Gold nanoparticle-enhanced radiotherapy: Dependence of the macroscopic dose enhancement on the microscopic localization of the nanoparticles within the tumor vasculature.

In gold nanoparticle-enhanced radiotherapy, intravenously administered nanoparticles tend to accumulate in the tumor tissue by means of the so-called permeability and retention effect and upon irradiation with x-rays, the nanoparticles release a secondary electron field that increases the absorbed dose that would otherwise be obtained from the interaction of the x-rays with tissue alone. The concentration of the nanoparticles in the tumor, number of nanoparticles per unit of mass, which determines the total absorbed dose imparted, can be measured via magnetic resonance or computed tomography images, usually with a resolution of several millimeters. Using a tumor vasculature model with a resolution of 500 nm, we show that for a given concentration of nanoparticles, the dose enhancement that occurs upon irradiation with x-rays greatly depends on whether the nanoparticles are confined to the tumor vasculature or have already extravasated into the surrounding tumor tissue. We show that, compared to the reference irradiation with no nanoparticles present in the tumor model, irradiation with the nanoparticles confined to the tumor vasculature, either in the bloodstream or attached to the inner blood vessel walls, results in a two to three-fold increase in the absorbed dose to the whole tumor model, with respect to an irradiation when the nanoparticles have already extravasated into the tumor tissue. Therefore, it is not enough to measure the concentration of the nanoparticles in a tumor, but the location of the nanoparticles within each volume element of a tumor, be it inside the vasculature or the tumor tissue, needs to be determined as well if an accurate estimation of the resultant absorbed dose distribution, a key element in the success of a radiotherapy treatment, is to be made.

Endostar Synergizes with Radiotherapy to Inhibit Angiogenesis of Cervical Cancer in a Subcutaneous Xenograft Mouse Model.

BACKGROUND: To investigate the synergic effect and underlying mechanism of Endostar, a recombinant human endostatin used for anti-angiogenesis, in radiotherapy for cervical cancer. METHODS: The Cell Counting Kit-8 (CCK-8) assay and plate cloning experiment were first employed to analyze the proliferation of HeLa and SiHa cervical cancer cells and human umbilical vein vascular endothelial cells (HUVECs). Flow cytometry was used to detect apoptosis and cell cycle progression. A tube formation assay was used to assess angiogenesis in vitro. The expression of gamma H2A histone family member X (γ-H2AX) and activation of the vascular endothelial growth factor receptor (VEGFR) signaling pathway were detected by immunofluorescence and western blotting, respectively. In a HeLa xenograft model, tumor tissue expression of CD31 and alpha smooth muscle actin and serum expression of VEGF-A were detected by immunohistochemistry (IHC) and enzyme-linked immunosorbent assay, respectively. RESULTS: The CCK-8 and plate cloning assays showed that Endostar and radiotherapy synergistically inhibited the growth of HUVECs but not HeLa and SiHa cells. The flow cytometric results showed that Endostar only promoted radiotherapy-induced apoptosis and G2/M phase arrest in HUVECs (p < 0.05). Endostar combined with radiotherapy also significantly inhibited tube formation by HUVECs (p < 0.05). Furthermore, Endostar inhibited the radiotherapy-induced expression of γH2AX (p < 0.05) and phosphorylation of VEGFR2/PI3K/AKT/DNA-PK in HUVECs (p < 0.05). IHC showed that Endostar enhanced the inhibitory effect of radiotherapy on the microvessel density in xenograft tumor tissues (p < 0.05), as well as serum VEGF-A expression (p < 0.05). The tumor volume in the combination therapy groups (1200 mm3) was significantly lower than in the control group (2500 mm3; p < 0.05). CONCLUSIONS: Our findings provide experimental evidence and a theoretical basis for the application of Endostar in combination with irradiation for anti-cervical cancer treatment.

Towards the virtual tumor for optimizing radiotherapy treatments of hypoxic tumors: A novel model of heterogeneous tissue vasculature and oxygenation.

PURPOSE: Tumor oxygenation is one of the key features influencing the response of cells to radiation and chemo therapies. This study presents a novel in silico tumor model simulating realistic 3D microvascular structures and related oxygenation maps, featuring regions with different levels and typologies of hypoxia (chronic, acute and anemic). Such model, if integrated into a treatment planning system, could allow evaluations and comparisons of various scenarios when deciding the therapy to administer. METHODS AND MATERIALS: Spherical tumors between 0.6 and 1.5 cm in diameter encompassed uniformly by vascular trees generated starting from pseudo-fractal principles were simulated with a voxel resolution of 10 µm. The approach ensures a continuous transition from a well-perfused rim to a core with poor vascularization. The oxygen diffusion equation in the tumor is solved by a finite difference method. Several quantities, such as the fractal dimension (FD), the microvascular density (MVD) and the hypoxic fraction (HF) were assessed and compared. RESULTS: Different tumors with various degrees of chronic hypoxia were simulated by varying the tumor size and the number of bifurcations in the vascular networks. The simulations showed that for the case of chronically hypoxic tumors, in well-oxygenated volumes FD = 2.53 ± 0.07, MVD = 3460 ± 2180 vessels/mm3 and HF = 4.0 ± 3.4%, while in hypoxic volumes FD = 2.34 ± 0.09, MVD = 365 ± 156 vessels/mm3, HF = 49.8 ± 18.3%. The superimposition of acute or anemic hypoxia accentuated the oxygen deprivation in the core of the volumes. CONCLUSIONS: Tumors varying in diameter and extension of their vasculature were simulated, showing features that define two distinctive subvolumes in terms of oxygenation. The model could be regarded as a testbed for simulations of key radiobiological features governing the tumor response to radio- and chemotherapy and thus for treatment outcome simulations.

Help or hindrance: The obesity paradox in cancer treatment response.

Obesity is a rising epidemic, the influence of which on cancer development, progression as well as its impact on current standard of care cancer treatments is profound with many facets. Obesity is emerging as a modulating factor in many cancer therapies, such as chemotherapy, radiotherapy, immunotherapy and combination therapies. It has been reported to diminish the efficacy of some treatments but has also been alluded to being protective in terms of reduced treatment toxicities, thus the evolution of the obesity paradox. The obese tumour microenvironment influences treatment response through modulation of a series of aspects, including altered adipocyte secretome, angiogenesis, hypoxia, fibrosis, free fatty acid uptake as well as a modulated immune landscape. However, the influence of these underlying mechanisms on cancer treatment response and the biological action of adipose tissue is still largely unknown. Elucidation of these facets may lead to the enhanced efficacy of current treatment options or the identification of novel methods to combat cancer in the obese tumour microenvironment.

Three-year clinical and optical coherence tomography follow-up after stereotactic radiotherapy for neovascular age-related macular degeneration.

PURPOSE: The long-term clinical outcome of adjuvant stereotactic radiotherapy (SRT) in neovascular age-related macular degeneration (nAMD) patients was evaluated. METHODS: This case-control study included patients with unilateral nAMD, who underwent SRT complementary to standard anti-VEGF treatment. Only patients with monthly follow-up over at least three years were considered. Number of intravitreal injections, visual acuity (VA), central retinal thickness (CRT), and subfoveal choroidal thickness (SFCT) were evaluated and compared to baseline as well as to an age- and gender-matched control group, who received anti-VEGF monotherapy. RESULTS: Twenty patients were irradiated and had complete follow-up. Cumulatively, SRT patients needed significantly less injections than non-irradiated ones over three years (14 vs. 18, p â€‹= â€‹0.014), while median VA did not show statistically significant changes (0.4 logMAR at baseline to 0.65 logMAR at final follow-up, p â€‹= â€‹0.061). CRT remained steady, but SFCT showed a continuous thinning of almost 50 â€‹µm (p â€‹= â€‹0.031) in irradiated patients over three years. Multiple linear regression analysis revealed that SFCT and VA at time of irradiation are significant prognostic factors of VA change in SRT patients over the following three years (F(2,17) â€‹= â€‹23.946, p<0.001, R2 of 0.738). CONCLUSIONS: SRT significantly reduced the cumulative anti-VEGF treatment burden over three years, however, this was mainly driven by the results of the first year after irradiation. A thinner SFCT at time of irradiation was associated with poorer visual outcome. While further research and investigation are warranted to elucidate the underlying pathogenesis, SFCT could be a potential biomarker when evaluating a patient's suitability for SRT.

Tumor vasculature-targeted 10B delivery by an Annexin A1-binding peptide boosts effects of boron neutron capture therapy.

BACKGROUND: p-Boronophenylalanine (10BPA) is a powerful 10B drug used in current clinical trials of BNCT. For BNCT to be successful, a high (500 mg/kg) dose of 10BPA must be administered over a few hours. Here, we report BNCT efficacy after rapid, ultralow-dose administration of either tumor vasculature-specific annexin A1-targeting IFLLWQR (IF7)-conjugated 10BPA or borocaptate sodium (10BSH). METHODS: (1) IF7 conjugates of either 10B drugs intravenously injected into MBT2 bladder tumor-bearing mice and biodistribution of 10B in tumors and normal organs analyzed by prompt gamma-ray analysis. (2) Therapeutic effect of IF7-10B drug-mediated BNCT was assessed by either MBT2 bladder tumor bearing C3H/He mice and YTS-1 tumor bearing nude mice. RESULTS: Intravenous injection of IF7C conjugates of either 10B drugs into MBT2 bladder tumor-bearing mice promoted rapid 10B accumulation in tumor and suppressed tumor growth. Moreover, multiple treatments at ultralow (10-20 mg/kg) doses of IF7-10B drug-mediated BNCT significantly suppressed tumor growth in a mouse model of human YTS-1 bladder cancer, with increased Anxa1 expression in tumors and infiltration by CD8-positive lymphocytes. CONCLUSIONS: We conclude that IF7 serves as an efficient 10B delivery vehicle by targeting tumor tissues via the tumor vasculature and could serve as a relevant vehicle for BNCT drugs.

Effects of photobiomodulation on annulus fibrosus cells derived from degenerative disc disease patients exposed to microvascular endothelial cells conditioned medium.

Intervertebral disc (IVD) degeneration with chronic low back pain is associated with neo-vascularisation into the deeper IVD regions. During this process, endothelial cells (ECs), which are primarily responsible for angiogenesis, interact with the adjacent annulus fibrosus (AF) cells, which are the first line of defence against the invasion of vascular structures into deeper IVD regions. However, the accumulation of inflammatory and catabolic enzymes that results from this interaction promotes matrix degradation and an inflammatory response. Thus, regulating the production of these mediators and catabolic enzymes could ameliorate IVD degeneration. Photobiomodulation (PBM) therapy is a non-invasive stimulation known to have biologically beneficial effects on wound healing, tissue repair, and inflammation. Here, we examined the effects of PBM, administered at various wavelengths (645, 525, and 465 nm) and doses (16, 32, and 64 J/cm2), on EC-stimulated human AF cells. Our results show that PBM selectively inhibited the EC-mediated production of inflammatory mediators, catabolic enzymes, and neurotrophins by human AF cells in a dose- and wavelength-dependent manner. These results suggest that PBM could be a superior and advanced treatment strategy for IVD degeneration.

Radiofrequency irradiation attenuates angiogenesis and inflammation in UVB-induced rosacea in mouse skin.

Rosacea is a skin inflammatory condition accompanied by cutaneous signs such as oedema, flushing, erythema, telangiectasia and pustules. Generally, rosacea is triggered by ultraviolet B (UVB) exposure. When exposed to UVB, skin epidermis thickens and produces elevated levels of pro-inflammatory cytokines, especially keratinocyte-related VEGF, a potent angiogenic factor. The upregulations of VEGF expression and its secretion promote the formation of new blood vessels and exacerbates rosacea. In this study, radiofrequency (RF) irradiation reduced keratinocyte proliferation in the epidermal layer, the expressions of pro-inflammatory cytokines, angiogenesis-related inflammatory factors and VEGF in our UVB-induced model of rosacea in vitro and in vivo. RF irradiation attenuated VEGF-induced angiogenesis-associated processes such as tube formation, cell migration and endothelial cell proliferation. Notably, blood vessel densities in the skins of UVB-treated mice and rosacea patients were significantly decreased by RF irradiation. These results provide experimental and molecular evidence regarding the effectiveness of RF irradiation for the treatment of rosacea.

High-Dose Radiation Increases Notch1 in Tumor Vasculature.

PURPOSE: The aim of this study is to characterize the effects of high-dose radiation therapy (HDRT) on Notch signaling components of the tumor vasculature. METHODS AND MATERIALS: Human umbilical vein endothelial cells monolayers were exposed to different single fraction doses of irradiation; ribonucleic acid RNA was isolated and polymerase chain reaction was performed for Notch signaling components. The vascular response to radiation therapy was examined in a xenograft model of neuroblastoma. Tumors were treated with 0 Gy, 2 Gy, and 12 Gy single fraction doses and analyzed by double immunofluorescence staining for Notch1, Notch ligands Jagged1 and Dll4, and the endothelial cell (EC) marker endomucin. To assess the role of Notch in vivo, NGP xenograft tumors expressing Fc or Notch1-1-24-decoy (a novel Notch inhibitor) were treated with 0 Gy and 12 Gy. Immunofluorescence staining for endomucin and endomucin/αSMA was performed to analyze the effect of combination treatment on tumor EC and endothelial-to-mesenchymal-transition (EndMT), respectively. RESULTS: In human umbilical vein endothelial cells monolayers doses ≥8 Gy increased expression of NOTCH1, JAG1, and Notch target genes HEY1 and HEY2 as early as 6 hours after irradiation. In vivo, 12 Gy significantly increased Notch1 and Jagged1 in tumor ECs compared with 0 Gy or 2 Gy after 72 hours. Combining HDRT with Notch inhibition using the Notch1-1-24-decoy resulted in a greater loss of EC coverage of tumor vessels than HDRT alone at 6 hours and 72 hours post treatment. Notch inhibition reduced EndMT induced by HDRT, as indicated by diminished αSMA staining in ECs. CONCLUSIONS: HDRT induced Notch1 expression and increased Notch1 signaling in the endothelial component of tumor vasculature, which was not observed with lower doses. This increase in Notch1 activation might protect tumor vessels from HDRT induced damage and regulate EndMT process.

MiR-9-5p could promote angiogenesis and radiosensitivity in cervical cancer by targeting SOCS5.

OBJECTIVE: The aim of this study was to investigate the molecular mechanism of miRNA-9-5p in cervical cancer. PATIENTS AND METHODS: The expression level of microRNA-9-5p (miR-9-5p) in cervical cancer (CC) tissues and cell lines was examined by quantitative Real Time-Polymerase Chain Reaction. Cells were transfected with Lipofectamine 3000. Cell proliferation was measured by Cell Counting Kit-8 (CCK-8). Invasion assays were performed in 24-well transwell chambers system with 8 µm pores. Cell invasion was evaluated by transwell assay. Western blot was used to detect the changes of epithelial-mesenchymal transition (EMT) and SOCS5. The effects of miR-9-5p on tubule formation were examined under different doses of γ radiation. Immunohistochemistry assay was used to analyze the protein expression of SOCS5. Fluorescence microscopy analysis was used to measure autophagosomes after cells treated with γ irradiation. RESULTS: From the Cancer Genome Atlas (TCGA) database, the expression of miR-9-5p was significantly higher in cervical cancer patients than in the negative ones, and it was verified in 22 paired of lymph node-positive patient tissues and negative. The overexpression of miR-9-5p promoted proliferation and invasion of cervical cancer cells in vitro and primary tumor growth in vivo. MiR-9-5p reduced the tubule generation after the radiation dose of 4Gy. Besides, we identified SOCS5 as the target of miR-9-5p, and the overexpression of SOCS5 could inhibit miR-9-5p mimics from promoting tubule formation. CONCLUSIONS: MiR-9-5p could promote proliferation and invasion of CC cells in vitro and in vivo. MiR-9-5p could affect angiogenesis and radiosensitivity of CC cells by targeting SOCS5.

Low­intensity pulsed ultrasound promotes apoptosis and inhibits angiogenesis via p38 signaling­mediated endoplasmic reticulum stress in human endothelial cells.

Aberrant increase in angiogenesis contributes to the progression of malignant solid tumors. An alternative anti­angiogenesis therapy is critical for cancer, since the current anti­angiogenesis drugs lack specificity for tumor cells. In the present study, the effects and mechanisms of low­intensity pulsed ultrasound (LIPUS) on human umbilical vein endothelial cells (HUVECs) and human microvascular endothelial cells (HMECs) were investigated, and the therapeutic potential of this technology was assessed. HUVECs and HMECs were treated with LIPUS (0.5 MHz; 210 mW/cm2) for 1 min and cultured for 24 h. Flow cytometry and Cell Counting Kit­8 assays demonstrated that LIPUS treatment at a dose of 210 mW/cm2 promoted apoptosis and decreased the viability in HUVECs and HMECs. Real­time cell analysis also revealed that LIPUS did not affect the proliferation or migration of HUVECs. An endothelial cell tube formation assay indicated that LIPUS treatment inhibited the angiogenic ability of HUVECs and HMECs. Furthermore, LIPUS increased the protein levels of the apoptosis­associated cleaved Caspase­3 and decreased the B­cell lymphoma­2 levels. LIPUS increased the phosphorylation of p38 mitogen­activated protein kinase (MAPK), and the levels of endoplasmic reticulum (ER) stress­associated markers, including activating transcription factor­4 (ATF­4) and phosphorylated eukaryotic initiation factor 2α (eIF2α). The p38 inhibitor SB203580 reversed the pro­apoptotic and anti­angiogenic effects of LIPUS in cells. Finally, inhibition of p38 decreased the LIPUS­induced elevation of p­eIF2α and ATF­4 levels. Taken together, these results suggested that LIPUS promoted apoptosis and inhibited angiogenesis in human endothelial cells via the activation of p38 MAPK­mediated ER stress signaling.

Angiogenesis in 90Y-Radioembolization of Colorectal Liver Metastases.

In order to evaluate the role of angiogenesis in 90Y-radioembolization for colorectal cancer liver metastasis an overview was provided of angiogenic growth factors and their function, the angiogenic mechanisms in colorectal cancer, the role of hypoxia, and the advances in antiangiogenic therapy. Last, the use of circulating angiogenic growth factors in 90Y-radioembolization was reviewed. Two literature searches were conducted. A search query in PubMed on angiogenesis in colorectal cancer, and a systematic search in PubMed (Medline), Embase, and the Cochrane Library (October 2018) with synonyms for "radioembolization" and "angiogenic growth factor." The first search yielded 3 relevant publications on the role of angiogenic growth factors in colorectal cancer, hypoxia, and antiangiogenic therapy. The second search yielded two prospective studies on circulating angiogenic factors and their relationship with response and survival after 90Y-radioembolization for colorectal cancer liver metastases. Rises in circulating angiogenic growth factors after radioembolization were seen in both studies. High baseline values of Ang-2 and IL-8 correlated with shorter survival and post 90Y-radiembolization rises in Ang-2 and HGF correlated with early progression. Various angiogenic growth factors play a role in the development and progression of colorectal cancer. Several factors show correlation with poor outcomes after 90Y-radioembolization and might be used for patient selection in the future, however, validation in larger comparative studies is required.

Dual Modality Radiation With External Beam Radiation Therapy and Transarterial Radioembolization for Hepatocellular Carcinoma With Gross Vascular Invasion.

OBJECTIVES: Patients with hepatocellular carcinoma (HCC) and gross vascular invasion (GVI) have poor outcomes with systemic therapy such as sorafenib. Both external beam radiation therapy (EBRT) and transarterial radioembolization (TARE) have been utilized for this patient population. We sought to compare outcomes using dual modality radiation (EBRT+TARE) versus EBRT alone in patients with HCC and GVI. MATERIALS AND METHODS: Between 2011 and 2017, 45 patients with HCC and GVI were treated with EBRT±TARE at our institution. Progression-free survival (PFS) and overall survival (OS) were assessed and compared using Kaplan-Meier method and log-rank test. Univariable and multivariable Cox proportional hazards regression was used to assess the impact of the variables stage, etiology of cirrhosis, Child-Pugh (CP) score, and Karnofsky Performance Score (KPS) on PFS and OS. RESULTS: Patient characteristics were well-balanced except for KPS (80 vs. 90) and CP score. Median OS for patients receiving EBRT+TARE was 263 days (95% confidence interval [CI]: 167, -) versus 193 days (95% CI: 51, 262) for EBRT alone (P=0.049). However, this did not hold up on MVA. When EBRT and TARE were delivered within 2 months as planned (n=12), median PFS was 218 days (95% CI: 44, -) for dual modality radiation versus 63 days (95% CI: 38, 137) for EBRT alone (P=0.048). When EBRT and TARE were delivered within 6 months, the difference in PFS was no longer seen (P=NS), because some patients received TARE as a salvage therapy. CONCLUSIONS: Dual modality radiation with EBRT and TARE may be associated with improved OS in patients with HCC and GVI. Dual modality radiation may be associated with improved PFS in patients with HCC and GVI compared with EBRT alone when EBRT and TARE are delivered within 2 months of each other as part of a planned dual modality treatment strategy. However, since this is a retrospective study with inherent selection bias, these findings need further validation in a prospective clinical trial for patients with HCC and GVI.

Improved survival with radiotherapy in hepatocellular carcinoma with major vascular invasion: A propensity-matched analysis of Surveillance, Epidemiology, and End Results database.

OBJECTIVES: Hepatocellular carcinoma (HCC) associated with major vascular invasion is an advanced stage disease with an extremely poor prognosis and low survival rate. Our study evaluated the survival benefit of radiotherapy (RT) in HCC patients with major vascular invasion through Surveillance, Epidemiology, and End Results database. METHODS: We analyzed 3181 HCC patients with major vascular invasion cases diagnosed from 2004 to 2013. Patients (N = 308) who underwent RT and patients (N = 2873) who did not receive RT were compared. We successfully analyzed patients using propensity score matching (PSM). Kaplan-Meier and Cox-regression analyses were applied to assess prognosis. RESULTS: The median survival time in radiation-treated group was longer compared to the control group (7 months vs 3 months; P < 0.001) in the overall sample and 3 months longer compared to the control group (7 months vs 4 months; P < 0.001) in a PSM cohort. Cox-regression analyses showed that radiation-treated patients in propensity-matched sample had a significantly lower risk of mortality (HR: 0.625, 95% CI: 0.522-0.749, P < 0.001) compared with untreated patients. The radiation-treated groups had better survival rate than untreated group. Subgroup analysis revealed that the survival time of patients in radiation-treated group was significantly longer than that in the untreated group (P < 0.001 and P = 0.026, respectively). The subgroup analysis also revealed that RT provides a survival benefit regardless of race, marital status, and tumor size after PSM. CONCLUSIONS: Radiotherapy provides improves survival in HCC patients with major vascular invasion, especially for tumor(s) confined to one lobe and not on surface of liver.

CD105 (endoglin) expression as a prognostic marker of angiogenesis in squamous cell cervical cancer treated with radical radiotherapy.

INTRODUCTION: Increased levels of endoglin may represent a new reagent of active neovascularization and angiogenesis process in various cancer types. The prognostic value of tumor CD105 (endoglin) expression in cervical squamous cell cancer (CSCC) patients treated with radical radiotherapy (RT) ± chemotherapy was investigated. MATERIALS AND METHODS: CD105 (endoglin) expression was assessed by immunohistochemical methods in seventy patients, who were treated with radical RT ± chemotherapy for CSCC. The prognostic effects of CD105 on patient and treatment characteristics, local-regional control, and survival were assessed. RESULTS: The median follow-up was 24 (5-99) months for the whole cohort. The median CD105 microvessel density was 55.5 (range; 12-136). Age (≤61 vs. >61 years; P = 0.015), lymph node metastasis status (absent vs. present; P = 0.028), International Federation of Gynecology and Obstetrics stage (Ib-IIa vs. IIb-IVa; P = 0.036), cycles of concurrent chemotherapy (1-3 vs. 4-6 cycles; P = 0.001), and hemoglobin levels (≤10 g/dL vs. >10 g/dL; P = 0.006) appeared to associate significantly with overall survival on univariate analysis. DISCUSSION: No correlation was identified between the tumor CD105 (endoglin) expression and survival in CSCC patients treated with radical RT ± chemotherapy.

Novel 4D-MRI of tumor infiltrating vasculature: characterizing tumor and vessel volume motion for selective boost volume definition in pancreatic radiotherapy.

BACKGROUND: Pancreatic ductal adenocarcinoma has dismal prognosis. Most patients receive radiation therapy (RT), which is complicated by respiration induced organ motion in upper abdomen. The purpose of this study is to report our early clinical experience in a novel self-gated k-space sorted four-dimensional magnetic resonance imaging (4D-MRI) with slab-selective (SS) excitation to highlight tumor infiltrating blood vessels for pancreatic RT. METHODS: Ten consecutive patients with borderline resectable or locally advanced pancreatic cancer were recruited to the study. Non-contrast 4D-MRI with and without slab-selective excitation and 4D-CT with delay contrast were performed on all patients. Vessel-tissue CNR were calculated for aorta and critical vessels (superior mesenteric artery or superior mesenteric vein) encompassed by tumor. Respiratory motion trajectories for tumor, as well as involved vessels were analyzed on SS-4D-MRI. Intra-class cross correlation (ICC) between tumor volume and involved vessels were calculated. RESULTS: Among all 4D imaging modalities evaluated, SS-4D-MRI sampling trajectory results in images with highest vessel-tissue CNR comparing to non-slab-selective 4D-MRI and 4D-CT for all patients studied. Average (±standard deviation) CNR for involved vessels are 13.1 ± 8.4 and 3.2 ± 2.7 for SS-4D-MRI and 4D-CT, respectively. The ICC factors comparing tumor and involved vessels motion trajectories are 0.93 ± 0.10, 0.65 ± 0.31 and 0.77 ± 0.23 for superior-inferior, anterior-posterior and medial-lateral directions respectively. CONCLUSIONS: A novel 4D-MRI sequence based on 3D-radial sampling and slab-selective excitation has been assessed for pancreatic cancer patients. The non-contrast 4D-MRI images showed significantly better contrast to noise ratio for the vessels that limit tumor resectability compared to 4D-CT with delayed contrast. The sequence has great potential in accurately defining both the tumor and boost volume margins for pancreas RT with simultaneous integrated boost.

Radiation-Induced Transformation of Immunoregulatory Networks in the Tumor Stroma.

The implementation of novel cancer immunotherapies in the form of immune checkpoint blockers represents a major advancement in the treatment of cancer, and has renewed enthusiasm for identifying new ways to induce antitumor immune responses in patients. Despite the proven efficacy of neutralizing antibodies that target immune checkpoints in some refractory cancers, many patients do not experience therapeutic benefit, possibly owing to a lack of antitumor immune recognition, or to the presence of dominant immunosuppressive mechanisms in the tumor microenvironment (TME). Recent developments in this field have revealed that local radiotherapy (RT) can transform tumors into in situ vaccines, and may help to overcome some of the barriers to tumor-specific immune rejection. RT has the potential to ignite tumor immune recognition by generating immunogenic signals and releasing neoantigens, but the multiple immunosuppressive forces in the TME continue to represent important barriers to successful tumor rejection. In this article, we review the radiation-induced changes in the stromal compartments of tumors that could have an impact on tumor immune attack. Since different RT regimens are known to mediate strikingly different effects on the multifarious elements of the tumor stroma, special emphasis is given to different RT schedules, and the time after treatment at which the effects are measured. A better understanding of TME remodeling following specific RT regimens and the window of opportunity offered by RT will enable optimization of the design of novel treatment combinations.

Tumour cell dormancy as a contributor to the reduced survival of GBM patients who received standard therapy.

Glioblastoma multiforme (GBM) is a fatal cancer with varying life expectancy, even for patients undergoing the same standard therapy. Identification of differentially expressed genes in GBM patients with different survival rates may benefit the development of effective therapeutic strategies. In the present study, key pathways and genes correlated with survival in GBM patients were screened with bioinformatic analysis. Included in the study were 136 eligible patients who had undertaken surgical resection of GBM followed by temozolomide (TMZ) chemoradiation and long-term therapy with TMZ. A total of 383 differentially expressed genes (DEGs) related to GBM survival were identified. Gene Ontology and pathway enrichment analysis as well as hub gene screening and module analysis were performed. As expected, angiogenesis and migration of GBM cells were closely correlated with a poor prognosis. Importantly, the results also indicated that cell dormancy was an essential contributor to the reduced survival of GBM patients. Given the lack of specific targeted genes and pathways known to be involved in tumour cell dormancy, we proposed enriched candidate genes related to the negative regulation of cell proliferation, signalling pathways regulating pluripotency of stem cells and neuroactive ligand-receptor interaction, and 3 hub genes (FTH1, GRM1 and DDIT3). Maintaining persistent cell dormancy or preventing tumour cells from entering dormancy during chemoradiation should be a promising therapeutic strategy.

Abemaciclib, a Selective CDK4/6 Inhibitor, Enhances the Radiosensitivity of Non-Small Cell Lung Cancer In Vitro and In Vivo.

Purpose: To characterize the ionizing radiation (IR) enhancing effects and underlying mechanisms of the CDK4/6 inhibitor abemaciclib in non-small cell lung cancer (NSCLC) cells in vitro and in vivoExperimental Design: IR enhancement by abemaciclib in a variety of NSCLC cell lines was assessed by in vitro clonogenic assay, flow cytometry, and target inhibition verified by immunoblotting. IR-induced DNA damage repair was evaluated by γH2AX analysis. Global metabolic alterations by abemaciclib and IR combination were evaluated by LC/MS mass spectrometry and YSI bioanalyzer. Effects of abemaciclib and IR combination in vivo were studied by xenograft tumor regrowth delay, xenograft lysate immunoblotting, and tissue section immunohistochemistry.Results: Abemaciclib enhanced the radiosensitivity of NSCLC cells independent of RAS or EGFR status. Enhancement of radiosensitivity was lost in cell lines deficient for functional p53 and RB protein. After IR, abemaciclib treatment inhibited DNA damage repair as measured by γH2AX. Mechanistically, abemaciclib inhibited RB phosphorylation, leading to cell-cycle arrest. It also inhibited mTOR signaling and reduced intracellular amino acid pools, causing nutrient stress. In vivo, abemaciclib, when administered in an adjuvant setting for the second week after fractionated IR, further inhibited vasculogenesis and tumor regrowth, with sustained inhibition of RB/E2F activity, mTOR pathway, and HIF-1 expression. In summary, our study signifies inhibiting the CDK4/6 pathway by abemaciclib in combination with IR as a promising therapeutic strategy to treat NSCLC.Conclusions: Abemaciclib in combination with IR enhances NSCLC radiosensitivity in preclinical models, potentially providing a novel biomarker-driven combination therapeutic strategy for patients with NSCLC. Clin Cancer Res; 24(16); 3994-4005. ©2018 AACR.

Role of Acid Sphingomyelinase and Ceramide in Mechano-Acoustic Enhancement of Tumor Radiation Responses.

Background: High-dose radiotherapy (>8-10 Gy) causes rapid endothelial cell death via acid sphingomyelinase (ASMase)-induced ceramide production, resulting in biologically significant enhancement of tumor responses. To further augment or solicit similar effects at low radiation doses, we used genetic and chemical approaches to evaluate mechano-acoustic activation of the ASMase-ceramide pathway by ultrasound-stimulated microbubbles (USMB). Methods: Experiments were carried out in wild-type and acid sphingomyelinase (asmase) knockout mice implanted with fibrosarcoma xenografts. A cohort of wild-type mice received the ASMase-ceramide pathway inhibitor sphingosine-1-phosphate (S1P). Mice were treated with varying radiation doses, with or without a priori USMB exposure at different microbubble concentrations. Treatment response was assessed with quantitative 3D Doppler ultrasound and immunohistochemistry at baseline, and at three, 24, and 72 hours after treatment, with three to five mice per treatment group at each time point. All statistical tests were two-sided. Results: Results confirmed an interaction between USMB and ionizing radiation at 24 hours (P < .001), with a decrease in tumor perfusion of up to 46.5% by three hours following radiation and USMB. This peaked at 24 hours, persisting for up to 72 hours, and was accompanied by extensive tumor cell death. In contrast, statistically nonsignificant and minimal tumor responses were noted in S1P-treated and asmase knockout mice for all treatments. Conclusions: This work is the first to confirm the involvement of the ASMase-ceramide pathway in mechanotransductive vascular targeting using USMB. Results also confirm that an acute vascular effect is driving this form of enhanced radiation response, and that it can be elicited at low radiation doses (<8-10 Gy) by a priori USMB exposure.