Heat shock protein DNAJB8 is a novel target for immunotherapy of colon cancer-initiating cells.
Bottom Line: In the present study, we found that a heat shock protein (HSP) 40 family member, DnaJ (Hsp40) homolog, subfamily B, member 8 (DNAJB8), is preferentially expressed in CSC/CIC derived from colorectal cancer (CRC) cells rather than in non-CSC/CIC.Overexpression of DNAJB8 enhanced the expression of stem cell markers and tumorigenicity, indicating that DNAJB8 has a role in CRC CSC/CIC.A CTL clone specific for DNAJB8 peptide showed higher killing activity to CRC CSC/CIC compared with non-CSC/CIC, and CTL adoptive transfer into CRC CSC/CIC showed an antitumor effect in vivo.
Affiliation: Department of Pathology, Sapporo Medical University School of Medicine, Sapporo, Japan.Show MeSH
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Mentions: The PBMC of two healthy volunteer donors (A and B) were stimulated using a mixture of DNAJB8_22(9), DNAJB8_99(9) and DNAJB8_143(9) and then the reactivity for each peptide was evaluated using a IFN-γ ELISpot assay and 51Cr release assay. Interferon-γ secretion was observed for DNAJB8_22(8)-pulsed and DNAJB8_143(9)-pulsed target cells from both donors using a IFN-γ ELISpot assay (Fig. 4a), whereas cytotoxic activity was detectable for only DNAJB8_143(9)-pulsed target cells using a 51Cr release assay (Fig. 4b). Therefore, DNAJB8_143(9) peptide is a candidate for DNAJB8-targeting immunotherapy. We generated four CTL clones specific for DNAJB8_143(9) from donor A (CTL clone #21, 67 and 84) and one clone from donor B (CTL clone #70) and performed further analysis using CTL clone #84. The DNAJB8_143(9)-specific CTL clone showed cytotoxic activity for T2-A24 cells pulsed with DNAJB8_143(9) peptide but not for T2-A24 cells without the peptide or for K562 cells (Fig. 4c). To verify whether this CTL clone can recognize endogenously presented DNAJB8_143(9) peptide of DNAJB8-positive CRC CSC/CIC, we performed a 51Cr release assay using SP cells derived from HT29 cells. The DNAJB8_143(9)-specific CTL clone showed greater cytotoxic activity for HLA-A*2402+ HT29-SP cells than for HLA-A*2402+ HT29-MP cells or HLA-A*2402-DNAJB8- K562 cells (Fig. 4d). These results indicate that DNAJB8_143(9) peptide is an immunogenic epitope and that the endogenously processed peptide is presented on the surface of SP cells.
Affiliation: Department of Pathology, Sapporo Medical University School of Medicine, Sapporo, Japan.