NEW YORK (GenomeWeb News) – Mutation patterns in 50 breast cancer genomes are offering new insights into the genetic complexity of the disease, Washington University oncologist Matthew Ellis reported at the American Association for Cancer research annual meeting in Orlando this weekend.
"Cancer genomes are extraordinarily complicated," Ellis said in a statement, adding the result of his and his colleagues research "explains our difficulty in predicting outcomes and finding new treatments."
Last year, researchers from Washington University's Genome Institute and elsewhere published a study in Nature describing findings for a triple negative breast cancer genome and matched normal genome from an African American woman.
For the current study, Ellis and co-workers sequenced matched tumor-normal samples from 50 women with estrogen receptor positive breast cancers to about 30 times coverage each.
The samples were obtained through an American College of Surgeons Oncology Group clinical trial, in conjunction with collaborators from Washington University School of Medicine and Barnes-Jewish Hospital's Alvin J. Siteman Cancer Center.
Despite detecting a preponderance of mutations — more than 1,700 overall — the researchers found just a handful of genes were altered in multiple tumor samples.
Among them: PIK3CA and TP53, genes that have been implicated in past studies of breast cancer. In the 50 tumors tested, researchers saw PIK3CA mutations in around 40 percent of tumors and TP53 mutations in roughly one-fifth of tumors.
Three additional genes — MAP3K1, ATR and MYST — were each mutated in about 10 percent of the breast cancers, while another 21 genes were significantly linked to breast cancer but mutated in tumors from just two or three of the women.
Because 24 of the 50 tumors tested came from women whose cancers were known to be resistant to an estrogen-lowering treatment given prior to surgery, the team hopes that the whole-genome data will also provide clues to the sorts of treatment resistance mechanisms that exist in ER-positive breast cancers.
Moreover, those involved in the study are keen to use information from the newly sequenced genomes as a jumping off point for new breast cancer treatment strategies — particularly for genes that are already being considered as possible drug targets in other types of cancer.
"We get good therapeutic ideas from the genomic information," Ellis said. "The near-term goal is to use information on whole genome sequencing to guide a personalized approach to the patient's trea