Abstract 3796: Exosomes enhance the radiation sensitivity via miR-6823-5p and modulate metastases in pancreatic cancer model

Introduction: Pancreatic cancer (PC) is believed to be a difficult disease because of its radio-resistance and metastases. Radiotherapy reported to modify tumor microenvironment (TME) and to affect PC progression. Exosomes containing such as microRNAs (miRNAs), messenger RNAs (mRNAs), and proteins of cells, play essential roles in cell-to-cell communications. However, characteristics and mechanisms for radiation responsive exosomes remain unclear. Here, we first report mechanisms of exosomes-mediated radiation response and regulation in PC metastasis with focusing on intra/intercellular communications via miRNA.

Methods: MIAPaCa-2 cells, human pancreatic carcinoma, was used. To isolate exosomes, cell culture media was ultracentrifuged at 100,000 x g for 90 min at 4°C. Exosomes derived from non-irradiated culture media was named ‘0 Gy-Exo’ and those from irradiated with 5 Gy culture media is called ‘5 Gy-Exo’. Exosome sizes and features were evaluated by transmission electron microscopy (TEM). Intracellular reactive oxygen species (ROS) levels induced by exosomes and by X-ray irradiation were evaluated by the C-H2DCF dye staining. To detect DNA damage, cells were fixed and stained by γ-H2AX antibody. The expression of superoxide dismutase 1 (SOD1) was evaluated by using immunoblots. Total RNA was extracted from 0 Gy-Exo and 5 Gy-Exo, and then comprehensive miRNA expression analysis was performed to analyze 2,565 human miRNA sequences. The Gene Expression Omnibus database (GSE163133) and the TargetScan were used for specific miRNAs identification. Living MIAPaCa-2 cells in the presence or absence of those exosomes were injected in the spleen of Balb/c nude mice to establish liver metastatic models. Eight weeks after the injection, mice were sacrificed, and then the spleen and the liver were harvested as a whole organ. H-E staining and immunohisitochemical analyses using S100A4 and SMAD4 antibodies were performed to detect liver metastases.

Results: Isolated exosomes were shaped in the form of closed, round vesicles with a diameter of 10~100 nm. Intracellular ROS levels and the numbers of γ-H2AX foci in the cells with 5 Gy-Exo were significantly increased compared to those the control (without adding exosomes, p<0.01). Intracellular SOD1 expression in the cells with the 5 Gy-Exo was decreased compared with that in the control. The miR-6823-5p was identified to have a complementary base sequence to SOD1. The average occupied proportions with MIAPaCa-2 cells in the liver was modulated according to those exosomes. The SMAD4 expression was highly observed in the liver and the spleen suggesting that the SMAD4 could be a useful marker of liver metastases.

Conclusion: Exosomes increased radiation sensitivity through increase of intracellular ROS levels via exosomal miRNAs and also could affect liver metastases in pancreatic cancer models.

Citation Format: Ai Nakaoka, Makiko Nakahana, Sachiko Inubushi, Yasuyuki Shimizu, Kazuma Iwashita, Naritoshi Mukumoto, Kana Kobayashi, Takeaki Ishihara, Daisuke Miyawaki, Ryohei Sasaki. Exosomes enhance the radiation sensitivity via miR-6823-5p and modulate metastases in pancreatic cancer model. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3796.

Abstract 4244: Black soybean seed coat extract suppress intestinal tumorigenesis in APCmin mice

Background: Colorectal cancer (CRC) is a major cause of cancer-related deaths in Japan and worldwide. Since CRC has been reported to have close relationship with diet, it seems significant to identify dietary constituents that might suppress occurrence of CRC. Recently, an epidemiological investigation for cancer incidence in Japan revealed that consumptions of black soybeans seem to reduce incidence of several cancers, especially colorectal cancer. Black soybeans coat extract (BE) is known to contain rich procyanidins which have many beneficial physiological activities such as anticancer effects. Therefore, we hypothesized that BE may have inhibitory effects to intestinal tumorigenesis and investigated using APCmin/+ mice models.

Materials and Methods: APCmin/+ male mice in the C57BL/6 genetic background were obtained from Jackson Laboratories. APCmin/+ genotypes of each mouse were confirmed by polymerase chain reaction analysis (PCR) using DNA extracted from the tip of mouse tails. Mice were weighed weekly once and monitored regularly for any signs of weight loss. APC min/+ mice at 4 weeks of age were randomly divided into three groups with 5 mice, and fed by either AIN-76A diet, AIN-76A diet containing 0.05% or 0.05% BE for 8 weeks. At 12 weeks of age, intestines were removed from each mouse and then sliced longitudinally. The small intestine was cut into three equally parts: proximal, middle, and distal. Numbers and sizes of intestinal polyps in each portion were evaluated under Video-Zoom-microscope XV-440. Intestinal polyps were categorized by size into 1-2 mm, 2-3 mm and >3 mm. Other parts of the intestines were placed in 10% phosphate-buffered formalin for histopathology and immunohistochemical (PCNA, β-catenin, and MUC2) analyses.

Results: Numbers of polyps in mice fed with containing 0.05% or 0.5% BE diet were significantly smaller than in mice fed without BE (P < 0.05). As for size of polyps, the number of polyps of 1 to 3 mm in size was decreased in mice with BE, however, there were no significant difference for numbers of polyps more than 3 mm in size regarding diets with or without BE. With 0.05% BE diet, reduction rates for occurrence of polyps were 81% for proximal, 48% for middle, and 47% for distal positions, while in with 0.5% BE diet, those reduction rates were 71% for proximal, 59% for middle, and 58% for distal positions, respectively. From these results, the BE, either 0.05% or 0.05% concentration, showed inhibitory effects for tumorigeneses in the small intestine of APC min/+ mice. In histological analyses, the BE was induced higher expression of MUC2-positive cells in normal intestinal lesions and lower expression of β-catenin in tumor sites

Conclusions: The BE showed inhibitory effects in occurrence and growth of intestinal polyps in APCmin/+ mice models. With further evaluation of mechanisms, the BE could be a promising nutrition for prevention of CRC in human.

Citation Format: Yasuyuki Shimizu, Shunta Hirano, Yoko Yamashita, Tsuyoshi Fukumoto, Naritoshi Mukumoto, Ai Nakaoka, Namiko Hoshi, Takeaki Ishihara, Daisuke Miyawaki, Ashida Hitoshi, Ryohei Sasaki. Black soybean seed coat extract suppress intestinal tumorigenesis in APCmin mice. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4244.

Exosome-mediated radiosensitizing effect on neighboring cancer cells via increase in intracellular levels of reactive oxygen species

The precise mechanism of intercellular communication between cancer cells following radiation exposure is unclear. Exosomes are membrane‑enclosed small vesicles comprising lipid bilayers and are mediators of intercellular communication that transport a variety of intracellular components, including microRNAs (miRNAs or miRs). The present study aimed to identify novel roles of exosomes released from irradiated cells to neighboring cancer cells. In order to confirm the presence of exosomes in the human pancreatic cancer cell line MIAPaCa‑2, ultracentrifugation was performed followed by transmission electron microscopy and nanoparticle tracking analysis (NanoSight) using the exosome‑specific surface markers CD9 and CD63. Subsequent endocytosis of exosomes was confirmed by fluorescent microscopy. Cell survival following irradiation and the addition of exosomes was evaluated by colony forming assay. Expression levels of miRNAs in exosomes were then quantified by microarray analysis, while protein expression levels of Cu/Zn‑ and Mn‑superoxide dismutase (SOD1 and 2, respectively) enzymes in MIAPaCa‑2 cells were evaluated by western blotting. Results showed that the uptake of irradiated exosomes was significantly higher than that of non‑irradiated exosomes. Notably, irradiated exosomes induced higher intracellular levels of reactive oxygen species (ROS) and a higher frequency of DNA damage in MIAPaCa‑2 cells, as determined by fluorescent microscopy and immunocytochemistry, respectively. Moreover, six up‑ and five downregulated miRNAs were identified in 5 and 8 Gy‑irradiated cells using miRNA microarray analyses. Further analysis using miRNA mimics and reverse transcription‑quantitative PCR identified miR‑6823‑5p as a potential candidate to inhibit SOD1, leading to increased intracellular ROS levels and DNA damage. To the best of our knowledge, the present study is the first to demonstrate that irradiated exosomes enhance the radiation effect via increasing intracellular ROS levels in cancer cells. This contributes to improved understanding of the bystander effect of neighboring cancer cells.

Elucidation of gastrointestinal dysfunction in response to irradiation using metabolomics

Gastrointestinal toxicity is frequently observed secondary to accidental or therapeutic radiation exposure. However, the variation in the intestinal metabolites after abdominal radiation exposure remains ambiguous. In the present study, C57BL/6 mice were exposed to 0, 2, and 20 Gy irradiation dose. The Head and chest of each mouse were covered with a lead shield before x-ray irradiation. 24 h post-irradiation treatment, intestinal tissue of each mouse was excised and prepared for metabolites measurement using gas chromatography-mass spectrometry (GC-MS). Our comprehensive analysis of metabolites in the intestinal tissues detected 44 metabolites after irradiation, including amino acids, carbohydrates, organic acids, and sugars. Amino acid levels in the intestinal tissue gradually rose, dependent on the radiation dose, perhaps as an indication of oxidative stress. Our findings raise the possibility that amino acid metabolism may be a potential target for the development of treatments to alleviate or mitigate the harmful effects of oxidative stress-related gastrointestinal toxicity due to radiation exposure.

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Gastrointestinal damage frequently results from radiation exposure.

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We analyzed the metabolic profile after local irradiation to the intestine.

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Amino acid levels in the intestinal tissue rose dependent on the radiation dose.

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Amino acid metabolism may be a good target for future therapies.

Novel artifact-robust and highly visible zinc solid fiducial marker for kilovoltage x-ray image-guided radiation therapy

PURPOSE

To develop a novel biocompatible solid fiducial marker that prevents radiopaque imaging artifacts and also maintains high imaging contrast for kilovoltage x-ray image-guided radiation therapy.

METHODS

The fiducial marker was made of pure zinc. An in-house water-equivalent phantom was designed to evaluate artifacts and visibility under various simulated treatment scenarios. Image artifacts were quantitatively assessed in terms of the metal artifact index (MAI) on kilovoltage computed tomography (CT) and cone-beam CT (CBCT) scans. Marker visibility was evaluated on two types of kilovoltage planar x-ray images in terms of the contrast-to-background ratio (CBR). Comparisons with a conventional gold fiducial marker were conducted.

RESULTS

The use of zinc rather than a gold marker mitigates imaging artifacts. The MAI near the zinc marker decreased by 76, 79, and 77 % in CT, and by 77 (81), 74 (80), and 79 (85) % in CBCT full-fan (half-fan) scans, when using one-, two-, and three-marker phantom settings, respectively. The high-contrast part of the zinc marker exhibited CBRs above 2.00 for 28/32 exposures under four (lung, tissue, low-density bone, and high-density bone) different simulation scenarios, making its visibility comparable to that of the gold marker (30/32 exposures with CBRs > 2.00).

CONCLUSIONS

We developed a biocompatible, artifact-robust, and highly visible solid zinc fiducial marker. Although further evaluation is needed in clinical settings, our findings suggest its feasibility and benefits for kilovoltage x-ray image-guided radiation therapy.

A Comparative Assessment of Mechanisms and Effectiveness of Radiosensitization by Titanium Peroxide and Gold Nanoparticles

The development of potentially safe radiosensitizing agents is essential to enhance the treatment outcomes of radioresistant cancers. The titanium peroxide nanoparticle (TiOxNP) was originally produced using the titanium dioxide nanoparticle, and it showed excellent reactive oxygen species (ROS) generation in response to ionizing radiation. Surface coating the TiOxNPs with polyacrylic acid (PAA) showed low toxicity to the living body and excellent radiosensitizing effect on cancer cells. Herein, we evaluated the mechanism of radiosensitization by PAA-TiOxNPs in comparison with gold nanoparticles (AuNPs) which represent high-atomic-number nanoparticles that show a radiosensitizing effect through the emission of secondary electrons. The anticancer effects of both nanoparticles were compared by induction of apoptosis, colony-forming assay, and the inhibition of tumor growth. PAA-TiOxNPs showed a significantly more radiosensitizing effect than that of AuNPs. A comparison of the types and amounts of ROS generated showed that hydrogen peroxide generation by PAA-TiOxNPs was the major factor that contributed to the nanoparticle radiosensitization. Importantly, PAA-TiOxNPs were generally nontoxic to healthy mice and caused no histological abnormalities in the liver, kidney, lung, and heart tissues.

Association between angiotensin converting enzyme gene polymorphism and clinical features in autosomal dominant polycystic kidney disease

We investigated the association between angiotensin converting enzyme (ACE) gene polymorphism and clinical manifestations in 47 patients with autosomal dominant polycystic kidney disease (ADPKD). One-hundred, age- and sex-matched subjects with non-ADPKD served as the controls. ACE gene polymorphism was analysed using a GeneAnp kit. Renal size was determined by abdominal CT scan, by adding the longitudinal axis of each kidney. Incidence of extrarenal complication was also examined. Out of 47 patients, 24 patients (51%) were II, 18 (38%) ID and 5 (11%) DD type. The frequencies of the I and D alleles as well as the distributions of ACE genotypes in ADPKD did not differ from those in controls. The number of patients undertaking renal replacement therapy was 11 in II (46%), 6 (33%) in ID and 2 (40%) in DD genotype, respectively, that was not significantly different among the groups. The mean age of the initiation of renal replacement therapy did not vary among the three genotypes. The slopes of 1/serum creatinine did not differ between II and ID genotypes, whose initial serum creatinine levels ranged from 1.5 to 2.5 mg/dl. Renal size, blood pressure, and extrarenal complications including liver cysts and cardiac valvular disease were unrelated to the ACE genotypes. The present data suggested the irrelevance of ACE gene polymorphism in clinical manifestations in patients with ADPKD.

Effect of glucagon infusion on renal hemodynamics in normal subjects and patients with chronic glomerulonephritis

The effect of glucagon infusion (15-20 ng/kg/min, for one hour) on renal hemodynamics was examined in normal subjects and in patients with chronic glomerulonephritis (CGN). In normal subjects, the glomerular filtration rate (GFR) was significantly increased by glucagon with a concomitant rise in effective renal plasma flow (ERPF) and filtration fraction (FF) (GFR/ERPF). In renal patients with a baseline GFR of above 90 ml/min/l/73 m2, GFR was significantly increased in response to glucagon, without a significant rise in ERPF. The patients whose baseline GFR ranged from 40-90 ml/min had no significant increase in GFR, while ERPF rose significantly. These results suggest that the renal hemodynamic response to glucagon infusion were modified by the level of baseline GFR in patients with chronic glomerulonephritis.

Environmental effects of natural radionuclides from coal-fired power plants

The assessment of the environmental effects of natural radionuclides contained in fly ash released from a coal-fired power plant was carried out and the following results were obtained. Mean concentrations of U, Th and K in 28 kinds of domestic and foreign coals were 1.0 ppm, 3.3 ppm and 2300 ppm, respectively. A good correlation between U and Th concentrations appears evident. Natural radionuclide concentrations of bottom and fly ashes were approximately equal in both ashes, and the values were the same as those calculated by concentration in coal divided by ash content. Release rates of 40K and radionuclides of each decay chain of U or Th were evaluated in the range of 2 to 40,000 pCi/sec for model coal-fired power plants of 1000 MW and 250 MW. The natural radionuclide concentration in air in a plume at the maximum concentration point was 5 X 10(-9) to 5 X 10(-3) pCi/m3, and these values were below 1/200 of those of natural origin.