'Angiogenesis' has been a buzzword in cancer research for several years now. It means 'blood vessel formation' - a process that fascinates cancer specialists because a tumour that is efficiently fed with blood is a successful, growing tumour.

The latest development in the angiogenesis story is that the early stages of tumour formation could result from inflammation gone wrong. In a mouse model of skin cancer, at least, Lisa Coussens and colleagues of the University of California, San Francisco, California have found that some of the key players in inflammation appear to be involved in setting the stage for malignant blood-vessel growth.

As Coussen and her group explain in the June issue of Genes and Development, the main villains of the piece are so-called 'mast' cells. Mast cells are unevenly shaped cells with large nuclei that come from the same lineage as blood cells and are found in connective tissue and fatty regions. They are central to the kind of healthy, healing inflammation reaction that the mammalian body mounts to protect itself against infection, injury or tissue damage, but they are also thought to promote angiogenesis.

After studying the distribution of mast cells (and their products) in mice that had been genetically modified to grow human skin cancers, the researchers found that, during the early stages of cancer development, the body's natural anti-tumour inflammatory response and the mast cells involved therein are hijacked by tumour cells for their own ends. Apparently these mutated cells redirect the tissue-rebuilding abilities of mast cells and the inflammatory process as a whole into planting and anchoring the blood-vessel-rich bedrock of cancerous growth.

Thus firmly established, a tumour can then drive its own angiogenesis without recourse to mast cells - indicating that "a clear goal for the future," as Coussen's group concludes, "is to identify the signals that recruit the mast cell inflammation."

The evidence pointing to such a system has been growing for more than a hundred years. Mast cells, which are essentially absent from tumour interiors, were first found at the borders of tumours as far back as 1891. More recently, they have been shown to lurk on the fringes of three of the most aggressive human cancers - malignant melanoma, breast carcinoma and colorectal adenocarcinoma (cancer colon). Furthermore, studies of animals deficient in mast cells have revealed that they exhibit diminished angiogenesis and hence significantly less cancerous tissue.