The chaga extract was tested on a laboratory sample of cancer, called HepG2.
HepG2 is one of several immortal cell lines, cancer tumours that continued to grow when removed from the body.
The HepG2 cell line has been used continuously since 1975.
Immortal cell lines have been used for testing vaccines, viruses, cancer treatments and more.
The mice from the animal study were similarly infected with a cancer sample discovered in 1951.