The eponymous and tragic hero in Oscar Wilde's The Picture of Dorian Gray keeps his youthful good looks despite a life of corruption, debauchery and murder -- his sins are visited instead on a ghastly portrait. Dorian Gray escaped what Wilde thought was the fate of all men -- that the scars of their lives would be worn on their faces.

What can we tell of something from its outside? Researchers in America now report how varied forms and behaviour of human breast tumours can be related to (similarly diverse) genes expressed within them. This approach should open the way to marked improvements in our understanding of the genetic aspects of tumour formation.

It should also lead to improvements in therapy. Detailed genetic portraits of tumours -- and some understanding of the behaviour of the genes involved -- will make it easier to design simpler and more effective therapeutic régimes. Such therapies would have a better chance of success than current approaches -- and potentially fewer side effects.

David Botstein of Stanford University School of Medicine, Stanford, California, and colleagues have drawn up such molecular portraits of tumours. They report their results in Nature1.

Botstein's team analysed breast tumour genetics using new 'biochip' technology that samples the simultaneous activities of thousands of genes. In fact the researchers studied some 8,102 genes of 65 breast tumour specimens from 42 different patients. The data were then grouped to relate gene activity and particular clinical phenomena, including reactions to chemotherapy.

As the new 'genomics' world is showing, many states of health and disease depend on how hundreds or thousands of genes interact with one another and the environment.

Researchers have long understood this, but previous technology has limited them to laborious one-gene-at-a-time approaches. Biochips -- in which genes are represented on a glass slide, and mapped -- make possible the simultaneous scanning of huge batteries of genes. This brings a holistic (rather than piecemeal) view of what is really happening.

So what is the relationship between the inner gene profile and the public face of the tumour? Do the 'molecular portraits' of the tumours, painted by the researchers, relate the tumour appearance to the genetic activity within? The answer is a resounding yes.

"[The genetic activity profiles] in two tumour samples from the same individual were almost always more similar to each other than either was to any other sample," the researchers say. This similarity was obvious even in one sample taken after chemotherapy.

The results confirm that genetic activity as a whole has a direct relationship with the external appearance of a tumour. So monitoring genetic activity should successfully guide understanding and therapy.

The epigrammatic Wilde also said that a man's face is his autobiography. This latest research may teach us to ignore his additional contention -- that a woman's face is her work of fiction. What is on the outside, in other words, reflects the inside.