Identification of Pancreatic Cancer-Associated Tumor Antigen from HSP-Enriched Tumor Lysate-Pulsed Human Dendritic Cells

PURPOSE: Vaccine strategies utilizing dendritic cells (DCs) to elicit anti-tumor immunity are the subject of intense research. Although we have shown that DCs pulsed with heat-treated tumor lysate (HTL) induced more potent anti-tumor immunity than DCs pulsed with conventional tumor lysate (TL), the underlying molecular mechanism is unclear. In order to explore the molecular basis of this approach and to identify potential antigenic peptides from pancreatic cancer, we analyzed and compared the major histocompatibility complex (MHC) ligands derived from TL- and HTL-pulsed dendritic cells by mass spectrophotometry. MATERIALS AND METHODS: Human monocyte-derived dendritic cells were pulsed with TL or HTL prior to maturation induction. To delineate differences of MHC-bound peptide repertoire eluted from DCs pulsed with TL or HTL, nanoflow liquid chromatography-electrospray ionization-tandem mass spectrometry (nLC-ESI-MS-MS) was employed. RESULTS: HTL, but not TL, significantly induced DC function, assessed by phenotypic maturation, allostimulation capacity and IFN-gamma secretion by stimulated allogeneic T cells. DCs pulsed with TL or HTL displayed pancreas or pancreatic cancer-related peptides in context of MHC class I and II molecules. Some of the identified peptides had not been previously reported as expressed in pancreatic cancer or cancer of other tissue types. CONCLUSION: Our partial lists of MHC-associated peptides revealed the differences between peptide profiles eluted from HTL-and TL-loaded DCs, implying that induced heat shock proteins in HTL chaperone tumor-derived peptides enhanced their delivery to DCs and promoted cross-presentation by DC. These findings may aid in identifying novel tumor antigens or biomarkers and in designing future vaccination strategies.

Modulación de la diferenciación de células dendríticas por antígenos tumorales pulmonares / Modulation of dendritic cell differentiation by lung tumor antigens

El cáncer es, en la actualidad, un serio problema de salud pública en el ámbito mundial. Una de las aproximaciones más exploradas desde hace cerca de veinte años, es la inmunoterapia con células dendríticas (CD), células presentadoras de antígenos (CPA) profesionales. No obstante, los resultados de los estudios clínicos que emplean CD autólogas pulsadas con antígenos tumorales no han sido tan exitosos como se proyectaba. Una de las hipótesis propuestas que justifique la eficacia tan variable en los protocolos terapéuticos, es la inducción de tolerancia en las CD por los antígenos tumorales y la subsecuente baja actividad de las células efectoras (linfocitos T CD8+, CD4+ y Natural Killer). En este trabajo se evidencia que los antígenos tumorales provenientes de un adenocarcinoma pulmonar favorecen la reaparición de co-receptores como el CD14, conocido marcador de inmadurez en CD. Esto sugiere que en algunos aspectos las CD expuestas a tales antígenos, muestran defectos en la diferenciación. Como se sabe, las CD inmaduras tienen una potencia estimuladora mucho menor sobre las células efectoras, comparativamente con las CD de fenotipo maduro. Sin embargo, antígenos provenientes de la línea comercial A549 (adenocarcinoma) no produjeron cambios similares en la maduración de CD. Ello resalta la necesidad de caracterizar la respuesta individual in vitro al planear una terapia basada en CD, a fin de tener mayor probabilidad de éxito en el tratamiento.

Cancer is currently a very serious public health problem worldwide. Dendritic cell (DC) based immunotherapy has been one of the most active research fields during the last 20 years. However, results of several studies, mainly involving tumor antigen pulsed autologous DCs, have not been as successful as expected. Induction of a tolerant behavior of DCs upon the contact with tumor derived antigens is one of the hypotheses proposed since other effector cells like CD8+, CD4+ T lymphocytes and Natural Killers, would be rendered to a non-responsive state seriously impairing tumor growth control. In this work we found additional evidence about a likely DC differentiation defect caused by lung adenocarcinoma specific antigens freshly obtained from a patient, as suggested by the presence of the co-receptor CD14 on the surface of mature DCs (CD14 is a known marker for initial stages of DC differentiation). Our results confirm that some aspects in tumor antigen treated DCs resemble their immature phenotype, largely less efficient presenting cells, and very weak immune response inducers. Interestingly, tumor antigens obtained from the lung adenocarcinoma derived A549 cell line were unable to cause the same effect. This highlights the requirement for a complete characterization of the functional nd phenotypic individual conditions when planning a DC based immunotherapy in order to have good success likelihood at cancer patient’s treatment.

Immunoregulation through IL-10 gene expression and the fate of cytotoxic T lymphocyte-mediated tumor immunotherapy.

Gene analysis of tumor associated antigens revealed that tumor antigens are all normal gene product. Inducing tumor reactive cytotoxic T lymphocytes (CT) in the patients is same as inducing autoimmunity in the patients. Immunosuppressive cytokine interleukin-10 (IL-10) plays an important role in maintaining homeostasis or tolerance. To break the tumor tolerance, blocking and IL-10 secretion or intervention in the pathways of IL-10 gene activation is indeed important.