Heat Shock Protein–Based Cancer Vaccines

Glioma progression through the prism of heat shock protein mediated extracellular matrix remodeling and epithelial to mesenchymal transition

Glial tumor is one of the intrinsic brain tumors with high migratory and infiltrative potential. This essentially contributes to the overall poor prognosis by circumvention of conventional treatment regimen in glioma. The underlying mechanism in gliomagenesis is bestowed by two processes- Extracellular matrix (ECM) Remodeling and Epithelial to mesenchymal transition (EMT). Heat Shock Family of proteins (HSPs), commonly known as "molecular chaperons" are documented to be upregulated in glioma. A positive correlation also exists between elevated expression of HSPs and invasive capacity of glial tumor. HSPs overexpression leads to mutational changes in glioma, which ultimately drive cells towards EMT, ECM modification, malignancy and invasion. Differential expression of HSPs - a factor providing cytoprotection to glioma cells, also contributes towards its radioresistance /chemoresistance. Various evidences also display upregulation of EMT and ECM markers by various heat shock inducing proteins e.g. HSF-1. The aim of this review is to study in detail the role of HSPs in EMT and ECM leading to radioresistance/chemoresistance of glioma cells. The existing treatment regimen for glioma could be enhanced by targeting HSPs through immunotherapy, miRNA and exosome mediated strategies. This could be envisaged by better understanding of molecular mechanisms underlying glial tumorigenesis in relation to EMT and ECM remodeling under HSPs influence. Our review might showcase fresh potential for the development of next generation therapeutics for effective glioma management.

Cancer immunotherapy by fusions of dendritic cells and tumor cells

Dendritic cells (DCs) are potent professional antigen-presenting cells and play a critical role in the induction of primary immune responses. DC-based vaccination represents a potentially powerful strategy for cancer immunotherapy. Thus, the use of cancer vaccines to eliminate residual tumor cells is a promising area of investigation. The immunotherapy of tumor antigen-loaded DCs has now been demonstrated in cancer patients and some clinical responses without any significant toxicity. Fusions of DCs and tumor cells represent an alternative but promising approach to overcome the inability of tumor antigens to induce a sustainable T-cell response. This review deals with recent progress in the immunotherapy of cancer with fusions of DCs and tumor cells.

Cancer immunotherapy targeting tumour-specific antigens: towards a new therapy for minimal residual disease

BACKGROUND

Clinical investigation of cancer immunotherapy has been very active and several approaches have been evaluated in Phase III trials. In particular, the characterisation at the molecular level of tumour-specific antigens, together with expert knowledge from GSK Biologicals in recombinant protein manufacturing and immunological Adjuvant Systems, has led the company to develop Antigen-Specific Cancer Immunotherapeutic (ASCI).

OBJECTIVE/METHODS

This paper reviews the different cancer immunotherapy approaches that have reached Phase III clinical development. A special attention is given to GSK's ASCI approach.

CONCLUSION

Based on encouraging data in a double-blind Phase II trial in non-small-cell lung cancer, the selection of the most suitable adjuvant system in melanoma and the choice of the adequate clinical setting for the clinical development of cancer immunotherapy, the ASCI approach offers the perspective that the long quest towards a new cancer treatment approach is about to succeed.

hsp70 genes in the human genome: Conservation and differentiation patterns predict a wide array of overlapping and specialized functions

Background

Hsp70 chaperones are required for key cellular processes and response to environmental changes and survival but they have not been fully characterized yet. The human hsp70-gene family has an unknown number of members (eleven counted over ten years ago); some have been described but the information is incomplete and inconsistent. A coherent body of knowledge encompassing all family components that would facilitate their study individually and as a group is lacking. Nowadays, the study of chaperone genes benefits from the availability of genome sequences and a new protocol, chaperonomics, which we applied to elucidate the human hsp70 family.

Results

We identified 47 hsp70 sequences, 17 genes and 30 pseudogenes. The genes distributed into seven evolutionarily distinct groups with distinguishable subgroups according to phylogenetic and other data, such as exon-intron and protein features. The N-terminal ATP-binding domain (ABD) was conserved at least partially in the majority of the proteins but the C-terminal substrate-binding domain (SBD) was not. Nine proteins were typical Hsp70s (65–80 kDa) with ABD and SBD, two were lighter lacking partly or totally the SBD, and six were heavier (>80 kDa) with divergent C-terminal domains. We also analyzed exon-intron features, transcriptional variants and protein structure and isoforms, and modality and patterns of expression in various tissues and developmental stages. Evolutionary analyses, including human hsp70 genes and pseudogenes, and other eukaryotic hsp70 genes, showed that six human genes encoding cytosolic Hsp70s and 27 pseudogenes originated from retro-transposition of HSPA8, a gene highly expressed in most tissues and developmental stages.

Conclusion

The human hsp70-gene family is characterized by a remarkable evolutionary diversity that mainly resulted from multiple duplications and retrotranspositions of a highly expressed gene, HSPA8. Human Hsp70 proteins are clustered into seven evolutionary Groups, with divergent C-terminal domains likely defining their distinctive functions. These functions may also be further defined by the observed differences in the N-terminal domain.

Interactions of tumor cells with dendritic cells: balancing immunity and tolerance

Dendritic cells (DCs) are antigen-presenting cells specialized to initiate and maintain immunity and tolerance. DCs initiate immune responses in a manner that depends on signals they receive from pathogens, surrounding cells and their products. Most tumors are infiltrated by DCs. Thus, interactions between DCs and dying tumor cells may determine the balance between immunity and tolerance to tumor cells. In addition, DCs also display non-immunologic effects on tumors and the tumor microenvironment. Therefore, improved understanding of the cross talk between tumor cells and DCs may suggest new approaches to improve cancer therapy.

Synergistic Induction of Antigen-Specific CTL by Fusions of TLR-Stimulated Dendritic Cells and Heat-Stressed Tumor Cells

Dendritic cell (DC)/tumor cell fusion cells (FCs) can induce potent CTL responses. The therapeutic efficacy of a vaccine requires the improved immunogenicity of both DCs and tumor cells. The DCs stimulated with the TLR agonist penicillin-killed Streptococcus pyogenes (OK-432; OK-DCs) showed higher expression levels of MHC class I and II, CD80, CD86, CD83, IL-12, and heat shock proteins (HSPs) than did immature DCs. Moreover, heat-treated autologous tumor cells displayed a characteristic phenotype with increased expression of HSPs, carcinoembryonic Ag (CEA), MUC1, and MHC class I (HLA-A2 and/or A24). In this study, we have created four types of FC preparation by alternating fusion cell partners: 1) immature DCs fused with unheated tumor cells; 2) immature DCs fused with heat-treated tumor cells; 3) OK-DCs fused with unheated tumor cells; and 4) OK-DCs fused with heat-treated tumor cells. Although OK-DCs fused with unheated tumor cells efficiently enhanced CTL induction, OK-DCs fused with heat-treated tumor cells were most active, as demonstrated by: 1) up-regulation of multiple HSPs, MHC class I and II, CEA, CD80, CD86, CD83, and IL-12; 2) activation of CD4+ and CD8+ T cells able to produce IFN- gamma at higher levels; 3) efficient induction of CTL activity specific for CEA or MUC1 or both against autologous tumor; and 4) superior abilities to induce CD107+ IFN-gamma+ CD8+ T cells and CD154+ IFN-gamma+ CD4+ T cells. These results strongly suggest that synergism between OK-DCs and heat-treated tumor cells enhances the immunogenicity of FCs and provides a promising means of inducing therapeutic antitumor immunity.

Chaperonopathies by defect, excess, or mistake

The stress response, stress proteins, heat-shock genes and proteins, molecular chaperone genes and proteins, and a number of closely related molecules and cellular processes have been studied over the last few decades. A huge amount of information has accumulated that is scattered in printed and electronic literature and databases. Most of this information constitutes the subject matter of the science of chaperonology. More recently, the concept of chaperone pathology, sick chaperones, has evolved since various pathological conditions have been identified in which defective chaperones play an etiologic role. These conditions are the chaperonopathies. Recent findings on chaperonopathies are briefly discussed in this article. Chaperonopathies occur at all ages; as a rule the genetic cases have an early clinical onset while the acquired chaperonopathies become manifest in the elderly and/or in association with other diseases. Other fields of chaperonology, which will most likely be expanded in the near future, are the study of extracellular chaperones, chaperone networks, the therapeutic use of chaperones (i.e., chaperonotherapy) to manage chaperonopathies and to improve cell performance in the face of stress, the evaluation of chaperones as diagnostic markers and as prognostic indicators, and the development of antichaperone agents to suppress chaperone-gene expression or inhibit chaperone function when chaperones contribute to disease rather than the opposite.

Chaperonopathies and chaperonotherapy

The study of molecular chaperones (genetics, structure, location, physiology, pathology, and therapeutics) has developed into a science with specific objectives, methods, and hypotheses, a discipline we called chaperonology. Subdisciplines of chaperonology include the study of pathological chaperones (chaperonopathies) and the analysis of their genes in sequenced genomes (chaperonomics). Chaperonopathies are pathological conditions in which one type of chaperone is deficient due to a genetic or acquired defect that modifies the chaperone's structure and/or makes the chaperone unavailable for functioning when needed. Experimental and clinical data show that chaperones and their genes can be used for treating various pathological conditions, thus justifying the development of chaperonotherapy. We discuss recent work showing that chaperonotherapy is on solid foundations: the data demonstrate that molecular chaperones counteract pathogenetic mechanisms in disease and during stress.

Bortezomib enhances dendritic cell (DC)-mediated induction of immunity to human myeloma via exposure of cell surface heat shock protein 90 on dying tumor cells: therapeutic implications

Most anticancer chemotherapies are immunosuppressive and induce nonimmunogenic tumor cell death. Bortezomib, a specific inhibitor of 26S proteasome, has shown clinical activity in several human tumors, including myeloma. Here we show that the uptake of human myeloma cells by dendritic cells (DCs) after tumor cell death by bortezomib, but not gamma irradiation or steroids, leads to the induction of antitumor immunity, including against primary tumor cells, without the need for any additional adjuvants. The delivery of activating signal from bortezomib-killed tumor cells to DCs depends on cell-cell contact between DCs and dying tumor cells and is mediated by bortezomib-induced exposure of heat shock protein 90 (hsp90) on the surface of dying cells. The combination of bortezomib and geldanamycin (an hsp90 inhibitor) leads to greater apoptosis of tumor cells but abrogates their immunogenicity. These data identify drug-induced exposure of endogenous heat shock proteins on the surface of dying cells as a mechanism of immunogenic death of human tumors. Specific targeting of bortezomib to tumors may enhance their immunogenicity and the induction of antitumor immunity.