# Bacteriotherapy in Breast Cancer
## 4 Bacteria as a Carrier for Cancer Therapeutic Agents  
### Salmonella Typhimurium  
_Salmonella typhimurium_ is a pathological gram-negative bacteria found in the intestinal lumen. Toxicity activity of _Salmonella typhimurium_ is due to an outer membrane feature of lipopolysaccharideaccharides (LPS), which protect it from the environment. Various studies have demonstrated that the attenuated strains of _Salmonella_ can provide the anticancer activity [96] (Table 4).  
These attenuated strains have the potential for selective amplification and to be selectively infected within tumors. Hence, these bacteria are able to be used as a vehicle to target human tumors in vivo. Furthermore, they could express effector genes that encode the therapeutic proteins. It was indicated in a study that _Salmonella typhimurium_ was attenuated by chromosomal deletion of the _pur1_ and _msbB  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Bacteria as a** & **Source** & **Breast Cancer Cell** & **Other Human Cancer Cells/Cell Lines** & **Clinical Phase** & **Ref** \\ \hline \multirow{4}{*}{_Salmonella typhimurium_} & & MDA-MB-435, & \multirow{4}{*}{\begin{tabular}{} \end{tabular} } & Metastatic melanoma & \multirow{4}{*}{Phase I} & \multirow{4}{*}{[97; 98; 99]} \\  & & MDA-MB-361, & & \\  & & MDA-MB-231, 4T1, & & & \\  & & Caco2, RKO, and & & & \\  & & MCF & & & \\  & & & & & \\  & & & & & \\ \hline \multirow{4}{*}{\
\begin{tabular}{} \end{tabular} } & \multirow{4}{*}{
\begin{tabular}{} \end{tabular} } & MDA-MB-231 & Metastatic melanoma & \multirow{4}{*}{Phase I} & \multirow{4}{*}{[97; 98; 99]} \\  & & MDA-MB-363, & & (MDA-MB-435, B16-F10), & & \\  & & MDA-MB-231, 4T1, & & human glioblastoma & \\  & & & MDA-MB-231, 4T1, & & (U87 NG), human pancreatic & \\  & & & Caco2, RKO, and & & (ASPC-1), colon & \\  & & & MCF & & (ASPC-1), colon & \\  & & & & carcinoma (WiDr, CT26) & \\  & & & & & \\  & & & & & (ASPC-1), colon &genes to raise safety and decrease the cytotoxic effect [97]. The _Purl_ gene was deleted to increase dependence and the requirement for an external source of adenine [98]. The deletion of the _msbB_ gene was associated with reducing toxicity by decreasing the stimulation of proinflammatory cytokines (TNF\(\alpha\)) and nitric oxide [106]. The genes that delete strains are genetically stable; they have no antibiotic resistance markers, can decrease the tumor growth, prolong survival, and increase the number of bacteria in the tumor. The attenuated _Salmonella typhimurium_ shows the anticancer activity against various cell lines of breast cancer, including MDA-MB-435, MDA-MB-361, MDA-MB-231, 4T1, Caco2, RKO, and MCF7 [99]. The attenuated strains of _S. typhimurium_, which are labeled by green fluorescent protein (GFP), are also auxotrophic for leucine and arginine, termed a _S. typhimurium A1_. This amino acid auxotrophic bacterium has unique antitumor efficacy, which can selectively grow in the viable tumor tissue and throughout the tumor including the viable malignant tissue. In addition, intravenous or intratumoral injection indicated that there were not any obvious side effects on the host. To increase the tumor-targeting capability of A1 the strain was re-isolated, by a study, after infection of the human colon tumor growing in nude mice, termed A1-R; with this passage through the HT-29 tumor, the ability of A1 was increased to adhere to and invade tumor cells [18]. The result of this study demonstrated that A1-R bacteria can be targeted, colonized, and replicated in the human MARY-X breast tumors growing s.c. in nude mice, as observed by fluorescence imaging on the second day after intravenous injection. The intravenous injection highly effected the targeting of the tumor and regressed human breast cancer. Moreover, the treated animals were completely cured and survived [18] (Table 4) (Figure 1).