Responsiveness of human prostate carcinoma bone tumors to interleukin-2 therapy in a mouse xenograft tumor model.

We have tested an immunotherapy approach for the treatment of metastatic prostate carcinoma using a bone tumor model. Human PC-3 prostate carcinoma tumor cells were heterotransplanted into the femur cavity of athymic Balb/c nude mice. Tumor cells replaced marrow cells in the bone cavity, invaded adjacent bone and muscle tissues, and formed a palpable tumor at the hip joint. PC-3/IF cell lines, generated from bone tumors by serial in vivo passages, grew with faster kinetics in the femur and metastasized to inguinal lymph nodes. Established tumors were treated with systemic interleukin-2 (IL-2) injections. IL-2 significantly inhibited the formation of palpable tumors and prolonged mouse survival at nontoxic low doses. Histologically IL-2 caused vascular damage and infiltration of polymorphonuclear cells and lymphocytes in the tumor as well as necrotic areas with apoptotic cells. These findings suggest destruction of tumor cells by systemic IL-2 therapy and IL-2 responsiveness of prostate carcinoma bone tumors.

Systemic interleukin 2 therapy for human prostate tumors in a nude mouse model.

Once the regional lymph nodes become involved in prostate carcinoma, 85% of patients develop distant metastases within 5 years, and metastatic disease is difficult to treat. We have investigated the effect of systemic interleukin 2 (IL-2) treatment on metastatic prostate carcinoma using a xenograft tumor model. Cells from a PC-3/IF cell line, produced by intrafemoral injection of human PC-3 prostate carcinoma cells, were injected in the prostate of Balb/c nude mice. Prostate tumors and para-aortic lymph nodes were resected, and tumor cells were recultured and passaged in the prostate in vivo to produce new cell lines. On day 6 following prostatic injection of these cell lines, mice were treated with i.p. injections of IL-2 at 25,000-50,000 units/ day for 5 consecutive days. The effect of IL-2 on tumor progression was assessed, and histological studies were performed on prostate tumor and lymph node sections. The tumor cell lines generated by serial prostate injection were tumorigenic and metastasized to regional para-aortic lymph nodes. Tumors of 0.4 cm were obtained by day 16 and grew to 1-1.5 cm by day 40 with metastasis to para-aortic lymph nodes. Following two to three weekly courses of 5 days of 25,000-40,000 units/day of IL-2, the growth of prostate tumors was inhibited by 94%. Higher doses of 50,000 units/ day were toxic. Histologically, prostate sections showed vascular damage manifested by multifocal hemorrhages and an influx of lymphocytes and polymorphonuclear cells into disintegrating tumors and areas of necrosis containing numerous apoptotic cells. In contrast to control mice, para-aortic lymph nodes were not enlarged in responding mice. These findings suggest that systemic IL-2 therapy can induce an antitumor response in prostate tumors and control their growth and metastasis.

Interleukin-13 receptors on human prostate carcinoma cell lines represent a novel target for a chimeric protein composed of IL-13 and a mutated form of Pseudomonas exotoxin.

We have discovered a new cell surface protein in the form of interleukin-13 receptor on several solid tumor cells, including human renal cell carcinoma cells (Obiri et al., 1995; Debinski et al., 1995). This study reports that human prostate cancer cell lines also express high affinity IL-13 receptors (Kd = 159 pM). These receptors are functional because IL-13 surprisingly increased proliferation of all three prostate cancer cell lines studied as determined by thymidine uptake and clonogenic assays. IL-13 receptors on prostate cancer cell lines were targeted using a chimeric protein composed of IL-13 and a mutated form of Pseudomonas exotoxin (PE38QQR). This molecule, termed IL13-PE38QQR, has been found cytotoxic to all three prostate cancer cell lines as determined by the inhibition of protein synthesis. The IC50 ranged between 1 nmol/l, to 15 nmol/l. These data were confirmed by clonogenic assays in which IL13-PE38QQR almost completely inhibited colony formation at 10 nmol/l. IL13-PE38QQR was not cytotoxic to cells that express little or no IL-13R. Heat inactivated IL13-PE38QQR was not cytotoxic to prostate cancer cells indicating specificity. IL13-PE38QQR was also cytotoxic to colonies when they were allowed to form first for several days before the addition of toxins. Our data suggest that additional studies should be performed to target IL-13 receptor bearing prostate cancer.

Inhibition of murine renal carcinoma pulmonary metastases by systemic administration of interferon gamma: mechanism of action and potential for combination with interleukin 4.

We have previously demonstrated that IFN-gamma causes cell growth inhibition and up-regulation of MHC antigens in human renal cell carcinoma cell lines. In this study, we have investigated the therapeutic potential of IFN-gamma for the treatment of 5-day established pulmonary metastases induced by i.v. injection of Renca cells, a murine renal adenocarcinoma. We found that systemic injections of IFN-gamma significantly reduced the number of lung metastases in a dose-dependent manner and increased mouse survival. Histological evaluation of IFN-gamma-treated lungs showed residual small tumor nodules containing extensive necrosis and mononuclear infiltrates. Immunohistochemistry studies on lung sections showed macrophage infiltration into tumor nodules, and in vivo depletion of macrophages partially inhibited IFN-gamma antitumor effect, suggesting a role for the macrophages in tumor destruction. Lymphocyte depletion of either natural killer (NK) cells or CD4+ or CD8+ T-cell subsets or both T-cell subsets did not affect the IFN-gamma effect, whereas depletion of both NK and T cells decreased the antitumor activity of IFN-gamma. These data indicate that neither T cells nor NK cells are essential for this activity but that either lymphocyte population can contribute to the IFN-gamma effect. An optimal dose of IFN-gamma inhibited by 60% the growth of Renca cells treated for 3 days in vitro, but this effect was transient and less pronounced in a long-term colony assay, suggesting that IFN-gamma direct growth inhibition may play a role but may not be sufficient to mediate its antitumor effect in vivo. In vitro, IFN-gamma caused up-regulation of class I MHC antigens and induction of class II antigen expression in Renca cells, an effect that may enhance Renca immunogenicity but may be relevant only when a T-cell response is elicited. A sequential administration of IFN-gamma followed by interleukin 4 was therapeutically better than IFN-gamma alone for the treatment of advanced pulmonary metastases, probably due to different antitumor mechanisms induced by these two cytokines.

The mechanism of local tumor irradiation combined with interleukin 2 therapy in murine renal carcinoma: histological evaluation of pulmonary metastases.

We have demonstrated that tumor irradiation enhanced the therapeutic effect of interleukin 2 (IL-2) on pulmonary metastases from a murine renal adenocarcinoma, Renca. To investigate the mechanism of interaction between tumor irradiation and IL-2 therapy, we have histologically evaluated the effects of each therapy alone or in combination on Renca pulmonary metastases. Following treatment of established lung metastases with irradiation and IL-2 therapy, lung sections were processed for H&E or immunohistochemical staining. We found that tumor irradiation or IL-2 therapy locally induced vascular damage, resulting in multifocal hemorrhages and mononuclear cell mobilization in the lung tissue. This effect was amplified in lungs treated with the combined therapy. Immunohistochemistry showed that irradiation produced a macrophage influx into irradiated tumor nodules, and systemic IL-2 therapy induced T-cell infiltration in tumor nodules. Lungs treated with the combined therapy exhibited massive macrophage, T-cell, and natural killer cell mobilization in disintegrating tumor nodules and in the lung tissue. This combined therapy caused a decrease in the number of proliferating tumor cells and an increase in the number of apoptotic cells, which were more marked than with either therapy alone. We suggest that the macrophages mobilized by radiation-induced tissue injury could play a role in phagocytosis of apoptotic tumor cells, processing and presenting of tumor antigens for a systemic immune response activated by IL-2. Tumor destruction may result from the concomitant action of activated T cells, natural killer cells, and macrophages infiltrating the tumor nodules.

Local tumor irradiation augments the response to IL-2 therapy in a murine renal adenocarcinoma.

We have previously demonstrated that local tumor irradiation effectively enhanced the therapeutic effect of IL-2 therapy on pulmonary metastases from a murine renal adenocarcinoma, Renca. Irradiation with 300 rad to the left lung only, followed by systemic IL-2 therapy, results in increased tumor reduction in both lungs, suggesting that radiation enhances the systemic effect of immunotherapy. In this study, we show that irradiation of the tumor-bearing organ is essential for the combined effect of both modalities. This effect is radiation dose-dependent as increases in the radiation dosage result in greater tumor reduction in the irradiated field as well as systemically in nonirradiated fields when combined with immunotherapy. We find that irradiation has a direct inhibitory effect on Renca cell growth in vitro. Irradiation of Renca cells also causes an upregulation in H-2Kd class I MHC antigen detectable at 300 rad and more pronounced with 800 rad. By in vivo selective depletion of lymphocyte subsets, we demonstrate the involvement of Lyt-2+ and L3T4+ T cell subsets and AsGM1+ cells, including NK cells, in the antitumor effect mediated by tumor irradiation and IL-2 therapy. Immunohistochemistry studies, performed on lung sections, showed a significant infiltration of CD3+ T cells and macrophages in the tumor nodules following treatment with tumor irradiation and IL-2 therapy. Our studies indicate that the mechanism of interaction between tumor irradiation and immunotherapy may include radiation-induced alterations in the tumor growth and antigenicity which may enhance or trigger an anti-tumor response elicited by IL-2 and mediated by T cells, AsGM1+ cells, and macrophages.

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.

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.

Expansion of activated lymphocytes obtained from renal cell carcinoma in an automated hollow fiber bioreactor.

Immunotherapy using IL-2 alone or combined with activated lymphocytes has been promising for metastatic renal cell carcinoma. Cytotoxic lymphocytes can be isolated from tumors, expanded in vitro with IL-2, and adoptively transferred back into the tumor-bearing host. These cells can also be transduced with the genes coding for cytokines for local delivery to tumor sites. A major drawback in adoptive immunotherapy is the cumbersome and expensive culture technology associated with the growth of large numbers of cells required for their therapeutic effect. To reduce the cost, resources, and manpower, we have developed the methodology for lymphocyte activation and expansion in the automated hollow fiber bioreactor IMMUNO*STAR Cell Expander (ACT BIOMEDICAL, INC). Tumor Infiltrating Lymphocytes (TIL) isolated from human renal cell carcinoma tumor specimens were inoculated at a number of 10(8) cells in a small bioreactor of 30 ml extracapillary space volume. We have determined the medium flow rates and culture conditions to obtain a significant and repeated expansion of TIL at weekly intervals. The lymphocytes cultured in the bioreactor demonstrated the same phenotype and cytotoxic activity as those expanded in parallel in tissue culture plates. Lymphocyte expansion in the hollow fiber bioreactor required lower volumes of medium, human serum, IL-2 and minimal labor. This technology may facilitate the use of adoptive immunotherapy for the treatment of refractory malignancies.