Immunosuppression in murine renal cell carcinoma. I. Characterization of extent, severity and sources

Animal models of spontaneous renal carcinoma: A possible rebirth?

Introduction and Objectives The animal models for renal carcinogenesis have allowed researchers to better understand the physiopathological, genetic, molecular, and immunological mechanisms underlying the development of human renal cancers from the induction of precancerous lesions to the metastatic process. Our study aimed to review and discuss the characteristics of all the spontaneous animal models of renal carcinogenesis described in scientific literature to date and see how they could address future challenges in the field of personalized medicine. Methods and Materials We reviewed all the papers on PubMed which focus on spontaneous animal models of renal carcinogenesis. To do so, we used the keywords "spontaneous" AND "animal model" AND "renal cancer" in the PubMed search engine. We also conducted a search using the keywords "spontaneous" AND "animal model" AND "kidney cancer." PRISMA recommendations were used for the literature review. Results A total of 213 publications were found on PubMed with the keywords "spontaneous" AND "animal model" AND "kidney cancer." 219 publications were found on PubMed with the keywords "spontaneous" AND "animal model" AND "renal cancer." After pooling these 2 searches and removing the duplicate publications, 233 publications remained. Among these, 220 full-text articles were assessed for eligibility; 160 were removed because they were irrelevant to our topic, and the remaining 60 studies were included in our qualitative synthesis. Conclusions Many spontaneous animal models have been developed to study renal cancer. So far, these models have enabled the understanding of pathophysiological mechanisms underlying renal cancer. Though less appropriate than patient xenografts from the perspective of personalized medicine, we believe animal models can help medical professionals better understand the hows and whys of the genetic events underlying the intratumoral heterogeneity and spatial distribution of metastatic subclones.

Anti-tumor immunity and mechanism of immunosuppression mediated by tumor cells: role of tumor-derived soluble factors and cytokines

The immune system plays a crucial role in the protection against tumor growth and progression. However, the activation of the immune system against the neoplastic cells does not always occur and, therefore, tumor cells are able to grow and progress continually in the host. It has now been realized that tumor cells themselves produce many of the important factors that are responsible for dismounting of effective immune response. These tumor-derived soluble factors invariably subdue the functions of almost every immune cell population. Therefore, we attempted to underline the mechanism of anti-tumor immune response and immunosuppression induced by tumor cells.

DC immunotherapy is highly effective for the inhibition of tumor metastasis or recurrence, although it is not efficient for the eradication of established solid tumors

Dendritic cell (DC)-based immunotherapy has not been as effective as expected in most solid tumors even in the murine model, particularly in renal cell carcinoma (RCC). Our investigation was initiated to identify what causes the limitations of DC-based immunotherapy in solid RCC. We have investigated immunosuppressive factors from tumors and their effects on DC migration, as well as cytotoxic T lymphocyte (CTL) response and lymphocyte infiltration into the tumor mass upon vaccination with mouse renal adenocarcinoma (Renca) cell lysate-pulsed bone marrow (Bm)-derived DC in tumor-bearing mice. We also investigated pulmonary metastasis- and tumor recurrence-inhibitory effects of DC-vaccination in the solid tumor-bearing mice. In these experiments, we found that the limitations of DC-based immunotherapy to solid RCC likely result from tumor-mediated TGF-beta hindrance of immune attack rather than insufficient immune induction by DC therapy. In fact, the CTL response induced by DC therapy was quite sufficient and functional for the inhibition of tumor recurrence after surgery or of tumor metastasis induced by additional tumor-challenge to the tumor-bearing mice. Taken together, our present results obtained in mouse model suggest the potential of DC immunotherapy in tumor patients for hindering or blocking disease progression by inhibition of tumor metastasis and/or tumor recurrence after surgery.

Restoration of expression of transforming growth factor-beta type II receptor in murine renal cell carcinoma (renca) cells by 5-Aza-2'-deoxycytidine

The murine renal cell carcinoma (Renca) cells are insensitive to TGF-beta due to a lack of TGF-beta type II receptor (TbetaR-II). The objective of the present study is to determine the mechanism of this loss of sensitivity to TGF-beta in Renca cells. Renca cells were cultured and treated with 5-Aza-2'-Deoxycytidine (5-Aza), a specific inhibitor of methylation. Expression of TGF-beta type I receptor (TbetaRI) and TbetaRII was determined by RT-PCR and Western blot analysis before and after the treatment of Renca cells with 5-Aza. The expression of phosphorylated Smad2 (P-Smad2) was determined by Western blot analysis. TGF-beta levels in the conditioned medium were measured by ELISA. Renca cells did not express TbetaR-II prior to 5-Aza treatment. After 5-Aza treatment, these cells expressed TbetaR-II at both mRNA and protein levels, which corresponded to the restoration of sensitivity to TGF-beta by an increase in P-Smad2. Levels of TGF-beta1 were similar before and after 5-Aza treatment. Results of the present study indicated that, in Renca cells, the loss of sensitivity to TGF-beta is likely due to a promoter hypermethylation in the TbetaR-II gene.

Potentiation of a Dendritic Cell Vaccine for Murine Renal Cell Carcinoma by CpG Oligonucleotides

Purpose: An ideal vaccine therapy for tumors should activate both effector and memory immune responses against tumor-specific antigens. Here we investigated the effect of CpG oligodeoxynucleotides (CpG-ODN) for their ability to potentiate the activity of tumor antigen–pulsed bone marrow–derived dendritic cells (DC) in a vaccine model for the treatment of murine renal cell carcinoma (RENCA).

Experimental Design: First we evaluated the effects of a murine renal cell carcinoma (RENCA) on immune cell activity in a mouse model using in vitro assays for T-cell proliferation and natural killer cell activation. To overcome the immune suppression of the tumor, we s.c. injected groups of 10 mice with dendritic cells and tumor cells. We compared the effect of different conditioning regimens of the DCs with RENCA antigen and/or CpG-ODNs before injection by measuring tumor size twice a week.

Results: Tumor growth was shown to negatively affect spleen cell and T-cell proliferation, IFN-γ production, natural killer cell activity, and NF-κB activation in T cells. In this model, we have shown that RENCA-pulsed CpG-ODN-treated DCs were able not only to significantly reduce tumor growth but also to prevent tumor implantation in 60% of mice. Tumor-free mice were resistant to tumor challenge and the immunity conferred by the vaccine was transferable and tumor specific.

Conclusions: This data show that RENCA down-modulates the immune response, and DC vaccine therapy, in conjunction with CpG-ODN, can restore tumor-specific immunity.

Tumor gene therapy by MVA-mediated expression of T-cell-stimulating antibodies

Immune responses to tumor-associated antigens are often dampened by a tumor-induced state of immune anergy. Previous work has attempted to overcome tumor-induced T-cell anergy by the direct injection of vectors carrying the genes encoding one of a variety of cytokines. We hypothesised that the polyclonal stimulation of T cells, preferably through the TCR complex, would result in a cascade of cytokines associated with T-cell activation and would be best able to overcome T-cell anergy. Here we use the highly attenuated MVA poxvirus to express on tumor cells, in vitro and in vivo, either of three membrane-bound monoclonal antibodies specific for murine TCR complex. Using this system, we have expressed antibodies specific for the CD3 epsilon chain (KT3), TCR alpha/beta complex (H57-597), and V beta 7 chain (TR310). Tumor cells bristling with these antibodies are capable of inducing murine T-cell proliferation and cytokine production. When injected into growing tumors (P815, RenCa, and B16F10), these constructs induce the activation of immune effector cells and result in the rejection of the tumor. Histological and FACS analysis of tumor-infiltrating leukocytes reveal that the injection of recombinant virus-expressing antibodies specific for the TCR complex attracts and activates (CD25(+), CD69(+)) CD4 and CD8 lymphocytes. This approach represents a novel strategy to overcome T-cell anergy in tumors and allow the stimulation of tumor-specific T cells.

Murine renal cell carcinoma: evaluation of a dendritic-cell tumour vaccine

OBJECTIVE

To use a murine model of renal cell carcinoma (RCC), Renca, to aid in developing a dendritic cell (DC)-mediated tumour vaccine for RCC; as conventional therapy has been unsuccessful for RCC and therapy using immune modulators has had limited success, novel therapies enhancing further the immune system must be developed.

MATERIALS AND METHODS

DCs were obtained from mouse bone marrow enriched for the haematopoietic progenitors, and cultured in the presence of interleukin-4 and granulocyte macrophage-colony stimulating factor. In vivo vaccines and in vitro proliferation assays were used to assess ability of the DCs to present tumour antigen.

RESULTS

The presence of DCs was confirmed in the cultures by fluorescent-activated cell sorting analysis. In vivo, tumour-bearing animals receiving tumour extract-pulsed DCs as a vaccine showed a two to threefold reduction in tumour growth at day 12 and day 16 but no significant difference at day 28. In vitro, tumour extract-pulsed DCs stimulated significant proliferation of splenocytes from naive animals but not tumour-bearing animals. In addition, splenocytes from tumour-bearing animals had an attenuated immune response in vitro.

CONCLUSION

These results show that it is possible to use the DC vaccine to modulate the immune response to achieve an antitumour effect, but further manipulation of the DC vaccine may be needed to overcome the tumour-induced immune suppression.

Effect of tumor growth on the blastogenic response of splenocytes: a role of macrophage-derived nitric oxide

In vivo growth of Dalton's lymphoma (DL), a spontaneous T cell lymphoma, has been found to increase the count of peripheral blood leukocytes (PBL). However, bone marrow cell proliferation and differentiation remained unaffected (A. Kumar and S.M. Singh, Immunol. Cell Biol., 73, 220-225). The present investigations were undertaken to study the effect of DL growth on the blastogenic response of splenocytes. A decrease in the wet weight of the spleen and in the count of splenocytes was observed at the early DL-bearing stage which, however, increased through the mid and late stages of the tumor growth. In vitro, the blastogenic response of the splenocytes of DL-bearing mice to phytohemagglutinin (PHA) was low at the early stage of the tumor, and subsequently increased at the mid and late stages. Macrophage-derived nitric oxide (NO) was found to be involved in regulating the blastogenic response of the splenocytes. DL cells are thus shown to influence splenocyte blastogenesis by altering the NO production of splenic macrophages.

T cells from late tumor-bearing mice express normal levels of p56lck, p59fyn, ZAP-70, and CD3 zeta despite suppressed cytolytic activity

Loss of T cell-associated signal transduction molecules has recently been implicated in immune suppression in tumor-bearing hosts. In the present study, we have examined this and related phenomenon extensively in a large number of tumor-bearing mice, analyzed individually. Splenic T cells from tumor-bearing mice were isolated and characterized with respect to the following: (a) levels of three tyrosine kinases, p56lck, p59fyn, and ZAP-70; (b) expression of CD3-zeta; (c) alloreactive responses; and (d) antigen-specific responses. Contrary to recent reports, T cells from tumor-bearing mice were observed to express normal levels of lck, fyn, ZAP-70, and CD3-zeta. Further, T cells showed healthy alloreactive and antigen-specific responses until approximately 3 wk after post tumor challenge, when the tumors constituted approximately 20% of the body weight. Alterations with respect to some parameters were observed only in mice that had been bearing larger tumors for a considerably longer period. As human tumors are unlikely to grow to such large sizes (e.g., > 20% of the total body weight), the significance of the alterations in T cell expression of lck, fyn, ZAP-70, or CD3-zeta in the immune status of cancer patients is unclear. Altogether, these results indicate that alterations in T cell signal transduction molecules do not account for the profound tumor-specific suppression observed during tumor growth.

Delayed-type hypersensitivity response in experimental autoimmune neuritis treated with peptide-coupled spleen cells

Experimental autoimmune neuritis (EAN) is a T cell-mediated autoimmune inflammatory disease of the peripheral nervous system that is characterized by demyelination and mononuclear cell infiltration. It is induced in Lewis rats by administration of myelin P2 protein or a synthetic peptide (SP-26) corresponding to amino acid residues 53-78 of bovine P2 protein. Recently, we showed that SP-26, when coupled to syngeneic spleen cells and administered intravenously, provided an effective means of inducing tolerance by inhibiting the clinical signs, decreased proliferative response of lymphoid cells to SP-26 and histological changes of EAN. However, our current data indicate that, despite tolerance induction in these Lewis rats, the antigen-specific delayed-type hypersensitivity (DTH) response to SP-26 remained intact. Furthermore, interferon (IFN)-gamma production by spleen cells of tolerized rats were unchanged as compared to EAN rats. The in vitro proliferation of T lymphocytes from tolerized rats stimulated by SP-26 was reduced as compared to EAN controls but was enhanced upon addition of exogenous interleukin-2. Thus, reduction in EAN clinical signs does not necessarily indicate a decrease in DTH response and IFN-gamma production in EAN Lewis rats. The implication of this finding in regard to immunoregulatory mechanism of DTH response is discussed.

Chinese medicinal herbs inhibit growth of murine renal cell carcinoma

Tumors are known to produce factors suppressing immune functions. We previously showed that a murine renal cell carcinoma (Renca) suppressed macrophage function in vitro and that this suppression was abolished by co-incubation with extracts of two Chinese medicinal herbs. We now report that these phytochemicals are capable of inhibiting growth of Renca in vivo. BALB/c mice were transplanted intraperitoneally (IP) with 1-2 x 10(5) Renca cells. One day after tumor transplant, mice were randomized into two groups. One group was treated IP, daily for 10 days, with 100 microliters of phytochemicals containing 500 micrograms each of Astragalus membranaceus and Ligustrum lucidum, while the other group received saline as controls. A cure rate of 57% was obtained with these phytochemicals when the initial tumor load was 2 x 10(5), and 100% when the initial tumor load was 1 x 10(5). Additional experiments were performed to investigate the mechanisms involved in this protection. Splenic macrophages from tumor-bearing mice were shown to have depressed chemiluminescent oxidative burst activity, and this depression was restored with phytochemical treatment. Splenocytes from mice transplanted with Renca responded less favorably to interleukin-2 (IL-2) in generating lymphokine-activated killer (LAK) cells; again this depression was restored with phytochemical treatment. Our data suggest that these phytochemicals may have exerted their antitumor effects via augmentation of phagocyte and LAK cell activities.

Inhibition of interleukin-2 dependent immune responses by serum from patients with advanced gastrointestinal cancer

Immunotherapy with high-dose interleukin-2 (IL-2) fails to induce clinical responses in patients with advanced gastrointestinal cancer, but may be effective in patients with malignant melanoma or renal adenocarcinoma. The hypothesis that this failure may be related to immunosuppressive moieties present in patients with advanced gastrointestinal cancer was investigated. Serum samples from 93 patients (32 advanced gastrointestinal cancer, 22 localized gastrointestinal cancer, 13 melanoma/renal adenocarcinoma and 26 age-matched controls) were incubated with peripheral blood lymphocytes from healthy volunteers. The generation of cytolytic lymphokine-activated killer (LAK) cells and the allogeneic mixed lymphocyte response (MLR) were measured in-vitro. LAK effector cytotoxicity (mean % +/- SEM) was significantly (P < 0.05) decreased by serum from advanced gastrointestinal cancer patients (30 +/- 3) compared with that from controls (47 +/- 3), serum from patients with localized gastrointestinal cancer (49 +/- 2) or that from patients with melanoma or renal adenocarcinoma (51 +/- 2). MLR responses were also significantly (P < 0.05) decreased using advanced gastrointestinal cancer patients serum compared to controls. A dose-response phenomenon for suppression of MLR was observed. Serum from patients with melanoma or renal adenocarcinoma was not significantly different to control samples. The immunosuppressive properties of serum from patients with advanced gastrointestinal carcinoma may abrogate therapeutic attempts using IL-2.

MHC-specific graft-protective and delayed-type hypersensitivity (DTH) suppressive activity of a CD4+ CD8+, alpha beta T cell receptor (TCR) positive lymphoma isolated from a tolerant mouse

Two lymphomas were found in, and isolated from A (H-2a) mice in which permanent transplantation tolerance was induced to CBA (H-2k) histocompatibility antigens by the neonatal injection of (CBAxA)F1 spleen cells. They proved to be of recipient origin and were transferable to syngeneic A mice, growing as disseminated lymphomas (L33 and L46) and killing the recipients rapidly. Analysis of the cell surface antigens disclosed that both lymphomas had an immature T cell phenotype [Thy-1+, CD5+, CD3low, TCR alpha beta low, CD4low, CD8high, heat-stable antigen (HSA) positive, and CD44-, MHC class II-, CD45R-, sIg-, Gr-1-, CD11b-]. Intraperitoneal (i.p.) injection of syngeneic A mice with viable L33 lymphoma cells resulted in a dose-dependent, significant prolongation of the mean survival times of "specific" CBA and MHC-identical B10.BR skin allografts as compared to the survival of appropriate grafts in non-lymphoma-bearing controls. The survival times of third party MHC-incompatible B10 (H-2b) and B10.D2 (H-2d) allografts were only slightly prolonged in A mice inoculated with L33 cells. The graft-protective effect was not abrogated if the proliferative capacity of the L33 cells was blocked by in vitro mitomycin C (MMC) pretreatment. Furthermore, the inoculation of L33 lymphoma into A mice significantly inhibited their DTH response to the sensitizing CBA histocompatibility antigens. In contrast, the L46 lymphoma had no effect on the survival of CBA allografts and the DTH reactivity. These data suggest that the CD4+CD8+TCR alpha beta + L33 T cell lymphoma originating from a neonatally tolerant mouse has a specific immunosuppressive effect on the in vivo reactivity of syngeneic mice to the tolerance-inducing (MHC class I) alloantigens.

Synergy of radiation therapy and immunotherapy in murine renal cell carcinoma

The treatment of metastatic renal cell carcinoma with immunotherapy has resulted in objective anti-tumor responses in 15-30% of patients. To enhance the therapeutic effects of immunotherapy, it is becoming evident that this approach should be combined with other treatment modalities. In this study, a spontaneously metastasizing murine renal adenocarcinoma (Renca), transplanted under the renal capsule, was treated with either radiation therapy, immunotherapy or a combination of both. In order to distinguish between the local and systemic effects of radiation therapy, total body irradiation was compared to irradiation of the tumor-bearing kidney only, or irradiation of the whole mouse with the tumor-bearing kidney shielded. Immunotherapy was administered with interleukin-2 (IL-2) alone or with IL-2 and lymphokine activated killer (LAK) cells. Combined radiation and immunotherapy induced a better anti-tumor response than either modality alone. The best response was obtained by local tumor irradiation and IL-2 therapy and resulted in a significant reduction in primary tumor size, elimination of lung metastases and a significant increase in survival.

Immunosuppression in murine renal cell carcinoma. II. Identification of responsible lymphoid cell phenotypes and examination of elimination of suppression

In our companion paper we have reported that cell-mediated immunity of mice bearing renal cell carcinoma is profoundly suppressed. The non-responsiveness of such animals was found to be attributable to Renca cells themselves and to splenic lymphoid cells that down-regulate other fully capable lymphoid cells. In this communication the lymphoid cell source of suppression within Renca-bearing mice has been explored with the aim of identifying phenotypes of the responsible cells, the manner by which suppression is mediated, and initial ways by which suppression may be eliminated. A plastic-adherent cell bearing the Thy1.2 surface marker as well as the Lyt1 and Lyt2 antigens has been found to operate, perhaps in conjunction with macrophages, to down-regulate lymphokine-activated killer (LAK) cell development for natural killer (NK) and non-NK targets that include Renca cells themselves. The splenic suppressor cells lost the capacity to suppress the NK response of normal recipient mice upon shallow irradiation (250 rad) prior to adoptive transfer. Spleen cells, presumably macrophages, from Renca-bearing mice were found to suppress the generation of LAK and NK cells in vitro by synthesizing prostaglandins. Indomethacin, a prostaglandin synthetase inhibitor, blocked the induction of suppression both in vitro and in vivo, suggesting the presence of endogenous prostaglandins in Renca-bearing mice. The suppression seen in Renca-bearing mice that derives from multiple sources and has been prevented by two separate methods has been discussed from the viewpoint of the inter-relatedness of the sources.