BACKGROUND Nucleus accumbens-1(NAC-1)is highly expressed in a variety of tumors,including colon cancer,and is closely associated with tumor recurrence,metastasis,and invasion.AIM To determine whether and how NAC-1 aff...BACKGROUND Nucleus accumbens-1(NAC-1)is highly expressed in a variety of tumors,including colon cancer,and is closely associated with tumor recurrence,metastasis,and invasion.AIM To determine whether and how NAC-1 affects antitumor immunity in colon cancer.METHODS NAC-1-siRNA was transfected into RKO colon cancer cells to knock down NAC expression;tumor cells with or without knockdown of NAC-1 were treated with CD8+T cells to test their cytocidal effect.The level of the immune checkpoint programmed death receptor-1 ligand(PD-L1)in colon cancer cells with or without knockdown of NAC-1 was analyzed using Quantitative real-time polymerase chain reaction and Western blotting.A double luciferase reporter assay was used to examine the effects of NAC-1 on the transcription of PD-L1.Mice bearing MC-38-OVA colon cancer cells expressing NAC-shRNA or controlshRNA were treated with OT-I mouse CD8+T cells to determine the tumor response to immunotherapy.Immune cells in the tumor tissues were analyzed using flow cytometry.NAC-1,PD-L1 and CD8+T cells in colon cancer specimens from patients were examined using immunohistochemistry staining.RESULTS Knockdown of NAC-1 expression in colon cancer cells significantly enhanced the cytocidal effect of CD8+T cells in cell culture experiments.The sensitizing effect of NAC-1 knockdown on the antitumor action of cytotoxic CD8+T cells was recapitulated in a colon cancer xenograft animal model.Furthermore,knockdown of NAC-1 in colon cancer cells decreased the expression of PD-L1 at both the mRNA and protein levels,and this effect could be rescued by transfection of an RNAi-resistant NAC-1 expression plasmid.In a reporter gene assay,transient expression of NAC-1 in colon cancer cells increased the promoter activity of PD-L1,indicating that NAC-1 regulates PD-L1 expression at the transcriptional level.In addition,depletion of tumoral NAC-1 increased the number of CD8+T cells but decreased the number of suppressive myeloid-derived suppressor cells and regulatory T cells.CONCLUSION Tumor expression of NAC-1 is a negative determinant of immunotherapy.展开更多
基金the Changsha Municipal Natural Science Foundation,No.kq2014258.
文摘BACKGROUND Nucleus accumbens-1(NAC-1)is highly expressed in a variety of tumors,including colon cancer,and is closely associated with tumor recurrence,metastasis,and invasion.AIM To determine whether and how NAC-1 affects antitumor immunity in colon cancer.METHODS NAC-1-siRNA was transfected into RKO colon cancer cells to knock down NAC expression;tumor cells with or without knockdown of NAC-1 were treated with CD8+T cells to test their cytocidal effect.The level of the immune checkpoint programmed death receptor-1 ligand(PD-L1)in colon cancer cells with or without knockdown of NAC-1 was analyzed using Quantitative real-time polymerase chain reaction and Western blotting.A double luciferase reporter assay was used to examine the effects of NAC-1 on the transcription of PD-L1.Mice bearing MC-38-OVA colon cancer cells expressing NAC-shRNA or controlshRNA were treated with OT-I mouse CD8+T cells to determine the tumor response to immunotherapy.Immune cells in the tumor tissues were analyzed using flow cytometry.NAC-1,PD-L1 and CD8+T cells in colon cancer specimens from patients were examined using immunohistochemistry staining.RESULTS Knockdown of NAC-1 expression in colon cancer cells significantly enhanced the cytocidal effect of CD8+T cells in cell culture experiments.The sensitizing effect of NAC-1 knockdown on the antitumor action of cytotoxic CD8+T cells was recapitulated in a colon cancer xenograft animal model.Furthermore,knockdown of NAC-1 in colon cancer cells decreased the expression of PD-L1 at both the mRNA and protein levels,and this effect could be rescued by transfection of an RNAi-resistant NAC-1 expression plasmid.In a reporter gene assay,transient expression of NAC-1 in colon cancer cells increased the promoter activity of PD-L1,indicating that NAC-1 regulates PD-L1 expression at the transcriptional level.In addition,depletion of tumoral NAC-1 increased the number of CD8+T cells but decreased the number of suppressive myeloid-derived suppressor cells and regulatory T cells.CONCLUSION Tumor expression of NAC-1 is a negative determinant of immunotherapy.
