LONDON The more scientists look, the more complex cancer seems to become.
British scientists said on Wednesday they had found a batch of new gene mutations linked to kidney cancer, suggesting even this apparently "straightforward" cancer type can be divided into subtypes requiring tailored treatment.
Clear cell renal cell carcinoma (ccRCC), the most common type of kidney cancer, stands out from other cancers because it is remarkably consistent and the majority of cases are known to be driven by mutations in a single gene, called VHL.
Yet when researchers conducted a large DNA sequencing study of more than 3,500 genes from around 100 tumor samples, they found evidence that additional mutations in other genes were also driving cells to become cancerous.
Three of the genes were involved in modifying proteins called histones, which help package DNA into chromosomes and are critical to the functioning of cells, they reported in the journal Nature.
"Even in this clearest of cases, we see evidence for substantial genetic heterogeneity," said Andy Futreal, co-leader of the Cancer Genome Project at the Wellcome Trust Sanger Institute in Cambridge.
While none of the new mutations accounted for more than 5 percent of cancer cases, the discovery should ultimately help in diagnosis and better selection of treatments for patients.
The latest findings underline the case for personalized medicine, or tailoring drugs to the genetic make-up of individual patients.
Scientists at the Sanger Institute last month also produced genetic "maps" identifying thousands of genetic mutations behind melanoma skin cancer and lung cancer.
Several personalized drugs are already used in cancer, including Roche's Herceptin for breast cancer and AstraZeneca's Iressa for lung cancer.
For drugmakers, tailored medicine is both an opportunity and a challenge as sub-dividing tumors by their molecular type shrinks the market for individual therapies.
Kidney cancer kills more than 100,000 people worldwide each year. Recent new drugs against the disease include Pfizer's Sutent and Bayer's Nexavar, which block cell proliferation and starve tumors of blood supply.
(Editing by Elizabeth Fullerton)