Early-stage breast cancer may contain motile cells
Researchers at the Salk Institute for Biological Studies suggest that although tumour cells during the early-stage of breast cancer do not appear to be invasive, they may already contain motile cells that can wander off via milk duct and start a new tumour somewhere else in the same breast. This discovery is important because the cancer cells may become migratory earlier than expected, and this will change the treatment approach.
Thanks to advances in screening programs, most breast tumours are discovered when they are still confined to the duct, the most common site for invasive breast cancer, before they become invasive. These tumours are known as DCIS (ductal carcinoma in situ). Currently, the standard treatment for DCIS is lumpectomy, the surgical removal of the tumor and surrounding tissue. About 16% of the patients who have received lumpectomy develop breast cancer again within 5 years. Gamma radiation is considered after the surgery to reduce the risk of recurrent cancer. The decision is made based on the size of the tumour.
Now with this new finding, when DCIS contain motile cells, the patient should receive radiation therapy regardless of the tumour size. However, the researchers have yet to show that these wandering cell do indeed affect the outcome of the disease.
What the scientists did was using a tissue culture model by isolating human breast cells and embedding them in a 3-D matrix. These cells spontaneously developed acini, hollow structures similar to milk ducts. And then they turned on the ERK1/2 MAP kinase pathway, a signaling cascade frequently activated during the development of tumors. Within 24 hours, the motile cells were observed. While these cells could escape the basement membrane, they were limited to the ERK-activated acini. However, their potential barrier to become invasive in the future had been lowered.
The next step is to find molecular markers for these wandering cells to help the oncologist find patient at higher risk for metastasis.