Establishment of a Clonal Cell Line Producing Granulocyte Colony‐Stimulating Factor and Parathyroid Hormone‐Related Protein from a Lung Cancer Patient with Leukocytosis and Hypercalcemia

Squamous cell lung carcinoma cells obtained from a patient who presented with leukocytosis and hypercalcemia were transplanted into nude mice anda serially transplantable cell line, OKa‐N‐1, was established. The nude mice transplanted with OKa‐N‐1 cells displayed leukocytosis and hypercalcemia. Serum levels of granulocyte colony‐stimulating factor (G‐CSF) and parathyroid hormone‐related protein (PTHrP) were both elevated in these mice. In vitro cultivation of this tumor cell line gave rise to a clonal cell line, OKa‐C‐1. Nude mice transplanted with the OKa‐C‐1 cell line also showed leukocytosis and hypercalcemia with high serum G‐CSF and PTHrP levels. The culture supernatant of OKa‐C‐1 contained high levels of G‐CSF and PTHrP. Immunohistochemical studies showed the expression of PTHrP in OKa‐C‐1 cells. Reverse transcription polymerase chain reaction revealed the presence of G‐CSF and PTHrP mRNA in this cell line. Dexamethasone treatment inhibited the transcription of G‐CSF and PTHrP genes. This new human squamous carcinoma cell line, OKa‐C‐1, would be useful for studying the mechanism of simultaneous production of G‐CSF and PTHrP and their control in cancer patients with leukocytosis and hypercalcemia.