RESUMEN
IMPORTANCE: In conjunction with chemotherapy, immunotherapy with dendritic cells (DCs) may eliminate minimal disease burden by generating cytotoxic T lymphocytes. Enhanced cytosolic bioavailability of tumor-specific antigens improves access to human leukocyte antigen (HLA) class I molecules for more efficient cytotoxic T lymphocyte generation. Various cell-penetrating domains (CPDs) are known to ferry covalently linked heterologous antigens to the intracellular compartment by traversing the plasma membrane. OBJECTIVE: To determine whether generating melanoma antigen family A, 3 (MAGE-A3), a tumor-specific cancer-testis antigen, as a fusion protein with CPD will enhance the cytosolic bioavailability of MAGE-A3. DESIGN: MAGE-A3 was amplified by polymerase chain reaction using complementary DNA from renal tissue and cloned in frame with a CPD (YARKARRQARR) at the amino-terminal end and hexahistidine at the carboxy-terminal end to generate CPD-MAGE-A3 in a pQE-70 expression vector. Cultures were grown in Escherichia coli BL21 Star (DE3-pLysS) cells followed by nickel-nitrilotriacetic acid affinity purification of recombinant proteins. MAIN OUTCOMES AND MEASURES: Measurement of DC membrane penetration of CPD-MAGE-A3 vs MAGE-A3 and determination of the effect of CPD-MAGE-A3 pulsing on DC phenotypic expression of cell-surface antigens. RESULTS: Media composition and isopropyl-d-thiogalactosidase induction were optimized to achieve high levels of protein expression followed by purification. Western blot analysis with MAGE-A3 antibodies recognized both MAGE-A3 and CPD-MAGE-A3 proteins, while CPD antibodies recognized only CPD-MAGE-A3. Purified CPD-MAGE-A3 exhibited more efficient DC membrane penetration than did MAGE-A3 alone as confirmed by immunofluorescence analysis. High-level expression of several unique DC markers (CD80, CD83, CD86, and HLA-DR) by flow cytometry was consistent with a mature DC phenotype, indicating that pulsing with CPD-MAGE-A3 did not alter specific cell-surface antigens required for T-cell activation. CONCLUSIONS AND RELEVANCE: We have demonstrated for the first time, to our knowledge, that cloning and purification of MAGE-A3 with CPD enhances its cytosolic bioavailability in DCs without altering cell-surface antigens, potentially making it a more potent therapeutic cancer vaccine compared with existing MAGE-A3 protein and peptide vaccines.
Asunto(s)
Antígenos de Neoplasias/uso terapéutico , Vacunas contra el Cáncer/farmacocinética , Vacunas contra el Cáncer/uso terapéutico , Permeabilidad de la Membrana Celular/efectos de los fármacos , Citosol/efectos de los fármacos , Citosol/inmunología , Células Dendríticas/efectos de los fármacos , Células Dendríticas/inmunología , Proteínas de Neoplasias/farmacocinética , Proteínas de Neoplasias/uso terapéutico , Antígenos de Neoplasias/inmunología , Disponibilidad Biológica , Vacunas contra el Cáncer/inmunología , Permeabilidad de la Membrana Celular/inmunología , Péptidos de Penetración Celular , Clonación Molecular , Ensayos de Selección de Medicamentos Antitumorales , Humanos , Proteínas de Neoplasias/inmunología , Linfocitos T Citotóxicos/efectos de los fármacos , Linfocitos T Citotóxicos/inmunologíaRESUMEN
BACKGROUND: Sulforaphane (SFN), an isothiocyanate phytochemical present predominantly in cruciferous vegetables such as brussels sprout and broccoli, is considered a promising chemo-preventive agent against cancer. In-vitro exposure to SFN appears to result in the induction of apoptosis and cell-cycle arrest in a variety of tumor types. However, the molecular mechanisms leading to the inhibition of cell cycle progression by SFN are poorly understood in epithelial ovarian cancer cells (EOC). The aim of this study is to understand the signaling mechanisms through which SFN influences the cell growth and proliferation in EOC. RESULTS: SFN at concentrations of 5-20 microM induced a dose-dependent suppression of growth in cell lines MDAH 2774 and SkOV-3 with an IC50 of ~8 microM after a 3 day exposure. Combination treatment with chemotherapeutic agent, paclitaxel, resulted in additive growth suppression. SFN at ~8 microM decreased growth by 40% and 20% on day 1 in MDAH 2774 and SkOV-3, respectively. Cells treated with cytotoxic concentrations of SFN have reduced cell migration and increased apoptotic cell death via an increase in Bak/Bcl-2 ratio and cleavage of procaspase-9 and poly (ADP-ribose)-polymerase (PARP). Gene expression profile analysis of cell cycle regulated proteins demonstrated increased levels of tumor suppressor retinoblastoma protein (RB) and decreased levels of E2F-1 transcription factor. SFN treatment resulted in G1 cell cycle arrest through down modulation of RB phosphorylation and by protecting the RB-E2F-1 complex. CONCLUSIONS: SFN induces growth arrest and apoptosis in EOC cells. Inhibition of retinoblastoma (RB) phosphorylation and reduction in levels of free E2F-1 appear to play an important role in EOC growth arrest.