Retinoblastoma / Q000201:enzymology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014212:Tretinoin / Q000502:physiology; D014407:Tumor Cells, Cultured
D012333:RNA, Messenger; D005576:Colforsin; D014212:Tretinoin; D014442:Monophenol Monooxygenase