Expression of thyrotropin-releasing hormone by human melanoma and nevi.
OBJECTIVE
Thyrotropin-releasing hormone (TRH) is a tripeptide hormone produced by the hypothalamus in response to hypothyroidism. RNA transcripts for the TRH prohormone have recently been described in melanoma cell lines. To expand these findings, we have examined cultured melanoma cells and melanocytes, human melanoma tumors, and nevi for the expression of TRH.


METHODS
Five melanoma cell lines were analyzed by reverse transcription-PCR/Southern blotting for preproTRH message. The same melanoma lines and two melanocyte lines were examined by immunocytochemistry for TRH protein expression and for growth response to exogenous TRH. Immunohistochemistry was used to test for TRH protein in sections of 19 melanomas, 33 dysplastic nevi, and 27 benign nevi.


RESULTS
TRH message and protein were detected in all melanoma cell lines examined. Melanocytes were also found to express TRH protein. Four of the five melanoma cell lines but neither melanocyte line responded with a increase in proliferation to low concentrations of exogenous TRH. TRH immunoreactivity was observed in 12 of 19 melanomas (63%), 23 of 33 (69.7%) dysplastic nevi, and 14 of 27 (51.9%) benign nevi. Expression in dysplastic nevi was significantly greater than in benign nevi. Upon separate analysis of nevi from melanoma patients, the difference between dysplastic and benign nevi was even more significant. However, in healthy individuals, no difference between dysplastic and benign nevi was observed. Furthermore, dysplastic nevi from melanoma patients had a significantly higher percentage of TRH-positive cells when compared with healthy individuals.


CONCLUSIONS
TRH is commonly expressed by melanomas and dysplastic nevi and may function as a melanoma autocrine growth factor. The presence of TRH in dysplastic nevi may be predictive for the development of melanoma. Our findings have significant clinical and biological implications for future research into the early stages of melanoma initiation and progression.
Department of Bioimmunotherapy, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA. jaellerh@mail.mdanderson.org
Julie A
JA
Ellerhorst
Aresu A
AA
Naderi
Marilyn K
MK
Johnson
Pauline
P
Pelletier
Victor G
VG
Prieto
A Hafeez
AH
Diwan
Marcella M
MM
Johnson
Debra C
DC
Gunn
Sandra
S
Yekell
Elizabeth A
EA
Grimm
D045744:Cell Line, Tumor; D017931:DNA Primers; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008545:Melanoma / Q000235:genetics* / Q000473:pathology; D009506:Nevus / Q000235:genetics* / Q000473:pathology; D011237:Predictive Value of Tests; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012878:Skin Neoplasms / Q000235:genetics* / Q000473:pathology; D013973:Thyrotropin-Releasing Hormone / Q000032:analysis / Q000235:genetics*
D017931:DNA Primers; D013973:Thyrotropin-Releasing Hormone