Difference between revisions of "Part:BBa K4156119"

Revision as of 03:33, 11 October 2022

XOR gate-HlyE

XOR gate-HlyE consists of an XOR logic gate ( BBa_K4156117 ) and a downstream HlyE ( BBa_K4156084 ) sequence, and tests the performance of the XOR gate by detecting the red fluorescent signal.

Usage and Biology

The construction of this part is similar to XOR gate-mRFP ( BBa_K4156124 ). The difference is that we replaced the mRFP protein with the HlyE therapeutic protein. This is to verify the therapeutic power of the recombinant strain under XOR gate control. After co-incubation of the recombinant strain with cancer cells, cell viability was monitored using the CCK8 assay to assess the therapeutic power of the recombinant strain and the reinforcing effect of the XOR gate.

Characterization

Lactate (plldR) and pH (pPepT)Induced promoter-controlled effector engineered strain co-incubated with RKO cells

Figure 7 shows the RKO cell activity after incubation of each strain in fresh DMEM medium, normoxic conditions(OD=0.6, 30 μl, 3 hours). It can be seen that the RKO relative viability of the experimental groups with the addition of the effector strains in the fresh culture medium did not change significantly compared to the WT group, except for the plac+HlyE positive control. Figure 8 shows the RKO cell activity of each strain after incubation in 3 day DMEM medium, normoxic conditions. It can be concluded that in the 3 day DMEM medium, due to the accumulation of metabolites such as cellular lactate, the lactate promoter and pH promoter were activated in the engineered strains and started to synthesize therapeutic proteins, resulting in a decrease in the relative viability of RKO compared to the WT group, especially in the pLldR+switch+HlyE and pCadC+switch+HlyE groups with the addition of the amplified gene switch. switch+HlyE group with the addition of the amplifying gene switch significantly reduced the RKO relative viability. In contrast, the decrease in RKO relative viability in the pLldR+φ174E+switch+HlyE group and pCadC+φ174E+switch+HlyE group was not significant, probably due to the decrease in the number of bacteria and the decrease in the number of synthesized therapeutic proteins by the addition of lysis genes.

Coincubation of different doses of effector engineered strains (OD=0.6) with RKO cells

Figure 9 shows the RKO cell activity after incubation with different doses of plldR and pCadC control effector strains in 3 day DMEM medium, normoxic conditions. The RKO cell activity decreased with increasing doses of effector strains.

30 μl effector engineered strains (OD=0.6) were co-incubated with RKO cells for different times

Figure 10 shows the RKO cell activity after incubation of plldR and pCadC control effector strains for different times under 3 day DMEM medium, normoxic conditions. It can be seen that the RKO cell activity decreased with the increase of co-incubation time.

Western blot

To verify the extracellular secretion of HlyE, we constructed an AE strain by fusing his tag at the C-terminus of HlyE. Then, the AE strain (HlyE with his tag) was inoculated in 50 ml of LB medium containing the corresponding antibiotics and cultured overnight at 37 °C. Then, 5 ml of the culture was centrifuged and the supernatant was collected. The supernatant was concentrated using the TCA precipitation method (25% TCA, -20°C, 1h) to isolate the total protein. Finally, the expression of HlyE was detected by western blot. The results showed that the constitutive promoter could secrete HlyE under both inducible and non-inducible conditions, while the lactate (plldR), pH (pCadc) and hypoxia (pPepT) inducible reporters could only secrete HlyE under inducible conditions and not under non-inducible conditions. indicated that our constructed AE strain could well cope with environmental induction and secrete HlyE in the tumor microenvironment It was shown that our AE strain could respond well to environmental induction and secrete HlyE in the tumor microenvironment, thus killing cancer cells without harming other normal cells.

Sequence and Features