Research News
Gene Studies Reveal Breast Cancer Evolution
Thanks to dramatic advances in genome sequencing, a multi-institutional team of researchers in British Columbia, Canada, has for the first time sequenced the entire genome of a matched set of tumor samples taken from the same patient nine years apart. By comparing the results of the two sequences, the investigators have shown that significant evolution can occur when breast cancers progress from low- or intermediate-grade disease to metastatic disease. This study has also identified several RNA editing changes that may be important in the spread of cancer.
In reporting its work in the journal Nature, the research team led by Samuel Aparicio, Ph.D., and Marco Marra, Ph.D., both of the BC Cancer Agency, presented genomic data for a matched pair of samples taken from a patient with lobular breast cancer, a type of breast cancer that accounts for about 10% of all forms of this disease. Their analysis identified 32 coding mutations in the metastatic tumors, 19 of which were not present in the original primary tumor. Only five of the mutations identified in the metastatic tumor sample were abundant in the primary tumor, suggesting that the majority of mutations identified in the metastatic tumors were not involved in tumor initiating processes. None of the five mutations present in the primary tumor were suspected, prior to this study, of being involved in the origins of breast cancer.
The investigators then examined the two samples’ transcriptome, the RNA molecules that a cell produces at the direction of its genes. This analysis identified two gene transcripts were edited in the metastatic tumors, producing new proteins whose functions have yet to be identified. The researchers noted that the primary enzyme involved in RNA editing was in the top 5% of all genes expressed in the metastatic cells.
The details of this study appear in a paper titled, “Mutational evolution in a lobular breast tumour profiled at single nucleotide resolution.” An abstract of this paper is available at the journal’s Web site.
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