Establishment of Continuous, Clonable Cultures of Small-Cell Carcinoma of the Lung Which Have Amine Precursor Uptake and Decarboxylation Cell Properties

Small-cell carcinoma of the lung (SCCL) grows rapidly in patients and can be maintained in culture for months but is difficult to establish in continuously replicating, clonable cell lines. We have established 15 SCCL cell lines from 11 patients. The SCCL lines grew as floating-cell aggregates with relatively long doubling times and formed tumors having typical SCCL histology in athymic nude mice. They had human enzyme markers, were aneuploid, and cloned in soft agarose at low efficiencies. These lines and their clonal derivatives expressed features of amine precursor uptake and decarboxylation (APUD) cells, including high dopa decarboxylase activity (EC 4.1.1.28), formaldehyde-induced fluorescence, and neurosecretory granules. While only two of 21 tumor specimens plated in fetal bovine serum-supplemented medium (growth medium) developed into continuous lines, 6 of 11 tumor specimens plated into growth medium conditioned by other SCCL cultures developed into lines. Conditioned medium also increased the colony-forming efficiency and colony size of some primary tumor specimens and early unestablished cultures, including one of the two specimens not absolutely requiring conditioned medium for initial growth. Continuous cell lines were eventually established from all eight SCCL tumors heterotransplanted in athymic nude mice; however, their replication was initially dependent on the presence of mouse stromal cell for periods of 3 to 24 months. Growth factor requirements of lung tumors of other histologies appeared less stringent; three of five non-SCCL lung tumors were readily established as continuous cell lines in growth medium. These cell lines from non-SCCL lung cancers lacked the APUD properties and neurosecretory granules characteristic of SCCL. We conclude that (a) human small-cell lung cancer lines and their clonal derivatives grown in vitro for long periods of time continue to express a program for APUD cell properties; (b) the establishment of such lines in some cases stringently requires, and in other cases is greatly facilitated by, conditioned medium containing as yet unknown growth factors; (c) these factors can come from either other cell cultures or nude mouse tumor stromal cells; and (d) that at least some non-small-cell lung cancers have a much less stringent growth factor requirement for establishment, have higher cloning efficiencies, and lack APUD cell properties.