Evidence for the Presence of Tumor Peptides with Corticotropin-Releasing-Factor-like Activity in the Ectopic ACTH Syndrome

Abstract

Evidence was found for the existence of four tumor peptides with corticotropin-releasing-factor-like (CRF) activity, two isolated from a pancreatic tumor (P-CRF-1, P-CRF-2) and two from the primary tumor and metastases of an oat-cell carcinoma (L-CRF-1, L-CRF-2). Tumor tissue was extracted for ACTH, and both tumors were demonstrated to certain ectopic ACTH. A peptide similar in size to ACTH and another, smaller than vasopressin, were isolated from each tumor. All four fractions appeared to be homogeneous on high-voltage electrophoresis at pH 6.5. Assays in hypophysectomized rats demonstrated that these peptides were devoid of direct adrenal-stimulating activity. CRF assays in the rat treated with chlorpromazine-morphine-pentobarbital showed ACTH-releasing activity comparable to the ACTH-releasing ability of 20 to 40 mU pressor activity of standard lysine vasopressin but no antidiuretice activity. Amino acid content indicates that these products are peptide in nature and different in composition from ACTH.