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[TSST-1 regulated synergistically by 5HRE and CEAp activates lymphocytes to kill CEA-positive tumor cells
Yong Tian1, Xue-jun Sun, Wei Wang
1Department of General Surgery, First Affiliated Hospital of Medical College of Xi'an Jiaotong University, Xi'an 710061, China.
Aim:
To evaluate the inhibitory effect of lymphocytes activated by the superantigen of toxic shock syndrome toxin-1 (TSST-1), which is regulated synergistically by 5 copies of hypoxia-responsive element (5HRE) and promoter of carcino-embryonic antigen (CEAp), against the carcino-embryonic antigen (CEA)-positive human colon carcinoma cell line LoVo under hypoxia condition in vitro.
Methods:
The eukaryotic expressive vector was constructed with the transmembrane superantigen gene of 5HRE-CEAp-regulated TSST-1-linker-CD80TM, and was transfected into CEA-positive human colon carcinoma cell line LoVo and CEA-negative human cervical carcinoma cell line HeLa by Lipofectamine 2000. Stably transfected cell lines were selected by G418. RT-PCR was employed to examine the expression of TC mRNA. Peripheral blood lymphocytes(PBL) of healthy people were extracted and then activated by the lysates of tumor cells stably transfected with TC. Concurrently, PBL were cultured together with stably transfected tumor cells in order to kill these cells. Then the proliferative effect of TSST-1 on PBL, and the killing effect of PBL against the stably transfected tumor cells were detected by MTT.
Results:
Monoclonal LoVo and HeLa cells stably transfected with TC were successfully obtained. Expression of TC mRNA in monoclonal LoVo cells under hypoxia condition was significantly higher than those under normoxia condition as confirmed by RT-PCR. Monoclonal HeLa cells did not express TC under either hypoxia condition or normoxia condition. As is shown by MTT assay, TSST-1 expressed by the monoclonal LoVo cells could effectively activate PBL to proliferate under hypoxia condition, resulting in dose-dependent inhibition on the proliferation of LoVo cells that expressed TSST (P<0.05). But HeLa cells and wild LoVo cells could not activate PBL to proliferate. PBL could not inhibit proliferation of HeLa cells and wild LoVo cells, either.
Conclusion:
The superantigen of TSST-1 regulated dually by 5HRE and CEAp could activate human PBL to kill CEA-positive tumor cells specifically under hypoxia condition.
Insights
This study shows that toxic shock syndrome toxin-1 (TSST-1) can activate lymphocytes to specifically kill CEA-positive colon cancer cells under hypoxia. This targeted approach offers a potential new strategy for cancer therapy.
Area of Science:
- Immunology
- Oncology
- Molecular Biology
Context:
- Hypoxia is a common feature in solid tumors, influencing tumor microenvironment and treatment resistance.
- Carcinoembryonic antigen (CEA) is a tumor-associated antigen overexpressed in various carcinomas, making it a target for cancer therapy.
- Superantigens, like TSST-1, can potently activate T cells, offering a platform for immune-based cancer treatments.
Purpose:
- To investigate the efficacy of lymphocytes activated by TSST-1, under the synergistic regulation of 5HRE and CEAp, against CEA-positive colon carcinoma cells (LoVo) in a hypoxic environment.
- To assess the specific activation of peripheral blood lymphocytes (PBL) and their subsequent cytotoxic effect on transfected tumor cells.
- To evaluate the role of hypoxia in regulating the expression of the therapeutic gene and the overall anti-tumor immune response.
Summary:
- Engineered eukaryotic expression vectors containing the 5HRE-CEAp-regulated TSST-1 gene were transfected into CEA-positive LoVo and CEA-negative HeLa cells.
- Hypoxia significantly upregulated TC mRNA expression in LoVo cells, while HeLa cells showed no expression under either normoxic or hypoxic conditions.
- Activated PBL demonstrated dose-dependent inhibition of proliferation in TSST-expressing LoVo cells under hypoxia, confirming specific tumor cell killing, whereas wild-type cells and HeLa cells were unaffected.
Impact:
- This research demonstrates a novel hypoxia-inducible gene therapy strategy for targeting CEA-positive tumors.
- The findings highlight the potential of TSST-1-activated PBL as a specific anti-cancer immunotherapy agent in hypoxic tumor settings.
- This approach could lead to the development of more effective and targeted treatments for colon cancer and potentially other CEA-expressing malignancies.
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