Increased activity of type I regulatory subunit of cyclic adenosine 3',5'-monophosphate-dependent protein kinase in estrogen-induced pituitary tumors
| Autor: | Gerardo Piroli, Alejandro F. De Nicola, Omar Pignataro |
|---|---|
| Rok vydání: | 1992 |
| Předmět: |
Cancer Research
medicine.medical_specialty Pituitary gland Immunoprecipitation Protein subunit Ovariectomy Biology Chromatography DEAE-Cellulose chemistry.chemical_compound Internal medicine medicine Cyclic AMP Animals Pituitary Neoplasms Protein kinase A Diethylstilbestrol Analysis of Variance Estradiol Pituitary tumors Intracellular Signaling Peptides and Proteins Radioimmunoassay Hypertrophy medicine.disease Adenosine Precipitin Tests Rats Inbred F344 Rats Endocrinology medicine.anatomical_structure Oncology chemistry Pituitary Gland Estradiol benzoate Female Carrier Proteins Protein Kinases medicine.drug |
| Zdroj: | Journal of the National Cancer Institute. 84(20) |
| ISSN: | 0027-8874 |
| Popis: | BACKGROUND Previous studies have shown that binding of [3H]cyclic adenosine 3',5'-monophosphate (cAMP) is increased in cytosol of diethylstilbestrol (DES)-induced pituitary tumors. In tumor cells, the cAMP-binding proteins that stimulate cell proliferation have been shown to predominate over those that inhibit it. PURPOSE This study was designed to determine the type of regulatory subunit (R) of cAMP-dependent protein kinase (PK) responsible for this binding by determining the type of subunit that is increased in DES-induced pituitary tumors. METHODS Experiments were carried out on three groups of Fischer 344 rats: 1) rats with DES-induced pituitary tumors, 2) ovariectomized rats receiving short-term estrogen treatment with estradiol benzoate (E2) for 4 days, and 3) ovariectomized control rats. We performed immunoprecipitation of RI and RII subunits with polyclonal antibodies in pituitary cytosol (direct method) or after separation of subunits by DEAE-cellulose chromatography (indirect method). The concentration of cAMP was also quantified by radioimmunoassay in pituitaries from the three groups. RESULTS Direct immunoprecipitation with RI antibody demonstrated a statistically significant increase in [3H]cAMP bound to RI in rats receiving E2 for 4 days over that for control rats and an even more significant increase in rats with DES-induced pituitary tumors. There was little change in the nucleotide [3H]cAMP bound to RII. Immunoprecipitation of the eluted fractions after chromatography demonstrated an RI subunit in peaks 1 and 2, whereas RII was contained almost exclusively in peak 2. After chromatography (indirect method), immunoprecipitation with RI and RII antibody indicated an overall increase in the level of binding to RI protein in tumors. Levels of cAMP in DES-induced pituitary tumors were also high compared with levels in controls or in glands from estrogen-treated rats. CONCLUSIONS In DES-induced pituitary tumors, cAMP may be preferentially bound to one isozyme of PK, which supports current theories that cell proliferation and tumor growth correlate with high expression of the RI subunit. IMPLICATIONS We plan studies to investigate the effects on tumor growth of the site-selective analogue 8-chloro-cAMP, which binds to RII and causes the elevated levels of the RI subunit of the tumor cells to return to normal levels. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|