pBV222 vector

Currently, the combination therapy of endostatin and chemotherapy drugs is considered a promising anti-tumor treatment strategy. In this study, researchers selected a safe strain of Bifidobacterium longum as a delivery system to transport endostatin to the gastrointestinal tract and explored their combined effect on inflammatory bowel disease (IBD) and colitis-associated cancer. Results showed that B. longum-Endo alleviated dextran sulfate sodium-induced weight loss, diarrhea, colon shortening, and epithelial damage. Long-term oral administration of B. longum-Endo significantly reduced tumor formation rate, tumor number, and tumor size. The levels of potentially beneficial bacteria such as Lactobacillus, Bifidobacterium, Allobacterium, and Bacteroidetes were increased in the B. longum-Endo group compared to the model group and the B. longum group. At the same time, levels of potentially pathogenic bacteria such as Desulfovibrio, Helicobacter, and Enterobacter also decreased. Taken together, these results suggest that oral administration of recombinant B. longum -Endo strains may be a promising therapeutic strategy for the treatment of IBD and colitis-associated cancers.

The complete endostatin gene of 560 bp was amplified from human placental cDNA and cloned into the pPRPL-inducible vector pBV222 (Figure 1A ). The obtained recombinant plasmids pBV222 and pBV222-endostatin were transformed into Lactococcus lactis, Lactobacillus acidophilus, and Bifidobacterium longum, respectively. After induction at 42°C for 8 hours, the total cell protein and secreted protein in the culture supernatant were extracted. As shown in Figure 1B, the expected 22 kDa protein product was successfully expressed in three recombinant strains. Among these recombinant strains, Bifidobacterium longum showed the highest relative expression of endostatin. However, no endostatin band was found in the parental strain carrying the empty vector pBV222 (termed Bifidobacterium longum). Likewise, no fluorescence was observed in the wild-type strain, whereas the recombinant strain carried an obvious fluorescence signal (Figure 1D). These results indicate that endostatin protein is successfully expressed in Bifidobacterium longum. Furthermore, the newly constructed recombinant strains exhibited accelerated growth rates.

Figure 1. Cloning and expression of endostatin in Bifidobacterium longum. (Bi, Zhiqian, et al. 2022)