Plenary Session – December 5, 2018
The best talk I heard on Wednesday at the San Antonio Breast Cancer Symposium was the plenary lecture presented by Nicholas Navin of the UT MD Anderson Cancer Center in Houston.
The talk, “Breast Tumor Evolution and Intratumor Heterogeneity — Insights from Single Cell Genomics,” focused on scientists’ use of single cell genomics to understand how ductal carcinoma in situ (DCIS) evolves into invasive cancer.
We have long assumed that precancerous cells start in the milk ducts and then develop a mutation that allows them to break out of the duct and invade the surrounding tissue. Navin’s research showed that this is not always true. When they sequenced the DNA of the DCIS and its associated invasive tumor, they found that in most cases the mutations seen in the DCIS were also in the invasive breast cancer. But in other instances, However, additional mutation were found in the invasive cancer that were not seen in the DCIS. This suggests that it is the stroma or the neighborhood around the cells that influences whether a cell from DCIS can invade, and not a new mutation that occurs in the cells themselves.
Navin reported that his research also found a direct genomic lineage between in situ and invasive tumor subpopulations, with most mutations and copy number aberrations evolving within the ducts prior to invasion. These results support a multi-clonal invasion model, in which one or more clones escape the ducts and migrate into the adjacent tissues to establish the invasive carcinomas.
It’s always fascinating to have our long-held assumptions questioned!