Radiosensitivity Of Tumor Cells Research Articles

The p38/MK2 Pathway Functions as Chk1-Backup Downstream of ATM/ATR in G2-Checkpoint Activation in Cells Exposed to Ionizing Radiation

We have recently reported that in G2-phase cells (but not S-phase cells) sustaining low loads of DNA double-strand break (DSBs), ATM and ATR regulate the G2-checkpoint epistatically, with ATR at the output-node, interfacing with the cell cycle through Chk1. However, although inhibition of ATR nearly completely abrogated the checkpoint, inhibition of Chk1 using UCN-01 generated only partial responses. This suggested that additional kinases downstream of ATR were involved in the transmission of the signal to the cell cycle engine. Additionally, the broad spectrum of kinases inhibited by UCN-01 pointed to uncertainties in the interpretation that warranted further investigations. Here, we show that more specific Chk1 inhibitors exert an even weaker effect on G2-checkpoint, as compared to ATR inhibitors and UCN-01, and identify the MAPK p38α and its downstream target MK2 as checkpoint effectors operating as backup to Chk1. These observations further expand the spectrum of p38/MK2 signaling to G2-checkpoint activation, extend similar studies in cells exposed to other DNA damaging agents and consolidate a role of p38/MK2 as a backup kinase module, adding to similar backup functions exerted in p53 deficient cells. The results extend the spectrum of actionable strategies and targets in current efforts to enhance the radiosensitivity in tumor cells.

Biological modeling of gadolinium-based nanoparticles radio-enhancement for kilovoltage photons: a Monte Carlo study

BackgroundGadolinium-based nanoparticles (GdNPs) are clinically used agents to increase the radiosensitivity of tumor cells. However, studies on the mechanisms and biological modeling of GdNP radio-enhancement are still preliminary. This study aims to investigate the mechanism of radio-enhancement of GdNPs for kilovoltage photons using Monte Carlo (MC) simulations, and to establish local effect model (LEM)-based biological model of GdNP radiosensitization.MethodsThe spectrum and yield of secondary electrons and dose enhancement around a single GdNP and clustered GdNPs were calculated in a water cube phantom by MC track-structure simulations using TOPAS code. We constructed a partial shell-like cell geometry model of pancreatic cancer cell based on transmission electron microscope (TEM) observations. LEM-based biological modeling of GdNP radiosensitization was established based on the MC-calculated nano-scale dose distributions in the cell model to predict the cell surviving fractions after irradiation.ResultsThe yield of secondary electrons for GdNP was 0.16% of the yield for gold nanoparticle (GNP), whereas the average electron energy was 12% higher. The majority of the dose enhancement came from the contribution of Auger electrons. GdNP clusters had a larger range and extent of dose enhancement than single GdNPs, although GdNP clustering reduced radial dose per interacting photon significantly. For the dose range between 0 and 8 Gy, the surviving fraction predicted using LEM-based biological model laid within one standard deviation of the published experimental results, and the deviations between them were all within 25%.ConclusionsThe mechanism of radio-enhancement of GdNPs for kilovoltage photons was investigated using MC simulations. The prediction results of the established LEM-based biological model for GdNP radiosensitization showed good agreement with published experimental results, although the deviation of simulation parameters can lead to large disparity in the results. To our knowledge, this was the first LEM-based biological model for GdNP radiosensitization.

PO-2217 Supplemented gut bacteria effect the viability and radiosensitivity of bladder tumour cells in vitro

PO-2217 Supplemented gut bacteria effect the viability and radiosensitivity of bladder tumour cells in vitro

Functionalized Hybrid Iron Oxide–Gold Nanoparticles Targeting Membrane Hsp70 Radiosensitize Triple-Negative Breast Cancer Cells by ROS-Mediated Apoptosis

Triple-negative breast cancer (TNBC) a highly aggressive tumor entity with an unfavorable prognosis, is treated by multimodal therapies, including ionizing radiation (IR). Radiation-resistant tumor cells, as well as induced normal tissue toxicity, contribute to the poor clinical outcome of the disease. In this study, we investigated the potential of novel hybrid iron oxide (Fe3O4)-gold (Au) nanoparticles (FeAuNPs) functionalized with the heat shock protein 70 (Hsp70) tumor-penetrating peptide (TPP) and coupled via a PEG4 linker (TPP-PEG4-FeAuNPs) to improve tumor targeting and uptake of NPs and to break radioresistance in TNBC cell lines 4T1 and MDA-MB-231. Hsp70 is overexpressed in the cytosol and abundantly presented on the cell membrane (mHsp70) of highly aggressive tumor cells, including TNBCs, but not on corresponding normal cells, thus providing a tumor-specific target. The Fe3O4 core of the NPs can serve as a contrast agent enabling magnetic resonance imaging (MRI) of the tumor, and the nanogold shell radiosensitizes tumor cells by the release of secondary electrons (Auger electrons) upon X-ray irradiation. We demonstrated that the accumulation of TPP-PEG4-FeAuNPs into mHsp70-positive TNBC cells was superior to that of non-conjugated FeAuNPs and FeAuNPs functionalized with a non-specific, scrambled peptide (NGL). After a 24 h co-incubation period of 4T1 and MDA-MB-231 cells with TPP-PEG4-FeAuNPs, but not with control hybrid NPs, ionizing irradiation (IR) causes a cell cycle arrest at G2/M and induces DNA double-strand breaks, thus triggering apoptotic cell death. Since the radiosensitizing effect was completely abolished in the presence of the ROS inhibitor N-acetyl-L-cysteine (NAC), we assume that the TPP-PEG4-FeAuNP-induced apoptosis is mediated via an increased production of ROS.

LncRNA ANRIL promotes HR repair through regulating PARP1 expression by sponging miR-7-5p in lung cancer

BackgroundRadiotherapy is an important treatment for lung cancer, mainly by triggering DNA double-strand breaks to induce cell death. Blocking DNA damage repair can increase the radiosensitivity of tumor cells. Recent studies have identified long noncoding RNAs as key regulators in DNA damage repair. The lncRNA ANRIL was previously shown to be involved in homologous recombination (HR) repair, but its specific mechanism has not been fully elucidated.MethodsThe downstream interacting miRNAs of ANRIL were predicted according to miRanda software. Fluorescence quantitative PCR was used to detect the expression levels of ANRIL and candidate miRNAs. Clone formation experiment and cell viability assays detect cell viability after ionizing radiation. Apoptosis assay was used to detect the apoptosis of cells after 8 h of ionizing radiation. Western blot analysis and immunofluorescence assays verified the protein expression levels of the downstream target molecule PARP1 of miR-7-5p and key molecules in the HR pathway. Fluorescent reporter gene experiments were used to verify the interaction between ANRIL and miR-7-5p and between miR-7-5p and PARP1.ResultsBioinformatics analysis and qPCR validation suggested that miR-7-5p might be a downstream molecule of ANRIL. The expression of miR-7-5p was up-regulated after knockdown of ANRIL, and the expression of miR-7-5p was down-regulated after overexpression of ANRIL. Meanwhile, there was a negative correlation between ANRIL and miR-7-5p expression changes before and after ionizing radiation. The luciferase reporter gene assay confirmed the existence of ANRIL binding site with miR-7-5p, and found that transfection of miR-7-5p inhibitor can reduce the radiation sensitivity of ANRIL-KD cells. A downstream target molecule of miR-7-5p related to HR repair, PARP1, was screened through website prediction. Subsequently, it was confirmed by Western blot and luciferase reporter assays that miR-7-5p could down-regulate the expression of PARP1, and there was a miR-7-5p binding site on the 3'UTR of PARP1 mRNA. This suggests that ANRIL may act as a competitive endogenous RNA to bind miR-7-5p and upregulate the expression of PARP1. Western blot and immunofluorescence staining were used to detect the expression changes of HR repair factors in ANRIL-KD cells after ionizing radiation, and it was found that knockdown of ANRIL can inhibit the expression of PARP1, BRCA1 and Rad51, hinder radiation-induced HR repair, and eventually result in resensitizing ANRIL-KD cells to ionizing radiation.ConclusionsOur findings provide evidence that ANRIL targets the miR-7-5p/PARP1 axis to exert its regulatory effect on HR repair, suggesting that altering ANRIL expression may be a promising strategy to overcome radiation resistance.

LncRNA DGCR5 Silencing Enhances the Radio-Sensitivity of Human Esophageal Squamous Cell Carcinoma via Negatively Regulating the Warburg Effect.

Recently, long noncoding RNAs (lncRNAs) and the Warburg effect have been reported to play important roles in the radio-sensitivity of tumor cells. Survival correlates with pathologic responses to chemoradiotherapy and improving responses to radiation may translate into improved survival. This study aims to examine the effects and mechanisms of lncRNA DGCR5 and the Warburg effect on ESCC cell radiosensitivity. Levels of DGCR5, miR-195 and hexokinase 2 (HK2) expression in ESCC tissues and cells were determined and their clinical significance was analyzed. TE-1 and KYSE150 cells received a 6 Gy dose of X-ray radiation and their survival, proliferation and apoptosis were evaluated using colony formation assays, CCK-8 assays, and flow cytometry, respectively. Lactic acid production and glucose consumption were also examined in both cell types. Finally, the expression of apoptotic proteins was assessed using Western blotting. Analysis revealed that DGCR5 and HK2 were overexpressed in ESCC, while miR-195 was under expressed. Moreover, it was demonstrated that down-regulation of DGCR5 inhibited cell proliferation and promoted apoptosis, resulting in increased radiosensitivity by inhibition of the Warburg Effect. Conversely, overexpression of DGCR5 exhibited an opposite phenomenon in vitro. When investigating the mechanism, we identified that miR-195 was predicted to be a direct downstream target of DGCR5. Meanwhile, HK2 was predicted to be a direct downstream target of miR-195. Dual-luciferase reporter assays verified the direct interaction between these molecules. Finally, in vivo experiments were utilized to validate that knockdown of DGCR5 suppressed the Warburg effect via targeting of the miR-195/HK2 axis to increase the radiosensitivity of ESCC. Our study reveals that down-regulation of DGCR5 resulted in inhibition of the Warburg effect through interaction with the miR-195/HK2 axis increasing ESCC cell apoptosis after irradiation, thus enhancing cell radiosensitivity.

Gut microbiota: A novel and potential target for radioimmunotherapy in colorectal cancer.

Colorectal cancer (CRC) is one of the most common cancers, with a high mortality rate, and is a major burden on human health worldwide. Gut microbiota regulate human immunity and metabolism through producing numerous metabolites, which act as signaling molecules and substrates for metabolic reactions in various biological processes. The importance of host-gut microbiota interactions in immunometabolic mechanisms in CRC is increasingly recognized, and interest in modulating the microbiota to improve patient's response to therapy has been raising. However, the specific mechanisms by which gut microbiota interact with immunotherapy and radiotherapy remain incongruent. Here we review recent advances and discuss the feasibility of gut microbiota as a regulatory target to enhance the immunogenicity of CRC, improve the radiosensitivity of colorectal tumor cells and ameliorate complications such as radiotoxicity. Currently, great breakthroughs in the treatment of non-small cell lung cancer and others have been achieved by radioimmunotherapy, but radioimmunotherapy alone has not been effective in CRC patients. By summarizing the recent preclinical and clinical evidence and considering regulatory roles played by microflora in the gut, such as anti-tumor immunity, we discuss the potential of targeting gut microbiota to enhance the efficacy of radioimmunotherapy in CRC and expect this review can provide references and fresh ideas for the clinical application of this novel strategy.

Small-Molecule Polθ Inhibitors Provide Safe and Effective Tumor Radiosensitization in Preclinical Models.

DNA polymerase theta (Polθ, encoded by the POLQ gene) is a DNA repair enzyme critical for microhomology mediated end joining (MMEJ). Polθ has limited expression in normal tissues but is frequently overexpressed in cancer cells and, therefore, represents an ideal target for tumor-specific radiosensitization. In this study we evaluate whether targeting Polθ with novel small-molecule inhibitors is a feasible strategy to improve the efficacy of radiotherapy. We characterized the response to Polθ inhibition in combination with ionizing radiation in different cancer cell models in vitro and in vivo. Here, we show that ART558 and ART899, two novel and specific allosteric inhibitors of the Polθ DNA polymerase domain, potently radiosensitize tumor cells, particularly when combined with fractionated radiation. Importantly, noncancerous cells were not radiosensitized by Polθ inhibition. Mechanistically, we show that the radiosensitization caused by Polθ inhibition is most effective in replicating cells and is due to impaired DNA damage repair. We also show that radiosensitization is still effective under hypoxia, suggesting that these inhibitors may help overcome hypoxia-induced radioresistance. In addition, we describe for the first time ART899 and characterize it as a potent and specific Polθ inhibitor with improved metabolic stability. In vivo, the combination of Polθ inhibition using ART899 with fractionated radiation is well tolerated and results in a significant reduction in tumor growth compared with radiation alone. These results pave the way for future clinical trials of Polθ inhibitors in combination with radiotherapy.

Targeting the STAT5A/IDO1 axis overcomes radioresistance and reverses the immunosuppressive tumor microenvironment in NSCLC.

As a metabolic mediator of antitumor immunity, indoleamine‑2,3‑dioxygenase 1 (IDO1) is upregulated in various types of cancer; however, the regulatory mechanism and clinical significance of IDO1 in non‑small cell lung cancer (NSCLC) radiotherapy (RT) remain unclear. The present study investigated the role of IDO1 in the NSCLC microenvironment. MTT assay, immunofluorescence, apoptosis analysis, cell cycle analysis, and C57BL/6 and BALB/c nude mouse tumor models were utilized to evaluate the roles of the STAT5A/IDO1/kynurenine axis in radioresistance and in the immune microenvironment of NSCLC. Protein expression levels were evaluated by western blotting, immunofluorescence and immunohistochemistry. Flow cytometry was performed to assess the status of CD8+ T lymphocytes, regulatory T cells (Tregs) and immune‑related inflammatory factors in C57BL/6 mice. Notably, IDO1 and STAT5A were positively associated with the immune microenvironment. RT treatment significantly promoted the expression levels of IDO1. IDO1 knockdown markedly enhanced the radiosensitivity of lung tumor cells and the anti‑apoptotic properties of T lymphocytes. It was demonstrated that STAT5A knockdown suppressed T‑cell apoptosis by inhibiting IDO1 enzyme function. Finally, invivo experiments showed that STAT5A knockdown combined with RT was associated with greater numbers of CD8+ T cells and fewer Tregs. Results from the present study indicated that targeting the STAT5A/IDO1 axis may reshape the immune microenvironment and promote the efficacy of RT in NSCLC treatment. The present study may provide a theoretical foundation for more efficient use of immunotherapy regimens in NSCLC treatment.

Targeting PI3K/Akt signaling in prostate cancer therapy.

Urological cancers have obtained much attention in recent years due to their mortality and morbidity. The most common and malignant tumor of urological cancers is prostate cancer that imposes high socioeconomic costs on public life and androgen-deprivation therapy, surgery, and combination of chemotherapy and radiotherapy are employed in its treatment. PI3K/Akt signaling is an oncogenic pathway responsible for migration, proliferation and drug resistance in various cancers. In the present review, the role of PI3K/Akt signaling in prostate cancer progression is highlighted. The activation of PI3K/Akt signaling occurs in prostate cancer, while PTEN as inhibitor of PI3K/Akt shows down-regulation. Stimulation of PI3K/Akt signaling promotes survival of prostate tumor cells and prevents apoptosis. The cell cycle progression and proliferation rate of prostate tumor cells increase by PI3K/Akt signaling induction. PI3K/Akt signaling stimulates EMT and enhances metastasis of prostate tumor cells. Silencing PI3K/Akt signaling impairs growth and metastasis of prostate tumor cells. Activation of PI3K/Akt signaling mediates drug resistance and reduces radio-sensitivity of prostate tumor cells. Anti-tumor compounds suppress PI3K/Akt signaling in impairing prostate tumor progression. Furthermore, upstream regulators such as miRNAs, lncRNAs and circRNAs regulate PI3K/Akt signaling and it has clinical implications for prostate cancer patients.

Sinomenine Hydrochloride Promotes TSHR-Dependent Redifferentiation in Papillary Thyroid Cancer.

Radioactive iodine (RAI) plays an important role in the diagnosis and treatment of papillary thyroid cancer (PTC). The curative effects of RAI therapy are not only related to radiosensitivity but also closely related to the accumulation of radionuclides in the lesion in PTC. Sinomenine hydrochloride (SH) can suppress tumor growth and increase radiosensitivity in several tumor cells, including PTC. The aim of this research was to investigate the therapeutic potential of SH on PTC cell redifferentiation. In this study, we treated BCPAP and TPC-1 cells with SH and tested the expression of thyroid differentiation-related genes. RAI uptake caused by SH-pretreatment was also evaluated. The results indicate that 4 mM SH significantly inhibited proliferation and increased the expression of the thyroid iodine-handling gene compared with the control group (p < 0.005), including the sodium/iodide symporter (NIS). Furthermore, SH also upregulated the membrane localization of NIS and RAI uptake. We further verified that upregulation of NIS was associated with the activation of the thyroid-stimulating hormone receptor (TSHR)/cyclic adenosine monophosphate (cAMP) signaling pathway. In conclusion, SH can inhibit proliferation, induce apoptosis, promote redifferentiation, and then increase the efficacy of RAI therapy in PTC cells. Thus, our results suggest that SH could be useful as an adjuvant therapy in combination with RAI therapy in PTC.

Dll1-Mediated Notch Signaling Drives Tumor Cell Cross-talk with Cancer-Associated Fibroblasts to Promote Radioresistance in Breast Cancer.

Dll1+ breast cancer cells activate Notch signaling in cancer-associated fibroblasts that increases Wnt ligand secretion and leads to β-catenin-driven radioresistance and metastasis, opening new therapeutic avenues for breast cancer.

Anlotinib plus chemoradiotherapy in the treatment for FIGO stage IB3 and IIB-IVA cervical cancer: A prospective single-arm, single-center, exploratory phase II trial (299)

<b>Objectives:</b> Cervical carcinoma is the fourth leading cause of cancer-related death among women worldwide. Previous randomized clinical trials showed a 30% to 50% decrease in risk of death in locally advanced cervical cancer (LACC) with the addition of concurrent platinum-based chemoradiotherapy when compared with radiotherapy alone. Mechanisms to account for improved efficacy are thought to include direct cytotoxicity, radiosensitization of tumor cells, and control of subclinical metastases. Anlotinib is an oral multi-targeted tyrosine kinase inhibitor (TKI) that strongly inhibits VEGFR, PDGFR, FGFR, and c-kit. Anlotinib synergizes with radiation and cisplatin, as shown in preclinical and clinical studies. This phase II study aims to evaluate the efficacy and safety of adding anlotinib to concurrent chemoradiotherapy in FIGO stage IB3 and IIB-IVA cervical cancer. <b>Methods:</b> Inclusion criteria include treatment-naive histologically confirmed FIGO stage IB3 to IVA cervical cancer with at least one measurable lesion and ECOG performance score 0-2 within the age range of 18 to 75 years. Abundant organ functions are required, with no contraindication to anlotinib or chemoradiation present. Patients will be treated with oral anlotinib (12 mg qd, d1-14; 21 days per cycle; total 3 cycles) and X-ray external-beam radiotherapy (total 45Gy-50Gy in 25-28 fraction), followed by brachytherapy (6Gy/5 fractions or 7Gy/4 fractions) with concurrent cisplatin (40 mg/m2 weekly for 5-6 weeks). The primary endpoint is the progression-free survival (PFS) rate at three years. The secondary endpoints include overall response rate (ORR), disease control rate (DCR), overall survival (OS), and quality of Life (QOL). Safety will be evaluated in all patients who receive study drugs according to the treatment received (safety population) by recording clinical adverse events (AEs) using National Cancer Institute Common. The sample size calculation of 47 patients provides 80% power to detect a difference in survival at the two-sided 5% significance level using the log-rank test; considering a 10% reduction, a total of 53 samples are required. This study is currently open, and 23 patients have been enrolled. The estimated primary completion date is December 1, 2024, and the estimated study completion date is October 31, 2025.

Ionizing Radiation Triggers the Antitumor Immunity by Inducing Gasdermin E-Mediated Pyroptosis in Tumor Cells

To understand pyroptosis induced by ionizing radiation and its implications for radiation therapy, we explored the involved factors, possible mechanisms of radiation-induced pyroptosis and consequent antitumor immunity. The occurrence of pyroptosis was assessed by cell morphology, lactate dehydrogenase release, Annexin V/PI staining and the cleavage of Gasdermin E (GSDME). Cell radiosensitivity was tested with MTT and colony survival assays. Xenograft tumor volume, Ki-67, CD8+ lymphocytes, and ELISA were used to evaluate the effect of GSDME on tumor suppression after irradiation. Irradiation induced pyroptosis in GSDME high-expressing tumor cell lines covering lung, liver, breast, and glioma cancers. Cleavage of GSDME occurred in a dose- and time-dependent manner after irradiation, and pyroptosis could be induced by various kinds of irradiation. The combination of chemotherapy drugs for DNA damage (cisplatin or etoposide) or demethylation (decitabine or azacytidine) and irradiation significantly enhanced the occurrence of pyroptosis. Moreover, we revealed that the Caspase 9/Caspase 3/GSDME pathway was involved in irradiation-induced pyroptosis. Notably, enhanced tumor suppression was observed in Balb/c mice bearing GSDME-overexpressing 4T1 tumors compared with those bearing vector tumors for the promotion of antitumor immunity, which was manifested as distinctly elevated levels of cytotoxic T lymphocytes and release of the related cytokines rather than the direct effect of pyroptosis on tumor cell radiosensitivity. As an immunogenic cell death caused by radiation, pyroptosis promotes antitumor immunity after irradiation. Our findings may provide new insights to improve the efficacy of tumor radiation therapy.

Stereotactic radiosurgery of radioresistant glioblastomas. The ways of overcoming radioresistance of hypoxic tumors

Background. Taking into account high degree of resistance of glioblastoma to radiation therapy, and also low overall survival rates of patients, it is necessary to develop improved methods of treating this pathology, in particular, complex combined treatment with radiation therapy and radiosensitizers.&#x0D; Purpose – to assess the effectiveness of radiosensitization of hypoxic tumors in radiosurgical treatment of glioblastomas; to increase non-recurrent and overall survival rate of patients. Materials and methods. Stereotactic radiosurgery (SRS) of glioblastoma was performed in 106 patients (average age – 53 years), 66 males (62,26%) and 40 females (37,73%). The average dose was 18 Gy in a single-fraction SRS, and 32 Gy (7 Gy per fraction) in multi-fraction SRS. The average volume tumor was 29 cm3 . The treatment group consisted of 66 patients who underwent SRS with radiosensitization. 40 patients made up the control group and underwent SRS without radiosensitization.&#x0D; Results. Median overall survival (MOS) was 20 months in the group with radiosensitization, whereas in the control group it was 12 months. 10-month recurrence-free period after radiosurgery was observed in 95,4% of the patients of the group with radiosensitization and in 70,6% of the patients of the control group. MOS after SRS was similar between the patients with wild-type IDH tumors and patients with tumors with IDH mutation (10,0 months and 11,0 months respectively), and also between the patients with MGMT-methylated tumors and patients with MGMT-nonmethylated tumors (11,2 and 10,2 months respectively). Among all the treated patients, in 20 of them (16,6%) side radiation effects after SRS were observed, and in 9 patients (7,5%) radiation necrosis developed in 3 to 16 months after SRS. The signs of moderate toxicity in the form of vomiting were observed in 6,6% of the patients of the subgroup with metronidazole. There were no signs of toxicity in the subgroup with nimorazole.&#x0D; Conclusions. Radiosensitization improves rates of overall survival by 53,3% and recurrence-free survival by 24,8 % in performing SRS of hypoxic radioresistant glioblastomas. Nimorazole and metronidazole are powerful radiosensitizers which increase radiosensitivity of tumor cells through enhancing oxygen saturation of hypoxic cells. In order to determine indications for performing SRS with radiosensitization and periods for performing an SRS session we must take into consideration the result of an oxygen test (level of oxygen saturation of the tumor), the peak of signal intensity in the zone of active tumor growth and the peak of saturation of the whole tumor volume.

Inhibition of the Translation Initiation Factor eIF4A Enhances Tumor Cell Radiosensitivity.

A fundamental component of cellular radioresponse is the translational control of gene expression. Because a critical regulator of translational control is the eukaryotic translation initiation factor 4F (eIF4F) cap binding complex, we investigated whether eIF4A, the RNA helicase component of eIF4F, can serve as a target for radiosensitization. Knockdown of eIF4A using siRNA reduced translational efficiency, as determined from polysome profiles, and enhanced tumor cell radiosensitivity as determined by clonogenic survival. The increased radiosensitivity was accompanied by a delayed dispersion of radiation-induced γH2AX foci, suggestive of an inhibition of DNA double-strand break repair. Studies were then extended to (-)-SDS-1-021, a pharmacologic inhibitor of eIF4A. Treatment of cells with the rocaglate (-)-SDS-1-021 resulted in a decrease in translational efficiency as well as protein synthesis. (-)-SDS-1-021 treatment also enhanced the radiosensitivity of tumor cell lines. This (-)-SDS-1-021-induced radiosensitization was accompanied by a delay in radiation-induced γH2AX foci dispersal, consistent with a causative role for the inhibition of double-strand break repair. In contrast, although (-)-SDS-1-021 inhibited translation and protein synthesis in a normal fibroblast cell line, it had no effect on radiosensitivity of normal cells. Subcutaneous xenografts were then used to evaluate the in vivo response to (-)-SDS-1-021 and radiation. Treatment of mice bearing subcutaneous xenografts with (-)-SDS-1-021 decreased tumor translational efficiency as determined by polysome profiles. Although (-)-SDS-1-021 treatment alone had no effect on tumor growth, it significantly enhanced the radiation-induced growth delay. These results suggest that eIF4A is a tumor-selective target for radiosensitization.

Abstract 6060: Can the gut microbiota both radiosensitize tumors and spare normal tissue toxicity

Abstract Background: New non-toxic radiosensitizers are needed in the treatment of muscle-invasive bladder cancer because elderly patients are vulnerable to chemotherapy-related toxicity of currently available radiosensitizers. Our previous study showed that high fiber diets sensitized RT112 xenografts to ionizing radiation (IR) by modifying the gut microbiome and this phenotype was positively correlated with B.acidifaciens (BA) abundance. It is noted that gut microbiota can enhance anti-tumoral responses, so we hypothesise that gut microbiota including BA may radiosensitize tumors via secretion of metabolites and immunomodulation. Methods: UPPL1591 mouse bladder cancer cell line flank xenografts were implanted into C57BL/6 mice (an immune-competent setting) at the same time as starting low (0.2% cellulose) and high fiber (5% psyllium, 5% psyllium plus 10% resistant starch/10% inulin) diets for their lifetime (N=30). 16S rRNA sequencing, IC-MS, IHC and the Nanostring platform were used for gut microbiota, untargeted metabolomics, and local tumor immunity analyses. For normal tissue toxicity studies, mice received 10-14 Gy IR (N=84). We used an intestinal crypt assay and FACS analysis of spleen to assess acute normal effects in small intestine and systemic immunity. Cell viability, clonogenic assay and Western blotting were used to validate the cytotoxic and radiosensitizing effects of bacterial supernatants on RT112 human bladder cancer cells (N=3). Results: Psyllium plus either resistant starch (RS, p=0.007) or inulin (p&amp;lt;0.001) significantly decreased tumors size. Psyllium plus inulin raised inosine-producing bacteria (p&amp;lt;0.001) and faecal inosine levels (p&amp;lt;0.001) which has been shown to enhance immunotherapy efficacy. Increased systemic (p=0.189) and local (p=0.024) anti-tumoral T cell responses were observed in the psyllium plus inulin group. Furthermore, the two diets mitigated the radiation injury from 14 Gy in intestinal crypt assays (p=0.011) and increased systemic immunity, with higher populations of B (p=0.024), cytotoxic T (p=0.019) and helper T (p&amp;lt;0.001) cells. Psyllium plus RS or inulin significantly increased caecal size (p&amp;lt;0.001), implying higher fermentation levels. We previously found inulin can enhance the relative abundance of BA. The supernatants of co-cultures of BA and F.praunitzii (FP, butyrate-producer) conferred greater cytotoxity than BA alone (p&amp;lt;0.001) or co-cultures of Bifidobacterium and FP (p&amp;lt;0.001), and also increased histone acetylation levels. Bacterial supernatants of BA increased DNA damage with 5Gy IR (p&amp;lt;0.05) and radiosensitivity of bladder tumour cells (p=0.008 at 8Gy). Conclusions: B.acidifaciens is a potential radiosensitiser with enhanced efficacy in combination with butyrate-producing bacteria. Our in vivo experiments suggest a role for inosine and cytotoxic T cells generated by the gut microbiota in radiosensitisation of bladder tumors. Citation Format: Chee Kin Then, Salome Paillas, Xuedan Wang, Mariya Misheva, James McCullagh, Kevin R. Foster, Anne E. Kiltie. Can the gut microbiota both radiosensitize tumors and spare normal tissue toxicity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6060.

Abstract 2732: A mathematical model for optimization of combination therapy involving targeted radionuclide and CAR-T cell therapy

Abstract Background: Immunotherapy with chimeric antigen receptor - T (CAR-T) cells and targeted radionuclide therapy (TRT) are two highly promising therapies in cancer treatment. Often, these therapies show limited efficacy in complete eradication of cancer cells making the combination of these two therapies an attractive cancer treatment option. The complications involved in dosing and scheduling of these therapies make mathematical modeling an appropriate method for analyzing and predicting disease response to these therapies. Here we propose a mathematical model evaluating disease response to the combination of these two therapies and explore the optimization of their dosing and scheduling. Methods: An ordinary differential equation-based formalism is proposed for simulation of tumor response to CAR-T cell therapy as well as TRT. CAR-T cell dose and injected radioactivity was input to the model. Among others, key model parameters included tumor proliferation rate, tumor cell and CAR-T cell radiosensitivity, CAR-T cell killing rate, CAR-T cell decay rate indicating persistence. Preclinical experiments involving CS1- CAR-T cell therapy and 225Ac-DOTA-Daratumumab TRT in a multiple myeloma mice model were used to parameterize the model. Sensitivity study of the model parameters using overall survival (OS) and progression-free survival (PFS) as evaluation metrics, was performed to elucidate the parameters with highest impact. Results: OS and PFS were 97 and 55 days when CAR-T cell therapy was given prior to TRT as compared to OS of 43 days for untreated control mice. Sensitivity study of model parameters showed that tumor proliferation has the highest impact on survival metrics. For a ±50% change in tumor proliferation rate, OS changed by -41%/+111% and PFS changed by -62%/+147%. Similar changes in TRT injected activity and CAR-T cell dose changed OS by ± 15% and ±21% respectively. Accordingly, PFS changed by roughly ±32% and ±45% respectively. A variation of the interval between the therapies showed that faster growing tumors required a shorter interval between the two therapies. The sequence of therapies was also changed and TRT prior to CAR-T cell therapy demonstrated shorter PFS (43 days) due to the adverse effects of radiation on CAR-T cells. Conclusion: For a fixed dose of TRT and CAR-T cells, tumor proliferation rate was found to be the prime factor impacting therapy interval. The presented work shows the key parameters required for planning and optimizing preclinical experiments and clinical trials. Using disease, CAR-T cell and radionuclide-specific parameters as shown in this work as well as incorporating immune stimulating effects of radiation would make it an extremely potent tool for optimizing combination therapies. Citation Format: Vikram Adhikarla, Dennis Awuah, Alexander B. Brummer, Enrico Caserta, Amrita Krishnan, Flavia Pichiorri, Megan M. Minnix, John E. Shively, Jeffrey Y.C. Wong, Xiuli Wang, Russell C. Rockne. A mathematical model for optimization of combination therapy involving targeted radionuclide and CAR-T cell therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2732.

Sorafenib inhibits ovarian cancer cell proliferation and mobility and induces radiosensitivity by targeting the tumor cell epithelial-mesenchymal transition.

Sorafenib, a pan-protein kinase inhibitor, inhibits the activity of various kinases (like vascular endothelial growth factor, platelet-derived growth factor, and rapidly accelerated fibrosarcoma) and clinically has been used to treat different human cancers. This study investigated its antitumor activity in ovarian cancer and the underlying molecular events. To achieve that, ovarian cancer SKOV-3 cells were treated with or without sorafenib (10 µM), transforming growth factor (TGF)-β1 (10 ng/mL), sorafenib (10 µM) + TGF-β1 (10 ng/mL), and TGF-β1 (10 ng/mL) + Ly2157299 (5 µM), followed by 8-Gy radiation. The cells were then subjected to cell viability, wound healing, Transwell, caspase-3 activity, and western blot assays. TGF-β1 treatment enhanced ovarian cancer cell epithelial–mesenchymal transition (EMT), whereas sorafenib and a selective TGF-β1 inhibitor Ly2157299 reversed tumor cell EMT, invasion, and expression of EMT markers (E-cadherin and vimentin). Sorafenib and Ly2157299 treatment also significantly reduced the tumor cell viability. Furthermore, both sorafenib and Ly2157299 significantly enhanced ovarian cancer cell radiosensitivity, as assessed by a caspase-3 activity assay. In conclusion, sorafenib inhibited ovarian cancer cell proliferation and mobility and induced tumor cell radiosensitivity. Molecularly, sorafenib could inhibit the TGF-β1-mediated EMT. Future studies will assess sorafenib anti-ovarian cancer activity plus TGF-β1 inhibitors in ovarian cancer in vivo.

Nanomaterials Based on Functional Polymers for Sensitizing Cancer Radiotherapy.

Despite being the mainstay treatment for many types of cancer in clinic, radiotherapy is undertaking great challenges in overcoming a series of limitations. Radiosensitizers are promising agents capable of depositing irradiation energy and generating free radicals to enhance the radiosensitivity of tumor cells. Combining radiosensitizers with functional polymer-based nanomaterials holds great potential to improve biodistribution, circulation time, and stability in vivo. The derived polymeric nano-radiosensitizers can significantly improve the efficiency of tumor targeting and radiotherapy, and reduce the side effect to healthy tissues. In this review, an overview of functional polymer-based nanomaterials for radiosensitization in recent years is provided. Particular emphases are given to the action mechanisms, drug loading methods, targeting efficiencies, the impact on therapeutic effects, and biocompatibility of various radiosensitizing polymers, which are classified as polymeric micelles, dendrimers, polymeric nanospheres, nanoscale coordination polymers, polymersomes, and nanogels. The challenges and outlooks of polymeric nano-radiosensitizers are also discussed.