Human Thyroid Cancer: Membrane Thyrotropin Binding and Adenylate Cyclase Activity

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Abstract
To characterize the relationship of the TSH receptor-adenylate cyclase system to differentiation in human thyroid cancers, adenylate cyclase and TSH binding were studied in membranes from primary and metastatic thyroid carcinomas of varying histological types (n = 33) and normal thyroids (n = 12). Membranes from differentiated carcinomas (n = 23) exhibit wide patient to patient variability; some membranes show entirely normal adenylate cyclase and TSH-binding characteristics, and other membranes exhibit decreased TSH stimulation of adenylate cyclase which is accompanied by either a normal or decreased TSH-binding site concentration. With respect to the TSH-binding site concentration and TSH stimulation of the adenylate cyclase, the well differentiated carcinomas are not significantly different from normal thyroids, whereas the moderately differentiated and the papillary carcinomas are significantly different (P < 0.001 and P < 0.001, respectively). Membranes from undifferentiated carcinomas (n = 5) and those from medullary carcinomas (n = 5) are characterized by an absence of both TSH binding and TSH stimulation of the adenylate cyclase. In conclusion, while a general relationship exists between the impairment of TSH responsiveness and the dedifferentiation process, no pattern of membrane alteration is specific for any histological type.