The role of bacteria in cancer therapy - enemies in the past, but allies at present.

In recent decades, bacteria's therapeutic role has aroused attention in medicinal and pharmaceutical research. While bacteria are considered among the primary agents for causing cancer, recent research has shown intriguing results suggesting that bacteria can be effective agents for cancer treatment - they are the perfect vessels for targeted cancer therapy. Several bacterial strains/species have been discovered to possess inherent oncolytic potentials to invade and colonize solid tumors in vivo. The therapeutic strategy of using bacteria for treating cancer is considered to be effective; however, the severe side effects encountered during the treatment resulted in the abandonment of the therapy. State-of-the-art genetic engineering has been recently applied to bacteria therapy and resulted in a greater efficacy with minimum side effects. In addition, the anti-cancer potential of tumor-targeting bacteria through oral administration circumvents the use of the intravenous route and the associated adverse effects. This review aims to provide a comprehensive summary of the latest literature on the role of bacteria in cancer treatment.