Mitochondria-Targeted Multifunctional Nanoparticles Combine Cuproptosis and Programmed Cell Death-1 Downregulation for Cancer Immunotherapy.

The combination of cuproptosis and immune checkpoint inhibition has shown promise in treating malignant tumors. However, it remains a challenge to deliver copper ions and immune checkpoint inhibitors efficiently and simultaneously to tumors. Herein, a mitochondria-targeted nanoscale coordination polymer particle, Cu/TI, comprising Cu(II), and a triphenylphosphonium conjugate of 5-carboxy-8-hydroxyquinoline (TI), for effective cuproptosis induction and programmed cell death-1 (PD-L1) downregulation is reported. Upon systemic administration, Cu/TI efficiently accumulates in tumor tissues to induce immunogenic cancer cell death and reduce PD-L1 expression. Consequently, Cu/TI promotes the intratumoral infiltration and activation of cytotoxic T lymphocytes to greatly inhibit tumor progression of colorectal carcinoma and triple-negative breast cancer in mouse models without causing obvious side effects.

Simultaneous Protonation and Metalation of a Porphyrin Covalent Organic Framework Enhance Photodynamic Therapy.

Covalent organic frameworks (COFs) have been explored for photodynamic therapy (PDT) of cancer, but their antitumor efficacy is limited by excited state quenching and low reactive oxygen species generation efficiency. Herein, we report a simultaneous protonation and metalation strategy to significantly enhance the PDT efficacy of a nanoscale two-dimensional imine-linked porphyrin-COF. The neutral and unmetalated porphyrin-COF (Ptp) and the protonated and metalated porphyrin-COF (Ptp-Fe) were synthesized via imine condensation between 5,10,15,20-tetrakis(4-aminophenyl)porphyrin and terephthalaldehyde in the absence and presence of ferric chloride, respectively. The presence of ferric chloride generated both doubly protonated and Fe3+-coordinated porphyrin units, which red-shifted and increased the Q-band absorption and disrupted exciton migration to prevent excited state quenching, respectively. Under light irradiation, rapid energy transfer from protonated porphyrins to Fe3+-coordinated porphyrins in Ptp-Fe enabled 1O2 and hydroxyl radical generation via type II and type I PDT processes. Ptp-Fe also catalyzed the conversion of hydrogen peroxide to hydroxy radical through a photoenhanced Fenton-like reaction under slightly acidic conditions and light illumination. As a result, Ptp-Fe-mediated PDT exhibited much higher cytotoxicity than Ptp-mediated PDT on CT26 and 4T1 cancer cells. Ptp-Fe-mediated PDT afforded potent antitumor efficacy in subcutaneous CT26 murine colon cancer and orthotopic 4T1 murine triple-negative breast tumors and prevented metastasis of 4T1 breast cancer to the lungs. This work underscores the role of fine-tuning the molecular structures of COFs in significantly enhancing their PDT efficacy.

Targeting the dendritic cell-secreted immunoregulatory cytokine CCL22 alleviates radioresistance.

PURPOSE: Radiation-mediated immune suppression limits efficacy and is a barrier in cancer therapy. Radiation induces negative regulators of tumor immunity including regulatory T cells (Treg). Mechanisms underlying Treg infiltration after radiotherapy (RT) are poorly defined. Given that dendritic cells (cDC) maintain Treg we sought to identify and target cDC signaling to block Treg infiltration after radiation. EXPERIMENTAL DESIGN: Transcriptomics and high dimensional flow cytometry revealed changes in murine tumor cDC that not only mediate Treg infiltration after RT, but associate with worse survival in human cancer datasets. Antibodies perturbing a cDC-CCL22-Treg axis were tested in syngeneic murine tumors. A prototype interferon-anti-epidermal growth factor receptor fusion protein (αEGFR-IFNα) was examined to block Treg infiltration and promote a CD8+ T cell response after RT. RESULTS: Radiation expands a population of mature cDC1 enriched in immunoregulatory markers that mediates Treg infiltration via the Treg-recruiting chemokine CCL22. Blocking CCL22 or Treg depletion both enhanced RT efficacy. αEGFR-IFNα blocked cDC1 CCL22 production while simultaneously inducing an antitumor CD8+ T cell response to enhance RT efficacy in multiple EGFR-expressing murine tumor models, including following systemic administration. CONCLUSIONS: We identify a previously unappreciated cDC mechanism mediating Treg tumor infiltration after RT. Our findings suggest blocking the cDC1-CCL22-Treg axis augments RT efficacy. αEGFR-IFNα added to RT provided robust antitumor responses better than systemic free interferon administration, and may overcome clinical limitations to interferon therapy. Our findings highlight the complex behavior of cDC after RT and provide novel therapeutic strategies for overcoming RT-driven immunosuppression to improve RT efficacy.

Radiotherapy and immunology.

The majority of cancer patients receive radiotherapy during the course of treatment, delivered with curative intent for local tumor control or as part of a multimodality regimen aimed at eliminating distant metastasis. A major focus of research has been DNA damage; however, in the past two decades, emphasis has shifted to the important role the immune system plays in radiotherapy-induced anti-tumor effects. Radiotherapy reprograms the tumor microenvironment, triggering DNA and RNA sensing cascades that activate innate immunity and ultimately enhance adaptive immunity. In opposition, radiotherapy also induces suppression of anti-tumor immunity, including recruitment of regulatory T cells, myeloid-derived suppressor cells, and suppressive macrophages. The balance of pro- and anti-tumor immunity is regulated in part by radiotherapy-induced chemokines and cytokines. Microbiota can also influence radiotherapy outcomes and is under clinical investigation. Blockade of the PD-1/PD-L1 axis and CTLA-4 has been extensively investigated in combination with radiotherapy; we include a review of clinical trials involving inhibition of these immune checkpoints and radiotherapy.

Radiotherapy Enhances Metastasis Through Immune Suppression by Inducing PD-L1 and MDSC in Distal Sites.

PURPOSE: Radiotherapy (RT) is a widely employed anticancer treatment. Emerging evidence suggests that RT can elicit both tumor-inhibiting and tumor-promoting immune effects. The purpose of this study is to investigate immune suppressive factors of radiotherapy. EXPERIMENTAL DESIGN: We used a heterologous two-tumor model in which adaptive concomitant immunity was eliminated. RESULTS: Through analysis of PD-L1 expression and myeloid-derived suppressor cells (MDSC) frequencies using patient peripheral blood mononuclear cells and murine two-tumor and metastasis models, we report that local irradiation can induce a systemic increase in MDSC, as well as PD-L1 expression on dendritic cells and myeloid cells, and thereby increase the potential for metastatic dissemination in distal, nonirradiated tissue. In a mouse model using two distinct tumors, we found that PD-L1 induction by ionizing radiation was dependent on elevated chemokine CXCL10 signaling. Inhibiting PD-L1 or MDSC can potentially abrogate RT-induced metastasis and improve clinical outcomes for patients receiving RT. CONCLUSIONS: Blockade of PD-L1/CXCL10 axis or MDSC infiltration during irradiation can enhance abscopal tumor control and reduce metastasis.

Reconciling the discrepancies in randomized data of combining immunotherapy and radiation therapy: Not all radiotherapy is created equal.

It remains highly unclear and debatable whether combining radiotherapy (RT) and immune checkpoint blocker (ICB) therapy yields improved outcomes compared to either modality alone. Whereas some randomized data have shown improved outcomes, others have not. As a result of these conflicting data, it is essential to reconcile differences in the data and postulate reasons thereof. This work seeks to address these discrepancies, and uses the lessons learned from both positive and negative trials, including the most cutting-edge data available, in order to guide future clinical trial design and clarify the ideal/expected role of combinatorial therapy going forward. Because RT offers two distinct contributions (cytoreductive (local) effects & immune-stimulating (systemic) effects), RT should complement immunotherapy by addressing immunotherapy-resistant clones, and immunotherapy should complement RT by addressing RT-resistant or out-of-field clones. RT is not merely a single "drug", but rather a constellation of diverse "drugs" that can be varied based on dose regimens, previous systemic therapy regimens, number of irradiated sites, treatment intent/location/timing, tumor biology, and individual patient immunological circumstances. These factors are discussed as an important explanation for the discrepancies in results of various randomized trials in heterogeneous populations and clinical settings, and these discrepancies may continue until trials of more uniform circumstances are designed to use particular RT paradigms that meaningfully add value to systemic therapy.

Nanoparticles Synergize Ferroptosis and Cuproptosis to Potentiate Cancer Immunotherapy.

The recent discovery of copper-mediated and mitochondrion-dependent cuproptosis has aroused strong interest in harnessing this novel mechanism of cell death for cancer therapy. Here the design of a core-shell nanoparticle, CuP/Er, for the co-delivery of copper (Cu) and erastin (Er) to cancer cells for synergistic cuproptosis and ferroptosis is reported. The anti-Warburg effect of Er sensitizes tumor cells to Cu-mediated cuproptosis, leading to irreparable mitochondrial damage by depleting glutathione and enhancing lipid peroxidation. CuP/Er induces strong immunogenic cell death, enhances antigen presentation, and upregulates programmed death-ligand 1 expression. Consequently, CuP/Er promotes proliferation and infiltration of T cells, and when combined with immune checkpoint blockade, effectively reinvigorates T cells to mediate the regression of murine colon adenocarcinoma and triple-negative breast cancer and prevent tumor metastasis. This study suggests a unique opportunity to synergize cuproptosis and ferroptosis with combination therapy nanoparticles to elicit strong antitumor effects and potentiate current cancer immunotherapies.

Immunogenic Bifunctional Nanoparticle Suppresses Programmed Cell Death-Ligand 1 in Cancer and Dendritic Cells to Enhance Adaptive Immunity and Chemo-Immunotherapy.

Blockade of programmed cell death-1/programmed cell death-ligand 1 (PD-L1) immune checkpoints with monoclonal antibodies has shown great promise for cancer treatment, but these antibodies can cause immune-related adverse events in normal organs. Here we report a dual-cell targeted chemo-immunotherapeutic nanoscale coordination polymer (NCP), OxPt/BP, comprising oxaliplatin (OxPt) and 2-bromopalmitic acid (BP), for effective downregulation of PD-L1 expression in both cancer cells and dendritic cells (DCs) by inhibiting palmitoyl acyltransferase DHHC3. OxPt/BP efficiently promotes DC maturation by increasing intracellular oxidative stress and enhancing OxPt-induced immunostimulatory immunogenic cancer cell death. Systemic administration of OxPt/BP reduces the growth of subcutaneous and orthotopic colorectal carcinoma by facilitating the infiltration and activation of cytotoxic T lymphocytes together with reducing the population of immunosuppressive regulatory T cells. As a result, OxPt/BP significantly extends mouse survival without causing side effects. This work highlights the potential of NCPs in simultaneously reprogramming cancer cells and DCs for potent cancer treatment.

Nanoscale Covalent Organic Framework with Staggered Stacking of Phthalocyanines for Mitochondria-Targeted Photodynamic Therapy.

Phthalocyanine photosensitizers (PSs) have shown promise in fluorescence imaging and photodynamic therapy (PDT) of malignant tumors, but their practical application is limited by the aggregation-induced quenching (AIQ) and inherent photobleaching of PSs. Herein, we report the synthesis of a two-dimensional nanoscale covalent organic framework (nCOF) with staggered (AB) stacking of zinc-phthalocyanines (ZnPc), ZnPc-PI, for fluorescence imaging and mitochondria-targeted PDT. ZnPc-PI isolates and confines ZnPc PSs in the rigid nCOF to reduce AIQ, improve photostability, enhance cellular uptake, and increase the level of reactive oxygen species (ROS) generation via mitochondrial targeting. ZnPc-PI shows efficient tumor accumulation, which allowed precise tumor imaging and nanoparticle tracking. With high cellular uptake and tumor accumulation, intrinsic mitochondrial targeting, and enhanced ROS generation, ZnPc-PI exhibits potent PDT efficacy with >95% tumor growth inhibition on two murine colon cancer models without causing side effects.

RNA m6A methylation and MDSCs: Roles and therapeutic implications for radiotherapy.

Emerging evidence suggests that local tumor radiotherapy reshapes the repertoire of circulating myeloid-derived suppressor cells (MDSCs) and leads to their infiltration into the tumor microenvironment, which poses a major obstacle for radiotherapy efficacy. Recent findings have identified RNA m6A modification at the nexus of both anti-tumor immunity and radiation response. Here, we examine the mechanisms by which this RNA modification modulates the immune milieu of the radiation-remodeled tumor microenvironment. We discuss potential therapeutic interventions targeting m6A machinery to improve radiotherapy response.

Corrigendum: Absolute oxygen-guided radiation therapy improves tumor control in three preclinical tumor models.

[This corrects the article DOI: 10.3389/fmed.2023.1269689.].

Absolute oxygen-guided radiation therapy improves tumor control in three preclinical tumor models.

Background: Clinical attempts to find benefit from specifically targeting and boosting resistant hypoxic tumor subvolumes have been promising but inconclusive. While a first preclinical murine tumor type showed significant improved control with hypoxic tumor boosts, a more thorough investigation of efficacy from boosting hypoxic subvolumes defined by electron paramagnetic resonance oxygen imaging (EPROI) is necessary. The present study confirms improved hypoxic tumor control results in three different tumor types using a clonogenic assay and explores potential confounding experimental conditions. Materials and methods: Three murine tumor models were used for multi-modal imaging and radiotherapy: MCa-4 mammary adenocarcinomas, SCC7 squamous cell carcinomas, and FSa fibrosarcomas. Registered T2-weighted MRI tumor boundaries, hypoxia defined by EPROI as pO2 ≤ 10 mmHg, and X-RAD 225Cx CT boost boundaries were obtained for all animals. 13 Gy boosts were directed to hypoxic or equal-integral-volume oxygenated tumor regions and monitored for regrowth. Kaplan-Meier survival analysis was used to assess local tumor control probability (LTCP). The Cox proportional hazards model was used to assess the hazard ratio of tumor progression of Hypoxic Boost vs. Oxygenated Boost for each tumor type controlling for experimental confounding variables such as EPROI radiofrequency, tumor volume, hypoxic fraction, and delay between imaging and radiation treatment. Results: An overall significant increase in LTCP from Hypoxia Boost vs. Oxygenated Boost treatments was observed in the full group of three tumor types (p < 0.0001). The effects of tumor volume and hypoxic fraction on LTCP were dependent on tumor type. The delay between imaging and boost treatments did not have a significant effect on LTCP for all tumor types. Conclusion: This study confirms that EPROI locates resistant tumor hypoxic regions for radiation boost, increasing clonogenic LTCP, with potential enhanced therapeutic index in three tumor types. Preclinical absolute EPROI may provide correction for clinical hypoxia images using additional clinical physiologic MRI.

Nanoscale coordination polymer synergizes photodynamic therapy and toll-like receptor activation for enhanced antigen presentation and antitumor immunity.

While activating antitumor immunity with toll-like receptor (TLR) agonists provides a promising approach toward cancer immunotherapy, existing TLR agonists, including resiquimod (R848), have shown poor tumor selectivity and ineffective TLR activation in tumors for optimal antitumor effects. We hypothesized that improved delivery of TLR agonists to tumors and their effective combination with tumor antigens could significantly enhance their antitumor efficacy. Here, we report a novel nanoscale coordination polymer, Ce6/R848, for the co-delivery of Ce6 photosensitizer to elicit immunogenic cell death via photodynamic therapy (PDT) and cholesterol-conjugated R848 (Chol-R848) for tumor-selective TLR7/8 activation. Upon light irradiation, Ce6-mediated PDT released tumor antigens while selectively delivered R848 activated TLR7/8 in the tumors to synergistically activate antigen-presenting cells and prime T cells for enhanced innate and adaptive antitumor immune responses. Ce6/R848 achieved a 50% cure rate and 99.4% inhibition of tumor growth in subcutaneous MC38 colorectal tumors with minimal systemic toxicity.

Mechanoregulatory Cholesterol Oxidase-Functionalized Nanoscale Metal-Organic Framework Stimulates Pyroptosis and Reinvigorates T Cells.

Cancer cells alter mechanical tension in their cell membranes. New interventions to regulate cell membrane tension present a potential strategy for cancer therapy. Herein, the increase of cell membrane tension by cholesterol oxidase (COD) via cholesterol depletion in vitro and the design of a COD-functionalized nanoscale metal-organic framework, Hf-TBP/COD, for cholesterol depletion and mechanoregulation of tumors in vivo, are reported. COD is found to deplete cholesterol and disrupt the mechanical properties of lipid bilayers, leading to decreased cell proliferation, migration, and tolerance to oxidative stress. Hf-TBP/COD increases mechanical tension of plasma membranes and osmotic fragility of cancer cells, which induces influx of calcium ions, inhibits cell migration, increases rupturing propensity for effective caspase-1 mediated pyroptosis, and decreases tolerance to oxidative stress. In the tumor microenvironment, Hf-TBP/COD downregulates multiple immunosuppressive checkpoints to reinvigorate T cells and enhance T cell infiltration. Compared to Hf-TBP, Hf-TBP/COD improves anti-tumor immune response and tumor growth inhibition from 54.3% and 79.8% to 91.7% and 95% in a subcutaneous triple-negative breast cancer model and a colon cancer model, respectively.

Nanoscale Metal-Organic Framework with an X-ray Triggerable Prodrug for Synergistic Radiotherapy and Chemotherapy.

As heavy-metal-based nanoscale metal-organic frameworks (nMOFs) are excellent radiosensitizers for radiotherapy via enhanced energy deposition and reactive oxygen species (ROS) generation, we hypothesize that nMOFs with covalently conjugated and X-ray triggerable prodrugs can harness the ROS for on-demand release of chemotherapeutics for chemoradiotherapy. Herein, we report the design of a novel nMOF, Hf-TP-SN, with an X-ray-triggerable 7-ethyl-10-hydroxycamptothecin (SN38) prodrug for synergistic radiotherapy and chemotherapy. Upon X-ray irradiation, electron-dense Hf12 secondary building units serve as radiosensitizers to enhance hydroxyl radical generation for the triggered release of SN38 via hydroxylation of the 3,5-dimethoxylbenzyl carbonate followed by 1,4-elimination, leading to 5-fold higher release of SN38 from Hf-TP-SN than its molecular counterpart. As a result, Hf-TP-SN plus radiation induces significant cytotoxicity to cancer cells and efficiently inhibits tumor growth in colon and breast cancer mouse models.

Integrated Clinical-Molecular Classification of Colorectal Liver Metastases: A Biomarker Analysis of the Phase 3 New EPOC Randomized Clinical Trial.

Importance: Personalized treatment approaches for patients with oligometastatic colorectal liver metastases are critically needed. We previously defined 3 biologically distinct molecular subtypes of colorectal liver metastases: (1) canonical, (2) immune, and (3) stromal. Objective: To independently validate these molecular subtypes in the phase 3 New EPOC randomized clinical trial. Design, Setting, and Participants: This retrospective secondary analysis of the phase 3 New EPOC randomized clinical trial included a bi-institutional discovery cohort and multi-institutional validation cohort. The discovery cohort comprised patients who underwent hepatic resection for limited colorectal liver metastases (98% received perioperative chemotherapy) from May 31, 1994, to August 14, 2012. The validation cohort comprised patients who underwent hepatic resection for liver metastases with perioperative chemotherapy (fluorouracil, oxaliplatin, and irinotecan based) with or without cetuximab from February 26, 2007, to November 1, 2012. Data were analyzed from January 18 to December 10, 2021. Interventions: Resected metastases underwent RNA sequencing and microRNA (miRNA) profiling in the discovery cohort and messenger RNA and miRNA profiling with microarray in the validation cohort. Main Outcomes and Measures: A 31-feature (24 messenger RNAs and 7 miRNAs) neural network classifier was trained to predict molecular subtypes in the discovery cohort and applied to the validation cohort. Integrated clinical-molecular risk groups were designated based on molecular subtypes and the clinical risk score. The unique biological phenotype of each molecular subtype was validated using gene set enrichment analyses and immune deconvolution. The primary clinical end points were progression-free survival (PFS) and overall survival (OS). Results: A total of 240 patients were included (mean [range] age, 63.0 [56.3-68.0] years; 151 [63%] male), with 93 in the discovery cohort and 147 in the validation cohort. In the validation cohort, 73 (50%), 28 (19%), and 46 (31%) patients were classified as having canonical, immune, and stromal metastases, respectively. The biological phenotype of each subtype was concordant with the discovery cohort. The immune subtype (best prognosis) demonstrated 5-year PFS of 43% (95% CI, 25%-60%; hazard ratio [HR], 0.37; 95% CI, 0.20-0.68) and OS of 63% (95% CI, 40%-79%; HR, 0.38; 95% CI, 0.17-0.86), which was statistically significantly higher than the canonical subtype (worst prognosis) at 14% (95% CI, 7%-23%) and 43% (95% CI, 32%-55%), respectively. Adding molecular subtypes to the clinical risk score improved prediction (the Gönen and Heller K for discrimination) from 0.55 (95% CI, 0.49-0.61) to 0.62 (95% CI, 0.57-0.67) for PFS and 0.59 (95% CI, 0.52-0.66) to 0.63 (95% CI, 0.56-0.70) for OS. The low-risk integrated group demonstrated 5-year PFS of 44% (95% CI, 20%-66%; HR, 0.38; 95% CI, 0.19-0.76) and OS of 78% (95% CI, 44%-93%; HR, 0.26; 95% CI, 0.08-0.84), superior to the high-risk group at 16% (95% CI, 10%-24%) and 43% (95% CI, 32%-52%), respectively. Conclusions and Relevance: In this prognostic study, biologically derived colorectal liver metastasis molecular subtypes and integrated clinical-molecular risk groups were highly prognostic. This novel molecular classification warrants further study as a possible predictive biomarker for personalized systemic treatment for colorectal liver metastases. Trial Registration: isrctn.org Identifier: ISRCTN22944367.

YTHDF2/m6 A/NF-κB axis controls anti-tumor immunity by regulating intratumoral Tregs.

N6 -methyladenosine (m6 A) in messenger RNA (mRNA) regulates immune cells in homeostasis and in response to infection and inflammation. The function of the m6 A reader YTHDF2 in the tumor microenvironment (TME) in these contexts has not been explored. We discovered that the loss of YTHDF2 in regulatory T (Treg) cells reduces tumor growth in mice. Deletion of Ythdf2 in Tregs does not affect peripheral immune homeostasis but leads to increased apoptosis and impaired suppressive function of Treg cells in the TME. Elevated tumor necrosis factor (TNF) signaling in the TME promotes YTHDF2 expression, which in turn regulates NF-κB signaling by accelerating the degradation of m6 A-modified transcripts that encode NF-κB-negative regulators. This TME-specific regulation of Treg by YTHDF2 points to YTHDF2 as a potential target for anti-cancer immunotherapy, where intratumoral Treg cells can be targeted to enhance anti-tumor immune response while avoiding Treg cells in the periphery to minimize undesired inflammations.

YTHDF2 inhibition potentiates radiotherapy antitumor efficacy.

RNA N6-methyladenosine (m6A) modification is implicated in cancer progression. However, the impact of m6A on the antitumor effects of radiotherapy and the related mechanisms are unknown. Here we show that ionizing radiation (IR) induces immunosuppressive myeloid-derived suppressor cell (MDSC) expansion and YTHDF2 expression in both murine models and humans. Following IR, loss of Ythdf2 in myeloid cells augments antitumor immunity and overcomes tumor radioresistance by altering MDSC differentiation and inhibiting MDSC infiltration and suppressive function. The remodeling of the landscape of MDSC populations by local IR is reversed by Ythdf2 deficiency. IR-induced YTHDF2 expression relies on NF-κB signaling; YTHDF2 in turn leads to NF-κB activation by directly binding and degrading transcripts encoding negative regulators of NF-κB signaling, resulting in an IR-YTHDF2-NF-κB circuit. Pharmacological inhibition of YTHDF2 overcomes MDSC-induced immunosuppression and improves combined IR and/or anti-PD-L1 treatment. Thus, YTHDF2 is a promising target to improve radiotherapy (RT) and RT/immunotherapy combinations.

Partial tumor irradiation plus pembrolizumab in treating large advanced solid tumor metastases.

BACKGROUNDWe previously demonstrated the safety of stereotactic body radiotherapy followed by pembrolizumab (SBRT+P) in patients with advanced solid tumors. This phase I clinical trial was expanded to study the safety of partial tumor irradiation (partial-Rx). We assessed irradiated local failure (LF) and clinical outcomes with correlations to biomarkers including CD8+ T cell radiomics score (RS) and circulating cytokines.METHODSPatients received SBRT to 2-4 metastases and pembrolizumab for up to 7 days after SBRT. Tumors measuring up to 65 cc received the full radiation dose (complete-Rx), whereas tumors measuring more than 65 cc received partial-Rx. Landmark analysis was used to assess the relationship between tumor response and overall survival (OS). Multivariable analysis was performed for RS and circulating cytokines.RESULTSIn the combined (expansion plus original) cohort, 97 patients (219 metastases) were analyzed and received SBRT+P. Forty-six (47%) patients received at least 1 partial-Rx treatment. There were 7 (7.2%)dose-limiting toxicities (DLTs). 1-year LF was 7.6% overall, and 13.3% and 5.4% for partial-Rx and complete-Rx tumors, respectively (HR 2.32, 95% CI 0.90-5.97, P = 0.08). The overall, unirradiated, and irradiated objective response rates were 22%, 12%, and 34%, respectively. Irradiated tumor response to SBRT+P was associated with prolonged OS; 1-year OS was 71% (responders), 42% (mixed-responders), and 0% (nonresponders) (P < 0.01). High-RS was significantly associated with improved LF, progression-free survival (PFS), and OS. Elevated circulating IL-8 was independently associated with inferior PFS and OS.CONCLUSIONSBRT+P is safe in patients with large, advanced solid tumors. Additional studies are warranted to assess noninferiority of complete versus partial irradiation of tumors in the setting of immunotherapy.TRIAL REGISTRATIONClinicaltrials.gov NCT02608385FUNDINGMerck Investigator Studies Program; Hillman Fellows for Innovative Cancer Research Program; NIH grants UM1CA186690-06, P50CA254865-01A1, P30CA047904-32, and R01DE031729-01A1.

Oligometastases: Characterizing the Role of Epigenetic Regulation of Epithelial-Mesenchymal Transition.

The "oligometastasis" hypothesis proposes that metastases exist as a spectrum and are not always disseminated. According to this theory, a subset of patients with metastatic disease could benefit from aggressive local therapies. However, the identification of patients most likely to exhibit an oligometastatic phenotype remains challenging. Recent literature focusing on basic and translational studies has identified novel epigenetic regulators of epithelial-mesenchymal transition (EMT) and the emergence of a spectrum of metastatic behavior. Herein, we review these scientific advances and suggest that the spectrum of metastatic virulence produced by these epigenetic mechanisms broadly contributes to the emergence of clinically evident "oligometastases." Epigenetic regulation of EMT programs can result in a spectrum of cell trajectories (e.g., quasi-mesenchymal and highly mesenchymal states) with differential propensity to develop metastases. We propose that quasi-mesenchymal cell states may be associated with a polymetastatic phenotype, whereas highly mesenchymal cell states may be associated with a more oligometastatic phenotype. The mechanisms governing epigenetic regulation of EMT and its array of intermediate states are multifaceted and may contribute to the development of the metastatic spectrum observed clinically. Within this context, translational studies that support the role of EMT and its epigenetic regulation are discussed. Continued translation of these mechanistic discoveries into novel biomarkers may help optimally select patients most likely to exhibit an oligometastatic phenotype and benefit from aggressive local therapies, such as surgery, radiotherapy, and other ablative procedures.