Human bladder carcinoma cell line HTB9, which secretes a factor to stimulate clonogenic leukemic blast growth, expresses the granulocyte-macrophage colony-stimulating factor gene.

Media conditioned by the human bladder carcinoma cell line HTB9 contained high leukemic blast growth factor activity and also showed granulocyte-macrophage colony-stimulating factor (GM-CSF) activity. Northern blotting analysis of total RNA from HTB9 cells using GM-CSF cDNA as a probe demonstrated abundant expression of the GM-CSF gene. Thus, this cell line secretes GM-CSF, and this factor contributes to the proliferation of clonogenic leukemic blast cells.