Systemic administration of rIL-12 induces complete tumor regression and protective immunity: response is correlated with a striking reversal of suppressed IFN-gamma production by anti-tumor T cells

B7.2-Ig fusion proteins enhance IL-4-dependent differentiation of tumor-sensitized CD8+ cytotoxic T lymphocyte precursors

The B7/CD28 co-stimulatory pathway plays a critical role in T cell activation and differentiation. Our previous study demonstrated that administration of B7.2-Ig fusion proteins to tumor-bearing mice elicits IL-4-dependent, CD8+ T cell-mediated tumor regression. Here, we investigated whether B7.2-Ig stimulation of tumor-sensitized CD8+ CTL precursors during in vitro antigen re-sensitization actually results in their differentiation into mature CTLs and if so, whether such a process depends on IL-4 signals. Splenocytes from tumor-sensitized (tumor-bearing or tumor-immunized) mice exhibited low levels of anti-tumor CTL responses upon culturing alone, but induced strikingly enhanced CTL responses when stimulated in vitro with B7.2-Ig fusion proteins. Because CTLs were not generated from normal splenocytes even by B7.2-Ig stimulation, the expression of the B7.2-Ig effect required the in vivo tumor sensitization of CD8+ CTL precursors. Administration of anti-CD4 or anti-CD40 ligand (CD40L) to mice before tumor sensitization resulted in almost complete inhibition of CTL responses generated in the subsequent culture containing B7.2-Ig. In contrast, anti-IL-4 did not influence in vivo tumor sensitization required for CTL induction. However, B7.2-Ig stimulation of tumor-sensitized splenocytes enhanced IL-4 production and neutralization of this IL-4 with anti-IL-4 potently down-regulated CTL responses. These results indicate that B7.2-Ig enhances IL-4-dependent differentiation of anti-tumor CD8+ CTL precursors that can be sensitized in vivo depending on collaboration with CD4+ T cells involving CD40L function.

Impaired interferon-gamma production as a consequence of STAT4 deficiency after autologous hematopoietic stem cell transplantation for lymphoma

Production of interferon gamma (IFN-gamma) is critical for optimal antitumor immunotherapy in several preclinical animal models. Interleukin-12 (IL-12)-induced IFN-gamma production is markedly defective after autologous stem cell transplantation. Quantitative deficiency in CD4 T cells, relative increase in CD25+CD4+ T cells, and bias toward T helper 2 (Th2) differentiation are not the primary mechanisms of defective IFN-gamma production. IL-12 receptor beta1 (IL-12Rbeta1) and IL-12Rbeta2 are expressed at equivalent or higher levels on posttransplantation patient peripheral blood mononuclear cells (PBMCs) as compared with control PBMCs. IL-12-induced tyrosine phosphorylation of signal transducer and activator of transcription 4 (STAT4) was undetectable or barely detectable in posttransplantation patient PBMCs, whereas IL-4-induced tyrosine phosphorylation of STAT6 did not differ in posttransplantation patient and control PBMCs. Levels of STAT4 protein were decreased by 97% in posttransplantation patient PBMCs. Levels of STAT4 mRNA were also significantly decreased in posttransplantation patient PBMCs. Incubation with IL-12 and IL-18 in combination partially reversed the defective IFN-gamma production by posttransplantation patient PBMCs. IFN-gamma production in response to IL-12 plus IL-18 did not require increased expression of STAT4 but was dependent on the activity of p38 mitogen-activated protein kinase (MAPK). These results indicate that defective IFN-gamma production is due to an intrinsic deficiency in STAT4 expression by posttransplantation patient lymphocytes and suggest strategies for circumventing this deficiency in cancer immunotherapy.

Antitumor and antiangiogenic effects of interleukin 12 gene therapy in murine head and neck carcinoma model

Interleukin-12 (IL-12) plays a critical role in producing an immune response, as indicated in many ways, e.g., induction of interferon-gamma (IFN-gamma), and augmentation of the cytotoxic activity of resting activated T cells and natural killer (NK) cells. In this study, we examined whether intratumoral injection of a recombinant retrovirus vector expressing IL-12s induce antitumor and antiangiogenic effects in a murine model using a murine head and neck squamous cell carcinoma (NR-S1). In vitro the levels of vascular endothelial growth factor (VEGF) mRNA and protein expression were decreased in IL-12 gene transfected NR-S1 cell. in vivo direct IL-12 gene therapy resulted in significantly remarkable inhibition of tumor growth compared to the control group. The tumor regression by direct IL-12 gene therapy was also associated with decreased vessel density, and apoptosis and increased infiltration of CD8(+) T cells and CD56(+) NK cells in the tumor increased. Also, the number of IFN-gamma expressed cells of spleen cells was increased in the treatment group compared with the control group. These results suggested that direct IL-12 gene therapy appears to be effective in reducing tumor growth by triggering both antiangiogenic effects and an immunological enhancing mechanism through induction of IFN-gamma.

IL-27 Mediates Complete Regression of Orthotopic Primary and Metastatic Murine Neuroblastoma Tumors: Role for CD8+T Cells

We have shown previously that IFN-gamma-inducing cytokines such as IL-12 can mediate potent antitumor effects against murine solid tumors. IL-27 is a newly described IL-12-related cytokine that potentiates various aspects of T and/or NK cell function. We hypothesized that IL-27 might also mediate potent antitumor activity in vivo. TBJ neuroblastoma cells engineered to overexpress IL-27 demonstrated markedly delayed growth compared with control mice, and complete durable tumor regression was observed in >90% of mice bearing either s.c. or orthotopic intra-adrenal tumors, and 40% of mice bearing induced metastatic disease. The majority of mice cured of their original TBJ-IL-27 tumors were resistant to tumor rechallenge. Furthermore, TBJ-IL-27 tumors were heavily infiltrated by CD8(+) T cells, and draining lymph node-derived lymphocytes from mice bearing s.c. TBJ-IL-27 tumors are primed to proliferate more readily when cultured ex vivo with anti-CD3/anti-CD28 compared with lymphocytes from mice bearing control tumors, and to secrete higher levels of IFN-gamma. In addition, marked enhancement of local IFN-gamma gene expression and potent up-regulation of cell surface MHC class I expression are noted within TBJ-IL-27 tumors compared with control tumors. Functionally, these alterations occur in conjunction with the generation of tumor-specific CTL reactivity in mice bearing TBJ-IL-27 tumors, and the induction of tumor regression via mechanisms that are critically dependent on CD8(+), but not CD4(+) T cells or NK cells. Collectively, these studies suggest that IL-27 could be used therapeutically to potentiate the host antitumor immune response in patients with malignancy.

Treatment of experimental breast cancer using interleukin-12 gene therapy combined with anti–vascular endothelial growth factor receptor-2 antibody

We have shown previously that interleukin-12 (IL-12) gene therapy induced strong antitumor effects in several syngeneic murine tumor models including 4T1 mammary adenocarcinoma. Antiangiogenic treatment with a monoclonal antibody (mAb) directed against the vascular endothelial growth factor receptor-2 (VEGFR-2) is another promising treatment approach that can cause transient suppression of tumor growth. We hypothesized that the combination of IL-12 gene therapy and anti-VEGFR-2 mAb will achieve better antitumor and antimetastatic effects against 4T1 adenocarcinoma than each treatment alone via implementation of different mechanisms. Administration of anti-VEGFR-2 mAb into BALB/c mice bearing s.c. 4T1 tumors induced significant suppression of tumor growth, as did intratumoral administration of naked IL-12 DNA. The combined treatment with anti-VEGFR-2 mAb and IL-12 DNA resulted in significantly enhanced inhibition of tumor growth as compared with each treatment alone. This combination was also effective against spontaneous lung metastases. In T-cell–deficient nude mice, both IL-12 DNA and anti-VEGFR-2 mAb were effective in suppressing tumor growth. In T-cell- and natural killer cell–deficient scid/beige mice, only anti-VEGFR-2 mAb was effective, suggesting that natural killer cells are involved in the antitumor effects induced by IL-12 DNA. In both types of immunodeficient mice, the combination of anti-VEGFR-2 mAb and IL-12 DNA was as effective in suppressing 4T1 tumor growth as anti-VEGFR-2 mAb alone. Antitumor effects of anti-VEGFR-2 mAb were associated with the inhibition of angiogenesis within the tumors, whereas the antiangiogenic effect of IL-12 gene therapy was not detected. Our results show a therapeutic benefit of combining IL-12 gene therapy and anti-VEGFR-2 mAb for cancer treatment.

Gene therapy of anaplastic thyroid carcinoma with a single-chain interleukin-12 fusion protein

Anaplastic thyroid carcinoma is the most aggressive type of thyroid malignancy with a mean survival time of less than 8 months. No effective therapeutic approach is currently available, making the development of novel treatments necessary. Interleukin (IL)-12 is a proinflammatory heterodimeric cytokine with strong antitumor activity. In the present study, we investigated the potential of IL-12 gene therapy for anaplastic thyroid carcinoma in BALB/c (nu/nu) nude mice. A single-chain IL-12 fusion protein construct was created to assure equal expression of its p35 and p40 subunits. Human anaplastic thyroid carcinoma cell line ARO was stably transfected with an IL-12 expression plasmid under the control of cytomegalovirus (CMV) promoter (scIL-12/CMVpDNA). High levels of functional IL-12 (26.78 +/- 4.11 ng/ml per 10(6) cells per 48 hr) were produced by scIL-12-transfected ARO cells (ARO/IL-12). Tumorigenicity in nude mice was completely lost in scIL-12-transfected ARO cells, as demonstrated by the lack of tumor formation after subcutaneous injection of 2 x 10(6) ARO/IL-12 cells, even though there was no difference in cell proliferation between ARO and ARO/IL-12 cells. Tumor growth was observed after challenge with ARO tumor cells, indicating that protective immunity had not developed against the parental cells. Furthermore, the growth rate of established subcutaneous ARO tumors was significantly reduced by either subcutaneous injection of 2 x 10(6) ARO/IL-12 cells weekly or intramuscular injection of 50 microg scIL-12/CMVpDNA twice weekly. The antineoplastic activity of ARO/IL-12 cells was, however, abrogated by intraperitoneal injection of anti-natural killer (NK) cell antibody. Moreover, significantly higher number of ARO/IL-12 cells and ARO cells were killed by splenocytes from nude mice previously treated with ARO/IL-12 compared to those treated with ARO cells (32% vs. 9% when ARO were used as target cells, 43% vs. 17% when ARO/IL12 were used as target cells; p < 0.01) in an in vitro cytotoxicity assay. Again, tumor cell killing was neutralized by the addition of anti-NK cell antibody in the assay. In conclusion, we have demonstrated successful gene therapy with a scIL-12 fusion protein against anaplastic thyroid carcinoma in an in vivo model. The immune response against ARO/IL-12 cells is mediated by NK cells. These results may set the stage for clinical application of IL-12 gene therapy for poorly differentiated thyroid carcinoma.

Mouse Complement Receptor-Related Gene y/p65-Neutralized Tumor Vaccine Induces Antitumor Activity In Vivo

Two mouse tumor cell lines, Meth A (BALB/c mouse-derived fibrosarcoma) and MM46 (C3H/He mouse-derived mammary tumor), were shown to express high levels of complement receptor-related gene y/p65 (Crry/p65), a membrane-bound complement-regulatory protein. Inhibiting the complement-regulatory activity of Crry/p65 with mAb 5D5 induced high levels of C3 deposition on in vivo tumor-derived Meth A and MM46 cells. To determine the effect of Crry/p65 blockade and increased C3 deposition on in vivo tumor growth, Meth A and MM46 cells were treated with 5D5 mAb and injected into BALB/c and C3H/He mice, respectively. Pretreating MM46 cells with 5D5 mAb significantly suppressed their tumorigenicity when injected s.c. Pretreatment with 5D5 mAb had a modest effect on Meth A s.c. tumor growth. Because complement is involved in the induction of an immune response, we investigated the effect of Crry/p65 blockade and increased C3 deposition on the immunogenicity of the tumor cells in a vaccination protocol. Vaccination of mice with irradiated Meth A cells pretreated with 5D5 mAb protected mice from subsequent challenge. In contrast, vaccination with irradiated Meth A cells without pretreatment was not protective. Survival was correlated with a high titer IgM response and specific CTL activity. These data demonstrate that the functional inhibition of Crry/p65 on tumor cells affects tumor growth and immunogenicity, and that the complement deposition resulting from this inhibition can act in concert with antitumor effector mechanisms to elicit potent antitumor immunity in vivo.

Paracrine release of IL-12 stimulates IFN-gamma production and dramatically enhances the antigen-specific T cell response after vaccination with a novel peptide-based cancer vaccine

Interleukin-12 can act as a potent adjuvant for T cell vaccines, but its clinical use is limited by toxicity. Paracrine administration of IL-12 could significantly enhance the response to such vaccines without the toxicity associated with systemic administration. We have developed a novel vaccine delivery system (designated F2 gel matrix) composed of poly-N-acetyl glucosamine that has the dual properties of a sustained-release delivery system and a potent adjuvant. To test the efficacy of paracrine IL-12, we incorporated this cytokine into F2 gel matrix and monitored the response of OT-1 T cells in an adoptive transfer model. Recipient mice were vaccinated with F2 gel/SIINFEKL, F2 gel/SIINFEKL/IL-12 (paracrine IL-12), or F2 gel/SIINFEKL plus systemic IL-12 (systemic IL-12). Systemic levels of IL-12 were lower in paracrine IL-12-treated mice, suggesting that paracrine administration of IL-12 may be associated with less toxicity. However, paracrine administration of IL-12 was associated with an enhanced Ag-specific T cell proliferative and functional response. Furthermore, paracrine IL-12 promoted the generation of a stable, functional memory T cell population and was associated with protection from tumor challenge. To study the mechanisms underlying this enhanced response, wild-type and gene-deficient mice were used. The enhanced immune response was significantly reduced in IFN-gamma(-/-) and IL-12R beta 2(-/-) recipient mice suggesting that the role of IL-12 is mediated, at least in part, by host cells. Collectively, the results support the potential of F2 gel matrix as a vaccine delivery system and suggest that sustained paracrine release of IL-12 has potential clinical application.

Interleukin-12 immunotherapy of murine transitional cell carcinoma of the bladder: dose dependent tumor eradication and generation of protective immunity

PURPOSE

The antitumor activity of interleukin (IL)-12 has been demonstrated in a number of tumor models but barely tested in bladder cancer models. We evaluated the antibladder cancer activity of this cytokine in syngeneic mice bearing subcutaneous, metastatic and orthotopic tumors.

MATERIALS AND METHODS

Mice were implanted subcutaneously, intravenously or orthotopically with syngeneic transitional cell carcinoma (TCC) of the bladder. The tumor bearing mice were then treated with IL-12 locally or systemically and monitored for tumor regression and survival.

RESULTS

In the subcutaneous model dose dependent suppression of tumorigenesis was observed when IL-12 was administered subcutaneously at a distal site with the MB49 line being more sensitive than MBT-2. IL-12 (10 days) above 50 ng daily was tumor inhibitory, while doses of 500 or 1000 ng daily prolonged survival and cured 70% and 75% of subjects, respectively. Upon re-challenge with parental tumor cells mice previously cured with IL-12 (1000 vs 500 ng daily) exhibited specific protection (70% vs 35% rejection) that was dependent on the earlier dose of cytokine. IL-12 administered intraperitoneally at a dose of 250 ng daily was more potent than subcutaneous administration and complete regression was observed. Metastatic TCC in the lungs and orthotopic tumors in the bladder also favorably responded to systemic or intravesical IL-12 therapy, respectively. Addition of IL-2 to IL-12 therapy increased tumor regression, long-term survival and rejection of re-challenged parental tumor.

CONCLUSIONS

IL-12 is exceptionally effective for treating murine bladder TCC in subcutaneous, metastatic and orthotopic models. The antibladder cancer activity of this cytokine should be tested in human bladder cancer therapy.

Immunological Consequences of Interleukin 12 Administration after Autologous Stem Cell Transplantation

PURPOSE

The purpose is to determine the immunological effects of recombinant human interleukin (rhIL)-12 therapy after autologous stem cell transplantation.

EXPERIMENTAL DESIGN

Twelve patients (8 non-Hodgkin's lymphoma, 2 Hodgkin's disease, and 2 plasma cell myeloma) were treated with rhIL-12 by bolus i.v. injection in doses of 30, 100, or 250 ng/kg starting at a median of 66 days posttransplant. Immunological assays were performed using serum and peripheral blood mononuclear cell (PBMC) samples obtained on study.

RESULTS

Dose-dependent increases in the total lymphocyte count occurred during rhIL-12 therapy. The absolute number of peripheral blood CD4 T cells increased up to 16.3-fold, CD8 T cells up to 20.5-fold, B cells up to 11-fold, and natural killer (NK) cells up to 12.3-fold during rhIL-12 administration and returned to pretreatment baseline levels after discontinuation of rhIL-12. CD56(bright) NK cells expanded dramatically in the blood of a patient with baseline lymphopenia before rhIL-12 therapy. In vitro proliferation of patient PBMCs in response to IL-12 was indistinguishable from that of PBMCs obtained from healthy control sub-jects. Moreover, spontaneous in vitro proliferation of patient PBMCs increased significantly during rhIL-12 therapy. Increased levels of IFN-gamma and IL-18 were detected in the serum of patients treated in the 100 and 250 ng/kg dose cohorts during the first multiple dose cycle.

CONCLUSIONS

Expansion of T, B, and NK cells occurs in vivo during rhIL-12 therapy after autologous stem cell transplantation for hematological malignancies. In contrast to their striking defect in IL-12-induced IFN-gamma production, posttransplant patient PBMCs exhibit normal proliferative responses to IL-12 in vitro. Additional investigation of rhIL-12 for posttransplantation immunotherapy is warranted.

Reduced L-selectin (CD62LLow) expression identifies tumor-specific type 1 T cells from lymph nodes draining an autologous tumor cell vaccine

Reduced expression of CD62L can identify tumor-specific T cells in lymph nodes draining murine tumors. Here, we examined whether this strategy could isolate tumor-specific T cells from vaccinated patients. Tumor vaccine-draining lymph node (TVDLN) T cells of seven patients were separated into populations with reduced (CD62LLow) or high levels of CD62L (CD62LHigh). Effector T cells generated from CD62LLow cells maintained or enriched the autologous tumor-specific type 1 cytokine response compared to unseparated TVDLN T cells in four of four patients showing tumor-specific cytokine secretion. Interestingly, effector T cells generated from CD62LLow or CD62LHigh TVDLN were polarized towards a dominant type 1 or type 2 cytokine profile, respectively. For CD62LLow T cells the type 1 cytokine profile appeared determined prior to culture. Since a tumor-specific type 1 cytokine profile appears critical for mediating anti-tumor activity in vivo, this approach might be used to isolate T cells for adoptive immunotherapy.

The power of combinatorial immunology: IL-12 and IL-12-related dimeric cytokines in infectious diseases

Appropriate induction of a Th1 immune response is required for effective antimicrobial immunity. However, dysregulated Th1 immune responses after infection may also lead to immunopathology. Thus, cell-mediated immune responses have to be tightly regulated. Upon infection, the production of interleukin (IL)-12, a heterodimeric cytokine composed of a p35 and a p40 subunit, is the dominant factor in Th1 cell development. The recent discovery of novel dimeric cytokines closely related to IL-12 add now to our understanding of cellular immunity and the fine tuning of T cell responses. At the onset of infection, IL-27, a heterodimer composed of the IL-12p40-related protein EBI-3 (Epstein-Barr virus-induced gene 3) and the IL-12p35-related protein p28 induces the expression of a functional IL-12 receptor in naive CD4+ T cells, making these cells sensitive to IL-12-mediated Th cell development. Later during infection, IL-23, a heterodimer composed of the IL-12p40 subunit and the IL-12p35-related molecule p19, preferentially acts on Th1 effector/memory CD4+ T cells. The IL-12p40 subunit can also form a homodimer, IL-12p80, which act as an IL-12 and IL-23 antagonist by competing at their receptors. This review focuses on these IL-12-related cytokines contributing to fine tuning of T cell responses after infection with intracellular pathogens.

Induction of Tumor Regression by Administration of B7-Ig Fusion Proteins: Mediation by Type 2 CD8+T Cells and Dependence on IL-4 Production

CD28 signals contribute to either type 1 or type 2 T cell differentiation. Here, we show that administration of B7.2-Ig fusion proteins to tumor-bearing mice induces tumor regression by promoting the differentiation of antitumor type 2 CD8(+) effector T cells along with IL-4 production. B7.2-Ig-mediated regression was not induced in IL-4(-/-) and STAT6(-/-) mice. However, it was elicited in IFN-gamma(-/-) and STAT4(-/-) mice. By contrast, IL-12-induced tumor regression occurred in IL-4(-/-) and STAT6(-/-) mice, but not in IFN-gamma(-/-) and STAT4(-/-) mice. Moreover, B7.2-Ig treatment was effective in a tumor model not responsive to IL-12. B7.2-Ig administration elicited elevated levels of IL-4 production. Tumor regression was predominantly mediated by CD8(+) T cells, although the induction of these effector cells required CD4(+) T cells. Tumor regression induced by CD8(+) T cells alone was inhibited by neutralizing the IL-4 produced during B7.2-Ig treatment. Thus, these results indicate that stimulation in vivo of CD28 with B7.2-Ig in tumor-bearing mice results in enhanced induction of antitumor type 2 CD8(+) T cells (Tc2) leading to Tc2-mediated tumor regression.

IL-12 Production Induced by Agaricus blazei Fraction H (ABH) Involves Toll-like Receptor (TLR)

Agaricus blazei Murill is an edible fungus used in traditional medicine, which has various well-documented medicinal properties. In the present study, we investigated the effects of hemicellulase-derived mycelia extract (Agaricus blazei fraction H: ABH) on the immune system. First, we examined the cytokine-inducing activity of ABH on human peripheral mononuclear cells (PBMC). The results indicated that ABH induced expression of IL-12, a cytokine known to be a critical regulator of cellular immune responses. Flow cytometric analysis demonstrated the induction of IL-12 production by the CD14-positive cell population, consisting of monocytes/macrophages (Mo/Mphi). Furthermore, the elimination of Mo/Mphi attenuated IL-12 production in PBMC. ABH-induced IL-12 production was inhibited by anti-CD14 and anti-TLR4 antibodies but not by anti-TLR2 antibody. The activity of ABH was not inhibited by polymyxin B, while the activity of lipopolysaccharide used as a reference was inhibited. Oral administration of ABH enhanced natural killer (NK) activity in the spleen. These findings suggest that ABH activated Mo/Mphi in a manner dependent on CD14/TLR4 and NK activity.

Natural killer cell depletion confounds the antitumor mechanism of endogenous IL-12 overexpression

IL-12 gene transfer to hepatocytes using a recombinant adenovirus vector (AdIL-12) has been shown to protect against primary and metastatic liver tumors in mice. However, the mechanism of protection has been elusive and studies using depleting monoclonal antibodies or transgenic mice have purported it to be independent of T and NK cells. We postulated that depletion of NK cells may distort the experimental model and misrepresent the antitumor mechanism by altering the magnitude and duration of transgene expression. We show in mice treated with AdIL-12 that NK depletion increased serum IL-12 levels by more than 250-fold and prolonged transgene expression by nearly 2 weeks compared to nondepleted mice. To determine the contribution of NK cells to tumor protection after AdIL-12 treatment, we analyzed NK cells from treated animals. Isolated NK cells were markedly activated in terms of their lytic activity and IFN-gamma secretion. Adoptive transfer of NK cells from mice that had been treated with AdIL-12 to naive mice was sufficient to confer protection against colorectal hepatic metastases. This protection was mediated in part by NK-cell production of IFN-gamma. Our findings indicate that NK-cell depletion distorts the model of systemic AdIL-12 administration by markedly altering transgene expression, which then may potentiate other antitumor mechanisms, and that endogenous IL-12 overexpression activates NK cells, rendering them sufficient to protect against liver metastases. These data have critical implications for investigating the immunologic mechanisms of experimental models that utilize gene transfer.

Antitumor effect of a splenic injection of 5-fluorouracil on metastatic liver cancer in mice

The regional administration of 5-fluorouracil (5-FU) has been the fundamental therapy against liver metastases for the improvement of patient prognosis; however, there have been few reports about the immunological effects of this agent. It is also unknown whether it affects the spleen, one of the major lymphoid organs. The objective of the present study was to determine the immunological effect of an intrasplenic injection of 5-FU against liver metastases. We investigated the effect of an intrasplenic injection of 5-FU on the formation of experimental liver metastasis resulting from an intraportal vein injection of colon 26 carcinoma cells in BALB/c mice and elucidated some of the underlying mechanisms involving the effects of this on cellular immunity. Liver metastases were significantly diminished by the splenic injection of 5-FU, particularly in comparison with the portal injection or systemic administration. This was followed by augmentation of the interleukin-12 (IL-12) level in the spleen and activation of hepatic mononuclear cells. In those cells, NK1.1+ (NKT) cells played a central role against metastases. A splenic injection of 5-FU is more effective on the involution of liver metastases than portal or systemic injection. This effect may be attributed to the augmentation of the IL-12 level in the spleen and of NKT cells in the liver rather than to the original effect of 5-FU, which is the so-called inhibition of DNA synthesis.

In vivo antitumor activity of NKT cells activated by the combination of IL-12 and IL-18

Interleukin-12 and IL-18 have been demonstrated to potentiate innate immunity in a variety of experimental tumor models, but the functional roles of NK and/or NKT cells and their mechanism of action in these models have not been fully addressed. Through adoptive transfer of NKT cells activated in vitro with a combination of IL-12 plus IL-18 (IL-12/IL-18 NKT) into syngeneic animals, we demonstrate in this study that IL-12/IL-18 NKT cells are essential and collaborate with the host's own NK cells in natural host immunity against the growth of ALC and MC57X syngeneic tumors. The relative roles of the adoptively transferred IL-12/IL-18 NKT cells and endogenous NK cells in host protection were first shown in normal C57BL/6 (B6) mice treated with anti-asialo GM1 Ab that selectively depletes NK cells; second, in B6.TCRJalpha281(-/-) mice specifically deficient for NKT cells; and third, in B6.scid mice that also lack NKT cells. Furthermore, by injecting normal B6 mice with anti-IL-2 and/or anti-IFN-gamma mAb, we could demonstrate that effective innate immunity against both types of syngeneic tumors was dependent on the production of IL-2 and IFN-gamma by the adoptively transferred NKT cells. In vitro studies confirmed both the secretion of IL-2 and IFN-gamma by the IL-12/IL-18-activated NKT cells and their collaborative role with NK cells for lysis of ALC and MC57X syngeneic tumor targets. This is the first description of an antitumor function of IL-12/IL-18 NKT cells adoptively transferred into syngeneic hosts that provides the basis for a new modality in the cellular immunotherapy of cancer.

Antitumor and antimetastatic activity of IL-23

The structure and T cell stimulatory effects of the recently discovered cytokine IL-23 are similar to, but distinct from, those of IL-12. Although the antitumor activities of IL-12 are well characterized, the effect of IL-23 on tumor growth is not known. In this study, murine CT26 colon adenocarcinoma and B16F1 melanoma cells were engineered using retroviral vectors to release single-chain IL-23 (scIL-23) to evaluate its antitumor activity. In BALB/c mice, scIL-23-transduced CT26 cells grew progressively until day 26 to an average size of 521 +/- 333 mm(3), then the tumors started to regress in most animals, resulting in a final 70% rate of complete tumor rejection. scIL-23 transduction also significantly suppressed lung metastases of CT26 and B16F1 tumor cells. In addition, mice that rejected scIL-23-transduced tumors developed a memory response against subsequent wild-type tumor challenge. Compared with scIL-12-expressing CT26 cells, scIL-23-transduced tumors lacked the early response, but achieved comparable antitumor and antimetastatic activity. These results demonstrated that IL-23, like IL-12, provided effective protection against malignant diseases, but it probably acted by different antitumor mechanisms. As a first step in identifying these antitumor mechanisms, tumor challenge studies were performed in immunocompromised hosts and in animals selectively depleted of various lymphocyte populations. The results showed that CD8(+) T cells, but not CD4(+) T cells or NK cells, were crucial for the antitumor activity of IL-23.

Potential involvement of monocyte chemoattractant protein (MCP)-1/CCL2 in IL-4-mediated tumor immunity through inducing dendritic cell migration into the draining lymph nodes

We previously observed that IL-4 gene transduction into a mouse colon 26 adenocarcinoma cell line abrogated its tumorigenicity due to the generation of anti-tumor CTL. DEC-205- and CD11c-double positive cells were increased in the lymph nodes of mice injected with IL-4-transfected cells between 2 and 3 days after the tumor injection, compared with those injected with parental cells. Most of these double positive cells expressed CD86 antigen. Among the chemokines with chemotactic activities against dendritic cells, monocyte chemoattractant protein (MCP)-1/CCL2, ABCD-1/CCL22, and liver and activation-regulated chemokine (LARC)/CCL20 gene expression was enhanced no later than 3 days after the tumor injection, in the draining lymph nodes of IL-4-transfected cell bearing mice. Moreover, gene expression of the receptor for MCP-1/CCL2, CCR2, was enhanced in the draining lymph nodes of the mice injected with IL-4-transfected cells, and most DEC-205-positive cells in the lymph nodes expressed CCR2. Finally, the administration of anti-MCP-1/CCL2 antibodies retarded the rate of tumor regression in mice injected with IL-4-tranfected cells, concomitantly with a decrease in DEC-205- and CD11c-double positive cell number in the draining lymph nodes. Thus, locally produced MCP-1/CCL2 may be responsible for IL-4-mediated tumor rejection presumably based on the induction of dendritic cell migration into the draining lymph nodes.

Phenotypic and immunologic characteristics of docetaxel-mobilized peripheral blood stem cells in mice

Effective mobilization of peripheral blood stem cells is vital for transplantation of patients after high-dose chemotherapy and provides a convenient source of stem cells for genetic engineering and other studies, but optimal mobilization strategies have not been defined. Recent studies show that in the presence of recombinant human granulocyte colony-stimulating factor (rhG-CSF), docetaxel (DXT) is an effective mobilization agent. This study was performed to evaluate the phenotype and immunologic properties of DXT-mobilized stem cells. Administration of DXT + rhG-CSF to normal C57Bl/6 mice induced a 75-fold increase in blood hematopoietic progenitors and a significant increase in both CD3(+) (T cell) and DX5(+) [natural killer (NK)] cells when compared to untreated mice. The cytotoxicity of DXT + rhG-CSF-mobilized cell populations against YAC-1 and B16F10 cell lines was not significantly different from that of untreated mice. When compared to cyclophosphamide + rhG-CSF, DXT + rhG-CSF-mobilized cell populations yielded a greater number of T and NK cells, with significantly higher cytotoxic effector function. These results suggest that DXT + rhG-CSF-mobilized PBSCs retain potent immunologic capacity with a high number of the functional cellular subsets than those normally present in peripheral blood, which may be important in maintaining the antitumor immunity after transplantation.

Inhibition of established subcutaneous and metastatic murine tumors by intramuscular electroporation of the interleukin-12 gene

In vivo electroporation (EP) of the murine interleukin-12 (IL-12) gene in an expression plasmid (pIL-12) was evaluated for antitumor activity. EP transfer of pIL-12 into mouse quadriceps muscles elicited significant levels of serum IL-12 and interferon-gamma. Intramuscular EP of pIL-12 resulted in complete regression or substantial inhibition of 38C13 B-cell lymphoma, whereas pIL-12 delivered by gene gun or intramuscular injection without EP showed little therapeutic effect. Impressive antitumor activity by intramuscular EP was also demonstrated in animals with advanced malignant disease. At day 14 after 38C13 tumor inoculation, all animals were found to carry large tumors and to have metastases; without treatment, most died within a week. A single intramuscular EP of pIL-12 resulted in regression of 50% of large subcutaneous tumors and significantly prolonged the lifespan of these animals. Moreover, animals that were previously cured of 38C13 tumors by in vivo EP treatment significantly suppressed tumor growth when challenged 60 days later. In vivo EP of the IL-12 gene was also effective in suppressing subcutaneous and lung metastatic tumors of CT-26 colon adenocarcinoma and B16F1 melanoma cells. Together, these results show that intramuscular electrotransfer of the IL-12 gene may represent a simple and effective strategy for cancer treatment.

Treatment of intracranial glioma with in situ interferon-gamma and tumor necrosis factor-alpha gene transfer

Interferon-gamma (IFNgamma) and tumor necrosis factor-alpha (TNFalpha) are potent immunostimulatory cytokines with demonstrated tumoricidal effects in a variety of cancers. With the aim of investigating their ability to generate antitumor immune responses in malignant brain tumors, we describe the use of in situ adenoviral-mediated IFNgamma and TNFalpha gene transfer in glioma-bearing rodents. Survival was prolonged in mice treated with AdmIFNgamma or AdTNFalpha compared to AdLacZ- and saline-inoculated controls, and AdmIFNgamma- or AdTNFalpha-treated animals revealed significantly smaller tumors. These effects were accompanied by significant up-regulation of tumor MHC-I expression in AdmIFNgamma-inoculated animals, and of MHC-II in AdTNFalpha-treated tumors. Significantly enhanced intratumoral infiltration with CD4(+) and CD8(+) T cells was visible in animals treated with AdmIFNgamma, AdTNFalpha, or a combination of AdmIFNgamma and AdTNFalpha. In addition, AdTNFalpha therapy down-regulated the expression of endothelial Fas ligand, a cell membrane protein implicated as a contributor to immune privilege in cancer. These findings demonstrate the effectiveness of local IFNgamma and TNFalpha gene transfer as a treatment strategy for glioma and illustrate possible physiological pathways responsible for the therapeutic benefit observed.

Fas-Fas ligand signaling pathway mediates an interleukin-12-induced rejection of a murine prostate tumor system

BACKGROUND

Recent data suggest that anti-tumor activities of interleukin-12 (IL-12) involve the induction of apoptosis. Fas (APO-1/CD95) is a type I membrane protein that is capable of initiating an apoptosis signaling pathway when bound to its ligand (FasL). We undertook this study to test the hypothesis that Fas-FasL-mediated apoptosis plays a role in IL-12-induced tumor regression.

METHODS

An mIL-12 expression vector driven by cytomegalovirus promoter was used to express murine IL-12 cDNA in the RM-9 murine prostate carcinoma cell line. Control RM-9 cells and RM-9 cells stably transfected with IL-12 gene (RM-9-IL12) were inoculated subcutaneously in 4- to 6-week-old male C57BL/J6 mice. Tumor size was measured every 3 days. Western blot and immunohistochemical assays were used to evaluate Fas and FasL protein expression. In situ fluorescent end labeling was used to label apoptotic cells.

RESULTS

IL-12-expressing RM-9 prostate carcinoma cells transplanted into C57BL/J6 mice grew more slowly than control RM-9 cells and vector control RM-9-Luc cells. The average survival time of the RM-9-IL12 mice was longer than 53 days, whereas the mean survival for mice transplanted with control RM-9 cells was only 16 days. Apoptotic cells were more numerous in RM-9-IL12 tumors: 10.3% vs. 1.5% in control (P = 0.001). Fas and FasL proteins were increased approximately twofold in the RM-9-IL12 tumors compared with the RM-9 control tumors as determined by Western blot and immunohistochemical analyses (P < 0.05).

CONCLUSION

The Fas-FasL-mediated apoptosis pathway may contribute to the IL-12-induced rejection of prostate carcinoma.

Gene transfer of secreted-type modified interleukin-18 gene to B16F10 melanoma cells suppresses in vivo tumor growth through inhibition of tumor vessel formation

Interleukin-18 is a novel cytokine identified as a strong inducer of interferon-gamma. Interleukin-18 has been shown to have similar bioactivities to interleukin-12 and to have antitumor efficacy in experimental models. In this study, we investigated whether the introduction of the interleukin-18 gene to B16F10 melanoma cells can induce antitumor response or not. Before the transfection, we modified the interleukin-18 gene to enable transfected tumor cells to secrete bioactive interleukin-18, because interleukin-18 does not have a signal sequence and requires processing by the interleukin-1 converting enzyme to attain the mature form. We found that B16 melanoma cells transduced with hybrid cDNA consisting of the interferon-beta signal sequence and mature interleukin-18 sequence, but not native interleukin-18, secreted a large amount of interleukin-18 and exhibited retarded tumor growth when injected in syngeneic mice. The antitumor effect was mostly abrogated by administration of anti-interferon-gamma antibody, but was not affected by in vivo depletion of CD8+ T cells or natural killer cells. Histologic analysis revealed that vascularization was markedly reduced and that necrosis was extensively induced in interleukin-18-secreting B16F10 melanoma (B16/IL18) tissues, whereas abundant tumor vessel formation was observed in B16/IL18 tissues of interferon-gamma-neutralized mice. We also found that chemokines, interferon-inducible protein-10 and monokine induced by interferon-gamma, were produced in B16/IL18 tissues and that the expression of both chemokines was dependent on that of interferon-gamma in the tumor tissues. Further, we showed that B16 melanoma cells secreted both chemokines in response to interferon-gamma. In addition, the expression of angiogenin, an angiogenic factor of melanoma, in B16 melanoma cells was reduced by interferon-gamma treatment. These results indicate that gene transfer of secreted-type interleukin-18 to B16F10 melanoma cells is a useful method of triggering an antitumor response without any systemic adverse effects and that the antitumor efficacy is mainly mediated by antiangiogenic activity, which is possibly involved in at least two dynamic changes induced by interferon-gamma inside B16 melanoma cells: the upregulation of antiangiogenic chemokines, interferon-inducible protein-10 and monokine induced by interferon-gamma, and the downregulation of angiogenic factor, angiogenin.

Adoptive cellular therapy with tumor vaccine draining lymph node lymphocytes after vaccination with HLA-B7/beta2-microglobulin gene-modified autologous tumor cells

Adoptive immunotherapy with anti-CD3-expanded lymphocytes from lymph nodes draining alloantigen gene-modified autologous tumor vaccines is an effective treatment of poorly immunogenic murine tumors. This phase I/II study was performed to determine the feasibility and toxicity of combining ex vivo gene transfer of autologous tumor cells and adoptive immunotherapy with anti-CD3-expanded tumor vaccine draining lymph node lymphocytes (TVDLN) in patients with metastatic melanoma and renal cell cancer (RCC). To facilitate the generation of tumor-specific lymphocytes in the TVDLN, autologous tumor cells were modified by gene transfer ex vivo to express the alloantigen HLA-B7, a modification that has the potential to enhance the immunogenicity of the tumor cells. After vaccination with gene-modified tumor cells, patients' lymph nodes were harvested; TVDLN lymphocytes were activated and expanded ex vivo with anti-CD3 and interleukin-2 (IL-2), and adoptively transferred to patients in combination with systemic IL-2. Twenty patients, nine with melanoma and 11 with RCC were treated. Tumor was harvested successfully in all 20 patients. Ex vivo gene transfer was performed using lipofection with a lipid: DNA plasmid complex containing the genes for HLA-B7 and beta2-microglobulin. The mean expression of HLA-B7 by autologous tumor cells after gene transfer was 4.53% (range 0.3%-12.1%). Lymph nodes were harvested from all 20 patients with a mean of 53 x 107 and 60 x 107 cells obtained from the gene-modified and unmodified tumor vaccine sites, respectively. Successful expansion of adequate TVDLN was accomplished in 19 of 20 harvests of unmodified vaccines and in 18 of 20 gene-modified vaccines. No major toxicities were noted after vaccination with autologous tumor cells or adoptive transfer of ex vivo activated TVDLN lymphocytes. Typical IL-2-related toxicities were observed in all patients. No objective tumor regressions were observed. MHC class I restricted, tumor-specific cytokine secretion was observed in lymphocytes from TVDLN and the peripheral blood of vaccinated patients.

Intratumoral coinjection of two adenoviral vectors expressing functional interleukin-18 and inducible protein-10, respectively, synergizes to facilitate regression of established tumors

We have constructed two recombinant adenoviral vectors AdVIP-10 and AdVIL-18 expressing the functional chemokine IFN-gamma inducible protein (IP)-10 and cytokine interleukin (IL)-18, respectively. Injection of either AdVIP-10 or AdVIL-18 subcutaneously into tumor nodules derived from the J558 murine myeloma cell line delayed some tumor growth but it was not curative in all cases. Coinjection of these two vectors at the same tumor nodule not only significantly suppressed the tumor growth, but also cured established tumors in 8 of 10 (80% tumor free) mice. The latter treatment stimulated T-cell infiltration into tumors in association with tumor necrosis formation, induced a type 1 immune response and induced the activation of J558 tumor-specific cytotoxic T lymphocytes. Moreover, the antitumor activity of IP-10 and IL-18 combined gene therapy was significantly diminished in mice with depletion of either CD4(+) (50% tumor free) or CD8(+) (40% tumor free) T cells, and completely lost (0% tumor free) in T cell-deficient nude and IFN-gamma knockout mice, indicating the critical roles of T cells and IFN-gamma in this therapeutical model. Taken together, the findings of this study demonstrate that the combined use of two adenoviral vectors expressing IP-10 and IL-18, respectively, synergize to facilitate regression of established tumors. These observations also suggest the potential use of double-recombinant adenoviral vectors expressing chemokines and immunomodulatory cytokines in cancer gene therapy.

Kidney cancer: the Cytokine Working Group experience (1986-2001): part II. Management of IL-2 toxicity and studies with other cytokines

The Cytokine Working Group (CWG) was initially established in 1986 as the Extramural IL-2/LAK Working Group. With funding from the National Cancer Institute (NCI), the CWG was mandated to confirming data regarding the efficacy of the high-dose interleukin-2 (IL2)/lymphokine-activated killer cell (LAK cell) regimen piloted at the NCI in the treatment of renal cell cancer. Since those initial studies, the CWG has conducted a series of clinical trials, often with correlative immunologic investigations, to evaluate combination immunotherapy in attempts to enhance the efficacy of IL-2 or to reduce toxicity. Subsequently, the CWG conducted trials to demonstrate the activity of lower-dose outpatient combination cytokine regimens to help determine their role in the armamentarium of treatment for metastatic renal cell cancer. This has culminated in a phase III randomized trial comparing the activity of high-dose IL-2 with the activity of outpatient IL-2 plus interferon-alpha. The CWG also has honed the management of both high-dose IL-2 and outpatient IL-2 regimens to make these safer in the hands of experienced clinicians. In addition, the CWG has produced a series of carefully conducted clinical trials of new cytokines, again attempting to define their clinical efficacy as anticancer agents. These include studies of IL-4, IL-6, and IL-12. Currently, the CWG is conducting studies with new approaches to IL-2 therapy, as well as planning trials with new agents for treatment of renal cell cancer. This review describes these efforts conducted over the past 15 yr.

IL-12-induced production of IL-10 and interferon-gamma by mononuclear cells in lung cancer-associated malignant pleural effusions

Interleukin (IL)-12 enhances natural killer (NK) activity and induces interferon gamma (IFN-gamma) production. Recently, it was shown that IL-12 induces IL-10 production by human T cells and NK cells, as a negative feedback for IL-12-induced immune responses. In the present study, in order to investigate the functions of host immune cells existing in contact with cancer cells, we examined the effect of IL-12 on the induction of non-major histocompatibility complex (MHC)-restricted killer activity and of IFN-gamma and IL-10 production by pleural and peripheral blood mononuclear cells (MNC), isolated from 40 lung cancer patients and 20 control subjects. IL-12 induced significant killer activity in pleural MNC from lung cancer patients, as well as those in peripheral blood, against a small cell lung cancer cell line (SBC-3). In lung cancer patients, pleural MNC incubated with IL-12 produced more IFN-gamma than blood MNC. In addition, when stimulated with both IL-12 and IL-2, pleural MNC produced more IL-10 than blood MNC. This is the first study reporting that MNC from pleural effusions of patients with lung cancer can produce both type 1 (IFN-gamma) and type 2 (IL-10) cytokines following exposure to IL-2 and IL-12. These observations suggest that control of IL-10 production at the microenvironment level may be important for the efficacy of human lung cancer immunotherapy with IL-12.

In situ adenoviral interleukin 12 gene transfer confers potent and long-lasting cytotoxic immunity in glioma

Interleukin 12 (IL-12) isa cytokine that promotesan antitumor Th1-type pattern of differentiation in mature naïveT cells. Despite its therapeutic success in multiple animal models of cancer, the utility of systemically administered recombinant cytokine has been limited by its toxicity. This has encouraged the development of local IL-12 delivery systems through gene transfer. To determine the effect of local adenoviral delivery of IL- 12 on glioma immunogenicity, mice bearing GL-26 gliomas in the right corpus striatum were treated with direct intratumoral administration of AdmIL-12, AdLacZ, or normal saline. Survival was significantly prolonged in AdmIL-12-treated animals and immunohistochemistry demonstrated robust CD4+ and CD8+ T-cell infiltration in these mice compared to the two control groups. Glioma-infiltrating T lymphocytes from mice that received AdmIL-12 also demonstrated relatively increased, albeit statistically nonsignificant tumor killing. Based on IL-12's known ability to enhance Th1-type cytotoxic antitumor immune responses, we postulate our findings to be a result of localized induction of tumor immunity.

Pre-existing tumor-sensitized T cells are essential for eradication of established tumors by IL-12 and cyclophosphamide plus IL-12

The antitumor immune response activated by IL-12, especially by a combination of cyclophosphamide and IL-12 (Cy+IL-12), is clinically significant in certain experimental tumor models, in that a number of well-established (10-20 mm in diameter) s.c. tumors are completely eradicated. Furthermore, Cy+IL-12 treatment is also able to eradicate well-established grossly detectable experimental lung metastases and advanced ascites tumors. Despite the dramatic antitumor effects seen in some tumor models, Cy+IL-12 fails to induce regression of other established tumors. Characterization of tumor immunogenicity shows that all tumors responding to IL-12 and Cy+IL-12 treatments are immunogenic tumors, in that an antitumor immune response is detectable in tumor-bearing hosts upon tumor establishment. In contrast, none of the nonimmunogenic tumor responds to IL-12 and Cy+IL-12 treatments. Analysis of cellular requirements for successful tumor rejection through an adoptive cell transfer approach reveals that the presence of tumor-sensitized, but not naive, T cells is essential for tumor rejection by IL-12 and Cy+IL-12. Transfer of these tumor-sensitized T cells must be conducted before, but not after, IL-12 treatment in order for tumor rejection to occur. The requirement of sensitized T cells is also tumor specific. In mice bearing immunogenic tumors, the presence of pre-existing tumor-sensitized T cells is demonstrated by adoptive cell transfer experiments using purified spleen T cells from these mice. Results from our study show that Cy+IL-12-based immunotherapy of cancer may be highly effective and that pre-existing tumor-sensitized T cells are essential for the success of the therapy.

Immune rejection of a large sarcoma following cyclophosphamide and IL-12 treatment requires both NK and NK T cells and is associated with the induction of a novel NK T cell population

Combined immunotherapy with cyclophosphamide (Cy) and IL-12, but not IL-12 alone, stimulates eradication of a large established solid tumor (20 mm), MCA207, a methylcholanthrene-induced murine sarcoma. In these studies we demonstrate that NK1.1(+) cells and CD1d-dependent NK T cells each play important yet distinct roles in regression of a large tumor in response to Cy and IL-12, and we define a novel NK T cell subset, selectively increased by this treatment. Mice depleted of NK1.1(+) cells demonstrated more rapid initial tumor growth and prolonged tumor regression following treatment, but tumors were eventually eradicated. In contrast, initial tumor regression following therapy was unimpaired in CD1d(-/-) mice, which are deficient in most NK T cells, but tumors recurred. No tumor regression occurred following Cy and IL-12 therapy in CD1d(-/-) mice that were depleted of NK1.1(+) cells. We found that Cy and IL-12 induced the selective increase in liver and spleen lymphocytes of a unique NK T subpopulation (DX5(+)NK1.1(-)CD3(+)). These cells were not induced by treatment in CD1d(-/-) mice. Our studies demonstrate a contribution of both NK and NK T cells to the Cy- and IL-12-stimulated anti-tumor response. We describe the selective induction of a distinct NK T cell subset by Cy and IL-12 therapy, not seen following IL-12 therapy alone, which we suggest may contribute to the successful anti-tumor response induced by this immunotherapeutic regimen.

Specific down-regulation of interleukin-12 signaling through induction of phospho-STAT4 protein degradation

Interleukin-12 (IL-12) plays a critical role in modulating the function of T lymphocytes and natural killer cells. IL-12 has potent antitumor effects in animal models, mediated primarily by its ability to enhance cytolytic activity and secretion of interferon-gamma (IFN-gamma). Unfortunately, the antitumor effect of IL-12 has not been demonstrated in clinical trials. Repeated administration of IL-12 in humans results in decreasing levels of IFN-gamma secretion. To understand the mechanism underlying this loss of responsiveness, the effect of IL-12 on its own signaling in activated human T cells was examined. These experiments demonstrate that the level of the signal transducer and activator of transcription 4 (STAT4) protein, a critical IL-12 signaling component, is dramatically decreased 24 hours after IL-12 stimulation, whereas levels of STAT4 messenger RNA are not affected. The decrease of STAT4 protein appears to be due to specific degradation of phospho-STAT4, possibly through the proteasome degradation pathway. Decreased levels of STAT4 protein lead to decreased STAT4 DNA-binding activity and reduced proliferation and secretion of IFN-gamma. This down-regulation of STAT4 is specific for IL-12 signaling, presumably owing to the prolonged activation of STAT4 induced by IL-12. IFN-alpha stimulation, which leads to transient phosphorylation of STAT4, does not reduce the level of STAT4 protein. These findings provide new insights into the regulation of IL-12 signaling in human T cells, where IL-12 promotes T(H)1 responses, but persistent IL-12 stimulation may also limit this response. The cellular depletion of STAT4 following prolonged IL-12 stimulation may also explain the loss of responsiveness following the repeated administration of IL-12 in clinical trials. (Blood. 2001;97:3860-3866)

In situ gene therapy for prostate cancer: immunomodulatory approaches

The development of effective treatments for prostate cancer is thwarted by the natural history of the disease. The biological and clinical potential of most individual cancers is uncertain. In many cases the disease will not progress to clinical significance but experimental and clinical studies indicate that prostate cancer can and may metastasis early in the course of the disease from relatively small foci (i.e., not necessarily the largest or index cancer). Localised prostate cancer is potentially curable with localised therapies (radical prostatectomy or irradiation therapy). However, there are no curative therapies for metastatic prostate cancer. Gene therapy, especially those approaches with an immunomodulatory component, may provide additional therapeutic options with the potential to affect both localised and systemic disease. We have pioneered the development and application of in situ gene therapy protocols using adenoviral vectors to transduce specific genes that generate cytotoxic activity and/or a systemic antitumour immune response. In addition we have completed initial studies that demonstrate the therapeutic potential of adenoviral vector-mediated gene modified cell-based vaccines. Our review discusses preclinical studies focused on the development of immunostimulatory in situ gene therapy approaches that hopefully will provide novel and effective treatments for localised and metastatic prostate cancer.

Interleukin 12 gene therapy of cancer by peritumoral injection of transduced autologous fibroblasts: outcome of a phase I study

A phase I dose-escalation clinical trial of peritumoral injections of interleukin 12 (IL-12)-transduced autologous fibroblasts was performed in patients with disseminated cancer for whom effective treatment does not exist. The goals of this study were to assess the safety and toxicities as well as the efficacy, and ancillarily the immunomodulatory effects, of peritumoral IL-12 gene transfer. Primary dermal fibroblasts cultured from the patients were transduced with retroviral vector carrying human IL-12 genes (p35 and p40) as well as the neomycin phosphotransferase gene (TFG-hIL-12-Neo). Patients received four injections at intervals of 7 days. Nine patients were enrolled in this dose-escalation study, with secreted IL-12 doses ranging from 300 ng/24 hr for the first three patients to 1000, 3000, and 5000 ng/24 hr for two patients in each subsequent dosage level. Although a definite statement cannot be made, there appears to be perturbation of systemic immunity. Also, the locoregional effects mediated by tumor necrosis factor alpha (TNF-alpha) and CD8+ T cells were observed with tumor regression. Treatment-related adverse events were limited to mild to moderate pain at the injection site; clinically significant toxicities were not encountered. Transient but clear reductions of tumor sizes were observed at the injected sites in four of nine cases, and at noninjected distant sites in one melanoma patient. Hemorrhagic necrosis of tumors was observed in two melanoma patients. These data indicate that gene therapy by peritumoral injection of IL-12-producing autologous fibroblasts is feasible, and promising in patients with advanced cancer.

Coordination of chemokine and adhesion systems in intratumoral T cell migration responsible for the induction of tumor regression

T cell migration into tumor masses is critical to the process of immunologically induced tumor regression. Like other lymphoid populations, T cells are recruited to inflammatory sites depending on the interaction of T cell integrin receptors with their ligands expressed on vasculature. It is increasingly becoming evident that the adhesive capacity of integrins is upregulated by signals from chemokine receptors. A model of intratumoral T cell migration has been established using IL-12 to induce tumor regression. Focusing on this particular model, we review how IL-12 works to upregulate the expression and/or function of chemokines/chemokine receptors as well as adhesion molecules and to induce collaboration between chemokine and adhesion systems. This article will also describe why such an IL-12-induced activation of chemokine and adhesion systems leads to T cell-mediated tumor regression in some tumor models, but not in others.

Tetracycline-regulatable adenovirus vectors: pharmacologic properties and clinical potential

Stringent control of gene expression in human gene therapy strategies is important for both therapeutic and safety reasons. Replication-defective vectors derived from adenoviruses have been shown to be capable of highly efficient in vivo gene delivery to a wide variety of dividing and nondividing human cells. Here, we review the progress in the development of regulatable adenovirus vectors that allow gene expression to be tightly controlled by low concentrations of tetracyclines. As an example of the potential clinical utility of this technology, we highlight our results obtained in an immunotherapy model for prostate cancer with a tetracycline-regulatable adenovirus vector expressing the cytokine interleukin-12. Recombinant adenovirus vectors with tetracycline-regulatable gene expression provide new opportunities and improved safety for gene therapy applications in humans.

Inhibition of tumor metastasis by adoptive transfer of IL-12-activated Valpha14 NKT cells

A unique lymphocyte lineage, the Valpha14 NKT cells, expresses both NK1.1 and an invariant antigen receptor encoded by Valpha14 and Jalpha281 gene segments. Valpha14 NKT cells play crucial roles in various immune responses, including autoimmune diseases, allergic reactions and anti-tumor immunity. Valpha14 NKT cells were demonstrated to be essential for anti-tumor effect of IL-12 in vivo. Here, we report that adoptive transfer of IL-12-activated Valpha14 NKT cells prevents hepatic metastasis of B16 melanoma. The injection of large amounts of IL-2, IL-4, and IFN-gamma, which are cytokines produced by activated Valpha14 NKT cells, exhibited no significant inhibition of the metastasis of this melanoma. The cells prepared from the liver of IL-12-injected mice expressed a potent cytotoxic activity on B16 melanoma cells in vitro. Although the adoptive transfer of IL-12-activated Valpha14 NKT cells prevents hepatic metastasis of B16 melanoma, activated NK cells from IL-12-injected RAG-1-/- mice failed to inhibit the metastasis of this melanoma. Thus, the anti-tumor effect of IL-12 can be replaced by adoptive transfer of IL-12-activated Valpha14 NKT cells but not by IL-12-activated NK cells, suggesting a minor role of NK cells for the IL-12-mediated anti-tumor effect in this experimental system. Moreover, our studies have suggested the involvement of direct cytotoxic mechanisms rather than cytokine-mediated immune responses at the effector phase of the Valpha14 NKT cell-mediated anti-tumor activity.

Antibody-cytokine fusion proteins for the therapy of cancer

Advances in genetic engineering and expression systems have led to rapid progress in the development of antibodies fused to other proteins. These 'antibody fusion proteins' have novel properties and include antibodies with specificity for tumor associated antigens fused to cytokines such as interleukin-2 (IL2), granulocyte/macrophage colony-stimulating factor (GM-CSF), and interleukin-12 (IL12). The goal of this approach to cancer therapy is to concentrate the cytokine in the tumor microenvironment and in so doing directly enhance the tumoricidal effect of the antibody and/or enhance the host immune response (T-cell, B-cell or NK) against the tumor. In the past decade, multiple antibody-cytokine fusion proteins have been developed with different specificities targeting a broad variety of tumors. These novel molecules retain both antibody and cytokine associated functions. In addition, in animals bearing tumors, antibody-cytokine fusion proteins are able to target the tumor and to elicit a significant anti-tumor response that in some cases results in a complete elimination of the tumor. These results suggest that antibody-cytokine fusion proteins have potential for use in the treatment of human cancer. In the present review, we describe strategies for construction of antibody-cytokine fusion proteins and discuss the properties of several antibody-cytokine fusion proteins with IgG genetically fused to the cytokines IL2, GM-CSF or IL12.

IL-12 treatment of endogenously arising murine brain tumors

A number of recent studies have indicated that T cells can be stimulated to attack transplanted brain tumors in rodent models. As IL-12 has been shown to activate cytotoxic T cell responses, we tested the idea that it might stimulate a T cell response against endogenous brain tumors that arise in SV40 large T Ag transgenic mice (SV11). SV11 mice develop tumors of the choroid plexus, a specialization of the ependymal lining of the brain ventricles. They are a particularly relevant model of human disease, because they are immunocompetent but immunologically tolerant of the tumors. SV11 mice were treated with recombinant murine IL-12 for 10 days. Tumors grew more slowly than in control treated mice, and in some cases were reduced in size, as assessed by magnetic resonance imaging before and after treatment. At the end of treatment, tumors, but not brain parenchyma, exhibited extensive infiltration of activated CD8(+) and CD4(+) T cells. Tumors also showed a reduction in vascular density. Mice treated with IL-12 lived significantly longer than control mice. Tumors that progressed were nearly devoid of T cells, indicating that the T cell response was not sustained. In addition, some mice that had a substantial tumor burden at the beginning of treatment displayed evidence of immunosuppression, which might be related to TGF-ss2 detected in tumors. We conclude that IL-12 treatment can initiate an anti-tumor response even against endogenously arising brain tumors, but factors that will allow a sustained and more effective anti-tumor response need to be determined.

Tumor vaccination that enhances antitumor T-cell responses does not inhibit the growth of established tumors even in combination with interleukin-12 treatment: the importance of inducing intratumoral T-cell migration

Interleukin-12 (IL-12) treatment is effective in the CSA1M but not in the Meth A and CSA1M-variant tumor models. The authors investigated the cause by which IL-12 treatment fails to induce tumor regression in these two tumor models. T cells from CSA1M-bearing mice have high levels of IL-12 responsiveness, whereas cells from Meth A-bearing mice display marginal levels of responsiveness. Because IL-12 responsiveness in T cells is induced after T-cell receptor stimulation, the lack of IL-12 responsiveness suggests that T cells in Meth A-bearing mice are not sensitized to Meth A tumor antigen. Immunization of normal mice with attenuated Meth A tumor cells resulted in a protective immunity, as shown by the rejection of challenged viable Meth A cells. Such an immunization, when performed in Meth A-bearing mice, induced potent IL-12 responsiveness in T cells. Nevertheless, IL-12 treatment in these mice did not inhibit tumor growth. In another IL-12-incurable (CSA1M-variant) model, IL-12 responsiveness was observed before tumor cell immunization. However, IL-12 treatment was ineffective regardless of whether tumor cell immunization was performed. In these two models, the failure of IL-12 treatment to induce tumor regression was associated with the lack of T-cell migration to tumor sites. These results indicate that the sensitization of T cells to tumor antigens and generation of IL-12 responsiveness are insufficient to induce tumor regression when these sensitized T cells are not allowed to migrate to tumor sites.

Therapeutic efficacy of Th1 and Th2 L-selectin--CD4+ tumor-reactive T cells

OBJECTIVE

To evaluate the cytokine secretion profile and therapeutic efficacy of Th1 CD4+ L-selectin-tumor-draining lymph node lymphocytes in the treatment of murine pulmonary metastases.

STUDY DESIGN

Prospective, murine in vivo and in vitro study.

METHODS

B6 mice were injected bilaterally subcutaneously with MCA 205 sarcoma cells to initiate tumor growth. Eleven days later, tumor-draining inguinal lymph nodes were harvested. Single-cell suspensions were prepared and fractionated using magnetically activated cell sorting. Sorted CD4+ L-selectin-lymphocytes were activated with anti-CD3 monoclonal antibody for 48 hours either alone to give a Th1 phenotype, or in the presence of interleukin (IL)-4 and anti-interferon-gamma (alpha-IFN-gamma) monoclonal antibody to elicit a Th2 phenotype. Activated cells were then expanded for 3 days in IL-2. Resulting cells were used to treat 3-day pulmonary metastases. Enzyme-linked immunosorbent assay and intracellular fluorescent-activated cell-sorter (FACS) scanning were used to evaluate the cytokine secretion profiles of these cells.

RESULTS

Activated and expanded L-selectin- CD4+ T cells demonstrated a Th1 cytokine profile and excellent antitumor efficacy. In contrast, L-selectin- CD4+ lymphocytes activated in the presence of IL-4 and alpha-IFN-gamma monoclonal antibody demonstrated a Th2-like profile and significantly (P < .05) poorer antitumor efficacy.

CONCLUSIONS

The cytokine environment during the activation of tumor-draining lymph nodes can influence the therapeutic efficacy of activated L-selectin-, CD4+ T cells. Cell mediated, Th1-dependent immunity appears to play an important role in mediating tumor regression. Culture conditions promoting Th2 cells resulted in T cells associated with diminished antitumor efficacy.

In vitro IL-12 treatment of peripheral blood mononuclear cells from patients with leukemia or myelodysplastic syndromes: increase in cytotoxicity and reduction in WT1 gene expression

Interleukin-12 (IL-12) has potent antitumor activities. We examined whether IL-12 enhanced the cytotoxicity of peripheral blood mononuclear cells (PBMNC) and decreased leukemia cells in 30 patients with leukemia or myelodysplastic syndromes (MDS): 12 acute myeloid leukemia (AML) (five in complete remission (CR) and seven in non-CR); six chronic myeloid leukemia (CML); and 12 MDS (three refractory anemia (RA), eight RA with excess of blasts and one chronic myelomonocytic leukemia). PBMNC from patients and five healthy volunteers were cultured at 5 x 10(5)/ml parallel with or without 100 units/ml of IL-12 for 3 days. Cytotoxicity of PBMNC against K562 cells was assessed by flow cytometry. To quantify the amount of leukemia cells, WT1 mRNA was measured by competitive reverse transcription polymerase chain reaction (RT-PCR), since WT1 mRNA is considered as a marker of minimal residual disease (MRD) in leukemia or MDS. The cytotoxicity of non-IL-12-treated PBMNC of 30 patients was 13.4+/-9.3% at the effector to target (E:T) ratio of 20:1, and significantly lower than that of normal subjects (25.7+/-8.4%). The cytotoxicity increased to 30.6+/-17.9% in the IL-12-treated PBMNC. WT1 mRNA in PBMNC of five healthy volunteers was less than 10(3) copies/microg of total RNA. Following the 3-day IL-12 treatment, mean WT1 mRNA of PBMNC was reduced from 10(4.8) to 10(4.2) copies/microg of total RNA in six CML patients, from 10(5.4) to 10(4.8) copies/microg in 12 MDS patients and from 10(5.0) to 10(4.2) copies/microg in five AML patients in CR, but not reduced in five of seven AML in non-CR. These results showed that IL-12 significantly enhanced PBMNC cytotoxicity and decreased the quantity of leukemia cells in PBMNC of most patients with MDS, CML and AML in CR. IL-12 might be of considerable benefit in the elimination of MRD in patients with hematological malignancies.

The anti-tumor activity of IL-12: mechanisms of innate immunity that are model and dose dependent

IL-12 has been demonstrated to have potent anti-tumor activities in a variety of mouse tumor models, but the relative roles of NK, NKT, and T cells and their effector mechanisms in these responses have not been fully addressed. Using a spectrum of gene-targeted or Ab-treated mice we have shown that for any particular tumor model the effector mechanisms downstream of IL-12 often mimic the natural immune response to that tumor. For example, metastasis of the MHC class I-deficient lymphoma, EL4-S3, was strictly controlled by NK cells using perforin either naturally or following therapy with high-dose IL-12. Intriguingly, in B16F10 and RM-1 tumor models both NK and NKT cells contribute to natural protection from tumor metastasis. In these models, a lower dose of IL-12 or delayed administration of IL-12 dictated a greater relative role of NKT cells in immune protection from tumor metastasis. Overall, both NK and NKT cells can contribute to natural and IL-12-induced immunity against tumors, and the relative role of each population is tumor and therapy dependent.

Differential IL-12 responsiveness of T cells but not of NK cells from tumor-bearing mice in IL-12-responsive versus -unresponsive tumor models

While IL-12 administration induces tumor regression through stimulating T cells in tumor-bearing mice, this IL-12 effect is observed in some but not all tumor models. The present study aimed to compare IL-12 responsiveness of T cells from tumor-bearing mice in IL-12-responsive (CSA1M and OV-HM) and -unresponsive (Meth A) tumor models. Tumor regression in IL-12-responsive tumor models required the participation of T cells, but not of NK1.1(+) cells. Because a NK1.1(+) cell population was the major producer of IFN-gamma, comparable levels of IFN-gamma production were induced in IL-12-responsive and -unresponsive tumor-bearing mice. This indicates that the amount of IFN-gamma produced in tumor-bearing individuals does not correlate with the anti-tumor efficacy of IL-12. In contrast, IL-12 responsiveness of T cells differed between the responsive and unresponsive models: purified T cells from CSA1M/OV-HM-bearing or Meth A-bearing mice exhibited high or low IL-12 responsiveness respectively, when evaluated by the amounts of IFN-gamma produced in response to IL-12. T cells from CSA1M- or OV-HM-bearing but not from Meth A-bearing mice exhibited enhanced levels of mRNA for the IL-12 receptor (IL-12R). These results indicate that a fundamental difference exists in IL-12 responsiveness of T cells between IL-12-responsive and -unresponsive tumor models, and that such a difference is associated with the expression of IL-12R on T cells.

Participation of endogenously produced interferon gamma in interleukin 4-mediated tumor rejection

To elucidate the molecular mechanism underlying IL-4-induced tumor rejection, we challenged mice with a mouse adenocarcinoma cell line, colon 26, genetically engineered to express constitutively IL-4 gene (colon 26/IL-4). Immunocompetent BALB/c mice rejected colon 26/IL-4 cells but not parental cells or cells transduced with a control gene (colon 26/control). Moreover, on rechallenge, parental cells and colon 26/control cells were rejected by normal BALB/c mice that had previously rejected colon 26/IL-4. However, both nude and severe combined immunodeficiency (SCID) mice failed to reject colon 26/IL-4 as well as parental or colon 26/control cells. In contrast, nude mice did reject colon 26/IL-4 after transfer of lymphocytes obtained from the draining lymph nodes of BALB/c mice injected with colon 26/IL-4. These results indicate that challenging mice with colon 26/IL-4 tumor cells resulted in the generation of memory cytotoxic T lymphocytes in the draining lymph nodes. At 3 days after the challenge, IFN-gamma, IL-12 p35, and p40 mRNA expression was selectively enhanced in the draining lymph nodes of mice bearing colon 26/IL-4 cells. Finally, mice deficient in the IFN-gamma gene did not reject colon 26/IL-4 cells. These results suggest that IL-4-induced memory cytotoxic T lymphocyte generation requires IFN-gamma production in the draining lymph nodes, in order to generate a protective immune response.

Paracrine delivery of IL-12 against intracranial 9L gliosarcoma in rats

OBJECT

Interleukin-12 (IL- 12) has potential for the treatment of tumors because it can stimulate an antitumor immune response and possesses antiangiogenic properties. In the study reported here, the authors investigated the therapeutic role of locally delivered IL-12 in a malignant brain tumor model.

METHODS

After genetically engineering 9L gliosarcoma cells to express IL-12 (9L-IL12 cells), the authors used these cells as a source of locally delivered cytokine. First, they investigated the behavior of these cells, which were implanted with the aid of stereotactic guidance into the rat brain, by using serial magnetic resonance imaging and histopathological examination. Second, they assessed the antitumor efficacy of proliferating, as well as nonproliferating (irradiated), 9L-IL12 cells by implanting these cells in animals challenged by wild-type 9L gliosarcoma (9Lwt) cells. The IL-12 expression in brain regions injected with 9L-IL12 was confirmed by reverse transcription-polymerase chain reaction. Last, the authors explored whether animals treated with 9L-IL12 cells developed an antitumor immunological memory by rechallenging the survivors with a second injection of 9Lwt cells. The authors demonstrated that local delivery of IL-12 into the rat brain by genetically engineered cells significantly prolongs survival time in animals challenged intracranially with a malignant glioma.

CONCLUSIONS

These findings support continued efforts to refine local delivery systems of IL-12 in an attempt to bring this therapy to clinical trials.