Use of a genetically engineered E. coli overexpressing ß-glucuronidase accompanied by glycyrrhizic acid, a natural and anti-inflammatory agent, for directed treatment of colon carcinoma in a mouse model.

Bacteria-directed enzyme prodrug therapy (BDEPT), is an emerging alternative directed and tumor-specific approach. The basis of this method is the conversion of a non-toxic prodrug by a bacterial enzyme to a toxic drug within the tumor-microenvironment (TME). In the present study, the therapeutic efficacy of BDEPT was investigated based on the ability of Escherichia coli DH5α-lux/ßG in activation of glycyrrhizic acid (GL), a natural and non-toxic compound purified from licorice, to glycyrrhetinic acid (GA) only in TME. To do so, the anti-bacterial effects of GL on bacteria and the cytotoxic effects of the produced GA on survival rate of CT26 mouse colon carcinoma cells were evaluated. The IC50 values of the produced GA and cisplatin were determined as 210 µM and 100 µM, respectively. Comparing these values to GL treatment (1305 µM) indicates that bacteria could have efficiently activated GL to GA to inhibit the growth of tumor cells. Afterward, the anti-cancer effects of bacteria used in combination with GL was investigated in a mouse model of colon carcinoma. Results were indicative of targeted homing and even proliferation of luminescent bacteria in TME. Moreover, combined treatment greatly inhibited tumor growth. Histopathological analysis of dissected tissues also demonstrated increased apoptosis rate in tumor cells after combined treatment and interestingly, showed no obvious damage to the spleen and liver of treated mice. Accordingly, this BDEPT approach could be considered as an effective alternative tumor-specific therapy utilizing prodrug-activating enzymes expressing from tumor-targeting bacteria to allow the development of new tumor-specific pharmacotherapy protocols.

Coadministration of auraptene and radiotherapy; a novel modality against colon carcinoma cells in vitro and in vivo.

Background: Use of ionizing radiation (IR) is a common therapeutic modality for patients with colon carcinoma, although resistance of cancer cells and unintended toxicity reduce clinical outcomes.Purpose: To enhance radioresponse of colon cancer cells, we designed a novel approach using auraptene (AUR) in combination with ionizing radiation (IR).Methods: For in vitro studies, CT26 cells were pretreated with AUR and irradiated at different doses. Then, cell viability was evaluated by alamarBlue assay, and the mechanism of cell death was elucidated using annexin V-PI. To determine efficacy of our combined therapeutic modality in vivo, AUR was injected intraperitoneally to murine models of colon carcinoma followed by IR, and then quantitative measurements and histopathological examinations were performed. For molecular analyses, real time PCR and Western blot were carried out.Results: Assessment of cell viability indicated significant enhancement of IR effects by AUR that was also confirmed by increased number of apoptotic cells. In vivo studies further demonstrated improved outcome in IR, since significant regression in tumor size was observed after administration of AUR + IR. Molecular analyses revealed down regulation of Cyclin D1 and CD44, along with involvement of PI3K-AKT-mTORC signaling pathway and Caspase-3 in observed combinatorial effects.Conclusion: Taken together, current findings support our previous reports on sensitizing effects of AUR and that AUR could be used as a promising adjunct to IR in cancer treatment.