Radiotherapy Response Research Articles

High PDGFRb Expression Predicts Resistance to Radiotherapy in DCIS within the SweDCIS Randomized Trial.

This study analyzes the potential of stromal platelet-derived growth factor receptor-beta (PDGFRb) expression as biomarker for radiotherapy (RT) benefit on ipsilateral breast events (IBE) in ductal carcinoma in situ (DCIS). Improved identification of DCIS patients refractory to adjuvant whole-breast RT is needed. Predictive biomarker studies in DCIS have focused on tumor cell features rather than the tumor-associated stroma, despite growing evidence of its influence on therapy efficiency. Samples from the Swedish randomized radiotherapy DCIS trial (SweDCIS) were subjected to IHC analysis for stromal PDGFRb expression. IBE incidence at 10 years after breast-conserving surgery was the primary endpoint. Interactions between marker and treatment were analyzed. PDGFRb score was predictive for RT benefit with regard to IBE (P interaction = 0.002 and P interaction = 0.008 adjusted multivariably). Patients of the PDGFRblow group had a strong benefit from RT regarding IBE risk [HR, 0.23; 95% confidence interval (CI), 0.12-0.45; P < 0.001] with an absolute risk reduction of 21% (cumulative risk 7% vs. 28%) at 10 years. No significant risk reduction by RT was observed for patients of the PDGFRbhigh group (HR, 0.83; 0.51-1.34; P = 0.444; cumulative risk 22% vs. 25%). The RT response-predictive effect of stromal PDGFRb was equally strong in analyses for in situ and invasive IBE when analyzed separately (in situ IBE: P = 0.029; invasive IBE: P = 0.044). Results suggest high stromal PDGFRb expression as a novel biomarker identifying DCIS patients who are refractory to standard whole-breast adjuvant RT. The data imply previously unrecognized fibroblast-mediated modulation of radiosensitivity of DCIS, which should be further explored from mechanistic and targeting perspectives.

The responder/nonresponder phenomena: The immune system’s role in determining the outcome of radiation therapy in rectal cancer

Abstract While surgical resection is a viable option to treat patients with rectal cancer (RC), it is not without significantly reducing patients’ quality of life. In an effort to delay or even prevent surgery, patients are often administered pre-operative radiation therapy (RT). Although RT can significantly reduce tumor burden in a subset of patients, there are many patients whose tumors do not respond to RT. To study this, we developed an orthotopic model of RC that recapitulates human disease in which administration of clinically relevant RT results in mice bearing tumors that demonstrate a reduction of tumor burden (responders), and a group of animals whose tumors respond poorly (nonresponders). RNA-sequencing of intratumoral immune populations identified a unique gene signature associated with each group. Tumor-associated macrophages (TAMs) from nonresponding tumors were more similar to TAMs from untreated tumors when compared to TAMs from responding tumors. Interestingly, TAMs in responding tumors upregulate pathways associated with pattern recognition receptor signaling and damage associated molecular patterns. These data suggest that TAMs from responding tumors may be polarized to respond to the immunostimulatory damage induced by RT. While TAM polarization plays a large role in promoting either an immunostimulatory or immunosuppressive microenvironment, CD8+ T cells are directly responsible for killing tumor cells. We sequenced intratumoral CD8+ T cells as well and determined that T cells from responding tumors induced pathways consistent with enhanced effector function. These data suggest that a targeted therapy aimed at the TAM:CD8+ T cell interaction may promote a stronger RT response in the nonresponding tumors.

Effect of Moderate and High Intensity Exercise on Hypoxia and Radiosensitivity in Tumor‐Bearing Rats

Background Prostate tumors typically have hypoxic regions that are resistant to traditional radiation therapy. Prior evidence from our laboratory has demonstrated improved perfusion and reduced hypoxia of prostate tumors with moderate intensity exercise training; such changes have potential to enhance radiation therapy. However, there is a dearth of evidence for the magnitude of alterations of intra-tumor hypoxia markers with exercise, as well as the ideal intensity of exercise for combating hypoxia in solid tumors. Using a pre-clinical orthotopic model of prostate cancer, we tested the hypothesis that exercise training at both moderate and high intensities would result in a decrease in hypoxia assessed via immunohistochemical analysis of hypoxic markers. Further, that enhanced radiotherapy responses would occur in exercise trained tumor bearing animals compared to sedentary counterparts. Methods Immunocompetent male Copenhagen rats aged 6 months (n=48) were injected orthotopically (ventral lobe of prostate) with 1x105 Dunning R-3327 AT-1 prostate adenocarcinoma cells. All animals were first acclimated to treadmill exercise and randomized into three groups: tumor bearing sedentary (TBS, n=20), moderate intensity training, (TBMIT, n=12), or high intensity training (TBHIT, n=16). After 7 days of recovery from surgery, both exercise groups began progressive exercise training on a motorized treadmill at either 20/min with a 5% incline, or 30m/min 15% incline for 10 minutes a day progressing to 60 min/day for TBMIT and TBHIT, respectively, for approximately 5 weeks. Immunohistochemical analysis and whole-body ionizing radiation (2 Gy) were performed at the end of the 5-week period of training followed by clonogenic cell survival assay to assess survival fraction. Results There were no significant differences (p>0.05) in tumor mass between groups (TBS 7.8±1.1; TBMIT 7.2±1.3; TBHIT 6.4±0.9 g). Overall expression levels of hypoxia inducible factor 1-alpha (HIF-1a, n=40) were significantly greater in the TBS group vs both the TBMIT and TBHIT (TBS 37.9±7.4; TBMIT 25.5±6.1; TBHIT 14.4±5.7%, p<0.05), with a trend for increased expression in TBMIT vs TBHIT (p=0.059). The survival fraction (n=8) was also significantly higher in TBS when compared to both TBMIT and TBHIT (TBS 39.9±5.3; TBMIT 23.2±3.2; TBHIT 20.7±4.9%, p<0.05). Conclusion This study suggests that compared to sedentary counterparts, both chronic moderate and high intensity exercise training modify the tumor microenvironment (decreased levels of HIF-1a) favorably. Given exercise therapy is becoming increasingly recommended to mitigate fatigue and increase quality of life in patients, a potential therapeutic component could add to the efficacy of exercise prescription in a clinical setting.

Investigation of Chromosome 1 Aberrations in the Lymphocytes of Prostate Cancer and Benign Prostatic Hyperplasia Patients by Fluorescence in situ Hybridization.

PurposeRadiotherapy is one of the most common treatments for prostate cancer. Finding a useful predictor of the therapeutic outcome is crucial as it increases the efficacy of treatment planning. This study investigated the individual susceptibility to radiation based on chromosome 1 aberration frequency measured by the FISH (fluorescence in situ hybridization) method.Patients and MethodsWhole blood samples were collected from 27 prostate cancer (PCa) patients and 32 subjects with benign prostatic hyperplasia (BPH), who were considered as a control group. Samples were irradiated with 2 Gy of x-rays, cultured, harvested, and used in the FISH procedure.ResultsAfter irradiation, significantly higher levels of all studied chromosome 1 aberrations (except for deletions) in the group of PCa patients were revealed. Furthermore, in the lymphocytes of cancer patients, nearly five-fold higher frequencies of acentric fragments were observed compared to the BPH group. The highest individual radiosensitivities for all estimated biomarkers were seen in PCa patient cells who reported cancer incidence in the immediate family (CIF+).ConclusionThe differences in chromosome 1 aberrations between PCa and BPH demonstrate that lymphocytes taken from patients with prostate cancer have higher radiosensitivity which might be related to hereditary or familiar inclinations. Therefore, this technique may find future application in searching biomarkers of the cellular radiotherapy response in prostate cancer patients.

Victoria (Australia) radiotherapy response to working through the first and second wave of COVID‐19: Strategies and staffing

IntroductionThe COVID‐19 pandemic demanded a rapid response within Radiation Oncology services to minimise the risk of infection to patients and workforce. This study aimed to assess whether the operational changes put in place to reduce infection risks were effective in engaging and supporting staff.MethodsOur service’s response saw staff and patients split into morning or afternoon shifts without overlap. Changes included extended clinic hours, modified treatment regimens, expanded online/electronic communication and remote working. Staff were invited to respond to an electronic questionnaire in September 2020, just after the peak of the second COVID‐19 wave in Victoria. Responses captured demographic data, parental status, profession, happiness levels, fear of COVID‐19 and e‐communication efficacy.ResultsA 57% response rate was achieved. 69% of respondents were female; 40% were aged 45+ and 35% had school‐aged children. Staff aged 45+ showed a significantly greater fear of COVID‐19 than younger staff. 36% of respondents reported feeling nervous or anxious watching news reports about COVID‐19. 92% of staff were happy with their work arrangements; staff with children were happier than staff without children with their shifts. Online chat/channels were reported as the preferred e‐communication method between colleagues.ConclusionStaff provided predominantly positive feedback to the changes made in response to the pandemic, reporting high levels of happiness and willingness to continue with the changes implemented during COVID‐19. The strategies adopted worked well and the overall high levels of staff satisfaction will allow our service to quickly pivot should further surges, or another pandemic, arise.

Abstract PR-001: Angiotensin II receptor blockers modify the solid tumor microenvironment and improve radiation therapy response

Abstract Poorly oxygenated (hypoxic) cells are key components of the solid tumor microenvironment and are well-established contributors to poor therapeutic outcome. Patients with tumors that contain hypoxic cells have worse outcome after radiotherapy, chemotherapy, and surgery, underscoring the therapeutic relevance of hypoxia in driving more aggressive tumor phenotypes. Angiotensin II type 1 receptor (AT1R) blockers (ARBs) are widely prescribed anti-hypertensive agents that inhibit the activity of angiotensin II derived from the renin-angiotensin system. ARBs have also been shown to exhibit anti-fibrotic activity by inhibiting AT1R expressed on myofibroblasts. We recently reported that the ARB telmisartan inhibits collagen I (Col1) deposition in solid tumors, increasing net tumor perfusion, stabilizing microregional tumor blood flow, and decreasing tumor hypoxia. Cancer-associated fibroblasts (CAFs) produce Col1, although recent clinical data indicate the presence of multiple, functionally-diverse CAF subsets in tumors from patients with breast or ovarian cancer. To further explore how ARBs and CAFs affect the solid tumor microenvironment, we were interested in whether murine CAF subsets are present in human tumor xenografts and, if so, whether telmisartan preferentially influences collagen-producing CAF subsets in solid tumors. We were also interested in whether telmisartan affects collagen deposition, hypoxia, and radiation response in head &amp; neck and cervix tumors that are commonly treated with ionizing radiation therapy. We then asked whether head &amp; neck cancer patients taking ARBs as anti-hypertensive medications have quantifiably different tumor microenvironments and improved therapeutic outcome. Using a panel of six human head &amp; neck and cervix tumor xenografts, we identified four unique subsets (S1-S4) of CAFs that are present at varying levels in the different tumor lines. Telmisartan significantly altered the CAF content of tumors while also reducing CAF-mediated collagen deposition in the tumor microenvironment. We found that telmisartan also decreased tumor hypoxia and improved radiation response in our pre-clinical models, indicating that CAF subsets help to create hypoxia and contribute to radioresistance of solid tumors in an AT1R-dependent manner. Using a retrospective cohort of over 1,100 oropharyngeal cancer patients, we found that patients taking ARBs had dramatically improved therapeutic outcomes after radiation therapy, validating our pre-clinical data and supporting the further development and testing of ARBs as neoadjuvant therapies for patients with hypoxic tumors. Understanding how the solid tumor microenvironment influences cancer therapy is central to improving treatment outcome, and our work identifies CAFs as key contributors to the development of hypoxia in solid tumors. Repurposing clinically approved, anti-hypertensive ARBs represents a novel therapeutic strategy to inhibit CAF activity, modify the solid tumor microenvironment, reduce tumor hypoxia, and improve radiation response. Citation Format: Brennan J. Wadsworth, Che-Min Lee, Ryan Urban, Sarah N. Hamilton, Kevin L. Bennewith. Angiotensin II receptor blockers modify the solid tumor microenvironment and improve radiation therapy response [abstract]. In: Proceedings of the AACR Virtual Special Conference on Radiation Science and Medicine; 2021 Mar 2-3. Philadelphia (PA): AACR; Clin Cancer Res 2021;27(8_Suppl):Abstract nr PR-001.

Quantitative Molecular Positron Emission Tomography Imaging Using Advanced Deep Learning Techniques.

The widespread availability of high-performance computing and the popularity of artificial intelligence (AI) with machine learning and deep learning (ML/DL) algorithms at the helm have stimulated the development of many applications involving the use of AI-based techniques in molecular imaging research. Applications reported in the literature encompass various areas, including innovative design concepts in positron emission tomography (PET) instrumentation, quantitative image reconstruction and analysis techniques, computer-aided detection and diagnosis, as well as modeling and prediction of outcomes. This review reflects the tremendous interest in quantitative molecular imaging using ML/DL techniques during the past decade, ranging from the basic principles of ML/DL techniques to the various steps required for obtaining quantitatively accurate PET data, including algorithms used to denoise or correct for physical degrading factors as well as to quantify tracer uptake and metabolic tumor volume for treatment monitoring or radiation therapy treatment planning and response prediction.This review also addresses future opportunities and current challenges facing the adoption of ML/DL approaches and their role in multimodality imaging.

MR-Guided Radiotherapy for Rectal Cancer: Current Perspective on Organ Preservation.

Online MRI-guided radiotherapy (MRgRT) is one of the most recent technological advances in radiotherapy. MRgRT permits the visualization of tumorous and healthy tissue while the patient is on the treatment table and online daily plan adaptations following the observed anatomical changes. In the context of rectal cancer, online MRgRT is a very promising modality due to the pronounced geographical variability of tumor tissues and the surrounding healthy tissues. This current paper will discuss the possible applications of online MRgRT, in particular, in terms of radiotherapy dose escalation and response prediction in organ preservation approaches for rectal cancer.

Developing a lncRNA Signature to Predict the Radiotherapy Response of Lower-Grade Gliomas Using Co-expression and ceRNA Network Analysis.

BackgroundLower-grade glioma (LGG) is a type of central nervous system tumor that includes WHO grade II and grade III gliomas. Despite developments in medical science and technology and the availability of several treatment options, the management of LGG warrants further research. Surgical treatment for LGG treatment poses a challenge owing to its often inaccessible locations in the brain. Although radiation therapy (RT) is the most important approach in this condition and offers more advantages compared to surgery and chemotherapy, it is associated with certain limitations. Responses can vary from individual to individual based on genetic differences. The relationship between non-coding RNA and the response to radiation therapy, especially at the molecular level, is still undefined.MethodsIn this study, using The Cancer Genome Atlas dataset and bioinformatics, the gene co-expression network that is involved in the response to radiation therapy in lower-grade gliomas was determined, and the ceRNA network of radiotherapy response was constructed based on three databases of RNA interaction. Next, survival analysis was performed for hub genes in the co-expression network, and the high-efficiency biomarkers that could predict the prognosis of patients with LGG undergoing radiotherapy was identified.ResultsWe found that some modules in the co-expression network were related to the radiotherapy responses in patients with LGG. Based on the genes in those modules and the three databases, we constructed a ceRNA network for the regulation of radiotherapy responses in LGG. We identified the hub genes and found that the long non-coding RNA, DRAIC, is a potential molecular biomarker to predict the prognosis of radiotherapy in LGG.

MR-Guided Radiotherapy for Brain and Spine Tumors.

MRI is the standard modality to assess anatomy and response to treatment in brain and spine tumors given its superb anatomic soft tissue contrast (e.g., T1 and T2) and numerous additional intrinsic contrast mechanisms that can be used to investigate physiology (e.g., diffusion, perfusion, spectroscopy). As such, hybrid MRI and radiotherapy (RT) devices hold unique promise for Magnetic Resonance guided Radiation Therapy (MRgRT). In the brain, MRgRT provides daily visualizations of evolving tumors that are not seen with cone beam CT guidance and cannot be fully characterized with occasional standalone MRI scans. Significant evolving anatomic changes during radiotherapy can be observed in patients with glioblastoma during the 6-week fractionated MRIgRT course. In this review, a case of rapidly changing symptomatic tumor is demonstrated for possible therapy adaptation. For stereotactic body RT of the spine, MRgRT acquires clear isotropic images of tumor in relation to spinal cord, cerebral spinal fluid, and nearby moving organs at risk such as bowel. This visualization allows for setup reassurance and the possibility of adaptive radiotherapy based on anatomy in difficult cases. A review of the literature for MR relaxometry, diffusion, perfusion, and spectroscopy during RT is also presented. These techniques are known to correlate with physiologic changes in the tumor such as cellularity, necrosis, and metabolism, and serve as early biomarkers of chemotherapy and RT response correlating with patient survival. While physiologic tumor investigations during RT have been limited by the feasibility and cost of obtaining frequent standalone MRIs, MRIgRT systems have enabled daily and widespread physiologic measurements. We demonstrate an example case of a poorly responding tumor on the 0.35 T MRIgRT system with relaxometry and diffusion measured several times per week. Future studies must elucidate which changes in MR-based physiologic metrics and at which timepoints best predict patient outcomes. This will lead to early treatment intensification for tumors identified to have the worst physiologic responses during RT in efforts to improve glioblastoma survival.

Outcomes of Patients With Spinal Metastases From Prostate Cancer Treated With Conventionally-Fractionated External Beam Radiation Therapy.

Retrospective cohort study. To evaluate the outcomes of conventionally-fractionated external beam radiation therapy (cEBRT) in the treatment of prostate cancer spinal metastases (PCSM). Patients who received palliative cEBRT for PCSM in our institution between 2008 and 2018 were included. Our outcomes were local progression-free survival (LPFS), overall survival (OS), pain response and toxicities graded using CTCAE version 4.03. Univariable and multivariable Cox proportional hazard regressions were performed to identify predictors for LPFS and OS. A total of 100 patients with 132 sites of PCSM were identified, with a median follow-up of 54 months. Fourteen-percent of patients underwent surgical intervention before receiving cEBRT. Eighteen spinal segments (13.6%) had local progression, with a median time to local progression of 8 months. The median LPFS and OS were 7.8 and 9.0 months, respectively. The complete and partial pain response rates were 57% and 39% respectively. The incidence of grade ≥3 acute toxicities was 11%. Better ECOG performance status (0 to 1), castration-sensitive disease, spinal surgery and use of novel antiandrogen agent were identified as significant predictors for improved OS on multivariable analysis. In our prostate cancer cohort, cEBRT is an effective treatment modality for local palliation of spinal metastases. More aggressive treatment approach should be considered for patients with excellent performance status and castration-sensitive disease in light of their expected longer survival. Further studies are warranted to identify the predictors for radiotherapy response in this population.

Differential and longitudinal immune gene patterns associated with reprogrammed microenvironment and viral mimicry in response to neoadjuvant radiotherapy in rectal cancer

BackgroundRectal cancers show a highly varied response to neoadjuvant radiotherapy/chemoradiation (RT/CRT) and the impact of the tumor immune microenvironment on this response is poorly understood. Current clinical tumor regression grading...

Role of Non-coding RNAs on the Radiotherapy Sensitivity and Resistance of Head and Neck Cancer: From Basic Research to Clinical Application.

Head and neck cancers (HNCs) rank as the sixth common and the seventh leading cause of cancer-related death worldwide, with an estimated incidence of 600,000 cases and 40–50% mortality rate every year. Radiotherapy is a common local therapeutic modality for HNC mainly through the function of ionizing radiation, with approximately 60% of patients treated with radiotherapy or chemoradiotherapy. Although radiotherapy is more advanced and widely used in clinical practice, the 5-year overall survival rates of locally advanced HNCs are still less than 40%. HNC cell resistance to radiotherapy remains one of the major challenges to improve the overall survival in HNC patients. Non-coding RNAs (ncRNAs) are newly discovered functional small RNA molecules that are different from messenger RNAs, which can be translated into a protein. Many previous studies have reported the dysregulation and function of ncRNAs in HNC. Importantly, researchers reported that several ncRNAs were also dysregulated in radiotherapy-sensitive or radiotherapy-resistant HNC tissues compared with the normal cancer tissues. They found that ectopically elevating or knocking down expression of some ncRNAs could significantly influence the response of HNC cancer cells to radiotherapy, indicating that ncRNAs could regulate the sensitivity of cancer cells to radiotherapy. The implying mechanism for ncRNAs in regulating radiotherapy sensitivity may be due to its roles on affecting DNA damage sensation, inducing cell cycle arrest, regulating DNA damage repair, modulating cell apoptosis, etc. Additionally, clinical studies reported that in situ ncRNA expression in HNC tissues may predict the response of radiotherapy, and circulating ncRNA from body liquid serves as minimally invasive therapy-responsive and prognostic biomarkers in HNC. In this review, we aimed to summarize the current function and mechanism of ncRNAs in regulating the sensitivity of HNC cancer cells to radiotherapy and comprehensively described the state of the art on the role of ncRNAs in the prognosis prediction, therapy monitoring, and prediction of response to radiotherapy in HNC.

RESPONSE TO EXTERNAL RADIATION AND INTERSTITIAL BRACHYTHERAPY IN BULKY VULVAR CANCER

Vulvar cancer is a gynaecologic malignancy with an incidence of 3-5% of all gynaecologic malignancies. In Indonesia, number of new cases of vulvar cancer reaches 1153 cases with a mortality rate of 420. Multimodal therapy is the main therapy of vulvar cancer at advanced stage which consists of of surgery, radiotherapy, and chemotherapy. The role of brachytherapy as adjunctive therapy combined with EBRT is widely studied, especially its role in the management of patients with comorbidities or contraindications to surgery. The purpose of writing this case report is to assess the response of radiotherapy in the form of external beam radiotherapy (EBRT) and brachytherapy use the MUPIT applicator in patients with vulvar cancer. From the relevant studies, we obtain a good 5-year overall survival rate, disease free survival rate, and local control with tolerable complications. It can be concluded that the combination of EBRT and brachytherapy can be one of the therapeutic modality of choice in vulvar cancer.

Effect of ATR Inhibition in RT Response of HPV-Negative and HPV-Positive Head and Neck Cancers.

Radiotherapy (RT) has a central role in head and neck squamous cell carcinoma (HNSCC) treatment. Targeted therapies modulating DNA damage response (DDR) and more specific cell cycle checkpoints can improve the radiotherapeutic response. Here, we assessed the influence of ataxia-telangiectasia mutated and Rad3-related (ATR) inhibition with the ATR inhibitor AZD6738 on RT response in both human papillomavirus (HPV)-negative and HPV-positive HNSCC. We found that ATR inhibition enhanced RT response in HPV-negative and HPV-positive cell lines independent of HPV status. The radiosensitizing effect of AZD6738 was correlated with checkpoint kinase 1 (CHK1)-mediated abrogation of G2/M-arrest. This resulted in the inhibition of RT-induced DNA repair and in an increase in the percentage of micronucleated cells. We validated the enhanced RT response in HPV-negative and HPV-positive xenograft models. These data demonstrate the potential use of ATR inhibition in combination with RT as a treatment option for both HPV-negative and HPV-positive HNSCC patients.

18F-FDG PET/CT in GIST treatment response evaluation beyond Imatinib.

Positron emission tomography/computed tomography (PET/CT) represents a reliable promising tool in treatment response evaluation of new therapies beyond Imatinib in gastrointestinal stromal tumors (GIST). This narrative review aims to discuss the literature about the role of fluorine-18-fluorodeoxyglucose (18F-FDG) PET/CT in evaluating response in new tyrosine kinase inhibitors (TKI) and radiotherapy (RT) in GIST patients. A comprehensive literature search was performed to retrieve original studies published on PubMed, Scopus and Google Scholar databases. Eighteen studies including 382 patients with GIST were selected. Main findings of included studies are presented. Fluorine-18-FDG PET/CT may enhance performance in GIST management providing significant information in evaluation of treatment response and representing a strong predictor of clinical outcome.

Hypoxic tumour cell-derived exosomal miR-340-5p promotes radioresistance of oesophageal squamous cell carcinoma via KLF10

BackgroundRadiotherapy resistance is a major obstacle in the treatment of oesophageal squamous cell carcinoma (OSCC). Hypoxia is a critical cause of radioresistance. However, the communication between hypoxic cells and aerobic cells via exosomes during the transfer of radiation resistance remains unclear.MethodsExo-miR-340-5p levels were analysed by RNA-seq and qRT-PCR. We co-cultured OSCC cells with isolated normoxic and hypoxic exosomes to study their impact on radiosensitivity. We used a specific exo-miR-340-5p mimic and knock-down retrovirus to explore the role of this miRNA in the transfer of radioresistance from hypoxic to normoxic cells. Dual-luciferase reporter and RIP assays were used to verify KLF10 as a putative target of miR-340-5p. Several in vitro assays were conducted and xenograft models were established to investigate the effect of exo-miR-340-5p on OSCC radiosensitivity. The plasma exo-miR-340-5p levels in OSCC patients were analysed to study the clinical value of this parameter.ResultsHypoxic exosomes alleviated radiation-induced apoptosis and accelerated DNA damage repair. miR-340-5p was highly expressed in hypoxic exosomes and was transferred into normoxic cells, where it induced radioresistance. Overexpression of miR-340-5p in normoxic OSCC cells mimicked the radioresistance of cells co-cultured with hypoxic exosomes. Knockdown of miR-340-5p in hypoxic exosomes reversed the radioresistance effect, indicating that exo-miR-340-5p is critical for hypoxic EV-transferred radioresistance. KLF10 was identified as the direct target of miR-340-5p. Moreover, metformin was found to increase the expression of KLF10 and enhance the radiosensitivity of OSCC. Higher levels of miR-340-5p in the plasma exosomes from OSCC patients are related to a poorer radiotherapy response and prognosis.ConclusionsHypoxic tumour cell-derived exosomal miR-340-5p confers radioresistance in OSCC by targeting KLF10/UVRAG, suggesting that miR-340-5p could be a potential biomarker and therapeutic target for the enhancement of radiosensitivity in OSCC. Metformin can increase KLF10 expression, which ameliorates the radioresistance induced by exo-miR-340-5p transfer. Therefore, metformin could be further investigated as a therapeutic option for the treatment of OSCC.

Senolytic Targeting of Bcl-2 Anti-Apoptotic Family Increases Cell Death in Irradiated Sarcoma Cells.

Simple SummaryLimited volumetric change after pre-operative radiotherapy (RT) suggests that sarcomas generally do not undergo cell death. Senolytic drugs represent a highly promising field as a new therapy approach to drive senescent cancer cells towards cell death to enhance treatment response. Here, we demonstrate that the Bcl-2 family of anti-apoptotic proteins in irradiated senescent sarcoma cells represents a senotherapeutic target to improve the cell death response in RT. This study paves the way for new treatment options in soft tissue sarcoma management.Radiotherapy (RT) is a key component of cancer treatment. Most of the time, radiation is given after surgery but for soft-tissue sarcomas (STS), pre-surgical radiation is commonly utilized. However, despite improvements in RT accuracy, the rate of local recurrence remains high and is the major cause of death for patients with STS. A better understanding of cell fates in response to RT could provide new therapeutic options to enhance tumour cell killing by RT and facilitate surgical resection. Here, we showed that irradiated STS cell cultures do not die but instead undergo therapy-induced senescence (TIS), which is characterized by proliferation arrest, senescence-associated β-galactosidase activity, secretion of inflammatory cytokines and persistent DNA damage. STS-TIS was also associated with increased levels of the anti-apoptotic Bcl-2 family of proteins which rendered cells targetable using senolytic Bcl-2 inhibitors. As oppose to radiation alone, the addition of senolytic agents Venetoclax (ABT-199) or Navitoclax (ABT-263) after irradiation induced a rapid apoptotic cell death in STS monolayer cultures and in a more complex three-dimensional culture model. Together, these data suggest a new promising therapeutic approach for sarcoma patients who receive neoadjuvant RT. The addition of senolytic agents to radiation treatments may significantly reduce tumour volume prior to surgery and thereby improve the clinical outcome of patients.

Identification of a Dexamethasone Mediated Radioprotection Mechanism Reveals New Therapeutic Vulnerabilities in Glioblastoma.

Simple SummaryThe standard of care for patients with newly diagnosed glioblastoma (GBM) comprises surgery followed by radio- and chemotherapy. In addition, dexamethasone is used to manage the development of inflammation within the brain in general, and particularly during treatment. The effects of dexamethasone on patient survival however remain controversial because several clinical studies suggest that dexamethasone could potentially restrict effective radiotherapy. With the idea to improve GBM therapy, we set out to identify small molecule inhibitors that could improve the killing of GBM cells when applied together with radiotherapy. We have identified a novel dexamethasone-induced mechanism that can directly protect GBM cells from radiotherapy and thus may contribute to the adverse effects observed in the clinic. Strikingly, this mechanism also sensitises GBM cells to tyrosine kinase inhibitors, thus encouraging the revision of the use of these inhibitors for the treatment of GBM, potentially in an adjuvant setting.(1) Background: Despite the indisputable effectiveness of dexamethasone (DEXA) to reduce inflammation in glioblastoma (GBM) patients, its influence on tumour progression and radiotherapy response remains controversial. (2) Methods: We analysed patient data and used expression and cell biological analyses to assess effects of DEXA on GBM cells. We tested the efficacy of tyrosine kinase inhibitors in vitro and in vivo. (3) Results: We confirm in our patient cohort that administration of DEXA correlates with worse overall survival and shorter time to relapse. In GBM cells and glioma stem-like cells (GSCs) DEXA down-regulates genes controlling G2/M and mitotic-spindle checkpoints, and it enables cells to override the spindle assembly checkpoint (SAC). Concurrently, DEXA up-regulates Platelet Derived Growth Factor Receptor (PDGFR) signalling, which stimulates expression of anti-apoptotic regulators BCL2L1 and MCL1, required for survival during extended mitosis. Importantly, the protective potential of DEXA is dependent on intact tyrosine kinase signalling and ponatinib, sunitinib and dasatinib, all effectively overcome the radio-protective and pro-proliferative activity of DEXA. Moreover, we discovered that DEXA-induced signalling creates a therapeutic vulnerability for sunitinib in GSCs and GBM cells in vitro and in vivo. (4) Conclusions: Our results reveal a novel DEXA-induced mechanism in GBM cells and provide a rationale for revisiting the use of tyrosine kinase inhibitors for the treatment of GBM.

Radiation Response in the Tumour Microenvironment: Predictive Biomarkers and Future Perspectives.

Radiotherapy (RT) is a primary treatment modality for a number of cancers, offering potentially curative outcomes. Despite its success, tumour cells can become resistant to RT, leading to disease recurrence. Components of the tumour microenvironment (TME) likely play an integral role in managing RT success or failure including infiltrating immune cells, the tumour vasculature and stroma. Furthermore, genomic profiling of the TME could identify predictive biomarkers or gene signatures indicative of RT response. In this review, we will discuss proposed mechanisms of radioresistance within the TME, biomarkers that may predict RT outcomes, and future perspectives on radiation treatment in the era of personalised medicine.