ABSTRACT
Objective:To investigate the influence of bacterial outer membrane vesicles (OMVs) tumor vaccine on tumor cell proliferation and CD8 + T cell infiltration of mouse with pancreatic cancer. Methods:The experimental study was conducted. The ovalbumin (OVA) lentivirus vector plasmid pLV-EF1a-hluc-P2A-mNeongreen-CMV-OVA-3Xflag-P2A-puro was used to construct the mouse pancreatic cancer Pan02-OVA cells. The ClyA-Catchers-OMVs (CC-OMVs) originated from Escherichia coli and labeled antigenic peptide SpyTag-OVA were used to construct the OMVs tumor vaccine. Mouse CD8 + T cells were stimulated by OMVs tumor vaccine, and the effects of OMVs tumor vaccine on inhibiting pancreatic cancer cells proliferation and stimulating CD8 + T cell infiltration were analy-zed by in vitro cell killing assay, including the OMVs tumor vaccine stimulated T cell group and the control T cell group, subcutaneous pancreatic cancer model, including the OMVs tumor vaccine group and the control group, and immunohistochemical staining. Observation indicators: (1) identification of mouse pancreatic cancer Pan02-OVA cells; (2) morphological observation of CC-OMVs; (3) inhibi-tion of mouse pancreatic cancer Pan02-OVA cells by OMVs tumor vaccine specific T cells; (4) inhibi-tion of mouse pancreatic cancer by OMVs tumor vaccine; (5) CD8 + T cell infiltration in pancreatic cancer tissue of mouse stimulated by OMVs tumor vaccine. Measurement data with normal distribu-tion were represented as Mean± SD, and comparison between groups was analyzed using the t test. Count data were described as absolute numbers or percentages. Results:(1) Identification of mouse pancreatic cancer Pan02-OVA cells. Results of laser scanning confocal microscopy showed that the mNeongreen fluorescence was expressed in Pan02-OVA cells infected with the OVA lentivirus vector plasmid of pLV-EF1a-hluc-P2A-mNeongreen-CMV-OVA-3Xflag-P2A-puro. Results of Flow cytometry showed that using the mouse pancreatic cancer Pan02 cells as references, the protein expression rate of Flag on the Pan02-OVA cells was 90.7%. (2) Morphological observation of CC-OMVs. Results of transmission electron microscopy analysis showed that the CC-OMVs were in spherical shape, with a diameter <50 nm. (3) Inhibition of mouse pancreatic cancer Pan02-OVA cells by OMVs tumor vaccine specific T cells. Results of cell proliferation toxicity test showed that the absorbance at 450 nm of mouse pancreatic cancer Pan02-OVA cells was 0.41±0.12 and 1.05±0.15 in the OMVs tumor vaccine-stimulated T cell group and the control T cell group, respectively, showing a significant difference between the two groups ( t=9.54, P<0.05). (4) Inhibition of mouse pancreatic cancer by OMVs tumor vaccine. The weight of subcutaneous tumor tissue in the back of mouse was (81±10)g and (153±17)g in the OMVs tumor vaccine group and the control group, respectively, showing a significant difference between the two groups ( t=8.26, P<0.05). (5) CD8 + T cell infiltration in pancreatic cancer tissue of mouse stimulated by OMVs tumor vaccine. Results of immuno-histochemical staining showed that the numbers of CD8 + T cells staining in the mouse back subcu-taneous tumor tissues was 28.7±3.5 and 9.3±1.5 in the OMVs tumor vaccine group and the control group, respectively, showing a significant difference between the two groups ( t=8.74, P<0.05). Conclusion:Bacterial OMVs tumor vaccine can inhibit proliferation of pancreatic cancer cells and increase the numbers of CD8 + T cells infiltrated in pancreatic cancer tissue of mouse.
ABSTRACT
More efficient drug delivery system and formulation with less adverse effects are needed for the clinical application of broad-spectrum antineoplastic agent doxorubicin (DOX). Here we obtained outer-membrane vesicles (OMVs), a nano-sized proteoliposomes naturally released by Gram-negative bacteria, from attenuated and prepared doxorubicin-loaded O0MVs (DOX-OMV). Confocal microscopy and distribution study observed that DOX encapsulated in OMVs was efficiently transported into NSCLC A549 cells. DOX-OMV resulted in intensive cytotoxic effects and cell apoptosis as evident from MTT assay, Western blotting and flow cytometry due to the rapid cellular uptake of DOX. In A549 tumor-bearing BALB/c nude mice, DOX-OMV presented a substantial tumor growth inhibition with favorable tolerability and pharmacokinetic profile, and TUNEL assay and H&E staining displayed extensive apoptotic cells and necrosis in tumor tissues. More importantly, OMVs' appropriate immunogenicity enabled the recruitment of macrophages in tumor microenvironment which might synergize with their cargo DOX . Our results suggest that OMVs can not only function as biological nanocarriers for chemotherapeutic agents but also elicit suitable immune responses, thus having a great potential for the tumor chemoimmunotherapy.
ABSTRACT
Objective@#To establish a labeling method for bacterial outer membrane vesicle (OMV) based on luciferase reporting gene. @*Methods@#By utilizing the characteristics that high abundance of outer membrane protein A (OmpA) presented on the surface of bacterial OMV, the outer membrane protein-luciferase fusion protein was constructed to position the luciferase on the surface of the outer membrane vesicle, and the number of bacterial OMV was evaluated based on the luciferase activity. @*Results@#The OmpA-NanoLuc fusion protein expression vector was constructed successfully, and the outer membrane vesicles secreted by the subject strains after the expression of the fusion protein displayed stable luciferase activity. The number of bacterial outer membrane vesicles was semi-quantitative detrmined by measuring the activity of fluorescein enzyme. @*Conclusion@#A semi-quantitative method based on luciferase labeling was developed for the detection of extracellular vesicles, which could be used to evaluate the secretion level of specific strains.