Gene transfer of human interferon gamma complementary DNA into a renal cell carcinoma line enhances MHC-restricted cytotoxic T lymphocyte recognition but suppresses non-MHC-restricted effector cell activity

Immune suppression in renal cell carcinoma

The clear evidence that tumor-infiltrating lymphocytes with anti-tumor activity exist in situ raises the question why renal cell carcinomas (RCCs) progress in vivo. A complex array of factors and pathways has been identified that impinges on innate and adaptive effector cells thereby inhibiting their activity against RCCs. The current picture of suppressive mechanisms that contribute to the failure of the immune system to control RCCs is reviewed here. Understanding these complex host-tumor interactions has broad implications for successful application of cytokine therapy and other forms of immunotherapy for RCC.

Superior antitumor in vitro responses of allogeneic matched sibling compared with autologous patient CD8+ T cells

Allogeneic cell therapy as a means to break immunotolerance to solid tumors is increasingly used for cancer treatment. To investigate cellular alloimmune responses in a human tumor model, primary cultures were established from renal cell carcinoma (RCC) tissues of 56 patients. In three patients with stable RCC line and human leukocyte antigen (HLA)-identical sibling donor available, allogeneic and autologous RCC reactivities were compared using mixed lymphocyte/tumor cell cultures (MLTC). Responding lymphocytes were exclusively CD8(+) T cells, whereas CD4(+) T cells or natural killer cells were never observed. Sibling MLTC populations showed higher proliferative and cytolytic antitumor responses compared with their autologous counterparts. The allo-MLTC responders originated from the CD8(+) CD62L(high)(+) peripheral blood subpopulation containing naive precursor and central memory T cells. Limiting dilution cloning failed to establish CTL clones from autologous MLTCs or tumor-infiltrating lymphocytes. In contrast, a broad panel of RCC-reactive CTL clones was expanded from each allogeneic MLTC. These sibling CTL clones either recognized exclusively the original RCC tumor line or cross-reacted with nonmalignant kidney cells of patient origin. A minority of CTL clones also recognized patient-derived hematopoietic cells or other allogeneic tumor targets. The MHC-restricting alleles for RCC-reactive sibling CTL clones included HLA-A2, HLA-A3, HLA-A11, HLA-A24, and HLA-B7. In one sibling donor-RCC pair, strongly proliferative CD3(+)CD16(+)CD57(+) CTL clones with non-HLA-restricted antitumor reactivity were established. Our results show superior tumor-reactive CD8 responses of matched allogeneic compared with autologous T cells. These data encourage the generation of antitumor T-cell products from HLA-identical siblings and their potential use in adoptive immunotherapy of metastatic RCC patients.

TCR-independent cytokine stimulation induces non-MHC-restricted T cell activity and is negatively regulated by HLA class I

Recent evidence suggests that the functional status of T cells activated independently from their TCR differs substantially from classical MHC-restricted T cells. Here, we show that TCR-independent, short-term stimulation via the common gamma-chain of the IL-2/IL-15 receptor induces non-MHC-restricted cytotoxicity and sustained cytokine secretion in purified CD4+ or CD8+ T cells. NK-like cytotoxicity is directed against MHC class I-negative targets and can be inhibited by classical and non-classical HLA class I molecules. Known inhibitory receptors, such as CD85j (ILT2) and leukocyte-associated Ig-like receptor-1, are not responsible for this HLA-mediated inhibition. NK-like cytotoxicity can be costimulated by NKG2D (CD314) triggering, but 2B4 (CD244) and DNAM-1 (CD226) are not involved. NK-like T cells display an activated phenotype and secrete various cytokines, including IFN-gamma, TNF-alpha, IL-5, IL-13 and MIP-1beta. Under normal conditions, HLA class I-mediated inhibition may function as a safety mechanism to prevent unbalanced cytokine production and effector killing mechanisms by T cells that were activated independently from their TCR. Non-MHC-restricted activity represents a functional status rather than a property of distinct T cell subpopulations. Thus, cytokine-induced, non-MHC-restricted T cells may be relevant in immune responses against tumors showing aberrant MHC expression through their capacities of cytokine production and direct tumor cell eradication.

Cell-based vaccines for renal cell carcinoma: genetically-engineered tumor cells and monocyte-derived dendritic cells

Initial vaccine developments for renal cell carcinoma (RCC) have concentrated on cell-based approaches in which tumor cells themselves provide mixtures of unknown tumor-associated antigens as immunizing agents. Antigens derived from autologous tumors can direct responses to molecular composites characteristic of individual tumors, whereas antigens derived from allogeneic tumor cells must be commonly shared by RCC. Three types of cell-based vaccine for RCC have been investigated: isolated tumor cell suspensions, gene modified tumor cells and dendritic cells (DCs) expressing RCC-associated antigens. Approaches using genetic modification of autologous RCC have included ex vivo modification of tumor cells or modification of tumors in vivo. We have used gene-modification of allogeneic tumor cell lines to create generic RCC vaccines. More recently, emphasis has shifted to the use of DCs as cell-based vaccines for RCC. DCs have moved to a position of central interest because of their excellent stimulatory capacity, combined with their ability to process and present antigens to both naive CD4 and CD8 cells. The long impasse in identifying molecular targets for specific immunotherapy of RCC is now rapidly being overcome through the use of tools and information emerging from human genome research. Identification of candidate molecules expressed by RCC using cDNA arrays, combined with protein arrays and identification of peptides presented by MHC molecules, allow specific vaccines to be tailored to the antigenic profile of individual tumors, providing the basis for development of patient-specific vaccines.

Influence of CD80, interleukin-2, and interleukin-7 expression in human renal cell carcinoma on the expansion, function, and survival of tumor-specific CTLs

PURPOSE

A renal cell carcinoma (RCC) line, RCC-26, has been identified as a suitable candidate for development of an allogeneic tumor cell vaccine based on its expression of a variety of tumor-associated antigens (TAA). To improve immunogenicity, RCC-26 cells were genetically engineered to express CD80 alone or in combination with interleukin (IL)-2 or IL-7. The effect of these modifications on proliferation, function, and survival of autologous and allogeneic tumor-specific CTLs was assessed.

EXPERIMENTAL DESIGN

RCC-26 sublines expressing different transgenes were tested for their capacity to reactivate cytokine secretion and cytotoxicity in autologous tumor-infiltrating lymphocytes, to improve proliferation and survival of tumor-associated T cells present in autologous peripheral blood, and to induce tumor-associated responses in naive allogeneic lymphocytes. The expression of several common TAA was quantitated in the RCC-26 sublines using reverse transcription-PCR to identify surrogate markers for immune monitoring in clinical trials.

RESULTS

Gene-modified RCC-26 cells showed enhanced immunogenicity. CD80 expression was necessary to induce RCC-associated CTL in blood of healthy allogeneic donors. It also improved proliferation of autologous effector-memory T cells. Further enhancement was achieved with IL-2 through induction of the antiapoptosis protein Bcl-x(L). The candidate vaccine lines overexpressed several common TAA that are suitable markers for immune monitoring.

CONCLUSIONS

RCC-26 cells coexpressing CD80 and cytokine transgenes display improved immunogenic characteristics, supporting their use as allogeneic tumor cell vaccines for HLA-A2-matched patients with metastatic RCC.

Renal cell carcinoma-infiltrating natural killer cells express differential repertoires of activating and inhibitory receptors and are inhibited by specific HLA class I allotypes

Among tumor-infiltrating lymphocytes (TILs) directly isolated from renal cell carcinomas (RCCs), we found substantial numbers of natural killer (NK) cells in most tumor tissues. They could be identified reliably in situ with an antibody directed against the activating receptor (AR) NKp46 that is exclusively expressed by all NK cells. NK-enriched TILs (NK-TILs) showed cytotoxicity against major histocompatibility complex (MHC) class I-negative cell lines. The ability to detect lysis of target cells was dependent on the percentage of NK cells within the TILs, and cytotoxicity was only observed after overnight activation with low-dose interleukin-2 (IL-2). Infiltrating NK cells were found to express various inhibitory receptors (IRs); among these the CD94/NKG2A receptor complex was overrepresented compared to the autologous peripheral blood mononuclear cell (PBMC) population. Other IRs were underrepresented, indicating that NK subpopulations vary in their tumor-infiltrating capacity. IRs expressed by NK-TILs are functional since receptor engagement with MHC class I ligands presented by human leukocyte antigen (HLA)-transfected target cell lines was able to inhibit NK-mediated cytotoxicity. NK-TILs were also able to lyse autologous or allogeneic tumor cell lines in vitro. This activity correlated with low HLA class I surface expression since lysis could be inhibited by interferon (IFN)-gamma-expressing RCC transductants that displayed a higher surface density of HLA class I molecules. Therefore, NK cells infiltrating tumor tissues have an inherent ability to recognize transformed cells, but they require cytokine activation and are sensitive to inhibition by IR ligands.

Systemic administration of naked DNA encoding interleukin 12 for the treatment of human papillomavirus DNA-positive tumor

Interleukin 12 (IL-12) is one of the most effective and promising cytokines for cancer therapy. Its therapeutic effects have been demonstrated in a variety of tumors in animal models when it is administrated locally or systemically. We describe here a systemic delivery of naked murine IL-12 (mIL-12) gene in vivo. Dose-dependent systemic production of mIL-12, with a serum level up to approximately 20 microg/ml, was observed 24 hr after systemic gene delivery. The apparent half-life in the circulation was about 5 hr. The result of a bioactivity assay (in vitro interferon gamma [IFN-gamma] release) indicated that the gene product in mice was as active as the purified recombinant murine IL-12 protein (rmIL-12). The circulating mIL-12 activated natural killer cells and stimulated IFN-gamma production in vivo. A single administration of mIL-12 gene resulted in prominent regression of established subcutaneous tumor in a human papillomavirus (HPV) DNA-positive tumor model (TC-1) in C57BL/6J mice. The antitumor effect of the single gene dose was comparable to repeated intraperitoneal administration of rmIL-12 (0.5 microg/day for consecutive 5 days). This systemic gene delivery is simple, economical, and highly efficient for the production of large amounts of cytokine in vivo. With this gene delivery method, we have demonstrated the therapeutic potential of IL-12 for the treatment of HPV DNA-positive tumor and the usefulness of the systemic gene delivery for assessing the therapeutic effect of a candidate gene.

Allogeneic MHC class I ligands and their role in positive and negative regulation of human cytotoxic effector cells

The allogeneic mixed lymphocyte culture (MLC) has served as an important experimental system for elucidating the cellular and molecular basis of human lymphocyte responses. Complex mixtures of lymphocytes are stimulated by disparate alloantigens, inducing cellular activation and generating a cytokine milieu that is an excellent breeding ground for the proliferation and differentiation of many distinct lymphocyte subsets. Cloning of individual lymphocytes following alloactivation has allowed various cytotoxic lymphocytes to be isolated and characterized with respect to phenotype and specificity. These analyses have revealed that all types of cytotoxic effector cells are regulated by interactions with MHC-peptide ligands, however, the consequences of these interactions can result in opposite functional outcomes. In this review we summarize how allogeneic MHC class I-peptide ligands positively or negatively regulate the activities of four distinct groups of cytotoxic lymphocytes and how this information might be transferred into clinical use.

The transporter associated with antigen processing: function and implications in human diseases

The adaptive immune systems have evolved to protect the organism against pathogens encountering the host. Extracellular occurring viruses or bacteria are mainly bound by antibodies from the humoral branch of the immune response, whereas infected or malignant cells are identified and eliminated by the cellular immune system. To enable the recognition, proteins are cleaved into peptides in the cytosol and are presented on the cell surface by class I molecules of the major histocompatibility complex (MHC). The transport of the antigenic peptides into the lumen of the endoplasmic reticulum (ER) and loading onto the MHC class I molecules is an essential process for the presentation to cytotoxic T lymphocytes. The delivery of these peptides is performed by the transporter associated with antigen processing (TAP). TAP is a heterodimer of TAP1 and TAP2, each subunit containing transmembrane domains and an ATP-binding motif. Sequence homology analysis revealed that TAP belongs to the superfamily of ATP-binding cassette transporters. Loss of TAP function leads to a loss of cell surface expression of MHC class I molecules. This may be a strategy for tumors and virus-infected cells to escape immune surveillance. Structure and function of the TAP complex as well as the implications of loss or downregulation of TAP is the topic of this review.

Intratumoral delivery of an interferon gamma retrovirus-producing cells inhibits growth of a murine melanoma by a non-immune mechanism

Interferon gamma (IFNgamma) is a potent inhibitor of cell growth effective against a wide range of tumor-derived cell lines. We cloned murine IFNgamma cDNA into a retroviral vector and created a packaging cell line (Am-gamma) producing this IFNgamma-encoding retrovirus. In a pilot experiment, admixing and co-injection of equal numbers of retrovirus-producing and target B16 melanoma cells led to high rates of infection and strong suppression of neoplastic growth. This effect was observed in the absence of measurable systemic production of IFNgamma and could be reproduced in animals lacking cytotoxic immune responses. Tumor angiogenesis was unaffected and no increase in apoptosis was apparent; however, mitotic indices were greatly reduced in Am-gamma-containing abortive tumors. We thus concluded that IFNgamma directly affects proliferation of B16 cells. Indeed, exposure of B16 cells to IFNgamma in vitro inhibits cell division, as measured by a thymidine incorporation assay. Most importantly, repeated intratumoral injections of Am-gamma stunted growth of established B16 melanomas in 75% of treated animals. Thus, this approach can serve as a prototype for new anti-cancer modalities.

The genetic basis of renal epithelial tumors: advances in research and its impact on prognosis and therapy

The genetics of renal cell carcinoma continues to elucidate the pathways of kidney tumorigenesis. The relationship between the VHL gene and clear cell carcinoma, MET and papillary carcinoma, and the families of genes that they regulate, continues to be unraveled. New hereditary kidney cancer syndromes, like familial oncocytoma and the Birt-Hogg-Dubé syndrome, have been identified and the search for the genes that cause them is under way. Researching the genetics of these disorders is essential for an understanding of sporadic kidney cancer genetics. This chapter will review the current knowledge of the hereditary kidney cancer syndromes, the genes that cause them, new advances in genetic research and techniques, and how this information impacts upon diagnostic, prognostic, and therapeutic methods of the future.