Differential production of interleukin-6 and its close relation to liver metastasis in clones from murine P815 mastocytoma

Interleukin-6 (IL-6)-producing abilities of plastic-adherent and plastic-non-adherent P815 clones were investigated in connection with the liver metastasis. Most adherent clones produced IL-6 at high level (over 10 ng/105 cells per 48 h), and they coincided with highly liver-metastatic clones. The remaining adherent and all the non-adherent clones tested produced IL-6 at low level (under 1.5 ng/105 cells), and they coincided with the low or non-liver-metastatic clones. The IL-6 production was greatly enhanced by IL-1α, but not by IL-6, tumor necrosis factor-α or interferon-γ.