Endocrine-related biochemistry in the spectrum of human lung carcinoma

The association of hormonal syndrome and APUD (amine precursor uptake, decarboxylase) features with small cell carcinoma of the lung (SCC) has suggested that SCC has a separate cell origin from other major forms of lung cancer. Recently, however, both SCC and non-SCC lung cancers have been found to contain small polypeptide hormones and APUD enzymes. The present study quantitates, in 50 samples of human lung cancer tissue, relationships among the 4 major types of lung cancer and endocrine-related properties. Among 4 parameters measured (dopa decarboxylase, histaminase, beta-endorphin, and calcitonin), no single marker clearly separated SCC from non-SCC lung cancer. The high activity of dopa decarboxylase (the "D" in "APUD") best separated SCC from non-SCC, but significant overlap existed even for this critical APUD property. In fact, 2 adenocarcinomas had among the highest concentrations of dopa decarboxylase, histaminase, and calcitonin of any tumor tissue studied. The simultaneous appearance of high levels of 2 or more markers favored SCC. This was quantitated by deriving an index unit based upon the product of the values for the 4 markers in each lesion. This index separated all SCC from all non-SCC lung carcinomas, with the exception of the above 2 adenocarcinomas. Endocrine-related properties thus occur throughout the spectrum of human lung cancer. Biochemical differences between the major histopathological types are quantitative rather than qualitative and probably reflect the fact that the major forms of lung cancer represent a continuum of differentiation within a common cell lineage which includes both SCC and non-SCC lung tumors.