Increased plasma and tumor somatostatin-like immunoreactivity in medullary thyroid carcinoma and small cell lung cancer.

Abstract

To investigate the possible elaboration of soma-tostatin-like immunoreactivity (SLI) by medullary thyroid carcinoma (MTC) and/or by small cell lung cancer, we have ra-dioimmunoassayed extracts of plasma and tumor tissue from persons with these forms of cancer. These results have been compared with blood and tissue SLI measurements in patients with epidermoid lung cancer and people without detectable neoplastic disease. The upper limit of plasma SLI in 15 control subjects was 37 pg/ml. None of the 19 patients with epidermoid lung cancer had significantly elevated plasma SLI. By contrast, significantly elevated (136–6150 pg/ml) plasma SLI was noted in 3 of 7 cases of MTC and in 4 of 26 cases of small cell lung cancer. When SLI concentrations determined by direct RIA of plasma extracts were compared to SLI values determined by RIA of SLI isolated by immunoadsorbent chromatography, a highly significant direct correlation was noted. At least three SLI species (13,000, 4,000, and 1,600 daltons) were resolved by...