Tumor necrosis factor induces neuroendocrine differentiation in small cell lung cancer cell lines
We studied tumor necrosis factor (TNF)-α as a candidate cytokine to promote neuroendocrine cell differentiation in a nitrosamine-hyperoxia hamster lung injury model. Differential screening identified expression of the genes modulated by TNF-α preceding neuroendocrine cell differentiation. Undifferentiated small cell lung carcinoma (SCLC) cell lines NCI-H82 and NCI- H526 were treated with TNF-α for up to 2 wk. Both cell lines demonstrated rapid induction of gastrin-releasing peptide (GRP) mRNA; H82 cells also expressed aromatic-L-amino acid decarboxylase mRNA within 5 min after TNF-α was added. Nuclear translocation of nuclear factor-κB immunostaining occurred with TNF-α treatment, suggesting nuclear factor-κB involvement in the induction of GRP and/or aromatic-L-amino acid decarboxylase gene expression. We also demonstrated dense core neurosecretory granules and immunostaining for proGRP and neural cell adhesion molecule in H82 cells after 7-14 days of TNF-α treatment. We conclude that TNF-α can induce phenotypic features of neuroendocrine cell differentiation in SCLC cell lines. Similar effects of TNF-α in vivo may contribute to the neuroendocrine cell differentiation/hyperplasia associated with many chronic inflammatory pulmonary diseases.