Lessons from randomized phase III studies with active cancer immunotherapies--outcomes from the 2006 meeting of the Cancer Vaccine Consortium (CVC)

Biomarkers in T cell therapy clinical trials

T cell therapy represents an emerging and promising modality for the treatment of both infectious disease and cancer. Data from recent clinical trials have highlighted the potential for this therapeutic modality to effect potent anti-tumor activity. Biomarkers, operationally defined as biological parameters measured from patients that provide information about treatment impact, play a central role in the development of novel therapeutic agents. In the absence of information about primary clinical endpoints, biomarkers can provide critical insights that allow investigators to guide the clinical development of the candidate product. In the context of cell therapy trials, the definition of biomarkers can be extended to include a description of parameters of the cell product that are important for product bioactivity.

This review will focus on biomarker studies as they relate to T cell therapy trials, and more specifically: i. An overview and description of categories and classes of biomarkers that are specifically relevant to T cell therapy trials, and ii. Insights into future directions and challenges for the appropriate development of biomarkers to evaluate both product bioactivity and treatment efficacy of T cell therapy trials.

Natural and Induced Humoral Responses to MUC1

MUC1 is a membrane-tethered mucin expressed on the ductal cell surface of glandular epithelial cells. Loss of polarization, overexpression and aberrant glycosylation of MUC1 in mucosal inflammation and in adenocarcinomas induces humoral immune responses to the mucin. MUC1 IgG responses have been associated with a benefit in survival in patients with breast, lung, pancreatic, ovarian and gastric carcinomas. Antibodies bound to the mucin may curb tumor progression by restoring cell-cell interactions altered by tumor-associated MUC1, thus preventing metastatic dissemination, as well as counteracting the immune suppression exerted by the molecule. Furthermore, anti-MUC1 antibodies are capable of effecting tumor cell killing by antibody-dependent cell-mediated cytotoxicity. Although cytotoxic T cells are indispensable to achieve anti-tumor responses in advanced disease, abs to tumor-associated antigens are ideally suited to address minimal residual disease and may be sufficient to exert adequate immune surveillance in an adjuvant setting, destroying tumor cells as they arise or maintaining occult disease in an equilibrium state. Initial evaluation of MUC1 peptide/glycopeptide mono and polyvalent vaccines has shown them to be immunogenic and safe; anti-tumor responses are scarce. Progress in carbohydrate synthesis has yielded a number of sophisticated substrates that include MUC1 glycopeptide epitopes that are at present in preclinical testing. Adjuvant vaccination with MUC1 glycopeptide polyvalent vaccines that induce strong humoral responses may prevent recurrence of disease in patients with early stage carcinomas. Furthermore, prophylactic immunotherapy targeting MUC1 may be a strategy to strengthen immune surveillance and prevent disease in subjects at hereditary high risk of breast, ovarian and colon cancer.

Role of tumor vascular architecture in drug delivery

Tumor targeted drug delivery has the potential to improve cancer care by reducing non-target toxicities and increasing the efficacy of a drug. Tumor targeted delivery of a drug from the systemic circulation, however, requires a thorough understanding of tumor pathophysiology. A growing or receding (under the impact of therapy) tumor represents a dynamic environment with changes in its angiogenic status, cell mass, and extracellular matrix composition. An appreciation of the salient characteristics of tumor vascular architecture and the unique biochemical markers that may be used for targeting drug therapy is important to overcome barriers to tumor drug therapy and to facilitate targeted drug delivery. This review discusses the unique aspects of tumor vascular architecture that need to be overcome or exploited for tumor targeted drug delivery.

Clinical trial design for testing the stem cell model for the prevention and treatment of cancer

The cancer stem cell model introduces new strategies for the prevention and treatment of cancers. In cancers that appear to follow the stem cell model, pathways such as Wnt, Notch and Hedgehog may be targeted with natural compounds such as curcumin or drugs to reduce the risk of initiation of new tumors. Disease progression of established tumors could also potentially be inhibited by targeting the tumorigenic stem cells alone, rather than aiming to reduce overall tumor size. These new approaches mandate a change in the design of clinical trials and biomarkers chosen for efficacy assessment for preventative, neoadjuvant, adjuvant, and palliative treatments. Cancer treatments could be evaluated by assessing stem cell markers before and after treatment. Targeted stem cell specific treatment of cancers may not result in “complete” or “partial” responses radiologically, as stem cell targeting may not reduce the tumor bulk, but eliminate further tumorigenic potential. These changes are discussed using breast, pancreatic, and lung cancer as examples.

Control of advanced cancer: the road to chronicity

Despite the recent trend toward a slight decrease in age-adjusted cancer mortality in some countries, crude mortality rates will continue to increase, driven by the demographic shift towards an aged population. Small molecules (small molecules and biologics) are not only a new therapeutic acquisition, but the tools of a more fundamental transition: the transformation of cancer from a rapidly fatal disease into a chronic condition. Antibodies and cancer vaccines can be used for a long time, even beyond progressive disease, and in aged patients, usually unfit for more aggressive conventional treatments. However, this transition to chronicity will require novel developmental guidelines adequate to this kind of drugs, for which optimal dose is not usually the maximal tolerated dose, pharmacokinetics does not define treatment schedule, and tumor shrinkage is not a good correlate of survival. The ongoing cancer immunotherapy program (including several monoclonal antibodies and therapeutic vaccines) at the Centre of Molecular Immunology can illustrate the issues to be addressed, both biological and social, along the path to transform advanced cancer into a chronic non-communicable disease compatible with years of quality life.

Type-1 polarized dendritic cells loaded with apoptotic prostate cancer cells are potent inducers of CD8(+) T cells against prostate cancer cells and defined prostate cancer-specific epitopes

BACKGROUND

In order to develop improved vaccines for patients with recurrent prostate cancer (PCa), we tested the feasibility of using type-1 polarized dendritic cells (αDC1s) to cross-present antigens from allogeneic PCa cells and to induce functional CD8(+) T cell responses against PCa cells and against defined MHC class I-restricted PCa-relevant epitopes.

METHODS

Monocyte-derived DCs from PCa patients were matured using the "standard" cytokine cocktail (IL-1β/TNFα/IL-6/PGE₂) or using the αDC1-polarizing cocktail (IL-1β/TNFα/IFNα/IFNγ/poly-I:C), loaded with UV-irradiated LNCaP cells, and used to sensitize autologous CD8(+) T cells.

RESULTS

αDC1s from PCa patients secreted 10-30 times higher levels of IL-12p70 than sDCs. Importantly this elevated capacity for IL-12p70 secretion was not inhibited by loading with apoptotic tumor cells. Compared to standard DCs, αDC1s induced higher numbers of CD8(+) T cells capable of recognizing both the original PCa cells as well as another PCa cell line, DU145, in MHC class I-restricted fashion. Furthermore, αDC1s induced higher numbers of CD8(+) T cells recognizing defined PCa-specific class I-restricted peptide epitopes of prostate-specific antigen and prostatic acid phosphatase: PAP(135-143) (average 49-fold higher), PAP(112-120) (average 24-fold), PSA(141-150) (average 5.5-fold), and PSA(146-154) (average 11-fold).

CONCLUSION

Type-1 polarization of GM-CSF/IL-4-generated DCs enhances their ability to present allogeneic tumor cells and to induce CD8(+) T cells recognizing different PCa cells and multiple defined PCa-specific epitopes. These observations help to develop improved immunotherapies of PCa for patients with different HLA types and lacking autologous tumor material.

A phase I study of personalized peptide vaccination for advanced urothelial carcinoma patients who failed treatment with methotrexate, vinblastine, adriamycin and cisplatin

OBJECTIVE

• To investigate the safety and immune responses of 12 consecutive weeks of once-weekly personalized peptide vaccine (PPV) administration in patients with advanced urothelial carcinoma (UC) for whom therapy with methotrexate, vinblastine, adriamycin and cisplatin (MVAC) has failed.

PATIENTS AND METHODS

• A phase I trial was designed. Ten patients with MVAC-refractory advanced or metastatic UC were treated with weekly personalized peptide vaccine 12 times using positive peptides chosen from 14 and 16 peptides in patients with human leucocyte antigens A24 and A2, respectively. • Peptide-specific cytotoxic T lymphocyte precursor analysis by interferon-γ production and peptide-reactive immunoglobulin G (IgG) using an enzyme-linked immunosorbent assay was monitored during the treatment.

RESULTS

• The peptide vaccination was safe and well tolerated with no major adverse effects. Increased cytotoxic T lymphocyte response and the anti-peptide IgG titre were revealed by the post-vaccination sera in eight patients. • Clinical responses were as follows: one complete response, one partial response, two stable disease and six progressive disease. • Median progression-free survival and overall survival were 3.0 and 8.9 months, respectively. In the four responders, median progression-free survival and overall survival were 21 and 24 months, respectively.

CONCLUSIONS

• This phase I study showed the safety of and boosted immune responses in response to PPV for advanced UC. • The potential efficacy of 12 consecutive weekly vaccinations with PPV in patients with advanced UC merits further investigation based on these findings.

Minimal information about T cell assays: the process of reaching the community of T cell immunologists in cancer and beyond

Many assays to evaluate the nature, breadth, and quality of antigen-specific T cell responses are currently applied in human medicine. In most cases, assay-related protocols are developed on an individual laboratory basis, resulting in a large number of different protocols being applied worldwide. Together with the inherent complexity of cellular assays, this leads to unnecessary limitations in the ability to compare results generated across institutions. Over the past few years a number of critical assay parameters have been identified which influence test performance irrespective of protocol, material, and reagents used. Describing these critical factors as an integral part of any published report will both facilitate the comparison of data generated across institutions and lead to improvements in the assays themselves. To this end, the Minimal Information About T Cell Assays (MIATA) project was initiated. The objective of MIATA is to achieve a broad consensus on which T cell assay parameters should be reported in scientific publications and to propose a mechanism for reporting these in a systematic manner. To add maximum value for the scientific community, a step-wise, open, and field-spanning approach has been taken to achieve technical precision, user-friendliness, adequate incorporation of concerns, and high acceptance among peers. Here, we describe the past, present, and future perspectives of the MIATA project. We suggest that the approach taken can be generically applied to projects in which a broad consensus has to be reached among scientists working in fragmented fields, such as immunology. An additional objective of this undertaking is to engage the broader scientific community to comment on MIATA and to become an active participant in the project.

Crosstalk between PKA and Epac regulates the phenotypic maturation and function of human dendritic cells

The cAMP-dependent signaling pathways that orchestrate dendritic cell (DC) maturation remain to be defined in detail. Although cAMP was previously thought to signal exclusively through protein kinase A (PKA), it is now clear that cAMP also activates exchange protein activated by cAMP (Epac), a second major cAMP effector. Whether cAMP signaling via PKA is sufficient to drive DC maturation or whether Epac plays a role has not been examined. In this study, we used cAMP analogs to selectively activate PKA or Epac in human monocyte-derived DCs and examined the effect of these signaling pathways on several hallmarks of DC maturation. We show that PKA activation induces DC maturation as evidenced by the increased cell-surface expression of MHC class II, costimulatory molecules, and the maturation marker CD83. PKA activation also reduces DC endocytosis and stimulates chemotaxis to the lymph node-associated chemokines CXCL12 and CCL21. Although PKA signaling largely suppresses cytokine production, the net effect of PKA activation translates to enhanced DC activation of allogeneic T cells. In contrast to the stimulatory effects of PKA, Epac signaling has no effect on DC maturation or function. Rather, Epac suppresses the effects of PKA when both pathways are activated simultaneously. These data reveal a previously unrecognized crosstalk between the PKA and Epac signaling pathways in DCs and raise the possibility that therapeutics targeting PKA may generate immunogenic DCs, whereas those that activate Epac may produce tolerogenic DCs capable of attenuating allergic or autoimmune disease.

Improved endpoints for cancer immunotherapy trials

Unlike chemotherapy, which acts directly on the tumor, cancer immunotherapies exert their effects on the immune system and demonstrate new kinetics that involve building a cellular immune response, followed by changes in tumor burden or patient survival. Thus, adequate design and evaluation of some immunotherapy clinical trials require a new development paradigm that includes reconsideration of established endpoints. Between 2004 and 2009, several initiatives facilitated by the Cancer Immunotherapy Consortium of the Cancer Research Institute and partner organizations systematically evaluated an immunotherapy-focused clinical development paradigm and created the principles for redefining trial endpoints. On this basis, a body of clinical and laboratory data was generated that supports three novel endpoint recommendations. First, cellular immune response assays generate highly variable results. Assay harmonization in multicenter trials may minimize variability and help to establish cellular immune response as a reproducible biomarker, thus allowing investigation of its relationship with clinical outcomes. Second, immunotherapy may induce novel patterns of antitumor response not captured by Response Evaluation Criteria in Solid Tumors or World Health Organization criteria. New immune-related response criteria were defined to more comprehensively capture all response patterns. Third, delayed separation of Kaplan–Meier curves in randomized immunotherapy trials can affect results. Altered statistical models describing hazard ratios as a function of time and recognizing differences before and after separation of curves may allow improved planning of phase III trials. These recommendations may improve our tools for cancer immunotherapy trials and may offer a more realistic and useful model for clinical investigation.

Vaccine-induced antibody responses in patients with carcinoma

Cancer vaccines based on defined antigens are capable of inducing antibodies that recognize and kill tumor cells. Antibodies are ideally suited to address minimal residual disease, and vaccination in an adjuvant setting may favorably influence the outcome of a disease. The present article gives a short summary of antibody production by B cells, and the mechanism of action of antibodies, as well as a description of the current methods for measuring antibody responses and for assessing their antitumor efficacy in the context of clinical trials. It concludes with an overview of antibody responses induced by vaccines based on structurally defined tumor-associated antigens tested in patients with carcinomas. Correlation between antibody responses, T-cell responses and clinical outcome has been noted in a few studies, signaling the importance of vaccine design and adjuvants to exploit the interactions of the innate and adaptive immune system. However, humoral responses, which may provide a surrogate marker for T-helper responses and simplify monitoring of large Phase III trials, are still not or incompletely explored in many vaccination trials.

Modification of MHC anchor residues generates heteroclitic peptides that alter TCR binding and T cell recognition

Improving T cell Ags by altering MHC anchor residues is a common strategy used to enhance peptide vaccines, but there has been little assessment of how such modifications affect TCR binding and T cell recognition. In this study, we use surface plasmon resonance and peptide-MHC tetramer binding at the cell surface to demonstrate that changes in primary peptide anchor residues can substantially and unpredictably alter TCR binding. We also demonstrate that the ability of TCRs to differentiate between natural and anchor-modified heteroclitic peptides distinguishes T cells that exhibit a strong preference for either type of Ag. Furthermore, we show that anchor-modified heteroclitic peptides prime T cells with different TCRs compared with those primed with natural Ag. Thus, vaccination with heteroclitic peptides may elicit T cells that exhibit suboptimal recognition of the intended natural Ag and, consequently, impaired functional attributes in vivo. Heteroclitic peptide-based immune interventions therefore require careful evaluation to ensure efficacy in the clinic.

Novel gamma-chain cytokines as candidate immune modulators in immune therapies for cancer

Cytokines that signal through the common-gamma chain are potent growth factors for T cells and natural killer cells. Interleukin (IL)-2, the gammac prototype, can mediate antitumor effects as a single agent or in the context of multimodality regimens but is limited by side effects and a propensity for expansion of regulatory T cells. IL-7, IL-15, and IL-21 each possess properties that can be exploited in the context of immunotherapy for cancer. Each has been demonstrated to mediate potent vaccine adjuvant effects in tumor models, and each can enhance the effectiveness of adoptive immunotherapies. Although the overlap among the agents is significant, IL-7 is uniquely immunorestorative and preferentially augments reactivity of naive populations, IL-15 potently augments reactivity of CD8 memory cells and natural killer cells, and IL-21 preferentially expands the inflammatory Th17 subset and may limit terminal differentiation of effector CD8 cells. Clinical trials of IL-7 and IL-21 have already been completed and, so far, demonstrate safety and biologic activity of these agents. Clinical trials of IL-15 are expected soon. Ultimately, these agents are expected to be most effective in the context of multimodal immunotherapy regimens, and careful clinical trial design will be needed to efficiently identify the proper doses, regimens, and settings in which to exploit their biologic properties for therapeutic gain.

Overcoming the hurdles of randomised clinical trials of therapeutic cancer vaccines

Most of the recent randomised clinical trials of therapeutic cancer vaccines have failed to demonstrate a meaningful therapeutic benefit to patients over existing treatments. Furthermore, some clinical trials have demonstrated a detrimental effect on patients, resulting in poorer outcomes. These unexpected results have shed light on several important issues to be solved for further development of cancer vaccines. As has been discussed with respect to the use of granulocyte-macrophage colony-stimulating factor (GM-SCF) as an adjuvant, the failures of clinical trials may be explained, in part, by a vaccine-specific adverse event, i.e. the induction of an 'inconvenient immune response' that inhibits pre-existing host immunity. This hypothesis may be supported by the fact that randomised trials of personalised peptide vaccines that were selected in consideration of pre-existing host immunities in individual patients resulted in clear benefit to patients. The development of reliable biomarkers for the selection of appropriate patients and vaccine antigens would thus be pivotal to prevent such vaccine-specific adverse events. This article discusses possible ways to overcome the hurdles of randomised clinical trials of therapeutic cancer vaccines based on a review of recently conducted clinical trials.

Vaccine prevention of cancer: can endogenous antigens be targeted?

This perspective on the report by Beatty et al. in this issue of the journal (beginning on page 438) discusses the prevention of cancer through vaccination strategies that target antigens associated with tumor promotion and progression. Such approaches were first developed for treating cancer. We address cancer vaccination in the context of a mouse model of inflammatory bowel disease expressing MUC1, an epithelial mucin aberrantly expressed during chronic inflammation and in colorectal carcinogenesis, and in a broader context that includes the potential of targeting the tumor microenvironment for immunoprevention in humans. Obstacles in developing effective cancer vaccines, including antigen selection, immunoediting, and tumor-mediated immunosuppression, are also discussed.

Assessing oncologic benefit in clinical trials of immunotherapy agents

BACKGROUND

USA Food and Drug Administration approval for cancer therapy requires demonstration of patient benefit as a marker of clinical efficacy. Prolonged survival is the gold standard for demonstration of efficacy, but other end points such as antitumor response, progression-free survival, quality of life, or surrogate end points may be used.

DESIGN

This study was developed based on discussion during a roundtable meeting of experts in the field of immunotherapy.

RESULTS

In most clinical trials involving cytotoxic agents, response end points use RECIST based on the premise that 'effective' therapy causes tumor destruction, target lesion shrinkage, and prevention of new lesions. However, RECIST may not be appropriate in trials of immunotherapy. Like other targeted agents, immunotherapies may mediate cytostatic rather than direct cytotoxic effects, and these may be difficult to quantify with RECIST. Furthermore, significant time may elapse before clinical effects are quantifiable because of complex response pathways. Effective immunotherapy may even mediate transient lesion growth secondary to immune cell infiltration.

CONCLUSIONS

RECIST may not be an optimal indicator of clinical benefit in immunotherapy trials. This article discusses alternative clinical trial designs and end points that may be more relevant for immunotherapy trials and may offer more effective prediction of survival in pivotal phase III studies.

T-cell-based therapies for malignancy and infection in childhood

One major advance in T-cell-based immunotherapy in the last 20 years has been the molecular definition of numerous viral and tumor antigens. Adoptive T-cell transfer has shown definite clinical benefit in the prophylaxis and treatment of viral infections that develop in pediatric patients after allogeneic transplant and in posttransplant lymphoproliferative disease associated with the Epstein-Barr virus. Developing adoptive T-cell therapies for other malignancies presents additional challenges. This article describes the recent advances in T-cell-based therapies for malignancy and infection in childhood and strategies to enhance the effector functions of T cells and optimize the cellular product, including gene modification and modulation of the host environment.

TAP-inhibitors from old world primate 1-herpesviruses and their use: WO2009008713

Cytotoxic T lymphocytes (CTLs) recognize peptide antigens in the context of major histocompatibility complex (MHC) class I molecules. CTL-mediated immunity is important for defense against cancers and virus infections, and thus viruses and tumors have evolved CTL-evasion mechanisms. The transporter associated with antigen processing (TAP) is a key factor for MHC class I assembly, and TAP is a frequent target of immune evasion by viruses and tumors. WO2009008713 discloses potential therapeutic uses of TAP inhibitors encoded by Epstein-Barr virus and its lymphocryptovirus (LCV) homologs. In particular, WO2009008713 proposes the use of LCV TAP inhibitors and their combinations with other viral TAP inhibitors to elicit novel categories of CTLs that destroy target cells in which the function of TAP or other components of the MHC class I assembly pathway is inhibited. Alternatively, WO2009008713 proposes the use of LCV TAP inhibitors and their combinations with other viral TAP inhibitors to more efficiently generate tumor-specific T-cell epitopes for immunotherapy. The methods described in WO2009008713 offer the promise of new strategies of cancer immunotherapy. However, significant optimization of therapy conditions and characterizations of eligible tumor types will be needed to further develop therapeutic use of TAP inhibitors.

Multiple antigen-targeted immunotherapy with alpha-galactosylceramide-loaded and genetically engineered dendritic cells derived from embryonic stem cells

Numerous tumor-associated antigens (TAA) have been identified and their use in immunotherapy is considered to be promising. For TAA-based immunotherapy to be broadly applied as standard anticancer medicine, methods for active immunization should be improved. In the present study, we demonstrated the efficacy of multiple TAA-targeted dendritic cell (DC) vaccines and also the additive effects of loading alpha-galactosylceramide to DC using mouse melanoma models. On the basis of previously established methods to generate DC from mouse embryonic stem cells (ES-DC), 4 kinds of genetically modified ES-DC, which expressed the melanoma-associated antigens, glypican-3, secreted protein acidic and rich in cysteine, tyrosinase-related protein-2, or gp100 were generated. Anticancer effects elicited by immunization with the ES-DC were assessed in preventive and also therapeutic settings in the models of peritoneal dissemination and spontaneous metastasis to lymph node and lung. The in vivo transfer of a mixture of 3 kinds of TAA-expressing ES-DC protected the recipient mice from melanoma cells more effectively than the transfer of ES-DC expressing single TAA, thus demonstrating the advantage of multiple as compared with single TAA-targeted immunotherapy. Loading ES-DC with alpha-galactosylceramide further enhanced the anticancer effects, suggesting that excellent synergic effects of TAA-specific cytotoxic T lymphocytes and natural killer T cells against metastatic melanoma can be achieved by using genetically modified ES-DC. With the aid of advancing technologies related to pluripotent stem cells, induced pluripotent stem cells, and ES cells, clinical application of DC highly potent in eliciting anticancer immunity will be realized in the near future.

A clinical and immunologic phase 2 trial of Wilms tumor gene product 1 (WT1) peptide vaccination in patients with AML and MDS

This study investigated the immunogenicity of Wilms tumor gene product 1 (WT1)-peptide vaccination in WT1-expressing acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) patients without curative treatment option. Vaccination consisted of granulocyte-macrophage colony-stimulating factor subcutaneously days 1 to 4, and WT1.126-134 peptide and 1 mg keyhole limpet hemocyanin on day 3. The initial 9 patients received 4 vaccinations biweekly, then monthly, and the subsequent 10 patients received continual biweekly vaccination. Seventeen AML patients and 2 refractory anemia with excess blasts patients received a median of 11 vaccinations. Treatment was well tolerated. Objective responses in AML patients were 10 stable diseases (SDs) including 4 SDs with more than 50% blast reduction and 2 with hematologic improvement. An additional 4 patients had clinical benefit after initial progression, including 1 complete remission and 3 SDs. WT1 mRNA levels decreased at least 3-fold from baseline in 35% of patients. In 8 of 18 patients, WT1-tetramer(+) T cells increased in blood and in 8 of 17 patients in bone marrow, with a median frequency in bone marrow of 0.18% at baseline and 0.41% in week 18. This WT1 vaccination study provides immunologic, molecular, and preliminary evidence of potential clinical efficacy in AML patients, warranting further investigations.

Harmonization guidelines for HLA-peptide multimer assays derived from results of a large scale international proficiency panel of the Cancer Vaccine Consortium

Purpose

The Cancer Vaccine Consortium of the Cancer Research Institute (CVC-CRI) conducted a multicenter HLA-peptide multimer proficiency panel (MPP) with a group of 27 laboratories to assess the performance of the assay.

Experimental design

Participants used commercially available HLA-peptide multimers and a well characterized common source of peripheral blood mononuclear cells (PBMC). The frequency of CD8+ T cells specific for two HLA-A2-restricted model antigens was measured by flow cytometry.

The panel design allowed for participants to use their preferred staining reagents and locally established protocols for both cell labeling, data acquisition and analysis.

Results

We observed significant differences in both the performance characteristics of the assay and the reported frequencies of specific T cells across laboratories. These results emphasize the need to identify the critical variables important for the observed variability to allow for harmonization of the technique across institutions.

Conclusions

Three key recommendations emerged that would likely reduce assay variability and thus move toward harmonizing of this assay. (1) Use of more than two colors for the staining (2) collect at least 100,000 CD8 T cells, and (3) use of a background control sample to appropriately set the analytical gates. We also provide more insight into the limitations of the assay and identified additional protocol steps that potentially impact the quality of data generated and therefore should serve as primary targets for systematic analysis in future panels. Finally, we propose initial guidelines for harmonizing assay performance which include the introduction of standard operating protocols to allow for adequate training of technical staff and auditing of test analysis procedures.

Electronic supplementary material

The online version of this article (doi:10.1007/s00262-009-0681-z) contains supplementary material, which is available to authorized users.

Immunotherapy in acute leukemia

Recent advances in immunotherapy of cancer may represent a successful example in translational research, in which progress in knowledge and technology in immunology has led to new strategies of immunotherapy, and even past failures in many clinical trials have led to a better understanding of basic cancer immunobiology. This article reviews the latest concepts in antitumor immunology and its application in the treatment of cancer, with particular focus on acute leukemia.

Recent advances in cancer vaccines: an overview

The field of cancer vaccines is currently in an active state of clinical investigations. Human papilloma virus vaccine has been approved as a prophylactic cancer vaccine, while Oncophage (heat shock protein-peptide complex) was recently approved in Russia for a certain stage of kidney cancer, although to date none has been approved in Japan or the USA. We reviewed recent clinical trials of several different types of cancer vaccines, mainly by using PubMed from 2005 to 2008. There have been slow but substantial advances in peptide vaccines and dendritic cell-based vaccines with regard to both clinical responses and immunological markers. A personalized approach to boost immune responses, addition of chemotherapy to overcome robust cancers and changing of endpoints from tumor reduction to overall survival seem to be the three key elements for the development of therapeutic cancer vaccines.

Telomerase as a universal tumor antigen for cancer vaccines

T-cell immunotherapy relies on the fundamental concept that tumor antigens exist and are presented in the context of MHC molecules for recognition by specific T cells capable of cytolysis. However, heterogeneous expression of most characterized tumor antigens limits the broad applicability of cancer vaccines that target such antigens. Telomerase, on the other hand, represents a prototype of a universal tumor antigen due to both its expression by the vast majority of tumors and its inherent functional involvement in oncogenic transformation. Given these attractive features, the identification of epitopes within human telomerase reverse transcriptase (hTERT), the catalytic subunit of telomerase, has led to the investigation of this tumor antigen as a broadly applicable immunological target. Basic immunological analyses have revealed that hTERT is immunogenic, and initial clinical trials of multiple vaccine formulations have demonstrated that hTERT-specific immune responses can be safely induced in patients and impact on clinical outcomes. Second-generation vaccines are now addressing strategies to enhance cellular immunity against hTERT without toxicity. Findings obtained from these trials will inform the possibility of broad-spectrum cancer immunotherapy or even immunoprevention.

Cell based cancer vaccines: regulatory and commercial development

There is both clinical and regulatory drive to expedite development of safe, efficacious cancer therapies. Stimulation of the patients immune system through vaccination with tumour cells has long been at the vanguard of cancer therapeutic vaccines, and several have been demonstrated to be safe and to have efficacy in early clinical trials for a range of cancers including melanoma, renal cell carcinoma, prostate and colorectal cancers. A number of development-stage vaccines and strategies are currently being tested, utilising either autologous or allogeneic tumour cells, which may also have been ex vivo manipulated (e.g. cytokine transfected cells). It seems likely that clinical trial success, and hence patient benefit, could be improved through better patient identification, possibly by the discovery and use of novel immune response biomarkers. In this review, we aim to summarise the state of tumour cell vaccines in commercial development and to explore not only the difficulties of determining efficacy, but also the production challenges faced when developing a vaccine from proof of principle to pivotal phase III trials.