The growth of cancer cells in inflammatory tissue is often observed. This can be the result of favorable conditions for endothelial cell adherence and/or increased production of local growth factors.
The role of the proinflammatory cytokine interleukin 1 (IL-1) in the prometastatic and growth-promoting environment of inflammation was studied in vivo, and the mechanism of cytokine action was studied in vitro as well.
Systemic inflammation was induced by the intravenous injection of IL-1β or lipopolysaccharide (LPS), and the hepatic metastasizing ability of B16 melanoma (B16) cells following intrasplenic injection was studied. IL-1 receptor blockade was accomplished with the use of the IL-1 receptor antagonist (IL-1Ra). In vitro, IL-1Ra was used to assess the mechanism for prometastasis and growth promotion of cultured hepatic sinusoidal endothelium stimulated with LPS.
There was a statistically significant ( P <.01) enhancement in the parameters of hepatic metastasis when B16 cells were injected intrasplenically either 4 hours after IL-1 injection or 6 or 12 hours after LPS injection. IL-IRa pretreatment reduced IL-1-induced enhancement of metastasis by 73%-87% and completely inhibited the augmentation of metastasis following LPS injection. In vitro, the adherence of melanoma cells to LPS-treated endothelium increased nearly twofold but was completely abrogated when IL-1Ra was added before LPS. Similar to melanoma adherence, a 2.5-fold increase ( P <.05) in functional mannose receptors was observed with LPS treatment but was prevented by the addition of IL-1Ra. IL-1Ra did not affect basal mannose-receptor activity in unstimulated epithelium. Mannose-receptor activity and B16 cell adherence significantly correlated ( r = .9) with LPS treatment. Conditioned medium from LPS-stimulated epithelium augmented B16 cell proliferation compared with control conditioned medium ( P <.01). Production of B16 cell growth factor(s) was markedly reduced ( P <.01) when IL-1Ra was added.
These results demonstrate that systemic inflammation induces an enhancement of melanoma cell metastasis and growth by IL-1-dependent mechanisms in vivo. In vitro, the mechanism(s) is consistent with IL-1-mediated increase in expression of mannose receptors and production of tumor cell growth factor(s) from the endothelium.
Given the multiple and complex cytokine cascade induced in vivo and in vitro during LPS-induced systemic inflammation, IL-1 plays a strategic role. Since IL-1Ra is without side effects in humans, studies on intraoperative infusion of IL-1Ra during tumor resection may be indicated. [J Natl Cancer Inst 1996;88:198–205]