Tumor immunotherapy by converting tumor cells to MHC class II-positive, Ii protein-negative phenotype

Progress in the Use of Antisense Oligonucleotides for Vaccine Improvement

: Antisense oligonucleotides (ASOs) are synthetically prepared short single-stranded deoxynucleotide sequences that have been validated as therapeutic agents and as a valuable tool in molecular driving biology. ASOs can block the expression of specific target genes via complementary hybridization to mRNA. Due to their high specificity and well-known mechanism of action, there has been a growing interest in using them for improving vaccine efficacy. Several studies have shown that ASOs can improve the efficacy of vaccines either by inducing antigen modification such as enhanced expression of immunogenic molecules or by targeting certain components of the host immune system to achieve the desired immune response. However, despite their extended use, some problems such as insufficient stability and low cellular delivery have not been sufficiently resolved to achieve effective and safe ASO-based vaccines. In this review, we analyze the molecular bases and the research that has been conducted to demonstrate the potential use of ASOs in vaccines.

Development of potent class II transactivator gene delivery systems capable of inducing de novo MHC II expression in human cells, in vitro and ex vivo

Class II transactivator (CIITA) induces transcription of major histocompatibility complex (MHC) II genes and can potentially be used to improve genetic immunotherapies by converting non-immune cells into cells capable of presenting antigens to CD4⁺ T cells. However, CIITA expression is tightly controlled and it remains unclear whether distinct non-immune cells differ in this transactivator regulation. Here we describe the development of gene delivery systems capable of promoting the efficient CIITA expression in non-immune cell lines and in primary human cells of an ex vivo skin explant model. Different human cell types undergoing CIITA overexpression presented high-level de novo expression of MHC II, validating the delivery systems as suitable tools for the CIITA evaluation as a molecular adjuvant for gene therapies.

Expression of CD74 in invasive breast carcinoma: its relation to Nottingham Prognostic Index, hormone receptors, and HER2 immunoprofile

PURPOSE

To study the immunohistochemical expression of CD74 in series of invasive breast carcinomas classified according to their estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) immunoprofile and explore its correlation to Nottingham Prognostic Index (NPI) and tumor pathologic stage to determine if it has a prognostic value.

METHODS

A total of 160 cases of mammary carcinoma were classified broadly according to their ER, PR, and HER2 expression into luminal, HER2-positive, and triple-negative groups. The NPI was calculated and pathologic stage was recorded for each individual case and cases were classified into different prognostic groups. The CD74 expression was evaluated immunohistochemically and correlated to different prognostic variables.

RESULTS

The CD74 immunohistochemical expression in invasive breast carcinoma was significantly higher in triple-negative tumors, higher tumor grades, presence of lymph nodal metastasis, higher tumor stages, and higher NPI scores.

CONCLUSIONS

The CD74 might be a useful prognostic indicator predicting poor outcome of patients with breast carcinoma. Its consistent expression in triple-negative breast carcinomas points to the need of further studies to test the possibility if it can be targeted in treatment of breast carcinoma, especially in such groups.

Tumor cell transformation using antisense oligonucleotide

Major histocompatibility complex (MHC) Class II-positive, invariant chain (Ii)-suppressed tumor cells induce both T helper and cytotoxic T lymphocytes' responses. Genetically controlled immunotherapy could be utilized for prophylactic vaccination of tumor-free individuals who are at high risk of developing tumor and can be therapeutic for treating established tumors that are nonresponsive to existing therapies. In this chapter, we provide practical methods to create a potent in vivo tumor cell vaccine by inducing MHC Class II and Ii using MHC Class II transactivator (CIITA) or interferon-gamma (IFN-γ) and subsequently inhibiting Ii by antisense oligonucleotides. We also describe the development of an adenoviral vector.

Establishment and characterization of transplantable, luminescence labeled rat renal cell carcinoma cell lines

PURPOSE

Since renal cell carcinoma is considered an immunogenic tumor, testing therapeutic strategies has been impeded by the lack of relevant tumor models in immunocompetent animals. Recent advances in bioluminescence imaging permit sensitive in vivo detection and quantification of cells emitting light. Thus, we established bioluminescent rat renal cell carcinoma cell lines for immunocompetent rats.

MATERIALS AND METHODS

The rat renal cell carcinoma cell line ACI-RCC stemming from chemically induced renal cell carcinoma in syngeneic ACI rats was stably transfected with a recombinant retroviral vector encoding luciferase genes derived from fireflies (ACI-RCC-ffLuc) or click beetles (ACI-RCC-cbLuc). Cell line growth patterns were characterized by bioluminescence imaging.

RESULTS

Linear correlations noted observed between cell number and photon counts in each cell type. ACI-RCC-cbLuc emitted light about 500-fold higher than ACI-RCC-ffLuc. When transplanted subcutaneously, only ACI-RCC-ffLuc grew, possibly because of less antigenicity. ACI-RCC-ffLuc photon emission correlated significantly with subcutaneous tumor size. Orthotopic tumor growth and subsequent metastatic spread were monitored with time by increased photon intensity on bioluminescence imaging. Based on ACI-RCC-cbLuc bioluminescent intensity the in vitro screening test allowed the identification of several anticancer agents, including molecules related to human renal cell carcinoma progression.

CONCLUSIONS

The new in vivo rat renal cell carcinoma model with luciferase labeled tumor cells allowed us to monitor tumor growth noninvasively and semiquantitatively by bioluminescence imaging. This model system coupled with in vitro screening permits precise evaluation of tumor behavior in intact animals and determination of the therapeutic efficacy of anticancer agents for renal cell carcinoma.

Intratumoral DNA electroporation induces anti-tumor immunity and tumor regression

In situ expression of a foreign antigen and an immune-modulating cytokine by intratumoral DNA electroporation was tested as a cancer therapy regimen. Transgene expression in the tumors was sustained for 2-3 weeks after intratumoral electroporation with mammalian expression plasmid containing firefly luciferase cDNA. Electroporation with cDNA encoding tetanus toxin fragment C (TetC) induced tetanus toxin-binding antibody, demonstrating immune recognition of the transgene product. Intratumoral electroporation with TetC and IL-12 cDNA after mice were treated with CD25 mAb to remove regulatory T cells induced IFN-gamma producing T-cell response to tumor-associated antigen, heavy inflammatory infiltration, regression of established tumors and immune memory to protect mice from repeated tumor challenge. Intratumoral expression of immune-modulating molecules may be most suitable in the neoadjuvant setting to enhance the therapeutic efficacy and provide long-term protection.

Down-regulation of CD55 and CD46 expression by anti-sense phosphorothioate oligonucleotides (S-ODNs) sensitizes tumour cells to complement attack

Overexpression of one or more membrane-bound complement regulatory proteins (mCRPs) protects tumour cells against complement-mediated clearance by the autologous humoral immune response and is also considered as a barrier for successful immunotherapy with monoclonal anti-tumour antibodies. Neutralization of mCRPs by blocking antibodies, enzymatic removal or cytokine-mediated down-regulation has been shown to sensitize tumour cells to complement attack. In our study we applied, for the first time, anti-sense phosphorothioate oligonucleotides (S-ODNs) to knock down the expression of the mCRPs CD55 and CD46 with the aim of exploiting complement more effectively for tumour cell damage. Potent anti-sense oligonucleotides against CD55 and CD46 were identified by screening various target sequences (n = 10) for each regulator. S-ODN anti-CD55(687) reduced CD55 protein expression up to 84% and CD46 protein expression was inhibited up to 76% by S-ODN anti-CD46(85). Reverse transcription-polymerase chain reaction (RT-PCR) analysis revealed a similar reduction of the CD55 and CD46 mRNA levels, which argues for an RNAse H-dependent anti-sense mechanism. T47D, A549 and PC3 cells, representing breast, lung and prostate carcinoma, were used for functional studies. Dependent on the particular cell line, anti-sense-based inhibition of mCRP expression enhanced complement-dependent cytolysis (CDC) up to 42% for CD55 and up to 40% for CD46, and the combined inhibition of both regulators yielded further additive effects in T47D cells. C3 opsonization of CD55/CD46-deficient tumour cells was also clearly enhanced upon mCRP suppression. Due to the clinical applicability of S-ODNs, the anti-sense approach described in this study may offer an additional alternative to improve the efficacy of antibody- and complement-based cancer immunotherapy.

Suppression of major histocompatibility complex class II-associated invariant chain enhances the potency of an HIV gp120 DNA vaccine

Summary One function of the major histocompatibility complex (MHC) class II-associated invariant chain (Ii) is to prevent MHC class II molecules from binding endogenously generated antigenic epitopes. Ii inhibition leads to MHC class II presentation of endogenous antigens by APC without interrupting MHC class I presentation. We present data that in vivo immunization of BALB/c mice with HIV gp120 cDNA plus an Ii suppressive construct significantly enhances the activation of both gp120-specific T helper (Th) cells and cytotoxic T lymphocytes (CTL). Our results support the concept that MHC class II-positive/Ii-negative (class II(+)/Ii(-)) antigen-presenting cells (APC) present endogenously synthesized vaccine antigens simultaneously by MHC class II and class I molecules, activating both CD4(+) and CD8(+) T cells. Activated CD4(+) T cells locally strengthen the response of CD8(+) CTL, thus enhancing the potency of a DNA vaccine.

RENCA/carbonic anhydrase-IX: a murine model of a carbonic anhydrase-IX-expressing renal cell carcinoma

OBJECTIVES

Carbonic anhydrase-IX (CA-IX) is a cell surface tumor-associated antigen expressed by most clear cell renal cell carcinomas (RCCs). The specificity and the prognostic value of CA-IX provide impetus to create a mouse model of CA-IX-expressing RCC for testing CA-IX-targeted therapies against RCC.

METHODS

A retrovirus encoding the human CA-IX gene was used to transduce the murine RCC line, RENCA. In vivo growth kinetics and CA-IX expression were compared between RENCA and RENCA/CA-IX using heterotopic, metastatic, and orthotopic models.

RESULTS

Transduction of RENCA created the RENCA/CA-IX line with nearly 100% CA-IX surface expression. In the heterotopic model, subcutaneous injection of 500,000 and 50,000 cells led to tumor formation at 2 to 2.5 weeks after injection, with similar growth kinetics between the two cell lines at either cell number. In the pulmonary metastatic model, a similar number of metastases was noted after inoculation of RENCA and RENCA/CA-IX. In the orthotopic model, autopsy revealed a CA-IX-expressing renal tumor, as well as CA-IX-expressing metastases to the lungs, liver, contralateral kidney, intestines, and lymph nodes. In all the above models, the RENCA/CA-IX tumors retained expression of CA-IX, as demonstrated by immunohistochemistry staining.

CONCLUSIONS

RENCA/CA-IX is the first tumor model that manifests in immunocompetent Balb/c mice and stably expresses a defined kidney cancer-associated antigen. It maintains antigen expression, forms metastases, and produces reliable tumor growth kinetics equivalent to that of its parental cell line.

Helicobacter pylori CagA-dependent macrophage migration inhibitory factor produced by gastric epithelial cells binds to CD74 and stimulates procarcinogenic events

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine that has recently been implicated in carcinogenesis. Helicobacter pylori, which is closely linked to gastric cancer, induces the gastric epithelium to produce proinflammatory cytokines, including MIF. MIF can bind to CD74, which we have previously shown to be highly expressed on the surface of gastric epithelial cells (GEC) during H. pylori infection. In this study, we sought to investigate the role of the H. pylori-induced MIF on epithelial proliferation and procarcinogenic events. Upon establishing a role for the H. pylori CagA virulence factor in MIF production, MIF binding to CD74 on GEC was confirmed. rMIF and H. pylori were shown to increase GEC proliferation, which was decreased when cagA- strains were used and when CD74 was blocked by mAbs. Apoptosis was also decreased by MIF, but increased by cagA- strains that induced much lower amounts of MIF than the wild-type bacteria. Furthermore, MIF binding to CD74 was also shown to decrease p53 phosphorylation and up-regulate Bcl-2 expression. This data describes a novel system in which an H. pylori virulence factor contributes to the production of a host factor that in turn up-regulates procarcinogenic events by the gastric epithelium.

Tumor cells transduced with the MHC class II Transactivator and CD80 activate tumor-specific CD4+ T cells whether or not they are silenced for invariant chain

The specificity and potency of the immune system make immunotherapy a potential strategy for the treatment of cancer. To exploit this potential, we have developed cell-based cancer vaccines consisting of tumor cells expressing syngeneic MHC class II and costimulatory molecules. The vaccines mediate tumor regression in mice and activate human CD4+ T cells in vitro. Previous vaccines were generated by transducing MHC II negative tumor cells with a single HLA-DR allele. Because expression of multiple MHC II alleles would facilitate presentation of a broader repertoire of tumor antigens, we have now transduced tumor cells with the MHC class II transactivator (CIITA), a regulatory gene that coordinately increases expression of all MHC II alleles. Previous studies in mice indicated that coexpression of the MHC II accessory molecule invariant chain (Ii) inhibited presentation of endogenously synthesized tumor antigens and reduced vaccine efficacy. To determine if Ii expression affects presentation of MHC class II-restricted endogenously synthesized tumor antigens in human tumor cells, HLA-DR-MCF10 breast cancer cells were transduced with the CIITA, CD80 costimulatory molecule gene, and with or without small interfering RNAs (siRNA) specific for Ii. Ii expression is silenced >95% in CIITA/CD80/siRNA transductants; down-regulation of Ii does not affect HLA-DR expression or stability; and Ii(+) and Ii(-) transductants activate human CD4+ T cells to DRB1*0701-restricted HER-2/neu epitopes. Therefore, tumor cells transduced with the CIITA, CD80, and with or without Ii siRNA present endogenously synthesized tumor antigens and are potential vaccines for activating tumor-specific CD4+ T cells.

Antitumour activity mediated by CD4+ cytotoxic T lymphocytes against MHC class II-negative mouse hepatocellular carcinoma induced by dendritic cell vaccine and interleukin-12

When BALA/c mice with BNL hepatocellular carcinoma (HCC) were treated with dendritic cells fused with BNL cells (DC/BNL) and recombinant murine interleukin (IL)-12, tumour development was significantly suppressed, whereas treatment with either DC/BNL or IL-12 alone did not show a tumour-suppressive effect. Antitumour activity induced by DC/BNL + IL-12 was abrogated by depletion of CD4+ T cells, but not by depletion of CD8+ T cells or natural killer cells. Splenic CD4+ T cells and CD8+ T cells from DC/BNL-treated mice showed cytotoxic activity against BNL cells after 3 days of incubation with DC/BNL, although BNL cells do not express major histocompatibility complex (MHC) class II molecules even after treatment with interferon (INF)-gamma. Furthermore, CD4+ T cells killed syngeneic-irrelevant CT26 cells and even allogeneic Hepa1-6 cells. This cytotoxicity was blocked by concanamycin A, but not by an anti-Fas ligand (FasL) monoclonal antibody, indicating that cytotoxic activity was mediated by perforin. Immunofluorescence microscopy demonstrated that abundant CD4+ T cells and MHC class II-positive macrophages, but not CD8(+) T cells, had infiltrated tumour tissue in mice treated with DC/BNL + IL-12. Flow cytometric analysis of tumour-infiltrating cells in mice treated with DC/BNL + IL-12 showed increases in CD4+ T cells and MHC class II+ CD11b+ cells but not in CD8+ T cells or MHC class I+ CD11b+ cells. Our results suggest that, in BNL-bearing mice treated with DC/BNL + IL-12, tumour macrophages activated by INF-gamma produced by IL-12-stimulated T cells might present BNL tumour antigens and activate DC/BNL-primed CD4+ cytotoxic T lymphocytes (CTLs) in a MHC class II-dependent manner, leading to perforin-mediated bystander killing of neighbouring MHC class II-negative tumour cells.

Curative Antitumor Immune Response Is Optimal with Tumor Irradiation Followed by Genetic Induction of Major Histocompatibility Complex Class I and Class II Molecules and Suppression of Ii Protein

Transfecting genes into tumors, to upregulate major histocompatibility complex (MHC) class I and class II molecules and inhibit MHC class II associated invariant chain (Ii), induces a potent anti-tumor immune response when preceded by tumor irradiation, in murine RM-9 prostate carcinoma. The transfected genes are cDNA plasmids for interferon-gamma (pIFN-gamma), MHC class II transactivator (pCIITA), an Ii reverse gene construct (pIi-RGC), and a subtherapeutic dose of adjuvant IL-2 (pIL-2). Responding mice rejected challenge with parental tumor and demonstrated tumor-specific cytotoxic T lymphocytes (CTLs). We have extended our investigation to determine the relative roles of each one of the four plasmids pIFN-gamma, pCIITA, pIi-RGC, and pIL-2 in conjunction with radiation for the induction of a curative immune response. Upregulation of MHC class I with pIFN-gamma or class II with pCIITA, separately, does not lead to a complete response even if supplemented with pIL-2 or pIi-RGC. An optimal and specific antitumor response is achieved in more than 50% of the mice when, after tumor irradiation, tumor cells are converted in situ to a MHC class I+/class II+/Ii- phenotype with pIFN-gamma, pCIITA, pIi-RGC, and pIL-2. We demonstrate further that both CD4+ helper T cells and CD8+ cytotoxic T cells are essential for induction of an antitumor response because in vivo depletion of either subset abrogates the response. The radiation contributes to the gene therapy by causing tumor debulking and increasing the permeability of tumors to infiltration of inflammatory cells.

Turning tumor cells in situ into T-helper cell-stimulating, MHC class II tumor epitope-presenters: immuno-curing and immuno-consolidation

Immunological control or cure of tumors depends on initiating a robust T helper cell response to MHC class II epitopes of tumor-associated antigens. T helper cells regulate the potency of cytotoxic T lymphocyte and antibody responses. We have developed a novel approach to stimulate T helper cells by converting tumor cells into MHC class II molecule-positive, antigen presenting cells. Furthermore, using antisense methods, we suppress expression of the Ii protein, that normally blocks the antigenic peptide binding site of MHC class II molecules during synthesis in the endoplasmic reticulum. In such gene-engineered tumor cells, the MHC class II molecules pick up antigenic peptides, which have been transported into the endoplasmic reticulum for binding to MHC class I molecules. All nucleated cells create such "surveys of self" to detect viral or malignant transformation. Our method extends that survey of self to MHC class II endogenous tumor-associated antigens. Simultaneous presentation of tumor antigens by both MHC class I and II generates a robust and long-lasting antitumor immune response. Injecting murine tumors with genes, which induce MHC class II molecules and suppress Ii protein, cures a significant number of animals with renal and prostate tumors. We have developed analogous human gene vectors that are suitable for most patients and cancers, because they are monomorphic and active in all HLA-DR alleles. We review our findings, and analyze remaining issues for preclinical study and the design of clinical trials.