Reprogramming the immunosuppressive tumor microenvironment results in successful clearance of tumors resistant to radiation therapy and anti-PD-1/PD-L1

Despite breakthroughs in immune checkpoint inhibitors (ICI), the majority of tumors, including those poorly infiltrated by CD8+ T cells or heavily infiltrated by immunosuppressive immune effector cells, are unlikely to result in clinically meaningful tumor responses. Radiation therapy (RT) has been combined with ICI to potentially overcome this resistance and improve response rates but reported clinical trial results have thus far been disappointing. Novel approaches are required to overcome this resistance and reprogram the immunosuppressive tumor microenvironment (TME) and address this major unmet clinical need. Using diverse preclinical tumor models of prostate and bladder cancer, including an autochthonous prostate tumor (Pten-/-/trp53-/-) that respond poorly to radiation therapy (RT) and anti-PD-L1 combinations, the key drivers of this resistance within the TME were profiled and used to develop rationalized combination therapies that simultaneously enhance activation of anti-cancer T cell responses and reprogram the immunosuppressive TME. The addition of anti-CD40mAb to RT resulted in an increase in IFN-y signaling, activation of Th-1 pathways with an increased infiltration of CD8+ T-cells and regulatory T-cells with associated activation of the CTLA-4 signaling pathway in the TME. Anti-CTLA-4mAb in combination with RT further reprogrammed the immunosuppressive TME, resulting in durable, long-term tumor control. Our data provide novel insights into the underlying mechanisms of the immunosuppressive TME that result in resistance to RT and anti-PD-1 inhibitors and inform therapeutic approaches to reprogramming the immune contexture in the TME to potentially improve tumor responses and clinical outcomes.

Progress and pitfalls with the use of image-guided personalised approaches in lymphoma

The use of ¹⁸F-FDG PET CT has become an essential part of the management of patients with lymphoma. The last decade has seen unrivalled progress in research efforts to personalise treatment approaches using PET as a predictive imaging biomarker. Critical to this success has been the standardisation of PET methods and reporting, including the 5-point Deauville scale, which has enabled the delivery of robust clinical trial data to develop response-adapted treatment approaches.(1, 2) The utility of PET as a predictive imaging biomarker in assessing treatment success or failure has been investigated extensively in malignant lymphomas. Considerable progress has been made over the last decade, in using PET to direct more personalised "risk-adapted" approaches, as well as an increased understanding of some of the limitations. Arguably the greatest success has been in Hodgkin Lymphoma (HL) where PET was initially demonstrated to be a powerful predictive biomarker (3) and is now routinely used in both early-stage and advanced HL to reduce or escalate the use of chemotherapy as well as guiding the delivery of more selective radiotherapy to patients.

Reprogramming the tumour microenvironment by radiotherapy: implications for radiotherapy and immunotherapy combinations

Radiotherapy (RT) is a highly effective anti-cancer therapy delivered to around 50-60% of patients. It is part of therapy for around 40% of cancer patients who are cured of their disease. Until recently, the focus of this anti-tumour efficacy has been on the direct tumour cytotoxicity and RT-induced DNA damage. Recently, the immunomodulatory effects of RT on the tumour microenvironment have increasingly been recognized. There is now intense interest in potentially using RT to induce an anti-tumour immune response, which has led to rethinking into how the efficacy of RT could be further enhanced. Following the breakthrough of immune check point inhibitors (ICIs), a new era of immuno-oncology (IO) agents has emerged and established immunotherapy as a routine part of cancer treatment. Despite ICI improving outcomes in many cancer types, overall durable responses occur in only a minority of patients. The immunostimulatory effects of RT make combinations with ICI attractive to potentially amplify anti-tumour immunity resulting in increased tumour responses and improved outcomes. In contrast, tumours with profoundly immunosuppressive tumour microenvironments, dominated by myeloid-derived cell populations, remain a greater clinical challenge and RT may potentially further enhance the immunosuppression. To harness the full potential of RT and IO agent combinations, further insights are required to enhance our understanding of the role these immunosuppressive myeloid populations play, how RT influences these populations and how they may be therapeutically manipulated in combination with RT to improve outcomes further. These are exciting times with increasing numbers of IO targets being discovered and IO agents undergoing clinical evaluation. Multidisciplinary research collaborations will be required to establish the optimal parameters for delivering RT (target volume, dose and fractionation) in combination with IO agents, including scheduling to achieve maximal therapeutic efficacy.

Novel Methods to Improve the Efficiency of Radioimmunotherapy for Non-Hodgkin Lymphoma

Radioimmunotherapy (RIT) is a novel strategy for treating non-Hodgkin lymphoma (NHL). Several studies have shown the promising results of using RIT in NHL, which have led to FDA approval for two RIT agents in treating low grade NHL. In spite of these favorable results in low-grade NHL, most of the aggressive or relapsed/refractory NHL subjects experience relapses following RIT. Although more aggressive treatments such as myeloablative doses of RIT followed by stem cell transplantation appear to be able to provide a longer survival for some patients these approaches are associated with significant treatment-related adverse events and challenging to deliver in most centers. Therefore, it seems reasonable to develop treatment approaches that enhance the efficiency of RIT, while reducing its toxicity. In this paper, novel methods that improve the efficiency of RIT and reduce its toxicity through various mechanisms are reviewed. Further clinical development of these methods could expand the NHL patient groups eligible for receiving RIT, and even extend the use of RIT to new indications and disease groups in future.

Akt inhibition improves long-term tumour control following radiotherapy by altering the microenvironment

Radiotherapy is an important anti-cancer treatment, but tumour recurrence remains a significant clinical problem. In an effort to improve outcomes further, targeted anti-cancer drugs are being tested in combination with radiotherapy. Here, we have studied the effects of Akt inhibition with AZD5363. AZD5363 administered as an adjuvant after radiotherapy to FaDu and PE/CA PJ34 tumours leads to long-term tumour control, which appears to be secondary to effects on the irradiated tumour microenvironment. AZD5363 reduces the downstream effectors VEGF and HIF-1α, but has no effect on tumour vascularity or oxygenation, or on tumour control, when administered prior to radiotherapy. In contrast, AZD5363 given after radiotherapy is associated with marked reductions in tumour vascular density, a decrease in the influx of CD11b+ myeloid cells and a failure of tumour regrowth. In addition, AZD5363 is shown to inhibit the proportion of proliferating tumour vascular endothelial cells in vivo, which may contribute to improved tumour control with adjuvant treatment. These new insights provide promise to improve outcomes with the addition of AZD5363 as an adjuvant therapy following radiotherapy.

A TLR7 agonist enhances the antitumor efficacy of obinutuzumab in murine lymphoma models via NK cells and CD4 T cells

This corrects the article DOI: 10.1038/leu.2016.352.

A TLR7 agonist enhances the antitumor efficacy of obinutuzumab in murine lymphoma models via NK cells and CD4 T cells

Anti-CD20 monoclonal antibodies (mAb) such as rituximab have been proven to be highly effective at improving outcome in B-cell malignancies. However, many patients ultimately relapse and become refractory to treatment. The glycoengineered anti-CD20 mAb obinutuzumab was developed to induce enhanced antibody-dependent cellular cytotoxicity, antibody-dependent phagocytosis and direct cell death and was shown to lead to improved outcomes in a randomized study in B-CLL. We hypothesized that immune stimulation through Toll-like receptor 7 (TLR7) agonism in combination with obinutuzumab would further enhance lymphoma clearance and the generation of long-term antitumor immune responses. Here we demonstrate, in syngeneic human CD20 (hCD20)-expressing models of lymphoma, that systemic administration of a TLR7 agonist (R848) increases responses when administered in combination with obinutuzumab and protects against disease recurrence. Depletion studies demonstrate that primary antitumor activity is dependent on both NK cells and CD4+ T cells but not on CD8+ T cells. However, both CD4+ and CD8+ T cells appear necessary for the generation of protective immunological memory. Importantly, increased tumor-free survival post obinutuzumab and R848 combination therapy was seen in hCD20 transgenic mice, which express hCD20 on normal B cells. These findings provide a rationale for clinical testing of obinutuzumab in combination with systemically administered TLR7 agonists to further improve outcome.

Stereotactic ablative radiotherapy and immunotherapy combinations: turning the future into systemic therapy?

Radiotherapy (RT) is effective at cytoreducing tumours and until relatively recently the focus in radiobiology has been on the direct effects of RT on the tumour. Increasingly, however, the effect of RT on the tumour vasculature, tumour stroma and immune system are recognized as important to the overall outcome. RT is known to lead to the induction of immunogenic cell death (ICD), which can generate tumour-specific immunity. However, systemic immunity leading to "abscopal effects" resulting in tumour shrinkage outside of the RT treatment field is rare, which is thought to be caused by the immunosuppressive nature of the tumour microenvironment. Recent advances in understanding the nature of this immunosuppression and therapeutics targeting immune checkpoints such as programmed death 1 has led to durable clinical responses in a range of cancer types including malignant melanoma and non-small-cell lung cancer. The effects of RT dose and fraction on the generation of ICD and systemic immunity are largely unknown and are currently under investigation. Stereotactic ablative radiotherapy (SABR) provides an opportunity to deliver single or hypofractionated large doses of RT and potentially increase the amount of ICD and the generation of systemic immunity. Here, we review the interplay of RT and the tumour microenvironment and the rationale for combining SABR with immunomodulatory agents to generate systemic immunity and improve outcomes.

Abstract SY31-02: The interplay of radiotherapy with the tumour microenvironment: Novel opportunities to overcome adaptive resistance

Radiation Therapy (RT) is a highly effective anti-cancer treatment delivered to approximately 50 - 60% of all cancer patients, In addition to the direct tumor cell kill, emerging evidence suggests that RT has important effects on the tumor microenvironment and can generate anti-tumor immunity. RT induced tumor cell death is known to lead to increased ecto-calreticulin and tumor antigen expression as well as the release of several damage-associated molecular patterns (DAMPs). These “danger signals” include High Mobility Group Box 1 (HMGB1) and ATP which can lead to recruitment and activation of antigen presenting cells (APCs) and priming of tumor antigen-specific T cell responses. Despite these immunomodulatory properties of RT, systemic anti-tumor immune responses leading to clinically meaningful anti-tumor responses outside of the irradiated tumor field the so called the “abscopal effect” are rare in routine clinical practice. This lack of clinically meaningful abscopal effect is thought to be secondary to the immunosuppressive nature of the tumor microenvironment (TME), including Myeloid Derived Suppressor Cells (MDSC), Foxp3 T regulatory cells (Tregs) or blocking inhibitory molecules such as Programmed cell death protein 1 (PD-1), Cytotoxic T-lymphocyte-associated protein 4 (CTLA-4); (LAG-3) Lymphocyte-activation gene 3, T-cell immunoglobulin and mucin-domain containing-3 (Tim-3),receptors or inhibitory cytokines including Transforming Growth Factor (TGF-β) and IL-13. Therefore therapeutic strategies designed to overcome these inhibitory immunosuppressive networks may provide an opportunity to enhance anti-tumor immunity by promoting the generation of T cell priming in combination with RT.

Emerging biological insights and target identification of some of the important immune checkpoints that control regulation of anti-tumor immunity have led to the development of an increasing number of novel immunomodulatory agents. These new therapeutics can be broadly divided into either agonists or immune stimulating receptors (co-stimulatory receptors) eg CD40, OX40,CD137 /4-1BB or antagonists of immune suppressor molecules (co-inhibitory molecules) eg CTLA4, PD-1,PD-L1, LAG-3,Tim-3 that are able to overcome the down regulation of anti-tumor immunity. Most recent clinical progress has been with immune “check-point inhibitors”. Proof of principle was initially demonstrated with anti- CTLA-4 monoclonal antibodies (mAb) and more recently with anti-PD-1 and anti-PDL1 checkpoint inhibitors leading to durable anti-tumor immune responses in a broad range of cancers including melanoma, renal cell and non-small-cell lung cancer. Although encouraging, clinical responses were observed, this was only in the minority of patients and it is likely that combination therapy approaches will be required to improve response rates to increase response rates for the majority. Combinations of RT and immunomodulatory agents are attractive, given the local anti-tumor efficacy of RT and lack of systemic immunosuppression that is commonly seen with cytotoxic chemotherapy and other systemic agents. The biological premise is that RT initiates local tumour “immunogenic cell death” leading to local immune response that will be augmented by immunomodulatory agents leading to systemic anti-tumor immunity and greater tumor control. Preclinical studies have demonstrated that the anti-tumor immune responses generated by RT can be enhanced through combination with a range of immunomodulatory agents such as immune agonists such as anti-CD40, Toll Like Receptors (TLR), and immune checkpoints inhibitors such anti-CTLA-4, anti-PD1. Understanding the effect of RT on the local TME and using immunomodulatory agents to overcome the immunosuppression within the TME, are key to making further progress. Recent data has demonstrated that fractionated RT leads to local T-cell activation and production of IFNγ which drives adaptive resistance through the PD-1/PD-L1 axis. RT leads to increases in PD-L1 expression on both tumor cells and MDSC within the irradiated tumor. Concurrent treatment with RT and anti-PD-1 mAb overcomes this local immunosuppression facilitating systemic anti-tumor immunity capable of mediating the systemic tumor regression. Dual immune checkpoint inhibitor combinations with RT are likely to be important in more durable remissions. In a melanoma model the optimal anti-tumor response required RT, anti-CTLA-4 and anti-PD-L1/PD-1. Anti-CTLA-4 was found to predominantly inhibits T-regulatory cells (Treg cells), thereby increasing the CD8 T-cell to Treg (CD8/Treg) ratio. RT was found to enhance the diversity of the T-cell receptor (TCR) repertoire of intra-tumoral T cells. Together, anti-CTLA-4 was found to promote the expansion of T cells, while RT appeared to increase and define the TCR repertoire of the expanded peripheral clones. The addition of PD-L1 blockade appeared to reverse the T-cell exhaustion to mitigate depression in the CD8/Treg ratio and further encourages oligoclonal T-cell expansion, with the triple combination leading to increased durable anti-tumor responses.

The translation of immunomodulation from scientific discovery to effective clinical anti-cancer therapeutics has been considerable over the past decade. RT and immunmodulatory combinations offer great potential to improve outcomes further if the appropriate translational research and well-designed clinical trials are performed. In order to increase the number of responses in the majority of patients across many tumor types further investigation is required to fully understand the potential underlying mechanisms of resistance is required.

In the palliative setting in metastatic disease RT can be used an “immunogenic hub” with local tumor cell death enhancing systemic immune responses with immunomodulatory agents. Further research is required to inform clinical translation including the optimal radiation dose and fraction size, which is likely to be tumor specific, and most importantly the optimal scheduling of RT and immunotherapy. The future however appears extremely promising to potentially convert RT from a local treatment to a highly effective systemic therapy when used in combination with immunomodulatory agents

Citation Format: Tim M. Illidge. The interplay of radiotherapy with the tumour microenvironment: Novel opportunities to overcome adaptive resistance. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr SY31-02.

Short duration immunochemotherapy followed by radioimmunotherapy consolidation is effective and well tolerated in relapsed follicular lymphoma: 5-year results from a UK National Cancer Research Institute Lymphoma Group study

We report a phase II study to evaluate the efficacy and toxicity of abbreviated immunochemotherapy followed by (90) Y Ibritumomab tiuxetan ((90) Y-IT) in patients with recurrent follicular lymphoma. Of the 52 patients enrolled, 50 were treated with three cycles of R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, prednisolone) or R-CVP (rituximab, cyclophosphamide, vincristine, prednisolone), followed by (90) Y-IT regimen (15 MBq/kg, maximum 1200 MBq) preceded by two infusions of 250 mg/m(2) rituximab. The overall response rate was 98% with complete response (CR) 30% and partial response (PR) 68%. 18 patients with a PR following chemotherapy improved to a CR following (90) Y-IT: a conversion rate of 40%. Seven patients with PR following (90) Y-IT subsequently improved to a CR 12-18 months later, leading to an overall CR rate of 44%. With a median follow-up of 5 years, median progression-free survival was 23·1 months and overall survival was 77·5% at 5 years. High trough serum rituximab levels (median 112 μg/ml; range 52-241) were attained after four doses of rituximab, prior to (90) Y-IT; this was not found to influence response rates. The treatment was well tolerated with few (13·5%) grade 3 or 4 infective episodes and manageable haematological toxicity. Abbreviated immunochemotherapy followed by (90) Y-IT is an effective and well-tolerated treatment in recurrent follicular lymphoma patients previously exposed to rituximab.

TRIAL REGISTRATION

clinicaltrials.gov identifier: NCT00637832.

The antitumor immune response generated by fractionated radiation therapy may be limited by tumor cell adaptive resistance and can be circumvented by PD-L1 blockade

Fractionated radiation therapy (RT) leads to adaptive changes in the tumor microenvironment that may limit the generation of an antitumor immune response. We demonstrated that fractionated RT led to increased tumor cell expression of programmed cell death ligand 1 (PD-L1) in response to CD8⁺ T cell production of interferon gamma. Our data reveal that the efficacy of fractionated RT can be significantly improved through the generation of durable systemic immune responses when combined with concurrent, but not sequential, blockade of the PD-1/PD-L1 pathway.

Acquired resistance to fractionated radiotherapy can be overcome by concurrent PD-L1 blockade

Radiotherapy is a major part in the treatment of most common cancers, but many patients experience local recurrence with metastatic disease. In evaluating response biomarkers, we found that low doses of fractionated radiotherapy led to PD-L1 upregulation on tumor cells in a variety of syngeneic mouse models of cancer. Notably, fractionated radiotherapy delivered in combination with αPD-1 or αPD-L1 mAbs generated efficacious CD8(+) T-cell responses that improved local tumor control, long-term survival, and protection against tumor rechallenge. These favorable outcomes were associated with induction of a tumor antigen-specific memory immune response. Mechanistic investigations showed that IFNγ produced by CD8(+) T cells was responsible for mediating PD-L1 upregulation on tumor cells after delivery of fractionated radiotherapy. Scheduling of anti-PD-L1 mAb was important for therapeutic outcome, with concomitant but not sequential administration with fractionated radiotherapy required to improve survival. Taken together, our results reveal the mechanistic basis for an adaptive response by tumor cells that mediates resistance to fractionated radiotherapy and its treatment failure. With attention to scheduling, combination immunoradiotherapy with radiotherapy and PD-1/PD-L1 signaling blockade may offer an immediate strategy for clinical evaluation to improve treatment outcomes.

Consensus guidelines for the detection of immunogenic cell death

Apoptotic cells have long been considered as intrinsically tolerogenic or unable to elicit immune responses specific for dead cell-associated antigens. However, multiple stimuli can trigger a functionally peculiar type of apoptotic demise that does not go unnoticed by the adaptive arm of the immune system, which we named "immunogenic cell death" (ICD). ICD is preceded or accompanied by the emission of a series of immunostimulatory damage-associated molecular patterns (DAMPs) in a precise spatiotemporal configuration. Several anticancer agents that have been successfully employed in the clinic for decades, including various chemotherapeutics and radiotherapy, can elicit ICD. Moreover, defects in the components that underlie the capacity of the immune system to perceive cell death as immunogenic negatively influence disease outcome among cancer patients treated with ICD inducers. Thus, ICD has profound clinical and therapeutic implications. Unfortunately, the gold-standard approach to detect ICD relies on vaccination experiments involving immunocompetent murine models and syngeneic cancer cells, an approach that is incompatible with large screening campaigns. Here, we outline strategies conceived to detect surrogate markers of ICD in vitro and to screen large chemical libraries for putative ICD inducers, based on a high-content, high-throughput platform that we recently developed. Such a platform allows for the detection of multiple DAMPs, like cell surface-exposed calreticulin, extracellular ATP and high mobility group box 1 (HMGB1), and/or the processes that underlie their emission, such as endoplasmic reticulum stress, autophagy and necrotic plasma membrane permeabilization. We surmise that this technology will facilitate the development of next-generation anticancer regimens, which kill malignant cells and simultaneously convert them into a cancer-specific therapeutic vaccine.

Final results of a multicenter phase II study of the purine nucleoside phosphorylase (PNP) inhibitor forodesine in patients with advanced cutaneous T-cell lymphomas (CTCL) (Mycosis fungoides and Sézary syndrome)

BACKGROUND

Forodesine is a potent inhibitor of purine nucleoside phosphorylase (PNP) that leads to intracellular accumulation of deoxyguanosine triphosphate (dGTP) in T and B cells, resulting in apoptosis. Forodesine has demonstrated impressive antitumor activity in early phase clinical trials in cutaneous T-cell lymphoma (CTCL).

PATIENTS AND METHODS

In this phase II study, patients with CTCL who had already failed three or more systemic therapies were recruited. We investigated the response rate, safety and tolerability of oral forodesine treatment in subjects with cutaneous manifestations of CTCL, stages IB, IIA, IIB, III and IVA. The safety population encompassing all stages was used for analysis of accountability, demographics and safety. The efficacy population differed from the safety population by exclusion of stage IB and IIA patients.

RESULTS

All 144 patients had performance status 0-2. The median duration of CTCL from diagnosis was 53 months (5-516 months). The median number of pretreatments was 4 (range: 3-15). No complete remissions were observed. In the efficacy group of patients, 11% achieved partial remission and 50% had stable disease. The median time to response was 56 days and the median duration of response was 191 days. A total of 96% of all treated patients reported one or more adverse events (AEs) and 33% reported a serious AE. The majority of AEs were classified as mild or moderate in severity. The most commonly reported AEs (>10%) were peripheral edema, fatigue, insomnia, pruritus, diarrhea, headache and nausea. Overall eight patients died during the study: five due to sepsis and infections, one due to a second malignancy (esophageal cancer), one due to disease progression and one due to liver failure.

CONCLUSION

Oral forodesine at a dose of 200 mg daily is feasible and shows partial efficacy in this highly selected CTCL population and some durable responses.

Emerging opportunities for the combination of molecularly targeted drugs with radiotherapy

Recent drug discovery developments in the field of small molecule targeted agents have led to much interest in combining these with radiotherapy. There are good preclinical data to suggest this approach worthy of investigation and in this review we discuss how this has translated into recent clinical trials. The outcome of clinical trials investigating radiotherapy/targeted drug combinations published in the last 5 years is discussed, as are trials in progress. The perceived future opportunities and challenges in the development of this exciting area are considered.

Fractionated 90Y-Ibritumomab Tiuxetan Radioimmunotherapy As an Initial Therapy of Follicular Lymphoma: An International Phase II Study in Patients Requiring Treatment According to GELF/BNLI Criteria

Purpose

We report an international, multicenter phase II trial to evaluate the efficacy and toxicity of fractionated 90Y-ibritumomab tiuxetan (90Y-IT) as initial therapy of follicular lymphoma (FL).

Patients and Methods

A total of 74 patients, with a median age of 61 years (range, 28 to 80 years), were recruited requiring initial therapy by Groupe d'Etude des Lymphomes Folliculaires (GELF)/British National Lymphoma Investigation (BNLI) criteria. Among them, 78% had stage III-IV disease, 32% intermediate, and 44% high-risk (according to FL International Prognostic Index). Treatment consisted of two doses of 90Y-IT (11.1 MBq/kg) administered 8 to 12 weeks apart. Patients with more than 20% lymphoma infiltration of bone marrow (BM) received one infusion per week for 4 consecutive weeks of rituximab (375 mg/m2) and proceeded to fractionated radioimmunotherapy (RIT) only if a repeat BM biopsy demonstrated clearing of lymphoma to less than 20% involvement. The primary end point was end of treatment response of the intention-to-treat population. Secondary objectives were safety and progression-free survival (PFS).

Results

Initial overall response rate (ORR) was 94.4% (68 of 72 patients) with combined complete response (CR/CRu) of 58.3% (42 of 72 patients). Nine patients subsequently improved response making an ORR of 95.8% (69 of 72 patients) and CR/CRu of 69.4% (50 of 72 patients). At a median follow-up of 3.1 years (range, 0.2 to 5.2 years) estimated 3-year PFS is 58%, treatment-free survival 66%, and overall survival 95%. Median PFS is 40.2 months. Thirty patients have experienced disease progression and 24 have required further treatment. The treatment was well tolerated with few (2.8%) grade 3 or 4 infectious episodes or adverse events and manageable hematologic toxicity.

Conclusion

Fractionated RIT using 90Y-IT is an effective initial treatment for advanced-stage FL in patients with higher tumor burden requiring treatment.

Radiotherapy physics research in the UK: challenges and proposed solutions

In 2011, the Clinical and Translational Radiotherapy Research Working Group (CTRad) of the National Cancer Research Institute brought together UK radiotherapy physics leaders for a think tank meeting. Following a format that CTRad had previously and successfully used with clinical oncologists, 23 departments were asked to complete a pre-meeting evaluation of their radiotherapy physics research infrastructure and the strengths, weaknesses, opportunities and threats within their own centre. These departments were brought together with the CTRad Executive Group and research funders to discuss the current state of radiotherapy physics research, perceived barriers and possible solutions. In this Commentary, we summarise the submitted materials, presentations and discussions from the meeting and propose an action plan. It is clear that there are challenges in both funding and staffing of radiotherapy physics research. Programme and project funding streams sometimes struggle to cater for physics-led work, and increased representation on research funding bodies would be valuable. Career paths for academic radiotherapy physicists need to be examined and an academic training route identified within Modernising Scientific Careers; the introduction of formal job plans may allow greater protection of research time, and should be considered. Improved access to research facilities, including research linear accelerators, would enhance research activity and pass on developments to patients more quickly; research infrastructure could be benchmarked against centres in the UK and abroad. UK National Health Service departments wishing to undertake radiotherapy research, with its attendant added value for patients, need to develop a strategy with their partner higher education institution, and collaboration between departments may provide enhanced opportunities for funded research.

New antibody drug treatments for lymphoma

INTRODUCTION

The advent of anti-CD20 monoclonal antibody (mAb) rituximab heralded a new era in the treatment of non-Hodgkin's lymphoma leading to significant improvements in outcome for patients. This unprecedented success has changed the mindset of the clinical community and catalyzed the interest in the pharmaceutical industry to develop the next-generation of antibodies and antibody conjugates in cancer.

AREAS COVERED

There are an ever increasing number of newer generation anti-CD20 and rituximab 'bio-similars' undergoing early phase clinical development. In addition emerging novel therapies including antibody drug conjugates (brentuximab vedotin, SGN-35) and mAb against T-cell lymphomas antigens (e.g., zanolimumab) offer hope of improved outcome for other lymphomas. Bispecific T-cell-engaging antibodies and combination immunotherapy, also provide the promise of further improvements. Radiolabelled antibodies or radioimmunotherapy (RIT) has also demonstrated high clinical activity and two drugs namely 131I-tositumomab (Bexxar) and 90Y-ibritumomab (Zevalin) are licensed.

EXPERT OPINION

Despite the large numbers of new anti-CD20 mAb currently undergoing clinical testing, improving on clinical efficacy of rituximab is a substantial challenge. Further improvements in outcome for patients will require rigorous testing in well designed clinical trials alongside the translation of new insights into mechanism of mAb action that lead to improvements in clinical efficacy.

Validation of an ELISA for the determination of rituximab pharmacokinetics in clinical trials subjects

Rituximab is a chimeric anti-CD20 monoclonal antibody that has revolutionised the treatment of many B-cell malignancies, and is now increasingly being used in non-malignant conditions such as auto-immune disorders. Serum rituximab levels are highly variable in patients receiving similar 'standard' approved doses. Little is known regarding the factors that affect serum rituximab concentration and that in turn may influence clinical outcome. In order to provide a tool that may ultimately enable patient specific dosing of rituximab therapy, we have validated a reliable, robust ELISA for the quantitation of serum rituximab levels to provide accurate pharmacokinetic (PK) data that will guide the optimisation of rituximab dosing regimes. Extensive validation of the assay was performed in order to utilise the assay for clinical applications. The within and between day plate coating reproducibility was tested and proved a robust starting platform for the assay. The within day precision for the assay was determined using spiked serum samples and was shown to have a coefficient of variation (CV) of <10% with an accuracy between 91 and 125%. The between day precision (CV) was <25% with an accuracy between 95 and 109%. Dilution linearity and parallelism were demonstrated. Spike recovery for all concentrations and donors was shown to be within +/-15% on average, with a CV below 10%. This assay is highly accurate and reproducible in determining the levels of rituximab in spiked serum samples. It meets stringent acceptance criteria, is fit for purpose, and is currently being applied to several clinical trials incorporating rituximab in the treatment of lymphoma. This assay represents a useful tool for clinical application of this widely used therapeutic.

Radioimmunotherapy: strategies for the future in indolent and aggressive lymphoma

The conjugation of radioisotopes to monoclonal antibodies, or radioimmunotherapy (RIT), is a highly active treatment in non-Hodgkin's lymphoma. RIT has demonstrated high response rates and durable remissions in extensively pretreated patients and has proved highly effective as consolidation after induction chemotherapy in the first-line therapy of follicular lymphoma. Early-phase clinical trials have shown highly promising results using RIT as part of conditioning regimens in patients who are to undergo transplantation and as consolidation after chemotherapy in patients with aggressive lymphomas. Recent data suggest that integrating RIT with immunochemotherapy and transplant conditioning regimens may further improve outcomes for patients.

Monoclonal antibodies directed to CD20 and HLA-DR can elicit homotypic adhesion followed by lysosome-mediated cell death in human lymphoma and leukemia cells

mAbs are becoming increasingly utilized in the treatment of lymphoid disorders. Although Fc-FcgammaR interactions are thought to account for much of their therapeutic effect, this does not explain why certain mAb specificities are more potent than others. An additional effector mechanism underlying the action of some mAbs is the direct induction of cell death. Previously, we demonstrated that certain CD20-specific mAbs (which we termed type II mAbs) evoke a nonapoptotic mode of cell death that appears to be linked with the induction of homotypic adhesion. Here, we reveal that peripheral relocalization of actin is critical for the adhesion and cell death induced by both the type II CD20-specific mAb tositumomab and an HLA-DR-specific mAb in both human lymphoma cell lines and primary chronic lymphocytic leukemia cells. The cell death elicited was rapid, nonapoptotic, nonautophagic, and dependent on the integrity of plasma membrane cholesterol and activation of the V-type ATPase. This cytoplasmic cell death involved lysosomes, which swelled and then dispersed their contents, including cathepsin B, into the cytoplasm and surrounding environment. The resulting loss of plasma membrane integrity occurred independently of caspases and was not controlled by Bcl-2. These experiments provide what we believe to be new insights into the mechanisms by which 2 clinically relevant mAbs elicit cell death and show that this homotypic adhesion-related cell death occurs through a lysosome-dependent pathway.

Fusion of metabolic function and morphology: sequential [18F]fluorodeoxyglucose positron-emission tomography/computed tomography studies yield new insights into the natural history of bone metastases in breast cancer

PURPOSE

By monitoring bone metastases with sequential [(18)F]fluorodeoxyglucose positron-emission tomography/computed tomography ([(18)F]FDG-PET/CT) imaging, this study investigates the clinical relevance of [(18)F]FDG uptake features of bone metastases with various radiographic appearances.

PATIENTS AND METHODS

Bone metastases were found in 67 of 408 consecutive patients with known/suspected recurrent breast cancer on [(18)F]FDG-PET/CT, characterized by CT morphology changes and/or bony [(18)F]FDG uptake. Twenty-five of the patients had sequential [(18)F]FDG-PET/CT examinations (86 studies) over an average follow-up period of 23 months. The temporal changes in [(18)F]FDG uptake and corresponding CT morphology features of 146 bone lesions identified in these 25 patients were followed up and correlated with therapeutic outcome retrospectively.

RESULTS

The 146 lesions were classified as osteolytic (77), osteoblastic (41), mixed-pattern (11), or no change/negative (17) on CT. The majority of the osteolytic (72; 93.5%) and mixed-pattern lesions (nine; 81.8%), but fewer of the osteoblastic lesions (25; 61%), showed increased [(18)F]FDG uptake. After treatment, 58 osteolytic lesions (80.5%) became [(18)F]FDG negative and osteoblastic on CT and only 14 relatively large lesions (19.5%) remained [(18)F]FDG avid. Of the 25 [(18)F]FDG-avid osteoblastic lesions, 13 (52%) became [(18)F]FDG negative, but 12 (48%) remained [(18)F]FDG avid and increased in size on CT. Five of the mixed-pattern lesions remained [(18)F]FDG avid after treatment. All 17 CT-negative lesions became [(18)F]FDG negative; however, nine of them became osteoblastic. None of the initially [(18)F]FDG-negative lesions showed [(18)F]FDG avidity during follow-up.

CONCLUSION

[(18)F]FDG uptake reflects the immediate tumor activity of bone metastases, whereas the radiographic morphology changes vary greatly with time among patients.

Segregation of genomes in polyploid tumour cells following mitotic catastrophe

Following irradiation p53-function-deficient tumour cells undergo mitotic catastrophe and form endopolyploid cells. A small proportion of these segregates nuclei, and give rise to viable descendants. Here we studied this process in five tumour cell lines. After mitotic failure, tumour cells enter the endocycle and form mono-nucleated or multi-nucleated giant cells (MOGC and MNGC). MNGC arise from arrested anaphases, MOGC, from arrested metaphases. In both cases the individual genomes establish a radial pattern by links to a single microtubule organizing centre. Segregation of genomes is also ordered. MNGC present features of mitosis being resumed from late anaphase. In MOGC the sub-nuclei retain arrangement of stacked metaphase plates and are separated by folds of the nuclear envelope. Mitosis then resumes in sub-nuclei directly from metaphase. The data presented indicate that endopolyploid tumour cells preserve the integrity of individual genomes and can potentially re-initiate mitosis from the point at which it was interrupted.

What's new in the management of cutaneous T-cell lymphoma?

The aetiology and clinical management of primary cutaneous T-cell lymphoma (CTCL) and specifically of mycosis fungoides and Sezary syndrome are poorly defined. Interesting new insights into CTCL disease biology as well as a number of emerging of novel therapeutic interventions make this an increasingly interesting area for dermatologists and oncologists involved in the treatment of CTCL. This review article covers much of this new information including new drugs, such as denileukin diftitox (Ontak) a targeted cytotoxic biological agent, Bexarotene an RXR selective retinoid, anti-CD4 monoclonal antibodies (mAb), new cytotoxics agents and vaccines.

Antibody-induced intracellular signaling works in combination with radiation to eradicate lymphoma in radioimmunotherapy

Radioimmunotherapy (RIT) has emerged as an effective treatment for lymphoma, however the underlying mechanisms are poorly understood. We therefore investigated the relative contributions of antibody and targeted radiation to the clearance of tumor in vivo, using 2 different syngeneic murine B-cell lymphoma models. Although RIT with 131I–anti–major histocompatibility complex class II (MHCII) was effective in targeting radiation to tumor, no improvement in survival was seen by escalating the radiation dose alone and there were no long-term survivors. In contrast, using the combination of 131I anti-MHCII in the presence of unlabeled anti-idiotype (anti-Id), 100% prolonged disease-free survival was seen in both B-cell lymphoma models at the higher radiation dose. Using in vivo tracking we show that treatment with radiation plus anti-Id monoclonal antibody (mAb) results in a substantially greater reduction of splenic tumor cells than with either treatment alone. Prolonged survival could also be achieved using 131I anti-MHCII plus the signaling anti-CD19 mAb. Furthermore, the ability of these anti–B-cell mAbs to improve survival with targeted radiotherapy appeared to correlate with their ability to initiate intracellular signal transduction. Together these data illustrate that using 1 mAb to target radiation to tumor and a second to induce cell signaling is an effective new strategy in RIT.

Cervical neuropathy following mantle radiotherapy

The majority of newly diagnosed patients with Hodgkin's lymphoma are expected to survive because of effective therapies established during the last 40 years. Long-term observations from large populations of treated patients have disclosed a variety of late effects of the disease and its therapy that have contributed morbidity and excess mortality to Hodgkin's lymphoma survivors. As such complications have been recognized treatment approaches have been modified. Here we report a case of cervical neuropathy secondary to mantle radiotherapy, a complication not previously reported in the literature.

Hypercalcaemia, parathyroid hormone-related protein and malignancy

Hypercalcaemia is the most common serious metabolic complication of malignancy. Recent advances have significantly increased our understanding of the pathophysiology of hypercalcaemia of malignancy and revealed the importance of parathyroid hormone-related protein (PTHrP) in a wide range of physiological and pathological processes. This review examines the pathophysiology of hypercalcaemia of malignancy, focusing on the role of PTHrP before discussing further pathological and physiological processes in which PTHrP may be implicated, and the impact of this knowledge on the management of malignant disease.

Antibody therapy of lymphoma

The availability of rituximab and the possible imminent availability of two new radiolabelled monoclonal anti-CD20 antibodies (Yttrium-90 (90Y)-ibritumomab and Iodine-131(131I)-tositumomab) have captured much attention in the treatment of lymphoma. The chimeric monoclonal anti-CD20 antibody, rituximab has truly heralded a new era for the treatment of lymphoma and human malignancies. The full potential of antibody-based therapy to improve the outcome in patients with B-cell non-Hodgkin's lymphoma has yet to be defined, but recent data suggests that the combination of chemotherapy plus rituximab may significantly improve outcome for patients with aggressive lymphoma over chemotherapy alone. Highly promising data are also emerging for the use of rituximab in combination with chemotherapy in other types of lymphoma. New advances in antibody therapy, driven by new technologies and defining novel antigen targets, offer the promise of more effective tumour specific therapies. Combinations of antibodies, either conjugated with radioisotopes or unlabelled, used with chemotherapy are likely to provide definitive advances in the treatment of lymphoma in the immediate future.

Polyploid giant cells provide a survival mechanism for p53 mutant cells after DNA damage

The relationships between delayed apoptosis, polyploid 'giant' cells and reproductive survivors were studied in p53-mutated lymphoma cells after DNA damage. Following severe genotoxic insult with irradiation or chemotherapy, cells arrest at the G(2)-M cell cycle check-point for up to 5 days before undergoing a few rounds of aberrant mitoses. The cells then enter endoreduplication cycles resulting in the formation of polyploid giant cells. Subsequently the majority of the giant cells die, providing the main source of delayed apoptosis; however, a small proportion survives. Kinetic analyses show a reciprocal relationship between the polyploid cells and the diploid stem line, with the stem line suppressed during polyploid cell formation and restituted after giant cell disintegration. The restituted cell-line behaves with identical kinetics to the parent line, once re-irradiated. When giant cells are isolated and followed in labelling experiments, the clonogenic survivors appear to arise from these cells. These findings imply that an exchange exists between the endocyclic (polyploid) and mitotic (diploid or tetraploid) populations during the restitution period and that giant cells are not always reproductively dead as previously supposed. We propose that the formation of giant cells and their subsequent complex breakdown and subnuclear reorganization may represent an important response of p53-mutated tumours to DNA damaging agents and provide tumours with a mechanism of repair and resistance to such treatments.

Release of mitotic descendants by giant cells from irradiated Burkitt's lymphoma cell line

Polyploid giant cells are produced as part of the response of p53 mutant Burkitt's lymphoma cell lines to high doses of irradiation. Polyploid giant cells arise by endo-reduplication in the first week after a single 10 Gray dose of irradiation. Within the giant cells a sub-nuclear structure is apparent and within this, sub-nuclear autonomy is evident, as displayed by independent nuclear structure and DNA replication in different parts of the nucleus. The majority of these cells soon die as apoptotic polykaryons. However, approximately 10-20% of giant cells remain viable into the second week after irradiation and begin vigorous extrusion of large degraded chromatin masses. During the second week, the giant cells begin to reconstruct their nuclei into polyploid 'bouquets', where chromosome double-loops are formed. Subsequently, the bouquets return to an interphase state and separate into several secondary nuclei. The individual sub-nuclei then resume DNA synthesis with mitotic divisions and sequester cytoplasmic territories around themselves, giving rise to the secondary cells, which continue mitotic propagation. This process of giant cell formation, reorganization and breakdown appears to provide an additional mechanism for repairing double-strand DNA breaks within tumour cells.

Radioimmunotherapy of cancer: using monoclonal antibodies to target radiotherapy

After years of pre-clinical and clinical testing monoclonal antibodies (mAbs) finally offer new therapeutic choices for patients with haematological and solid malignancies both as unconjugated antibody and as vectors to target radionuclides in radioimmunotherapy (RIT). In recent years some of the most exciting clinical data have come from the use of RIT in the treatment of lymphoma and haematological malignancies and it would now appear highly likely that RIT will play a major role in the treatment strategies for these diseases. For the solid tumours there has also been considerable progress with RIT and mAbs have become a component of treatment protocols for breast cancer. This review highlights the important recent clinical progress that has been made with clinical RIT and provides some new insights into the important mechanisms of action of RIT in haematological malignancies.

The importance of antibody-specificity in determining successful radioimmunotherapy of B-cell lymphoma

We report the radioimmunotherapy of mouse B-cell lymphoma, BCL1, using a panel of anti-B-cell monoclonal antibodies (MoAb) (anti-CD19, anti-CD22, anti-major histocompatibility complex (MHC) II, and anti-idiotype (Id) radiolabeled with 131-iodine. When administered early in disease (day 4), the 131I-anti-MHCII MoAb cured tumors as a result of targeted irradiation alone, the unlabeled MoAb being nontherapeutic. In contrast, 131I-anti-Id, despite targeting irradiation and having therapeutic activity as an unconjugated antibody, protected mice for only 30 days; 131I-anti-CD19 and anti-CD22 were therapeutically inactive. Binding and biodistribution studies showed that the anti-Id, unlike anti-MHCII, MoAb was cleared from target cells in vivo and delivered 4 times less irradiation to splenic tumor. Treating later in the disease (day 14) increased tumor load and produced the expected reduction in therapeutic activity with the anti-MHCII, but surprisingly, allowed 131I-anti-Id to cure most mice. This unexpected potency of 131I-anti-Id late in the disease appeared to result from the direct cytotoxicity of the anti-Id MoAb, which was more active in established disease, in combination with targeted irradiation. We believe the ability of targeted irradiation and certain cytotoxic MoAb to work cooperatively against tumor in this way has important implications for the selection of reagents in radioimmunotherapy of B-cell lymphoma.

Monoclonal antibody therapy of B cell lymphoma: signaling activity on tumor cells appears more important than recruitment of effectors

Despite the recent success of mAb in the treatment of certain malignancies, there is still considerable uncertainty about the mechanism of action of anti-cancer Abs. Here, a panel of rat anti-mouse B cell mAb, including Ab directed at surface IgM Id, CD19, CD22, CD40, CD74, and MHC class II, has been investigated in the treatment of two syngeneic mouse B cell lymphomas, BCL1 and A31. Only three mAb were therapeutically active in vivo, anti-Id, anti-CD19, and anti-CD40. mAb to the other Ags showed little or no therapeutic activity in either model despite giving good levels of surface binding and activity in Ag-dependent cellular cytotoxicity and complement assays, and in some cases inhibiting cell growth in vitro. We conclude that the activity of mAb in vitro does not predict therapeutic performance in vivo. Furthermore, in vivo tracking experiments using fluorescently tagged cells showed that anti-Id and anti-CD40 mAb probably operate via different mechanisms: the anti-Id mAb cause growth arrest that is almost immediate and does not eliminate cells over a period of 5 or 6 days, and the anti-CD40 mAb have a delayed effect that allows tumor to grow normally for 3 days, but then abruptly eradicates lymphoma cells. This work supports the belief that mAb specificity is critical to therapeutic success in lymphoma and that, in addition to any effector-recruiting activity they may possess, in vivo mAb operate via mechanisms that involve cross-linking and signaling of key cellular receptors.

Malignant hypercalcaemia in pregnancy and antenatal administration of intravenous pamidronate

A patient is reported who was found to have metastatic breast cancer in pregnancy. Intravenous pamidronate was given with beneficial effect in the third trimester. There were no serious adverse effects on the foetus.