Retraction. The Fas/Fas ligand pathway and Bcl-2 regulate T cell responses to model self and foreign antigens

The abscopal effect of anti-CD95 and radiotherapy in melanoma

BACKGROUND

Radiotherapy (RT) is frequently adopted to control cancer cell proliferation, which is achieved by altering the tumor microenvironment (TME) and immunogenicity. Apoptosis of cancer cells is the major effect of radiation on tumor tissues. Fas/APO-1(CD95) receptors on the cell membrane are death receptors that can be activated by diverse factors, including radiation and integration with CD95L on CD8⁺ T cells. The abscopal effect is defined as tumor regression out of the local RT field, and it is produced through anti-tumor immunity. The immune response against the radiated tumor is characterized by the cross-presentation between antigen-presenting cells (APCs), which includes cytotoxic T cells (CTLs) and dendritic cells (DCs).

METHODS

The effect of activation and radiation of CD95 receptors on melanoma cell lines was examined in vivo and in vitro. In vivo, bilateral lower limbs were given a subcutaneous injection of a dual-tumor. Tumors in the right limb were radiated with a single dose of 10 Gy (primary tumor), while tumors in the left limb (secondary tumor) were spared.

RESULTS

The anti-CD95 treatment plus radiation (combination treatment) reduced growth rates of both primary and secondary tumors relative to the control or radiation groups. In addition, higher degrees of infiltrating CTLs and DCs were detected in the combination treatment compared to the other groups, but the immune response responsible for secondary tumor rejection was not proven to be tumor specific. In vitro, combination treatment combined with radiation resulted in further apoptosis of melanoma cells relative to controls or cells treated with radiation.

CONCLUSIONS

Targeting CD95 on cancer cells will induce tumor control and the abscopal effect.

[Total glucosides of paeony inhibits proliferation and promotes activation- induced cell death of mouse T cells in vitro]

OBJECTIVE

To investigate the effects of total glucosides of paeony (TGP) on the proliferation and activation-induced cell death of mouse T cells and the mechanism underlying the immunosuppressive effects of TGP.

METHODS

Purified total T cells isolated from the spleen of C57BL/6 mice were treated with TGP at 0, 50, 100, or 200 μg/mL and stimulated by anti-CD3/ CD28. Flow cytometry was performed to detect the cell death and the proliferation of CFSE-labeled T cells. The expression of Fas/FasL mRNA was detected using RT-PCR, and flow cytometry was used to analyze the expression of Fas/FasL proteins on activated T cells. Western blotting was used to detect the expression of Bcl-2 in the cells.

RESULTS

TGP treatment for 48 h significantly reduced the total number and percentage of viable T cells and dose-dependently lowered the percentage of divided T cells. TGP treatment obviously up-regulated the cellular expression of Fas mRNA, enhanced Fas expression on the surface of the T cells, and decreased the expression level of Bcl-2 protein in the cells.

CONCLUSIONS

TGP significantly inhibits proliferation and promotes activation-induced cell death of mouse T cell by increasing the expression of Fas and downregulating the expression of Bcl-2.