The use of autoantibodies for the early detection of breast cancer has generated much interest as antibodies can be readily assayed in serum when antigen levels are low. Ideally, diagnostic autoantibodies would be identified in individuals who harbored pre-invasive disease/high risk lesions leading to malignancy. Prospectively collected human serum samples from these individuals are rare and not often available for biomarker discovery. We questioned whether transgenic animals could be used to identify cancer-associated autoantibodies present at the earliest stages of the malignant transformation of breast cancer.

Background The ability of T-cells to traffic to and penetrate tumors impacts the clinical efficacy of T-cell therapy therefore methods to track transferred T-cells in vivo are needed. In this preliminary report, we evaluated the use of concurrent SPECT/PET-CT imaging to monitor the egress of HER-2/neu specific T-cells in a breast cancer patient with extensive bone-only metastatic disease. Findings Indium (In-111) labeled T-cells demonstrated similar or greater viability than unlabeled T-cells at either a low or high dose of In-111 over a 24-h incubation period in vitro. The function of labeled or unlabeled T-cells was not significantly different (p > 0.05) at either dose. T-cells trafficked to all sites of metastatic disease and infiltrated the tumor as assessed by SPECT imaging. In-111 uptake at 24 h after infusion varied from 3.8 (right proximal humerus) to 6.3 (right sacrum) background corrected counts per pixel and remained elevated at 48 h. Concurrent PET-CT imaging demonstrated a fluorodeoxyglucose flare, measured by increase in tumor site uptake as high as 32 % and at most sites of disease at 48 h. This flare was associated with focal pain after T-cell infusion at metastatic sites. The patient had stable disease for 18 months after completion of T-cell therapy. Conclusion Concurrent SPECT/PET-CT imaging, over a 48-h period after T-cell infusion, provided evidence of T-cell homing to all disease sites as well as a tumor metabolism flare response. This technique may be useful for monitoring T-cell trafficking after autologous as well as chimeric antigen receptor T-cell infusion. Trial Registraion Trial registered at ClinicalTrials.gov registration number NCT00791037, registered 13 November 2008.

Purpose: High levels of type I T cells are needed for tumor eradication. We evaluated whether the HER2-specific vaccine–primed T cells are readily expanded ex vivo to achieve levels needed for therapeutic infusion. Patients and Methods: Phase I/II nonrandomized trial of escalating doses of ex vivo–expanded HER2-specific T cells after in vivo priming with a multiple peptide–based HER2 intracellular domain (ICD) vaccine. Vaccines were given weekly for a total of three immunizations. Two weeks after the third vaccine, patients underwent leukapheresis for T-cell expansion, then received three escalating cell doses over 7- to 10-day intervals. Booster vaccines were administered after the T-cell infusions. The primary objective was safety. The secondary objectives included extent and persistence of HER2-specific T cells, development of epitope spreading, and clinical response. Patients received a CT scan prior to enrollment and 1 month after the last T-cell infusion. Results: Nineteen patients received T-cell infusions. Treatment was well tolerated. One month after the last T-cell infusion, 82% of patients had significantly augmented T cells to at least one of the immunizing epitopes and 81% of patients demonstrated enhanced intramolecular epitope spreading compared with baseline (P < 0.05). There were no complete responses, one partial response (6%), and eight patients with stable disease (47%), for a disease control rate of 53%. The median survival for those with progressive disease was 20.5 months and for responders (PR+SD) was 45.0 months. Conclusions: Adoptive transfer of HER2 vaccine–primed T cells was feasible, was associated with minimal toxicity, and resulted in an increased overall survival in responding patients. See related commentary by Crosby et al., p. 3256

Background/Objectives: Regulatory T cells (Treg) suppress immunity in the tumor microenvironment, are linked to poor prognosis across breast cancer subtypes, and suppress the cytolytic function of cytotoxic CD8+ T cells. Denileukin diftitox, a diphtheria toxin (DT)/IL-2 fusion protein, targets and depletes Tregs. This Phase II study aimed to assess the safety of denileukin diftitox and its effect on Tregs and tumor growth in patients with advanced breast cancer. Methods: This single-arm Phase II study of denileukin diftitox enrolled patients with refractory stage IV breast cancer. Patients received denileukin diftitox 18 mcg/kg/day IV for Days 1–5 every 21 days for up to six cycles. Toxicity was assessed using CTCAE v3.0 and tumor response was evaluated per RECIST criteria. Blood samples were collected to analyze Tregs by flow cytometry and anti-DT antibodies by ELISA. Results: Fifteen patients with stage IV breast cancer were enrolled. Four patients completed all planned denileukin diftitox infusions and achieved stable disease (27%, 95% CI [0.08, 0.55]). Two patients (13%) discontinued due to toxicity, and nine patients (60%) discontinued due to progressive disease. Eleven patients experienced at least one grade 3 or 4 adverse event. Although there was a general reduction in peripheral blood Tregs, the difference in CD4+CD25+FOXP3+ Tregs levels post-treatment was not statistically significant (p = 0.10). Six patients (40%) achieved $\ge$25% reductions in Tregs. A significant increase in anti-DT IgG antibodies was observed post-treatment (p < 0.005). Conclusions: Denileukin diftitox demonstrated moderate toxicity in this advanced breast cancer cohort. Denileukin diftitox modulated regulatory T cells. However, the majority of patients experienced disease progression in the study.

Background: Breast cancer stem cells (CSCs), particularly those enriched in triple-negative breast cancer (TNBC), are key contributors to tumor recurrence, metastasis, and resistance to therapy. CSCs often undergo epithelial-to-mesenchymal transformation (EMT), enhancing their invasiveness. Immune-based strategies that selectively target CSC/EMT antigens offer a promising therapeutic approach. Methods: Twelve candidate CSC/EMT-associated proteins were identified through a systematic literature review. Human serum samples were assessed for antigen-specific IgG using ELISA. Th1/Th2 cytokine profiles, in response to predicted MHC II epitopes, were measured by ELISPOT in PBMCs. Epitope immunogenicity and tumor inhibition were evaluated in murine models, using either TNBC or luminal B syngeneic breast cancer cell lines. Results: Six of the candidate proteins (SOX2, YB1, FOXQ1, MDM2, CDH3, CD105) elicited antigen-specific IgG in human serum. Th1-selective epitopes, defined by high Th1/Th2 ratios, were identified for five of these proteins. Immunization of mice with peptide pools derived from CD105, CDH3, MDM2, SOX2, and YB1 induced significant antigen-specific IFN-γ responses. Tumor growth was significantly inhibited in the vaccinated mice across both the TNBC and luminal B breast cancer models, with mean tumor volume reductions ranging from 61% to 70%. Conclusions: CSC/EMT-associated antigens are immunogenic in humans and can be targeted using Th1-selective epitope-based vaccines. Immunization with these epitopes effectively inhibits tumor growth in multiple murine models of breast cancer. These findings support further clinical evaluation of CSC/EMT-targeted vaccines, especially for high-risk or advanced-stage breast cancer patients.