Regulation of Granulocyte Colony‐stimulating Factor and Parathyroid Hormonerelated Protein Production in Lung Carcinoma Cell Line OKa‐C‐1

Previously we have established a clonal squamous cell carcinoma cell line OKa‐C‐1 derived from lung cancer of a patient with marked leukocytosis and hypercalcemia. OKa‐C‐1 cells simultaneously produce granulocyte colony‐stimulating factor (G‐CSF) and parathyroid hormone‐related protein (PTHrP) at the single cell level and cause paraneoplastic syndromes in nude mice bearing the tumor. It is known that the production of G‐CSF and PTHrP is individually regulated by inflammatory cytokines in various malignant cells. To investigate the common factors in the regulation of G‐CSF and PTHrP production in OKa‐C‐1 cells, we examined the effects of some inflammatory agents [lipopolysaccharide (LPS), phorbol‐12‐myristate‐13‐acetate (PMA), tumor necrosis factor‐α (TNF‐α), interleukin‐1 (IL‐1) β and IL‐6] on G‐CSF and PTHrP production, by means of enzyme‐linked immunosorbent assay (ELISA), immunoradiometric assay (IRMA) and quantitative reverse transcription‐polymerase chain reaction (RT‐PCR). TNF‐α or IL‐1β induced both G‐CSF and PTHrP production in the conditioned medium. TNF‐α synergized with IL‐1β to significantly increase G‐CSF production. In addition, TNF‐α and IL‐1β strongly induced G‐CSF mRNA with peaks at 2 and 6 h respectively. Although PTHrP production was also strongly induced by TNF‐α PTHrP mRNA expression was more strongly induced by PMA than by TNF‐α. Thus, TNF‐α and IL‐1β could be common factors that individually and synergistically regulate G‐CSF and PTHrP production in OKa‐C‐1 cells. Moreover, G‐CSF and PTHrP production could be not only transcriptionally, but also posttranscriptionally regulated by other factors.