Recent progress in tumour vaccine development

De novo induction of a cancer/testis antigen by 5-aza-2'-deoxycytidine augments adoptive immunotherapy in a murine tumor model

Recent studies suggest that immunotherapy targeting specific tumor-associated antigens (TAAs) may be beneficial in cancer patients. However, most of these TAAs are tumor type specific and heterogeneous among patients, thus limiting their applications. Here, we describe the de novo induction of a cancer/testis antigen (CTA) for immunotherapy of tumors of various histologies. The murine CTA P1A, normally expressed only in a few tumor lines, could be induced de novo in all P1A-negative cancer lines of eight histologic origins in vitro and in various murine xenografts by systemic administration of 5-aza-2'-deoxycytidine. The induction of P1A expression correlated strongly with demethylation of the CpG island in the promoter region of this gene. The induced antigen was processed and presented properly for recognition by H-2L(d)-restricted P1A-specific CTLs. The combination of a demethylating agent and adoptive transfer of P1A-specific CTL effectively treated lung metastases in syngeneic mice challenged with P1A-negative 4T1 mammary carcinoma cells. These data show a novel strategy of combined chemoimmunotherapy of cancer targeting a CTA induced de novo in a broad range of tumor histologies, and support further evaluation of chromatin-remodeling agents for human cancer therapy.

Antitumor efficacy of DNA vaccination to the epigenetically acting tumor promoting transcription factor BORIS and CD80 molecular adjuvant

Cancer testis (CT) antigens are promising candidates for tumor vaccines due to their immunogenicity and tissue-restricted expression. Recently, we identified a novel cancer testis gene, BORIS, whose expression is restricted to male testis after puberty and is strictly absent in non-malignant female tissue. BORIS encodes a DNA-binding protein that shares 11 zing finger (ZF) with transcription factor CTCF and differs at the N- and C-termini. CTCF has been implicated in epigenetic regulation of imprinting, X chromosome inactivation, repression, and activation of cancer testis antigens. BORIS expression has been documented in cancers of diverse histological origin, including, but not limited to breast, prostate, ovary, gastric, liver, endometrial, glia, colon, and esophagus. Interestingly, BORIS induces demethylation and subsequent expression of many cancer-testis genes, including MAGE-A1 and NY-ESO-1, indicating that it is expressed very early in malignancy and might be an attractive candidate for immunotherapy. In this study we tested BORIS as a vaccine in a very aggressive, highly metastatic, and poorly immunogenic murine model of mammary carcinoma. Immunizations with a DNA encoding the mutant form of murine BORIS antigen (pmBORIS lacking DNA-binding function) significantly prolonged survival, and inhibited tumor growth in BALB/c mice inoculated with 4T1 cells. Priming with pmBORIS mixed with molecular adjuvant and boosting with adenoviral vector expressing mBORIS was generally more effective, suggesting that the vaccination protocol could be further optimized. This is the first report demonstrating the feasibility of vaccination with a cancer associated epigenetic regulator for the induction of tumor inhibition.

Peptide-based vaccines for cancer immunotherapy

One approach in the immunotherapy of cancer patients involves vaccination with peptides derived from tumour-associated antigens specifically designed to associate with T cells in the context of major histocompatibility complex (MHC) class I or II molecules. Several clinical trials in different tumour types have been conducted utilising this vaccination strategy. The majority of trials indicate that peptide vaccination has few toxicities associated with its administration, but disparities exist between in vitro and clinical responses. However, this represents an evolving field and, thus, it is difficult to draw firm conclusions concerning the efficacy of peptide-based vaccines for cancer immunotherapy. Improvements to peptide vaccination, including the addition of various adjuvants, the utilisation of peptide-pulsed dendritic cells, multipeptide vaccinations, the addition of helper peptides and peptide delivery through the use of mini-genes, are encouraging and serve as important guides for future research.

Dendritic Cell Maturation Requires STAT1 and Is under Feedback Regulation by Suppressors of Cytokine Signaling

In this study we show that activation of STAT pathways is developmentally regulated and plays a role in dendritic cell (DC) differentiation and maturation. The STAT6 signaling pathway is constitutively activated in immature DC (iDC) and declines as iDCs differentiate into mature DCs (mDCs). However, down-regulation of this pathway during DC differentiation is accompanied by dramatic induction of suppressors of cytokine signaling 1 (SOCS1), SOCS2, SOCS3, and cytokine-induced Src homology 2-containing protein expression, suggesting that inhibition of STAT6 signaling may be required for DC maturation. In contrast, STAT1 signaling is most robust in mDCs and is not inhibited by the up-regulated SOCS proteins, indicating that STAT1 and STAT6 pathways are distinctly regulated in maturing DC. Furthermore, optimal activation of STAT1 during DC maturation requires both IL-4 and GM-CSF, suggesting that synergistic effects of both cytokines may in part provide the requisite STAT1 signaling intensity for DC maturation. Analyses of STAT1(-/-) DCs reveal a role for STAT1 in repressing CD86 expression in precursor DCs and up-regulating CD40, CD11c, and SOCS1 expression in mDCs. We further show that SOCS proteins are differentially induced by IL-4 and GM-CSF in DCs. SOCS1 is primarily induced by IL-4 through a STAT1-dependent mechanism, whereas SOCS3 is induced mainly by GM-CSF. Taken together, these results suggest that cytokine-induced maturation of DCs is under feedback regulation by SOCS proteins and that the switch from constitutive activation of the STAT6 pathway in iDCs to predominant use of STAT1 signals in mDC is mediated in part by STAT1-induced SOCS expression.