More than a century ago, physician William Coley observed that some patients with bacterial infections were able to fight off cancer. Following years of unsuccessful attempts to harness bacteria as a cancer therapy, scientists have announced some encouraging developments.
After Coley’s initial observations, scientists discovered that Clostridium bacteria thrived in certain parts of cancerous tissue as a result of rapid tumor progression.
Tumors spread and sustain themselves by growing new blood vessels. However some tumors progress so fast that the interior cancer tissue becomes starved of blood and oxygen creating a necrosis of cells in that area.
Those conditions limit the effectiveness of conventional treatments like chemotherapy and radiation because drugs cannot be delivered in lethal amounts and radiation therapy requires oxygen to trigger apoptosis. When treatments fail or only kill surrounding tissue, the cancerous cells in those regions begin to regenerate.
While conventional treatments are limited in targeting those areas, the low oxygen supply creates the perfect environment for anaerobic bacteria. The bacteria literally devour cancer cells and because they are anaerobic they die when they reach healthy oxygen rich tissue. However that includes the tumor’s perimeter making this therapy ineffective as a sole treatment.
Knowing that limitation, researchers at Johns Hopkins combined the bacteria with chemotherapy during a recent clinical trial.
Researchers tested 26 strains of anaerobic bacteria on a group of eight mice by injecting it directly into tumors. Seven of the animals saw a large decrease in tumor volume including several instances where the tumor completely disappeared. The success of the treatment was so rapid that one scientist commented that you could almost see it dying in real time.
However three of the eight mice died afterwards and researchers believe this was caused by their circulatory system being clogged by dead cells and bacteria resulting from the therapy. Researchers are optimistic this won’t be a problem for humans considering the larger volume of the circulatory system.
Scientists are also concerned about the effectiveness of the treatment on smaller tumors and at what point bacteria therapy can be considered as an adjuvant therapy for a cancer patient.
The next step is to continue testing on larger animals and if that is successful then a human trial could be a few years away.