Establishment and Characterization of a New Lung Cancer Cell Line (MI‐4) Producing High Levels of Granulocyte Colony Stimulating Factor

We established a human lung cancer cell line, MI‐4 from the pleural effusion of a 69‐year‐old male with advanced large cell undifferentiated carcinoma of the lung complicated by leukocytosis. The culture supernatant of MI‐4 contained high levels of granulocyte colony stimulating factor (G‐CSF). The intracellular localization of the G‐CSF was identified by immunocytochemistry. Reverse transcription‐polymerase chain reaction (RT‐PCR) revealed G‐CSF mRNA expression in this cell line. The cell line was successfully transplanted into nude mice. The transplanted nude mice also showed leukocytosis with a high serum G‐CSF level. Southern blot analysis did not show amplification or rearrangement of the G‐CSF gene in MI‐4 cells. Spectral karyotyping (SKY) and fluorescence in situ hybridization (FISH) analyses revealed that this cell line has an additional chromosome 17 attached to a segment of chromosome 10 besides two intact chromosomes 17, and that each of these three chromosomes 17 has a G‐CSF gene on chromosome 17q. Inflammatory cytokines, tumor necrosis factor (TNF)‐α and interleukin (IL)‐1β, significantly enhanced G‐CSF expression at both the protein and mRNA levels in MI‐4. However, these cytokines did not stimulate the growth of MI‐4 cells, regardless of abundant G‐CSF production. TNF‐α rather suppressed it, in a dose‐dependent manner. Exogenous recombinant human G‐CSF and anti‐G‐CSF antibody did not promote or inhibit the growth of MI‐4 cells at any concentration examined. In addition, RT‐PCR analysis did not show G‐CSF receptor mRNA expression. These results suggest that this cell line does not have an autocrine growth loop for G‐CSF. This cell line should be very useful for understanding the biological activity of G‐CSF in G‐CSF‐overproducing lung cancer.