Synergy of radiation therapy and immunotherapy in murine renal cell carcinoma

Choosing The Right Animal Model for Renal Cancer Research

The increase in the life expectancy of patients with renal cell carcinoma (RCC) in the last decade is due to changes that have occurred in the area of preclinical studies. Understanding cancer pathophysiology and the emergence of new therapeutic options, including immunotherapy, would not be possible without proper research. Before new approaches to disease treatment are developed and introduced into clinical practice they must be preceded by preclinical tests, in which animal studies play a significant role. This review describes the progress in animal model development in kidney cancer research starting from the oldest syngeneic or chemically-induced models, through genetically modified mice, finally to xenograft, especially patient-derived, avatar and humanized mouse models. As there are a number of subtypes of RCC, our aim is to help to choose the right animal model for a particular kidney cancer subtype. The data on genetic backgrounds, biochemical parameters, histology, different stages of carcinogenesis and metastasis in various animal models of RCC as well as their translational relevance are summarized. Moreover, we shed some light on imaging methods, which can help define tumor microstructure, assist in the analysis of its metabolic changes and track metastasis development.

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.

Previous Radiotherapy Increases the Efficacy of IL-2 in Malignant Pleural Effusion: Potential Evidence of a Radio-Memory Effect?

Preclinical and clinical studies have shown that prior receipt of radiotherapy enhances antitumor immune responses, a phenomenon we call the “radio-memory effect.” However, all of the evidence regarding this effect to date comes from work with PD1/PDL1 inhibitors. Here we explored whether this effect also occurs with other forms of immune therapy, specifically interleukin-2 (IL-2). We retrospectively assessed outcomes in patients with malignant pleural effusion (MPE) who had previously received radiotherapy for non-small-cell lung cancer (NSCLC) within 18 months before the intrapleural infusion of IL-2 or cisplatin. Radiotherapy sites included lungs, thoracic lymph nodes, and intracranial. All patients received intrapleural infusion of IL-2 or cisplatin, and most had had several cycles of standard chemotherapy for NSCLC. We identified 3,747 patients with MPE (median age 64 years [range 29–88)) treated at one of several institutions from August 2009 through February 2015; 642 patients had been treated with IL-2 and 1102 with cisplatin and had survived for at least 6 months afterward. Among those who received IL-2, 288 had no radiotherapy, 324 had extracranial (i.e., thoracic) radiotherapy, and 36 had intracranial radiotherapy. The median follow-up time for surviving patients was 38 months. Patients who had received extracranial radiotherapy followed by IL-2 had significantly longer PFS than patients who had not received extracranial radiotherapy (i.e., either no radiotherapy or intracranial radiotherapy). Patients who had received intracranial or extracranial radiotherapy followed by IL-2 had significantly longer OS than did other patients. No survival advantage was noted for prior radiotherapy among patients who received intrapleural cisplatin. We speculate that previous radiotherapy could enhance the efficacy of subsequent intrapleural infusion of IL-2, a “radio-memory” effect that could be beneficial in future studies.

Immunotherapy with radiotherapy in urological malignancies

PURPOSE OF REVIEW

Radiotherapy has the potential to augment the host's immune response to cancer. Urological malignancies are highly immunogenic and the combination of radiotherapy and immunotherapy shows promise. In this review, we discuss the effects of radiotherapy on the cancer immune system and highlight the rationale for using the combined approach in prostate, urothelial and renal cancers. Current clinical studies are summarized emphasising the synergistic effects of the combination and the possibility of improved clinical outcomes.

RECENT FINDINGS

Local and abscopal effects have been observed in different urological cancers when using a combined approach. Large fraction size is associated with an increased immune response. Multiple radiotherapy/immunotherapy combinations are being studied in several clinical trials although no combination has yet been introduced in to standard practice.

SUMMARY

Although our knowledge of immunomodulation by radiotherapy has improved significantly in recent times, there remain several unanswered questions regarding how to best use the combination in clinical practice. Ongoing trials will provide further insight into complex mechanisms governing radiotherapy-immunotherapy interactions, with potential to improve clinical outcomes.

The Abscopal Effect of Radiation Therapy: What Is It and How Can We Use It in Breast Cancer?

The abscopal effect refers to the ability of localized radiation to trigger systemic antitumor effects. Over the past 50 years, reports on the abscopal effect arising from conventional radiation have been relatively rare. However, with the continued development and use of immunotherapy strategies incorporating radiotherapy with targeted immunomodulators and immune checkpoint blockade, the abscopal effect is becoming increasingly relevant in less immunogenic tumors such as breast cancer. Here, we review the mechanism of the abscopal effect, the current preclinical and clinical data, and the application of the abscopal effect in designing clinical trials of immunotherapy combined with radiotherapy in breast cancer.

Clinical outcome of high-dose bolus intravenous interleukin-2 with a modified administration schedule for Asian patients with metastatic renal cell carcinoma

PURPOSE

The standard regimen of high-dose interleukin-2 (HDIL-2) for metastatic renal cell carcinoma (RCC) is two cycles separated by 9 days, which constitutes one course. Each course is separated by an 8-12 weeks. However, the 9-day interval between each HDIL-2 cycle is often not long enough to allow recovery from adverse effects. Therefore, we modified HDIL-2 schedules by increasing the interval between each cycle without changing the total cumulative doses of IL-2.

METHODS

Clinical data from 37 patients who were treated with modified HDIL-2 schedule were reviewed. Patients received the first dose of IL-2 on day 1 and took subsequent doses every 8 h for a maximum of 14 doses each cycle. Treatment was repeated every 4 weeks, and a maximum of six cycles were planned.

RESULTS

The overall response rate was 35% including two patients with complete response. With a median follow-up duration of 46.9 months, median progression-free survival was 16.0 months (95% CI 10.2-21.7 months) and median overall survival was 58.9 months (95% CI 49.6-68.3 months) with a 3-year overall survival rate of 77.8%. Toxicity profile was acceptable and comparable to standard HDIL-2 schedule. There were no treatment-related mortalities. The incidence of ≥grade 3 adverse events did not differ between patients who had prior exposure to vascular endothelial growth factor receptor tyrosine kinase inhibitor (VEGFR TKI) and VEGFR TKI-naïve patients.

CONCLUSION

Modified HDIL-2 schedule seems to be a safe and effective option for selected Asian patients with metastatic RCC, even in patients with prior VEGFR TKI treatment.

Stereotactic Ablative Radiotherapy for the Treatment of Clinically Localized Renal Cell Carcinoma

Thermal ablation is currently the most studied treatment option for medically inoperable patients with clinically localized renal cell carcinoma (RCC). Recent evidence suggests that stereotactic ablative radiotherapy (SABR) may offer an effective noninvasive alternative for these patients. In this review, we explore the current literature on SABR for the primary treatment of RCC and make recommendations for future studies so that an accurate comparison between SABR and other ablative therapies may be conducted.

Intratumoral injection of interleukin-2 augments the local and abscopal effects of radiotherapy in murine rectal cancer

Recent studies have suggested that tumor shrinkage in response to radiotherapy (RT) is greatly dependent on the host immune response. A Balb/c mouse model of simultaneous subcutaneous tumor and liver metastasis of Colon26 was prepared and, after irradiation of the subcutaneous tumor (2 Gy × 5 day × 2 cycles), interleukin-2 (IL-2) (2 × 10(4) U) was injected intra-tumorally, and the fate of both the subcutaneous tumor and liver metastatic lesions was evaluated. Intratumoral injection of IL-2 greatly enhanced the anti-tumor effects of RT and completely eradicated the established subcutaneous tumor. Interestingly, although RT was given locally to the subcutaneous tumor, liver metastasis formation was also inhibited in mice receiving only local RT. More impressively, the combination of RT + IL-2 completely inhibited liver metastasis formation. Splenocytes in mice receiving RT + IL-2 contained a higher percentage of CD4(+) T cells, but lower percentages of CD4(+)CD25(+) regulatory T cells and CD11b(+) Gr-1(+) myeloid-derived suppressor cells. Immunohistochemical investigation of human rectal cancer revealed that the density of CD8(+) cells infiltrating into irradiated rectal tumor was positively associated with a lower frequency of distant metastasis as well as histological response grade. Local administration of IL-2 not only enhances shrinkage of the irradiated tumor itself, but can also suppress the development of distant metastasis located outside the RT field, possibly though the induction of a systemic T cell response. Augmentation of T-cell-mediated antitumor immunity during RT might be critical for improvement of the clinical efficacy of neoadjuvant RT for the treatment of advanced rectal cancer.

Combination approaches to immunotherapy: the radiotherapy example

The marquee cell of the immune response, the T lymphocyte, is exquisitely sensitive to ionizing radiation. Moreover, the majority of cells of the hematopoietic lineage, with their high turnover and radiation sensitivity, are effectively ablated by relatively low radiation doses, such that total-body irradiation is an effective immunosuppressive therapy. Despite and sometimes because of these facts, the immune system may underlie some portion of the therapeutic effects of radiation. In this review, we will discuss these processes, and go on to discuss current therapies combining radiation therapy with immunotherapy for the treatment of cancer.

Treatment of transforming growth factor-beta-insensitive mouse Renca tumor by transforming growth factor-beta elimination

OBJECTIVES

The mouse renal cell carcinoma line, Renca, is insensitive to transforming growth factor-beta (TGF-beta) in vitro. The present study was conducted to determine whether removal of TGF-beta from these tumor cells would inhibit tumor progression in vivo.

METHODS

TGF-beta elimination was accomplished either by administration of neutralizing TGF-beta antibody into mice receiving intravenous injection of Renca tumor cells or infection of TGF-beta antisense expression vector into these tumor cells before subcutaneous injection into recipient mice.

RESULTS

Although a low dose of TGF-beta antibody (5 mg/kg every 3 days) was without any effect, a high dose of TGF-beta antibody (50 mg/kg every 3 days), administered to recipient mice, resulted in a significant reduction in lung metastasis and was accompanied by increased apoptosis in the tumor cells. When the tumor cells were transfected with a TGF-beta1 antisense expressing vector, a significant reduction occurred in the tumor incidence, as well as the tumor burden. However, in nude mice, cells with reduced TGF-beta1 production grew almost as well as did the unmodified Renca cells, suggesting that the host's immune system might play an antitumor role.

CONCLUSIONS

These results indicate that progression of Renca tumor can be inhibited by eliminating TGF-beta from the tumor cells. Our results also suggest that, although insensitive to TGF-beta under in vitro conditions, Renca tumors could be inhibited by TGF-beta removal through the systemic host environment.

Combination tumor immunotherapy with radiotherapy and Th1 cell therapy against murine lung carcinoma

Mice bearing established Lewis lung carcinoma (LLC) expressing model tumor antigen, ovalbumin (OVA) (LLC-OVA) marginally responded to local radiotherapy, but none of the mice was cured. In contrast, treatment of the tumor-bearing mice with intratumoral injection of tumor-specific T helper type 1 (Th1) cells and tumor antigen (OVA) after radiotherapy dramatically prolonged the survival days and induced complete cure of the mice at high frequency (80%). Radiation therapy combined with Th1 cells or OVA alone showed no significant therapeutic activity against LLC-OVA. Such a strong therapeutic activity was not induced by intratumoral injection of Th1 cells plus OVA. Compared with other treatment, radiation therapy combined with Th1 cells and OVA was superior to induce the generation of OVA/H-2(b) tetramer(+) tumor-specific cytotoxic T lymphocyte (CTL) with a strong cytotoxicity against LLC-OVA in draining lymph node (DLN). Moreover, the combined therapy is demonstrated to inhibit the growth of tumor mass, which grew at contralateral side. These results indicated that radiotherapy combined with Th1 cell/vaccine therapy induced a systemic antitumor immunity. These findings suggested that combination therapy with radiotherapy and Th1 cell/vaccine therapy may become a practical strategy for cancer treatment.

CXCR3/CXCR3 ligand biological axis impairs RENCA tumor growth by a mechanism of immunoangiostasis

Metastatic renal cell carcinoma (RCC) responds poorly to chemo- or radiation therapy but appears to respond to systemic immunotherapy (i.e., IL-2 and/or IFN-alpha), albeit with only 5-10% durable response. The CXCR3/CXCR3 ligand biological axis plays an important role in mediating type 1 cytokine-dependent cell-mediated immunity, which could be beneficial for attenuating RCC if optimized. We found that systemic IL-2 induced the expression of CXCR3 on circulating mononuclear cells but impaired the CXCR3 ligand chemotactic gradient from plasma to tumor by increasing circulating CXCR3 ligand levels in a murine model of RCC. Moreover, the antitumor effect of systemic IL-2 was CXCR3-dependent, as IL-2 failed to inhibit tumor growth and angiogenesis in CXCR3-/- mice. We hypothesized that the immunotherapeutic effect of the CXCR3/CXCR3 ligand biological axis could be optimized by first priming with systemic IL-2 to induce CXCR3 expression on circulating mononuclear cells followed by enhancing the intratumor CXCR3 ligand levels to establish optimal CXCR3-dependent chemotactic gradient. We found that combined systemic IL-2 with an intratumor CXCR3 ligand (CXCL9) lead to significantly greater reduction in tumor growth and angiogenesis, increased tumor necrosis, and increased intratumor infiltration of CXCR3+ mononuclear cells, as compared with either IL-2 or CXCL9 alone. The enhanced antitumor effect of the combined strategy was associated with a more optimized CXCR3-dependent chemotactic gradient and increased tumor-specific immune response. These data suggest that the combined strategy of systemic IL-2 with intratumor CXCR3 ligand is more efficacious than either strategy alone for reducing tumor-associated angiogenesis and augmenting tumor-associated immunity, the concept of immunoangiostasis.

Multifocal metastases of recurrent renal cell carcinoma successfully treated with a combination of low dose interleukin-2, alpha-interferon and radiotherapy

A 59-year-old man presented with a 2-month history of left flank pain and a possibility of gross hematuria. Left renal cell carcinoma stage II was diagnosed and radical left nephrectomy was performed. Twenty-two months postoperatively, lung metastases were demonstrated and 6 x 10(6) units of alpha-interferon (IFN-alpha) were administered for 9 months, only to keep the sizes of the metastases unchanged. Thirty-four months after the operation, liver metastases and bone metastasis in the left sacroiliac joint were revealed. The combination cytokine therapy was performed with 1.4 x 10(6) U of interleukin-2 (IL-2) and 3 x 10(6) U of IFN-alpha for 16 weeks, and the left sacroiliac joint metastasis was treated with radiation therapy of 4 Gy per day for 7 days. Six months after the 16 weeks of immunotherapy, computed tomography and bone scintigraphy revealed that the metastases of the lung, liver and bone substantially disappeared and this complete response is still kept after 16 months.

Treatment of bone metastases and local recurrence from renal cell carcinoma with immunochemotherapy and radiation

Immunotherapies using interferons and/or interleukins are currently the treatment of choice for metastatic renal cell carcinoma (RCC). Bone metastases and non-resectable local recurrence are negative predictors for successful immunotherapy and signs of poor prognosis. The present study was designed to evaluate the effectiveness of combined immunochemotherapy (ICT) and radiation therapy (RT) for bone metastases or local recurrence from RCC in a prospective fashion. From September 1997 to September 1999, 20 patients with progressive RCC were treated with a combination of RT and ICT [s.c. interleukin-2a (IL-2), s.c. interferon alpha (IFN-alpha) and i.v. 5-fluorouracil]. RT started in week 2 of ICT. The radiation field was limited to the symptomatic bone metastases (15 patients) or the local recurrence (five patients). The total dosages of the RT ranged between 45 and 50 Gy, administered in fractions of from 1.8 to 2 Gy daily. In case of objective response or stable disease, the patients received up to two further ICT courses. All patients had good pain relief. Three out of 20 achieved complete remission, three had a partial remission, nine were stable and five patients had progressive disease under the combined treatment. Median survival was 21 months, mean survival 24 months (range: 5-59 months). The side effects of the combined treatment are in the same range as with ICT alone (World Health Organisation grade 2 and 3). Of 20 patients, 19 had their pain medication reduced after treatment. The combination of ICT and RT is feasible. There is remarkable pain relief. Our data suggest that the combination of immunochemotherapy and radiation therapy may induce a synergistic antitumor effect for the treatment of bone metastases or local recurrence from RCC compared to data from the literature for ICT or RT alone.

Tumor irradiation followed by intratumoral cytokine gene therapy for murine renal adenocarcinoma

To circumvent the toxicity caused by systemic injection of cytokines, cytokine cDNA genes encoding the human interleukin IL-2 cDNA (Ad-IL-2) and murine interferon IFN-gamma gene (Ad- IFN-gamma) were inserted into adenoviral vectors. These constructs were used for intratumoral gene therapy of murine renal adenocarcinoma Renca tumors. Treatment with three doses of Ad-IL-2 or Ad- IFN-gamma, given a day apart, was more effective than single-dose gene therapy. We found that tumor irradiation enhanced the therapeutic efficacy of Ad-IL-2 and Ad-IFN-gamma intratumoral gene therapy. Tumor irradiation, administered 1 day prior to three doses of Ad-IL-2 treatment, was more effective than radiation or Ad-IL-2 alone, resulting in tumor growth arrest in all mice, increased survival and a consistent increase in complete tumor regression response rate. Complete responders rejected Renca tumor challenge and demonstrated specific cytotoxic T-cell activity, indicative of specific tumor immunity. The effect of radiation combined with three doses of Ad-IFN-gamma was less pronounced and did not lead to tumor immunity. Histological observations showed that irradiation of the tumor prior to gene therapy increased tumor destruction and inflammatory infiltrates in the tumor nodules. These findings demonstrate that tumor irradiation improves the efficacy of Ad-IL-2 gene therapy for induction of antitumor immune response.

Ionizing radiation inhibition of distant untreated tumors (abscopal effect) is immune mediated

PURPOSE

Ionizing radiation can reduce tumor growth outside the field of radiation, known as the abscopal effect. Although it has been reported in multiple malignancies, the abscopal effect remains a rare and poorly understood event. Ionizing radiation generates inflammatory signals and, in principle, could provide both tumor-specific antigens from dying cells and maturation stimuli that are necessary for dendritic cells' activation of tumor-specific T cells. We therefore tested the hypothesis that the abscopal effect elicited by radiation is immune mediated. This was directly tested by enhancing the number of available dendritic cells using the growth factor Flt3-Ligand (Flt3-L).

METHODS AND MATERIALS

Mice bearing a syngeneic mammary carcinoma, 67NR, in both flanks were treated with Flt3-L daily for 10 days after local radiation therapy (RT) to only 1 of the 2 tumors at a single dose of 2 or 6 Gy. The second nonirradiated tumor was used as indicator of the abscopal effect. Data were analyzed using repeated measures regression.

RESULTS

RT alone led to growth delay exclusively of the irradiated 67NR tumor, as expected. Surprisingly, growth of the nonirradiated tumor was also impaired by the combination of RT and Flt3-L. As control, Flt3-L had no effect without RT. Importantly, the abscopal effect was shown to be tumor specific, because growth of a nonirradiated A20 lymphoma in the same mice containing a treated 67NR tumor was not affected. Moreover, no growth delay of nonirradiated 67NR tumors was observed when T cell deficient (nude) mice were treated with RT plus Flt3-L.

CONCLUSIONS

These results demonstrate that the abscopal effect is in part immune mediated and that T cells are required to mediate distant tumor inhibition induced by radiation.

Murine animal model

Experimental animal models are available for the development of new treatment. Murine animal models have particular advantages for comparative study to evaluate the efficacy and safety of different treatment modalities because many mice can be treated at the same time with easy handling. Among several experimental models, murine renal carcinoma (Renca), which arises spontaneously in Balb/c mice, is the most frequently used for the assessment of chemotherapy, immunotherapy, and radiotherapy. Renca cells readily establish tumors in isogenic mice, producing histologically proven adenocarcinoma with a predictable growth rate to mimic the clinical situation for orthotopic growth and metastasis in a reasonable time frame. Because of its poor immunogenicity and its responsiveness to immunotherapy, the number of studies using cytokine gene-modified tumor vaccines-such as interferon-alpha or interleukin-2-in the Renca system is growing. Therefore, Renca experiments greatly contribute to the analysis of the mechanisms of antitumor immune response. In this chapter, we describe several experimental systems using this Renca model.

Local low-dose interleukin-2 induces systemic immunity when combined with radiotherapy of cancer. A pre-clinical study

Tumor recurrence and outgrowth of metastases limit the therapeutical effect of radiotherapy. We have tested whether these problems can be overcome by supplementing radiotherapy with locoregional interleukin-2 (IL-2) treatment. The SL2 lymphoma and the M8013 mammary carcinoma were used. Mice bearing a 10-day-old s.c. tumor were locally irradiated and were treated daily with IL-2 peritumorally for 5 or 10 days. Low-dose IL-2 therapy improved local response (LR) and increased disease-free survival (DFS) in both tumor models following either single-dose irradiation or fractionated irradiation. For example, 93% of SL2-bearing mice treated with single-dose irradiation and 10 days of IL-2 experienced long-term DFS, compared with 17% for irradiation alone (p < 0.0001). Additionally, treatment of one tumor with irradiation +IL-2 led to anti-tumor effects in a second, untreated tumor in 80% of SL2-bearing mice. LR was increased to 100% and DFS to 70% when the second, non-irradiated tumor was also treated with peritumoral IL-2. We conclude that supplementing local radiotherapy with low doses of IL-2 results in increased local tumor control and regression of distant, non-irradiated tumors. This type of radioimmunotherapy is a promising new approach for the clinic.

Radiation-induced effects on murine kidney tumor cells: role in the interaction of local irradiation and immunotherapy

Local tumor irradiation enhances the effect of interleukin-2 (IL-2) therapy in the Renca murine renal adenocarcinoma model. To investigate the mechanism(s) of this interaction, we studied the in vitro and in vivo effects of irradiation on the tumor cells. Tumor cells from in situ irradiated renal tumors had diminished proliferation in vitro. A similar growth inhibition was noted following injection of irradiated Renca cells into naive mice, but this effect could be overcome by injecting more cells. Histologic evaluation of tumors derived from irradiated cells revealed a decrease in mitosis and an increase in multinucleated giant cells, apoptosis and micronecrosis. The presence of irradiated tumor reduced the growth of nonirradiated tumor cells when both were injected into separate flanks of the same animal, suggesting that irradiated tumor cells may trigger a systemic antitumor response. Interleukin-2 therapy given after injection of irradiated tumor cells caused a significant increase in leukocytic infiltrates and micronecrosis. Our findings indicate that radiation directly affects tumor growth and induces a systemic mechanism which could be enhanced by IL-2.

Intralesional treatment of established murine primary renal tumor with interleukin-4: localized effect on primary tumor with no impact on metastases

In an effort to develop new strategies for immunotherapy of metastatic renal cell carcinoma, we investigated the therapeutic potential of interleukin-4 in a visceral renal tumor using the murine Renca renal adenocarcinoma model. Renca cells were implanted underneath the renal capsule of Balb/c mice to induce a primary tumor that spontaneously metastasized to several organs. Established primary renal tumors 4 to 6 mm. in diameter were treated by intralesional administration of recombinant murine interleukin-4 (IL-4). This treatment caused a marked inhibition of the primary tumor growth but had little effect on the progression of metastases in the liver, mesentery and lungs. Immunohistochemistry studies performed on renal tumor sections showed a macrophage infiltration that became predominant 7 days after IL-4 treatment. CD8+ T cells were also observed at the periphery and within the tumor. These data suggest that IL-4 mediated a potent antitumor effect when administered intralesionally although its effects remained localized with no impact on metastases at distant sites. Interleukin-4 antitumor activity seems to be mediated by recruitment of macrophages and T cells in the tumor.

Systemic treatment with interleukin-4 induces regression of pulmonary metastases in a murine renal cell carcinoma model

Advanced metastatic renal cell carcinoma has been shown to be responsive to immunotherapy but the response rate is still limited. We have investigated the therapeutic potential of systemic interleukin-4 (IL-4) administration for the treatment of pulmonary metastases in the murine Renca renal adenocarcinoma model. Renca cells were injected iv in Balb/c mice to induce multiple pulmonary tumor nodules. From Day 5, Renca-bearing mice were treated with two daily injections of recombinant murine IL-4 for 5 consecutive days. IL-4 treatment induced a significant reduction in the number of lung metastases in a dose-dependent manner and significantly augmented the survival of treated animals. Immunohistochemistry studies, performed on lung sections, showed macrophage and CD8+ T cell infiltration in the tumor nodules 1 day after the end of IL-4 treatment. The CD8 infiltration increased by Day 7 after IL-4 treatment. Granulocyte infiltration was not detectable. To clarify further the role of the immune system in IL-4 anti-tumor effect, mice were depleted of lymphocyte subpopulations by in vivo injections of specific antibodies prior to treatment with IL-4. Depletion of CD8+ T cells or AsGM1+ cells abrogated the effect of IL-4 on lung metastases, whereas depletion of CD4+ T cells had no impact. These data indicate that CD8+ T cells and AsGM1+ cells are involved in IL-4-induced regression of established renal cell carcinoma.