Development of Vaccines for High-Risk Ductal Carcinoma In situ of the Breast: Figure 1

Transcriptomic Properties of HER2+ Ductal Carcinoma In Situ of the Breast Associate with Absence of Immune Cells

The identification of transcriptomic alterations of HER2+ ductal carcinoma in situ (DCIS) that are associated with the density of tumor-infiltrating lymphocytes (TILs) could contribute to optimizing choices regarding the potential benefit of immune therapy. We compared the gene expression profile of TIL-poor HER2+ DCIS to that of TIL-rich HER2+ DCIS. Tumor cells from 11 TIL-rich and 12 TIL-poor DCIS cases were micro-dissected for RNA isolation. The Ion AmpliSeq Transcriptome Human Gene Expression Kit was used for RNA sequencing. After normalization, a Mann-Whitney rank sum test was used to analyze differentially expressed genes between TIL-poor and TIL-rich HER2+ DCIS. Whole tissue sections were immunostained for validation of protein expression. We identified a 29-gene expression profile that differentiated TIL-rich from TIL-poor HER2+ DCIS. These genes included CCND3, DUSP10 and RAP1GAP, which were previously described in breast cancer and cancer immunity and were more highly expressed in TIL-rich DCIS. Using immunohistochemistry, we found lower protein expression in TIL-rich DCIS. This suggests regulation of protein expression at the posttranslational level. We identified a gene expression profile of HER2+ DCIS cells that was associated with the density of TILs. This classifier may guide towards more rationalized choices regarding immune-mediated therapy in HER2+ DCIS, such as targeted vaccine therapy.

Immunotherapy in breast cancer: Current status and future directions

Breast cancer, one of the leading causes of death in women in the United States, challenges therapeutic success in patients due to tumor heterogeneity, treatment resistance, metastasis and disease recurrence. Knowledge of immune system involvement in normal breast development and breast cancer has led to extensive research into the immune landscape of breast cancer and multiple immunotherapy clinical trials in breast cancer patients. However, poor immunogenicity and T-cell infiltration along with heightened immunosuppression in the tumor microenvironment have been identified as potential challenges to the success of immunotherapy in breast cancer. Oncodrivers, owing to their enhanced expression and stimulation of tumor cell proliferation and survival, present an excellent choice for targeted immunotherapy development in breast cancer. Loss of anti-tumor immune response specific to oncodrivers has been reported in breast cancer patients as well. Dendritic cell vaccines have been tested for their efficacy in generating anti-tumor T-cell response against specific tumor-associated antigens and oncodrivers and have shown improved survival outcome in patients. Here, we review the current status of immunotherapy in breast cancer, focusing on dendritic cell vaccines and their therapeutic application in breast cancer. We further discuss future directions of breast cancer immunotherapy and potential combination strategies involving dendritic cell vaccines and existing chemotherapeutics for improved efficacy and better survival outcome in breast cancer.

Tumor-infiltrating lymphocytes and ductal carcinoma in situ of the breast: friends or foes?

In the past three decades, the detection rate of ductal carcinoma in situ of the breast has dramatically increased due to breast screening programs. As a consequence, about 20% of all breast cancer cases are detected in this early in situ stage. Some ductal carcinoma in situ cases will progress to invasive breast cancer, while other cases are likely to have an indolent biological behavior. The presence of tumor-infiltrating lymphocytes is seen as a promising prognostic and predictive marker in invasive breast cancer, mainly in HER2-positive and triple-negative subtypes. Here, we summarize the current understanding regarding immune infiltrates in invasive breast cancer and highlight recent observations regarding the presence and potential clinical significance of such immune infiltrates in patients with ductal carcinoma in situ. The presence of tumor-infiltrating lymphocytes, their numbers, composition, and potential relationship with genomic status will be discussed. Finally, we propose that a combination of genetic and immune markers may better stratify ductal carcinoma in situ subtypes with respect to tumor evolution.

Tumor Immuno-Environment in Cancer Progression and Therapy

The approvals of Provenge (Sipuleucel-T), Ipilimumab (Yervoy/anti-CTLA-4) and blockers of the PD-1 - PD-L1/PD-L2 pathway, such as nivolumab (Opdivo), pembrolizumab (Keytruda), or atezolizumab (Tecentriq), have established immunotherapy as a key component of comprehensive cancer care. Further, murine mechanistic studies and studies in immunocompromised patients have documented the critical role of immunity in effectiveness of radio- and chemotherapy. However, in addition to the ability of the immune system to control cancer progression, it can also promote tumor growth, via regulatory T cells (Tregs), myeloid-derived dendritic cells (MDSCs) and tumor associated macrophages (TAM), which can enhance survival of cancer cells directly or via the regulation of the tumor stroma.An increasing body of evidence supports a central role for the tumor microenvironment (TME) and the interactions between tumor stroma, infiltrating immune cells and cancer cells during the induction and effector phase of anti-cancer immunity, and the overall effectiveness of immunotherapy and other forms of cancer treatment. In this chapter, we discuss the roles of key TME components during tumor progression, metastatic process and cancer therapy-induced tumor regression, as well as opportunities for their modulation to enhance the overall therapeutic benefit.

Dendritic Cell Vaccination Enhances Immune Responses and Induces Regression of HER2pos DCIS Independent of Route: Results of Randomized Selection Design Trial

Purpose: Vaccination with HER2 peptide-pulsed DC1s stimulates a HER2-specific T-cell response. This randomized trial aimed to establish safety and evaluate immune and clinical responses to vaccination via intralesional (IL), intranodal (IN), or both intralesional and intranodal (ILN) injection.Experimental Design: Fifty-four HER2^pos patients [42 pure ductal carcinoma in situ (DCIS), 12 early invasive breast cancer (IBC)] were enrolled in a neoadjuvant HER2 peptide-pulsed DC1 vaccine trial. Patients were randomized to IL (n = 19), IN (n = 19), or ILN (n = 16) injection. Immune responses were measured in peripheral blood and sentinel lymph nodes by ELISPOT or in vitro sensitization assay. Pathologic response was assessed in resected surgical specimens.Results: Vaccination by all injection routes was well tolerated. There was no significant difference in immune response rates by vaccination route (IL 84.2% vs. IN 89.5% vs. ILN 66.7%; P = 0.30). The pathologic complete response (pCR) rate was higher in DCIS patients compared with IBC patients (28.6% vs. 8.3%). DCIS patients who achieved pCR (n = 12) and who did not achieve pCR (n = 30) had similar peripheral blood anti-HER2 immune responses. All patients who achieved pCR had an anti-HER2 CD4 immune response in the sentinel lymph node, and the quantified response was higher by response repertoire (P = 0.03) and cumulative response (P = 0.04).Conclusions: Anti-HER2 DC1 vaccination is a safe and immunogenic treatment to induce tumor-specific T-cell responses in HER2^pos patients; immune and clinical responses were similar independent of vaccination route. The immune response in the sentinel lymph nodes, rather than in the peripheral blood, may serve as an endpoint more reflective of antitumor activity. Clin Cancer Res; 23(12); 2961-71. ©2016 AACR.

Addition of anti-estrogen therapy to anti-HER2 dendritic cell vaccination improves regional nodal immune response and pathologic complete response rate in patients with ERpos/HER2pos early breast cancer

HER2-directed therapies are less effective in patients with ERpos compared to ERneg breast cancer, possibly reflecting bidirectional activation between HER2 and estrogen signaling pathways. We investigated dual blockade using anti-HER2 vaccination and anti-estrogen therapy in HER2pos/ERpos early breast cancer patients. In pre-clinical studies of HER2pos breast cancer cell lines, ERpos cells were partially resistant to CD4+ Th1 cytokine-induced metabolic suppression compared with ERneg cells. The addition of anti-estrogen treatment significantly enhanced cytokine sensitivity in ERpos, but not ERneg, cell lines. In two pooled phase-I clinical trials, patients with HER2pos early breast cancer were treated with neoadjuvant anti-HER2 dendritic cell vaccination; HER2pos/ERpos patients were treated with or without concurrent anti-estrogen therapy. The anti-HER2 Th1 immune response measured in the peripheral blood significantly increased following vaccination, but was similar across the three treatment groups (ERneg vaccination alone, ERpos vaccination alone, ERpos vaccination + anti-estrogen therapy). In the sentinel lymph nodes, however, the anti-HER2 Th1 immune response was significantly higher in ERpos patients treated with combination anti-HER2 vaccination plus anti-estrogen therapy compared to those treated with anti-HER2 vaccination alone. Similar rates of pathologic complete response (pCR) were observed in vaccinated ERneg patients and vaccinated ERpos patients treated with concurrent anti-estrogen therapy (31.4% vs. 28.6%); both were significantly higher than the pCR rate in vaccinated ERpos patients who did not receive anti-estrogen therapy (4.0%, p = 0.03). Since pCR portends long-term favorable outcomes, these results support additional clinical investigations using HER2-directed vaccines in combination with anti-estrogen treatments for ERpos/HER2pos DCIS and invasive breast cancer.

The immune microenvironment of breast ductal carcinoma in situ

The host immune response has a key role in breast cancer progression and response to therapy. However, relative to primary invasive breast cancers, the immune milieu of breast ductal carcinoma in situ (DCIS) is less understood. Here, we profile tumor infiltrating lymphocytes and expression of the immune checkpoint ligand programmed death ligand 1 (PD-L1) in 27 cases of DCIS with known estrogen receptor (ER), progesterone receptor, and human epidermal growth factor 2 (HER-2) expression using tissue microarrays. Twenty-four cases were pure DCIS and three had associated invasive ductal carcinoma. Tumors were stained by immunohistochemistry for PD-L1, as well as the lymphocyte markers CD3, CD4, CD8, FoxP3, and CD20. The expression of PD-L1 by DCIS carcinoma cells and tumor infiltrating lymphocytes was determined, and the average tumor infiltrating lymphocytes per high power field were manually scored. None of the DCIS cells expressed PD-L1, but 81% of DCIS lesions contained PD-L1+ tumor infiltrating lymphocytes. DCIS with moderate-diffuse tumor infiltrating lymphocytes was more likely to have PD-L1+ tumor infiltrating lymphocytes (P=0.004). Tumor infiltrating lymphocytes with high levels of PD-L1 expression (>50% cells) were seen only in triple-negative DCIS (P=0.0008), and PD-L1-tumor infiltrating lymphocytes were seen only in ER+/HER-2-DCIS (P=0.12). The presence of PD-L1+ tumor infiltrating lymphocytes was associated with a younger mean patient age (P=0.01). Further characterization of the DCIS immune microenvironment may identify useful targets for immune-based therapy and breast cancer prevention.

Rationale for a Multimodality Strategy to Enhance the Efficacy of Dendritic Cell-Based Cancer Immunotherapy

Dendritic cells (DC), master antigen-presenting cells that orchestrate interactions between the adaptive and innate immune arms, are increasingly utilized in cancer immunotherapy. Despite remarkable progress in our understanding of DC immunobiology, as well as several encouraging clinical applications – such as DC-based sipuleucel-T for metastatic castration-resistant prostate cancer – clinically effective DC-based immunotherapy as monotherapy for a majority of tumors remains a distant goal. The complex interplay between diverse molecular and immune processes that govern resistance to DC-based vaccination compels a multimodality approach, encompassing a growing arsenal of antitumor agents which target these distinct processes and synergistically enhance DC function. These include antibody-based targeted molecular therapies, immune checkpoint inhibitors, therapies that inhibit immunosuppressive cellular elements, conventional cytotoxic modalities, and immune potentiating adjuvants. It is likely that in the emerging era of “precision” cancer therapeutics, tangible clinical benefits will only be realized with a multifaceted – and personalized – approach combining DC-based vaccination with adjunctive strategies.

Human epidermal growth factor receptor 2-positive microinvasive breast carcinoma with a highly aggressive course: a case report

Background

Microinvasive ductal carcinoma in situ of the breast is a rare entity defined as ductal carcinoma in situ with invasive foci measuring no more than 1 mm. In general, the outcome is excellent, similar to ductal carcinoma in situ. We report a patient with breast ductal carcinoma in situ with microinvasion who died eight months after diagnosis due to progression of the disease – liver metastases. This is the first report in the literature of such an aggressive course.

Case presentation

A 47-year-old Caucasian woman presented with mammographic-detected suspicious microcalcinations in an area of 8.6 x 6 cm. A radical mastectomy with a sentinel lymph node biopsy and immediate breast reconstruction with implant was performed. A histopathological report showed a massive high grade ductal carcinoma in situ, of the solid and comedo type. In one quadrant, some foci of microinvasions of less than 1 mm were present. Tumour margins were free. Isolated tumour cells were found in the sentinel lymph node. Hormone receptors were negative and human epidermal growth factor receptor-2 status was not performed. The patient received no adjuvant systemic therapy. Eight months after the surgery, she died from hepatic failure without known breast cancer progression before. An autopsy revealed diffuse liver metastases with human epidermal growth factor receptor 2-positive, hormone receptor negative breast cancer. Dissemination to other organs was not proven.

Conclusion

Our patient is a rare case of ductal carcinoma in situ with microinvasion that developed distant metastases very early. In case of multiple foci of microinvasion, besides radical local treatment we suggest considering adjuvant systemic treatment based on biological characteristics since tumour size alone does not predict the prognosis well.

Global Inhibition of DC Priming Capacity in the Spleen of Self-Antigen Vaccinated Mice Requires IL-10

Dendritic cells (DC) in the spleen are highly activated following intravenous vaccination with a foreign-antigen, promoting expansion of effector T cells, but remain phenotypically and functionally immature after vaccination with a self-antigen. Up-regulation or suppression of expression of a cohort of pancreatic enzymes 24–72 h post-vaccination can be used as a biomarker of stimulatory versus tolerogenic DC, respectively. Here we show, using MUC1 transgenic mice and a vaccine based on the MUC1 peptide, which these mice perceive as a self-antigen, that the difference in enzyme expression that predicts whether DC will promote immune response or immune tolerance is seen as early as 4–8 h following vaccination. We also identify early production of IL-10 as a predominant factor that both correlates with this early-time point and controls DC function. Pre-treating mice with an antibody against the IL-10 receptor prior to vaccination results in DC that up-regulate CD40, CD80, and CD86 and promote stronger IFNγ+ T cell responses. This study suggests that transient inhibition of IL-10 prior to vaccination could improve responses to cancer vaccines that utilize self-tumor antigens.

A multiantigen vaccine targeting neu, IGFBP-2, and IGF-IR prevents tumor progression in mice with preinvasive breast disease

A multiantigen multipeptide vaccine, targeting proteins expressed in preinvasive breast lesions, can stimulate type I CD4(+) T cells which have been shown to be deficient in both patients with breast cancer and mice that develop mammary tumors. Transgenic mice (TgMMTV-neu) were immunized with a multiantigen peptide vaccine specific for neu, insulin-like growth factor-binding protein 2 and insulin-like growth factor receptor-I at a time when some of the animals already had preinvasive lesions (18 weeks of age). Although immunization with each individual antigen was partially effective in inhibiting tumor growth, immunization with the multiantigen vaccine was highly effective, blocking development of palpable lesions in 65% of mice and slowing tumor growth in the infrequent palpable tumors, which did arise. Protection was mediated by CD4(+) T cells, and the few slow-growing tumors that did develop demonstrated a significant increase in intratumoral CD8(+) T cells as compared with controls (P = 0.0007). We also combined the vaccine with agents that were, by themselves, partially effective inhibitors of tumor progression in this model; lapatinib and the RXR agonist bexarotene. Although the combination of lapatinib and vaccination performed similarly to vaccination alone (P = 0.735), bexarotene and vaccination significantly enhanced disease-free survival (P < 0.0001), and approximately 90% of the mice showed no pathologic evidence of carcinomas at one year. The vaccine also demonstrated significant clinical efficacy in an additional transgenic model of breast cancer (TgC3(I)-Tag). Chemoimmunoprevention combinations may be an effective approach to breast cancer prevention even when the vaccine is administered in the presence of subclinical disease.

Identification of putative immunologic targets for colon cancer prevention based on conserved gene upregulation from preinvasive to malignant lesions

The length of time required for preinvasive adenoma to progress to carcinoma, the immunogenicity of colorectal cancer (CRC), and the identification of high-risk populations make development and testing of a prophylactic vaccine for the prevention of CRC possible. We hypothesized that genes upregulated in adenoma relative to normal tissue, which maintained increased expression in CRC, would encode proteins suitable as putative targets for immunoprevention. We evaluated existing adenoma and CRC microarray datasets and identified 160 genes that were ≥2-fold upregulated in both adenoma and CRC relative to normal colon tissue. We further identified 23 genes that showed protein overexpression in colon adenoma and CRC based on literature review. Silencing the most highly upregulated genes, CDH3, CLDN1, KRT23, and MMP7, in adenoma and CRC cell lines resulted in a significant decrease in viability (P < 0.0001) and proliferation (P < 0.0001) as compared to controls and an increase in cellular apoptosis (P < 0.05 for CDH3, KRT23). Results were duplicated across cell lines representing microsatellite instability, CpG island methylator, and chromosomal instability phenotypes, suggesting immunologic elimination of cells expressing these proteins could impact the progression of all CRC phenotypes. To determine whether these proteins were immunogens, we interrogated sera from early stage CRC patients and controls and found significantly elevated CDH3 (P = 0.006), KRT23 (P = 0.0007), and MMP7 (P < 0.0001) serum immunoglobulin G in cases as compared to controls. These data show a high throughput approach to the identification of biologically relevant putative immunologic targets for CRC and identified three candidates suitable for vaccine development.

Dendritic cell-based vaccines: barriers and opportunities

Dendritic cells (DCs) have several characteristics that make them an ideal vehicle for tumor vaccines, and with the first US FDA-approved DC-based vaccine in use for the treatment of prostate cancer, this technology has become a promising new therapeutic option. However, DC-based vaccines face several barriers that have limited their effectiveness in clinical trials. A major barrier includes the activation state of the DC. Both DC lineage and maturation signals must be selected to optimize the antitumor response and overcome immunosuppressive effects of the tumor microenvironment. Another barrier to successful vaccination is the selection of target antigens that will activate both CD8(+) and CD4(+) T cells in a potent, immune-specific manner. Finally, tumor progression and immune dysfunction limit vaccine efficacy in advanced stages, which may make DC-based vaccines more efficacious in treating early-stage disease. This review underscores the scientific basis and advances in the development of DC-based vaccines, focuses on current barriers to success and highlights new research opportunities to address these obstacles.

Vaccination for the prevention and treatment of breast cancer with special focus on Her-2/neu peptide vaccines

Immunologic interventions in a subset of breast cancer patients represent a well-established therapeutic approach reflecting individualized treatment modalities. Thus, the therapeutic administration of monoclonal antibodies targeting tumor-associated antigens (TAA), such as Her-2/neu, represents a milestone in cancer treatment. However, passive antibody administration suffers from several drawbacks, including frequency and long duration of treatment. These undesirables may be avoidable in an approach based on generating active immune responses against these same targets. Only recently has the significance of tumors in relation to their microenvironments been understood as essential for creating an effective cancer vaccine. In particular, the immune system plays an important role in suppressing or promoting tumor formation and growth. Therefore, activation of appropriate triggers (such as induction of Th1 cells, CD8+ T cells, and suppression of regulatory cells in combination with generation of antibodies with anti-tumor activity) is a desirable goal. Current vaccination approaches have concentrated on therapeutic vaccines using certain TAA. Many cancer antigens, including breast cancer antigens, have been described and also given priority ranking for use as vaccine antigens by the US National Cancer Institute. One of the TAA antigens which has been thoroughly examined in numerous trials is Her-2/neu. This review will discuss delivery systems for this antigen with special focus on T and B cell peptide vaccines. Attention will be given to their advantages and limitations, as well as the use of certain adjuvants to improve anti-cancer responses.

High prevalence of HER-2/neu overexpression in female breast cancer among an Iraqi population exposed to depleted uranium

Background

This study aimed to estimate the rate of HER-2/neu (c-erbB2) immunohistochemical overexpression in different histological types of breast cancer found in the middle Euphrates region of Iraq, a region that was exposed to high levels of depleted uranium. HER-2/neu (c-erbB2) overexpression was correlated with common clinicopathological parameters such as age, grade, stage, tumor size and lymph node involvement to determine if any particular biomarker for exposure to depleted uranium could be found in the tumor samples from this region.

Materials and Methods

The present investigation was performed over a period starting from September 2007 to June 2008. Formalin-fixed, paraffin-embedded blocks from 90 patients with breast cancer were included in this study. A group of 25 patients with benign breast lesions (fibroadenoma) was included as a comparative group, and 20 breast tissue sections were used as controls. Labeled streptavidin-biotin (LSAB) complex method was employed for immunohistochemical detection of HER-2/neu.

Results

HER-2/neu immuno-expression was positive in 67.8% of breast cancer, while it was negative in all benign breast lesions (fibroadenoma) (P < 0.05). HER-2/neu immunostaining was significantly associated with histological type and recurrence of breast cancer (P < 0.05). It was positively correlated with tumor grade, but this finding was not significant (P > 0.05).

Conclusion

Based upon the findings of this study, it can be concluded that HER-2/neu overexpression plays an important role in the pathogenesis of breast cancer and is associated with a worse prognosis. The findings indicate that in regions exposed to high levels of depleted uranium, HER-2/neu overexpression is high, but its correlation with age, grade, stage, tumor size, and lymph node involvement is similar to studies that have been conducted on populations not exposed to depleted uranium.

Immune therapy for breast cancer in 2010-hype or hope?

The identification of numerous breast cancer antigens has generated increasing enthusiasm for the application of immune-based therapies in breast malignancies. Although the use of monoclonal antibodies has revolutionized the "targeted therapy" of breast cancer, and the immunomodulatory effects of bisphosphonates continue to be evaluated, few studies to date have demonstrated widespread utility for other forms of immunotherapy. The present review assesses modern research and explores whether the hopes for immunotherapy can overcome the hype.

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.

Progress in the development of a therapeutic vaccine for breast cancer

Various human malignancies are immunogenic and recent cancer vaccine trials have demonstrated potential survival benefit. Breast cancer is immunogenic and there are several tumor associated antigens for which breast cancer vaccines have been developed. Breast cancer vaccines are designed to stimulate the immune response at various steps in the native antigen processing pathway for immunosurveillance. Human epidermal growth factor receptor 2 (HER-2/neu), mucin 1 (MUC-1), and human telomerase reverse transcriptase (hTERT) are some of the most studied antigens actively being targeted for vaccination in breast cancer patients. These vaccines are designed to elicit cytotoxic and/or helper T cell responses. Over the last several years, there has been reported progress in human clinical trials for these antigens. Cancer vaccines have repeatedly been shown to be safe with production of minimal toxicity. Recent clinical advances in the development of cancer vaccines demonstrate the potential clinical benefit that cancer vaccines hold.

Reengineering dendritic cell-based anti-cancer vaccines

Despite initial enthusiasm, dendritic cell (DC)-based anti-cancer vaccines have yet to live up to their promise as one of the best hopes for generating effective anti-tumor immunity. One of the principal reasons for the generally disappointing results achieved thus far could be that the full potential of DCs has not been effectively exploited. Here, we argue that dramatic improvements in vaccine efficacy will probably require a careful re-evaluation of current vaccine design. The formulation of new strategies must take into account the natural history of DCs, particularly their role in helping the immune system deal with infection. Equally critical is the emerging importance of soluble factors, notably interleukin-12, in modulating the quality of immune responses. Vaccines should also be designed to recruit helper T cells and antibody-producing B cells rather than simply cytotoxic T lymphocytes. Finally, the judicious selection of tumor, target antigen, and disease stage best suited for treatment should serve as the foundation of trial designs. Our discussion addresses a recent clinical vaccine trial to treat early breast cancer, where many elements of this new strategy were put into practice.

Her-2 DNA versus cell vaccine: immunogenicity and anti-tumor activity

Direct comparison and ranking of vaccine formulations in pre-clinical studies will expedite the identification of cancer vaccines for clinical trials. Two human ErbB-2 (Her-2) vaccines, naked DNA and whole cell vaccine, were tested side-by-side in wild type and Her-2 transgenic mice. Both vaccines can induce humoral and cellular immunity to the entire repertoire of Her-2 epitopes. Mice were electro-vaccinated i.m. with a mixture of pGM-CSF and pE2TM, the latter encodes Her-2 extracellular and transmembrane domains. Alternatively, mice were injected i.p. with human ovarian cancer SKOV3 cells that have amplified Her-2. In wild type mice, comparable levels of Her-2 antibodies (Ab) were induced by these two vaccines. However, T cell immunity and protection against Her-2(+) tumors were superior in DNA vaccinated mice. In BALB Her-2 transgenic (Tg) mice, which were tolerant to Her-2, DNA and cell vaccines were administered after regulatory T cells (Treg) were removed by anti-CD25 mAb. Again, comparable levels of Her-2 Ab were induced, but DNA vaccines rendered greater anti-tumor activity. In B6xDR3 Her-2 Tg mice that expressed the autoimmune prone HLA-DR3 allele, higher levels of Her-2 Ab were induced by SKOV3 cell than by Her-2 DNA. But anti-tumor activity was still more profound in DNA vaccinated mice. Therefore, Her-2 DNA vaccine induced greater anti-tumor immunity than cell vaccine, whether mice were tolerant to Her-2 or susceptible to autoimmunity. Through such side-by-side comparisons in appropriate pre-clinical test systems, the more effective vaccine formulations will emerge as candidates for clinical trials.