1 2 5 4 VOLUME 18 | NUMBER 8 | AUGUST 2012 nAture medicine Therapeutic cancer vaccines hold the promise of combining meaningful efficacy (prolongation of survival) with very good safety and tolerability, as has been shown in several recent randomized trials 1-3 . However, development of cancer vaccines remains a major challenge, with little knowledge of (i) the optimal tumor antigens to target, (ii) suitable agents to counteract regulatory mechanisms opposing successful immunotherapy and (iii) surrogate and predictive biomarkers that can improve our understanding of these regulatory mechanisms and predict a patient's response to therapy. The first major issue addressed in this work is whether relevant HLArestricted peptides for immunotherapeutic intervention in patients with RCC can be identified and clinically validated. We defined the relevance of the antigens as their natural presence on the tumor in the majority of RCC samples, their immunogenicity (induction of T cell responses in clinical studies) and the association of the vaccine-induced T cell responses with clinical benefit. For the identification, selection and preclinical immunological validation of such antigens, we used the antigen discovery platform XPRESIDENT 4,5 to create a multipeptide vaccine designated IMA901 for immunotherapy of RCC. We tested IMA901 in HLA-A*02 + subjects with advanced RCC in two clinical trials, a phase 1 (n = 28) and a randomized phase 2 (n = 68) trial, both of which assessed the association of T cell responses to IMA901 with clinical benefit.

Prediction of clinical outcome in cancer is usually achieved by histopathological evaluation of tissue samples obtained during surgical resection of the primary tumor. Traditional tumor staging (AJCC/UICC-TNM classification) summarizes data on tumor burden (T), presence of cancer cells in draining and regional lymph nodes (N) and evidence for metastases (M). However, it is now recognized that clinical outcome can significantly vary among patients within the same stage. The current classification provides limited prognostic information, and does not predict response to therapy. Recent literature has alluded to the importance of the host immune system in controlling tumor progression. Thus, evidence supports the notion to include immunological biomarkers, implemented as a tool for the prediction of prognosis and response to therapy. Accumulating data, collected from large cohorts of human cancers, has demonstrated the impact of immune-classification, which has a prognostic value that may add to the significance of the AJCC/UICC TNM-classification. It is therefore imperative to begin to incorporate the ‘Immunoscore’ into traditional classification, thus providing an essential prognostic and potentially predictive tool. Introduction of this parameter as a biomarker to classify cancers, as part of routine diagnostic and prognostic assessment of tumors, will facilitate clinical decision-making including rational stratification of patient treatment. Equally, the inherent complexity of quantitative immunohistochemistry, in conjunction with protocol variation across laboratories, analysis of different immune cell types, inconsistent region selection criteria, and variable ways to quantify immune infiltration, all underline the urgent requirement to reach assay harmonization. In an effort to promote the Immunoscore in routine clinical settings, an international task force was initiated. This review represents a follow-up of the announcement of this initiative, and of the J Transl Med. editorial from January 2012. Immunophenotyping of tumors may provide crucial novel prognostic information. The results of this international validation may result in the implementation of the Immunoscore as a new component for the classification of cancer, designated TNM-I (TNM-Immune).

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The heat shock protein Gp96 has been shown to induce specific immune responses. On one hand, this phenomenon is based on the specific interaction with CD91 that mediates endocytosis and results in major histocompatibility complex class I-restricted representation of the Gp96-associated peptides. On the other hand, Gp96 induces activation of professional antigen-presenting cells, resulting in the production of pro-inflammatory cytokines and up-regulation of costimulatory molecules by unknown mechanisms. In this study, we have analyzed the consequences of Gp96 interaction with cells expressing different Toll-like receptors (TLRs) and with bone marrow-derived dendritic cells from mice lacking functional TLR2 and/or TLR4 molecules. We find that the Gp96-TLR2/4 interaction results in activation of nuclear factor B-driven reporter genes and mitogen-and stress-activated protein kinases and induces IB␣ degradation. Bone marrow-derived dendritic cells of C3H/HeJ and more pronounced C3H/HeJ/ TLR2 ؊/؊ mice fail to respond to Gp96. Interestingly, activation of bone marrow-derived dendritic cells depends on endocytosis of Gp96 molecules. Our results provide, for the first time, the molecular basis for understanding the Gp96-mediated activation of antigen-presenting cells by describing the simultaneous stimulation of the innate and adaptive immune system. This feature explains the remarkable ability of Gp96 to induce specific immune responses against tumors and pathogens.

IntroductionMetastatic renal cell cancer (RCC) has a very poor prognosis with a median survival of only 6 to 12 months from the time of diagnosis. 1,2 Historically, there were no established effective treatment approaches for metastatic RCC because of its resistance to radiation and chemotherapy. 3 Until recently, cytokine-based immunotherapy using interferon-␣ (IFN-␣) and/or interleukin-2 (IL-2) was the only effective treatment resulting in response rates of 10% to 20%. 4 The understanding of RCC pathogenesis and identification of molecular mechanisms responsible for the malignant transformation and metastatic spread led to the development of drugs that target cancer-specific pathways, such as the PI3K/AKT and Ras/Raf/MAPK pathways. 5 RCC is often associated with up-regulated Raf1, EGFR, and VEGFR activity. 5,6 Furthermore, in a high proportion of RCC, mutational aberrations of the von Hippel-Lindau (VHL) gene were identified. The loss-of-function of this tumor suppressor gene results in an accumulation of hypoxia inducible factor (HIF)-␣ subunits and stimulation of angiogenesis via VEGF-and PDGF-receptors.Consequently, 2 novel tyrosine kinase inhibitors, sorafenib (Bayer HealthCare, Leverkusen, Germany) 5 and sunitinib (Pfizer, New York, NY), were introduced in the treatment of RCC patients.Sorafenib is a multikinase inhibitor initially developed to inhibit the Raf1-kinase pathway. 2 However, besides the RAF/MEK/ERK pathway, sorafenib targets receptor tyrosine kinases (RTKs), such as VEGFR-2 and -3, PDGFR-␤, Flt-3, and c-KIT. 2,7 In several clinical and preclinical trials, sorafenib was revealed to be a promising anticancer therapeutic, which negatively regulates tumor growth, cell proliferation, and angiogenesis 8,9 and additionally induces apoptosis in tumor cells. 10 In December 2005, sorafenib was approved by the FDA for treatment of patients with advanced/ metastatic RCC. In a randomized trial, sorafenib doubled the median duration of progression-free survival up to 24 weeks in patients refractory to or relapsed during cytokine treatment. 2,11,12 Sunitinib inhibits multiple split kinase domain RTKs, including VEGFR-1 and -2, PDGFR-␣ and -␤, c- 7,13 In 2 phase 2 studies, application of sunitinib resulted in response rates up to 40% and in a randomized phase 3 trial it showed an improved response rate and progression-free survival in comparison to 14,15 However, until now the effects of sorafenib and sunitinib on development and function of normal nonmalignant hematopoetic cells have not been evaluated in detail. It is known that PBLs isolated from patients receiving clinically relevant doses of sorafenib show inhibition of ERK phosphorylation on ex vivo PMA stimulation. 16 We therefore analyzed the immunomodulatory functions of these compounds using T cells and monocyte-derived dendritic cells (MDDCs), which were activated with ligands for TLR3 or 4. We found that sorafenib, but not sunitinib, has a detrimental effect on DC phenotype and inhibits cytokine secretion, migration ability, and T-cell stimulator...

Heat shock proteins (HSPs) like glycoprotein (gp)96 (glucose-regulated protein 94 [grp94]) are able to induce specific cytotoxic T lymphocyte (CTL) responses against cells from which they originate. Here, we demonstrate that for CTL activation by gp96-chaperoned peptides, specific receptor-mediated uptake of gp96 by antigen-presenting cells (APCs) is required. Moreover, we show that in both humans and mice, only professional APCs like dendritic cells (DCs), macrophages, and B cells, but not T cells, are able to bind gp96. The binding is saturable and can be inhibited using unlabeled gp96 molecules. Receptor binding by APCs leads to a rapid internalization of gp96, which colocalizes with endocytosed major histocompatibility complex (MHC) class I and class II molecules in endosomal compartments. Incubation of gp96 molecules isolated from cells expressing an adenovirus type 5 E1B epitope with the DC line D1 results in the activation of E1B-specific CTLs. This CTL activation can be specifically inhibited by the addition of irrelevant gp96 molecules not associated with E1B peptides. Our results demonstrate that only receptor-mediated endocytosis of gp96 molecules leads to MHC class I–restricted re-presentation of gp96-associated peptides and CTL activation; non–receptor-mediated, nonspecific endocytosis is not able to do so. Thus, we provide evidence on the mechanisms by which gp96 is participating in the cross-presentation of antigens from cellular origin.

Human cytomegalovirus (HCMV) has evolved a multitude of molecular mechanisms to evade the antiviral immune defense of the host. Recently, using soluble recombinant molecules, the HCMV UL16 glycoprotein was shown to interact with some ligands of the activating immunoreceptor NKG2D and, therefore, may also function as a viral immunomodulator. However, the role of UL16 during the course of HCMV infection remained unclear. Here, we demonstrate that HCMV infection of fibroblasts induces expression of all known NKG2D ligands (NKG2DL). However, solely MICA and ULBP3 reach the cellular surface to engage NKG2D, whereas MICB, ULBP1 and ULBP2 are selectively retained in the endoplasmic reticulum by UL16. UL16-mediated reduction of NKG2DL cell surface density diminished NK cytotoxicity. Thus, UL16 functions by capturing activating ligands for cytotoxic lymphocytes that are synthesized in response to HCMV infection.

Peptides presented at the cell surface reflect the protein content of the cell; those on HLA class I molecules comprise the critical peptidome elements interacting with CD8 T lymphocytes. We hypothesize that peptidomes from ex vivo tumour samples encompass immunogenic tumour antigens. Here, we uncover >6000 HLA-bound peptides from HLA-A*02(+) glioblastoma, of which over 3000 were restricted by HLA-A*02. We prioritized in-depth investigation of 10 glioblastoma-associated antigens based on high expression in tumours, very low or absent expression in healthy tissues, implication in gliomagenesis and immunogenicity. Patients with glioblastoma showed no T cell tolerance to these peptides. Moreover, we demonstrated specific lysis of tumour cells by patients' CD8(+) T cells in vitro. In vivo, glioblastoma-specific CD8(+) T cells were present at the tumour site. Overall, our data show the physiological relevance of the peptidome approach and provide a critical advance for designing a rational glioblastoma immunotherapy. The peptides identified in our study are currently being tested as a multipeptide vaccine (IMA950) in patients with glioblastoma.