Therapy of bovine ocular squamous-cell carcinoma with local doses of interleukin-2: 67% complete regressions after 20 months of follow-up

Treatment of equine sarcoids using recombinant poxviruses expressing feline interleukin-2

BACKGROUND

Interleukin (IL)-2 stimulates antitumour immunity and is successfully used for the treatment of different neoplasias.

HYPOTHESIS/OBJECTIVES

Canarypox virus locally expressing feline IL-2 is safe and can be used to treat equine sarcoids.

ANIMALS

Twenty horses of different breeds with a median age of eight years (interquartile range 6.0-13.3 years) and a total number of 59 sarcoids were included in the study.

METHODS

In this prospective clinical trial, sarcoids were injected twice seven days apart, with a recombinant canarypox virus expressing feline IL-2. Complete blood counts (CBC) and fibrinogen levels were measured before treatment and on days 1, 2, 7 and 8.

RESULTS

Complete regression was achieved in eight horses (40%) and partial regression in two horses (10%). No change in sarcoid size was observed in two horses (10%) and the disease progressed in five horses (25%). Sarcoids of three horses (15%) showed initial response followed by tumour growth. There were no significant changes in CBC and fibrinogen levels after either injection. One horse developed a mild fever the day after each injection, which subsided without treatment the following day.

CONCLUSIONS

Treatment of equine sarcoids with recombinant canarypox virus expressing feline IL-2 seems to be a safe therapy option. Although the expression of IL-2 after vector injection and its biological activity in horses were not proven in this study, the treatment resulted in regression and partial regression in 50% of the cases. Further studies are necessary to verify these findings and to establish a treatment protocol.

Elucidating the Immune-Related Mechanisms by Which Probiotic Strain Lactobacillus casei BL23 Displays Anti-tumoral Properties

We have recently described antitumor properties of Lactobacillus casei BL23 strain in both a mouse allograft model of human papilloma virus (HPV)-induced cancer and dimethylhydrazine-associated colorectal cancer. However, the mechanisms underlying these beneficial effects are still unknown. Interestingly, in vitro cellular models show that this bacterium is able to stimulate the production of high levels of IL-2. Because this cytokine has well-known antitumor properties, we decided to explore its role in the anti-cancer effects of BL23 using the HPV-induced cancer model. We found a negative correlation between IL-2 and tumor size confirming the necessity of IL-2 to protect from tumor development. Then, we blocked IL-2 synthesis using neutralizing monoclonal antibodies in mice that were challenged with lethal levels of tumor cells; this led to a significant reduction in the protective abilities of BL23. Next, we used a genetically modified strain of Lactococcus lactis to deliver exogenous IL-2 to the system, and in doing so, we were able to partially mimic the antitumor properties of BL23. Additionally, we showed the systemic role of T-cells in tumor protection through a negative correlation between tumor size and T-cells subpopulations and an increasement of BL23-specific local Foxp3 levels in tumor-bearing mice. Finally, we observed a negative correlation between tumor size and NK+ cells, but local recruitment of NK cells and cytotoxic activity appeared specific to BL23 treatment. Taken together, our data suggest that IL-2 signaling pathway plays an important role in the anti-tumoral effects of probiotic strain L. casei BL23. These results encourage further investigation in the use of probiotic strains for potential therapeutic applications to clinical practice, in particular for the treatment of colorectal cancer. Furthermore, our approach could be extended and applied to other potential beneficial microorganisms, such as gut microbiota, in order to better understand the crosstalk between microbes and the host.

In vivo model for mastocytosis: A comparative review

Human mastocytosis are heterogeneous group of neoplastic diseases characterized by a different degree of uncontrolled mast cell (MC) proliferation and activation. Interestingly, human mastocytosis share several biological and clinical features with canine mast cell disorders, so called canine mast cell tumors (CMCTs). These CMCTs are the most common spontaneous cutaneous tumors found in dogs representing a valid model to study neoplastic mast cell disorders. It has been discovered that the pathological activation of c-Kit receptor (c-KitR), expressed by MCs, has been involved in the pathogenesis of neoplastic MC disorders. In this review we have focused on human mastocytosis in terms of: (i) epidemiology and classification; (ii) pathogenesis at molecular levels; (iii) clinical presentation. In addition, we have summarized animal models useful to study neoplastic MC disorders including CMCTs and murine transgenic models. Finally, we have revised therapeutic approaches mostly common in human and canine MCTs and novel tyrosine kinase inhibitors approved for CMCTs and recently translated in human clinical trials.

Bovine ocular squamous cell carcinoma

Ocular squamous cell carcinoma (OSCC) in animals is a primary neoplasm of epithelial origin. OSCC or "cancer eye" is the most common malignant tumor affecting cattle in North America and is responsible for significant economic losses. In the United States, the prevalence of OSCC varies geographically and is higher in the southwestern region and in lower latitudes with higher levels of sunlight. Control of this disease would be of considerable significance to the economics and profitability of the beef and dairy cattle industries. This article reviews the characteristics of the most commonly affected animals, the factors that are believed to contribute to the development of OSCC, and the treatment options that have been proposed.

Clinical application of dendritic cells and interleukin-2 and tools to study activated T cells in horses--first results and implications for quality control

Dendritic cells (DCs) are antigen-presenting cells, which are well known for their capacity to stimulate immunity. The ex vivo generation of myeloid DC from monocytes has facilitated the development of DC-vaccination protocols which have been extensively evaluated in tumour immunology and are regarded by some as a gold mine for clinical research. However, there is a considerable amount of work required to overcome the potential risks associated with such therapy. It is therefore mandatory to characterize the system to be applied and to study the reactions, particularly at the level of T cell responses. The first objective of the current study was to test if tumour lysates loaded autologous DC or recombinant human IL-2 are well tolerated in horses and performed an exploratory phase I study on equine sarcoids and squamous cell carcinomas. We consequently intended to establish a robust protocol for the magnetic separation of monocytes such as in use in human clinical studies. Finally we intended to address the limits in the reagents to study equine T cell based immune reactions, and analysed markers for CD25 and FoxP3. The data showed that local application of DC or IL-2 did not cause side effects. Additionally our data show that a polyclonal approach to detect antigens such as CD25 might be successful, where mAbs are not available. Our data also demonstrate that the mAb FJK16s, which has been used successfully in rodents, humans, and dogs, can also be applied in horses. We finally wish to share our concerns regarding quality control for clinical studies and encourage multi-central studies such as in human medicine to ensure that progress along established standards is made for the benefit of veterinary medicine.

Local therapy of cancer with free IL-2

This is a position paper about the therapeutic effects of locally applied free IL-2 in the treatment of cancer. Local therapy: IL-2 therapy of cancer was originally introduced as a systemic therapy. This therapy led to about 20% objective responses. Systemic therapy however was very toxic due to the vascular leakage syndrome. Nevertheless, this treatment was a break-through in cancer immunotherapy and stimulated some interesting questions: Supposing that the mechanism of IL-2 treatment is both proliferation and tumoricidal activity of the tumor infiltrating cells, then locally applied IL-2 should result in a much higher local IL-2 concentration than systemic IL-2 application. Consequently a greater beneficial effect could be expected after local IL-2 application (peritumoral = juxtatumoral, intratumoral, intra-arterial, intracavitary, or intratracheal = inhalation). Free IL-2: Many groups have tried to prepare a more effective IL-2 formulation than free IL-2. Examples are slow release systems, insertion of the IL-2 gene into a tumor cell causing prolonged IL-2 release. However, logistically free IL-2 is much easier to apply; hence we concentrated in this review and in most of our experiments on the use of free IL-2. Local therapy with free IL-2 may be effective against transplanted tumors in experimental animals, and against various spontaneous carcinomas, sarcomas, and melanoma in veterinary and human cancer patients. It may induce rejection of very large, metastasized tumor loads, for instance advanced clinical tumors. The effects of even a single IL-2 application may be impressive. Not each tumor or tumor type is sensitive to local IL-2 application. For instance transplanted EL4 lymphoma or TLX9 lymphoma were not sensitive in our hands. Also the extent of sensitivity differs: In Bovine Ocular Squamous Cell Carcinoma (BOSCC) often a complete regression is obtained, whereas with the Bovine Vulval Papilloma and Carcinoma Complex (BVPCC) mainly stable disease is attained. Analysis of the results of local IL-2 therapy in 288 cases of cancer in human patients shows that there were 27% Complete Regressions (CR), 23% Partial Regressions (PR), 18% Stable Disease (SD), and 32% Progressive Disease (PD). In all tumors analyzed, local IL-2 therapy was more effective than systemic IL-2 treatment. Intratumoral IL-2 applications are more effective than peritumoral application or application at a distant site. Tumor regression induced by intratumoral IL-2 application may be a fast process (requiring about a week) in the case of a highly vascular tumor since IL-2 induces vascular leakage/edema and consequently massive tumor necrosis. The latter then stimulates an immune response. In less vascular tumors or less vascular tumor sites, regression may require 9-20 months; this regression is mainly caused by a cytotoxic leukocyte reaction. Hence the disadvantageous vascular leakage syndrome complicating systemic treatment is however advantageous in local treatment, since local edema may initiate tumor necrosis. Thus the therapeutic effect of local IL-2 treatment is not primarily based on tumor immunity, but tumor immunity seems to be useful as a secondary component of the IL-2 induced local processes. If local IL-2 is combined with surgery, radiotherapy or local chemotherapy the therapeutic effect is usually greater than with either therapy alone. Hence local free IL-2 application can be recommended as an addition to standard treatment protocols. Local treatment with free IL-2 is straightforward and can readily be applied even during surgical interventions. Local IL-2 treatment is usually without serious side effects and besides minor complaints it is generally well supported. Only small quantities of IL-2 are required. Hence the therapy is relatively cheap. A single IL-2 application of 4.5 million U IL-2 costs about 70 Euros. Thus combined local treatment may offer an alternative in those circumstances when more expensive forms of treatment are not available, for instance in resource poor countries.

Partial Prostatectomy Using Nd:YAG Laser for Management of Canine Prostate Carcinoma

OBJECTIVE

To report a technique for partial prostatectomy by laser dissection and to evaluate outcome and complications in dogs with prostate carcinoma (PCA).

STUDY DESIGN

Experimental and clinical case series.

ANIMALS

Four normal dogs and 8 dogs with PCA.

METHODS

Subcapsular partial prostatectomy, sparing the urethra and the dorsal aspect of the prostatic capsule, using Nd:YAG laser dissection to remove the prostatic parenchyma and control hemorrhage was performed in 4 normal dogs and subsequently in 8 dogs with histologically confirmed PCA. Additional treatment of PCA dogs included local application of interleukin-2 and systemic administration of meloxicam. Prostate size, complications, and survival time were recorded. Laser-associated thermal damage to surrounding tissue was evaluated by histology.

RESULTS

In normal dogs, no damage to the dorsal prostatic capsule or urethra was detected. In PCA dogs, median survival was 103 days (range, 5-239 days). Three dogs died from complications within 16 days, whereas 5 (median survival, 183 days; range, 91-239 days) had improvement or resolution of clinical signs. Urinary incontinence did not occur.

CONCLUSION

Laser assisted subcapsular partial prostatectomy can be performed in dogs with PCA without development of postoperative incontinence.

CLINICAL RELEVANCE

Subcapsular partial prostatectomy is a potential palliative treatment for PCA in dogs and may lead to the resolution of clinical signs for several months.

Locoregional IL-2 low dose applications for gastrointestinal tumors

AIM: To explore the feasibility of local interleukin 2 (IL-2) in patients with different forms of abdominal cancer. This required experimentation with the time interval between IL-2 applications and the methods of application.

METHODS: Sixteen patients with stages III and IV of gastrointestinal malignancies (primary or metastatic) who were admitted to our Department of Gastroenterology were treated with locoregionally applied IL-2 in low doses.

RESULTS: No major problems applying locoregional IL-2 were encountered. In 6 out of 16 patients, a modest but clinically worthwhile improvement was obtained. Adverse effects were minimal. The therapeutic scheme was well tolerated, even in patients in a poor condition.

CONCLUSION: This study demonstrates the feasibility of low dose locoregional IL-2 application in advanced abdominal cancer. Local IL-2 therapy gives only negligible adverse effects. The results suggest that it is important to apply intratumorally. Local IL-2 may be given adjunct to standard therapeutic regimes and does not imply complex surgical interventions. These initial results are encouraging.

Treatment of stage III-IV nasopharyngeal carcinomas by external beam irradiation and local low doses of IL-2

The therapeutic effect of intratumoural application of Interleukin-2 (IL-2) was studied in patients with stage III-IV nasopharyngeal carcinoma (NPC) that received radiotherapy. Patients with stage III-IV NPC receiving a standard treatment of 7,000 cGy external beam irradiation have a mean disease-free survival of about 1.5 years. In this paper, we describe ten of these patients who were treated with additional peritumoural and intratumoural injections with 3 x 10(4) U IL-2 on 5 days in weeks 2, 4, and 6 of the 7-weeks' irradiation period. This combined treatment group was compared with a historical group of patients treated with standard irradiation alone. Local IL-2 therapy showed a marked clinical and statistical significant improvement of disease-free survival. After 5 years, 63% of the IL-2 treated patients were disease-free versus 8% of the control patients. These results suggest that the therapeutic results of radiotherapy can be significantly improved by combining it with local IL-2 treatment. To our knowledge, this is the first clinical report showing that local IL-2 therapy is effective against an infiltrative and locally metastasizing tumour in human patients.

Local interleukin 2 therapy is most effective against cancer when injected intratumourally

Local interleukin 2 (IL-2) therapy is more effective against systemic tumours than systemic IL-2 therapy, but it remains unclear whether IL-2 should be injected intratumourally or peritumourally. To investigate this question, we treated DBA/2 mice bearing a large subcutaneous syngeneic SL2 lymphoma with either intra or peritumoural IL-2 therapy. Both applications enhanced survival, but intratumourally injected IL-2 was more effective than peritumourally injected IL-2. Tumours started to regress 4 days after IL-2 injection. Tumour cells died at the IL-2 injection site, although IL-2 is not directly cytotoxic for SL2 cells in vitro. Tumour cell death correlated well with oedema and extravascular erythrocytes, but less with leukocyte infiltrates. In mice bearing two s.c. tumours, intratumoural application therapy of IL-2 in one tumour caused decrease in size of both tumours in 4-9 days after therapy. However, the IL-2 treated tumours regressed more strongly than the untreated tumours. We conclude that vascular leakage and/or tissue destruction inside the tumour may contribute to the enhanced effect of intratumoural IL-2 therapy compared to peritumoural IL-2 therapy. Hence, we recommend applying of intratumoural rather than peritumoural IL-2 therapy.

Local interleukin-2 and interleukin-12 therapy of bovine ocular squamous cell carcinomas

Interleukin-2 and interleukin-12 have been used independently to successfully treat the induced and the spontaneous tumours in animals. This trial was done to determine if a combination of IL-2 and IL-12 in the treatment of spontaneous bovine ocular squamous cell carcinomas (BOSCC) would be more successful than IL-2 or IL-12 therapy by themselves. For this trial, we selected 25 BOSCC tumours seen on Holstein Fresian cows in Beatrice, Zimbabwe. The cows were randomly assigned to a treatment group of 5 days of IL-2 (200,000 U/day), 5 days of IL-12 (0.5 microg/day) or 5 days of IL-2 (200,000 U/day) and IL-12 (0.5 microg/day). At 20 months after treatment, the IL-2 therapy group had 63% complete regressions; the combination group had 38% complete regressions, which were significantly higher than the IL-12 group, which had 0% complete regressions at 20 months, despite having 29% complete regressions at 6 months. These results show that IL-2 therapy by itself and in combination with IL-12 is more successful than IL-12 by itself. However, combination therapy does not improve the outcome in comparison to IL-2 as a single therapy. It also proves that IL-2 is consistently successful in the therapy of BOSCC with over 60% complete regression, which corresponds to a number of other studies we have done on IL-2 therapy of BOSCC [Rutten, V.P.M.G., Klein, W.R., De Jong, W.A., Misdorp, W., Den Otter, W., Steerenberg, P.A., De Jong, W.H., Ruitenberg, E.J., 1989. Local interleukin-2 therapy in bovine ocular squamous cell carcinoma. A pilot study. Cancer Immunol. Immunother. 30, 165--169; Stewart, R.J.E., Hill, F.W.G., Masztalerz, A., Jacobs, J.J.L., Koten, J.W., Den Otter, W., 2003. Local low dose interleukin-2 therapy of bovine ocular squamous cell carcinomas in cattle in Zimbabwe, submitted for publication; Den Otter, W., Hill, F.W.G., Klein, W.R., Koten, J.W., Steerenberg, P.A., De Mulder, P.H.M., Rutten, V.P.M.G., Ruitenberg, E.J., 1993. Low doses of interleukin-2 can cure large bovine ocular squamous cell carcinoma. Anticancer Res. 13, 2453-2455; Den Otter, W., Hill, F.W.G., Klein, W.R., Koten, J.W., Steerenberg, P.A., De Mulder, P.H., Rhode, C., Stewart, R., Faber, J.A., Ruitenberg, E.J., 1995. Therapy of bovine ocular squamous cell carcinoma with local doses of interleukin-2: 67% complete regressions after 20 months of follow-up. Cancer Immunol. Immunother. 41, 10-14].

In situ crosslinked biodegradable hydrogels loaded with IL-2 are effective tools for local IL-2 therapy

We investigated the therapeutic efficacy of recombinant human interleukin-2 (rhIL-2)-loaded, in situ gelling, physically crosslinked dextran hydrogels, locally applied to SL2 lymphoma in mice. The physical crosslinking was established by stereocomplex formation between d-lactic acid oligomers and l-lactic acid oligomers grafted separately to dextrans. The stereocomplex hydrogel as described in our manuscript has several favourable characteristics, which enables its use as system for the controlled release of pharmaceutically active proteins. Firstly, the hydrogel system is a physically crosslinked system. In physically crosslinked gels, the use of chemical crosslinking agents is avoided. Such agents can potentially inactivate the protein and can covalently link the protein to the hydrogel network. Secondly, the hydrogel formation takes place at room temperature and physiological pH, and, importantly, in an all-aqueous environment. All factors are important to preserve the three-dimensional structure, and thus the biological activity, of the protein to be entrapped and released from the gels. Thirdly, the gel formation does not occur instantaneously. This means that a liquid formulation can be injected which solidifies after injection (in situ gel formation is possible). Fourthly, no pH drop during degradation is expected during degradation. As a control, free rhIL-2 was administered locally in either a single injection or at five consecutive days. All mice received the same total dose of rhIL-2. The rhIL-2-loaded hydrogels released most IL-2 over a period of about 5 days. The biocompatibility and biodegradability of the gels were excellent, as there were no acute or chronic inflammatory reaction and as the gels were replaced completely by fibroblasts after 15 days. The therapeutic efficacy of rhIL-2-loaded in situ gelled hydrogels is very good, as was demonstrated in DBA/2 mice bearing SL2. The therapeutic effect of a single application of gels loaded with 1 x 10(6) IU rhIL-2 is at least comparable to the therapeutic effect of injection of an equal dose of free rhIL-2. All mice cured with rhIL-2-loaded hydrogels survived a subsequent challenge, rejecting 10(6) intraperitoneal (i.p.) injected SL2 cells. In conclusion, this study demonstrates that in situ gelling, physically crosslinked dextran hydrogels slowly release encapsulated rhIL-2 in such a way that it is intact and biologically and therapeutically active. These hydrogels may greatly enhance the clinical applicability of rhIL-2 immunotherapy as only a single treatment is required and as these hydrogels are completely biodegradable.

Further development of local IL-2 therapy of cancer: multiple versus single IL-2 treatment of transplanted murine colon carcinoma

We have compared the effect of one and up to four local IL-2 treatments of transplanted MC38 colon carcinoma. A single IL-2 treatment prolonged the survival time ( p=0.015), but no cure was obtained. One local IL-2 treatment inhibited tumor growth for about 1 week. After the start of tumor regrowth, a further IL-2 injection was given. After four IL-2 injections 6 out of 13 mice were cured. Histological studies show that IL-2 induced a local vascular leakage syndrome leading to massive peritumoral edema and subsequent necrosis of tumor tissue. IL-2 also attracted infiltrating cells, mainly macrophages. Subsequent IL-2 injections led to complete tumor regression. We believe that the combination of necrotic tumor debris and the IL-2-induced macrophage reaction enhanced a tumor-specific immune response. This local IL-2 application was not toxic.

Presence of Cytotoxic B220+CD3+CD4−CD8− Cells Correlates with the Therapeutic Efficacy of Lymphoma Treatment with IL-2 and/or IL-12

Cancer treatment with IL-2 and IL-12 is thought to work via enhancement of proliferation and activity of T cells and NK cells. Incubation of cytotoxic T lymphocytes (CTLs) and NK cells with IL-2 and/or IL-12 results in propagation of a distinct cell type called lymphokine-activated killers (LAK) characterized by increased lytic activity against many tumor types. Here we address the question whether cytokine therapy may be efficient in treatment of a LAK-insensitive tumor and, if so, which cell type, other than classic LAK cells, is responsible for tumor cell killing. We used DBA/2 mice bearing metastasized SL2 lymphoma and treated them with locally applied IL-2 and /or IL-12 injections. We showed that IL-12 treatment is efficient, though there is a rather narrow range of effective doses because of toxicity. This toxicity may be alleviated by a single injection of IL-12 before treatment. Next, we showed that IL-12 synergistically enhances the efficacy of local IL-2 treatment. Moreover, our results indicate that the IL-2/IL-12-mediated therapeutic effect is greatest when it is given after establishment of an immune response to a tumor. Finally, we showed the existence of a unique population of lymphoid cells, namely B220+CD3+CD4-CD8-, at the site of tumor growth. These cells become highly cytotoxic to SL2 cells in mice treated with cytokines late (day 10-14) in the course of the immune response, but not in mice treated early (day 3-7), and cytotoxicity of this unique cell population correlates with the success of therapy.

IL-2 loaded dextran microspheres with attractive histocompatibility properties for local IL-2 cancer therapy

Biodegradable dextran microspheres (MS) were developed as a slow-release system for interleukin-2 (IL-2) to apply them for local IL-2 therapy of cancer. We describe the tissue reactions induced by these MS without or with IL-2 in rats. Dextran MS stain bright red-purple with the periodic acid Schiff (PAS), visualising the exact spot of IL-2 release and its relation to the histological reaction pattern. Subcutaneously injected MS always form a well-circumscribed deposit. In the first 2 days there is a PMN inflammation within the MS-deposit, but the surroundings show only a scanty inflammatory reaction. The PMN reaction is replaced by an abundant macrophage reaction in particular in the MS-deposit. At day 21 a fibrous capsule of about 50 mum surrounds the deposit. The effect of IL-2 administered in its free form is mainly vascular, with vascular dilatation, vascular leakage and oedema. It is remarkable that lymphocytes are present in the injection area already at day 2. When IL-2 releasing MS were used, the various reactions induced by IL-2 and MS were amplified leading to local necrosis. We conclude that neither placebo MS nor IL-2 leads to necrosis after subcutaneous injection in rats. In contrast, when IL-2 was released from MS, then massive necrosis was induced. This might be due to increased phagocytosis or changes in the micro-niche due to the release of humoral factors by the infiltrating cells. This is probably fortuitous for local IL-2 therapy of cancer, as massive necrosis of tumour cells can be expected to lead to an increased antitumour reaction.

Therapeutic effect of a single peritumoural dose of IL-2 on transplanted murine breast cancer

Interleukin-2 therapy is not clearly effective against breast cancer both in mouse models and in human patients. However, the study of IL-2 therapy of breast cancer remains important, as 3,700 women died from this malignancy in the Netherlands in 2000. Previously we have shown the therapeutical efficacy of a single peritumoural IL-2 application in different experimental models and in veterinary patients. Here we apply this mode of IL-2 therapy to advanced mouse mammary carcinoma models, i.e., severe metastasised tumours in A/Sn mice and non-metastasised carcinomas in BALB/c mice. Mice with advanced transplanted mammary carcinomas were given a single peritumoural treatment with 2.5 x 10(6) IU IL-2 at days 10-14 after i.p. or s.c. inoculation of 10(6) carcinoma cells. Within each experiment it was always possible to distinguish relatively slowly and fast growing tumours which allows the therapeutical effect of IL-2 in tumours with different growth rates to be studied. A new approach to analyse results enabled us to show that survival of mice with transplanted, advanced metastasised breast cancer can be significantly improved after a single local treatment with IL-2. Advanced relatively fast i.p and s.c. growing mammary carcinomas seem to be more sensitive to a single IL-2 treatment than relatively slowly growing tumours. IL-2 was most effective against non-metastasised mouse breast cancer.

Intralesional lipid-complexed cytokine/superantigen immunogene therapy for spontaneous canine tumors

These studies sought to determine the gene expression and short-term effects of intralesional lipid-complexed immunogene therapy with constructs encoding Staphylococcus aureus enterotoxin A and canine interleukin-2 (L-SEA/cIL-2) in dogs with tumors of various histotypes, and then to assess the safety and efficacy of repeated L-SEA/cIL-2 injections in dogs with spontaneous soft tissue sarcomas (STS). In the first study, pet dogs with a variety of tumors received a single intralesional injection of L-SEA/cIL-2, and surgical excision was performed 48 h later. In the second study, dogs with histologically confirmed STS were treated weekly for a maximum of 12 weeks with escalating doses of L-SEA/cIL-2. Tumors were then surgically excised and assessed histologically and immunohistochemically. Overall, treatments were well tolerated, with no dose-limiting toxicities encountered. At 48 h, in the single injection study, plasmid DNA was detected in 14 of 16 tumor samples, and plasmid-specific mRNA was detected in 3 of 14. In the multiple injection study, the overall response rate in dogs with STS was 25%, consisting of 3 complete responses (CR) and 1 partial response (PR). Diffuse lymphoplasmacytic inflammation was observed in all tumors from patients experiencing CR or PR, whereas these changes were not evident in tumors from nonresponders. The infiltrate was composed primarily of CD3(+) cells at 48 h from the single-injection study, and was composed of both CD3(+) and CD79a(+) cells at 12 weeks in responding dogs from the multiple-injection study. In conclusion, these studies suggests that intralesional L-SEA/cIL-2 immunotherapy is well tolerated, results in detectable transgene expression in canine tumors, and has antitumor activity in dogs with spontaneous STS.

Therapeutic efficacy of IL-2-loaded hydrogels in a mouse tumor model

Interleukin-2 (IL-2) is a highly effective anticancer drug if it is applied locally for 5 consecutive days. In most cases this requires 5 invasive treatments, which is not usually acceptable for either the patient or the clinician. For this reason we have developed dextran-based hydrogels from which the required amount of encapsulated IL-2 (1-4 x 10(6) IU of IL-2) is gradually released during 5-10 days. Initially IL-2-containing macroscopic cylinder-shaped gels (implants), and later IL-2-containing injectable microspheres, were developed. These preparations were characterized in vitro, and the therapeutic activity was tested in DBA/2 mice with SL2 lymphosarcoma. The therapy was given to mice with a large and extensively metastasized tumor load (at least 5% of the body weight). If 1-4 x 10(6) IU of IL-2 was slowly released from the hydrogels over a period of 5-10 days, the therapeutic effects were very good and comparable to the effects of free IL-2 injections for 5 consecutive days. In conclusion, dextran-based hydrogels are promising systems for the controlled release of IL-2.

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.

Optimal regimes for local IL-2 tumour therapy

In this report we present studies on optimal regimes for regional IL-2 therapy, focused on dose, schedule and site of injection. Original data obtained in 2 murine tumour models show that all 3 factors are of importance. Anti-tumour responses were most effective when IL-2 was administered regionally 5 to 10 times, at doses ranging from 7,000 to 33,000 IU/day every day or every other day. This resulted in cure rates of more than 40% in mice bearing ascitic tumour that had also disseminated to liver and lungs. The importance of these data is discussed in the light of previous results of our group. These results illustrate that the doses and schedules used in this study are not effective exclusively in these 2 tumour models but may have a more general applicability.