The use of bacteria in the regression of
tumors has long been known. Various approaches for using bacteria in
cancer therapy include the use of bacteria as sensitizing agents for
chemotherapy, as delivery agents for
cancer drugs and as agents for gene therapy. The
tumor regression stimulated by infecting microorganisms has been attributed to activation of the immune system of the host. However, recent studies indicate that when
tumor-harboring mice with defective immune systems are infected with certain microorganisms, the regression of the
tumor is still observed, suggesting that there are other host factors contributing to the microbial associated regression of
tumors. Since the use of live or attenuated bacteria for
tumor regression has associated toxic effects, studies are in progress to identify a pure microbial metabolite or any component of the microbial cell that might have anti-
cancer activity. It has now been demonstrated that a redox
protein from Pseudomonas aeruginosa, a
cupredoxin, can enter into human
cancer cells and trigger the apoptotic cell death. In vivo, this
cupredoxin can lead to the regression of
tumor growth in immunodeficient mice harboring xenografted
melanomas and
breast cancer tumors without inducing significant toxic effects, suggesting that it has potential anti-
cancer activity. This
bacterial protein interacts with p53 and modulates mammalian cellular activity. Hence, it could potentially be used as an anti-
cancer agent for solid
tumors and has translational value in
tumor-targeted or in combinational-biochemotherapy strategies for
cancer treatments. Here, we focus on diverse approaches to
cancer biotherapy, including bacteriolytic and bacterially-derived anti-
cancer agents with an emphasis on their mechanism of action and therapeutic potential.