Difference between revisions of "Team:HZAU-China/Description"

We utilize a newly reported mechanism, the pyroptosis, to treat cancers. Pyroptosis is a lytic form of inflammatory cell death which is mediated by activation of Caspases 1, 3, 4, 5 and 11. The morphology of pyroptosis is characterized by cell swelling and rupturing which causes releasing of cytoplasmic contents of the cell, including proinflammatory cytokines, endogenous ligands, alarmins, ATP and other danger-associated molecular patterns³. What's important is that protein Gasdermin D (GSDMD) has been found as an essential effector of pyroptosis in recent studies. When host cells are defending the infection, full-length Gasdermin D will be cleaved by Caspases and the process will expose the N-terminal of Gasdemin D (PFD, pore form domain) from RD (repressor domain). PFD can oligomerize and form pores on the plasma membrane, sodium and water rush into the cell subsequently, causing the cell rupture. But only applicable in the intracellular side. Simultaneously, cytokines such as IL-1β, IL-18 are released into the extracellular environment through the Gasdermin pores⁴ (Figure 1).

Some points about the relationship of pyroptosis and cancers that are demonstrated in recent studies:

1. Berberine inhibits the viability of HepG2 cell through induction of pyroptosis⁵.

2. Caspase 1 rescues the sensitivity of radiant lethality in prostate cancer, increasing the proportion of death cancer cells after radiation therapy⁶.

3. Nlrp3^-/- mice without pyroptosis pathway are susceptible to catch colitis-associated colon cancer⁷.

These meaningful studies help us to exploit advantage of pyroptosis in tumor therapy.

Our project aims to cure cancer by triggering pyroptosis through translocate the N-terminal of GSDMD (GSDMD-N275). There are many vectors can be choose such as oncolytic virus, macromolecular carrier and bacteria. In our project, we choose Salmonella enterica serovar Typhimurium str. SL1344 as a carrier. The reason why we chose Salmonella as our carrier are based on following reason. First, in consideration of GSDMD-N275 induced pyroptosis only when delivered cytosolically but not extracellularly, Salmonella is a brilliant candidate as a intracellular parasite. Second, Salmonella is a widely used carrier to cancer therapy because its natural taxis to tumor⁸.

It's important to highlight our significances.

1. Switch apoptosis to pyroptosis in chemical therapy.
Numerous patients accept chemotherapy during their fight against cancers though there is a terrible drawback. Chemotherapy drugs can activate caspase-3-mediated pyroptosis in normal tissue while apoptosis in cancer cells, resulting in severe healthy tissue damage but inefficiency tumor cure⁹. But our designed circuit can trigger pyroptosis in cancer cells to solve this problem.

2. Pyroptosis make tumor expose to immune system.
The lysate of cell rupture during pyroptosis can destroy tumor microenvironment which is vital to tumor growth. Pyroptosis not only releases "find me" signals but also "eat me" signals¹⁰. Pyroptosis induces greater ATP release than apoptosis to attract more immune cells into tumor bed, which is one of our "find me" signals. Also, ATP can bind to purinergic P2RX7 receptors on dentritic cell (DC), activating the NLRP3/ASC/Caspase-1 inflammasome and secreting interleukin-1β (IL-1β), which is required for CD8⁺ T cells to release IFN-γ which lysis tumor cells¹¹. The "eat me" signal is the phosphatidylserine externalization to recruit macrophages to engulf the tumor cells.

3. Pyroptosis recombine with antibody-dependent cellular cytotoxicity (ADCC) will become more efficient.
Some monoclonal antibodies such as trastuzumab (TRAST), alemtuzumab, cetuximab and panitumumab have been taken on board for both solid tumors and hematologic malignancies treatments through ADCC¹². It's a special way to recruit nature kill cells (NK cells), macrophages, γδ T cells, and dendritic cells to against cancer. However, lower activity of NK cells hinder the development of this approach¹³. In our project, we give a new insight to solve this problem. IL-18 released from pyroptotic cells can stimulate natural killer cells proliferation and activation¹⁴. Meanwhile pyroptosis also up-regulates intercellular cell adhesion molecule-1 (ICAM-1 or CD54) which binds to alpha integrin on the tumor cell result in enhancing the ability of combination between NK cells and tumor cells¹⁵.

4. Safe utilization of the N-terminal of GSDMD.
Recent studies demonstrated that the N-terminal of GSDMD executes the function through bind to inositol phosphate (present in inner leaflet of cell membrane) in eukaryotic cell but cardiolipin (present in the inner and outer leaflets of cell membranes) in bacteria¹⁶. Thus, the N-terminal of GSDMD releasing from bacteria in extracellular is avirulent and attack both tumor cells and redundant bacteria.

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2. Bray, F. et al. Global cancer statistics 2018: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries. CA A J. Clin. 00, 1–31 (2018).

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4. Ding, J. et al. Pore-forming activity and structural autoinhibition of the gasdermin family. Nature 535, 111-116, doi:10.1038/nature18590 (2016).

5. Pyroptosis is involved in the pathogenesis of human hepatocellular carcinoma (2016).

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15. Kohrt, H., Rajasekaran, N., Chester, C., Yonezawa, A. & Zhao, X. Enhancement of antibody-dependent cell mediated cytotoxicity: a new era in cancer treatment. ImmunoTargets Ther. 91 (2015). doi:10.2147/ITT.S61292

16. Liu, X. et al. Inflammasome-activated gasdermin D causes pyroptosis by forming membrane pores. Nature 535, 153-158, doi:10.1038/nature18629 (2016).