Previous studies have shown that TGFb regulates normal cell growth and movement.
But in the newest study, the team from Cancer Research UK used an advanced microscopy and analysis technique in mice, to document the movement of cancer cells from primary breast tumor sites.
The researchers found that when TGFb turned messenger genes in cancer cells on and off, single breast cancer cells were able to break away from the main tumor and enter the blood stream.
When TGFb was inactive, only clumps and not single breast cancer cells were able to break away.
Those clumps are only able to travel through the lymphatic system, not the blood, so the spread of cancer was local.
"The results helped us to find the set of genes that are behind the spread of breast cancer, and that the genes need to be first turned on and then off in order for single cancer cells to be able to "relocate,"" said the study's author Erik Sahai.
The find could lead to promising new drugs that target TGFb and prevent the spread of metastatic breast cancer.