In vivo studies with interleukin-12 alone and in combination with monocyte colony-stimulating factor and/or fractionated radiation treatment

Preclinical and clinical studies of a tumor targeting IL-12 immunocytokine

The clinical success of immune checkpoint inhibitors (ICIs) has demonstrated the promise and challenges of cancer immunotherapy. There is an unmet need to develop novel cancer therapies that can provide clinical benefit for most patients with solid malignancies, which harbor innate or acquired resistance to ICIs. Interleukin-12 (IL-12) is a promising cytokine for cancer therapy given its direct stimulatory effects on innate and adaptive immunity. However, unfavorable pharmacokinetics and a narrow therapeutic index render recombinant IL-12 (rIL-12) less attractive as a cancer therapy. NHS-IL12 is a fusion protein of IL-12 and NHS76 (human IgG1) antibody engineered to target single and double stranded DNA present in necrotic areas solid tumors. In preclinical tumor models, NHS-IL12 elicited significant Th1 immune activation and tumor suppressive effects, primarily mediated by NK and CD8+ T lymphocytes, with engagement of myeloid immunity. NHS-IL12 is currently being evaluated clinically in combination with various therapeutic modalities, including chemotherapy, radiation therapy, immune checkpoint inhibition, vaccines, and epigenetic modulation. Here we review the preclinical and clinical studies involving NHS-IL12 for the treatment of solid malignancies.

Immune correlates with response in patients with metastatic solid tumors treated with a tumor targeting immunocytokine NHS-IL12

The immunocytokine NHS-IL12 delivers IL-12 to the tumor microenvironment by targeting DNA/histones in necrotic areas. The first-in-human clinical trial administered NHS-IL12 subcutaneously in 59 patients treated every four weeks (Q4W), with a maximum tolerated dose of 16.8 mcg/kg. The phase I study was expanded to include a high-exposure cohort that received bi-weekly treatment (Q2W) with two dose levels of NHS-IL12: 12.0 mcg/kg and 16.8 mcg/kg. Here, patients given NHS-IL12 were analyzed both prior to and early after treatment for effects on 10 serum soluble analytes, complete blood counts, and 158 peripheral immune subsets. Higher levels of immune activation were seen with a dose of 16.8 mcg/kg versus 12.0 mcg/kg in patients in the high-exposure cohort, as evidenced by greater increases in serum IFNγ, TNFα, and soluble PD-1, and greater increases in frequencies of peripheral ki67+ mature natural killer (NK), CD8+T, and NKT cells. Greater immune activation was also seen in the Q2W versus Q4W cohort, as demonstrated by greater increases in pro-inflammatory serum analytes, ki67+ CD8+ T, NK, and NKT cells, intermediate monocytes, and a greater decrease in CD73+ T cells. Specific immune analytes at baseline including lower levels of monocytes and plasmacytoid dendritic cells, and early changes after treatment such as an increase in refined NK cell subsets and total CD8+ T cells, associated with better clinical response. These findings may help to guide future schedule and dosing regimens of clinical studies of NHS-IL12 as monotherapy and in combination therapies.

Intratumoral immunotherapy relies on B and T cell collaboration

Antitumor T cell responses are the primary mediators of cancer immunotherapy. However, many other components of the immune system are needed for efficient T cell responses to be generated. Here, we developed a combinatorial approach where a Toll-like receptor 9 agonist (CpG) and Fc-fused IL-12 protein were injected together into just one of several tumor sites in a mouse. This combination led to body-wide (abscopal) therapeutic responses in multiple cancer models. These systemic responses were dependent not only on T cells but also on B cells. B cells were activated by the treatment and were required for optimal T cell activation. This cross-talk was dependent on MHC and was tumor antigen specific. The addition of an agonistic antibody against OX40 further enhanced T cell activation and therapeutic responses. Our data suggest that the combination of CpG, anti-OX40, and IL-12Fc may have success in patients with cancer and that B and T cell collaboration is crucial for the efficacy of this combination immunotherapy.

Boosting Interleukin-12 Antitumor Activity and Synergism with Immunotherapy by Targeted Delivery with isoDGR-Tagged Nanogold

The clinical use of interleukin-12 (IL12), a cytokine endowed with potent immunotherapeutic anticancer activity, is limited by systemic toxicity. The hypothesis is addressed that gold nanoparticles tagged with a tumor-homing peptide containing isoDGR, an αvβ3-integrin binding motif, can be exploited for delivering IL12 to tumors and improving its therapeutic index. To this aim, gold nanospheres are functionalized with the head-to-tail cyclized-peptide CGisoDGRG (Iso1) and murine IL12. The resulting nanodrug (Iso1/Au/IL12) is monodispersed, stable, and bifunctional in terms of αvβ3 and IL12-receptor recognition. Low-dose Iso1/Au/IL12, equivalent to 18-75 pg of IL12, induces antitumor effects in murine models of fibrosarcomas and mammary adenocarcinomas, with no evidence of toxicity. Equivalent doses of Au/IL12 (a nanodrug lacking Iso1) fail to delay tumor growth, whereas 15 000 pg of free IL12 is necessary to achieve similar effects. Iso1/Au/IL12 significantly increases tumor infiltration by innate immune cells, such as NK and iNKT cells, monocytes, and neutrophils. NK cell depletion completely inhibits its antitumor effects. Low-dose Iso1/Au/IL12 can also increase the therapeutic efficacy of adoptive T-cell therapy in mice with autochthonous prostate cancer. These findings indicate that coupling IL12 to isoDGR-tagged nanogold is a valid strategy for enhancing its therapeutic index and sustaining adoptive T-cell therapy.

Combination of radiation and interleukin 12 eradicates large orthotopic hepatocellular carcinoma through immunomodulation of tumor microenvironment

Immunotherapies have shown promising results in certain cancer patients. For hepatocellular carcinoma (HCC), the multiplicity of an immunotolerant microenvironment within both the tumor, and the liver per se may limit the efficacy of cancer immunotherapies. Since radiation induces immunogenic cell death and inflammatory reactions within the tumor microenvironment, we hypothesized that a combination therapy of radiation and lasting local immunostimulating agents, achieved by intratumoral injection of an adenoviral vector encoding interleukin 12, may reverse the immunotolerant microenvironment within a well-established orthotopic HCC toward a state favorable for inducing antitumor immunities. Our data showed that radiation and IL-12 combination therapy (RT/IL-12) led to dramatic tumor regression in animals bearing large subcutaneous or orthotopic HCC, induced systemic effect against distant tumor, and significantly prolonged survival. Radiation monotherapy induced tumor regression at early times but afterwards most tumors regained exponential growth, while IL-12 monotherapy only delayed tumor growth. Mechanistic studies revealed that RT/IL-12 increased expression of MHC class II and co-stimulatory molecules CD40 and CD86 on tumor-infiltrating dendritic cells, suggesting an improvement of their antigen presentation activity. RT/IL-12 also significantly reduced accumulation of tumor-infiltrating myeloid-derived suppressor cells (MDSCs) and impaired their suppressive functions by reducing production of reactive oxygen species. Accordingly, tumor-infiltrating CD8⁺ T cells and NK cells were significantly activated toward the antitumor phenotype, as revealed by increased expression of CD107a and TNF-α. Together, our data showed that RT/IL-12 treatment could reset the intratumoral immunotolerant state and stimulate activation of antitumor cellular immunity that is capable of eliminating large established HCC tumors.

Abscopal, immunological effects of radiotherapy: Narrowing the gap between clinical and preclinical experiences

Radiotherapy-despite being a local therapy that meanwhile is characterized by an impressively high degree of spatial accuracy-can stimulate systemic phenomena which occasionally lead to regression and rejection of non-irradiated, distant tumor lesions. These abscopal effects of local irradiation have been observed in sporadic clinical case reports since the beginning of the 20th century, and extensive preclinical work has contributed to identify systemic anti-tumor immune responses as the underlying driving forces. Although abscopal tumor regression still remains a rare event in the radiotherapeutic routine, increasing numbers of cases are being reported, particularly since the clinical implementation of immune checkpoint inhibiting agents. Accordingly, interests to systematically exploit the therapeutic potential of radiotherapy-stimulated systemic responses are constantly growing. The present review briefly delineates the history of radiotherapy-induced abscopal effects and the activation of systemic anti-tumor immune responses by local irradiation. We discuss preclinical and clinical reports with specific focus on the corresponding controversies, and we propose issues that should be addressed in the future in order to narrow the gap between preclinical knowledge and clinical experiences.

Interleukin 12: still a promising candidate for tumor immunotherapy?

Interleukin 12 (IL-12) seemed to represent the ideal candidate for tumor immunotherapy, due to its ability to activate both innate (NK cells) and adaptive (cytotoxic T lymphocytes) immunities. However, despite encouraging results in animal models, very modest antitumor effects of IL-12 in early clinical trials, often accompanied by unacceptable levels of adverse events, markedly dampened hopes of the successful use of this cytokine in cancer patients. Recently, several clinical studies have been initiated in which IL-12 is applied as an adjuvant in cancer vaccines, in gene therapy including locoregional injections of IL-12 plasmid and in the form of tumor-targeting immunocytokines (IL-12 fused to monoclonal antibodies). The near future will show whether this renewed interest in the use of IL-12 in oncology will result in meaningful therapeutic effects in a select group of cancer patients.

Radiosensitizing effect of intratumoral interleukin-12 gene electrotransfer in murine sarcoma

Background

Interleukin-12 (IL-12) based radiosensitization is an effective way of tumor treatment. Local cytokine production, without systemic shedding, might provide clinical benefit in radiation treatment of sarcomas. Therefore, the aim was to stimulate intratumoral IL-12 production by gene electrotransfer of plasmid coding for mouse IL-12 (mIL-12) into the tumors, in order to explore its radiosensitizing effect after single or multiple intratumoral gene electrotransfer.

Methods

Solid SA-1 fibrosarcoma tumors, on the back of A/J mice, were treated intratumorally by mIL-12 gene electrotransfer and 24 h later irradiated with a single dose. Treatment effectiveness was measured by tumor growth delay and local tumor control assay (TCD₅₀ assay). With respect to therapeutic index, skin reaction in the radiation field was scored. The tumor and serum concentrations of cytokines mIL-12 and mouse interferon γ (mIFNγ) were measured. Besides single, also multiple intratumoral mIL-12 gene electrotransfer before and after tumor irradiation was evaluated.

Results

Single intratumoral mIL-12 gene electrotransfer resulted in increased intratumoral but not serum mIL-12 and mIFNγ concentrations, and had good antitumor (7.1% tumor cures) and radiosensitizing effect (21.4% tumor cures). Combined treatment resulted in the radiation dose-modifying factor of 2.16. Multiple mIL-12 gene electrotransfer had an even more pronounced antitumor (50% tumor cures) and radiosensitizing (86.7% tumor cures) effect.

Conclusions

Single or multiple intratumoral mIL-12 gene electrotransfer resulted in increased intratumoral mIL-12 and mIFNγ cytokine level, and may provide an efficient treatment modality for soft tissue sarcoma as single or adjuvant therapy to tumor irradiation.

Bladder Cancer Immunotherapy: BCG and Beyond

Mycobacterium bovis bacillus Calmette-Guérin (BCG) has become the predominant conservative treatment for nonmuscle invasive bladder cancer. Its mechanism of action continues to be defined but has been shown to involve a T helper type 1 (Th1) immunomodulatory response. While BCG treatment is the current standard of care, a significant proportion of patients fails or do not tolerate treatment. Therefore, many efforts have been made to identify other intravesical and immunomodulating therapeutics to use alone or in conjunction with BCG. This paper reviews the progress of basic science and clinical experience with several immunotherapeutic agents including IFN-α, IL-2, IL-12, and IL-10.

Controlled systemic release of interleukin-12 after gene electrotransfer to muscle for cancer gene therapy alone or in combination with ionizing radiation in murine sarcomas

BACKGROUND

The present study aimed to evaluate the antitumor effectiveness of systemic interleukin (IL)-12 gene therapy in murine sarcoma models, and to evaluate its interaction with the irradiation of tumors and metastases. To avoid toxic side-effects of IL-12 gene therapy, the objective was to achieve the controlled release of IL-12 after intramuscular gene electrotransfer.

METHODS

Gene electrotransfer of the plasmid pORF-mIL12 was performed into the tibialis cranialis in A/J and C57BL/6 mice. Systemic release of the IL-12 was monitored in the serum of mice after carrying out two sets of intramuscular IL-12 gene electrotransfer of two different doses of plasmid DNA. The antitumor effectiveness of IL-12 gene electrotransfer alone or in combination with local tumor or lung irradiation with X-rays, was evaluated on subcutaneous SA-1 and LPB tumors, as well as on lung metastases.

RESULTS

A synergistic antitumor effect of intramuscular gene electrotransfer combined with local tumor irradiation was observed as a result of the systemic distribution of IL-12. The gene electrotransfer resulted in up to 28% of complete responses of tumors. In combination with local tumor irradiation, the curability was increased by up to 100%. The same effect was observed for lung metastases, where a potentiating factor of 1.3-fold was determined. The amount of circulating IL-12 was controlled by the number of repeats of gene electrotransfer and by the amount of the injected plasmid.

CONCLUSIONS

The present study demonstrates the feasibility of treatment by IL-12 gene electrotransfer combined with local tumor or lung metastases irradiation on sarcoma tumors for translation into the clinical setting.

Cooperative effects of adenoviral vector-mediated interleukin 12 gene therapy with radiotherapy in a preclinical model of metastatic prostate cancer

We investigated the potential benefits of combining adenoviral vector mediated in situ interleukin-12 (AdmIL-12) gene therapy with radiation therapy (XRT) to enhance therapeutic efficacy. In a metastatic mouse prostate cancer cell line, 178-2 BMA, AdmIL-12+XRT demonstrated enhanced therapeutic activities in vitro as determined by clonogenic survival, apoptosis, and mIL-12 levels. At the molecular level, increased expression of tumor necrosis factor-alpha mRNA was specific for the combined therapy. In a subcutaneous 178-2 BMA in vivo model, the combination of AdmIL-12+XRT produced statistically significant tumor growth suppression compared to control vector Adbetagal, Adbetagal XRT, or AdmIL-12 as monotherapy. In addition, significant prolongation of survival was demonstrated for the combination of AdmIL-12+XRT. The combination of AdmIL-12+XRT significantly suppressed both spontaneous and pre-established lung metastases, and led to a prolonged elevation of serum IL-12 and significantly increased natural killer (NK) activities. Importantly, in vivo depletion of NK cells resulted in significant attenuation of the antimetastatic activities of AdmIL-12 alone or AdmIL-12+XRT. These combined effects suggest that AdIL-12 gene therapy together with radiotherapy may achieve maximal tumor control (both local and systemic) in selected prostate cancer patients via radio-gene therapy induced local cytotoxicity and local and systemic antitumor immunity.

Significance of angiogenesis in cancer therapy

BACKGROUND

For most solid tumours, surgery remains the most effective primary treatment. Despite apparently curative resection, significant numbers of patients develop secondary disease due to growth of undetected micrometastases. The ability of a tumour to metastasize is related to the degree of angiogenesis it induces. In addition, micrometastases rely on new vessel formation to provide the nutrients necessary for growth. A better understanding of how tumours acquire their blood supply may lead to more effective adjuvant therapies and improve survival following surgery.

METHODS

A systematic review of the literature on angiogenesis between 1971 and 1997 was performed using the Medline database to ascertain current thinking on angiogenesis and its relevance in oncological surgery.

RESULTS

Angiogenesis is a physiological process subject to autocrine and paracrine regulation which has the potential to become abnormal and play a part in a number of pathological states, including cancer. Increased angiogenic stimuli in the perioperative period, associated with concomitant reduction in tumour-derived antiangiogenic factors following resection of a primary tumour, result in a permissive environment which allows micrometastases to grow.

CONCLUSION

Recognition of the role of angiogenesis in metastatic tumour growth represents a significant development in our understanding of tumour biology. The development of antiangiogenic agents offers new promise in the treatment of malignancy. Such agents may prevent or control the development and growth of primary and metastatic tumours.

T Cell-Mediated, IFN-γ-Facilitated Rejection of Murine B16 Melanomas

The murine melanoma cell line B16.F10 (H-2b) was used to study specific T cell responses that reject tumors. Stable B16 transfectants were established that express viral Ags, either the hepatitis B surface Ag (HBsAg) or the large tumor Ag (T-Ag) of SV40. B16 cells and their transfected sublines were CD40+CD44+ but expressed no (or low levels of the) costimulator molecules CD154 (CD40L), CD48, CD54, CD80, and CD86. Surface expression of MHC class I (Kb, Db) and class II (I-Ab) molecules by B16 cells was low, but strikingly up-regulated by IFN-γ. CD95 (Fas) and CD95 ligand (CD95L (FasL)) were “spontaneously” expressed by B16 cells growing in vitro in serum-free medium; these markers were strikingly up-regulated by IFN-γ. B16 cells coexpressing CD95 and CD95L were irreversibly programed for apoptosis. In vitro, noninduced B16 transfectants stimulated a specific IFN-γ release response, but no cytolytic response (in a 4-h assay) in MHC class I-restricted CTL; in contrast, IFN-γ-induced B16 targets were efficiently and specifically lysed by CTL. In vivo, B16 transfectants were specifically rejected by DNA-vaccinated syngeneic hosts through a T-dependent immune effector mechanism. The tumors showed evidence of massive apoptosis in vivo during the rejection process. The data suggest that CTL-derived IFN-γ enhances an intrinsic suicide mechanism of these tumor cells in addition to facilitating lytic interactions of effectors with tumor targets.

Optimal scheduling of interleukin-12 and fractionated radiation therapy in the murine Lewis lung carcinoma

Interleukin-12 (IL-12), a naturally occurring cytokine, has demonstrated antitumor activity in several murine solid tumors. The Lewis lung carcinoma was used to study the most effective scheduling of recombinant murine interleukin-12 (rmIL-12) administration with fractionated radiation therapy. The effect of the schedule of rmIL-12 administration alone or along with a 1- or 2-week fractionated radiation therapy regimen was examined. Beginning rmIL-12 prior to or at the same time as radiation therapy and extending rmIL-12 through the radiation regimen and beyond produced the longest tumor growth delays. Those treatment regimens which were most effective against the primary tumor were also most effective in decreasing the number of lung metastases on day 20. To further assess the immunotherapeutic effects from rmIL-12 administration, the efficacy of rmIL-12 with fractionated radiation therapy delivered to a right hind-limb tumor was measured as tumor growth delay in an unirradiated left hind-limb tumor. There was some difference in the tumor growth delay between the unirradiated tumor in the animals bearing an irradiated tumor in the contralateral leg, and the tumors in animals receiving rmIL-12 only. Recombinant murine granulocyte-macrophage-colony stimulating factor (rmGM-CSF) was also an antitumor agent active against the Lewis lung carcinoma and produced an additive effect in combination with fractionated radiation therapy in this tumor. rmIL-12 was a radiation sensitizer in the Lewis lung carcinoma. When rmIL-12 (45-microg/kg) and rmGM-CSF (45 microg/kg) were administered together with fractionated radiation therapy, a marked increase in tumor growth delay resulted. This treatment combination also nearly ablated lung metastases on day 20 in these animals. These results may serve as a useful guide in developing clinical protocols, including rmIL-12 and fractionated radiation therapy.

Therapeutic effect of interleukin 12 on mouse haemangiosarcomas is not associated with an increased anti-tumour cytotoxic T-lymphocyte activity

In syngeneic mice, the H5V polyoma middle-T oncogene-transformed endothelioma cell line induces Kaposi's sarcoma-like cavernous haemangiomas that regress transiently, probably because of an anti-tumour immune response, but eventually grow progressively and kill the host. To evaluate the generation of tumour-specific cytotoxic T lymphocytes (CTLs), spleen cells of tumour-bearing mice were restimulated with irradiated H5V cells in mixed leucocyte-tumour cell cultures. Tumour-specific CTLs were demonstrable only when low numbers of H5V stimulator cells were used (<1 H5V cell per 50 splenocytes). We found that H5V cells secrete immunosuppressive mediators because CTL generation was blocked when H5V cells culture supernatants were added to allogeneic mixed leucocyte cultures. As numerous tumour-derived immunosuppressive mediators may interfere with interleukin 12 (IL-12) production, we tested whether IL-12 treatment of the tumour-bearing mice would augment their immune response and thus suppress tumour growth. Indeed, IL-12 inhibited tumour growth and prevented mortality, but did not increase anti-H5V CTL generation either in vitro or in vivo. Moreover, the anti-tumour activity in IL-12-treated mice was abrogated by anti-interferon (IFN)-gamma monoclonal antibody (MAb) co-administration. These results strongly suggest that the anti-tumour effect of IL-12 is principally mediated by IFN-gamma release that in turn blocks H5V cell proliferation and induces the release of factors that suppress angiogenesis.

Requirement for Valpha14 NKT cells in IL-12-mediated rejection of tumors

A lymphocyte subpopulation, the Valpha14 natural killer T (NKT) cells, expresses both NK1.1 and a single invariant T cell receptor encoded by the Valpha14 and Jalpha281 gene segments. Mice with a deletion of the Jalpha281 gene segment were found to exclusively lack this subpopulation. The Valpha14 NKT cell-deficient mice could no longer mediate the interleukin-12 (IL-12)-induced rejection of tumors. Although the antitumor effect of IL-12 was thought to be mediated through natural killer cells and T cells, Valpha14 NKT cells were found to be an essential target of IL-12, and they mediated their cytotoxicity by an NK-like effector mechanism after activation with IL-12.