Faculty Bibliography

The discovery and development of novel treatments that harness the patient's immune system and prevent immune escape has dramatically improved outcomes for patients across cancer types. However, not all patients respond to immunotherapy, acquired resistance remains a challenge, and responses are poor in certain tumors which are considered to be immunologically cold. This has led to the need for new immunotherapy-based approaches, including adoptive cell transfer (ACT), therapeutic vaccines, and novel immune checkpoint inhibitors. These new approaches are focused on patients with an inadequate response to current treatments, with emerging evidence of improved responses in various cancers with new immunotherapy agents, often in combinations with existing agents. The use of cell therapies, drivers of immune response, and trends in immunotherapy were the focus of the Immunotherapy Bridge (November 30th-December 1st, 2022), organized by the Fondazione Melanoma Onlus, Naples, Italy, in collaboration with the Society for Immunotherapy of Cancer.

Tryptophan catabolism is a major metabolic pathway utilized by several professional and non-professional antigen presenting cells to maintain immunological tolerance. Here we report that 3-hydroxy-L-kynurenamine (3-HKA) is a biogenic amine produced via an alternative pathway of tryptophan metabolism. In vitro, 3-HKA has an anti-inflammatory profile by inhibiting the IFN-γ mediated STAT1/NF-κΒ pathway in both mouse and human dendritic cells (DCs) with a consequent decrease in the release of pro-inflammatory chemokines and cytokines, most notably TNF, IL-6, and IL12p70. 3-HKA has protective effects in an experimental mouse model of psoriasis by decreasing skin thickness, erythema, scaling and fissuring, reducing TNF, IL-1β, IFN-γ, and IL-17 production, and inhibiting generation of effector CD8⁺ T cells. Similarly, in a mouse model of nephrotoxic nephritis, besides reducing inflammatory cytokines, 3-HKA improves proteinuria and serum urea nitrogen, overall ameliorating immune-mediated glomerulonephritis and renal dysfunction. Overall, we propose that this biogenic amine is a crucial component of tryptophan-mediated immune tolerance.

Improved understanding of tumor immunology has enabled the development of therapies that harness the immune system and prevent immune escape. Numerous clinical trials and real-world experience has provided evidence of the potential for long-term survival with immunotherapy in various types of malignancy. Recurring observations with immuno-oncology agents include their potential for clinical application across a broad patient population with different tumor types, conventional and unconventional response patterns, durable responses, and immune-related adverse events. Despite the substantial achievements to date, a significant proportion of patients still fail to benefit from current immunotherapy options, and ongoing research is focused on transforming non-responders to responders through the development of novel treatments, new strategies to combination therapy, adjuvant and neoadjuvant approaches, and the identification of biomarkers of response. These topics were the focus of the virtual Immunotherapy Bridge (December 2nd-3rd, 2020), organized by the Fondazione Melanoma Onlus, Naples, Italy, in collaboration with the Society for Immunotherapy of Cancer and are summarised in this report.

BACKGROUND:Previous phase 2 trials of neoadjuvant anti-PD-1 or anti-PD-L1 monotherapy in patients with early-stage non-small-cell lung cancer have reported major pathological response rates in the range of 15-45%. Evidence suggests that stereotactic body radiotherapy might be a potent immunomodulator in advanced non-small-cell lung cancer (NSCLC). In this trial, we aimed to evaluate the use of stereotactic body radiotherapy in patients with early-stage NSCLC as an immunomodulator to enhance the anti-tumour immune response associated with the anti-PD-L1 antibody durvalumab. METHODS:We did a single-centre, open-label, randomised, controlled, phase 2 trial, comparing neoadjuvant durvalumab alone with neoadjuvant durvalumab plus stereotactic radiotherapy in patients with early-stage NSCLC, at NewYork-Presbyterian and Weill Cornell Medical Center (New York, NY, USA). We enrolled patients with potentially resectable early-stage NSCLC (clinical stages I-IIIA as per the 7th edition of the American Joint Committee on Cancer) who were aged 18 years or older with an Eastern Cooperative Oncology Group performance status of 0 or 1. Eligible patients were randomly assigned (1:1) to either neoadjuvant durvalumab monotherapy or neoadjuvant durvalumab plus stereotactic body radiotherapy (8 Gy × 3 fractions), using permuted blocks with varied sizes and no stratification for clinical or molecular variables. Patients, treating physicians, and all study personnel were unmasked to treatment assignment after all patients were randomly assigned. All patients received two cycles of durvalumab 3 weeks apart at a dose of 1·12 g by intravenous infusion over 60 min. Those in the durvalumab plus radiotherapy group also received three consecutive daily fractions of 8 Gy stereotactic body radiotherapy delivered to the primary tumour immediately before the first cycle of durvalumab. Patients without systemic disease progression proceeded to surgical resection. The primary endpoint was major pathological response in the primary tumour. All analyses were done on an intention-to-treat basis. This trial is registered with ClinicalTrial.gov, NCT02904954, and is ongoing but closed to accrual. FINDINGS/RESULTS:Between Jan 25, 2017, and Sept 15, 2020, 96 patients were screened and 60 were enrolled and randomly assigned to either the durvalumab monotherapy group (n=30) or the durvalumab plus radiotherapy group (n=30). 26 (87%) of 30 patients in each group had their tumours surgically resected. Major pathological response was observed in two (6·7% [95% CI 0·8-22·1]) of 30 patients in the durvalumab monotherapy group and 16 (53·3% [34·3-71·7]) of 30 patients in the durvalumab plus radiotherapy group. The difference in the major pathological response rates between both groups was significant (crude odds ratio 16·0 [95% CI 3·2-79·6]; p<0·0001). In the 16 patients in the dual therapy group with a major pathological response, eight (50%) had a complete pathological response. The second cycle of durvalumab was withheld in three (10%) of 30 patients in the dual therapy group due to immune-related adverse events (grade 3 hepatitis, grade 2 pancreatitis, and grade 3 fatigue and thrombocytopaenia). Grade 3-4 adverse events occurred in five (17%) of 30 patients in the durvalumab monotherapy group and six (20%) of 30 patients in the durvalumab plus radiotherapy group. The most frequent grade 3-4 events were hyponatraemia (three [10%] patients in the durvalumab monotherapy group) and hyperlipasaemia (three [10%] patients in the durvalumab plus radiotherapy group). Two patients in each group had serious adverse events (pulmonary embolism [n=1] and stroke [n=1] in the durvalumab monotherapy group, and pancreatitis [n=1] and fatigue [n=1] in the durvalumab plus radiotherapy group). No treatment-related deaths or deaths within 30 days of surgery were reported. INTERPRETATION/CONCLUSIONS:Neoadjuvant durvalumab combined with stereotactic body radiotherapy is well tolerated, safe, and associated with a high major pathological response rate. This neoadjuvant strategy should be validated in a larger trial. FUNDING/BACKGROUND:AstraZeneca.

PURPOSE/OBJECTIVE:Recent preclinical data suggest that cyclin-dependent kinase 4/6 (CDK4/6) inhibition may be harnessed to sensitize estrogen receptor (ER)+ breast cancer (BC) to radiation therapy (RT). However, these findings were obtained in human ER+ BC cell lines exposed to subclinical doses of CDK4/6 inhibitors with limited attention to treatment schedule. We investigated the activity of RT combined with the prototypic CDK4/6 inhibitor palbociclib placing emphasis on therapeutic schedule. EXPERIMENTAL DESIGN/METHODS:We combined RT and palbociclib in various doses and therapeutic schedules in human and mouse models of ER+ and ER- BC, including an immunocompetent mouse model that recapitulates key features of human luminal B BC in women. We assessed proliferation, cell death, cell cycle control and clonogenic survival in vitro, as well as tumor growth, overall survival and metastatic dissemination in vivo. RESULTS:RT and palbociclib employed as standalone agents had partial cytostatic effects in vitro, correlating with suboptimal tumor control in vivo. However, while palbociclib delivered before focal RT provided minimal benefits as compared to either treatment alone, delivering focal RT before palbociclib mediated superior therapeutic effects, even in the absence of p53. Such superiority manifested in vitro with enhanced cytostasis and loss of clonogenic potential, as well as in vivo with improved local and systemic tumor control. CONCLUSIONS:Our preclinical findings demonstrate that RT delivered before CDK4/6 inhibitors mediates superior antineoplastic effects compared to alternative treatment schedules, calling into question the design of clinical trials administering CDK4/6 inhibitors before RT in women with ER+ BC.

Recent evidence indicates that ionizing radiation can enhance immune responses to tumors. Advances in radiation delivery techniques allow hypofractionated delivery of conformal radiotherapy. Hypofractionation or other modifications of standard fractionation may improve radiation's ability to promote immune responses to tumors. Other novel delivery options may also affect immune responses, including T-cell activation and tumor-antigen presentation changes. However, there is limited understanding of the immunological impact of hypofractionated and unique multifractionated radiotherapy regimens, as these observations are relatively recent. Hence, these differences in radiotherapy fractionation result in distinct immune-modulatory effects. Radiation oncologists and immunologists convened a virtual consensus discussion to identify current deficiencies, challenges, pitfalls and critical gaps when combining radiotherapy with immunotherapy and making recommendations to the field and advise National Cancer Institute on new directions and initiatives that will help further development of these two fields.This commentary aims to raise the awareness of this complexity so that the need to study radiation dose, fractionation, type and volume is understood and valued by the immuno-oncology research community. Divergence of approaches and findings between preclinical studies and clinical trials highlights the need for evaluating the design of future clinical studies with particular emphasis on radiation dose and fractionation, immune biomarkers and selecting appropriate end points for combination radiation/immune modulator trials, recognizing that direct effect on the tumor and potential abscopal effect may well be different. Similarly, preclinical studies should be designed as much as possible to model the intended clinical setting. This article describes a conceptual framework for testing different radiation therapy regimens as separate models of how radiation itself functions as an immunomodulatory 'drug' to provide alternatives to the widely adopted 'one-size-fits-all' strategy of frequently used 8 Gy×3 regimens immunomodulation.

Over the last few years, numerous clinical trials and real-world experience have provided a large amount of evidence demonstrating the potential for long-term survival with immunotherapy agents across various malignancies, beginning with melanoma and extending to other tumours. The clinical success of immune checkpoint blockade has encouraged increasing development of other immunotherapies. It has been estimated that there are over 3000 immuno-oncology trials ongoing, targeting hundreds of disease and immune pathways. Evolving topics on cancer immunotherapy, including the state of the art of immunotherapy across various malignancies, were the focus of discussions at the Immunotherapy Bridge meeting (4-5 December, 2019, Naples, Italy), and are summarised in this report.

Increased regulatory T cells (Tregs) after radiation therapy have been reported, but the mechanisms of their induction remain incompletely understood. TGFβ is known to foster Treg differentiation within tumors and is activated following radiation therapy. Thus, we hypothesized that TGFβ blockade would result in decreased Tregs within the irradiated tumor microenvironment (TME). We found increased Tregs in the tumors of mice treated with focal radiotherapy and TGFβ blockade. This increase was mediated by upregulation of another TGFβ family member, activin A. In vitro, activin A secretion was increased following irradiation of mouse and human breast cancer cells, and its expression was further enhanced upon TGFβ blockade. In vivo, dual blockade of activin A and TGFβ was required to decrease intratumoral Tregs in the context of radiation. This resulted in an increase in CD8+ T-cell priming and was associated with a reduced tumor recurrence rate. Combination of immune checkpoint inhibitors with the dual blockade of activin A and TGFβ led to the development of tumor-specific memory responses in irradiated breast cancer. Supporting the translational value of activin A targeting to reduce Treg-mediated immunosuppression, retrospective analysis of a public dataset of breast cancer patients revealed a positive correlation between activin A gene expression and Treg abundance. Overall, these results shed light on an immune escape mechanism driven by activin A, and suggest that dual targeting of activin A and TGFβ may be required to optimally unleash radiation-induced antitumor immunity against breast cancer.

Radiation therapy (RT) is highly effective due to its ability to physically focus the treatment to target the tumor while sparing normal tissue and its ability to be combined with systemic therapy. This systemic therapy can be utilized before RT as an adjuvant or induction treatment, during RT as a radiation "sensitizer," or following RT as a part of combined modality therapy. As part of a unique concept of using radiation as "focused biology" we investigated how tumors and normal tissues adapt to clinically relevant multi-fraction (MF) and single-dose (SD) radiation to observe whether the adaptations can induce susceptibility to cell killing by available drugs or by immune enhancement. We identified an adaptation occurring after MF (3 x 2 Gy) that induced cell killing when AKT-mTOR inhibitors were delivered following cessation of RT. Additionally, we identified inducible changes in integrin expression 2 months following cessation of RT that differ between MF (1 Gy x 10) and SD (10 Gy) that remain targetable compared to pre-RT. Adaptation is reflected across different "omics" studies, and thus the range of possible molecular targets is not only broad but also time, dose, and schedule dependent. While much remains to be studied about the radiation adaptive response, radiation should be characterized by its molecular perturbations in addition to physical dose. Consideration of the adaptive effects should result in the design of a tailored radiotherapy treatment plan that accounts for specific molecular changes to be targeted as part of precision multi-modality cancer treatment.

Cell cycle proteins that are often dysregulated in malignant cells, such as cyclin-dependent kinase 4 (CDK4) and CDK6, have attracted considerable interest as potential targets for cancer therapy. In this context, multiple inhibitors of CDK4 and CDK6 have been developed, including three small molecules (palbociclib, abemaciclib and ribociclib) that are currently approved for the treatment of patients with breast cancer and are being extensively tested in individuals with other solid and haematological malignancies. Accumulating preclinical and clinical evidence indicates that the anticancer activity of CDK4/CDK6 inhibitors results not only from their ability to block the cell cycle in malignant cells but also from a range of immunostimulatory effects. In this Review, we discuss the ability of anticancer cell cycle inhibitors to modulate various immune functions in support of effective antitumour immunity.