Combining radiotherapy and immunotherapy: a revived partnership

Primer on immuno-oncology and immune response

Advances in the understanding of the immunogenicity of tumors have provided the basis for immuno-oncology, the development of immunotherapeutic agents that augment the patient's antitumor immunity and disrupt the immune-regulatory circuits that allow tumors to evade the immune system. Two immunomodulatory agents recently have been introduced for the treatment of malignancy: sipuleucel-T and ipilimumab. Unlike cytotoxic chemotherapy, immunotherapies stimulate the patient's immune system to mount or augment existing endogenous antitumor immune responses. Both agents have demonstrated significant improvements in long-term overall survival in patients. Like other immunotherapies, sipuleucel-T and ipilimumab also are characterized by adverse events that manifest as immune-related inflammatory conditions that typically are low grade. Management guidelines have been developed and emphasize early recognition of the signs and symptoms of immune-related adverse events and treatment with corticosteroids. Because these events can manifest even after the cessation of therapy, patients treated with immunotherapies should continue to be followed by their oncology team and other healthcare providers.

[Radiation therapy and immunomodulation: Focus on experimental data]

The immunosuppressive effects of radiation therapy have long been the only ones considered. It has been demonstrated that exposure to ionizing radiation induces the release of tumour antigens which activates both the innate immune system and the adaptive immune response of the host. The purpose of tumour immunotherapy is based on the principle that reversal of tolerance to immunogenic tumours would be able to activate an immune response against tumour cells. Preclinical data and clinical studies early phase suggest a potential therapeutic benefit of immunotherapy combined with radiation therapy. The objective of this article is to review how tumour cells interact with the immune system and how ionizing radiation modulate this interaction and finally the combination of perspectives of immunotherapy and ionizing radiation by focusing on existing clinical data.

Radiotherapy and toll-like receptor agonists

The clinical successes of CTLA4 and PD-1 immune checkpoint blockade in aggressive malignancies such as metastatic melanoma and non-small cell lung carcinoma inaugurate a new era in oncology. Indeed, as opposed to tumor-targeted therapies, it is now clear that immune-targeted therapies designed to enhance the antitumor immune response are a relevant strategy to obtain long-term tumor responses. Interestingly, the study of tumor cell death biology has recently revealed that part of radiotherapy efficacy relies on its ability to trigger an immune response against tumor cells. This "immunogenic cell death" partly relies on the generation of damage-associated molecular patterns, which can stimulate immune sensors such as toll-like receptors. Tumor radiation therapy can therefore be envisioned as a strategy to perform an in situ immunization because it can initiate the release of tumor-associated antigens, deplete immune suppressors, and stimulate antigen-presenting cells via endogenous release of toll-like receptor agonists. Moreover, combinations of radiotherapy with immune checkpoint antibodies are synergistic in preclinical models. The translation of these observations in the clinic is ongoing in early phase I/II trials.

NK Cell-Mediated Antibody-Dependent Cellular Cytotoxicity in Cancer Immunotherapy

Natural killer (NK) cells play a major role in cancer immunotherapies that involve tumor-antigen targeting by monoclonal antibodies (mAbs). NK cells express a variety of activating and inhibitory receptors that serve to regulate the function and activity of the cells. In the context of targeting cells, NK cells can be "specifically activated" through certain Fc receptors that are expressed on their cell surface. NK cells can express FcγRIIIA and/or FcγRIIC, which can bind to the Fc portion of immunoglobulins, transmitting activating signals within NK cells. Once activated through Fc receptors by antibodies bound to target cells, NK cells are able to lyse target cells without priming, and secrete cytokines like interferon gamma to recruit adaptive immune cells. This antibody-dependent cell-mediated cytotoxicity (ADCC) of tumor cells is utilized in the treatment of various cancers overexpressing unique antigens, such as neuroblastoma, breast cancer, B cell lymphoma, and others. NK cells also express a family of receptors called killer immunoglobulin-like receptors (KIRs), which regulate the function and response of NK cells toward target cells through their interaction with their cognate ligands that are expressed on tumor cells. Genetic polymorphisms in KIR and KIR-ligands, as well as FcγRs may influence NK cell responsiveness in conjunction with mAb immunotherapies. This review focuses on current therapeutic mAbs, different strategies to augment the anti-tumor efficacy of ADCC, and genotypic factors that may influence patient responses to antibody-dependent immunotherapies.

ANTI-TUMOR IMMUNE RESPONSES INDUCED BY RADIOTHERAPY: A REVIEW

An anti-tumor immune response is one of the most important factors that can determine treatment response and prognosis of cancer patients. Recent studies have demonstrated that radiotherapy can activate tumor-specific immune responses and that these responses contribute to the therapeutic efficacy. However, the exact mechanisms underlying the radiation-induced immune responses remain unclear. Better understanding of the mechanisms could facilitate the application of immune-activating radiotherapy and provide new treatment strategies. We previously demonstrated that tumor-specific T cell responses could be induced in esophageal cancer patients during and after chemoradiotherapy. Furthermore, in a mouse model, immune responses played an important role in determining the local and systemic therapeutic efficacy of radiotherapy that could be augmented by the immune checkpoint blockade. In this review, radiotherapy-induced immune responses, the mechanisms underlying the induction of those responses, and a practical application of the therapy are discussed.

The tumour microenvironment after radiotherapy: mechanisms of resistance and recurrence

Radiotherapy plays a central part in curing cancer. For decades, most research on improving treatment outcomes has focused on modulating radiation-induced biological effects on cancer cells. Recently, we have better understood that components within the tumour microenvironment have pivotal roles in determining treatment outcomes. In this Review, we describe vascular, stromal and immunological changes that are induced in the tumour microenvironment by irradiation and discuss how these changes may promote radioresistance and tumour recurrence. We also highlight how this knowledge is guiding the development of new treatment paradigms in which biologically targeted agents will be combined with radiotherapy.

Opportunities and challenges of radiotherapy for treating cancer

The past 20 years have seen dramatic changes in the delivery of radiation therapy, but the impact of radiobiology on the clinic has been far less substantial. A major consideration in the use of radiotherapy has been on how best to exploit differences between the tumour and host tissue characteristics, which in the past has been achieved empirically by radiation-dose fractionation. New advances are uncovering some of the mechanistic processes that underlie this success story. In this Review, we focus on how these processes might be targeted to improve the outcome of radiotherapy at the individual patient level. This approach would seem a more productive avenue of treatment than simply trying to increase the radiation dose delivered to the tumour.

TGFβ Is a Master Regulator of Radiation Therapy-Induced Antitumor Immunity

T cells directed to endogenous tumor antigens are powerful mediators of tumor regression. Recent immunotherapy advances have identified effective interventions to unleash tumor-specific T-cell activity in patients who naturally develop them. Eliciting T-cell responses to a patient's individual tumor remains a major challenge. Radiation therapy can induce immune responses to model antigens expressed by tumors, but it remains unclear whether it can effectively prime T cells specific for endogenous antigens expressed by poorly immunogenic tumors. We hypothesized that TGFβ activity is a major obstacle hindering the ability of radiation to generate an in situ tumor vaccine. Here, we show that antibody-mediated TGFβ neutralization during radiation therapy effectively generates CD8(+) T-cell responses to multiple endogenous tumor antigens in poorly immunogenic mouse carcinomas. Generated T cells were effective at causing regression of irradiated tumors and nonirradiated lung metastases or synchronous tumors (abscopal effect). Gene signatures associated with IFNγ and immune-mediated rejection were detected in tumors treated with radiation therapy and TGFβ blockade in combination but not as single agents. Upregulation of programmed death (PD) ligand-1 and -2 in neoplastic and myeloid cells and PD-1 on intratumoral T cells limited tumor rejection, resulting in rapid recurrence. Addition of anti-PD-1 antibodies extended survival achieved with radiation and TGFβ blockade. Thus, TGFβ is a fundamental regulator of radiation therapy's ability to generate an in situ tumor vaccine. The combination of local radiation therapy with TGFβ neutralization offers a novel individualized strategy for vaccinating patients against their tumors.

Combining immunotherapy and anticancer agents: the right path to achieve cancer cure?

Recent clinical trials revealed the impressive efficacy of immunological checkpoint blockade in different types of metastatic cancers. Such data underscore that immunotherapy is one of the most promising strategies for cancer treatment. In addition, preclinical studies provide evidence that some cytotoxic drugs have the ability to stimulate the immune system, resulting in anti-tumor immune responses that contribute to clinical efficacy of these agents. These observations raise the hypothesis that the next step for cancer treatment is the combination of cytotoxic agents and immunotherapies. The present review aims to summarize the immune-mediated effects of chemotherapeutic agents and their clinical relevance, the biological and clinical features of immune checkpoint blockers and finally, the preclinical and clinical rationale for novel therapeutic strategies combining anticancer agents and immune checkpoint blockers.

Ablative Tumor Radiation Can Change the Tumor Immune Cell Microenvironment to Induce Durable Complete Remissions

PURPOSE

The goals of the study were to elucidate the immune mechanisms that contribute to desirable complete remissions of murine colon tumors treated with single radiation dose of 30 Gy. This dose is at the upper end of the ablative range used clinically to treat advanced or metastatic colorectal, liver, and non-small cell lung tumors.

EXPERIMENTAL DESIGN

Changes in the tumor immune microenvironment of single tumor nodules exposed to radiation were studied using 21-day (>1 cm in diameter) CT26 and MC38 colon tumors. These are well-characterized weakly immunogenic tumors.

RESULTS

We found that the high-dose radiation transformed the immunosuppressive tumor microenvironment resulting in an intense CD8(+) T-cell tumor infiltrate, and a loss of myeloid-derived suppressor cells (MDSC). The change was dependent on antigen cross-presenting CD8(+) dendritic cells, secretion of IFNγ, and CD4(+)T cells expressing CD40L. Antitumor CD8(+) T cells entered tumors shortly after radiotherapy, reversed MDSC infiltration, and mediated durable remissions in an IFNγ-dependent manner. Interestingly, extended fractionated radiation regimen did not result in robust CD8(+) T-cell infiltration.

CONCLUSIONS

For immunologically sensitive tumors, these results indicate that remissions induced by a short course of high-dose radiotherapy depend on the development of antitumor immunity that is reflected by the nature and kinetics of changes induced in the tumor cell microenvironment. These results suggest that systematic examination of the tumor immune microenvironment may help in optimizing the radiation regimen used to treat tumors by adding a robust immune response.

Present and future of immune checkpoint blockade: Monotherapy to adjuvant approaches

Immune regulation of aggressive tumor growth is often outpaced by tumor up-regulation of ligands that inhibit effector immune responses through the activation of immune checkpoints. A few of such checkpoints include programmed death-1 (PD-1), cytotoxic T lymphocyte associated antigen-4 (CTLA-4), lymphocyte activation gene-3, T-cell immunoglobulin and mucin protein-3, Glucocorticoid-induced TNFR family-related receptor (GITR), and killer cell immunoglobulin like receptor. With the exception of GITR, after binding to their respective ligands these checkpoints induce down-modulation of immune responses to prevent autoimmunity. However, such immune mechanisms are co-opted by tumors to allow rapid tumor cell proliferation. Pre-clinical studies in antibody blockade of PD-1 and CTLA-4 have led to promising augmentation of effector immune responses in murine tumor models, and human antibodies against PD-1 and CTLA-4 alone or in combination have demonstrated tumor regression in clinical trials. The development of immune checkpoint blockade as a potential future immunotherapy has led to increasing interest in combining treatment modalities. Combination checkpoint blockade with chemotherapy and radiation therapy has shown synergistic effects in pre-clinical and clinical studies, and combination checkpoint blockade with bacterial vaccine vectors have produced increased effector immune responses in pre-clinical models. The future of immune checkpoint blockade may be as a powerful adjuvant alongside the current standard of care.

The role of checkpoints in the treatment of GBM

Targeted immunotherapy is founded on the principle that augmentation of effector T cell activity in the tumor microenvironment can translate to tumor regression. Targeted checkpoint inhibitors in the form of agonist or antagonist monoclonal antibodies have come to the fore as a promising strategy to activate systemic immunity and enhance T cell activity by blocking negative signals, enhancing positive signals, or altering the cytokine milieu. This review will examine several immune checkpoints and checkpoint modulators that play a role in cancer pathogenesis, with an emphasis on malignant gliomas.

Radiation meets immunotherapy - a perfect match in the era of combination therapy?

PURPOSE

This review focuses on recent advances in the field of combining radiation with immunotherapy for the treatment of malignant diseases, since various combinatorial cancer therapy approaches have lately proven highly successful.

RESULTS

With initial case reports and anecdotes progressively converting into solid clinical data, interest in cancer immunotherapy (CIT) has risen steeply. Especially immune checkpoint blockade therapies have recently celebrated tremendous successes in the treatment of severe malignancies resistant to conventional treatment strategies. Nevertheless, the high variability of patient responses to CIT remains a major hurdle, clearly indicating an urgent need for improvement. It has been suggested that successful cancer therapy most probably involves combinatorial treatment approaches. Radiotherapy (RT) has been proposed as a powerful partner for CIT due to its broad spectrum of immune modulatory characteristics. Several preclinical studies, supported by an increasing number of clinical observations, have demonstrated synergistic interactions between RT and CIT resulting in significantly improved therapy outcomes.

CONCLUSIONS

Numerous reports have shown that radiation is capable of tipping the scales from tumor immune evasion to elimination in different tumor types. The next puzzle to be solved is the question of logistics - including types, schedule and dosage of combinatorial RT and CIT strategies.

Harnessing the potential of radiation-induced immune modulation for cancer therapy

The conventional use of radiotherapy is for local tumor control. Radiotherapy of the primary tumor can prevent the development of distant metastases, but this modality is generally not effective for treating preexisting systemic disease. However, radiation-induced tumor destruction may be considered a novel strategy for in situ cancer vaccination, in which tumor antigens released from dying tumor cells may be presented in an immunostimulatory context. Moreover, radiation has been demonstrated to induce immunogenic modulation in various tumor types by altering the biology of surviving cells to render them more susceptible to T cell-mediated killing. Finally, radiotherapy typically has a favorable toxicity profile and is associated with the absence of systemic immunosuppression. Together, these properties suggest that radiotherapy may serve as an important component of combinatorial immunotherapies aimed at augmenting systemic antitumor immunity. Here, we provide an overview of the radiation-induced modulations of the immune system that may be harnessed for cancer therapy.

NHS-IL2 combined with radiotherapy: preclinical rationale and phase Ib trial results in metastatic non-small cell lung cancer following first-line chemotherapy

BACKGROUND

NHS-IL2 (selectikine, EMD 521873, MSB0010445) consists of human NHS76 (antibody specific for necrotic DNA) fused to genetically modified human interleukin 2 (IL-2) and selectively activates the high-affinity IL-2 receptor. Based on an evolving investigational concept to prime the tumor microenvironment with ionizing radiation prior to initiating immunotherapy, 2 related studies were conducted and are reported here. The first, a preclinical study, tests the systemic effect of the immunocytokine NHS-IL2 and radiotherapy in a lung carcinoma animal model; the second, a phase Ib trial in patients with metastatic non-small cell lung carcinoma (NSCLC), was designed to determine the safety and tolerability of NHS-IL2 in combination with radiotherapy directly following first-line palliative chemotherapy.

METHODS

Tumor-bearing C57Bl/6 mice were treated with NHS-IL2 alone (5 mg/kg; days 7-9), fractionated radiotherapy (3.6 Gy; days 0-4) plus cisplatin (4 mg/kg; day 0), or the triple combination. Metastatic NSCLC patients who achieved disease control with first-line palliative chemotherapy were enrolled in the phase Ib trial. Patients received local irradiation (5x 4 Gy) of a single pulmonary nodule. Dose-escalated NHS-IL2 was administered as 1-h intravenous infusion on 3 consecutive days every 3 weeks.

RESULTS

NHS-IL2 plus radiotherapy induced immune response activation and complete tumor growth regressions in 80%-100% of mice. In patients with metastatic NSCLC treated with NHS-IL2 (3, 3, and 7 patients in the 0.15-mg/kg, 0.30-mg/kg, and 0.45-mg/kg cohorts, respectively), maximum tolerated dose was not reached. Most frequently reported adverse events were fatigue, anorexia, and rash. Transient increases in leukocyte subsets were observed. In 3 patients, thyroid gland dysfunction occurred. No objective responses were reported; long-term survival was observed in 2 patients, including 1 patient with long-term tumor control.

CONCLUSIONS

Combining NHS-IL2 with radiotherapy achieved synergistic antitumor activity in preclinical studies, supporting the use in lung cancer patients. This combination was well tolerated and 2 of 13 patients achieved long-term survival.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00879866.

Building immunity to cancer with radiation therapy

Over the last decade there has been a dramatic shift in the focus of cancer research toward understanding how the body's immune defenses can be harnessed to promote the effectiveness of cytotoxic anti-cancer therapies. The ability of ionizing radiation to elicit anti-cancer immune responses capable of controlling tumor growth has led to the emergence of promising combination-based radio-immunotherapeutic strategies for the treatment of cancer. Herein we review the immunoadjuvant properties of localized radiation therapy and discuss how technological advances in radio-oncology and developments in the field of tumor-immunotherapy have started to revolutionize the therapeutic application of radiotherapy.

In-situ tumor vaccination: Bringing the fight to the tumor

After decades of development in the shadow of traditional cancer treatment, immunotherapy has come into the spotlight. Treatment of metastatic tumors with monoclonal antibodies to T cell checkpoints like programed cell death 1 (PD-1) or its ligand, (PD-L1), have resulted in significant clinical responses across multiple tumor types. However, these therapies fail in the majority of patients with solid tumors, in particular those who lack PD1(+)CD8(+) tumor-infiltrating lymphocytes within their tumors. Intratumoral "in situ vaccination" approaches seek to enhance immunogenicity, generate tumor infiltrating lymophcytes (TIL) and drive a systemic anti-tumor immune response, directed against "unvaccinated," disseminated tumors. Given the emerging picture of intratumoral immunotherapy as safe and capable of delivering systemic efficacy, it is anticipated that these approaches will become integrated into future multi-modality therapy.

Radiotherapy combined with the immunocytokine L19-IL2 provides long-lasting antitumor effects

PURPOSE

Radiotherapy modifies the tumor microenvironment and causes the release of tumor antigens, which can enhance the effect of immunotherapy. L19 targets the extra domain B (ED-B) of fibronectin, a marker for tumor neoangiogenesis, and can be used as immunocytokine when coupled to IL2. We hypothesize that radiotherapy in combination with L19-IL2 provides an enhanced antitumor effect, which is dependent on ED-B expression.

EXPERIMENTAL DESIGN

Mice were injected with syngeneic C51 colon carcinoma, Lewis lung carcinoma (LLC), or 4T1 mammary carcinoma cells. Tumor growth delay, underlying immunologic parameters, and treatment toxicity were evaluated after single-dose local tumor irradiation and systemic administration of L19-IL2 or equimolar controls.

RESULTS

ED-B expression was high, intermediate, and low for C51, LLC, and 4T1, respectively. The combination therapy showed (i) a long-lasting synergistic effect for the C51 model with 75% of tumors being cured, (ii) an additive effect for the LLC model, and (iii) no effect for the 4T1 model. The combination treatment resulted in a significantly increased cytotoxic (CD8(+)) T-cell population for both C51 and LLC. Depletion of CD8(+) T cells abolished the benefit of the combination therapy.

CONCLUSIONS

These data provide the first evidence for an increased therapeutic potential by combining radiotherapy with L19-IL2 in ED-B-positive tumors. This new opportunity in cancer treatment will be investigated in a phase I clinical study for patients with an oligometastatic solid tumor (NCT02086721). An animation summarizing our results is available at https://www.youtube.com/watch?v=xHbwQuCTkRc.

Multi-institutional phase I study of low-dose ultra-fractionated radiotherapy as a chemosensitizer for gemcitabine and erlotinib in patients with locally advanced or limited metastatic pancreatic cancer

PURPOSE

Gemcitabine (G) has been shown to sensitize pancreatic cancer to radiotherapy but requires lower doses of G and thus delays aggressive systemic treatment, potentially leading to distant failure. We initiated a phase I trial combining ultra-fractionated low-dose radiotherapy with full dose G and erlotinib in the treatment of patients with advanced pancreatic cancer.

METHODS

Patients with locally advanced or metastatic pancreatic cancer confined to the abdomen and an ECOG performance status (PS) of 0-1 who had received 0-1 prior regimens (without G or E) and no prior radiotherapy were eligible. Patients were treated in 21 day cycles with G IV days 1 & 8, E once PO QD, and twice daily RT fractions separated by at least 4h on days 1, 2, 8, and 9. Whole abdominal RT fields were used. Primary endpoint was to define dose limiting toxicity (DLT) and the maximum tolerated dose (MTD).

RESULTS

27 patients (median age 64 years and 15 male) were enrolled between 11/24/08 and 4/12/12. 1 patient withdrew consent prior to receiving any protocol therapy. 17 patients had a PS of 1. The majority of patients were stage IV. One DLT was noted out of 7 patients at dose level (DL) 1. Subsequently no DLTs were noted in 3 patients each enrolled at DL2-4 or 11 patients in the expansion cohort. The majority of grade 3 toxicities were hematologic with 1 grade 5 bowel perforation in dose level 1 in cycle 4. Best response in 24 evaluable patients: PR (8), stable (15), PD 1. Median survival for the entire group was 9.1 months.

CONCLUSION

This phase I study combining low-dose ultra-fractionated RT as a sensitizer to full dose G plus E was well tolerated with encouraging efficacy. This represents a novel strategy worthy of further investigation in advanced pancreatic cancer patients.

Sequential intranodal immunotherapy induces antitumor immunity and correlated regression of disseminated follicular lymphoma

Advanced stage follicular lymphoma (FL) is incurable by conventional therapies. In the present pilot clinical trial, we explored the efficacy and immunogenicity of a novel in situ immunotherapeutic strategy. Fourteen patients with untreated or relapsed stage III/IV FL were included and received local radiotherapy to solitary lymphoma nodes and intranodal injections of low-dose rituximab (5 mg), immature autologous dendritic cells, and granulocyte-macrophage colony-stimulating factor at the same site. The treatment was repeated 3 times targeting different lymphoma nodes. Primary end points were clinical responses and induction of systemic immunity. Five out of 14 patients (36%) displayed objective clinical responses, including 1 patient with cutaneous FL who showed regression of skin lesions. Two of the patients had durable complete remissions. Notably, the magnitude of vaccination-induced systemic CD8 T-cell-mediated responses correlated closely with reduction in total tumor area (r = 0.71, P = .006), and immune responders showed prolonged time to next treatment. Clinical responders did not have a lower tumor burden than nonresponders pretreatment, suggesting that the T cells could eliminate large tumor masses once immune responses were induced. In conclusion, the combined use of 3 treatment modalities, and in situ administration in single lymphoma nodes, mediated systemic T-cell immunity accompanied by regression of disseminated FL. The trial was registered at www.clinicaltrials.gov as #NCT01926639.

The future of glioblastoma therapy: synergism of standard of care and immunotherapy

The current standard of care for glioblastoma (GBM) is maximal surgical resection with adjuvant radiotherapy and temozolomide (TMZ). As the 5-year survival with GBM remains at a dismal <10%, novel therapies are needed. Immunotherapies such as the dendritic cell (DC) vaccine, heat shock protein vaccines, and epidermal growth factor receptor (EGFRvIII) vaccines have shown encouraging results in clinical trials, and have demonstrated synergistic effects with conventional therapeutics resulting in ongoing phase III trials. Chemoradiation has been shown to have synergistic effects when used in combination with immunotherapy. Cytotoxic ionizing radiation is known to trigger pro-inflammatory signaling cascades and immune activation secondary to cell death, which can then be exploited by immunotherapies. The future of GBM therapeutics will involve finding the place for immunotherapy in the current treatment regimen with a focus on developing strategies. Here, we review current GBM therapy and the evidence for combination of immune checkpoint inhibitors, DC and peptide vaccines with the current standard of care.

Radiotherapy as an immunological booster in patients with metastatic melanoma or renal cell carcinoma treated with high-dose Interleukin-2: evaluation of biomarkers of immunologic and therapeutic response

Background

Tumor cells killed by radiation therapy (RT) are a potentially good source of antigens for dendritic cell (DC) uptake and presentation to T-cells. RT upregulates cell death receptors such as Fas/CD95 and MHC-I, induces the expression of co-stimulatory molecules on tumor cells, and promotes production of pro-inflammatory cytokines. High-dose interleukin-2 (HD-IL-2) bolus has been shown to obtain objective response rates ranging from 15% to 17% in patients with metastatic melanoma or renal cell carcinoma (RCC), with 6% to 8% of cases experiencing a durable complete response. However, HD-IL-2 is also associated with severe side-effects; if it is to remain a component of the curative treatment strategy in patients with metastatic melanoma or RCC, its therapeutic efficacy must be improved and patients who are most likely to benefit from treatment must be identified a priori. We designed a clinical study combining immunomodulating RT and HD-IL-2 to evaluate their clinical and immunological efficacy and to explore the predictive and prognostic value of 1) tumor-specific immune response and 2) serum levels of proangiogenic cytokines.

Methods/design

The primary endpoint of this proof-of-principle phase II study is immune response. Secondary endpoints are the identification of biomarkers potentially predictive of response, toxicity, response rate and overall survival. Three daily doses of booster radiotherapy (XRT) at 6–12 Gy will be administered to at least one metastatic field on days −3 to −1 before the first and third cycle. Treatment with IL-2 (dose 18 MIU/m2/day by continuous IV infusion for 72 hours) will start on day +1 and will be repeated every 3 weeks for up to 4 cycles and then every 4 weeks for a further 2 cycles. Immune response against tumor antigens expressed by melanoma and/or RCC will be evaluated during treatment. Circulating immune effectors and regulators, e.g. cytotoxic T lymphocytes and regulatory T cells, as well as serum levels of proangiogenic/proinflammatory cytokines will also be quantified.

Discussion

This study aims to evaluate the potential immunological synergism between HD-IL-2 and XRT, and to identify biomarkers that are predictive of response to IL-2 in order to spare potentially non responding patients from toxicity.

Trial registration

EudraCT no. 2012-001786-32

ClinicalTrials.gov Identifier: NCT01884961

Stereotactic ablative body radiotherapy combined with immunotherapy: present status and future perspectives

Radiotherapy is along with surgery and chemotherapy one of the prime treatment modalities in cancer. It is applied in the primary, neoadjuvant as well as the adjuvant setting. Radiation techniques have rapidly evolved during the past decade enabling the delivery of high radiation doses, reducing side-effects in tumour-adjacent normal tissues. While increasing local tumour control, current and future efforts ought to deal with microscopic disease at a distance of the primary tumour, ultimately responsible for disease-progression. This review explores the possibility of bimodal treatment combining radiotherapy with immunotherapy.

The optimal partnership of radiation and immunotherapy: from preclinical studies to clinical translation

The main role of the immune system is to restore tissue homeostasis when altered by pathogenic processes, including neoplastic transformation. Immune-mediated tumor rejection has been recognized as an extrinsic tumor suppressor mechanism that tumors need to overcome to progress. By the time a tumor becomes clinically apparent it has successfully escaped immune control by establishing an immunosuppressive microenvironment. Ionizing radiation applied locally to a tumor alters these tumor-host interactions. Accumulating evidence indicates that standard therapeutic doses of radiation have the potential to recover tumor immunogenicity and convert the tumor into an in situ personalized vaccine. Radiotherapy induces an immunogenic tumor cell death promoting cross-presentation of tumor-derived antigens by dendritic cells to T cells. In addition, radiotherapy stimulates chemokine-mediated recruitment of effector T cells to the tumor, and cellular recognition and killing by T cells that is facilitated by upregulation of major histocompatibility antigens, NKG2D ligands, adhesion molecules and death receptors. Despite these effects, radiotherapy alone is only rarely capable of generating enough proinflammatory signals to sufficiently overcome suppression, as it can also activate immunosuppressive factors. However, our group and others have shown that when combined with targeted immunotherapy agents radiotherapy significantly contributes to a therapeutically effective anti-tumor immune response. To illustrate this partnership between radiation and immunotherapy we will discuss as an example our experience in preclinical models and the molecular mechanisms identified. Additionally, the clinical translation of these combinations will be discussed.

In vivo effects of lattice radiation therapy on local and distant lung cancer: potential role of immunomodulation

Radiation is a potent immune-modulator that elicits cell death upon tumor, stromal and angiogenic compartments of tumor microenvironment. Here, we test a novel approach of high-dose radiation delivery using three dimensional volume based lattice radiation therapy (LRT) to understand the impact of different volume irradiation in eliciting both local and metastatic/distant tumor control through modulation of tumor immune micro-environment. To study such effects of LRT, tumors were implanted in both hind legs of C57BL/6 mice using Lewis lung carcinoma 1 (LLC1) cells. Mice were divided into five groups: untreated; partial tumor volume groups included two 10% vertices, one 20% vertex and one 50% vertex of the total tumor volume; and 100% open-field irradiation. Tumors implanted in the left flank were irradiated with a single dose of 20 Gy while the tumors in the right flank were unirradiated. Tumor growth and regression as well as immune responses (such as Th1 and Th2; T-cell infiltration) were determined after radiation treatment. Results demonstrated that both 100% open-field irradiation and 20% volume irradiation (in two 10% volumes) resulted in significant growth delay in the irradiated tumor. Further, all types of radiation exposures, partial or 100% volume, demonstrated distal effectiveness, however, 20% volume irradiation (in two 10% volumes) and 50% tumor volume irradiation led to maximum growth delay. Mice treated with partial tumor volume radiation induced a robust IFN-γ and Th1 response when compared to whole-tumor irradiation and down-modulated Th2 functions. The presence of increased CD3+ cells and TRAIL in partially irradiated tumor volumes correlated well with tumor growth delay. Further, serum obtained from any of the LRT treated mice caused growth inhibition of endothelial cells when compared to serum obtained from either untreated or open-field irradiated groups. These results indicate that high-dose partial volume irradiation can cause an improved distant effect than the total tumor volume irradiation through activating the host immune system.

Focal radiation therapy combined with 4-1BB activation and CTLA-4 blockade yields long-term survival and a protective antigen-specific memory response in a murine glioma model

Background

Glioblastoma (GBM) is the most common malignant brain tumor in adults and is associated with a poor prognosis. Cytotoxic T lymphocyte antigen -4 (CTLA-4) blocking antibodies have demonstrated an ability to generate robust antitumor immune responses against a variety of solid tumors. 4-1BB (CD137) is expressed by activated T lymphocytes and served as a co-stimulatory signal, which promotes cytotoxic function. Here, we evaluate a combination immunotherapy regimen involving 4-1BB activation, CTLA-4 blockade, and focal radiation therapy in an immune-competent intracranial GBM model.

Methods

GL261-luciferace cells were stereotactically implanted in the striatum of C57BL/6 mice. Mice were treated with a triple therapy regimen consisted of 4-1BB agonist antibodies, CTLA-4 blocking antibodies, and focal radiation therapy using a small animal radiation research platform and mice were followed for survival. Numbers of brain-infiltrating lymphocytes were analyzed by FACS analysis. CD4 or CD8 depleting antibodies were administered to determine the relative contribution of T helper and cytotoxic T cells in this regimen. To evaluate the ability of this immunotherapy to generate an antigen-specific memory response, long-term survivors were re-challenged with GL261 glioma en B16 melanoma flank tumors.

Results

Mice treated with triple therapy had increased survival compared to mice treated with focal radiation therapy and immunotherapy with 4-1BB activation and CTLA-4 blockade. Animals treated with triple therapy exhibited at least 50% long-term tumor free survival. Treatment with triple therapy resulted in a higher density of CD4⁺ and CD8⁺ tumor infiltrating lymphocytes. Mechanistically, depletion of CD4⁺ T cells abrogated the antitumor efficacy of triple therapy, while depletion of CD8⁺ T cells had no effect on the treatment response.

Conclusion

Combination therapy with 4-1BB activation and CTLA-4 blockade in the setting of focal radiation therapy improves survival in an orthotopic mouse model of glioma by a CD4⁺ T cell dependent mechanism and generates antigen-specific memory.

Treatment of 4T1 metastatic breast cancer with combined hypofractionated irradiation and autologous T-cell infusion

The goal of this study was to determine whether a combination of local tumor irradiation and autologous T-cell transplantation can effectively treat metastatic 4T1 breast cancer in mice. BALB/c mice were injected subcutaneously with luciferase-labeled 4T1 breast tumor cells and allowed to grow for 21 days, at which time metastases appeared in the lungs. Primary tumors were treated at that time with 3 daily fractions of 20 Gy of radiation each. Although this approach could eradicate primary tumors, tumors in the lungs grew progressively. We attempted to improve efficacy of the radiation by adding autologous T-cell infusions. Accordingly, T cells were purified from the spleens of tumor-bearing mice after completion of irradiation and cryopreserved. Cyclophosphamide was administered thereafter to induce lymphodepletion, followed by T-cell infusion. Although the addition of cyclophosphamide to irradiation did not improve survival or reduce tumor progression, the combination of radiation, cyclophosphamide and autologous T-cell infusion induced durable remissions and markedly improved survival. We conclude that the combination of radiation and autologous T-cell infusion is an effective treatment for metastatic 4T1 breast cancer.

Radiation as immunomodulator: implications for dendritic cell-based immunotherapy

The last decade has witnessed significant progress in the field of cancer immunotherapy. This has, in part, been driven by a growing recognition that elements of the innate immune response can be harnessed to induce robust immunity against tumor-associated targets. Nonetheless, as clinically effective immunotherapy for the majority of cancers remains a distant goal, attention has shifted toward multimodality approaches to cancer therapy, sometimes combining novel immunotherapeutics and conventional therapeutics. The traditional view of radiation therapy as immunosuppressive has been challenged, prompting a re-evaluation of its potential as an adjunct to, or even a component of immunotherapy. Radiation therapy may enhance expression of tumor-associated antigens, induce targeting of tumor stroma, diminish regulatory T-cell activity and activate effectors of innate immunity such as dendritic cells through Toll-like receptor (TLR)-dependent mechanisms. Here, we review recent progress in the field of dendritic cell-based immunotherapy, evidence for radiation-induced antitumor immunity and TLR signaling and the results of efforts to rationally integrate radiation into dendritic cell-based immunotherapy strategies.

Unlocking the combination: potentiation of radiation-induced antitumor responses with immunotherapy

There is increasing evidence of the potential for radiation therapy to generate antitumor immune responses. The mechanisms of this immune-activating potential include actions on tumor cells such as immunogenic cell death and phenotypic change. Radiation modulates tumor cell surface expression of cell death receptors, tumor-associated antigens and adhesion molecules. This process of immunomodulation sensitizes tumor cells to immune-mediated killing. Radiation also affects immune compartments, including antigen-presenting cells, cytotoxic T lymphocytes and humoral immunity, leading to specific antitumor immune responses. Recognizing the importance of immunity as a potentiator of response to radiation leads to rational augmentation of antitumor immunity by combining radiation and immunotherapy. Targeted immunotherapy manipulates the immune system in a way that best synergizes with radiation. This article discusses the ability of radiation monotherapy to induce antitumor immunity, with a focus on the effect of radiation on antigen-presenting cells and cytotoxic T lymphocytes. We define two important responses generated by tumor cells, immunogenic cell death and immunomodulation, both of which are radiation dose-dependent. In conclusion, we describe the translation of several combination therapies from the preclinical to the clinical setting and identify opportunities for further exploration.

Radiation therapy combined with Listeria monocytogenes-based cancer vaccine synergize to enhance tumor control in the B16 melanoma model

Conceptually, the immune system may profoundly influence the efficacy of radiation therapy. Compelling evidence has recently emerged revealing the capacity of local radiation therapy (RT) to induce antitumor immune responses and sparked interest in combining RT with immunotherapy to promote tumor-specific immunity. A Listeria monocytogenes (Lm)-based cancer vaccine engineered to express tumor-associated antigen has been shown to effectively retard tumor growth by cell-mediated immune mechanisms. We hypothesized that combining RT and Lm vaccine will result in synergistic effects that enhance tumor control. Collectively, our data demonstrate that combination therapy significantly delayed B16 melanoma tumor growth by a mechanism partly dependent on CD8⁺ T cells. Radiotherapy and Lm vaccine each induce different aspects of antitumor immunity, resulting in an overall increase in intratumoral numbers of activated T cells, antigen-specific CD8⁺ T cells, natural killer (NK) cells and levels of effector molecules, such as interferon γ (IFNγ) and granzyme B. Thus, radiation and Lm vaccine combination therapy is a promising new strategy for the treatment of malignant disease, and further understanding of the mechanisms that underlie efficacy is required to optimize the dosage and schedule for administering the two treatments.

Flagellin and LPS each restores rat lymphocyte populations after colorectal irradiation

Radiation-induced gastrointestinal toxicity, including its shift of the immune balance, remains a major limitation to delivering tumoricidal doses of abdominal radiation therapy. This study evaluates the effect on the colon's innate and adaptive immune responses to moderate irradiation doses and the therapeutic possibilities of maintaining immune homeostasis. We investigated whether administration of the TLR4 agonist LPS or of the TLR5 agonist flagellin, 3 days after a single 20-Gy colorectal irradiation, modified recruitment of neutrophils, NK cells, or CD4⁺ or CD8⁺ T cells, 7 days postirradiation. Flow cytometric analysis showed that LPS and flagellin reduced irradiation-induced neutrophil infiltration and normalized NK frequency. LPS normalized the CD4⁺ population and enhanced the CD8⁺ population, whereas flagellin maintained the radiation-induced elevation in the frequencies of both. Irradiation also modified TLR4 and TLR5 expression on the surface of both populations, but LPS and flagellin each subsequently normalized them. LPS and flagellin were strong inducers of Th1 cytokines (IL-12p35, IL-12p40, and IFN-γ) and thus, contributed to a shift from the Th2 polarization induced by irradiation toward a Th1 polarization, confirmed by an increase of the T-bet:GATA3 ratio, which assesses the Th1 or Th2 status in mixed cell populations. LPS and flagellin treatment resulted in overexpression of FoxP3, IL-2Rα (CD25), IL-2, and OX40, all expressed specifically and involved in high levels of Treg cell expansion. We observed no variation in Treg function-related expression of IL-10 or CTLA-4. These data suggest that the use of TLR ligands limits the effects of irradiation on innate and adaptive immunity.

Cell death-stimulated cell proliferation: a tissue regeneration mechanism usurped by tumors during radiotherapy

The death of all the cancer cells in a tumor is the ultimate goal of cancer therapy. Therefore, much of the current effort in cancer research is focused on activating cellular machinery that facilitates cell death such as factors involved in causing apoptosis. However, recently, a number of studies point to some counterintuitive roles for apoptotic caspases in radiation therapy as well as in tissue regeneration. It appears that a major function of apoptotic caspases is to facilitate tissue regeneration and tumor cell repopulation during cancer therapy. Because tumor cell repopulation has been shown to be important for local tumor relapse, understanding the molecular mechanisms behind tumor repopulation would be important to enhance cancer radiotherapy. In this review, we discuss our current knowledge of these potentially paradigm-changing phenomena and mechanisms in various organisms and their implications on the development of novel cancer therapeutics and strategies.

Radiation for Awakening the Dormant Immune System, a Promising Challenge to be Explored

Recent advances that have been made in our understanding of cancer biology and immunology show that infiltrated immune cells and cytokines in the tumor microenvironment may play different functions that appear tightly related to clinical outcomes. Strategies aimed at interfering with the cross-talk between microenvironment tumor cells and their cellular partners have been considered for the development of new immunotherapies. These novel therapies target different cell components of the tumor microenvironment and importantly, they may be coupled and boosted with classical treatments, such as radiotherapy. In this work, we try to summarize recent data on the microenvironment impact of radiation therapy, from pre-clinical research to the clinic, while taking into account that this new knowledge will probably translate into indication and objective of radiation therapy changes in the next future.

Radiation for Awakening the Dormant Immune System, a Promising Challenge to be Explored

Recent advances that have been made in our understanding of cancer biology and immunology show that infiltrated immune cells and cytokines in the tumor microenvironment may play different functions that appear tightly related to clinical outcomes. Strategies aimed at interfering with the cross-talk between microenvironment tumor cells and their cellular partners have been considered for the development of new immunotherapies. These novel therapies target different cell components of the tumor microenvironment and importantly, they may be coupled and boosted with classical treatments, such as radiotherapy. In this work, we try to summarize recent data on the microenvironment impact of radiation therapy, from pre-clinical research to the clinic, while taking into account that this new knowledge will probably translate into indication and objective of radiation therapy changes in the next future.

General overview of radioimmunotherapy of solid tumors

Radioimmunotherapy (RIT) represents an attractive tool for the treatment of local and/or diffuse tumors with radiation. In RIT, cytotoxic radionuclides are delivered by monoclonal antibodies that specifically target tumor-associated antigens or the tumor microenvironment. While RIT has been successfully employed for the treatment of lymphoma, mostly with radiolabeled antibodies against CD20 (Bexxar(®); Corixa Corp., WA, USA and Zevalin(®); Biogen Idec Inc., CA, USA and Schering AG, Berlin, Germany), its use in solid tumors is more challenging and, so far, few trials have progressed beyond Phase II. This review provides an update on antibody-radionuclide conjugates and their use in RIT. It also discusses possible optimization strategies to improve the clinical response by considering biological, radiobiological and physical features.

Clinical response of advanced cancer patients to cellular immunotherapy and intensity-modulated radiation therapy

Patients afflicted with advanced cancers were treated with the intratumoral injection of autologous immature dendritic cells (iDCs) followed by activated T-cell infusion and intensity-modulated radiation therapy (IMRT). A second round of iDCs and activated T cells was then administered to patients after the last radiation cycle. This complete regimen was repeated for new and recurring lesions after 6 weeks of follow-up. One year post therapy, outcome analyses were performed to evaluate treatment efficacy. Patients were grouped according to both the number and size of tumors and clinical parameters at treatment initiation, including recurrent disease after standard cancer therapy, Stage IV disease, and no prior therapy. Irrespective of prior treatment status, 23/37 patients with ≤ 5 neoplastic lesions that were ≤ 3 cm in diameter achieved complete responses (CRs), and 5/37 exhibited partial responses (PRs). Among 130 individuals harboring larger and more numerous lesions, CRs were observed in 7/74 patients that had received prior SCT and in 2/56 previously untreated patients. Some patients manifested immune responses including an increase in CD8⁺CD56⁺ lymphocytes among circulating mononuclear cells in the course of treatment. To prospectively explore the therapeutic use of these cells, CD8⁺ cells were isolated from patients that had been treated with cellular immunotherapy and IMRT, expanded in vitro, and injected into recurrent metastatic sites in 13 individuals who underwent the same immunoradiotherapeutic regimens but failed to respond. CRs were achieved in 34 of 58 of such recurrent lesions while PRs in 17 of 58. These data support the expanded use of immunoradiotherapy in advanced cancer patients exhibiting progressive disease.

Lung cancer: potential targets for immunotherapy

Lung cancer is the most common cause of cancer-related mortality worldwide and a therapeutic challenge. Recent success with antibodies blocking immune checkpoints in non-small-cell lung cancers (NSCLC) highlights the potential of immunotherapy for lung cancer treatment, and the need for trials of combination regimens of immunotherapy plus chemotherapy that lead to immunogenic cell death. Here, we review the development of immunogenic cytotoxic compounds, vaccines, and antibodies in NSCLC, in view of their integration into personalised oncology.

Therapy model for advanced intracerebral B16 mouse melanoma using radiation therapy combined with immunotherapy

A reproducible therapy model for advanced intracerebral B16 melanoma is reported. Implanted tumors (D0), suppressed by a single 15 Gy radiosurgical dose of 100 kVp X-rays (D8), were further suppressed by a single ip injection of a Treg-depleting mAb given 2 days prior to the initiation (D9) of four weekly then eight bi-monthly sc injections of GMCSF-transfected, mitotically disabled B16 cells. The trends of seven independent experiments were similar to the combined result: The median (days) [SD/total N] of survival went from 15[1.09/62] (no treatment control) to 35.8[8.8/58] (radiation therapy only) to 52.5[13.5/57] (radiation therapy plus immunotherapy). Within 2 weeks after immunization, tumors in mice receiving radiation therapy plus immunotherapy were significantly smaller than tumors in mice treated only with radiosurgery. Splenocytes and lymph node cells from immunized mice showed increased interferon γ production when cultured with syngeneic tumor cells. We suggest that our model will be useful for the development and testing of novel combination therapies for brain tumors.

IFN-γ mediates the antitumor effects of radiation therapy in a murine colon tumor

Cancer treatments using ionizing radiation (IR) therapy are thought to act primarily through the induction of tumor cell damage at a molecular level. However, a new concept has recently emerged, suggesting that the immune system is required for effective IR therapy. Our work here has identified interferon gamma (IFN-γ) as an essential cytokine for the efficacy of IR therapy. Local IR (15 Gy) to mice bearing Colon38, a colon adenocarcinoma, decreases tumor burden in wild-type animals. Interestingly, IR therapy had no effect on tumor burden in IFNγKO mice. We further determined that intratumoral levels of IFN-γ increased 2 days following IR, which directly correlated with a decrease in tumor burden that was not a result of direct cytotoxic effects of IFN-γ on tumor cells. T cells from IR-treated tumors exhibited a far greater capacity to lyse tumor cells in a (51)Cr release assay, a process that was dependent on IFN-γ. CD8(+) T cells were the predominant producers of IFN-γ, as demonstrated by IFN-γ intracellular staining and studies in IFN-γ reporter mice. Elimination of CD8(+) T cells by antibody treatment reduced the intratumoral levels of IFN-γ by over 90%. More importantly, elimination of CD8(+) T cells completely abrogated the effects of radiation therapy. Our data suggest that IFN-γ plays a pivotal role in mediating the antitumor effects of IR therapy.

Characterization of direct radiation-induced immune function and molecular signaling changes in an antigen presenting cell line

Radiation therapy is a widely used cancer treatment and pre-transplantation conditioning regimen that has the potential to influence anti-tumor and post-transplantation immune responses. Although conventionally fractionated radiation doses can suppress immune responses by depleting lymphocytes, single high doses of local tumor radiation can enhance immune responses. Using phospho-flow cytometry analysis of a human monocytic cell line, we identified novel radiation-induced changes in the phosphorylation state of NFκB family members known in other cell types to maintain and regulate immune function. These phosphorylation changes were p53 independent, but were strongly dependent upon ATM activation due to DNA damage. We found that radiation promotes the activation and APC functional maturation through phosphorylation of NFκB Essential Modulator (NEMO). Our results and the analytic methods are especially well suited to the study of functional changes in APC when radiation is used for immune modulation in clinical protocols.

The combination of ANT2 shRNA and hNIS radioiodine gene therapy increases CTL cytotoxic activity through the phenotypic modulation of cancer cells: combination treatment with ANT2 shRNA and I-131

BACKGROUND

It is important to simultaneously induce strong cell death and antitumor immunity in cancer patients for successful cancer treatment. Here, we investigated the cytotoxic and phenotypic modulation effects of the combination of ANT2 shRNA and human sodium iodide symporter (hNIS) radioiodine gene therapy in vitro and in vivo and visualized the antitumor effects in an immunocompromised mouse colon cancer model.

METHODS

A mouse colon cancer cell line co-expressing hNIS and the luciferase gene (CT26/hNIS-Fluc, named CT26/NF) was established. CT26/NF cells and tumor-bearing mice were treated with HBSS, scramble, ANT2 shRNA, I-131, and ANT2 shRNA + I-131. The apoptotic rates (%) and MHC class I and Fas gene expression levels were determined in treated CT26/NF cells using flow cytometry. Concurrently, the level of caspase-3 activation was determined in treated cells in vitro. For in vivo therapy, tumor-bearing mice were treated with scramble, ANT2 shRNA, I-131, and the combination therapy, and the anti-tumor effects were monitored using bioluminescence. The killing activity of cytotoxic T cells (CTLs) was measured with a lactate dehydrogenase (LDH) assay.

RESULTS

For the in vitro experiments, the combination of ANT2 shRNA and I-131 resulted in a higher apoptotic cell death rate compared with ANT2 shRNA or I-131 alone, and the levels of MHC class I and Fas-expressing cancer cells were highest in the cells receiving combination treatment, while single treatment modestly increased the level of MHC class I and Fas gene expression. The combination of ANT2 shRNA and I-131 resulted in a higher caspase-3 activation than single treatments. Interestingly, in vivo combination treatment led to increased gene expression of MHC class I and Fas than the respective mono-therapies; furthermore, bioluminescence showed increased antitumor effects after combination treatment than monotherapies. The LDH assay revealed that the CTL killing activity against CT26/NF cells was most effective after combination therapy.

CONCLUSIONS

Increased cell death and phenotypic modulation of cancer cells in vitro and in vivo were achieved simultaneously after combination therapy with ANT2 shRNA and I-131, and this combination therapy induced remarkable antitumor outcomes through improvements in CTL immunity against CT26/NF. Our results suggest that combination therapy can be used as a new therapeutic strategy for cancer patients who show resistance to single therapy such as radiation or immunotherapy.

Radiation-induced melanoma-associated leucoderma, systemic antimelanoma immunity and disease-free survival in a patient with advanced-stage melanoma: a case report and immunological analysis

BACKGROUND

Melanoma is an immunogenic tumour. The development of skin depigmentation or melanoma-associated leucoderma (MAL) has been associated with favourable clinical outcome in patients with metastatic melanoma, especially after immunotherapy. Evidence for clinically meaningful enhancement of melanoma-directed autoimmunity, as indicated by MAL, after radiotherapy without immunotherapy has not yet been published.

OBJECTIVES

We investigated whether a patient with stage IV melanoma, who developed leucoderma in the irradiated skin areas following radiotherapy and experienced exceptional disease-free survival of 3 years despite brain metastasis, possessed antimelanoma immunity that could be linked to the favourable disease course.

METHODS

A detailed immunological analysis was performed consisting of immunohistochemistry of several melanoma tissues, and analyses of T cells isolated from the blood and MAL skin tissue for melanocyte/melanoma specificity and functionality, as well as the presence of a melanoma-specific antibody response.

RESULTS

Immunological analyses showed the presence of CD8+ T cells and antibody responses directed against melanocyte differentiation antigens expressed in the primary tumour, lymph node and brain metastasis, indicating adequate tumour recognition by activated T cells.

CONCLUSION

The immune responses found in this patient, probably enhanced by radiotherapy, are thought to have contributed to his favourable clinical course. Radiotherapy may act as local immunotherapy in patients with melanoma by destroying melanocytes, leading to the induction, or enhancement, of already existent antimelanoma immunity. As in patients treated with immunotherapy, this may lead to MAL, also at distant sites from the treated area. This patient is a clear example of the positive prognostic value of MAL, which is possibly induced by radiotherapy, for patients with melanoma.

Chapter seven--Cancer treatment with gene therapy and radiation therapy

Radiation therapy methods have evolved remarkably in recent years which have resulted in more effective local tumor control with negligible toxicity of surrounding normal tissues. However, local recurrence and distant metastasis often occur following radiation therapy mostly due to the development of radioresistance through the deregulation of the cell cycle, apoptosis, and inhibition of DNA damage repair mechanisms. Over the last decade, extensive progress in radiotherapy and gene therapy combinatorial approaches has been achieved to overcome resistance of tumor cells to radiation. In this review, we summarize the results from experimental cancer therapy studies on the combination of radiation therapy and gene therapy.

Combining radiotherapy and cancer immunotherapy: a paradigm shift

The therapeutic application of ionizing radiation has been largely based on its cytocidal power combined with the ability to selectively target tumors. Radiotherapy effects on survival of cancer patients are generally interpreted as the consequence of improved local control of the tumor, directly decreasing systemic spread. Experimental data from multiple cancer models have provided sufficient evidence to propose a paradigm shift, whereby some of the effects of ionizing radiation are recognized as contributing to systemic antitumor immunity. Recent examples of objective responses achieved by adding radiotherapy to immunotherapy in metastatic cancer patients support this view. Therefore, the traditional palliative role of radiotherapy in metastatic disease is evolving into that of a powerful adjuvant for immunotherapy. This combination strategy adds to the current anticancer arsenal and offers opportunities to harness the immune system to extend survival, even among metastatic and heavily pretreated cancer patients. We briefly summarize key evidence supporting the role of radiotherapy as an immune adjuvant. A critical appraisal of the current status of knowledge must include potential immunosuppressive effects of radiation that can hamper its capacity to convert the irradiated tumor into an in situ, individualized vaccine. Moreover, we discuss some of the current challenges to translate this knowledge to the clinic as more trials testing radiation with different immunotherapies are proposed.