Lee Parry

Bacterial cancer therapy (BCT) is emerging as an important option for the treatment of solid tumours, with promising outcomes in preclinical trials. Further progress is hampered by an incomplete understanding of how oncotropic bacteria, such as attenuated strains of Salmonella enterica serovar Typhimurium, colonise tumours and the responses of both the bacteria and tumour cells to this colonisation. To model this, we developed organoids that are permissive for bacterial colonisation, replacing the conventional commercially available extracellular matrix (e.g., Matrigel) with a type I collagen matrix scaffold. A comparison of the two extracellular matrices indicated that type 1 collagen permitted an initial infection efficiency more than 5-times greater than with Matrigel. In addition, subsequent growth within type 1 collagen expanded bacterial cell numbers by over 10-fold within 4 days of infection. These organoids allow for the visualisation of bacterial chemoattraction, cell invasion and subsequent population of the interior lumen, and will permit the future optimisation of BCT. In addition, by establishing patient-derived organoids, we demonstrate a platform for developing future personalised treatments exploiting BCT.

Bacterial cancer therapy (BCT) is emerging as an important option for treatment of solid tumours, with promising outcomes in preclinical trials. Further progress is hampered by an incomplete understanding of how oncotropic bacteria, such as attenuated strains of Salmonella enterica serovar Typhimurium, colonise tumours and the responses of both the bacteria and tumour cells to this colonisation. To model this, we have developed organoids that are permissive for bacterial colonisation, replacing conventional commercially available extracellular matrix (e.g. Matrigel) with a type I collagen matrix scaffold. A comparison of the two extracellular matrices indicated that type 1 collagen permitted an initial infection efficiency more than 5 times greater than with Matrigel. In addition, subsequent growth within type 1 collagen expanded bacterial cell numbers by over 10-fold within 4 days of infection. These organoids allow visualisation of bacterial chemoattraction, cell invasion and subsequent population of the interior lumen, and will permit future optimisation of BCT. In addition, by establishing patient-derived organoids, we demonstrate a platform for developing future personalised treatments exploiting BCT.

The links between diet, microbiome, immunity, and colorectal cancer are well established. The metabolite output of the microbiome, which has a large influence over host health and disease, is related to the composition of the diet. These metabolites subsequently impact on immune and intestinal epithelial either directly or indirectly via production of secondary metabolites. Here we summarize the latest findings and briefly discuss their potential for managing disease risk.

Jaboticaba (Myrciaria jaboticaba) is a recognizable and unique crop from Brazil. The fruit’s byproducts are currently being studied, given their bioactive composition and promising anti-cancer potential. It is not evident, however, if different harvesting seasons can modify the chemical profile and antioxidant capacity of jaboticaba fruit fractions. Furthermore, as there is limited data for jaboticaba’s anti-proliferative effects, additional assessments are required to improve the robustness of these findings. Therefore, this study aimed to determine the composition of the peel of jaboticaba collected in two periods (May—off-season, sample 1—and August–October—peak season, sample 2) and test the peel’s richest anthocyanin sample against colorectal cancer (CRC) cell lines. To accomplish this, proximate, spectrophotometric, and chromatographic analyses were performed in two freeze-dried samples; and anti-proliferative and/or colony-forming assays were carried out in Caco-2, HT29, and HT29-MTX cells. As a result, sample 2 showed the highest levels of polyphenols overall, including flavonoids and anthocyanins. This sample displayed significative higher contents of cyanidin-3-O-glucoside (48%) and delphinidin-3-O-glucoside (105%), in addition to a superior antioxidant capacity (23% higher). Sample 1 showed higher amounts of total protein, gallic acid (20% higher), and specific carotenoids. An aqueous extract from sample 2 was tested against CRC, showing anti-proliferative effects for Caco-2 cells at 1 and 2 mg/mL concentrations, with IC50 values of 1.2–1.3 mg/mL. Additionally, the extract was able to inhibit cell colony formation when tested at both low and high concentrations. In conclusion, jaboticaba collected in the main season stands out regarding its polyphenol composition and holds potential against cancer cell growth.

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 Lgr5creER^T2Apc^flx/flx and BlgCreBrca2^flx/flp53^flx/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.

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 1x106 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.