MicroRNAs (miRNAs) — an abundant class of small non–protein–coding regulators of gene expression — play an important role in tumorigenesis and, depending on their targets, can function as tumour suppressors or oncogenes. Crucially, miRNA–expression profiling of human tumours has identified signatures associated with diagnosis, staging, progression, prognosis and response to treatment.

Here we present a series of specially commissioned articles that discuss the key issues and our current knowledge of MYC and cancer. Since the isolation of the MYC oncogene in the early 1980's, the concepts that try to explain how this transcription factor contributes to tumorigenesis are numerous and encompass many fields. And yet, new ideas about MYC–dependent responses and how these might be involved in tumorigenesis are still emerging as the repertoire of signalling pathways that are induced downstream of MYC activation expand. In addition, key concepts implicit in the consideration of how MYC might function as an oncogene are also likely to be relevant to other oncogenes and transcription factors, and may have therapeutic relevance.

Throughout 2008, a series of specially commissioned articles that examine hypoxia and metabolism in tumour biology will be published in Nature Reviews Cancer. Although hypoxia is not a new phenomenon, we now have a much greater understanding of the molecular links between hypoxic conditions and tumour development. Apart from driving angiogenesis, hypoxia is also linked with changes in cellular metabolism, an area that has become a hot topic in cancer research. A greater understanding of these closely related tumorigenic changes should prove fruitful in the pursuit of more effective cancer drugs.

Nature Reviews presents a Collection on microRNAs, which includes Reviews from Nature Reviews Genetics,Nature Reviews CancerandNature Reviews Molecular Cell Biology. The articles have been specially selected to provide an introduction to diverse aspects of microRNA biology, including their biogenesis, function in normal development and cancer, and evolutionary implications of their impact on gene regulation.

Biomarkers can help assess and treat patients with cancer. They can be used not only to diagnose cancer, but also to determine the stage and subtype of a tumour to assess patient prognosis and the ability of a tumour to respond to a particular therapy. This Nature Reviews Cancercollection includes a selection of recent Reviews, Perspectives and Research Highlights that provide an up-to-date insight into the development and ultimate clinical use of cancer biomarkers.

Milestones in Cancer is a collaborative project involving three journals - Nature,Nature MedicineandNature Reviews Cancer- and celebrates more than 100 years of discoveries in the field of cancer.

Throughout 2006 and 2007, a series of articles on the Tumour Microenvironment was published in Nature Reviews Cancer. The study of the tumour microenvironment involves a multidisciplinary approach, with in vitro and in vivo models of tumour growth, invasion, extracellular matrix remodelling, angiogenesis and inflammation, as well as preclinical trials, all contributing to the rapid progress that is being made in this area. We hope that this series of articles gave you a taste of the diversity of topics that form part of this rapidly moving field.

Biomarkers are invaluable tools for cancer detection, diagnosis, patient prognosis and treatment selection. This focus discusses issues surrounding important genetic, epigenetic and protein biomarkers of cancer, including how these can be used to better understand tumour formation and to develop new therapeutic approaches.

Epigenetics — the study of heritable changes in gene expression or function that occur without a change in the DNA sequence itself — is proving to have an increasingly important role in both human development and disease, particularly cancer.

The development of cancer vaccines is not a new idea. In the late nineteenth century William Coley and colleagues observed that spontaneous tumour regression, although rare, often occurred after patients had mounted an immune response to an opportunistic infection. These ideas spawned many years of research into cancer vaccines, which, although successful in the laboratory, proved highly disappointing in the clinic.

We examine the role of kinase signalling in cancer and the potential for developing effective therapies that can modulate various kinase pathways. Following the success of targeted kinase inhibitor therapies such as imatinib and gefitinib this continues to be a fast moving area of research.

Since the early studies of the 17th century, microscopy has played a vital role in biological discovery − it enabled Robert Hooke to describe cells and Antonie van Leeuwenhoek to discover bacteria. Four centuries later, microscopy techniques remain at the centre of cell-biological research.