The HLA class I antigen processing machinery (APM) plays a crucial role in the anticancer immune response. The aim of this study was to assess the clinical significance of APM components in esophageal cancer. A total of 11 esophageal cancer cell lines were evaluated by Western blot analysis for 13 HLA class I APM components. There was a different expression pattern among cancer cell lines for HLA class I heavy chain (HLA-HC), β2 microglobulin, Tapasin, TAP‑1, TAP-2, LMP-7 and LMP-10. Immunohistochemical staining utilizing a tissue microarray method for HLA class I APM expression showing different expression patterns among cell lines was performed for 95 surgical specimens from patients with esophageal cancer. Prognostic factors were the down-regulation of HLA-HC, and the up-regulation of β2 microglobulin and TAP-1 in the cancer tissues. Multivariate analysis using a Cox regression model indicated that the down-regulation of HLA-HC, and up-regulation of TAP-1 in cancer tissues are independent, unfavorable prognostic factors (hazard ratio, 2.361 and 2.297; P=0.0141 and 0.0145, respectively). Although there was no significant difference in survival for selected p-stage I and II patients (n=54) in all APM components, only down-regulation of HLA-HC was an unfavorable prognostic factor by a Cox regression model for selected p-stage III and IV patients (n=41). In conclusion, the current results suggest that the down-regulation of HLA-HC in tumors is especially associated with a poor prognosis among advanced esophageal cancer patients.

A phase I+II clinical trial of vaccination with MAGE-A4 protein complexed with cholesteryl pullulan melanoma antigen gene-A4 nanogel (CHP-MAGE-A4) is currently underway in patients with MAGE-A4-expressing cancer. In the present study, the primary phase I endpoint was to test the safety of the administration of 300 µg CHP-MAGE-A4 with and without OK-432. Another aim of the study was to clarify the details of the specific humoral immune response to vaccination. The 9 patients enrolled for phase I were vaccinated 6 times, once every 2 weeks: 3 patients with 100 µg and 3 patients with 300 µg CHP-MAGE-A4, and 3 patients with 300 µg CHP-MAGE-A4 plus 0.5 clinical units of OK-432. Toxicities were assessed using Common Terminology Criteria for Adverse Events v3.0. Clinical response was evaluated by modified Response Evaluation Criteria in Solid Tumours. Immunological monitoring of anti-MAGE-A4-specific antibodies was performed by ELISA of pre- and post-vaccination patient sera. The 6 vaccinations produced no severe adverse events. Stable disease was assessed in 4/9 patients. Anti-MAGE-A4 total immunoglobulin (Ig)G titers increased in 7/9 patients. Efficacious anti-MAGE-A4 IgG1, 2 and 3 antibody responses were observed in 7/9 patients. Among them, positive conversions to T helper 2 (Th2)-type antibody responses (IgG4 and IgE) were observed after frequent vaccination in 4/7 patients. The Th2 conversion was possibly associated with undesirable clinical observations, including progressive disease and the appearance of a new relapse lesion. The present study suggested that frequent vaccinations activated a Th2-dominant status in the cancer patients. The identification of a time-dependent IgG subclass and IgE antibody production during vaccination protocols may be a useful surrogate marker indicating a potentially undesirable change of the immunological environment for an effective antitumor immune response in cancer patients.