Targeting Tumor Hypoxia Research Articles

Targeting Tumor Hypoxia with Nanoparticle-Based Therapies: Challenges, Opportunities, and Clinical Implications.

Hypoxia is a crucial factor in tumor biology, affecting various solid tumors to different extents. Its influence spans both early and advanced stages of cancer, altering cellular functions and promoting resistance to therapy. Hypoxia reduces the effectiveness of radiotherapy, chemotherapy, and immunotherapy, making it a target for improving therapeutic outcomes. Despite extensive research, gaps persist, necessitating the exploration of new chemical and pharmacological interventions to modulate hypoxia-related pathways. This review discusses the complex pathways involved in hypoxia and the associated pharmacotherapies, highlighting the limitations of current treatments. It emphasizes the potential of nanoparticle-based platforms for delivering anti-hypoxic agents, particularly oxygen (O2), to the tumor microenvironment. Combining anti-hypoxic drugs with conventional cancer therapies shows promise in enhancing remission rates. The intricate relationship between hypoxia and tumor progression necessitates novel therapeutic strategies. Nanoparticle-based delivery systems can significantly improve cancer treatment efficacy by targeting hypoxia-associated pathways. The synergistic effects of combined therapies underscore the importance of multimodal approaches in overcoming hypoxia-mediated resistance. Continued research and innovation in this area hold great potential for advancing cancer therapy and improving patient outcomes.

The Effects of Hypoxia on the Immune-Metabolic Interplay in Liver Cancer.

M2-like macrophages promote tumor growth and cancer immune evasion. This study used an in vitro model to investigate how hypoxia and tumor metabolism affect macrophage polarization. Liver cancer cells (HepG2 and VX2) and macrophages (THP1) were cultured under hypoxic (0.1% O2) and normoxic (21% O2) conditions with varying glucose levels (2 g/L or 4.5 g/L). Viability assays and extracellular pH (pHe) measurements were conducted over 96 hours. Macrophages were exposed to the tumor-conditioned medium (TCM) from the cancer cells, and polarization was assessed using arginase and nitrite assays. GC-MS-based metabolic profiling quantified TCM meta-bolites and correlated them with M2 polarization. The results showed that pHe in TCMs decreased more under hypoxia than normoxia (p < 0.0001), independent of glucose levels. The arginase assay showed hypoxia significantly induced the M2 polarization of macrophages (control group: p = 0.0120,0.1%VX2-TCM group: p = 0.0149, 0.1%HepG2-TCM group: p < 0.0001, 0.1%VX2-TCMHG group: p = 0.0001, and 0.1%HepG2-TCMHG group: p < 0.0001). TCMs also induced M2 polarization under normoxic conditions, but the strongest M2 polarization occurred when both tumor cells and macrophages were incubated under hypoxia with high glucose levels. Metabolomics revealed that several metabolites, particularly lactate, were correlated with hypoxia and M2 polarization. Under normoxia, elevated 2-amino-butanoic acid (2A-BA) strongly correlated with M2 polarization. These findings suggest that targeting tumor hypoxia could mitigate immune evasion in liver tumors. Lactate drives acidity in hypoxic tumors, while 2A-BA could be a therapeutic target for overcoming immunosuppression in normoxic conditions.

Recent Progress in Synthesis of 99mTc-labeled Complexes with Nitroimidazoles as SPECT Probes for Targeting Tumor Hypoxia.

The majority of solid tumors have hypoxia, or low oxygen levels, which is one of the hallmarks of cancer. Hypoxia was found to relate to cancer metastases and resistance to therapies, therefore, detection of hypoxia plays an important role in the process of cancer prognosis and treatment. Single-photon emission computed tomography (SPECT) is a non-invasive imaging technique using gamma-emitting radiopharmaceuticals to visualize biological activities within the body. SPECT is also applied for the detection of tumor hypoxia with the development of hypoxia-targeting radiopharmaceuticals. Radiopharmaceuticals containing nitroimidazole moieties have received increasing attention due to their bio-reducible characteristics which make the radiopharmaceuticals accumulate in the hypoxia regions. This review summarizes the recent development of 99mTc-labeled radiopharmaceuticals bearing nitroimidazoles for SPECT imaging of tumor hypoxia including the synthetic methods and results of animal studies.

Re-engineered theranostic gold nanoparticles for targeting tumor hypoxia

Developing nanovehicles for selective delivery of a radiation dose/drug to hypoxic tumors is a present-day clinical requirement for effective treatment of cancer.

Hyperoxic BOLD-MRI-Based Characterization of Breast Cancer Molecular Subtypes Is Independent of the Supplied Amount of Oxygen: A Preclinical Study.

Hyperoxic BOLD-MRI targeting tumor hypoxia may provide imaging biomarkers that represent breast cancer molecular subtypes without the use of injected contrast agents. However, the diagnostic performance of hyperoxic BOLD-MRI using different levels of oxygen remains unclear. We hypothesized that molecular subtype characterization with hyperoxic BOLD-MRI is feasible independently of the amount of oxygen. Twenty-three nude mice that were inoculated into the flank with luminal A (n = 9), Her2+ (n = 5), and triple-negative (n = 9) human breast cancer cells were imaged using a 9.4 T Bruker BioSpin system. During BOLD-MRI, anesthesia was supplemented with four different levels of oxygen (normoxic: 21%; hyperoxic: 41%, 71%, 100%). The change in the spin-spin relaxation rate in relation to the normoxic state, ΔR2*, dependent on the amount of erythrocyte-bound oxygen, was calculated using in-house MATLAB code. ΔR2* was significantly different between luminal A and Her2+ as well as between luminal A and triple-negative breast cancer, reflective of the less aggressive luminal A breast cancer's ability to better deliver oxygen-rich hemoglobin to its tissue. Differences in ΔR2* between subtypes were independent of the amount of oxygen, with robust distinction already achieved with 41% oxygen. In conclusion, hyperoxic BOLD-MRI may be used as a biomarker for luminal A breast cancer identification without the use of exogenous contrast agents.

Dual hypoxia-responsive supramolecular complex for cancer target therapy

The prognosis with pancreatic cancer is among the poorest of any human cancer. One of the important factors is the tumor hypoxia. Targeting tumor hypoxia is considered a desirable therapeutic option. However, it has not been translated into clinical success in the treatment of pancreatic cancer. With enhanced cytotoxicities against hypoxic pancreatic cancer cells, BE-43547A2 (BE) may serve as a promising template for hypoxia target strategy. Here, based on rational modification, a BE prodrug (NMP-BE) is encapsulated into sulfonated azocalix[5]arene (SAC5A) to generate a supramolecular dual hypoxia-responsive complex NMP-BE@SAC5A. Benefited from the selective load release within cancer cells, NMP-BE@SAC5A markedly suppresses tumor growth at low dose in pancreatic cancer cells xenograft murine model without developing systemic toxicity. This research presents a strategy for the modification of covalent compounds to achieve efficient delivery within tumors, a horizon for the realization of safe and reinforced hypoxia target therapy using a simple approach.

Effective drug and shRNA delivery for synergistic treatment of triple-negative breast cancer by sequentially targeting tumor hypoxia

Clinical treatment of TNBC remains challenging, due to the lack of targeted therapies. As TNBC is highly hypoxic with higher HIF-1α expression than other subtypes, we fabricated hypoxia-responsive polymeric micelles co-loading drug and shRNA to treat TNBC by targeting hypoxic tumor microenvironment and subsequently targeting overexpressed HIF-1α under hypoxia. The micelles were assembled from methoxy-polyethylene glycol (mPEG) and poly-L-lysine (PLL) copolymer with AZO as a hypoxia-responsive bridge of mPEG and PLL. Once exposed to hypoxia, AZO bridge was cleaved, resulting in the disassembly of the micelles for rapid release. In vitro and in vivo results showed that the micelles enabled simultaneous delivery of drug and shRNA to hypoxic sites for site-specific rapid release, facilitated by sensitive response to hypoxia; hypoxia-responsive shRNA delivery effectively silenced HIF-1α and its downstream genes, which not only ameliorated the response of hypoxic tumor to drug, but also modulated tumor microenvironment for further improved drug and shRNA delivery; as a result, synergistic treatment of chemotherapy and HIF-1α targeted gene therapy inhibited the growth of primary TNBC tumor and its distant metastasis in a murine model of orthotopic TNBC. Together with their good biocompatibility, hypoxia-responsive polymeric micelles thus emerged as a safe, effective, and universally applicable drug and gene carrier for treatment of TNBC as well as other hypoxic tumors.

Design and Synthesis of New Boron-Based Benzo[c][1,2,5]oxadiazoles and Benzo[c][1,2,5]thiadiazoles as Potential Hypoxia Inhibitors

Benzo[c][1,2,5]oxadiazoles and benzo[c][1,2,5]thiadiazoles are recognized to possess potent pharmacological activities including anticancer potential. In continuation of our research endeavors in the development of boron-based heterocycles as potential therapeutic agents, herein we report the design and synthesis of new series of boron-based benzo[c][1,2,5]oxadiazoles and benzo[c][1,2,5]thiadiazoles as anticancer agents targeting tumor hypoxia. A series of seventeen compounds were synthesized in two steps in an efficient manner via substitution reactions followed by subsequent hydrolysis of aryltrifluoroboronate salts into corresponding boronic acid derivatives in the presence of silica. This is the first example to develop boron-based hypoxia agents. The synthesized hybrids were characterized by suitable spectroscopic techniques. The biological studies are currently underway.

Targeting Tumor Hypoxia Inhibits Aggressive Phenotype of Dedifferentiated Thyroid Cancer.

Hypoxia is commonly observed in multiple aggressive cancers. Its role remains unclear in the biology and therapy of dedifferentiated thyroid cancer (DDTC). We aimed to elucidate hypoxia's roles in DDTC tumor biology. We discovered and confirmed hypoxia's correlation with dedifferentiation status, poor prognoses, and immune checkpoints in thyroid cancer using transcriptome data from our center and Gene Expression Omnibus (GEO) database. Then, the effect of targeting hypoxia was investigated via treating anaplastic thyroid cancer (ATC) cells with acriflavine (ACF) in vitro and in vivo, and hypoxia was analyzed for its association with response to immunotherapy in patients. Hypoxia score was positively associated with dedifferentiation status, and high hypoxia score significantly correlated with reduced overall survival, TP53 mutation, and elevated expression of immunosuppression-related markers in DDTC. ACF and siRNA targeting HIF-1α significantly suppressed growth and proliferation of thyroid cancer cells in vitro and in vivo, and reduced c-MYC and PDL1 expression in ATC. HIF-1α showed a positive correlation with PDL1 expression in DDTC. Integrated analyses of phosphoproteome and RNA sequencing data revealed that ACF's target was connected with differentiation genes and immune checkpoints via tumor-related kinases in ATC. Furthermore, hypoxia score was associated with immunotherapeutic response in some cancer types. Hypoxia score serves as a significant indicator for dedifferentiation status, prognoses, and immunotherapeutic response predicted by Tumor Immune Dysfunction and Exclusion in DDTC patients. Targeting hypoxia by ACF is useful to alleviate aggressive phenotype of ATC in a preclinical model of DDTC.

The Role of Imaging Biomarkers to Guide Pharmacological Interventions Targeting Tumor Hypoxia.

Hypoxia is a common feature of solid tumors that contributes to angiogenesis, invasiveness, metastasis, altered metabolism and genomic instability. As hypoxia is a major actor in tumor progression and resistance to radiotherapy, chemotherapy and immunotherapy, multiple approaches have emerged to target tumor hypoxia. It includes among others pharmacological interventions designed to alleviate tumor hypoxia at the time of radiation therapy, prodrugs that are selectively activated in hypoxic cells or inhibitors of molecular targets involved in hypoxic cell survival (i.e., hypoxia inducible factors HIFs, PI3K/AKT/mTOR pathway, unfolded protein response). While numerous strategies were successful in pre-clinical models, their translation in the clinical practice has been disappointing so far. This therapeutic failure often results from the absence of appropriate stratification of patients that could benefit from targeted interventions. Companion diagnostics may help at different levels of the research and development, and in matching a patient to a specific intervention targeting hypoxia. In this review, we discuss the relative merits of the existing hypoxia biomarkers, their current status and the challenges for their future validation as companion diagnostics adapted to the nature of the intervention.

Nitroimidazole-sulfonamides as carbonic anhydrase IX and XII inhibitors targeting tumor hypoxia: Design, synthesis, molecular docking and molecular dynamics simulation

In the present investigation, we focused on the development of dual drugs able to inhibit carbonic anhydrase enzyme (CA) by harboring sulfonamide group and to increase the sensitivity of hypoxic tumors to radio and chemotherapies by incorporating 5-nitroimidazole scaffold. The synthesized compounds were evaluated as cytotoxic agents under oxic and hypoxic conditions against three cell lines including human colorectal carcinoma (HCT116), epithelioid carcinoma (Hela), and mammary gland carcinoma (MCF-7) cells. Compounds 13a and 15a,b exhibited the highest cytotoxic activity against the three cell lines under both oxic (IC50 = 6.18 - 23.06 µM) and hypoxic (IC50 = 5.63 - 19.78 µM) conditions. The capability of compounds 13a and 15b to augment the lethal effect of ɤ-irradiation was evaluated. Both compounds increased the sensitivity of cancerous HCT116 cells to the cell-killing effect of ionizing radiation (IC50 = 4.18 and 2.53 µM, respectively). Sulfonamide derivatives 13a,b, 15a,b, and 17a,b were evaluated for their inhibitory effect against the tumor-associated hCA IX and XII isoforms in comparison to acetazolamide. Molecular docking and molecular dynamics simulation were performed for some sulfonamides on isoforms hCA IX and XII to understand the elements governing the inhibitory effect and the stability of interaction under dynamic conditions.

Improving the synergistic combination of programmed death-1/programmed death ligand-1 blockade and radiotherapy by targeting the hypoxic tumour microenvironment.

SummaryImmune checkpoint inhibition with PD‐1/PD‐L1 blockade is a promising area in the field of anti‐cancer therapy. Although clinical data have revealed success of PD‐1/PD‐L1 blockade as monotherapy or in combination with CTLA‐4 or chemotherapy, the combination with radiotherapy could further boost anti‐tumour immunity and enhance clinical outcomes due to the immunostimulatory effects of radiation. However, the synergistic combination of PD‐1/PD‐L1 blockade and radiotherapy can be challenged by the complex nature of the tumour microenvironment (TME), including the presence of tumour hypoxia. Hypoxia is a major barrier to the effectiveness of both radiotherapy and PD‐1/PD‐L1 blockade immunotherapy. Thus, targeting the hypoxic TME is an attractive strategy to enhance the efficacy of the combination. Addition of compounds that directly or indirectly reduce hypoxia, to the combination of PD‐1/PD‐L1 inhibitors and radiotherapy may optimize the success of the combination and improve therapeutic outcomes. In this review, we will discuss the synergistic combination of PD‐1/PD‐L1 blockade and radiotherapy and highlight the role of hypoxic TME in impeding the success of both therapies. In addition, we will address the potential approaches for targeting tumour hypoxia and how exploiting these strategies could benefit the combination of PD‐1/PD‐L1 blockade and radiotherapy.

Exploring hypoxic biology to improve radiotherapy outcomes.

Ionising radiotherapy is a well-established, effective cancer treatment modality, whose efficacy has improved with the application of newer technological modalities. However, patient outcomes are governed and potentially limited by aspects of tumour biology that are associated with radioresistance. Patients also still endure treatment-associated toxicities owed to the action of ionising radiation in normoxic tissue adjacent to the tumour mass. Tumour hypoxia is recognised as a key component of the tumour microenvironment and is well established as leading to therapy resistance and poor prognosis. In this review, we outline the current understanding of hypoxia-mediated radiotherapy resistance, before exploring targeting tumour hypoxia for radiotherapy sensitisation to improve treatment outcomes and increase the therapeutic window. This includes increasing oxygen availability in solid tumours, the use of hypoxia-activated prodrugs, targeting of hypoxia-regulated or associated signalling pathways, as well as the use of high-LET radiotherapy modalities. Ultimately, targeting hypoxic radiobiology combined with precise radiotherapy delivery modalities and modelling should be associated with improvement to patient outcomes.

DDRE-07. TARGETING TUMOR HYPOXIA AND MITOCHONDRIAL METABOLISM WITH ANTI-PARASITIC DRUGS AS AN APPROACH TO IMPROVE THE RADIOSENSITIVITY OF DIFFUSE INTRINSIC PONTINE GLIOMA

Abstract Diffuse intrinsic pontine glioma (DIPG) is an incurable pediatric brain tumor with a median survival of 12 months. Current management is limited to radiotherapy; however, the tumor recurs secondary to radioresistance. Tumor hypoxia appears to be one of the major contributors to radioresistance of DIPG, as oxygenation is critical to successful radiotherapy treatment. Therefore, strategies to alleviate hypoxia could enhance the effectiveness of radiotherapy and result in improved survival outcomes of patients with DIPG. Recent approaches to target tumor hypoxia are predicated on inhibiting mitochondrial respiration of the tumors to decrease oxygen consumption rate (OCR) and increase oxygenation. Here, we aimed to identify a safe but potent mitochondrial inhibitor that could decrease OCR and hypoxia, and improve the radiosensitivity of DIPG. A subset of anti-parasitic drugs (atovaquone, ivermectin, quinacrine, mefloquine and proguanil) which are known mitochondrial inhibitors were studied against a panel of patient-derived DIPG cell lines. We assessed their antiproliferative effects, OCR inhibition and radiosensitising efficacy using cell proliferation, extracellular flux and colony formation assays. Among the five tested drug candidates, atovaquone was found to be the most potent OCR inhibitor with minimal antiproliferative effects on DIPG cultures. It also decreased hypoxia in 3-dimensional DIPG neurospheres, reduced the expression of hypoxia-inducible factor-1α and improved the radiosensitivity of neurospheres of DIPG. Its anti-mitochondrial role was further confirmed by inhibition of various mitochondrial parameters and increase in reactive oxygen species. Overall, these results provide promising in vitro evidence of atovaquone as a hypoxia modifier and radiosensitiser in DIPG and pave a way for rapid translation to in vivo studies.

Selectively Targeting Tumor Hypoxia With the Hypoxia-Activated Prodrug CP-506.

Hypoxia-activated prodrugs (HAP) are a promising class of antineoplastic agents that can selectively eliminate hypoxic tumor cells. This study evaluates the hypoxia-selectivity and antitumor activity of CP-506, a DNA alkylating HAP with favorable pharmacologic properties. Stoichiometry of reduction, one-electron affinity, and back-oxidation rate of CP-506 were characterized by fast-reaction radiolytic methods with observed parameters fulfilling requirements for oxygen-sensitive bioactivation. Net reduction, metabolism, and cytotoxicity of CP-506 were maximally inhibited at oxygen concentrations above 1 μmol/L (0.1% O2). CP-506 demonstrated cytotoxicity selectively in hypoxic 2D and 3D cell cultures with normoxic/anoxic IC50 ratios up to 203. Complete resistance to aerobic (two-electron) metabolism by aldo-keto reductase 1C3 was confirmed through gain-of-function studies while retention of hypoxic (one-electron) bioactivation by various diflavin oxidoreductases was also demonstrated. In vivo, the antitumor effects of CP-506 were selective for hypoxic tumor cells and causally related to tumor oxygenation. CP-506 effectively decreased the hypoxic fraction and inhibited growth of a wide range of hypoxic xenografts. A multivariate regression analysis revealed baseline tumor hypoxia and in vitro sensitivity to CP-506 were significantly correlated with treatment response. Our results demonstrate that CP-506 selectively targets hypoxic tumor cells and has broad antitumor activity. Our data indicate that tumor hypoxia and cellular sensitivity to CP-506 are strong determinants of the antitumor effects of CP-506.

Phase Ib dose-escalation study of the hypoxia-modifier Myo-inositol trispyrophosphate in patients with hepatopancreatobiliary tumors

Hypoxia is prominent in solid tumors and a recognized driver of malignancy. Thus far, targeting tumor hypoxia has remained unsuccessful. Myo-inositol trispyrophosphate (ITPP) is a re-oxygenating compound without apparent toxicity. In preclinical models, ITPP potentiates the efficacy of subsequent chemotherapy through vascular normalization. Here, we report the results of an unrandomized, open-labeled, 3 + 3 dose-escalation phase Ib study (NCT02528526) including 28 patients with advanced primary hepatopancreatobiliary malignancies and liver metastases of colorectal cancer receiving nine 8h-infusions of ITPP over three weeks across eight dose levels (1'866-14'500 mg/m2/dose), followed by standard chemotherapy. Primary objectives are assessment of the safety and tolerability and establishment of the maximum tolerated dose, while secondary objectives include assessment of pharmacokinetics, antitumor activity via radiological evaluation and assessment of circulatory tumor-specific and angiogenic markers. The maximum tolerated dose is 12,390 mg/m2, and ITPP treatment results in 32 treatment-related toxicities (mostly hypercalcemia) that require little or no intervention. 52% of patients have morphological disease stabilization under ITPP monotherapy. Following subsequent chemotherapy, 10% show partial responses while 60% have stable disease. Decreases in angiogenic markers are noted in ∼60% of patients after ITPP and tend to correlate with responses and survival after chemotherapy.

68Ga-labeled PET tracers for targeting tumor hypoxia: Role of bifunctional chelators on pharmacokinetics

IntroductionBy virtue of their oxygen dependant accumulation in hypoxic cells, radiolabeled nitroimidazole analogues have been widely used for detecting tumor hypoxia. Present study evaluates two 2-nitroimidazole (2-NIM) based 68Ga-labeled radiotracers, [68Ga]Ga-DOTAGA-2-NIM and [68Ga]Ga-NODAGA-2-NIM, for hypoxia targeting applications. MethodsBifunctional chelating agents suitable for radiolabeling with 68Ga, viz. 1,4,7,10-tetraazacyclododececane,1-(glutaric acid)-4,7,10-triacetic acid (DOTAGA) and 1,4,7-triazacyclododececane,1-(glutaric acid)-4,7-diacetic acid (NODAGA), were coupled to appropriately modified 2-nitroimidazole to obtain 2-NIM-DOTAGA and 2-NIM-NODAGA, respectively. These ligands were radiolabeled using [68Ga]GaCl3 obtained from a commercial 68Ge/68Ga-generator to obtain corresponding 68Ga-complexes. Both the radiotracers were tested for their hypoxia selectivity in CHO cells under hypoxic and normoxic conditions. Biodistribution studies in fibrosarcoma tumor bearing Swiss mice were carried out to evaluate the radiotracer in vivo. ResultsThe 68Ga complexes of 2-NIM-DOTAGA and 2-NIM-NODAGA could be prepared in ~82% and ~90% yield, respectively. In vitro studies of the complexes in CHO cells showed significant accumulation of [68Ga]Ga-NODAGA-2-NIM complex under hypoxic conditions with hypoxic to normoxic ratio of 2.88 ± 0.36 at 180 min post incubation. The [68Ga]Ga-DOTAGA-2-NIM complex also showed hypoxia selectivity albeit to a lesser extent. Biodistribution studies of the complexes in Swiss mice bearing fibrosarcoma tumor showed significant tumor uptake by both radiolabeled complexes. [68Ga]Ga-NODAGA-2-NIM showed a more favorable pharmacokinetics with respect to [68Ga]Ga-DOTAGA-2-NIM. ConclusionThe nitroimidazole radiotracer with NODAGA chelator displayed more favorable pharmacokinetics and good hypoxia selectivity, making it a promising candidate for further investigation. The present study also provides an insight into the possible role of bifunctional chelator on overall pharmacokinetics of small molecule radiotracers.

A light-controlled multi-step drug release nanosystem targeting tumor hypoxia for synergistic cancer therapy.

Hypoxia is a major obstacle for cancer therapy due to its association with cell proliferation, tumor distant metastasis, and treatment resistance. In this study, a hypoxia-activated bifunctional prodrug (CC5) was designed, synthesized and encapsulated by a photo-responsive ruthenium complex-derived polymer to yield a light-controlled multi-step drug release system (CC5-RuCa) for synergistic therapy against tumor hypoxia. Under NIR irradiation, CC5-RuCa not only generated ROS to kill the cancer cells in the exterior of the tumor but also released the prodrug CC5 with enhanced intratumoral penetration in the severe hypoxia region inside the tumor tissue. In vivo studies on MDA-MB-231 xenograft models revealed that CC5-RuCa with preferential accumulation in the tumor exhibited highly efficient tumor regression through the synergistic effect of photodynamic therapy and hypoxia-activated chemotherapy.

Biological Guided Carbon-Ion Microporous Radiation to Tumor Hypoxia Area Triggers Robust Abscopal Effects as Open Field Radiation.

Recently, a growing number of studies focus on partial tumor irradiation to induce the stronger non-target effects. However, the value of partial volume carbon ion radiotherapy (CIRT) targeting hypoxic region of a tumor under imaging guidance as well as its effect of inducing radiation induced abscopal effects (RIAEs) have not been well investigated. Herein, we developed a technique of carbon ion microporous radiation (CI-MPR), guided by 18F-FMISO PET/computerized tomography (CT), for partial volume radiation targeting the hypoxia area of a tumor and investigated its capability of inducing abscopal effects. Tumor-bearing mice were inoculated subcutaneously with breast cancer 4T1 cells into the flanks of both hind legs of mouse. Mice were assigned to three groups: group I: control group with no treatment; group II: carbon ion open field radiation (CI-OFR group) targeting the entire tumor; group III: partial volume carbon ion microporous radiation (CI-MPR group) targeting the hypoxia region. The tumors on the left hind legs of mice were irradiated with single fraction of 20 Gy of CIRT. Mice treated with CI-MPR or CI-OFR showed that significant growth delay on both the irradiated and unirradiated of tumor as compared to the control groups. Tumor regression of left tumor irradiated with CI-OFR was more prominent as compared to the tumor treated with CI-MPR, while the regression of the unirradiated tumor in both CI-MPR and CI-OFR group was similar. Biological-guided CIRT using the newly developed microporous technique targeting tumor hypoxia region could induce robust abscopal effects similar to CIRT covering the entire tumor.

Abstract CT136: Phase I study with rapamycin combined with irinotecan, the SFCE RAPIRI I trial, a new way to target tumor hypoxia in pediatric refractory cancers

Abstract Background: Hypoxic environment is a pejorative prognostic factor in pediatric solid tumors (ST). It is favoring neoangiogenesis, tumor progression and resistance to treatments through the activation of mTor and HIF-1α pathways. Those hypoxic markers can be targeted by rapamycin and irinotecan, respectively. Therefore, we designed a dose-escalation phase I trial combining both drugs to inhibit tumor hypoxic mechanisms present in several pediatric refractory/relapsing ST. Procedure: Patients were enrolled in this 3+3 escalation trial with ten dose levels. The primary endpoint was to determine the maximum tolerated dose (MTD) of rapamycin when combined with irinotecan. Rapamycin was administered orally once daily in a 28-day cycle (1 to 2.5 mg/m2/day) and associated biweekly with intravenous irinotecan (125 to 240 mg/m2/dose). Toxicities, pharmacokinetics (PK), efficacy analyses and pharmacodynamics (UGT1A1 status, cytokines/chemokines assessment, MRI markers and proteins' expression) were evaluated. Results: 42 patients were treated and had mild to moderate reversible toxicities. No MTD was present up to the tenth level. The PK were highly variable. Nevertheless, the usually targeted concentrations of rapamycin over time were reached at 1.5 mg/m2/day dose. When looking to the 2 partial responses (PR) and 19 stable diseases (SD) in 31 assessable patients, the mean irinotecan AUC was 363 min.mg/L and the mean D8 rapamycin AUC was 9.3 min.mg/L. No significant relationship was observed between dose escalation and response, but progressive tumors' subgroup (PD) had slightly lower mean irinotecan AUC (321 min.mg/L) and D8 rapamycin AUC (6.5 min.mg/L). The two main tumor groups were brain tumors (BTs) and sarcomas. A high proportion of those patients experienced tumor responses (3/4 ependymomas, 2/3 medulloblastomas, 1 rhabdoid tumor, 2/3 high-grade gliomas and 5/6 osteosarcomas). In all 17 assessable patients for immunohistochemistry, the two targeted proteins, mTor and HIF-1α, were expressed, but the resistance to this double strategy was significantly linked to the HIF-2α protein hyperexpression. In the BTs, lower ADC values in MRI were also a prerequisite for tumor responsiveness. Cytokine analyses, distinguished specific proinflammatory and angiogenic signatures during first course of treatment: PR patients had an increase of TNF, associated to a stable PIGF and a decrease of VEGF-C; the SD subgroup had a significant increase of VEGF-D and a stable or increase of sFLT1 and PD group had a constant increase of IL8 and VEGF-D. Conclusion: Despite no MTD, we can propose a next phase II trial with rapamycin dose of 1.5 mg/m2/day associated with 125 mg/m2 irinotecan in STs not expressing HIF-2α protein. A precise PK follow-up will be used to reach an irinotecan AUC up to 360 min.mg/L and a D8 rapamycin blood concentration of 10 µg/L. The cytokine evaluation will help us to predict during first cycle the potential tumor response. Citation Format: Sarah Jannier, Veronique Kemmel, Consuelo Sebastia, Agathe Chammas, Amelia-Naomi Sabo, Erwan Pencreach, Françoise Farace, Benoit Lhermitte, Birgit Geoerger, Isabelle Aerts, Didier Frappaz, Pierre Leblond, Nicolas Andre, Yves Perel, Nadège Corradini, Anne Isabelle Bertozzi, Florence Vincent, Natacha Entz-Werle. Phase I study with rapamycin combined with irinotecan, the SFCE RAPIRI I trial, a new way to target tumor hypoxia in pediatric refractory cancers [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr CT136.