Development of an experimental ovarian tumor: immunocytochemical analysis.
OBJECTIVE
The aim of the present work was to study whether immunocytochemical parameters present in the normal ovary were altered after tumor development under high gonadotropin levels.


METHODS
Ovarian tumors (luteoma): castrated female rats had an ovary grafted into the spleen; tumors were left to develop for 1, 2, 3 or 7 months. The presence of apoptotic cells (TUNEL method) and the expression of proliferating cell nuclear antigen (PCNA), gap junction protein (Cx43), steroidogenic acute regulatory protein (StAR), aromatase and synaptosome-associated protein of 25 kDa (SNAP-25) were determined by immunocytochemistry. Some of these findings were confirmed by RT-PCR (Cx43, StAR, SNAP-25). Inhibin subunit mRNAs were investigated by Northern blot.


RESULTS
PCNA staining of tumors was mainly found in granulosa cells of transforming follicles and was absent from luteinized follicles. A nearly complete absence of apoptosis was observed. Cx43 was mainly found in follicles, while it was very weakly expressed or absent in luteinized follicles. StAR protein expression, indicating active steroidogenesis, was demonstrated only in luteinized follicles and in thecal cells, but was absent from granulosa cells. Aromatase immunoreactivity was very intense in granulosa and also present in luteal cells. Membrane-associated and cytoplasmic SNAP-25 immunostaining was determined in patches of endocrine cells in the follicles, as well as in the luteinized follicles. The expression of mRNAs for Cx43, StAR and SNAP-25 (RT-PCR) and inhibin subunits (Northern blots) were confirmed in 1-, 3- and 7-month-old tumors.


CONCLUSIONS
These results indicated that luteoma most likely develop from unruptured follicles by hypertrophy and proliferation of follicular cells. Circulating gonadotropins seem to play a fundamental role in maintaining the expression of proteins typically expressed in normal ovary, while avoiding apoptosis in this tissue.
Sorianello
E
E
Instituto de Biología y Medicina Experimental, Department of Physiology, University of Buenos Aires Medical School, Buenos Aires, Argentina.
Fritz
S
S
Beyer
C
C
Hales
D B
DB
Mayerhofer
A
A
Libertun
C
C
Lux-Lantos
V
V
D000818:Animals; D017209:Apoptosis; D001141:Aromatase / Q000032:analysis; D015152:Blotting, Northern; D002455:Cell Division; D018031:Connexin 43 / Q000032:analysis / Q000235:genetics; D004195:Disease Models, Animal; D005260:Female; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D018311:Luteoma / Q000737:chemistry; D008565:Membrane Proteins / Q000032:analysis / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000032:analysis / Q000235:genetics; D010051:Ovarian Neoplasms / Q000737:chemistry*; D010052:Ovariectomy; D010053:Ovary / Q000637:transplantation; D010750:Phosphoproteins / Q000032:analysis / Q000235:genetics; D018809:Proliferating Cell Nuclear Antigen / Q000032:analysis; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013154:Spleen / Q000737:chemistry; D050825:Synaptosomal-Associated Protein 25; D013997:Time Factors; D014446:Tyrosine 3-Monooxygenase / Q000032:analysis; D000098682:Steroidogenic Acute Regulatory Protein
D018031:Connexin 43; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D010750:Phosphoproteins; D018809:Proliferating Cell Nuclear Antigen; D012333:RNA, Messenger; C494210:Snap25 protein, rat; D050825:Synaptosomal-Associated Protein 25; D000098682:Steroidogenic Acute Regulatory Protein; D001141:Aromatase; D014446:Tyrosine 3-Monooxygenase