Scientists decipher cancer genomes

Cambridge, England

- The first comprehensive analyses of cancer genomes are complete, according to new research published in the Dec. 16 online issue of

Nature

, Medscape Medical News reports.

The result of the two analyses, conducted by researchers from the Wellcome Trust Sanger Institute here, is that the entire genome of malignant melanoma and lung cancer has been sequenced.

According to the studies’ authors, cancer is driven by mutation, and all cancer cells carry genetic noninherited mutations that have accumulated as the cells progress to disease. The more than 100 different types of cancer have one thing in common: They develop as a result of the acquisition of somatic mutations during a person’s lifetime.

For both malignant melanoma and lung cancer, the researchers say they have uncovered imprints of these mutagens on DNA, which occur years before a tumor becomes evident.

Some of these somatic alterations, called driver mutations, are implicated in cancer development, the researchers say. The remaining mutations are “passengers,” so called because though they do not contribute to oncogenesis; they carry imprints of the mutational mechanisms that have generated them. Thus, they can provide insight into the cause and pathogenesis of cancer.

The malignant melanoma study notes that while this form of cancer comprises only 3 percent of skin cancer cases, it causes 75 percent of deaths attributed to skin cancer. In this analysis, the researchers sequenced COLO-829, a cancer cell line that was derived, before therapy, from a metastasis of a malignant melanoma in a 43-year-old man.

The authors write that a total of 33,345 base somatic substitutions were identified, providing what they say is “the first comprehensive catalogue of somatic mutations from an individual cancer.” The catalogue represents a cumulative record of all mutational events that have occurred during the lineage of cell divisions, beginning with the fertilized egg and ending in the cancer cell.