Identification of an immunodominant peptide of HER-2/neu protooncogene recognized by ovarian tumor-specific cytotoxic T lymphocyte lines

Nondominant CD8 T cells are active players in the vaccine-induced antitumor immune response

We previously reported that CD8(+) T cells are directed predominantly toward the immunodominant Her-2/neu (neu) epitope RNEU(420-429) in nontolerized FVB/N but not tolerized HER-2/neu (neu-N) mice. In this study, we screened overlapping peptides of the entire neu protein and identified six new epitopes recognized by vaccine-induced neu-N-derived T cells. Evaluation of individual nondominant responses by tetramer staining and IFN-γ secretion demonstrate that this repertoire is peripherally tolerized. To address the role that the complete CD8(+) T cell repertoire plays in vaccine-induced antitumor immunity, we created a whole-cell vaccine-expressing neu cDNA that has been mutated at the RNEU(420-429) anchor residue, thereby abrogating activation of immunodominant epitope responses. Studies comparing the mutated and nonmutated vaccines indicate that nondominant CD8(+) T cells can induce antitumor immunity when combined with regulatory T cell-depleting agents in both neu-N and FVB/N mice. Collectively, these studies demonstrate that the neu-directed T cell repertoire is not intrinsically incapable of eradicating tumors. Rather, they are suppressed by mechanisms of peripheral tolerance. Thus, these studies provide new insights into the function of the complete T cell repertoire directed toward a clinically relevant tumor Ag in tumor-bearing hosts.

MHC class I-presented tumor antigens identified in ovarian cancer by immunoproteomic analysis are targets for T-cell responses against breast and ovarian cancer

PURPOSE

The purpose of this study is to test whether peptide epitopes chosen from among those naturally processed and overpresented within MHC molecules by malignant, but not normal cells, when formulated into cancer vaccines, could activate antitumor T-cell responses in humans.

EXPERIMENTAL DESIGN

Mixtures of human leukocyte antigen A2 (HLA-A2)-binding ovarian cancer-associated peptides were used to activate naive T cells to generate antigen-specific T cells that could recognize ovarian and breast cancers in vitro. Combinations of these peptides (0.3 mg of each peptide or 1 mg of each peptide) were formulated into vaccines in conjunction with Montanide ISA-51 and granulocyte monocyte colony stimulating factor which were used to vaccinate patients with ovarian and breast cancer without evidence of clinical disease in parallel pilot clinical trials.

RESULTS

T cells specific for individual peptides could be generated in vitro by using mixtures of peptides, and these T cells recognized ovarian and breast cancers but not nonmalignant cells. Patient vaccinations were well tolerated with the exception of local erythema and induration at the injection site. Nine of the 14 vaccinated patients responded immunologically to their vaccine by inducing peptide-specific T-cell responses that were capable of recognizing HLA-matched breast and ovarian cancer cells.

CONCLUSION

Mixtures of specific peptides identified as naturally presented on cancer cells and capable of activating tumor-specific T cells in vitro also initiate or augment immune responses toward solid tumors in cancer patients.

Immunotherapy for ovarian cancer: what's next?

In the past decade, we have witnessed important gains in the treatment of ovarian cancer; however, additional advances are required to reduce mortality. With compelling evidence that ovarian cancers are immunogenic tumors, immunotherapy should be further pursued and optimized. The dramatic advances in laboratory and clinical procedures in cellular immunotherapy, along with the development of powerful immunomodulatory antibodies, create new opportunities in ovarian cancer therapeutics. Herein, we review current progress and future prospects in vaccine and adoptive T-cell therapy development as well as immunomodulatory therapy tools available for immediate clinical testing.

HER-2/neu as a target for cancer vaccines

A novel modality toward the treatment of HER-2/neu-positive malignancies, mostly including breast and, more recently prostate carcinomas, has been the use of vaccines targeting HER-2/neu extracellular and intracellular domains. HER-2/neu-specific vaccines have been demonstrated to generate durable T-cell anti-HER-2/neu immunity when tested in Phase I and II clinical trials with no significant toxicity or autoimmunity directed against normal tissues. Targeting of HER-2/neu in active immunotherapy may involve peptide and DNA vaccines. Moreover, active anti-HER-2/neu immunization could facilitate the ex vivo expansion of HER-2/neu-specific T cells for use in adoptive immunotherapy for the treatment of established metastatic disease. In addition, early data from trials examining the potential use of HER-2/neu-based vaccines in the adjuvant setting to prevent the relapse of breast cancer in high-risk patients have shown promising results. Future approaches include multiepitope preventive vaccines and combinatorial treatments for generating the most efficient protective anti-tumor immunity.

Targeting the epidermal growth factor receptor (HER) family by T cell receptor gene-modified T lymphocytes

Human epidermal growth factor receptor 2 (HER2) has been successfully targeted as a breast cancer-associated antigen by various strategies. HER2 is also overexpressed in other solid tumors such as stomach cancer, as well as in hematological malignancies such as acute lymphoblastic leukemia. HER2-targeted therapies are currently under clinical investigation for a panel of malignancies. In this study, we isolated the T cell receptor (TCR) genes of a HER2-reactive allo-human leukocyte antigen-A2-restricted CTL clone and introduced the TCRα- and β-chain genes into the retrovirus vector MP71. Murinization and codon optimization of the HER2-reactive TCR was required for efficient TCR expression in primary human T cells. The tumor recognition efficiency of HER2-TCR gene-modified T cells was similar to the parental CTL clone from which the TCR genes were isolated. The known cross-reactivity of the HER2-reactive TCR with HER3 and HER4 was retained when the TCR was transduced into primary T cells. Our results could contribute to the development of a TCR-based approach for the treatment of HER2-positive breast cancer, as well as of other malignancies expressing HER2, HER3, and/or HER4.

Inverse correlation of HER2 with MHC class I expression on oesophageal squamous cell carcinoma

BACKGROUND

As HER2 is expressed in 30% of oesophageal squamous cell carcinomas (ESCCs), T-cell-based immunotherapy and monoclonal antibodies targeted against HER2 are attractive, novel approaches for ESCCs. However, it was shown that there is an inverse correlation between HER2 and MHC class I expression on tumours. Thus, the correlation between HER2 and MHC class I expressions on ESCC was evaluated.

METHODS

Expressions of MHC class I and HER2 in ESCC tissues (n=80) and cell lines were assessed by immunohistochemistry, fluorescence in situ hybridisation (FISH), and flow cytometry. We investigated whether HER2 downregulation with small interfering RNA (siRNA) in ESCC cell lines could upregulate the expression of MHC class I and the antigen presentation machinery components, and could increase their sensitivity for tumour antigen-specific CTLs.

RESULTS

There was an inverse correlation between HER2 and MHC class I expressions in both tumour tissues and cell lines. Downregulation of HER2 with siRNA resulted in the upregulation of MHC class I expression, leading to increased CTL recognition by tumour antigen-specific CTLs.

CONCLUSION

HER2-overexpressing ESCC tumour cells showed a reduced sensitivity for CTLs through the downregulation of MHC class I.

Anti-HER2 vaccines: new prospects for breast cancer therapy

Each year, breast cancer accounts for more than 400,000 new cancer cases and more than 130,000 cancer deaths in Europe. Prognosis of nonmetastatic breast cancer patients is directly related to the extent of the disease, mainly nodal spreading and tumor size, and to the molecular profile, particularly HER2 over-expression. In patients with HER2-over-expressing tumors, different studies have shown cellular and/or humoral immune responses against HER2 associated with a lower tumor development at early stages of the disease. These findings have led to the hypothesis that the generation of an anti-HER2 immune response should protect patients from HER2-over-expressing tumor growth. Taken together with the clinical efficiency of trastuzumab-based anti-HER2 passive immunotherapy, these observations allowed to envisage various vaccine strategies against HER2. The induction of a stable and strong immunity by cancer vaccines is expected to lead to establishment of immune memory, thereby preventing tumor recurrence. However, an immunological tolerance against HER2 antigen exists representing a barrier to effective vaccination against this oncoprotein. As a consequence, the current challenge for vaccines is to find the best conditions to break this immunological tolerance. In this review, we will discuss the different anti-HER2 vaccine strategies currently developed; considering the strategies having reached the clinical phases as well as those still in preclinical development. The used antigen can be either composed of tumoral allogenic cells or autologous cells, or specific to HER2. It can be delivered by dendritic cells or in a DNA, peptidic or proteic form. Another area of research concerns the use of anti-idiotypic antibodies mimicking HER2.

Whole tumor antigen vaccines

Although cancer vaccines with defined antigens are commonly used, the use of whole tumor cell preparations in tumor immunotherapy is a very promising approach and can obviate some important limitations in vaccine development. Whole tumor cells are a good source of TAAs and can induce simultaneous CTLs and CD4(+) T helper cell activation. We review current approaches to prepare whole tumor cell vaccines, including traditional methods of freeze-thaw lysates, tumor cells treated with ultraviolet irradiation, and RNA electroporation, along with more recent methods to increase tumor cell immunogenicity with HOCl oxidation or infection with replication-incompetent herpes simplex virus.

A virosomal formulated Her-2/neu multi-peptide vaccine induces Her-2/neu-specific immune responses in patients with metastatic breast cancer: a phase I study

We have previously shown in mice that vaccination with three Her-2-peptides representing B-cell epitopes of the extracellular domain of Her-2/neu induces Her-2/neu-specific IgG antibodies with strong anti-tumor activity in vitro and in vivo. We have now finalized a phase I clinical trial with an anti-Her-2/neu vaccine-construct of immunopotentiating reconstituted influenza virosomes with the three peptides in patients with metastatic breast cancer (MBC). Ten MBC patients with low protein overexpression of Her-2/neu of MBC (+ or ++ upon immunohistochemistry, FISH negative) and positive hormone receptor status were enrolled in a single center phase I study. The virosomal formulated vaccine, consisting of 10 microg/peptide, was intramuscularly applied three times on days 1, 28, and 56. The primary endpoint of the study, which lasted 12 weeks, was safety, the secondary endpoint immunogenicity. Local erythema at the injection site was the only vaccine-related side effect occurring in four patients. In 8 of 10 patients an increase in peptide-specific antibody titer measured by ELISA was found. Importantly, the induced antibodies were also directed against the native Her-2/neu protein. Cellular immune responses, as measured by in vitro production of IL-2, IFN-c, and TNF-a of PBMCs showed a marked increase after vaccination in the majority of vaccinees. Notably, the number of CD4+CD25+Foxp3+T regulatory cells, which were significantly increased compared to healthy controls prior to vaccination, was markedly reduced following vaccination. In all, the immunological responses after vaccination indicated that the patients in stage IV of disease were immunocompetent and susceptible to vaccination. The Her-2/neu multipeptide vaccine was safe, well tolerated and effective in overcoming immunological tolerance to Her-2/neu. The induction of anti-Her-2-specific antibodies could result in clinical benefit comparable to passive anti-Her-2 antibody therapy.

Results of the first phase 1 clinical trial of the HER-2/neu peptide (GP2) vaccine in disease-free breast cancer patients: United States Military Cancer Institute Clinical Trials Group Study I-04

BACKGROUND

HER-2/neu, overexpressed in breast cancer, is a source of immunogenic peptides that include GP2 and E75. Phase 2 testing of E75 as an adjuvant vaccine has suggested a clinical benefit. GP2, derived from the transmembrane portion of HER-2/neu, has differing binding characteristics and may be more immunogenic than E75. Results of the first phase 1 trial of GP2 peptide vaccine are presented.

METHODS

Disease-free, lymph node-negative, human leukocyte antigen (HLA)-A2(+) breast cancer patients were enrolled. This dose escalation trial included 4 groups to determine safety and optimal GP2 peptide/granulocyte-macrophage colony-stimulating factor (GM-CSF) dose. Toxicities were monitored. Immunologic response was assessed ex vivo via the HLA-A2:immunoglobulin dimer assay to detect GP2-specific CD8(+) T cells (and E75-specific CD8(+) T cells to assess epitope spreading) and in vivo via delayed type hypersensitivity (DTH) reaction (medians/ranges).

RESULTS

Eighteen patients were enrolled. All toxicities were grade < or =2. Eight (88.9%) of 9 patients in the first 3 dose groups required GM-CSF dose reductions for local reactions > or =100 mm or grade > or =2 systemic toxicity. GM-CSF dose was reduced to 125 microg for the final dose group. All patients responded immunologically ex vivo (GP2-specific CD8(+) T cells from prevaccination to maximum, 0.4% [0.0%-2.0%] to 1.1% [0.4%-3.6%], P < .001) and in vivo (GP2 pre- to postvaccination DTH, 0 mm [0.0-19.5 mm] to 27.5 mm [0.0-114.5 mm, P < .001). E75-specific CD8(+) T cells also increased in response to GP2 from prevaccination to maximum (0.8% [0.0%-2.41%] to 1.6% [0.86%-3.72%], P < .001).

CONCLUSIONS

The GP2 peptide vaccine appears safe and well tolerated with minimal local/systemic toxicity. GP2 elicited HER-2/neu-specific immune responses, including epitope spreading, in high-risk, lymph node-negative breast cancer patients. These findings support further investigation of the GP2 vaccine for the prevention of breast cancer recurrence.

Clinical and immunologic responses of HLA-A3+ breast cancer patients vaccinated with the HER2/neu-derived peptide vaccine, E75, in a phase I/II clinical trial

BACKGROUND

We have treated disease-free breast cancer patients with an HER2/neu-derived peptide, E75, as an adjuvant vaccine. E75 was originally described as HLA-A2-restricted and has been previously tested in this population. Based on computer modeling, E75 is predicted to bind to HLA-A3, and preclinical data support this. We conducted a clinical trial of E75 in HLA-A3(+), A2(-) (A3) patients.

STUDY DESIGN

Disease-free breast cancer patients were enrolled after standard therapy in phase I/II trials. A3 patients were enrolled in parallel with A2 patients and vaccinated with E75 and granulocyte-macrophage colony-stimulating factor immunoadjuvant. A2(-), A3(-) patients were followed as controls. Toxicities were graded. Immunologic responses were assessed by delayed-type hypersensitivity reactions and E75-specific interferon-gamma enzyme-linked immunosorbent spot assay. Clinical recurrences were documented.

RESULTS

Thirteen A3 patients completed the vaccine schedule. Clinicopathologic features were similar between A3, A2, and control patients, except for more HER2/neu-overexpressing tumors in the A2 group and more estrogen-receptor/progesterone-receptor-negative tumors in A2 and A3 groups. Toxicity profiles and postvaccination delayed-type hypersensitivity were similar in A3 and A2 patients. Enzyme-linked immunosorbent spot assay results varied, but A3 patients' median spots increased pre- to postvaccination (p = 0.2). Recurrences were lower in the A3 group (7.7%) at 30-month median follow-up compared with published recurrence in A2-vaccinated (8.3%) and control groups (14.8%) at 26-month median follow-up.

CONCLUSIONS

HLA restriction limits potential use of peptide-based cancer vaccines. This trial demonstrates that HLA-A3 patients respond similarly to E75 vaccination as HLA-A2 patients, suggesting the potential use of the E75 vaccine in up to 76% of the population.

The emergence of immunomodulation: combinatorial immunochemotherapy opportunities for the next decade

In the past decade we have witnessed important advances in the treatment of gynecological cancers and have recognized their potential immunogenicity. This has opened the door to explore immune therapy not only in HPV-induced cancers but also in ovarian and endometrial cancers. Here we will review the off-target immune effects of select chemotherapy drugs commonly used to treat gynecologic cancers and novel tools that can stimulate both the adaptive and innate immune mechanisms such as novel pleiotropic cytokines, Toll-like receptors, and powerful antibodies that can target inhibitory checkpoints, thereby activating effector cellular immune mechanisms and neutralizing suppressor cells. We will also review how existing drugs can be used for combinatorial tumor therapy.

Antigen-specific Tregs control T cell responses against a limited repertoire of tumor antigens in patients with colorectal carcinoma

Spontaneous antitumor T cell responses in cancer patients are strongly controlled by Tregs, and increased numbers of tumor-infiltrating Tregs correlate with reduced survival. However, the tumor antigens recognized by Tregs in cancer patients and the impact of these cells on tumor-specific T cell responses have not been systematically characterized. Here we used a broad panel of long synthetic peptides of defined tumor antigens and normal tissue antigens to exploit a newly developed method to identify and compare ex vivo the antigen specificities of Tregs with those of effector/memory T cells in peripheral blood of colorectal cancer patients and healthy subjects. Tregs in tumor patients were highly specific for a distinct set of only a few tumor antigens, suggesting that Tregs exert T cell suppression in an antigen-selective manner. Tumor-specific effector T cells were detectable in the majority of colorectal cancer patients but not in healthy individuals. We detected differences in the repertoires of antigens recognized by Tregs and effector/memory T cells in the majority of colorectal cancer patients. In addition, only effector/memory T cell responses against antigens recognized by Tregs strongly increased after Treg depletion. The selection of antigens according to preexisting T cell responses may improve the efficacy of future immunotherapies for cancer and autoimmune disease.

HER-2/neu (657-665) represents an immunogenic epitope of HER-2/neu oncoprotein with potent antitumor properties

The HER-2/neu oncoprotein is a promising cancer vaccine target. We describe herein a novel HLA-A2.1-restricted epitope, encompassing amino acids 657-665 (AVVGILLVV), which is naturally presented by human breast and ovarian cell lines. HER-2/neu(657-665), [HER-2(9(657))], binds with high affinity to HLA-A2.1 molecules as revealed by a prediction algorithm (SYFPEITHI) and in functional assays. This peptide was found to be immunogenic in HLA-A2.1 transgenic (HHD) mice inducing peptide-specific CTL, which responded with increased IFNgamma production, degranulation, and in vitro as well as in vivo cytotoxicity. Most important, HER-2(9(657)) functioned as a therapeutic vaccine by enabling HHD mice to reject established transplantable tumors. Cured mice resisted tumor growth when re-challenged with the same tumor, demonstrating the capacity of HER-2(9(657)) to generate tumor-specific memory immune response. Finally, this peptide was also found to be immunogenic in PBMCs from HLA-A2.1(+) patients with HER-2/neu(+) breast cancer. Our data encourage further exploitation of HER-2(9(657)) as a promising candidate for peptide-based cancer vaccines.

Phase I active immunotherapy with combination of two chimeric, human epidermal growth factor receptor 2, B-cell epitopes fused to a promiscuous T-cell epitope in patients with metastatic and/or recurrent solid tumors

PURPOSE To evaluate the maximum-tolerated dose (MTD), safety profile, and immunogenicity of two chimeric, B-cell epitopes derived from the human epidermal growth factor receptor (HER2) extracellular domain in a combination vaccine with a promiscuous T-cell epitope (ie, MVF) and nor-muramyl-dipeptide as adjuvant emulsified in SEPPIC ISA 720. PATIENTS AND METHODS Eligible patients with metastatic and/or recurrent solid tumors received three inoculations on days 1, 22, and 43 at doses of total peptide that ranged from 0.5 to 3.0 mg. Immunogenicity was evaluated by enzyme-linked immunosorbent assay, flow cytometry, and HER2 signaling assays. Results Twenty-four patients received three inoculations at the intended dose levels, which elicited antibodies able to recognize native HER2 receptor and inhibited both the proliferation of HER2-expressing cell lines and phosphorylation of the HER2 protein. The MTD was determined to be the highest dose level of 3.0 mg of the combination vaccine. There was a significant increase from dose level 1 (0.5 mg) to dose level 4 (3.0 mg) in HER2-specific antibodies. Four patients (one each with adrenal, colon, ovarian, and squamous cell carcinoma of unknown primary) were judged to have stable disease; two patients (one each with endometrial and ovarian cancer) had partial responses; and 11 patients had progressive disease. Patients with stable disease received 6-month boosts, and one patient received a 20-month boost. CONCLUSION The combination vaccines were safe and effective in eliciting antibody responses in a subset of patients (62.5%) and were associated with no serious adverse events, autoimmune disease, or cardiotoxicity. There was preliminary evidence of clinical activity in several patients.

A novel human Her-2/neu chimeric molecule expressed by Listeria monocytogenes can elicit potent HLA-A2 restricted CD8-positive T cell responses and impact the growth and spread of Her-2/neu-positive breast tumors

PURPOSE

The aim of this study was to efficiently design a novel vaccine for human Her-2/neu-positive (hHer-2/neu) breast cancer using the live, attenuated bacterial vector Listeria monocytogenes.

EXPERIMENTAL DESIGN

Three recombinant L. monocytogenes-based vaccines were generated that could express and secrete extracellular and intracellular fragments of the hHer-2/neu protein. In addition, we generated a fourth construct fusing selected portions of each individual fragment that contained most of the human leukocyte antigen (HLA) epitopes as a combination vaccine (L. monocytogenes-hHer-2/neu chimera).

RESULTS

Each individual vaccine was able to either fully regress or slow tumor growth in a mouse model for Her-2/neu-positive tumors. All three vaccines could elicit immune responses directed toward human leukocyte antigen-A2 epitopes of hHer-2/neu. The L. monocytogenes-hHer-2/neu chimera was able to mimic responses generated by the three separate vaccines and prevent spontaneous outgrowth of tumors in an autochthonous model for Her-2/neu-positive breast cancer, induce tumor regression in transplantable models, and prevent seeding of experimental lung metastases in a murine model for metastatic breast cancer.

CONCLUSION

This novel L. monocytogenes-hHer-2/neu chimera vaccine proves to be just as effective as the individual vaccines but combines the strength of all three in a single vaccination. These encouraging results support future clinical trials using this chimera vaccine and may be applicable to other cancer types expressing the Her-2/neu molecule such as colorectal and pancreatic cancer.

[Anti-HER2 vaccines: The HER2 immunotargeting future?]

Breast cancer is a widely spread women's disease. In spite of progress in the field of surgery and adjuvant therapies, the risk of breast cancer metastatic relapses remains high especially in those overexpressing HER2. Different studies have shown cellular and/or humoral immune responses against HER2 in patients with HER2-overexpressing tumors. This immune response is associated with a lower tumor development at early stages of the disease. These observations, associated with the efficiency today demonstrated by a trastuzumab-based anti-HER2 immunotherapy, allowed to envisage various vaccinal strategies against HER2. These findings have so led to the hypothesis that the generation of an anti-HER2 immune response should protect patients from HER2-overexpressing tumor growth, and induction of a stable and strong immunity by cancer vaccines is expected to lead to establishment of immune memory, thereby preventing tumor recurrence. However, an immunological tolerance against HER2 antigen exists representing a barrier to effective vaccination against this oncoprotein. As a consequence, the current challenge for vaccines is to find the best conditions to break this immunological tolerance. In this review, we will discuss the different anti-HER2 vaccine strategies currently developed; considering the strategies having reached the clinical phases as well as those still in preclinical development. The used antigen can be composed of tumoral allogenic cells or autologous cells or be specific of HER2. It can be delivered by denditric cells or in a DNA, peptidic or proteic form. Another area of the research concerns the use of anti-idiotypic antibodies mimicking HER2.

Targets for active immunotherapy against pediatric solid tumors

The potential role of antibodies and T lymphocytes in the eradication of cancer has been demonstrated in numerous animal models and clinical trials. In the last decennia new strategies have been developed for the use of tumor-specific T cells and antibodies in cancer therapy. Effective anti-tumor immunotherapy requires the identification of suitable target antigens. The expression of tumor-specific antigens has been extensively studied for most types of adult tumors. Pediatric patients should be excellent candidates for immunotherapy since their immune system is more potent and flexible as compared to that of adults. So far, these patients do not benefit enough from the progresses in cancer immunotherapy, and one of the reasons is the paucity of tumor-specific antigens identified on pediatric tumors. In this review we discuss the current status of cancer immunotherapy in children, focusing on the identification of tumor-specific antigens on pediatric solid tumors.

The functioning antigens: beyond just as the immunological targets

Antigenic peptides derived from tumor-associated antigens (TAAs) facilitate peptide cancer vaccine therapies. With the recent progress in cancer immunity research, huge amounts of antigenic peptides have already been reported. Clinical trials using such peptides are underway now all over the world. Some reports have shown the efficacy of peptide vaccine therapies. However, others ended with unfavorable results, suggesting fundamental underlying problems. One major mechanism that negates the peptide vaccine therapy is tumor escape from immunological systems caused by loss of antigens. TAAs that are used in cancer vaccine therapies may be divided into two major groups: functioning antigens and nonfunctioning antigens. A 'functioning antigen' could be defined as a TAA that is essential for tumor growth, is expressed in several kinds of malignancies and shows homogenous expression in cancerous tissues. It is not difficult to imagine that antigen loss will occur easily with non-functioning antigens as a target of cancer vaccine therapy. Thus, it is essential to use functioning antigens for successful cancer vaccine therapy. In this review, we discuss the functioning antigens and their categorization in detail.

HER-2/neu mediated down-regulation of MHC class I antigen processing prevents CTL-mediated tumor recognition upon DNA vaccination in HLA-A2 transgenic mice

To study DNA vaccination directed against human HER-2 in the HHD mouse Tg strain, we created a novel HER-2-expressing syngeneic tumor transplantation model. We found that a DNA vaccine encoding the full length HER-2 DNA protected HHD mice from HER-2(+) tumor challenge by a CTL independent mechanism. A more efficient approach to induce HLA-A2 restricted CTLs, through immunization with a multi-epitope DNA vaccine expressing the HLA-A2 restricted HER-2 369-377, 435-443 and 689-697 epitopes, resulted in high numbers of peptide specific T cells but failed to induce tumor protection. Subsequently we discovered that HER-2 transfected tumor cells down-regulated MHC class I antigen expression and exhibited a series of defects in the antigen processing pathway which impaired the capacity to produce and display MHC class I peptide-ligands to specific CTLs. Our data demonstrate that HER-2 transfection is associated with defects in the MHC class I presentation pathway, which may be the underlying mechanism behind the inability of CTLs to recognize tumors in this HLA-A2 transgenic model. As defective MHC class I presentation may be a common characteristic of HER-2 expressing tumors, vaccines targeting HER-2 should aim at inducing an integrated immune response where also CD4(+) T cells and antibodies are important components.

The impact of HER2/neu expression level on response to the E75 vaccine: from U.S. Military Cancer Institute Clinical Trials Group Study I-01 and I-02

PURPOSE

HER2/neu, a source of immunogenic peptides, is expressed in >75% of breast cancer patients. We have conducted clinical trials with the HER2/neu E75 peptide vaccine in breast cancer patients with varying levels of HER2/neu expression. Vaccine response based on HER2/neu expression level was analyzed.

EXPERIMENTAL DESIGN

Patients were stratified by HER2/neu expression. Low expressors (n = 100) were defined as HER2/neu immunohistochemistry (IHC) 1(+) to 2(+) or fluorescence in situ hybridization < 2.0. Overexpressors (n = 51) were defined as IHC 3(+) or fluorescence in situ hybridization > or = 2.0. Additional analyses were done stratifying by IHC status (0-3(+)). Standard clinocopathlogic factors, immunologic response (in vivo delayed-type hypersensitivity reactions; ex vivo human leukocyte antigen A2:immunoglobulin G dimer assay), and clinical responses (recurrence; mortality) were assessed.

RESULTS

Low-expressor (control, 44; vaccinated, 56) versus overexpressor patients (control, 22; vaccinated, 29) were assessed. Low expressors, overexpressors, and most IHC-status vaccinated groups responded immunologically. Vaccinated low-expressor patients had larger maximum immunologic responses compared with overexpressor patients (P = 0.04), and vaccinated IHC 1(+) patients had increased long-term immune response (P = 0.08). More importantly, compared with controls, low-expressor patients had a mortality reduction (P = 0.08). The largest decrease in mortality was seen in IHC 1(+) patients (P = 0.05). In addition, a subset of overexpressor patients (n = 7) received trastuzumab before vaccination, and this combination seems safe and immunologically beneficial.

CONCLUSIONS

Most patients with various levels of HER2/neu expression responded immunologically and seemed to benefit from vaccination. The low expressors, specifically IHC 1(+) patients, had more robust immunologic responses and may derive the greatest clinical benefit from the E75 vaccine.

Signal integration: a framework for understanding the efficacy of therapeutics targeting the human EGFR family

The human EGFR (HER) family is essential for communication between many epithelial cancer cell types and the tumor microenvironment. Therapeutics targeting the HER family have demonstrated clinical success in the treatment of diverse epithelial cancers. Here we propose that the success of HER family-targeted monoclonal antibodies in cancer results from their ability to interfere with HER family consolidation of signals initiated by a multitude of other receptor systems. Ligand/receptor systems that initiate these signals include cytokine receptors, chemokine receptors, TLRs, GPCRs, and integrins. We further extrapolate that improvements in cancer therapeutics targeting the HER family are likely to incorporate mechanisms that block or reverse stromal support of malignant progression by isolating the HER family from autocrine and stromal influences.

Sendai virus for cancer immunotherapy

Dendritic cells (DCs) have a crucial role to play in fighting nonself organisms and cells, including tumors. Clinically, numerous DC vaccinations have been attempted for cancer immunotherapy since the first trial, published in 1995, but with limited success. We found that Sendai virus (SeV) vector infection induces maturation of DCs and produces more powerful antitumor immunity against DCs in mouse models. We used a SeV vector as an immune booster for tumors and believe that this novel therapy, designated as "immunostimulatory virotherapy," will offer potent treatment for tumors.

Assessment of immunologic response and recurrence patterns among patients with clinical recurrence after vaccination with a preventive HER2/neu peptide vaccine: from US Military Cancer Institute Clinical Trials Group Study I-01 and I-02

BACKGROUND

E75, a HER2/neu immunogenic peptide, is expressed in breast cancer (BCa). We have performed clinical trials of E75 + GM-CSF vaccine in disease-free, node-positive and node-negative BCa patients at high recurrence risk and recurrences were noted in both control and vaccine groups.

METHODS

Among the 186 BCa patients enrolled, 177 completed the study. Patients were HLA typed; the HLA-A2(+)/A3(+) patients were vaccinated; HLA-A2(-)/A3(-) patients were followed as controls. Standard clinicopathological factors, immunologic response to the vaccine, and recurrences were collected and assessed.

RESULTS

The control group recurrence rate was 14.8 and 8.3% in the vaccinated group (P = 0.17). Comparing the 8 vaccinated recurrences (V-R) to the 88 vaccinated nonrecurrent patients (V-NR), the V-R group had higher nodal stage (> or = N2: 75 vs. 5%, P = 0.0001) and higher grade tumors (%grade 3: 88 vs. 31%, P = 0.003). The V-R group did not fail to respond immunologically as noted by equivalent dimer responses and post-DTH responses. Compared to control recurrent patients (C-R), V-R patients trended toward higher-grade tumors and hormone-receptor negativity. C-R patients had 50% bone-only recurrences, compared to V-R patients with no bone-only recurrences (P = 0.05). Lastly, V-R mortality rate was 12.5% compared with 41.7% for the C-R group (P = 0.3).

CONCLUSIONS

The vaccinated patients who recurred had more aggressive disease compared to V-NR patients. V-R patients had no difference in immune response to the vaccine either in vitro or in vivo. V-R patients, when compared to C-R patients, trended towards more aggressive disease, decreased recurrence rates, decreased mortality, and no bone-only recurrences.

Identification of the HERV-K gag antigen in prostate cancer by SEREX using autologous patient serum and its immunogenicity

The prostate cancer HERV-K gag-related NGO-Pr-54 antigen was identified by SEREX analysis using autologous patient serum. NGO-Pr-54 mRNA was observed to be faintly expressed in normal prostate and strongly expressed in a variety of cancers, including ovarian cancer (5/8), prostate cancer (6/9), and leukemia (5/14). A phage plaque assay showed that a strong reaction was constantly observed with clone ZH042 in which the 5' end of NGO-Pr-54 is deleted, suggesting that it contained the sequence coding for the protein product. A TI-35 mAb was produced using a recombinant protein (438 aa) deduced from the sequence of ZH042. Transfection of clone ZH042 into 293T cells resulted in the production of an approximately 50-kDa molecule visualized by Western blotting. Natural production of the molecule was confirmed in a SK-MEL-23 melanoma cell line. An indirect immunofluorescence assay showed that NGO-Pr-54 protein was expressed on the cell surface as well as in the cytoplasm. Cell surface expression was confirmed by flow cytometry using the TI-35 mAb. The antibody response against NGO-Pr-54 was observed in patients with bladder (5.1%), liver (4.1%), lung (3.4%), ovarian (5.6%), and prostate (4.2%) cancer, as well as with malignant melanoma (13.2%).

Cytolytic and Cytotoxic Activity of a Human Natural Killer Cell Line Genetically Modified to Specifically Recognize HER-2/neu Overexpressing Tumor Cells

NK92 cells genetically engineered to recognize the HER-2/neu oncoprotein have been previously reported to lyse HER-2/neu positive tumor cell lines through direct cell to cell contact. In the present study we have transduced NK92 cells with a chimeric receptor gene composed of the HER-/neu specific scFv (FRP5) antibody fragment, joined to the peptide CD8 hinge region and the signaling CD3 zeta chain. NK92 cells expressing this chimeric receptor (NK92.HER-2/neu/zeta) specifically recognized and lysed HER-2/neu overexpressing tumor cell lines both in vitro and in preclinical tumor models in vivo. More important we demonstrate that NK92.HER-2/neu/zeta cells constitutively secrete high levels of soluble scFv which mediate strong tumor cytostatic effects by directly binding on cell surface HER-2/neu. Our data uncover an additional mechanism through which NK92.HER-2/neu/zeta cells mediate antitumor effects and further support their use in cell based therapeutics for the treatment of HER-2/neu expressing cancers.

The E75 HER2/neu peptide vaccine

E75 (HER2/neu 369-377) is an immunogenic peptide from the HER2/neu protein which is overexpressed in many breast cancer patients. A large amount of preclinical work and a small number of Phase I trials have been completed evaluating the vaccine potential of the E75 peptide mixed with an immunoadjuvant. Our group has performed two concurrent E75 + GM-CSF Phase II trials in node-positive and node-negative disease-free breast cancer patients. These trials, totaling 186 patients, were designed to assess the ability of the E75 vaccine to prevent disease recurrence in these high risk patients. In this review article, we discuss the safety of the vaccine, the immunologic response to the peptide, and most importantly, the potential clinical benefit of the vaccine. The recurrence rate, mortality associated with recurrence, and the distribution of recurrences are presented and discussed. Additionally, the lessons learned from these trials to include optimal dosing and the need for booster inoculations are addressed. We also present data exploring possible explanations and mechanisms behind the potential clinical utility of this simple single epitope vaccine. Finally, we present some of the future directions for our Cancer Vaccine Development Program assessing multi-epitope peptide vaccines and combination immunotherapies.

Oxidation of ovarian epithelial cancer cells by hypochlorous acid enhances immunogenicity and stimulates T cells that recognize autologous primary tumor

PURPOSE

Hypochlorous acid, a product of neutrophil myeloperoxidase, is a powerful enhancer of antigen processing and presentation. In this study, we examine whether ovarian epithelial cells (SK-OV-3) exposed to hypochlorous acid can stimulate T cells from patients with ovarian epithelial cancer that recognize common tumor antigens as well as autologous tumor.

EXPERIMENTAL DESIGN

T cells from human leukocyte antigen (HLA)-A2(+) and HLA-A2(-) patients or healthy controls were stimulated with autologous dendritic cells cocultured with the generic ovarian tumor line SK-OV-3, previously exposed to hypochlorous acid.

RESULTS

Hypochlorous acid-treated SK-OV-3 cells drove expansion of CD8(+) T cells from HLA-A2(+) individuals, which recognized the HLA-A2-restricted tumor antigen epitopes of HER-2/neu (E75 and GP2) and MUC1 (M1.1 and M1.2). Up to 4.1% of the T cells were positive for the HER-2/neu KIFGSLAFL epitope using pentamer staining. Dendritic cells loaded with oxidized SK-OV-3 cells and further matured with CD40 agonistic antibody or monophosphoryl lipid A additionally induced CD4(+) class II-restricted responses. Critically, T cells stimulated with mature oxidized SK-OV-3 (but not a control oxidized melanoma cell line) directly recognized autologous tumor cells isolated from patient ascites.

CONCLUSIONS

Immunization with mature dendritic cells loaded with a generic oxidized tumor cell line stimulates a polyclonal antitumor response that recognizes autologous tumor. These findings suggest a new immunotherapeutic strategy to extend remission in ovarian cancer.

Results of the first phase I clinical trial of the novel II-key hybrid preventive HER-2/neu peptide (AE37) vaccine

PURPOSE

HER-2/neu is overexpressed in breast cancer and is the source of immunogenic peptides. CD4(+) T-helper peptides for HER-2/neu are being evaluated in vaccine trials. The addition of Ii-Key, a four-amino-acid LRMK modification, increases vaccine potency when compared with unmodified class II epitopes. We present the results of the first human phase I trial of the Ii-Key hybrid HER-2/neu peptide (AE37) vaccine in disease-free, node-negative breast cancer patients.

PATIENTS AND METHODS

The dose escalation trial included five dose groups, to determine safety and optimal dose of the hybrid peptide (100 microg, 500 microg, 1,000 microg) and granulocyte-macrophage colony-stimulating factor (GM-CSF; range, 0 to 250 microg). In the event of significant local toxicity, GM-CSF (or peptide in absence of GM-CSF) was reduced by 50%. Immunologic response was monitored by delayed-type hypersensitivity and [(3)H]thymidine proliferative assays for both the hybrid AE37 (LRMK-positive HER-2/neu:776-790) and AE36 (unmodified HER-2/neu:776-790).

RESULTS

All 15 patients completed the trial with no grade 3 to 5 toxicities. Dose reductions occurred in 47% of patients. In the second group (peptide, 500 microg; GM-CSF, 250 microg), all patients required dose reductions, prompting peptide-only inoculations in the third group. The vaccine induced dose-dependent immunologic responses in vitro and in vivo to AE37, as well as AE36.

CONCLUSION

The hybrid AE37 vaccine seems safe and well tolerated with minimal toxicity if properly dosed. AE37 is capable of eliciting HER-2/neu-specific immune responses, even without the use of an adjuvant. This trial represents the first human experience with the Ii-Key modification, and to our knowledge, AE37 is the first peptide vaccine to show potency in the absence of an immunoadjuvant.

Differential methylation of TSP50 and mTSP50 genes in different types of human tissues and mouse spermatic cells

Earlier studies identified human TSP50 as a testis-specific gene that encoded a threonine protease. Most importantly, TSP50 could be a cancer/testis antigen since there was a high frequency of reactivation in breast cancer biopsies. It was also found to be negatively regulated by the p53 gene. To further characterize this gene, we recently examined the DNA methylation patterns of the TSP50 gene promoter in normal human testis, as well as breast tissue and a testicular embryonic carcinoma cell line (HTECCL). Bisulfite genomic sequencing results demonstrated that the promoter exhibited mixed DNA methylation patterns in normal human testis, mainly non-methylation versus slight methylation, which could be attributed to the different stages spermatic cells go through during spermatogenesis. In contrast, it was methylated to a much greater extent in both breast tissue and HTECCL. To find out whether DNA methylation status was related to spermatogenesis stages, we analyzed DNA methylation patterns of the mTSP50 (the mouse ortholog of TSP50) promoter in spermatocytes and spermatozoa isolated from sexually mature mice. The results clearly demonstrated that each group of cells exhibited its preferential DNA methylation pattern that apparently was consistent with the gene expression status observed before. Taken together, our findings suggested that DNA methylation might regulate the TSP50 and mTSP50 gene expressions in different types of tissues and spermatic cells.

Combined clinical trial results of a HER2/neu (E75) vaccine for the prevention of recurrence in high-risk breast cancer patients: U.S. Military Cancer Institute Clinical Trials Group Study I-01 and I-02

PURPOSE

E75 is an immunogenic peptide from the HER2/neu protein, which is overexpressed in many breast cancer patients. We have conducted two overlapping E75 vaccine trials to prevent recurrence in node-positive (NP) and node-negative (NN) breast cancer patients.

EXPERIMENTAL DESIGN

E75 (HER2/neu 369-377) + granulocyte macrophage colony-stimulating factor was given intradermally to previously treated, disease-free NP breast cancer patients in a dose escalation safety trial and to NN breast cancer patients in a dose optimization study. Local and systemic toxicity was monitored. Immunologic responses were assessed using in vitro assays and in vivo delayed-type hypersensitivity responses. Clinical recurrences were documented.

RESULTS

One hundred and eighty-six patients were enrolled in the two studies (NP, 95; NN, 91). Human leucocyte antigen A2 (HLA-A2) and HLA-A3 patients were vaccinated (n = 101), whereas all others (n = 85) were followed prospectively as controls. Toxicities were minimal, and a dose-dependent immunologic response to the vaccine was shown. Planned primary analysis revealed a recurrence rate of 5.6% in vaccinated patients compared with 14.2% in the controls (P = 0.04) at a median of 20 months follow-up. As vaccine-specific immunity waned over time, the difference in recurrence lost significance at 26 months median follow-up (8.3% versus 14.8%); however, a significant difference in the pattern of recurrence persisted.

CONCLUSIONS

E75 is safe and effective in raising a dose-dependent HER2/neu immunity in HLA-A2 and HLA-A3 NP and NN breast cancer patients. More importantly, E75 may reduce recurrences in disease-free, conventionally treated, high-risk breast cancer patients. These findings warrant a prospective, randomized phase III trial of the E75 vaccine with periodic booster to prevent breast cancer recurrences.

About human tumor antigens to be used in immunotherapy

The choice of antigens to be used in cancer immunotherapy remains a crucial and difficult issue. This review highlights some properties of the different groups of human tumor antigens recognized by T lymphocytes, focusing on parameters that should influence this choice, such as tumor specificity and level of antigen expression.

Immunotherapy opportunities in ovarian cancer

Ovarian cancer is responsible for the majority of gynecologic cancer deaths and despite the highest standard of multimodality therapy with surgery and cytotoxic chemotherapy, long-term survival remains low. With compelling evidence that epithelial ovarian cancer is an immunogenic tumor capable of stimulating an antitumor immune response, renewed efforts to develop immune therapies to augment the efficacy of traditional therapies are underway. Current immunotherapies focus on varied modes of antitumor vaccine development, particularly with the use of dendritic cell vaccines, effective methods for adoptive T-cell transfer and combinatorial approaches with immune modulatory therapy subverting natural tolerance mechanisms or boosting effector mechanisms. Additional combinatorial approaches include the use of cytokines and/or chemotherapy with immune therapy.

Adoptive transfer of autologous, HER2-specific, cytotoxic T lymphocytes for the treatment of HER2-overexpressing breast cancer

The human epidermal growth factor receptor 2 (HER2) has been targeted as a breast cancer-associated antigen by immunotherapeutical approaches based on HER2-directed monoclonal antibodies and cancer vaccines. We describe the adoptive transfer of autologous HER2-specific T-lymphocyte clones to a patient with metastatic HER2-overexpressing breast cancer. The HLA/multimer-based monitoring of the transferred T lymphocytes revealed that the T cells rapidly disappeared from the peripheral blood. The imaging studies indicated that the T cells accumulated in the bone marrow (BM) and migrated to the liver, but were unable to penetrate into the solid metastases. The disseminated tumor cells in the BM disappeared after the completion of adoptive T-cell therapy. This study suggests the therapeutic potential for HER2-specific T cells for eliminating disseminated HER2-positive tumor cells and proposes the combination of T cell-based therapies with strategies targeting the tumor stroma to improve T-cell infiltration into solid tumors.

Immunological profiling of a panel of human ovarian cancer cell lines

PURPOSE

The efficient identification of peptide antigens recognized by ovarian cancer-specific cytotoxic T lymphocytes (CTL) requires the use of well-characterized ovarian cancer cell lines. To develop such a panel of cell lines, 11 ovarian cancer cell lines were characterized for the expression of class I and class II major histocompatibility complex (MHC)-encoded molecules, 15 tumor antigens, and immunosuppressive cytokines [transforming growth factor beta (TGF-beta) and IL-10].

METHODS

Class I MHC gene expression was determined by polymerase chain reaction (PCR), and class I and class II MHC protein expression was determined by flow cytometry. Tumor antigen expression was determined by a combination of polymerase chain reaction (PCR) and flow cytometry. Cytokine expression was determined by ELISA.

RESULTS

Each of the ovarian cancer cell lines expresses cytokeratins, although each cell line does not express the same cytokeratins. One of the lines expresses CD90, which is associated with a fibroblast lineage. Each of the cell lines expresses low to moderate amounts of class I MHC molecules, and several of them express low to moderate amounts of class II MHC molecules. Using a combination of PCR and flow cytometry, it was determined that each cell line expressed between six and thirteen of fifteen antigens tested. Little to no TGF-beta3 was produced by any of the cell lines, TGF-beta1 was produced by three of the cell lines, TGF-beta2 was produced by all of the cell lines, with four of the cell lines producing large amounts of the latent form of the molecule, and IL-10 was produced by one of the cell lines.

CONCLUSIONS

Each of the 11 ovarian cancer lines is characterized by a unique expression pattern of epithelial/fibroblast markers, MHC molecules, tumor antigens, and immunosuppressive cytokines. Knowledge of these unique expression patterns will increase the usefulness of these cell lines in identifying the antigens recognized by ovarian cancer-specific CTL.

Vascular endothelial growth factor partially inhibits the trastuzumab-mediated antibody-dependent cellular cytotoxicity of human monocytes

BACKGROUND

Vascular endothelial growth factor (VEGF) is produced by almost all cancer cells and VEGF receptor 1 (R1) (Flt-1) is abundantly expressed on human monocytes. In the present study, we investigated whether VEGF affects the antibody-dependent cell-mediated cytotoxicity (ADCC) of human monocytes mediated by trastuzumab.

METHODS

HER-2-expressing tumor cell lines (MKN-7, TE-4 and SKOV-3) were evaluated for trastuzumab-mediated ADCC of human monocytes in the presence of VEGF(165). The trastuzumab-mediated, monocyte-derived ADCC were treated with the anti-human blocking VEGF R1 or VEGF R2 mAb. VEGF-induced intracellular signaling on monocytes was quantified with ELISA kits.

RESULTS

VEGF partially inhibited the ADCC of human monocytes mediated by trastuzumab. The VEGF-induced deficiency of human monocytes for ADCC was completely recovered by the anti-human blocking VEGF R1 mAb, while the anti-VEGF R2 blocking mAb did not have any effect. Furthermore, VEGF treatment enhanced the phospho-Erk 1/2 in human monocytes.

CONCLUSION

VEGF partially inhibited the ADCC of human monocytes mediated by trastuzumab, and this inhibition was mainly mediated by VEGF R1 (Flt-1).

Quantification and phenotypic characterization of circulating tumor cells for monitoring response to a preventive HER2/neu vaccine-based immunotherapy for breast cancer: a pilot study

BACKGROUND

Ongoing cancer vaccine trials are limited by the inability of immunologic assays to monitor clinically relevant surrogates of response. Recent advances in the ability to quantify and phenotype circulating tumor cells (CTCs) in breast cancer patients may lead to a role for CTCs in monitoring response to vaccine-based immunotherapy.

METHODS

The CellSearch System (Veridex-LLC, Warren, NJ) was used to enumerate total and HER2/neu+ CTCs in 20 mL of blood from all 16 node-positive (NP) breast cancer patients active in our NP HER2/neu E75 peptide vaccine trial at the initiation of this pilot study. These patients were vaccinated with E75 (1000 microg)/GM-CSF (250 microg) monthly x 6 after completion of multimodality therapy. Mean (+/-SEM) number of CTCs and HER2/neu+ CTCs were compared in unmatched (n = 16) and matched (n = 9) prevaccination and postvaccination cases.

RESULTS

CTCs were detected in 14 of 16 (88%) patients (mean: 3.4 +/- 0.2 CTC/20 mL). After vaccination, a reduction in CTC/20 mL (prevaccination 3.9 +/- 1.5 vs postvaccination 0.7 +/- 0.4, P = .077) and HER2/neu+ CTC/20 mL (prevaccination 2.8 +/- 1.0 vs postvaccination 0.5 +/- 0.2, P = .048) was demonstrated. A significant delayed-type hypersensitivity (DTH) response suggesting that vaccination was effective in eliciting a peptide-specific immune response was confirmed (22.3 +/- 4.1 vs 3.0 +/- 2.2 [controls] mm, P < .01). All nine patients followed throughout the vaccination series also showed significant reduction in CTCs (4.8 +/- 1.5 vs 0.3 +/- 0.2, P < .01) and HER2/neu+ CTCs (3.0 +/- 0.9 vs 0.4 +/- 0.2, P = .013).

CONCLUSIONS

CTCs are readily demonstrated in posttreatment, clinically disease-free NP breast cancer patients. E75+GM-CSF vaccination appears to reduce the number of CTCs. These data suggest a potential role for this clinically validated CTC assay in assessing response to preventive vaccine-based immunotherapy, and further validation studies are underway.

Augmented HER-2 specific immunity during treatment with trastuzumab and chemotherapy

PURPOSE

Passive immunotherapy with antitumor antibodies has the potential to induce active tumor immunity via the opsonic enhancement of immunogenicity of tumor antigen. We have assessed whether immune sensitization to the HER-2/neu tumor antigen occurs during treatment with the anti-HER-2/neu monoclonal antibody trastuzumab.

EXPERIMENTAL DESIGN

Twenty-seven patients treated with trastuzumab and chemotherapy were assessed for the induction of HER-2/neu-specific immunity. Sera and peripheral blood mononuclear cells obtained before and after trastuzumab therapy were compared for the presence of anti-HER-2/neu endogenous Iglambda antibodies and HER-2/neu-specific CD4 responses by ELISA and enzyme-linked immunospot, respectively.

RESULTS

Anti-HER-2/neu antibodies were detectable in 8 of 27 (29%) patients before trastuzumab treatment and in 15 of 27 (56%) patients during trastuzumab treatment. In the overall study population, anti-HER-2/neu humoral responses significantly increased during therapy (P < 0.001) and were not associated with development of an anti-idiotypic response. In 10 evaluable individuals, 6 showed augmented HER-2/neu-specific CD4 T-cell responses during therapy. Of the 22 individuals treated for metastatic disease, those patients showing objective clinical responses exhibited more frequent (P = 0.004) and larger (P = 0.006) treatment-associated anti-HER-2/neu humoral responses.

CONCLUSION

Humoral immune sensitization occurs during treatment with chemotherapy and trastuzumab. Further studies are warranted to investigate whether augmented anti-HER-2/neu humoral and cellular immunity contributes mechanistically to clinical outcome.

A combination of chemoimmunotherapies can efficiently break self-tolerance and induce antitumor immunity in a tolerogenic murine tumor model

Her-2/neu is a well-characterized tumor-associated antigen overexpressed in human carcinomas such as breast cancer. Because Her-2/neu is a self-antigen with poor immunogenicity due to immunologic tolerance, active immunotherapy targeting Her-2/neu should incorporate methods to overcome immunologic tolerance to self-proteins. In this study, we developed a tolerogenic tumor model in mice using mouse Her-2/neu as self-antigen and investigated whether genetic vaccination with DNA plasmid and/or adenoviral vector expressing the extracellular and transmembrane domain of syngeneic mouse Her-2/neu or xenogenic human Her-2/neu could induce mouse Her-2/neu-specific CTL responses. Interestingly, adenoviral vectors expressing xenogenic human Her-2/neu (AdhHM) proved capable of breaking immune tolerance and of thereby inducing self-reactive CTL and antibodies, but not to the degree required to induce therapeutic antitumor immunity. In attempting to generate therapeutic antitumor immunity against established tumors, we adopted several approaches. Treatment with agonistic anti-glucocorticoid-induced TNFR family-related receptor (GITR) antibody plus AdhHM immunization significantly increased self-reactive CTL responses, and alpha-galactosylceramide (alphaGalCer)-loaded dendritic cells (DC) transduced with AdhHM were shown to break self-tolerance in a tolerogenic murine tumor model. Furthermore, gemcitabine treatment together with either AdhHM plus agonistic anti-GITR antibody administration or alphaGalCer-loaded DC transduced with AdhHM showed potent therapeutic antitumor immunity and perfect protection against preexisting tumors. Gemcitabine treatment attenuated the tumor-suppressive environment by eliminating CD11b(+)/Gr-1(+) myeloid-derived suppressor cells. When combined with immunotherapies, gemcitabine offers a promising strategy for the Ag-specific treatment of human cancer.