High-Affinity HLA-A(*)02.01 Peptides from Parathyroid Hormone-Related Protein Generate In Vitro and In Vivo Antitumor CTL Response Without Autoimmune Side Effects

Abstract

Parathyroid hormone-related protein (PTH-rP), a protein produced by prostate carcinoma and other epithelial cancers, is a key agent in the development of bone metastases. We investigated whether the protein follows the self-tolerance paradigm or can be used as a target Ag for anticancer immunotherapy by investigating the immunogenicity of two HLA-A(*)02.01-binding PTH-rP-derived peptides (PTR-2 and -4) with different affinity qualities. PTH-rP peptide-specific CTL lines were generated from the PBMC of two HLA-A(*)02.01+ healthy individuals, stimulated in vitro with PTH-rP peptide-loaded autologous dendritic cells and IL-2. The peptide-specific CTLs were able to kill PTH-rP+HLA-A(*)02.01+ breast and prostate carcinoma cell lines. The two peptides were also able to elicit a strong antitumor PTH-rP-specific CTL response in HLA-A(*)02.01 (HHD) transgenic mice. The vaccinated mice did not show any sign of side effects due to cell-mediated autoimmunity or toxicity. In this study we describe two immunogenic and toxic-free PTH-rP peptides as valid candidates for the design of peptide-based vaccination strategies against prostate cancer and bone metastases from the most common epithelial malignancies.

Identification of parathyroid hormone-related protein-derived peptides immunogenic in human histocompatibility leukocyte antigen-A24+ prostate cancer patients

“…This result is consistent with that of a previous report demonstrating the induction of PTHrP peptidespecific CTLs from the PBMCs of HLA-A2 þ healthy donors (Francini et al, 2002). As the PTHrP 36 -44 peptide shares three amino acids with PTH, and because there is no homology between the PTHrP 102 -111 peptide and PTH, crossreactivity between the PTHrP peptides and PTH could be excluded.…”

“…The background IFN-g production in response to the HIV peptide was subtracted, and the results that showed the best response are shown in In order to investigate the HLA-A24-restricted and prostate cancer-reactive cytotoxicity of peptide-stimulated PBMCs, we prepared an HLA-A24-expressing LNCaP cell line, which we designated LNCaP-A24 (Figure 2). LNCaP has previously been reported to produce PTHrP (Francini et al, 2002). A parental LNCaP cell line was negative for the cell surface expression of HLA-A24 molecules, whereas the LNCaP-A24 cell line expressed HLA-A24 molecules on their cell surface.…”

“…These lines of evidence indicate that PTHrP could be a good target for the development of specific immunotherapies against metastatic prostate cancer. Indeed, PTHrP 59 -68 and PTHrP 165 -173 peptides have been reported to be candidates for such specific immunotherapy of HLA-A2 þ prostate cancer patients (Guise, 1997;Francini et al, 2002). In this study, we identified new PTHrP peptides that have the potential to generate prostate cancerspecific CTLs in HLA-A24 þ prostate cancer patients, in order to extend the possibility of PTHrP peptide-based anticancer vaccine.…”

“…Therefore, we undertook the present study to identify epitope peptides that could potentially be suitable for specific the immunotherapy of HLA-A24 þ prostate cancer patients with metastases. PTHrP is known to be a key agent in the development of bone metastasis in cases of prostate cancer, and prostate cancer cells has been reported to produce PTHrP (Francini et al, 2002). These lines of evidence indicate that PTHrP could be a good target for the development of specific immunotherapies against metastatic prostate cancer.…”

“…Therefore, PTHrP has been considered to be responsible for the hypercalcemia associated with malignancy (Guise, 1997). In addition, prostate cancers have been reported to produce PTHrP (Francini et al, 2002). These lines of evidence suggest that PTHrP could be a promising target molecule for the immunotherapy of prostate cancer patients with bone metastases.…”