Vaccination regimens incorporating CpG-containing oligodeoxynucleotides and IL-2 generate antigen-specific antitumor immunity from T-cell populations undergoing homeostatic peripheral expansion after BMT

HPV-Associated Tumor Eradication by Vaccination with Synthetic Short Peptides and Particle-Forming Liposomes

Human papilloma virus (HPV)-16 is associated with cervical cancers and induces expression of the E6 and E7 oncogenes. Using a murine cell line that expresses these, the genes are sequenced, and six predicted major histocompatibility complex (MHC) class I (MHC-I) epitopes are identified. A liposomal vaccine adjuvant based on cobalt-porphyrin-phospholipid (CoPoP) is admixed with synthetic 9-mer epitopes appended with three histidine residues, resulting in rapid formation of peptide-liposome particles. Immunization with multivalent peptides leads to protection from tumor challenge. Of the peptides screened, only the previously identified E749-57 epitope is functional. The peptide-liposome particles that form upon mixing E7HHH49-57 with CoPoP liposomes are stable in serum and are avidly taken up by immune cells in vitro. Immunization results in robust protection from tumor challenge and re-challenge. A 100 ng peptide dose protects mice in a therapeutic tumor challenge when admixed with CoPoP liposomes, whereas 200-fold higher peptide doses are ineffective with the polyinosinic-polycytidylic (poly(I:C)) adjuvant. CoPoP induces a strong infiltrating CD8+ T-cell response within the tumor microenvironment with an improved functional profile. Vaccine monotherapy using nanogram dosing of the E7HHH49-57 peptide admixed with CoPoP reverses the growth of large established tumors, eradicating subcutaneous tumors upwards of 100 mm3 . Immunization also eradicates lung tumors in a metastasis model.

Analogue peptides for the immunotherapy of human acute myeloid leukemia

The use of peptide vaccines, enhanced by adjuvants, has shown some efficacy in clinical trials. However, responses are often short-lived and rarely induce notable memory responses. The reason is that self-antigens have already been presented to the immune system as the tumor develops, leading to tolerance or some degree of host tumor cell destruction. To try to break tolerance against self-antigens, one of the methods employed has been to modify peptides at the anchor residues to enhance their ability to bind major histocompatibility complex molecules, extending their exposure to the T-cell receptor. These modified or analogue peptides have been investigated as stimulators of the immune system in patients with different cancers with variable but sometimes notable success. In this review we describe the background and recent developments in the use of analogue peptides for the immunotherapy of acute myeloid leukemia describing knowledge useful for the application of analogue peptide treatments for other malignancies.

Repositioning therapeutic cancer vaccines in the dawning era of potent immune interventions

Based on lessons learned with various immune interventions, this review aims to provide a constructive framework for repositioning therapeutic cancer vaccination. Intensive research throughout the past decade has identified key hurdles interfering with the efficacy of cancer vaccines. The vaccination concept still holds promise if positioned appropriately in minimal residual disease and select early disease stage cancer indications. However, in advanced cancer, it must be integrated with complementary immune interventions to ensure reconstruction of a functional immune repertoire and simultaneous blockade of immune inhibiting mechanisms. Vaccination could render complex and integrative immune interventions simpler, safer and more effective. The near future will witness an explosion of activities in the cancer immunotherapy arena, witnessing a rational repositioning of vaccines rather than their extinction.

Myeloablative temozolomide enhances CD8⁺ T-cell responses to vaccine and is required for efficacy against brain tumors in mice

Temozolomide (TMZ) is an alkylating agent shown to prolong survival in patients with high grade glioma and is routinely used to treat melanoma brain metastases. A prominent side effect of TMZ is induction of profound lymphopenia, which some suggest may be incompatible with immunotherapy. Conversely, it has been proposed that recovery from chemotherapy-induced lymphopenia may actually be exploited to potentiate T-cell responses. Here, we report the first demonstration of TMZ as an immune host-conditioning regimen in an experimental model of brain tumor and examine its impact on antitumor efficacy of a well-characterized peptide vaccine. Our results show that high-dose, myeloablative (MA) TMZ resulted in markedly reduced CD4(+), CD8(+) T-cell and CD4(+)Foxp3(+) TReg counts. Adoptive transfer of naïve CD8(+) T cells and vaccination in this setting led to an approximately 70-fold expansion of antigen-specific CD8(+) T cells over controls. Ex vivo analysis of effector functions revealed significantly enhanced levels of pro-inflammatory cytokine secretion from mice receiving MA TMZ when compared to those treated with a lower lymphodepletive, non-myeloablative (NMA) dose. Importantly, MA TMZ, but not NMA TMZ was uniquely associated with an elevation of endogenous IL-2 serum levels, which we also show was required for optimal T-cell expansion. Accordingly, in a murine model of established intracerebral tumor, vaccination-induced immunity in the setting of MA TMZ-but not lymphodepletive, NMA TMZ-led to significantly prolonged survival. Overall, these results may be used to leverage the side-effects of a clinically-approved chemotherapy and should be considered in future study design of immune-based treatments for brain tumors.

The tipping point for combination therapy: cancer vaccines with radiation, chemotherapy, or targeted small molecule inhibitors

Therapeutic cancer vaccines are a unique treatment modality in that they initiate a dynamic process of activating the host immune system, which can then be exploited by concurrent or subsequent therapies. The addition of immunotherapy to standard-of-care cancer therapies has shown evidence of efficacy in preclinical models and in the clinical setting. This review examines the preclinical and clinical interactions between vaccine-mediated tumor-specific immune responses and local radiation, systemic chemotherapy, or select small molecule inhibitors, as well as the potential synergy between these modalities.

Active vaccination with Dickkopf-1 induces protective and therapeutic antitumor immunity in murine multiple myeloma

Dickkopf-1 (DKK1), broadly expressed in myeloma cells but highly restricted in normal tissues, together with its functional roles as an osteoblast formation inhibitor, may be an ideal target for immunotherapy in myeloma. Our previous studies have shown that DKK1 (peptide)-specific CTLs can effectively lyse primary myeloma cells in vitro. The goal of this study was to examine whether DKK1 can be used as a tumor vaccine to elicit DKK1-specific immunity that can control myeloma growth or even eradicate established myeloma in vivo. We used DKK1-DNA vaccine in the murine MOPC-21 myeloma model, and the results clearly showed that active vaccination using the DKK1 vaccine not only was able to protect mice from developing myeloma, but it was also therapeutic against established myeloma. Furthermore, the addition of CpG as an adjuvant, or injection of B7H1-blocking or OX40-agonist Abs, further enhanced the therapeutic effects of the vaccine. Mechanistic studies revealed that DKK1 vaccine elicited a strong DKK1- and tumor-specific CD4+ and CD8+ immune responses, and treatment with B7H1 or OX40 Abs significantly reduced the numbers of IL-10-expressing and Foxp3+ regulatory T cells in vaccinated mice. Thus, our studies provide strong rationale for targeting DKK1 for immunotherapy of myeloma patients.

Exploitation of differential homeostatic proliferation of T-cell subsets following chemotherapy to enhance the efficacy of vaccine-mediated antitumor responses

The 5-year survival rate for stage IB-III non-small-cell lung cancer (NSCLC) remains 15%. Surgical resection followed by adjuvant chemotherapy with cisplatin and vinorelbine is one standard-of-care. We sought to determine in a preclinical model whether (a) the combination of cisplatin and vinorelbine could positively modulate components of the immune system independent of antitumor activity, and (b) there were synergistic effects of this drug combination and vaccine immunotherapy. We examined the effect of cisplatin/vinorelbine on gene expression, cell-surface phenotype, and CTL-mediated cytolysis of murine lung carcinoma cells in vitro; we also assessed the effects of cisplatin/vinorelbine on immune subsets and function of Tregs in vivo. Finally, we evaluated the potential synergy between chemotherapy and a recombinant yeast-CEA vaccine in a murine model transgenic for CEA with mice bearing lung tumors. These studies demonstrate that exposure of lung tumor cells to the platinum doublet cisplatin/vinorelbine modulates tumor cell phenotype and increases sensitivity to CTL-mediated cytolysis. These studies also demonstrate that cisplatin/vinorelbine (a) induces sub-myeloablative leucopenia that differentially modulates reconstitution of Treg versus effector T-cell subsets and (b) can be employed synergistically with vaccine, exploiting homeostatic peripheral expansion of T cells. Antitumor studies show for the first time that cisplatin/vinorelbine combined with vaccine increases the survival of mice with established NSCLC. These findings provide the rationale for the potential clinical benefit of the combined use of vaccine with cisplatin/vinorelbine chemotherapy regimens.

A CpG-loaded tumor cell vaccine induces antitumor CD4+ T cells that are effective in adoptive therapy for large and established tumors

We designed a whole tumor cell vaccine by "loading" lymphoma tumor cells with CG-enriched oligodeoxynucleotide (CpG), a ligand for the Toll-like receptor 9 (TLR9). CpG-loaded tumor cells were phagocytosed, delivering both tumor antigen(s) and the immunostimulatory CpG molecule to antigen-presenting cells (APCs). These APCs then expressed increased levels of costimulatory molecules and induced T-cell immunity. TLR9 was required in the APCs but not in the CpG-loaded tumor cell. We demonstrate that T cells induced by this vaccine are effective in adoptive cellular therapy for lymphoma. T cells from vaccinated mice transferred into irradiated, syngeneic recipients protected against subsequent lymphoma challenge and, remarkably, led to regression of large and established tumors. This therapeutic effect could be transferred by CD4(+) but not by CD8(+) T cells. A CpG-loaded whole-cell vaccination is practical and has strong potential for translation to the clinical setting. It is currently being tested in a clinical trial of adoptive immunotherapy for mantle-cell lymphoma.

DSMM XI study: dose definition for intravenous cyclophosphamide in combination with bortezomib/dexamethasone for remission induction in patients with newly diagnosed myeloma

A clinical trial was initiated to evaluate the recommended dose of cyclophosphamide in combination with bortezomib and dexamethasone as induction treatment before stem cell transplantation for younger patients with newly diagnosed multiple myeloma (MM). Thirty patients were treated with three 21-day cycles of bortezomib 1.3 mg/m(2) on days 1, 4, 8, and 11 plus dexamethasone 40 mg on the day of bortezomib injection and the day after plus cyclophosphamide at 900, 1,200, or 1,500 mg/m(2) on day 1. The maximum tolerated dose of cyclophosphamide was defined as 900 mg/m(2). At this dose level, 92% of patients achieved at least a partial response. The overall response rate [complete response (CR) plus partial response (PR)] across all dose levels was 77%, with a 10% CR rate. No patient experienced progressive disease. The most frequent adverse events were hematological and gastrointestinal toxicities as well as neuropathy. The results suggest that bortezomib in combination with cyclophosphamide at 900 mg/m(2) and dexamethasone is an effective induction treatment for patients with newly diagnosed MM that warrants further investigation.

Proteasome inhibitors in the treatment of multiple myeloma

Targeting intracellular protein turnover by inhibiting the ubiquitin-proteasome pathway as a strategy for cancer therapy is a new addition to our chemotherapeutic armamentarium, and has seen its greatest successes against multiple myeloma. The first-in-class proteasome inhibitor, bortezomib, was initially approved for treatment of patients in the relapsed/refractory setting as a single agent, and was recently shown to induce even greater benefits as part of rationally designed combinations that overcome chemoresistance. Modulation of proteasome function is also a rational approach to achieve chemosensitization to other antimyeloma agents, and bortezomib has now been incorporated into the front-line setting. Bortezomib-based induction regimens are able to achieve higher overall response rates and response qualities than was the case with prior standards of care, and unlike these older approaches, maintain efficacy in patients with clinically and molecularly defined high-risk disease. Second-generation proteasome inhibitors with novel properties, such as NPI-0052 and carfilzomib, are entering the clinical arena, and showing evidence of antimyeloma activity. In this spotlight review, we provide an overview of the current state of the art use of bortezomib and other proteasome inhibitors against multiple myeloma, and highlight areas for future study that will further optimize our ability to benefit patients with this disease.

Lymphoma immunotherapy: vaccines, adoptive cell transfer and immunotransplant

Therapy for non-Hodgkin lymphoma has benefited greatly from basic science and clinical research such that chemotherapy and monoclonal antibody therapy have changed some lymphoma subtypes from uniformly lethal to curable, but the majority of lymphoma patients remain incurable. Novel therapies with less toxicity and more specific targeting of tumor cells are needed and immunotherapy is among the most promising of these. Recently completed randomized trials of idiotype vaccines and earlier-phase trials of other vaccine types have shown the ability to induce antitumor T cells and some clinical responses. More recently, trials of adoptive transfer of antitumor T cells have demonstrated techniques to increase the persistence and antitumor effect of these cells. Herein, we discuss lymphoma immunotherapy clinical trial results and what lessons can be taken to improve their effect, including the combination of vaccination and adoptive transfer in an approach we have dubbed 'immunotransplant'.

Systemic immune effects of adjuvant chemotherapy with 5-fluorouracil, epirubicin and cyclophosphamide and/or radiotherapy in breast cancer: a longitudinal study

Immunotherapy is being increasingly utilized for adjuvant treatment for breast cancer (BC). We have previously described immune functions during primary therapy for BC. The present study describes immune recovery patterns during long-term, unmaintained follow-up after completion of adjuvant therapy.A group of patients with primary BC had been treated with adjuvant radio-chemotherapy (RT + CT) 5-fluorouracil, epirubicin and cyclophosphamide (FEC) (n = 21) and another group with radiotherapy (RT) (n = 20) alone. Immunological testing of NK and T-cell functions was performed initially at the end of adjuvant treatment and repeated after 2, 6 and 12 months. NK cell cytotoxicity was significantly higher (P < 0.05) at all time-points in patients than in age-matched controls and did not differ between the two treatments groups during one year observation. In contrast, lower numbers of CD4 T-cells and lower expression of CD28 on T-cells was observed particularly in RT + CT patients and did not normalize during the observation period. The numbers of T(reg) cells (CD4(+)CD25(high)) were low in the RT + CT group during follow-up, as well as expression of TCRxi, Zap70, p56(lck), P59(fyn) and PI3 k in CD4(+) cells. In contrast, expression of intracellular cytokines (IFN-gamma, IL-2, IL-4) in CD4 and CD8 T cells were significantly higher in RT + CT patients than in the RT group and the difference increased during follow-up. In conclusion, NK-cell cytotoxicity increased during unmaintained long-term follow-up whereas CD4 and regulatory T cells as well as signal transduction molecules remained low following adjuvant radio-chemotherapy.

Keratinocyte growth factor enhances DNA plasmid tumor vaccine responses after murine allogeneic bone marrow transplantation

Keratinocyte growth factor (KGF), which is given exogenously to allogeneic bone marrow transplantation (allo-BMT) recipients, supports thymic epithelial cells and increases thymic output of naive T cells. Here, we demonstrate that this improved T-cell reconstitution leads to enhanced responses to DNA plasmid tumor vaccination. Tumor-bearing mice treated with KGF and DNA vaccination have improved long-term survival and decreased tumor burden after allo-BMT. When assayed before vaccination, KGF-treated allo-BMT recipients have increased numbers of peripheral T cells, including CD8(+) T cells with vaccine-recognition potential. In response to vaccination, KGF-treated allo-BMT recipients, compared with control subjects, generate increased numbers of tumor-specific CD8(+) cells, as well as increased numbers of CD8(+) cells producing interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha). We also found unanticipated benefits to antitumor immunity with the administration of KGF. KGF-treated allo-BMT recipients have an improved ratio of T effector cells to regulatory T cells, a larger fraction of effector cells that display a central memory phenotype, and effector cells that are derived from a broader T-cell-receptor repertoire. In conclusion, our data suggest that KGF can function as a potent vaccine adjuvant after allo-BMT through its effects on posttransplantation T-cell reconstitution.

Toll-like receptors in tumor immunotherapy

Lymphodepletion with chemotherapeutic agents or total body irradiation (TBI) before adoptive transfer of tumor-specific T cells is a critical advancement in the treatment of patients with melanoma. More than 50% of patients that are refractory to other treatments experience an objective or curative response with this approach. Emerging data indicate that the key mechanisms underlying how TBI augments the functions of adoptively transferred T cells include (a) the depletion of regulatory T cells (T(reg)) and myeloid-derived suppressor cells that limit the function and proliferation of adoptively transferred cells; (b) the removal of immune cells that act as "sinks" for homeostatic cytokines, whose levels increase after lymphodepletion; and (c) the activation of the innate immune system via Toll-like receptor 4 signaling, which is engaged by microbial lipopolysaccharide that translocated across the radiation-injured gut. Here, we review these mechanisms and focus on the effect of Toll-like receptor agonists in adoptive immunotherapy. We also discuss alternate regimens to chemotherapy or TBI, which might be used to safely treat patients with advanced disease and promote tumor regression.

A comparison and critical analysis of preclinical anticancer vaccination strategies

Anticancer vaccines have been extensively studied in animal models and in clinical trials. While vaccination can lead to tumor protection in numerous murine models, objective tumor regressions after anticancer vaccination in clinical trials have been rare. B16 is a poorly immunogenic murine melanoma that has been extensively used in anticancer vaccination experiments. Because B16 has been widely used, different vaccination strategies can be compared. We reviewed the results obtained when B16 was treated with five common vaccine types: recombinant viral vaccines, DNA vaccines, dendritic cell vaccines, whole-tumor vaccines, and peptide vaccines. We also reviewed the results obtained when B16 was treated with vaccines combined with adoptive transfer of tumor antigen-specific T cells. We found several characteristics of vaccination regimens that were associated with antitumor efficacy. Many vaccines that incorporated xenogeneic antigens exhibited more potent anticancer activity than vaccines that were identical except that they incorporated the syngeneic version of the same antigen. Interleukin-2 enhanced the antitumor efficacy of several vaccines. Finally, several effective regimens generated large numbers of tumor antigen-specific CD8(+) T cells. Identification of vaccine characteristics that are associated with antitumor efficacy may aid in the development of more effective anticancer vaccination strategies.

Maximizing CD8+ T cell responses elicited by peptide vaccines containing CpG oligodeoxynucleotides

We assessed the ability of several factors to increase the size of tumor-antigen-specific CD8(+) T cell responses elicited by vaccines incorporating peptides and CpG-containing oligodeoxynucleotides (CpG). Neither granulocyte-macrophage colony-stimulating factor (GM-CSF) nor an immunogenic MHC class II-presented "helper" peptide increased the size of epitope-specific CD8+ T cell responses elicited by peptide+CpG-containing vaccines. In contrast, low-dose subcutaneous interleukin (IL)-2 dramatically increased the size of splenic and peripheral blood epitope-specific CD8(+) T cell responses generated by peptide+CpG-containing vaccines. Moreover, peptide+CpG-containing vaccines plus low-dose IL-2 mediated anti-tumor immunity. A prime-boost vaccination schedule elicited larger CD8(+) T cell responses than a weekly vaccination schedule. Including larger doses of peptide in vaccines led to larger vaccine-elicited CD8(+) T cell responses. Clinical trials of CpG-containing peptide vaccines are ongoing. These findings suggest strategies to increase the size of CD8(+) T cell responses generated by CpG-containing peptide vaccines that could be tested in future clinical trials.