Sinigrin is present in significant amounts in cruciferous vegetables. Epidemiological studies suggest that the consumption of such vegetables decreases the risk of cancer, and the effect is attributed mainly to allyl isothiocyanate (AITC), a hydrolysis product of sinigrin catalyzed by myrosinase. Anticancer activity of AITC has been previously investigated for several cancer models, but less attention was paid to delivering AITC on the target site. In this study, the gene sequences of core streptavidin (coreSA) and myrosinase (MYR) were cloned in a pET-30a(+) plasmid and transformed into BL21(DE3) E. coli competent cells. The MYR-coreSA chimeric protein was expressed and purified using immobilized metal affinity chromatography and further characterized by gel electrophoresis, Western blot, and enzyme activity assay. The purified MYR-coreSA chimeric protein was tethered on the outer membrane of biotinylated adenocarcinoma A549 cells and then treated with various concentrations of sinigrin. Our results showed that 20 µM of sinigrin inhibited the growth of A549 cells tethered with myrosinase by ~60% in 48 h. Furthermore, the levels of treated cells undertaken apoptosis were determined by Caspase-3/7 activation and Annexin-V. In summary, sinigrin harnessed like a prodrug catalyzed by myrosinase to the production of AITC, which induced cell apoptosis and arrested the growth of lung cancer cells.
The limited amount of fusion protein transported into cytosol milieu has made it challenging to obtain a sufficient amount for further applications. To avoid the laborious and expensive task, T7 promoter-driving pET-30a(+) coding for chimeric gene of thymidine phosphorylase and core streptavidin as a model system was constructed and transformed into a variety of E. coli strains with T7 expression system. Our results demonstrated that the pET-30a(+)-TP-coreSA/Lemo21(DE3) system is able to provide efficient expression of soluble TP-coreSA fusion protein for purification. Moreover, the eluted TP-coreSA fusion protein tethered on biotinylated A549 carcinoma cells could effectively eliminate these malignant cells after administrating prodrug 5′-DFUR.
In the area of gene-directed enzyme prodrug therapy (GDEPT), using herpes simplex virus thymidine kinase (HSV-tk) paired with prodrug ganciclovir (GCV) for cancer treatment has been extensively studied. It is a process involved with two steps whereby the gene (HSV-tk) is first delivered to malignant cells. Afterward, non-toxic GCV is administered to that site and activated to cytotoxic ganciclovir triphosphate by HSV-tk enzyme expressed exogenously. In this study, we presented a one-step approach that both gene and prodrug were delivered at the same time by incorporating them with polymeric micellar nanovectors. GCV was employed as an initiator in the ring-opening polymerization of ε-caprolactone (ε-CL) to synthesize hydrophobic GCV-poly(caprolactone) (GCV–PCL), which was furthered grafted with hydrophilic chitosan to obtain amphiphilic polymer (GCV–PCL–chitosan) for the fabrication of self-assembled micellar nanoparticles. The synthesized amphiphilic polymer was characterized using Fourier transform infrared spectroscopy and proton nuclear magnetic resonance. Micellar prodrug nanoparticles were analyzed by dynamic light scattering, zeta potential, critical micelle concentration, and transmission electron microscopy. Polymeric prodrug micelles with optimal features incorporated with HSV-tk encoding plasmids were cultivated with HT29 colorectal cancer cells and anticancer effectiveness was determined. Our results showed that prodrug GCV and HSV-tk cDNA encoded plasmid incorporated in GCV–PCL–chitosan polymeric nanocarriers could be delivered in a one-step manner to HT-29 cells and triggered high cytotoxicity.
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