Purpose: We have previously demonstrated doxorubicin-induced urokinase (uPA) and interleukin-8 (IL-8) expression in human H69 small-cell lung carcinoma (SCLC) cells by a microarray technique using Human Cancer Chip version 2, in which 425 human "cancer-related" genes are spotted on the plates. The microarray analysis also revealed a significant induction of tumor necrosis factor-alpha (TNF-alpha), and doxorubicin-induced macrophage chemoattractant protein-1 (MCP-1) expression was demonstrated by an RNase protection assay. We extended the study by testing the effects of doxorubicin on the induction of TNF-alpha, uPA, IL-8 and MCP-1 in other types of lung carcinoma cells.
Methods: We investigated the effects of doxorubicin on the expression of TNF-alpha, uPA, IL-8 and MCP-1 in 12 human lung carcinoma cell lines, including five SCLC, three adenocarcinoma and four squamous cell carcinoma cells. The surface expression of their receptors was also investigated.
Results: TNF-alpha was significantly induced in three cell lines, H69, SBC-7 (SCLC) and PC-9 (adenocarcinoma), uPA in five cell lines, H69, SBC-7, EBC-1 (squamous cell), EBC-2 (squamous cell), and Sq-1 (squamous cell), IL-8 in three cell lines, H69, PC-9 and EBC-1, and MCP-1 in five cell lines, H69, SBC-3 (SCLC), SBC-7, PC-9 and Sq-1. In H69 cells, TNF-alpha antigen levels were increased approximately fivefold in the conditioned medium of doxorubicin-treated cells, in parallel with an increase in mRNA levels. As with uPA and IL-8, the maximum induction was observed at the "sublethal" concentrations of 2 and 4 microM at which cell growth was slightly inhibited 24 h after treatment. Furthermore, the cells did not express receptors including types I and II TNF-alpha receptors, uPA receptor (uPAR), C-x-C-chemokine receptor-1 (CXCR-1), or C-C-chemokine receptor-2, corresponding to TNF-alpha, uPA, IL-8 and MCP-1, respectively, that were induced by doxorubicin in the cells, although SBC-7 cells expressed uPAR, and EBC-1 cells expressed CXCR-1.
Conclusions: TNF-alpha, uPA, IL-8 and MCP-1 induced and secreted from tumor cells upon doxorubicin stimulation may activate surrounding cells expressing the receptors such as neutrophils and monocytes/macrophages in a paracrine fashion. TNF-alpha is a major proinflammatory cytokine, and IL-8 and MCP-1 are major chemoattractants for neutrophils and monocytes/macrophages, respectively. Furthermore, uPA activates matrix metalloproteinase 9 which can truncate and activate IL-8. Thus, the simultaneous induction of TNF-alpha, uPA, IL-8 and MCP-1 may enhance the interaction between tumor and inflammatory/immune cells, and augment cytotoxicity.