Development and elongation of neurite-like outgrowth on small cell lung cancer cell lines.

One (Lu-134A) of nine human small cell lung cancer cell lines which grow as floating cell aggregates changed its morphology dramatically when cells were cultured on a coverslip coated with polyethylenimine or extracellular matrix of human lung adenocarcinoma cell line PC-9 cells. The Lu-134A cells adhered to the substrate and developed elongated cytoplasmic processes which gradually grew into long neuronal-like processes. These processes developed to a length of more than 10 times the cell body length after 20 days of culture. Addition of dibutyryl cyclic adenosine 3', 5'-monophosphate to the cells on these substrates remarkably promoted the development and elongation of the processes, which grew into a netlike arrangement. The characteristics of these elongated neuronal-like processes were studied using immunocytochemical and electron microscopical methods. The processes reacted intensely with monoclonal antibodies against beta-tubulin and microtubule-associated protein-2. The swelling portions of the distal tips of these processes reacted strongly with polyclonal antibody against synaptophysin. Neurosecretory granules and bundles of microtubules were observed within processes. These findings suggested that this human small cell lung cancer cell line (Lu-134A) differentiated into neuronal cells, and indicated that attachment of cells to a substrate is the key to the development of long neurite-like outgrowths.