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Combination treatment with decitabine and ionizing radiation enhances tumor cells susceptibility of T cells

View Article: PubMed Central - PubMed

ABSTRACT

Decitabine has been found to have anti-metabolic and anti-tumor activities in various tumor cells. Recently, the use of decitabine in combination with other conventional therapies reportedly resulted in improved anti-tumor activity against various tumors. Ionizing radiation (IR) is widely used as a cancer treatment. Decitabine and IR improve immunogenicity and susceptibility of tumor cells to immune cells by up-regulating the expression of various molecules such as major histocompatibility complex (MHC) class I; natural-killer group 2, member D (NKG2D) ligands; and co-stimulatory molecules. However, the effects of combining decitabine and IR therapies are largely unknown. Our results indicate that decitabine or IR treatment upregulates MHC class I, along with various co-stimulatory molecules in target tumor cells. Furthermore, decitabine and IR combination treatment further upregulates MHC class I, along with the co-stimulatory molecules, when compared to the effect of each treatment alone. Importantly, decitabine treatment further enhanced T cell-mediated cytotoxicity and release of IFN- γ against target tumor cells which is induced by IR. Interestingly, decitabine did not affect NKG2D ligand expression or NK cell-mediated cytotoxicity in target tumor cells. These observations suggest that decitabine may be used as a useful immunomodulator to sensitize tumor cells in combination with other tumor therapies.

No MeSH data available.


Related in: MedlinePlus

Expression of NKG2D ligands in tumor cells after treatment with decitabine, ionizing radiation (IR), or their combination.NKG2D ligand expression in A549 cells (a), HCT-116 cells (b), and HepG2 cells (c) was analyzed by flow cytometry using specific mAbs. Tumor cells were treated with 5 μM decitabine for 24 h then exposed to radiation doses of 8 Gy. Mean fluorescence intensity (MFI) ratio was calculated as MFI with specific mAb/MFI with isotype control mAb (a–c). In the figure, filled white represents the untreated control, filled light gray represents decitabine, filled dark gray represents IR and filled black represents decitabine and IR combination treatment (d). Results are expressed as the average MFI ± SD. Experiments were independently performed from five healthy donors. The assay was performed in triplicated each donor. Statistical significance was determined using a one-way ANOVA. #P < 0.05, ##P < 0.005, ###P < 0.0005 (#DAC 0 versus other groups). **P < 0.005 (*DAC 5 versus other groups). ****P < 0.005 (**IR 8 Gy versus DAC 5 + IR 8 Gy).
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f5: Expression of NKG2D ligands in tumor cells after treatment with decitabine, ionizing radiation (IR), or their combination.NKG2D ligand expression in A549 cells (a), HCT-116 cells (b), and HepG2 cells (c) was analyzed by flow cytometry using specific mAbs. Tumor cells were treated with 5 μM decitabine for 24 h then exposed to radiation doses of 8 Gy. Mean fluorescence intensity (MFI) ratio was calculated as MFI with specific mAb/MFI with isotype control mAb (a–c). In the figure, filled white represents the untreated control, filled light gray represents decitabine, filled dark gray represents IR and filled black represents decitabine and IR combination treatment (d). Results are expressed as the average MFI ± SD. Experiments were independently performed from five healthy donors. The assay was performed in triplicated each donor. Statistical significance was determined using a one-way ANOVA. #P < 0.05, ##P < 0.005, ###P < 0.0005 (#DAC 0 versus other groups). **P < 0.005 (*DAC 5 versus other groups). ****P < 0.005 (**IR 8 Gy versus DAC 5 + IR 8 Gy).

Mentions: To investigate whether decitabine and IR combination treatment up-regulates NKG2D ligand expression in tumor cells, A549, HCT-116, and HepG2 cells were treated with 5 μM decitabine for 24 h. Then, the tumor cells were exposed to radiation doses of 8 Gy. NKG2D ligand cell surface expression was quantified using mean fluorescent intensities (MFIs) (Fig. 5). Mean fluorescence intensity (MFI) ratio was calculated as MFI with specific mAb/MFI with isotype control mAb. NKG2D ligand expression was not significantly increased after treatment with decitabine or IR in A549 and HepG2 cells. Also, the combination treatment was negative or only low positive for the NKG2D ligand compared with either treatment alone. HCT-116 cells significantly increased the expression of MICB by treatment with decitabine or IR, but other NKG2D ligands (MICA, ULBP1, ULBP2, and ULBP3) expression did not altered significantly. Although, the combination treatment with decitabine and IR resulted in a significantly increased expression of MICA, MICB, and ULBP2 compared with control cells, it increased only ULBP2 compared with either treatment alone. Previous studies reported that decitabine significantly upregulates NKG2D ligand expression in several cancer cells121434; however, expression levels may differ in individual tumor cells. As such, the results of this study suggest that decitabine treatment does not effectively induce NKG2D ligand expression in A549, HCT-116, and HepG2 cells.


Combination treatment with decitabine and ionizing radiation enhances tumor cells susceptibility of T cells
Expression of NKG2D ligands in tumor cells after treatment with decitabine, ionizing radiation (IR), or their combination.NKG2D ligand expression in A549 cells (a), HCT-116 cells (b), and HepG2 cells (c) was analyzed by flow cytometry using specific mAbs. Tumor cells were treated with 5 μM decitabine for 24 h then exposed to radiation doses of 8 Gy. Mean fluorescence intensity (MFI) ratio was calculated as MFI with specific mAb/MFI with isotype control mAb (a–c). In the figure, filled white represents the untreated control, filled light gray represents decitabine, filled dark gray represents IR and filled black represents decitabine and IR combination treatment (d). Results are expressed as the average MFI ± SD. Experiments were independently performed from five healthy donors. The assay was performed in triplicated each donor. Statistical significance was determined using a one-way ANOVA. #P < 0.05, ##P < 0.005, ###P < 0.0005 (#DAC 0 versus other groups). **P < 0.005 (*DAC 5 versus other groups). ****P < 0.005 (**IR 8 Gy versus DAC 5 + IR 8 Gy).
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f5: Expression of NKG2D ligands in tumor cells after treatment with decitabine, ionizing radiation (IR), or their combination.NKG2D ligand expression in A549 cells (a), HCT-116 cells (b), and HepG2 cells (c) was analyzed by flow cytometry using specific mAbs. Tumor cells were treated with 5 μM decitabine for 24 h then exposed to radiation doses of 8 Gy. Mean fluorescence intensity (MFI) ratio was calculated as MFI with specific mAb/MFI with isotype control mAb (a–c). In the figure, filled white represents the untreated control, filled light gray represents decitabine, filled dark gray represents IR and filled black represents decitabine and IR combination treatment (d). Results are expressed as the average MFI ± SD. Experiments were independently performed from five healthy donors. The assay was performed in triplicated each donor. Statistical significance was determined using a one-way ANOVA. #P < 0.05, ##P < 0.005, ###P < 0.0005 (#DAC 0 versus other groups). **P < 0.005 (*DAC 5 versus other groups). ****P < 0.005 (**IR 8 Gy versus DAC 5 + IR 8 Gy).
Mentions: To investigate whether decitabine and IR combination treatment up-regulates NKG2D ligand expression in tumor cells, A549, HCT-116, and HepG2 cells were treated with 5 μM decitabine for 24 h. Then, the tumor cells were exposed to radiation doses of 8 Gy. NKG2D ligand cell surface expression was quantified using mean fluorescent intensities (MFIs) (Fig. 5). Mean fluorescence intensity (MFI) ratio was calculated as MFI with specific mAb/MFI with isotype control mAb. NKG2D ligand expression was not significantly increased after treatment with decitabine or IR in A549 and HepG2 cells. Also, the combination treatment was negative or only low positive for the NKG2D ligand compared with either treatment alone. HCT-116 cells significantly increased the expression of MICB by treatment with decitabine or IR, but other NKG2D ligands (MICA, ULBP1, ULBP2, and ULBP3) expression did not altered significantly. Although, the combination treatment with decitabine and IR resulted in a significantly increased expression of MICA, MICB, and ULBP2 compared with control cells, it increased only ULBP2 compared with either treatment alone. Previous studies reported that decitabine significantly upregulates NKG2D ligand expression in several cancer cells121434; however, expression levels may differ in individual tumor cells. As such, the results of this study suggest that decitabine treatment does not effectively induce NKG2D ligand expression in A549, HCT-116, and HepG2 cells.

View Article: PubMed Central - PubMed

ABSTRACT

Decitabine has been found to have anti-metabolic and anti-tumor activities in various tumor cells. Recently, the use of decitabine in combination with other conventional therapies reportedly resulted in improved anti-tumor activity against various tumors. Ionizing radiation (IR) is widely used as a cancer treatment. Decitabine and IR improve immunogenicity and susceptibility of tumor cells to immune cells by up-regulating the expression of various molecules such as major histocompatibility complex (MHC) class I; natural-killer group 2, member D (NKG2D) ligands; and co-stimulatory molecules. However, the effects of combining decitabine and IR therapies are largely unknown. Our results indicate that decitabine or IR treatment upregulates MHC class I, along with various co-stimulatory molecules in target tumor cells. Furthermore, decitabine and IR combination treatment further upregulates MHC class I, along with the co-stimulatory molecules, when compared to the effect of each treatment alone. Importantly, decitabine treatment further enhanced T cell-mediated cytotoxicity and release of IFN- &gamma; against target tumor cells which is induced by IR. Interestingly, decitabine did not affect NKG2D ligand expression or NK cell-mediated cytotoxicity in target tumor cells. These observations suggest that decitabine may be used as a useful immunomodulator to sensitize tumor cells in combination with other tumor therapies.

No MeSH data available.


Related in: MedlinePlus