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BACKGROUND: Bacterial cancer therapy was first trialled in patients at the end of the nineteenth century. More recently, tumour-targeting bacteria have been harnessed to deliver plasmid-expressed therapeutic interfering RNA to a range of solid tumours. A major limitation to clinical translation of this is the short-term nature of RNA interference in vivo due to plasmid instability. To overcome this, we sought to develop tumour-targeting attenuated bacteria that stably express shRNA by virtue of integration of an expression cassette within the bacterial chromosome and demonstrate therapeutic efficacy in vitro and in vivo. RESULTS: The attenuated tumour targeting Salmonella typhimurium SL7207 strain was modified to carry chromosomally integrated shRNA expression cassettes at the xylA locus. The colorectal cancer cell lines SW480, HCT116 and breast cancer cell line MCF7 were used to demonstrate the ability of these modified strains to perform intracellular infection and deliver effective RNA and protein knockdown of the target gene c-Myc. In vivo therapeutic efficacy was demonstrated using the Lgr5creERT2Apcflx/flx and BlgCreBrca2flx/flp53flx/flx orthotopic immunocompetent mouse models of colorectal and breast cancer, respectively. In vitro co-cultures of breast and colorectal cancer cell lines with modified SL7207 demonstrated a significant 50-95% (P < 0.01) reduction in RNA and protein expression with SL7207/c-Myc targeted strains. In vivo, following establishment of tumour tissue, a single intra-peritoneal administration of 1 × 106 CFU of SL7207/c-Myc was sufficient to permit tumour colonisation and significantly extend survival with no overt toxicity in control animals. CONCLUSIONS: In summary we have demonstrated that tumour tropic bacteria can be modified to safely deliver therapeutic levels of gene knockdown. This technology has the potential to specifically target primary and secondary solid tumours with personalised therapeutic payloads, providing new multi-cancer detection and treatment options with minimal off-target effects. Further understanding of the tropism mechanisms and impact on host immunity and microbiome is required to progress to clinical translation.
RESUMO
PURPOSE: The purposes of this study were to determine if young children with rampant dental caries that received complete dental rehabilitation under general anesthesia: 1.) weighed less preoperatively compared to national norms; and 2.) demonstrated significant improvement postoperatively in percentile weight gain and/or quality of life indicators. METHODS: The preoperative and postoperative percentile weights based on national norms were calculated for children, aged 2-7 years old, with non-significant medical histories (absence of systemic illness) that underwent rehabilitation for rampant dental caries under general anesthesia. Changes in the quality of the children's life following dental rehabilitation under general anesthesia were determined from parental report. RESULTS: The results showed that there was a slight, non-significant increase in the mean percentile weight following dental rehabilitation under general anesthesia. There was no significant effect on the mean net percentile weight change based on the chronological age or weighing interval. There was, however, a significant improvement in the children's quality of life as reported by their parents. CONCLUSIONS: Contrary to previous reports, the mean percentile weight of children with rampant dental caries was not below the 50th percentile and the slight gain in percentile weight following dental rehabilitation under general anesthesia was not indicative of a "catch-up growth" phenomenon. There was, however, a significant improvement in the children's quality of life as based upon parental report and confirmed in a previous investigations.