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Animal experiments remain essential to understand the fundamental mechanisms underpinning malignancy and to discover improved methods to prevent, diagnose and treat cancer. Excellent standards of animal care are fully consistent with the conduct of high quality cancer research. Here we provide updated guidelines on the welfare and use of animals in cancer research. All experiments should incorporate the 3Rs: replacement, reduction and refinement. Focusing on animal welfare, we present recommendations on all aspects of cancer research, including: study design, statistics and pilot studies; choice of tumour models (e.g., genetically engineered, orthotopic and metastatic); therapy (including drugs and radiation); imaging (covering techniques, anaesthesia and restraint); humane endpoints (including tumour burden and site); and publication of best practice.

Key Points Chemokines are a subset of cytokines that cause the directed migration of leukocytes along a chemical gradient of ligand, known as the chemokine gradient. More than 50 human chemokines and 18 chemokine receptors have been discovered so far. Many cancers have a complex chemokine network that influences the immune-cell infiltration of a tumour, as well as tumour cell growth, survival and migration, and angiogenesis. Immune cells, endothelial cells and tumour cells themselves express chemokine receptors and can respond to chemokine gradients. Chemokines are a key determinant of the macrophage and lymphocyte infiltrate of human cancers and might contribute to T-helper 2 cell polarization. Malignant cells from different cancer types have different profiles of chemokine-receptor expression, but CXCR4 is most commonly found; at the last count, cells from 23 different cancer types expressed this receptor. Mutations in genes that alter levels of hypoxia-inducible factor, or gene-fusion events, can induce CXCR4 in cells that do not normally express this receptor. CXCR4 is also transiently increased by factors such as hypoxia, vascular endothelial growth factor and oestrogen in the tumour microenvironment. Studies of human cancer biopsy sampler and mouse cancer models show that cancer cell chemokine-receptor expression is associated with increased metastatic capacity. Preliminary laboratory data show that chemokine-receptor antagonists inhibit macrophage infiltrates, can induce tumour growth arrest or apoptosis, and prevent metastatic spread. Research into the cancer chemokine network is revealing parallels between the pathology of inflammation and malignancy, parallels that enhance our understanding of both types of disease and indicate new approaches for treatment. A complex network of chemokines and their receptors influences the development of primary tumours and metastases. New information about the biological role of chemokines in these processes is providing insights into host–tumour interactions, such as the role of the leukocyte infiltrate, and into the mechanisms that determine the metastatic potential and site-specific spread of cancer cells. Chemokine-receptor antagonists are showing promise in animal models of inflammation and autoimmune disease. Could manipulating the local chemokine network have therapeutic benefits in malignant disease?

We have defined the host leukocyte infiltrate in epithelial ovarian tumors and related this to the expression of C-C chemokines. Immunohistochemical analysis of 20 paraffin-embedded biopsies showed that the infiltrate was primarily composed of CD68+ macrophages and CD8+/CD45RO+ T cells (median values, 3700 cells/mm3 and 2200 cells/mm3, respectively). Natural killer cells, B cells, and mast cells occurred in lower numbers (median values, 0 to 200 cells/mm3). Eosinophils were rarely seen and neutrophils were mainly confined to blood vessels. More infiltrating cells were found in stromal than in tumor areas. Only macrophages occurred in significant numbers in areas of necrosis (P < 0.0005). Using in situ hybridization to mRNA, we examined expression of the chemokines MCP-1, MIP-1 alpha, MIP-1 beta, and RANTES. MCP-1 and MIP-1 alpha were expressed by significantly more cells than MIP-1 beta and RANTES (P < 0.005). In tumor epithelial areas, the predominant chemokine was MCP-1. MCP-1 and MIP-1 alpha were the predominant stromal chemokines. A significant correlation was found between the total number of CD8+ T cells and the number of cells expressing MCP-1 (rs = 0.63 and P < 0.003, respectively) and between the CD8+ population and RANTES-expressing cells (rs = 0.6 and P < 0.003). A correlation was also found between CD68+ macrophages and the number of cells expressing MCP-1 (rs = 0.50 and P = 0.026). We suggest that MCP-1 may be responsible for the leukocyte infiltrate in ovarian carcinomas, but the expression of other chemokines may determine its exact nature.

Tumour necrosis factor alpha (TNFalpha), named for its antitumour properties, was isolated almost 30 years ago. It is a vital member of the multifunctional TNF superfamily and has important roles in immunity and cellular remodelling as well as influencing apoptosis and cell survival. Its central role in inflammation has led to the development of TNFalpha antagonists as effective therapies for rheumatoid arthritis and inflammatory bowel disease. In this review, we discuss the evidence which has accumulated during the past decade that implicates TNFalpha in inflammatory pathways that increase tumorigenesis. There is convincing evidence that under specific conditions TNFalpha is a tumour promoter and helps to produce the toxic effects associated with conventional cancer therapy, such as the cytokine release syndrome and cisplatin-induced nephrotoxicity. Several trials have been set up to investigate the role of TNFalpha antagonists in cancer. It is hoped that these agents inhibit the neoplastic process either alone or in combination with other agents, and ameliorate the side effects of cancer therapy.

Early genetic events in the development of high-grade serous ovarian cancer (HGSOC) may define the molecular basis of the profound structural and numerical instability of chromosomes in this disease. To discover candidate genetic changes we sequentially passaged cells from a karyotypically normal hTERT immortalised human ovarian surface epithelial line (IOSE25) resulting in the spontaneous formation of colonies in soft agar. Cell lines transformed ovarian surface epithelium 1 and 4 (TOSE 1 and 4) established from these colonies had an abnormal karyotype and altered morphology, but were not tumourigenic in immunodeficient mice. TOSE cells showed loss of heterozygosity (LOH) at TP53 , increased nuclear p53 immunoreactivity and altered expression profile of p53 target genes. The parental IOSE25 cells contained a missense, heterozygous R175H mutation in TP53 , whereas TOSE cells had LOH at the TP53 locus with a new R273H mutation at the previous wild-type TP53 allele. Cytogenetic and array CGH analysis of TOSE cells also revealed a focal genomic amplification of CXCR4, a chemokine receptor commonly expressed by HGSOC cells. TOSE cells had increased functional CXCR4 protein and its abrogation reduced epidermal growth factor receptor (EGFR) expression, as well as colony size and number. The CXCR4 ligand, CXCL12, was epigenetically silenced in TOSE cells and its forced expression increased TOSE colony size. TOSE cells had other cytogenetic changes typical of those seen in HGSOC ovarian cancer cell lines and biopsies. In addition, enrichment of CXCR4 pathway in expression profiles from HGSOC correlated with enrichment of a mutated TP53 gene expression signature and of EGFR pathway genes. Our data suggest that mutations in TP53 and amplification of the CXCR4 gene locus may be early events in the development of HGSOC, and associated with chromosomal instability.

The response of the body to a cancer is not a unique mechanism but has many parallels with inflammation and wound healing. This article reviews the links between cancer and inflammation and discusses the implications of these links for cancer prevention and treatment. We suggest that the inflammatory cells and cytokines found in tumours are more likely to contribute to tumour growth, progression, and immunosuppression than they are to mount an effective host antitumour response. Moreover cancer susceptibility and severity may be associated with functional polymorphisms of inflammatory cytokine genes, and deletion or inhibition of inflammatory cytokines inhibits development of experimental cancer. If genetic damage is the “match that lights the fire” of cancer, some types of inflammation may provide the “fuel that feeds the flames”. Over the past ten years information about the cytokine and chemokine network has led to development of a range of cytokine/chemokine antagonists targeted at inflammatory and allergic diseases. The first of these to enter the clinic, tumour necrosis factor antagonists, have shown encouraging efficacy. In this article we have provided a rationale for the use of cytokine and chemokine blockade, and further investigation of non-steroidal anti-inflammatory drugs, in the chemoprevention and treatment of malignant diseases.

The matrix metalloprotease MMP-9 localizes to tumour-associated macrophages in human ovarian cancer but little is known of its regulation. Co-culture of human ovarian cancer cells (PEO-1) and a monocytic cell line (THP-1) led to production of 92-kDa proMMP-9. PEO-1-conditioned medium (CM) also stimulated THP-1 cells or isolated peripheral blood monocytes to produce proMMP-9. Expression of TIMP-1, however, remained unaffected. There was evidence that tumour necrosis factor alpha (TNF-alpha) was involved in tumour-stimulated monocytic proMMP-9 production. Antibody to TNF-alpha inhibited proMMP-9 production, and synthesis of TNF-alpha mRNA and protein preceded proMMP-9 release. In addition, the synthetic matrix metalloprotease inhibitor (MMPI) BB-2116, which blocks TNF-alpha shedding, inhibited proMMP-9 release in the co-cultures and from CM-stimulated monocytic cells. Further experiments suggested that the stimulating factor present in CM was not TNF-alpha, but acted synergistically with autocrine monocyte-derived TNF-alpha to release monocytic proMMP-9. Thus, ovarian cancer cells can stimulate monocytic cells in vitro to make proMMP-9 without affecting the expression of its inhibitor TIMP-1. This induction is mediated via a soluble factor (provisionally named MMPSF) that requires synergistic action of autocrine or paracrine TNF-alpha.

The receptor for macrophage colony-stimulating factor 1 receptor (CSF1R) is a product of the proto-oncogene c-fms and a member of the class III transmembrane tyrosine kinase receptor family. Earlier, we described increased mRNA expression of CSF1R in human telomerase reverse transcriptase (hTERT) immortalized human ovarian surface epithelial (IOSE) cell lines derived from a single donor. Here, we further describe that CSF1R is upregulated at both the mRNA and protein level in hTERT immortalized human normal OSE cells from two different donors and in hTERT immortalized human pancreatic ductal epithelial cells. CSF1R was not upregulated in hTERT immortalized epithelial clones that subsequently underwent senescence or in immortalized fibroblasts. Upon stimulation by the CSF1R ligand CSF1, the immortalized epithelial cell lines showed rapid internalization of CSF1R with concomitant down-modulation and colocalization of phosphorylated NFκBp65 with hTERT protein, hTERT translocation into the nucleus and the binding of c-Myc to the hTERT promoter region. Reducing the expression of CSF1R using short hairpin interfering RNA abolished these effects and also decreased cell survival and the number of population doublings under suboptimal culture conditions. The telomerase inhibitor GRN163L confirmed a role for telomerase in the cleavage of the intracellular domain of CSF1R. On the basis of these findings, we suggest that CSF1R may be a critical factor facilitating hTERT immortalization of epithelial cells.