PKA-dependent growth stimulation of cells derived from human pulmonary adenocarcinoma and small airway epithelium by dexamethasone

Smoking is a risk factor for lung cancer, chronic obstructive pulmonary disease, chronic bronchitis and asthma. The chronic lung diseases are also a predisposing factor for the development of lung cancer. Glucocorticoids are used for the management of chronic lung diseases because of their anti-inflammatory activity. These drugs also have anti-tumourigenic effects in mouse models of lung cancer. Glucocorticoids are frequently used as co-treatment with cancer therapy. Using the human pulmonary adenocarcinoma (PAC) cell line NCI-H322 with features of bronchiolar Clara cells, and immortalised human small airway epithelial cells, our data show that the glucocorticoid dexamethasone increased cell proliferation in MTT assays in a PKA-dependent manner. Dexamethasone significantly increased intracellular cAMP in direct immunoassays. Immunoblot analysis revealed increased phosphorylation of ERK1/2 and of the transcription factor CREB in response to dexamethasone. These data suggest that glucocorticoids could have tumour promoting activity on a sub-set of human PAC.