Intrathymic selection: new insight into tumor immunology

Pancreatic carcinoma-specific immunotherapy using novel tumor specific cytotoxic T cells

Pancreatic cancer represents one of the most lethal human cancers. Investigation of the effective targeting to the tumor cells is essential for both primary tumors and metastases. Tumor specific cytotoxic T lymphocytes (CTLs) have recently been considered to be the attractive vehicles for delivering therapeutic agents toward various tumor diseases. This study was to explore the distribution pattern of CTL carrying the lentiviral vectors with the characteristic of adenoviral E1 gene under the control of the cell activation-dependent CD40 ligand promoter (Lenti/hCD40L/E1AB). Following transduction with adenoviral particles containing chimeric type 5 and type 35 fiber proteins (Ad5/35-TRAIL), these CTLs produced infectious virus when exposed to SW1990 cells. We found that the novel CTL harboring Lenti/hCD40L/E1AB and Ad5/35-TRAIL inhibited pancreatic cancer cell growth and angiogenesis in vitro and in vivo. Furthermore, Ad5/35-TRAIL transduced CTL induced significant apoptosis in pancreatic carcinoma cell lines and upregulated IFN-gamma (IFN-γ) secretion of CTLs. Importantly, Ad5/35-TRAIL transduced CTLs had no inhibitory effect on normal cells. Thus, the novel CTLs may be safe and feasible for the development of gene therapy approaches to pancreatic carcinoma.

Adjuvant Autologous Melanoma Vaccine for Macroscopic Stage III Disease: Survival, Biomarkers, and Improved Response to CTLA-4 Blockade

Background. There is not yet an agreed adjuvant treatment for melanoma patients with American Joint Committee on Cancer stages III B and C. We report administration of an autologous melanoma vaccine to prevent disease recurrence. Patients and Methods. 126 patients received eight doses of irradiated autologous melanoma cells conjugated to dinitrophenyl and mixed with BCG. Delayed type hypersensitivity (DTH) response to unmodified melanoma cells was determined on the vaccine days 5 and 8. Gene expression analysis was performed on 35 tumors from patients with good or poor survival. Results. Median overall survival was 88 months with a 5-year survival of 54%. Patients attaining a strong DTH response had a significantly better (p = 0.0001) 5-year overall survival of 75% compared with 44% in patients without a strong response. Gene expression array linked a 50-gene signature to prognosis, including a cluster of four cancer testis antigens: CTAG2 (NY-ESO-2), MAGEA1, SSX1, and SSX4. Thirty-five patients, who received an autologous vaccine, followed by ipilimumab for progressive disease, had a significantly improved 3-year survival of 46% compared with 19% in nonvaccinated patients treated with ipilimumab alone (p = 0.007). Conclusion. Improved survival in patients attaining a strong DTH and increased response rate with subsequent ipilimumab suggests that the autologous vaccine confers protective immunity.

A novel minigene scaffold for therapeutic cancer vaccines

Genetic vaccines are emerging as a powerful modality to induce T-cell responses to target tumor associated antigens (TAA). Viral or plasmid DNA or RNA vectors harbor an expression cassette encoding the antigen of choice delivered in vivo by vaccination. In this context, immunizations with minigenes containing selected, highly antigenic, T-cell epitopes of TAAs may have several advantages relative to full-length proteins. The objective of this study was to identify an optimal scaffold for minigene construction. We generated a number of minigenes containing epitopes from the carcinoembryonic antigen (CEA) model TAA and utilized muscle DNA electro-gene-transfer (DNA-EGT) to vaccinate HLA-A*0201 (HHD) and CEA/HHD double transgenic mice. The components utilized to construct the minigenes included CD8⁺ T cell epitopes and (or) anchor modified analogs that were selected on the basis of their predicted binding to HLA-*A0201, their uniqueness in the human proteome, and the likelihood of cancer cell natural processing and presentation via MHC-I. Other candidate components comparatively tested included: helper CD4⁺ T-cell epitopes, flanking regions for optimal epitope processing (including both proteasome-dependent and furin-dependent polypeptide processing mechanisms), and immunoenhancing moieties. Through a series of comparative studies and iterations we have identified an optimal minigene scaffold comprising the following elements: human tissue plasminogen activator (TPA) signal peptide, T-cell epitopes connected by furin sensitive linkers, and the E. Coli enterotoxin B subunit. The selected epitope modified minigenes (EMM) delivered by DNA-EGT were able to break immune tolerance in CEA/HHD mice and induce a strong immune response against all epitopes tested, independently of their relative positions within the scaffold. Furthermore, the optimized EMMs delivered via DNA-EGT were more immunogenic and exerted more powerful antitumor effects in a B16-CEA/HHD metastatic melanoma model than a DNA vector encoding the full-length protein or a mixture of the same peptides injected subcutaneously. Our data may shed light on the optimal design of a universal vehicle for epitope-targeted, genetic cancer vaccines.

Potent Antitumor Activity Generated by a Novel Tumor Specific Cytotoxic T Cell

Hepatocellular carcinoma is one of the most common malignant neoplasms in the world and is the main cause of death in patients with liver cirrhosis. Surgical intervention is not suitable for majority of hepatocellular carcinoma. Investigation of the effective targeting to the tumor cells is essential for both primary tumors and metastases. Tumor specific cytotoxic T lymphocytes (CTL) have been considered to be the attractive vehicles for delivering therapeutic agents toward various tumor diseases. This study was to explore the distribution pattern of CTL carrying the lentiviral vectors with the characteristic of adenoviral E1 gene under the control of the cell activation-dependent CD40 ligand promoter (Lenti/hCD40L/E1AB). Following transduction with adenoviral vectors containing chimeric type 5 and type 35 fiber proteins (Ad5/35-TRAIL), these CTLs produced infectious virus when exposed to HepG2 cells. We assessed the therapeutic ability of CTLs using MTT, Western blot and colony formation assay. The novel CTL harboring Lenti/hCD40L/E1AB and Ad5/35-TRAIL caused proliferation inhibition and significant apoptosis in hepatocellular carcinoma cell lines. Thus, the novel CTL may be useful for the development of gene therapy approaches to hepatocellular carcinoma.

Conditional superagonist CTL ligands for the promotion of tumor-specific CTL responses

Although it has been demonstrated that CTLs can be raised against tumor-associated self-antigens, achieving consistent and effective clinical responses has proven challenging. Superagonist altered peptide ligands (APLs) can often elicit potent antitumor CTL responses where the native tumor-associated epitope fails. Current methods have identified a limited number of superagonist APLs, including the prototypic 27L mutant of MART-1. However, more comprehensive screening strategies would be desirable. In this study, we use a novel genetic screen, involving recombinant technology and class I Ag cross-presentation, to search for supraoptimal superagonists of the 27L MART-1 mutant by surveying the effectiveness of virtually every single amino acid substitution mutant of 27L to activate human Ag-specific CTL clones recognizing the wild-type MART-1(26-35) epitope. We identify three novel mutant epitopes with superagonist properties that are functionally superior to 27L; however, the ability of a given analogue to act as superagonist varies among patients and suggests that a given superagonist APL may be ideally suited to different patients. These findings endorse the use of comprehensive methods to establish panels of potential superagonist APLs to individualize tumor peptide vaccines among patients.