Paraneoplastic leukemoid reaction and rapid progression in a patient with malignant melanoma: establishment of KT293, a novel G-CSF-secreting melanoma cell line.

Paraneoplastic leukemoid reaction (PLR) is a rare condition of leucocytosis in cancer patients. Here we report the rapid progression of a patient suffering from a metastasized malignant melanoma and PLR. The patient's white blood cell count exceeded 200,000 cells per mul and the serum level of Granulocyte Colony-Stimulating Factor (G-CSF) was elevated up to 780 pg/mul. A Tc-m99-labeled anti-NCA90/95 based granulocyte scan demonstrated reactive bone marrow expansion, splenomegaly and granulocyte infiltration into the tumor. KT293, a S100, gp100 and CD68 positive melanoma cell line derived from an axillary metastasis, produced large amounts of G-CSF in vitro and induced rapidly growing tumors and PLR after subcutaneous inoculation in SCID mice. In contrast to G-CSF-secreting cancer cells of other tissue origin, G-CSF-neutralizing antibodies failed to inhibit the growth of KT293 cells. In addition, KT293 cells did not express G-CSF-receptor. These observations suggest that paracrine effects of G-CSF-secretion and PLR might promote an aggressive melanoma phenotype, as seen in this patient.