guanylyl-imidodiphosphate and Carcinoma

The present investigation was performed in order to study the properties of abnormal membrane function related to ACTH receptor-adenylate cyclase system interaction in human ACTH-unresponsive adrenocortical cancer. Two tissues of adrenocortical cancer obtained from a patient with Cushing's syndrome (CS) and a case presenting no abnormal endocrinological findings (NF) were used for in vitro studies, comparing with three normal adrenal tissues. The addition of ACTH alone and ACTH plus 10(-6) M GppNHp did not enhance the adenylate cyclase (AC) activity in the CS and NF tissues. Relative insensitivity of AC to GTP, GppNHp, and cholera toxin was observed for the NF tissue, while the rate of response to GppNHp for the CS tissue which also showed relative insensitivity to GTP and cholera toxin was similar to that for the normal tissues. Forskolin which is reported to directly activate the catalytic unit of the AC complex increased the AC activity of both CS and NF tissues as well as that of the normal tissues. Therefore, the function of the catalytic unit itself may be rather well preserved in these tumor tissues. These results suggest that the lack of ACTH receptor at the cell membrane surface might be responsible for ACTH-unresponsiveness in the CS tissue, although an accelerated degradation of GTP could contribute to decreased activity of GTP-binding protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adenylyl Cyclases; Adrenal Cortex Neoplasms; Adrenocorticotropic Hormone; Carcinoma; Cell Membrane; Cholera Toxin; Colforsin; GTP-Binding Proteins; Guanosine Triphosphate; Guanylyl Imidodiphosphate; Humans; Receptors, Corticotropin; Receptors, Pituitary Hormone

Thyrotropin (TSH), stimulators of guanyl nucleotide regulatory protein, (sodium fluoride and guanyl-5'-yl-imido-diphosphate [Gpp(NH)p]) and a stimulator of the catalytic unit of adenylate cyclase (AC) (forskolin) were used to probe the TSH receptor-guanyl nucleotide regulatory protein-cyclase unit in normal and neoplastic thyroid tissue from 17 patients. Eleven of these patients had benign follicular adenomas and six patients had differentiated thyroid carcinomas. An 8000 X g particulate fraction that is rich in thyroid plasma membranes was prepared, and the activity of AC was determined by the conversion of alpha-32P-ATP to P32-cAMP. Thyroid neoplasms had a greater AC response to TSH than did normal thyroid tissue removed from the same patients (p less than 0.001). The AC response to NaF and Gpp(NH)p was greater in the neoplastic thyroid tissue, although in these experiments the increase was not significant. In contrast, the AC response to forskolin was comparable in normal (573 +/- 129) and neoplastic (526 +/- 132) thyroid tissue (mean +/- SEM). The effects of NaF, Gpp(NH)p, and forskolin on AC activity were additive with TSH when used at concentrations for optimal AC activity. Low concentrations of NaF and Gpp(NH)p stimulated AC activity whereas high concentrations of NaF and Gpp(NH)p assayed either together or separately inhibited AC activity. When forskolin and NaF were assayed together there was a greater than additive effect or potentiated effect on activity. Basal AC activity was increased in the presence of manganese (Mn+2) (2 mM) over magnesium (Mg+2) (2 mM) (p less than 0.001), whereas TSH-stimulated (p less than 0.01) and Gpp(NH)p-stimulated AC activity (p less than 0.05) were lower in the presence of Mn+2 than Mg+2. There was an excellent correlation between basal AC activity and AC activity in response to forskolin in both normal and neoplastic thyroid tissue, whereas there was no correlation between basal AC activity and TSH-stimulated AC activity in the thyroid neoplasms. These data suggest that the abnormality responsible for the greater AC response to TSH in neoplastic thyroid tissue is proximal to the catalytic unit of AC and most probably is due to an alteration in the guanyl nucleotide regulatory protein or in the coupling of the guanyl nucleotide regulatory protein to either the receptor or the catalytic unit of AC.(ABSTRACT TRUNCATED AT 400 WORDS)

Topics: Adenoma; Adenylyl Cyclases; Adult; Aged; Carcinoma; Colforsin; Cyclic AMP; Diterpenes; Female; Guanylyl Imidodiphosphate; Humans; Male; Middle Aged; Receptors, Cell Surface; Receptors, Thyrotropin; Sodium Fluoride; Thyroid Gland; Thyroid Neoplasms; Thyrotropin

Adenylate cyclase activity in particulate preparations of ovarian tumors from 47 women was determined by measuring the conversion of phosphorus 32-labeled adenosine triphosphate to phosphorus 32-labeled cyclic adenosine monophosphate. Ovarian cancers typically exhibited an active adenylate cyclase which was stimulated by 50 mumol/L 5'-guanylylimidodiphosphate and 10 mmol/L of sodium fluoride. This activity was comparable to that in particulates of normal postmenopausal ovaries and was independent of the class of tumor. There was no significant increase in adenylate cyclase activity in any epithelial or germinal tumor in the presence of either 250 nmol/L of human chorionic gonadotropin or 333 nmol/L human follicle-stimulating hormone. However, cyclic adenosine monophosphate production by two sex cord stromal tumors was stimulated by follicle-stimulating hormone, but not by human chorionic gonadotropin. Follicle-stimulating hormone stimulated a threefold increase in activity in the granulosa-theca cell tumor, with an activation constant (57 nmol/L) similar to that in follicle-stimulating hormone-responsive rat ovaries. Prostaglandin E1 (50 mumol/L) increased cyclic adenosine monophosphate production by epithelial tumors more than twofold. These data suggest that sex cord stromal tumors, unlike the more common epithelial tumors, can be modulated directly by gonadotropin.

Topics: Adenylyl Cyclases; Animals; Carcinoma; Chorionic Gonadotropin; Cyclic AMP; Female; Follicle Stimulating Hormone; Gonadotropins; Guanylyl Imidodiphosphate; Humans; Luteinizing Hormone; Middle Aged; Ovarian Neoplasms; Ovary; Prostaglandins E; Rats; Sodium Fluoride; Stimulation, Chemical