T-Cell Immunity to the Folate Receptor Alpha Is Prevalent in Women With Breast or Ovarian Cancer

Purpose Studies have demonstrated that the generation of immunity to tumor antigens is associated with improved prognosis for many cancers. A candidate antigen is the folate receptor alpha (FRα), which is overexpressed in breast and ovarian cancers. Our goal in this study was to attain a better understanding of the extent of endogenous FRα immunity. Methods Using a CD4+ T cell epitope prediction algorithm, we predicted promiscuous epitopes of FRα, and tested for immunity in 30 breast (n = 17) or ovarian (n = 13) cancer patients and 18 healthy donors using enzyme-linked immunospot analysis. Results Fourteen peptides were predicted, seven each from the carboxy- and amino-terminus halves of the protein. More than 70% of patients demonstrated immunity to at least one FRα peptide. Patients responded to an average of 3 ± 0.5 peptides, whereas healthy donors responded to 1 ± 0.4 peptides (P = .004). Five peptides were recognized by more than 25% of patients. Responses to three peptides were higher (P < .05) in patients than in healthy donors, suggesting augmented immunity. Compared with healthy individuals, patients developed higher immunity to the amino-terminus half of the receptor (P = .03). There was no difference between each group in the responses to nonspecific (P = .2) and viral stimuli (P = .5). Lastly, patients demonstrated elevated levels of FRα antibodies consistent with a coordinated immune response. Conclusion These findings demonstrate that the FRα is a target of the immune system in breast and ovarian cancer patients. Understanding which antigens are targeted by the immune system may be important for prognosis or immune-based therapies.

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Patients with breast and ovarian cancer generate immune responses to the folate receptor alpha

Journal of Clinical Oncology ◽

10.1200/jco.2006.24.18_suppl.20043 ◽

2006 ◽

Vol 24 (18_suppl) ◽

pp. 20043-20043

Author(s):

K. L. Knutson ◽

K. R. Kalli ◽

C. J. Krco ◽

K. Goodman ◽

L. E. Kelemen ◽

...

Keyword(s):

Ovarian Cancer ◽

Immune System ◽

T Cell ◽

Immune Responses ◽

Folate Receptor ◽

T Cell Immunity ◽

Amino Terminus ◽

Breast And Ovarian Cancer ◽

Cell Immunity ◽

Healthy Donors

20043 Background: Studies have demonstrated that the generation of endogenous immunity to specific tumor antigens is associated with improved prognosis for many cancers. Thus, there has been increased efforts to identify tumor-associated antigens to which there is immunity, as these may be tumor rejection antigens. A candidate antigen is the folate receptor alpha (FRα) which is overexpressed in malignancies, especially breast and ovarian cancer. Prior studies involving ovarian and breast cancer patients have demonstrated the presence of FRα-specific cytotoxic T cells in the tumor-associated lymphocyte population. Methods: Using the RANKPEP CD4 T cell epitope prediction algorithm, we predicted promiscuous immunogenic regions of FRα, and tested for immunity in 30 breast or ovarian cancer patients and 18 healthy volunteer donors in order to attain a better understanding of the levels and extent of the endogenous FRα immune response. Immunity was examined using IFN-γ ELIspot analysis and IgG ELISAs. Results: Fourteen peptides were predicted as potential epitopes to which T cells may respond, seven each from the carboxy- and amino-terminus halves of the protein. Greater than 70% of patients demonstrated T cell immunity to at least one of the fourteen peptides. Patients responded to an average of 3 ± 0.7 peptides while healthy donors responded to only 1 ± 0.5 peptides (p = 0.02). Five peptides were recognized by >25% of patients. Responses to three of these peptides were higher (p > 0.05) in the patients than in healthy donors, suggesting that patients generated immunity upon cancer development. Compared to healthy individuals, patients developed higher immunity to the amino-terminus half of the receptor, suggesting natural epitope spreading (p = 0.03). There was no difference between patients and healthy donors in the immune responses to either non-specific stimuli (p = 0.2) or viral peptides (p = 0.5). Patients had detectable FRα-specific IgG antibody consistent with active FRα-specific helper T cell immunity. Conclusions: These findings demonstrate that the FRα is a target of the immune system in patients with breast or ovarian cancer. Understanding the antigens that are naturally targeted by the immune system may be important for diagnosis, prognosis, and immune-based therapies. No significant financial relationships to disclose.

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Functional Folate Receptor Alpha Is Elevated in the Blood of Ovarian Cancer Patients

PLoS ONE ◽

10.1371/journal.pone.0006292 ◽

2009 ◽

Vol 4 (7) ◽

pp. e6292 ◽

Cited By ~ 43

Author(s):

Eati Basal ◽

Guiti Z. Eghbali-Fatourechi ◽

Kimberly R. Kalli ◽

Lynn C. Hartmann ◽

Karin M. Goodman ◽

...

Keyword(s):

Ovarian Cancer ◽

Cancer Patients ◽

Folate Receptor ◽

Folate Receptor Alpha ◽

Receptor Alpha

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Isolation of Circulating Tumor Cells from Multiple Epithelial Cancers with ApoStream® for Detecting (or Monitoring) the Expression of Folate Receptor Alpha

Biomarker Insights ◽

10.4137/bmi.s35075 ◽

2016 ◽

Vol 11 ◽

pp. BMI.S35075 ◽

Cited By ~ 11

Author(s):

Daniel J. O'Shannessy ◽

Darren W. Davis ◽

Kenna Anderes ◽

Elizabeth B. Somers

Keyword(s):

Breast Cancer ◽

Lung Cancer ◽

Ovarian Cancer ◽

Cancer Patients ◽

Folate Receptor ◽

Healthy Controls ◽

Blood Samples ◽

Folate Receptor Alpha ◽

Lung Cancer Patients ◽

Receptor Alpha

This study describes our efforts to further the field of noninvasive diagnostics, specifically in the area of liquid biopsies in oncology. We employed laser scanning cytometry using highly selective antibodies to interrogate circulating tumor cells (CTCs) that were isolated using ApoStream® technology to identify folate receptor alpha (FRα)–positive cells. We demonstrate that FRα+ CTCs can be isolated from patients with metastatic cancers, including NSCLC adenocarcinoma, breast cancer, and ovarian cancer, whereas squamous cell lung cancer and normal healthy controls were devoid of FRα+ CTCs. We believe that the developed methodology will have applications in both the diagnosis and the monitoring of FRα-expressing cancers. Folate receptor alpha (FRα) expression may have utility as a potential diagnostic and therapeutic target in solid tumors. As tissue samples are not always available for patient screening, this study evaluated a noninvasive assay in CTCs from blood samples to detect FRα expression. The presence of FRα+ CTCs enriched using ApoStream® and detected using laser capture cytometry was evaluated in blood samples from cancer patients [NSCLC adenocarcinoma ( n = 14), breast cancer ( n = 20), ovarian cancer ( n = 6), and squamous lung cancer patients ( n = 6)] and healthy subjects ( n = 20). The data demonstrated that FRα+ CTCs were detected in blood from NSCLC adenocarcinoma, breast, and ovarian cancer patients, whereas squamous cell lung cancer patients and normal healthy controls lacked FRα+ CTCs as previously known. We demonstrate that CTCs captured using ApoStream® can be used to detect FRα+ CTCs and may have clinical utility as a real-time liquid biopsy for assessing FRα levels in cancer patients.

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