Human tumors transplanted into laboratory mice disappeared or shrank when scientists treated the animals with a single antibody. This antibody works by masking a protein flag on cancer cells that protects them from macrophages and other cells in the immune system.
The scientists from the Stanford University School of Medicine achieved the findings with human breast cancer, ovarian cancer, colon cancer, bladder cancer, brain cancer, liver cancer and prostate cancer samples.
It is the first antibody treatment shown to be broadly effective against a variety of human solid tumors, and the dramatic response – including some overt cures in the laboratory animals – has the investigators eager to begin phase-1 and -2 human clinical trials within the next two years.
“Blocking this ‘don’t-eat-me’ signal inhibits the growth in mice of nearly every human cancer we tested, with minimal toxicity,” said professor of pathology Irving Weissman, MD, who also directs Stanford’s Institute of Stem Cell Biology and Regenerative Medicine and the Ludwig Center for Cancer Stem Cell Research at Stanford. “This shows conclusively that this protein, CD47, is a legitimate and promising target for human cancer therapy.”
The antibody treatment also significantly inhibited the ability of the tumors to metastasize throughout the animals’ bodies.
“This is exciting work and will surely trigger a worldwide wave of research designed to convert this strategy into useful therapies,” said Robert Weinberg, PhD, a professor of biology at the Whitehead Institute for Biomedical Research in Massachusetts who was not involved in the research. “Mobilizing the immune system to attack solid tumors has been a longstanding goal of many cancer researchers for decades.”
In the current study, the researchers saw that most of the established tumors begin to shrink and even, in some cases, disappear within weeks of treatment with the antibody. In one case, antibody treatment cured five mice injected with the same human breast cancer cells. When the tumor was gone, the treatment was discontinued; the mice were monitored for four months with no signs of recurrence.
“These results indicate that anti-CD47 antibodies can dramatically inhibit the growth of human solid tumors by blocking the ability of CD47 to transmit the ‘don’t-eat-me’ signal to macrophages,” concluded the authors.
Source: Stanford University Medical Center, USA