Clostridial Spores for Cancer Therapy

Solid tumor accounts for 90% of all cancers. The current treatment approach for most solid tumors is surgery; however it is limited to early stage tumors. Other treatment options such as chemotherapy and radiotherapy are non-selective, thus causing damage to both healthy and cancerous tissue.

Recent research has shifted towards understanding the tumor microenvironment and it's differences from that of healthy cells/tissues in the body and then to exploit these differences for treatment of the tumor. One such approach is utilizing anaerobic bacteria. Several strains of bacteria have been shown to selectively colonize in solid tumors, making them valuable tools for selective tumor targeting and destruction.

Clostridium-based cancer therapy is a promising approach for the treatment of solid tumours. Bacterial-based cancer therapy using Clostridium spp. offers a selective advantage in overcoming the obstacles of hypoxia and necrosis. Clostridium spp., being strictly anaerobic will only colonize in areas devoid of oxygen, and when systematically injected, spores germinate and multiply in the hypoxic/necrotic areas of solid tumors. Clostridium, although anaerobic, possesses the ability to sporulate, allowing them to remain dormant in environments where oxygen is present. However, when growth conditions are suitable (i.e., in the hypoxic/necrotic milieu of solid tumors), the Clostridium spores germinate and begin to colonize these areas. This aspect of Clostridium growth is being exploited for use in a number of various novel cancer treatment strategies currently being developed which utilize Clostridium as a vector to deliver therapeutics directly to the solid tumor site. Clostridial vectors can be safely administered as spores, and their efficacy in delivering and secreting therapeutic proteins has been demonstrated in a number of preclinical trials.

Clostridium spp. with spore formation.