An experimental treatment based on a naturally occurring protein could offer new hope for women with one of the deadliest breast cancers.
In laboratory tests the protein, Tinagl1, held back the growth and spread of triple-negative breast cancer (TNBC).
Tumour cells of this type lack the three most common “receptors” – bioactive surface molecules – that fuel breast cancer.
They do not respond to hormone treatments, such as tamoxifen, or drugs that block the cancer-driving protein Her2.
TNBC affects about 15% of breast cancer patients.
Around 77% of women with TNBC survive for five years after diagnosis compared with 93% of those with other forms of breast cancer.
Tinagl1 acts on two biological pathways that make TNBC so aggressive and difficult to treat.
First, it targets a mutant tumour-promoting gene, EGFR, that sends out signals telling cancer cells to multiply and spread.
Secondly, it interferes with a protein called focal adhesion kinase (FAK), which fuels cancer cell migration, growth and survival.
Lead researcher Professor Yibin Kang, from Princeton University in the US, said: “People have tried to block the spread of this form of cancer but attempts so far have failed because if you try one approach, the cancer cells compensate by finding a way to escape.
“With this new approach, the treatment blocks both pathways at the same time. It is like having one stone that kills two birds.”
The research is reported in the journal Cancer Cell.
Prof Kang’s team first looked at more than 800 breast tumour samples taken from human patients.
Those with less active Tinagl1 genes were more likely to have come from patients with advanced tumours and shorter survival times.
Tumours containing more of the Tinagl1 protein were more strongly linked to good patient outcomes.
A lab-produced version of the protein was then administered to mice with breast cancer over a seven-week period.
It significantly suppressed tumour growth and cancer spread to the lungs, with no major side-effects.
The treatment appeared to be effective even after tumours had begun to metastasise, or spread, the scientists said.