Table I.

Details of engineered microbes used in cancer therapy studies in past 7 years. Table adopted and modified with permission from Sieow et al. (24)

Bacteria	Therapeutic payload	Animal model/ cell lines	Outcome	Reference
Escherichia coli	CD47 nanobody	BALB/c or C57BL/6 mice bearing A20, 4 T1, and B16-F10 tumours	Intratumoural injection of engineered microbe increased activation of tumour-infiltrating T cells and stimulated significant tumour regression in various tumour-bearing mouse models; treatment also triggered systemic tumour antigen-specific immune responses, because additional tumours that did not receive intratumoural injections experienced slightly weaker growth inhibition.	(25)
	Expression of myrosinase to convert dietary glucosinolate into sulforaphane	Azoxymethane (AOM) and dextran sulphate sodium (DSS)-induced tumours in BALB/c mice	Significant inhibition of tumour growth and tumour counts (~75% reduction) in colorectal region of induced-colorectal cancer mice.	(26)
	Expression of biosynthetic gene clusters of glidobactin, luminmide, and colibactin	Female NMRI nude mice bearing UT-SCC-5 tumours	Colibactin-producing EcN significantly inhibited tumour growth in mice (25% of tumour weight of control group); glidobactin and luminmide-producing EcNs also inhibited tumour growth in mice but to a lesser degree (~50% of tumour weight of control group).	/ (27)
E. coli Nissle	Tum-5	C57BL/6 mice bearing B16-F10 melanoma	Significantly inhibited solid tumour growth in mice; inhibited neovascularization in tumour areas; reduced expression of PECAM-1.	(28)
	Tum-5 and p53	BALB/c nude mice bearing SMMC-7721 tumours	Significantly inhibited solid tumour growth in mice; inhibited neovascularization in tumour areas; combined administration of p53 and Tum-5 more potent than single administration of either therapeutic protein.	(29)
	PD-L1 and CTLA-4 nanobodies	GM-CSFBALB/c mice bearing A20 and CT26 tumours	Increased systemic memory T cell populations, increased activation of tumour-infiltrating T cells, and stimulated significant tumour regression in mice. Combined administration of PD-L1nb, CTLA-4nb, and GM-CSF was more potent than single or combined administration of the two immune checkpoint nanobodies	(30)
	Expression of diadenylate cyclase to synthesize STING-agonist cyclic di-AMP	Specific pathogen-free mice bearing B16-F10 and A20 tumours	Significant dose-dependent tumour rejection of B16-F10 and A20 tumour-bearing mice. Percentage survival of mice also dependent on administered therapeutic dose	(31)
Salmonella typhimurium	IFN-γ	C57BL/6 mice bearing B16-F10 tumours	Significant NK cell-dependent inhibition of B16-F10 melanoma tumour growth and prolonged survival in B16-F10 mouse tumour model	(32)
	Vibrio vulnificus flagellin	BC57BL/6 mice bearing MC38 and HCT116-luc2 tumours	Significant suppression of MC38 tumour growth and prolonged survival in MC38 mouse tumour model; suppressed tumour growth and metastasis in HCT116 xenograft model; Induction of M1-like macrophage polarization, which secretes tumour-suppressive cytokines and nitric oxide.	(33)
	Endostatin	BALB/c mice bearing CT26 tumours and C57BL/6 mice bearing B16-F10 melanoma	Increased apoptosis level and suppression of tumour angiogenesis within tumour tissues.	(34)
	hlyE and 5-FU (chemo drug); hlyE, CCL21, and CDD-iRGD	BALB/c mice bearing MC26-LucF tumours	Significantly inhibited tumour growth and prolonged survival of mice. Combined administration of therapeutics showed better efficacy than administration of each therapeutic individually.	(35)
	TGFα-PE38	BALB/c mice bearing CT26 and 4 T1 tumours and C57BL/6 mice bearing MC38 tumours	Release of TGFα-PE38 by phage lysis system and secretion via signal peptide significantly inhibited solid tumour growth in mice and prolonged survival.	(36)
	DNase I and triptolide	BALB/c mice bearing B16-F10 tumours	Combination of DNase I delivery and triptolide inhibited tumour growth and enhanced survival rate in mice; at end-point, 26.32% of mice that received both therapeutics had complete elimination of tumours; DNase I monotherapy completely eliminated tumours for 15.79% of treated mice.	(37)
	Expression of L-asparaginase to convert asparagine to aspartateC57	BL/6 mice bearing MC38 tumours	Significant inhibition of tumour growth (75% reduction in size) and prolonged survival in mice (100% survival rate after 20 days)	(38)
	IDO (shIDO) and anti-PD-1 antibody	BALB/c mice bearing CT26 tumours and C57BL/6 mice bearing MC38 tumours	Induced intratumoural cell death in colorectal cancer mouse models; co-administration of anti-PD1 and shIDO was not more effective than shIDO monotherapy.	(39)
	Alpha subunit of inhibin (sh-INHA)	BALB/c mice bearing CT26 tumours and C57BL/6 mice bearing B16-F10 melanoma	Significant inhibition of tumour growth and prolonged survival in mouse models; suppression of INHA expression; induced caspase activation and downregulated expression of antiapoptotic Bcl-2 and Bcl-xL in in vitro studies.	(40)
	sh-PD-1 and Pimozide	C57BL/6 mice bearing B16-F10 melanoma	Combined administration of sh-PD-1 and pimozide induced tumour apoptosis and prolonged survival in mouse models compared with individual monotherapies; also increased tumour infiltration of T cells, increased spleen CD4+ T cells, CD8+ T cells, and NK cells, and reduced spleen Tregs.	(41)
	sh-Sox2 and HM-3 peptide	BALB/c mice bearing A549 tumours	Combined administration of sh-Sox2 and HM-3 peptide induced significant inhibition of tumour growth in mouse models and was more effective than sh-Sox2 monotherapy; HM-3 peptide inhibited microvessel formation in tumours.	(42)
Bifidobacterium longum	420Cell wall-anchored tumour antigen WT1 protein	C57BL/6 N mice bearing C1498-WT1 tumours	Significant inhibition of WT1-expressing tumour growth by WT1 epitope-specific cytotoxic T cells; increased stimulatory cytokine production.	/ (43)
	Tumstatin	BALB/c mice bearing CT26 tumours.	Significantly inhibited tumour growth and induced apoptosis of tumour vascular endothelial cells in CT26 mouse model.	(44)