Background: ABCB5ϩ MMIC are a population of chemoresistant cancer stem cell-like cells responsible for melanoma initiation, growth, and progression. Results: HAGE promotes ABCB5ϩ MMIC-dependent tumorigenesis by enhancing RAS protein expression. Conclusion: ABCB5ϩ MMIC require the presence of HAGE for their tumorigenic activity. Significance: HAGE is expressed only by tumor cells. Hence, targeting HAGE helicase may have broad therapeutic applications.

Treatment options for patients with advanced prostate cancer remain limited and rarely curative. Prostatic acid phosphatase (PAP) is a prostate-specific protein overexpressed in 95% of prostate tumours. An FDA-approved vaccine for the treatment of advanced prostate disease, PROVENGE R (sipuleucel-T), has been shown to prolong survival, however the precise sequence of the PAP protein responsible for the outcome is unknown. As the PAP antigen is one of the very few prostate-specific antigens for which there is a rodent equivalent with high homology, preclinical studies using PAP have the potential to be directly relevant to clinical setting. Here, we show three PAP epitopes naturally processed and presented in the context of HHDII/DR1 (114-128, 299-313, and 230-244). The PAP-114-128 epitope elicits CD4 + and CD8 + T-cell-specific responses in C57BL/6 mice.Furthermore, when immunised in a DNA vector format (ImmunoBody R ), PAP-114-128 prevents and reduces the growth of transgenic adenocarcinoma of mouse prostate-C1 prostate cancer cell-derived tumours in both prophylactic and therapeutic settings. This anti-tumour effect is associated with infiltration of CD8 + tumour-infiltrating lymphocytes and the generation of high avidity T cells secreting elevated levels of IFN-γ. PAP-114-128 therefore appears to be a highly relevant peptide on which to base vaccines for the treatment of prostate cancer. Keywords:Immunotherapy r Prostate acid phosphatase r Prostate cancer r Tumour-infiltrating lymphocyte r Vaccine Additional supporting information may be found in the online version of this article at the publisher's web-site IntroductionProstate cancer is the most common form of male cancer in developed countries and cases are rising among men under 50. EveryCorrespondence: Dr. Stephanie E. B. McArdle e-mail: stephanie.mcardle@ntu.ac.uk year, more than 32 000 British men are diagnosed and 10 000 die from the disease [1,2]. At present there is no standard treatment available for patients with biochemical recurrence in the absence of radiographically visible metastases [3]. A long-held dream of tumour immunologists is to harness the specificity and sensitivity of the immune response and induce specific protective anti-tumour immunity. Unfortunately, for most cancers, the specific antigenic determinants on which vaccination strategies can C 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.eji-journal.eu Eur. J. Immunol. 2014. 44: 994-1004 Cellular immune response 995 be based are weakly immunogenic self-antigens that are comparatively poor at inducing robust, protective anti-tumour responses. Developing cancer vaccines that can overcome immune evasion and the tolerogenic capacity of self-antigens and induce protective immune responses is therefore essential for the development of new immunotherapies for aggressive disease. Several tumour-associated antigens have been reported to be expressed by prostate cancer cells. These include prostate-specific membrane antigen, prostate-specific antigen and prostate acidic phosphatase (P...

Recent years have seen the unprecedented surge of interest in the role of CD4+ T cells and the role they play in the development of the immune response. In this symposium review, we examine the evidence for this and discuss their functions, particularly in respect to the cancer immunology, including CD4+CD25+ cells (Treg).

There remains a need to identify novel epitopes of potential tumour target antigens for use in immunotherapy of cancer. Here, several melanoma tissues and cell lines but not normal tissues were found to overexpress the cancer-testis antigen HAGE at the mRNA and protein level. We identified a HAGE-derived 15-mer peptide containing a shorter predicted MHC class I-binding sequence within a class II-binding sequence. However, only the longer peptide was found to be both endogenously processed and immunogenic for T cells in transgenic mice in vivo, as well as for human T cells in vitro. A different class I-binding peptide, not contained within a longer class II sequence, was subsequently found to be both immunogenic and endogenously processed in transgenic mice, as was a second class II epitope. These novel HAGE-derived epitopes may contribute to the range of immunotherapeutic targets for use in cancer vaccination programs.

The tumour suppressor PML (promyelocytic leukaemia protein) regulates several cellular pathways involving cell growth, apoptosis, differentiation and senescence. PML also has an important role in the regulation of stem cell proliferation and differentiation. Here, we show the involvement of the helicase HAGE in the transcriptional repression of PML expression in ABCB5+ malignant melanoma-initiating cells (ABCB5+ MMICs), a population of cancer stem cells which are responsible for melanoma growth, progression and resistance to drug-based therapy. HAGE prevents PML gene expression by inhibiting the activation of the JAK–STAT (janus kinase–signal transducers and activators of transcription) pathway in a mechanism which implicates the suppressor of cytokine signalling 1 (SOCS1). Knockdown of HAGE led to a significant decrease in SOCS1 protein expression, activation of the JAK–STAT signalling cascade and a consequent increase of PML expression. To confirm that the reduction in SOCS1 expression was dependent on the HAGE helicase activity, we showed that SOCS1, effectively silenced by small interfering RNA, could be rescued by re-introduction of HAGE into cells lacking HAGE. Furthermore, we provide a mechanism by which HAGE promotes SOCS1 mRNA unwinding and protein expression in vitro. Finally, using a stem cell proliferation assay and tumour xenotransplantation assay in non-obese diabetic/severe combined immunodeficiency mice, we show that HAGE promotes MMICs-dependent tumour initiation and tumour growth by preventing the anti-proliferative effects of interferon-α (IFNα). Our results suggest that the helicase HAGE has a key role in the resistance of ABCB5+ MMICs to IFNα treatment and that cancer therapies targeting HAGE may have broad implications for the treatment of malignant melanoma.