Scientists Decode Genome in Highly Lethal Breast Cancer

Metastatic tumors may originate from a small number of primary tumor cells

WEDNESDAY, April 21 (HealthDay News) -- By looking at structural variation patterns and differential mutation frequencies between primary tumor cells, metastatic tumor cells, and xenograft tumor cells from a highly lethal form of breast cancer, scientists have found evidence that some metastatic tumors may originate from only a small number of cells within the primary tumor, according to a study in the April 15 issue of Nature.

Li Ding, Ph.D., of Washington University in St. Louis, and colleagues used DNA sequencing technology to perform genomic analyses of four DNA samples from a 44-year-old African-American woman with basal-like breast cancer: peripheral blood, a brain metastasis, a xenograft derived from the primary tumor, and the primary tumor itself.

The researchers identified a wide range of mutant alleles in the primary tumor cells, which suggested a broad genetic heterogeneity of the original tumor. However, the range of mutation frequency was much smaller and overlapping in both the brain metastasis and the xenograft. This finding suggested that cell selection in the xenograft was similar to that which occurred in the metastasis.

"The first completed basal-like breast cancer genome is highly complex, as would be anticipated for a tumor type associated with chromosomal instability and DNA repair defects. Future studies should extend our analysis approach of primary, metastatic and normal tissue trios and include affected individuals with diverse geographic origins to produce a complete catalogue of recurrent somatic and inherited variants associated with the development of this common malignancy," the authors write.

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