Constitutive expression of interleukin-8 by Mutatect cells markedly affects their tumor biology

Polymorphonuclear neutrophils and cancer: intense and sustained neutrophilia as a treatment against solid tumors

Polymorphonuclear neutrophils (PMN) are the most abundant circulating immune cells and represent the first line of immune defense against infection. This review of the biomedical literature of the last 40 years shows that they also have a powerful antitumoral effect under certain circumstances. Typically, the microenvironment surrounding a solid tumor possesses many of the characteristics of chronic inflammation, a condition considered very favorable for tumor growth and spread. However, there are many circumstances that shift the chronic inflammatory state toward an acute inflammatory response around a tumor. This shift seems to convert PMN into very efficient anticancer effector cells. Clinical reports of unexpected antitumoral effects linked to the prolonged use of granulocyte colony-stimulating factor, which stimulates an intense and sustained neutrophilia, suggest that an easy way to fight solid tumors would be to encourage the development of intense peritumoral PMN infiltrates. Specifically designed clinical trials are urgently needed to evaluate the safety and efficacy of such drug-induced neutrophilia in patients with solid tumors. This antitumoral role of neutrophils may provide new avenues for the clinical treatment of cancer.

IL-1 alpha, innate immunity, and skin carcinogenesis: the effect of constitutive expression of IL-1 alpha in epidermis on chemical carcinogenesis

Tumor promoters such as the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) are proinflammatory agents, and their mechanism of action in epithelial carcinogenesis has been linked to the release of IL-1 alpha and the induction of chronic inflammation in skin. To test the role of IL-1 alpha and inflammation in models of cutaneous carcinogenesis, we used our previously described FVB/N transgenic mice overexpressing 17-kDa IL-1 alpha in the epidermis under the keratin 14 (K14) promoter. Strikingly, the K14/IL-1 alpha mice were completely resistant to papilloma and carcinoma formation induced by a two-stage DMBA/TPA protocol, while littermate controls developed both tumor types. K14/IL-1 alpha mice crossed with the highly sensitive TG.AC mice, constitutively expressing mutant Ha-Ras, also failed to develop papillomas or carcinomas. When the K14/IL-1 alpha transgene was bred onto a recombinase-activating gene-2-deficient background, the resistance persisted, indicating that innate, but not acquired, mechanisms may be involved in the resistance to the initiation/promotion model. As an alternative approach, a complete carcinogenesis protocol using repetitive application of DMBA alone was applied. Surprisingly, although the IL-1 alpha mice still did not develop papillomas, they did develop carcinomas de novo at an accelerated rate compared with controls. We conclude that constitutive IL-1 alpha expression rendered FVB mice completely resistant to carcinomas that required evolution from prior papillomas, but facilitated carcinomas that did not evolve from papillomas, as in the complete carcinogenesis protocol. Thus, the role of IL-1 alpha and, by extension that of other proinflammatory factors, in epithelial carcinogenesis are more complex than previously appreciated. These mice may provide a mechanism to investigate the validity of these models of human skin tumorigenesis.

Dietary vitamin E affects neutrophil distribution and genetic instability in murine Mutatect tumors

Vitamin E is best known for its ability to scavenge reactive oxygen and nitrogen species. Solid tumors are frequently infiltrated with leukocytes, a potential source of these reactive species. The Mutatect tumor model is a fibrosarcoma that can be grown subcutaneously in syngeneic C57BL/6 mice. We previously showed that these tumors are infiltrated with neutrophils and that the number of neutrophils correlates with the number of hypoxanthine phosphoribosyl transferase (hprt) mutations and loss of an interleukin-8 (IL-8) transgene. Neutrophils are a source of nitric oxide, and tumors contain nitrotyrosine, a marker of damage by nitric oxide-related species. We also showed previously that dietary vitamin E supplements markedly lower the frequency of hprt mutants and the level of myeloperoxidase (a neutrophil marker) in a tumor fraction containing "loosely bound" cells. In the present report, we examine the effect of dietary vitamin E in greater detail. No effect on inducible nitric oxide synthase expression or nitrotyrosine levels was observed. However, dietary vitamin E induced a major redistribution of neutrophils from the loosely bound cellular fraction to the "stromal" fraction, while the total number of neutrophils in tumors was essentially unchanged. The loss of the IL-8 transgene seen earlier in Mutatect tumors was largely prevented. Vitamin E also prevented the large increase in hprt mutants (in the cellular and stromal fractions). Thus vitamin E appears to be protective against genotoxicity by scavenging reactive species, but also its ability to affect the distribution of neutrophils within tumors may be important.

Induction of IL-8 and monoclyte chemoattractant protein-1 by doxorubicin in human small cell lung carcinoma cells

We previously demonstrated doxorubicin-induced urokinase expression in human H69 SCLC cells by the microarray technique using Human Cancer CHIP version 2 (Takara Shuzo, Kyoto, Japan), in which 425 human cancer-related genes were spotted on glass plates (Kiguchi et al., Int J Cancer 2001;93:792-7). Microarray analysis also revealed significant induction of IL-8, a member of the CXC chemokines. We have, therefore, extended the observation by testing the effects of doxorubicin on expression of the chemokine family and provide here definitive evidence that doxorubicin induces IL-8 and MCP-1, one of the CC chemokines, at least in 2 human SCLC cells, H69 and SBC-1. IL-8 antigen levels, measured by ELISA, were markedly increased in both H69 and SBC-1 conditioned media after doxorubicin treatment, in parallel with mRNA levels; and this was dependent on the dose of doxorubicin. The ribonuclease protection assay, using a multiprobe template set for human chemokines, revealed induction of not only IL-8 but also MCP-1 in doxorubicin-treated H69 cells. MCP-1 antigen levels increased approximately 100-fold in doxorubicin-treated H69 cells. RT-PCR using specific primers for MCP-1 suggested that doxorubicin also induced MCP-1 expression in SBC-1 and SBC-3 SCLC cells. Futhermore, CAT analysis using IL-8 promoter implicated the PEA3 transcriptional factor, whose binding site was located immediately upstream of the AP-1 and NF-kappaB binding sites. Thus, it is suggested that doxorubicin induces IL-8 and MCP-1 chemokines in human SCLC cells by activating gene expression, in which at least PEA3 is involved. IL-8 and MCP-1 are major chemoattractants for neutrophils and monocytes/macrophages, respectively; therefore, extensive induction of IL-8 and MCP-1 may provoke the interaction between inflammatory/immune cells and tumor cells under doxorubicin stimulation and influence many aspects of tumor cell biology.

Differential response of primary and metastatic melanomas to neutrophils attracted by IL-8

IL-8 is a strong chemoattractant for neutrophils, and it is constitutively produced by many tumors, including human melanomas. To determine the biologic importance of IL-8 for melanoma cells from primary and metastatic lesions, we transduced selected cell lines constitutively producing low levels of IL-8 with IL-8 cDNA using a replication-deficient adenoviral vector. Nontumorigenic SBcl2 primary melanoma cells formed tumors when transduced with increasing plaque-forming units of IL-8 per cell. However, at high IL-8 transduction levels (100 ng/ml/10(5) cells in 48 hr), tumor growth was impaired due to massive neutrophil infiltration. A similar biphasic response was observed in WM115 primary melanomas, which are tumorigenic but not metastatic. Depletion of neutrophils with an antibody that blocks the accumulation of granulocytes at the site of inflammation enabled transduced primary melanomas secreting high levels of IL-8 to survive and grow. In contrast, highly tumorigenic and metastatic 451Lu cells showed marked increases in tumor growth and number of metastatic foci in the lungs depending on the expression levels of IL-8. Cytotoxicity assays with isolated neutrophils confirmed the preferential killing of primary over metastatic melanoma cells. SBcl2 cells stimulated by IL-8 to form tumors in immunodeficient mice were induced to produce VEGF, suggesting that the angiogenic response is enhanced due to increased growth factor production. Our results demonstrate that nontumorigenic primary melanomas depend on IL-8 stimulation in vivo for growth and that tumor growth depends on the level of neutrophil infiltration. Metastatic melanomas proliferate in vivo independently of infiltrating neutrophils.

Neutrophils in anti-cancer immunological strategies: old players in new games

This review highlights the new "immunological identity" of neutrophils within the cytokine network and their role in biology of diseases, particularly in tumor biology. The latest preclinical evidence of their involvement in anti-cancer immunotherapeutic and prophylactic strategies will be discussed with particular reference to the real possibilities of transferring experimental results to a clinical setting.