Targeting DNA Double-Strand Break Repair Pathways to Improve Radiotherapy Response

Arsenic sulfide enhances radiosensitivity in rhabdomyosarcoma via activating NFATc3-RAG1 mediated DNA double strand break (DSB)

Rhabdomyosarcoma (RMS) represents one of the most lethal soft-tissue sarcomas in children. The toxic trace element arsenic has been reported to function as a radiosensitizer in sarcomas. To investigate the role of arsenic sulfide (As4S4) in enhancing radiation sensitization in RMS, this study was conducted to elucidate its underlying mechanism in radiotherapy. The combination of As4S4 and radiotherapy showed significant inhibition in RMS cells, as demonstrated by the cell counting kit-8 (CCK-8) assay and flow cytometry. Subsequently, we demonstrated for the first time that As4S4, as well as the knockdown of NFATc3 led to double-strand break (DSB) through increased expression of RAG1. In vivo experiment confirmed that co-treatment efficiently inhibited RMS growth. Furthermore, survival analysis of a clinical cohort consisting of 59 patients revealed a correlation between NFATc3 and RAG1 expression and overall survival (OS). Cox regression analysis also confirmed the independent prognostic significance of NFATc3 and RAG1.Taken together, As4S4 enhances radiosensitivity in RMS via activating NFATc3-RAG1 mediated DSB. NFATc3 and RAG1 are potential therapeutic targets. As4S4 will hopefully serve as a prospective radio-sensitizing agent for RMS.

Increasing DNA damage sensitivity through corylin-mediated inhibition of homologous recombination

BACKGROUND

DNA repair allows the survival of cancer cells. Therefore, the development of DNA repair inhibitors is a critical need for sensitizing cancers to chemoradiation. Sae2CtIP has specific functions in initiating DNA end resection, as well as coordinating cell cycle checkpoints, and it also greatly interacts with the DDR at different levels.

RESULTS

In this study, we demonstrated that corylin, a potential sensitizer, causes deficiencies in DNA repair and DNA damage checkpoints in yeast cells. More specifically, corylin increases DNA damage sensitivity through the Sae2-dependent pathway and impairs the activation of Mec1-Ddc2, Rad53-p and γ-H2A. In breast cancer cells, corylin increases apoptosis and reduces proliferation following Dox treatment by inhibiting CtIP. Xenograft assays showed that treatment with corylin combined with Dox significantly reduced tumor growth in vivo.

CONCLUSIONS

Our findings herein delineate the mechanisms of action of corylin in regulating DNA repair and indicate that corylin has potential long-term clinical utility as a DDR inhibitor.

In vitro evaluation of the selective cytotoxicity and genotoxicity of three synthetic ortho-nitrobenzyl derivatives in human cancer cell lines, with and without metabolic activation

Although the presence of nitro groups in chemicals can be recognized as structural alerts for mutagenicity and carcinogenicity, nitroaromatic compounds have attracted considerable interest as a class of agents that can serve as source of potential new anticancer agents. In the present study, the in vitro cytotoxicity, genotoxicity, and mutagenicity of three synthetic ortho-nitrobenzyl derivatives (named ON-1, ON-2 and ON-3) were evaluated by employing human breast and ovarian cancer cell lines. A series of biological assays was carried out with and without metabolic activation. Complementarily, computational predictions of the pharmacokinetic properties and druglikeness of the compounds were performed in the Swiss ADME platform. The MTT assay showed that the compounds selectively affected selectively the cell viability of cancer cells in comparison with a nontumoral cell line. Additionally, the metabolic activation enhanced cytotoxicity, and the compounds affected cell survival, as demonstrated by the clonogenic assay. The comet assay, the cytokinesis-block micronucleus assay, and the immunofluorescence of the γ-H2AX foci formation assay have that the compounds caused chromosomal damage to the cancer cells, with and without metabolic activation. The results obtained in the present study showed that the compounds assessed were genotoxic and mutagenic, inducing double-strand breaks in the DNA structure. The high selectivity indices observed for the compounds ON-2 and ON-3, especially after metabolic activation with the S9 fraction, must be highlighted. These experimental biological results, as well as the theoretical properties predicted for the compounds have shown that they are promising anticancer candidates to be exploited in additional studies.

Natural Guardians: Natural Compounds as Radioprotectors in Cancer Therapy

Cancer remains a significant global health challenge, with millions of deaths attributed to it annually. Radiotherapy, a cornerstone in cancer treatment, aims to destroy cancer cells while minimizing harm to healthy tissues. However, the harmful effects of irradiation on normal cells present a formidable obstacle. To mitigate these effects, researchers have explored using radioprotectors and mitigators, including natural compounds derived from secondary plant metabolites. This review outlines the diverse classes of natural compounds, elucidating their roles as protectants of healthy cells. Furthermore, the review highlights the potential of these compounds as radioprotective agents capable of enhancing the body's resilience to radiation therapy. By integrating natural radioprotectors into cancer treatment regimens, clinicians may improve therapeutic outcomes while minimizing the adverse effects on healthy tissues. Ongoing research in this area holds promise for developing complementary strategies to optimize radiotherapy efficacy and enhance patient quality of life.

Cyclin-dependent kinase inhibitor 1A inhibits pyroptosis to enhance human lung adenocarcinoma cell radioresistance by promoting DNA repair

Purpose

One of the best anticancer treatments available is radiotherapy, which can be used either alone or in conjunction with other forms of treatment including chemotherapy and surgery. Nevertheless, a number of biochemical and physiological processes that react to ionizing radiation might provide tumor cells radioresistance, which makes radiotherapy ineffective. It has been found that CDKN1A regulates DNA damage repair, which contributes to tumor radioresistance. However, the precise mechanism is still unknown. Therefore, this study aimed to explore the mechanisms underlying CDKN1A-enhanced radioresistance in tumor cells.

Methods

Cells were irradiated with 4 Gy after CDKN1A overexpression or knockdown. CDKN1A expression was measured using real-time PCR, cell viability was evaluated using cell counting kit-8 and colony formation assays, and cytotoxicity was assessed using a lactate dehydrogenase assay. Pyroptosis in cells was analyzed using caspase-1 activity assay, enzyme-linked immunosorbent assay, and flow cytometry. Inflammation activation was detected through a co-immunoprecipitation assay. Activation of pyroptosis-related proteins was analyzed using immunohistochemistry, Western blot, and immunofluorescence. Tumor radioresistance in vivo was evaluated in a mouse xenograft model.

Results

Radiotherapy upregulated CDKN1A expression, which promoted lung adenocarcinoma cell survival. CDKN1A influenced radiation-induced pyroptosis in A549, which mainly depended on inhibiting the activation of the AIM2 inflammasome by promoting DNA repair. Additionally, CDKN1A upregulation enhanced A549 xenograft tumor radioresistance by inhibiting radiation-induced pyroptosis in vivo.

Conclusions

CDKN1A inhibits pyroptosis to enhance the radioresistance of lung adenocarcinoma cells by promoting DNA repair. This study may serve as a reference for developing novel targeted therapies against cancer.

Peripheral blood lymphocytes differ in DNA damage response after exposure to X-rays with different physical properties

Introduction: In radiology, low X-ray energies (<140 keV) are used to obtain an optimal image while in radiotherapy, higher X-ray energies (MeV) are used to eradicate tumor tissue. In radiation research, both these X-ray energies being used to extrapolate in vitro research to clinical practice. However, the energy deposition of X-rays depends on their energy spectrum, which might lead to changes in biological response. Therefore, this study compared the DNA damage response (DDR) in peripheral blood lymphocytes (PBLs) exposed to X-rays with varying beam quality, mean photon energy (MPE) and dose rate.Methods: The DDR was evaluated in peripheral blood lymphocytes (PBLs) by the ɣ-H2AX foci assay, the cytokinesis-block micronucleus assay and an SYTOX-based cell death assay, combined with specific cell death inhibitors. Cell cultures were irradiated with a 220 kV X-ray research cabinet (SARRP, X-Strahl) or a 6 MV X-ray linear accelerator (Elekta Synergy). Three main physical parameters were investigated: beam quality (V), MPE (eV) and dose rate (Gy/min). Additional copper (Cu) filtration caused variation in the MPE (78 keV, 94 keV, 118 keV) at SARRP; dose rates were varied by adjusting tube current for 220 kV X-rays (0.33-3 Gy/min) or water-phantom depth in the 6 MV set-up (3-6 Gy/min).Results: The induction of chromosomal damage and initial (30 min) DNA double-stranded breaks (DSBs) were significantly higher for 220 kV X-rays compared to 6 MV X-rays, while cell death induction was similar. Specific cell death inhibitors for apoptosis, necroptosis and ferroptosis were not capable of blocking cell death after irradiation using low or high-energy X-rays. Additional Cu filtration increased the MPE, which significantly decreased the amount of chromosomal damage and DSBs. Within the tested ranges no specific effects of dose rate variation were observed.Conclusion: The DDR in PBLs is influenced by the beam quality and MPE. This study reinforces the need for consideration and inclusion of all physical parameters in radiation-related studies.

Efficacy and Safety Analysis of Recombinant Human Endostatin (Endostar) Combined With Chemoradiotherapy for Locally Advanced Cervical Cancer: A 2-Center Retrospective Study

BACKGROUND

This study aims to assess the efficacy and safety of Endostar in the management of locally advanced cervical cancer.

METHODS

This retrospective, 2-center study enrolled 41 patients with locally advanced cervical cancer between June 2017 and December 2020. The patients were subjected to a combination of Endostar and chemoradiotherapy until they experienced disease progression or an unacceptable level of toxicity. The patients in the Endostar combined chemoradiotherapy (E + CRT) and CRT groups were matched 1:1 based on clinical features, including age, disease stage, and pathological type. The therapeutic efficacy and safety outcomes were compared between the 2 groups.

RESULTS

Early treatment response: the CR rates in E + CRT and CRT groups were 48.8% and 26.8%, respectively (χ2 = 4.20, P < .05). The ORR and DCR were not significantly different between the 2 groups. Long-term efficacy: there was no significant difference in the 1-year and 2-year PFS rates and OS rates between 2 groups. However, in patients with stage IIB, subgroup analyses revealed a significant difference in PFS between the 2 groups (P < .05). Prognostic factors: stage, Eastern Cooperative Oncology Group (ECOG) score, and tumor size were independent predictive factors for PFS, while ECOG score and tumor size were those of OS in patients with locally advanced cervical cancer. Safety: The incidence of grade III-IV myelosuppression was significantly lower in E + CRT group than in CRT group (P < .05).

CONCLUSIONS

The combination of Endostar and concurrent CRT exhibited greater efficacy in treating locally advanced cervical cancer with no severe adverse reactions, when compared to simple CRT. It is expected that this approach will evolve into a new treatment alternative for patients with locally advanced cervical cancer.

Effects of radiation therapy on tumor microenvironment: an updated review

ABSTRACT

Cancer is a major threat to human health and causes death worldwide. Research on the role of radiotherapy (RT) in the treatment of cancer is progressing; however, RT not only causes fatal DNA damage to tumor cells, but also affects the interactions between tumor cells and different components of the tumor microenvironment (TME), including immune cells, fibroblasts, macrophages, extracellular matrix, and some soluble products. Some cancer cells can survive radiation and have shown strong resistance to radiation through interaction with the TME. Currently, the complex relationships between the tumor cells and cellular components that play major roles in various TMEs are poorly understood. This review explores the relationship between RT and cell-cell communication in the TME from the perspective of immunity and hypoxia and aims to identify new RT biomarkers and treatment methods in lung cancer to improve the current status of unstable RT effect and provide a theoretical basis for further lung cancer RT sensitization research in the future.

Advances in molecular targeted therapies to increase efficacy of (chemo)radiation therapy

Recent advances in understanding the tumor's biology in line with a constantly growing number of innovative technologies have prompted characterization of patients' individual malignancies and may display a prerequisite to treat cancer at its patient individual tumor vulnerability. In recent decades, radiation- induced signaling and tumor promoting local events for radiation sensitization were explored in detail, resulting the development of novel molecular targets. A multitude of pharmacological, genetic, and immunological principles, including small molecule- and antibody-based targeted strategies, have been developed that are suitable for combined concepts with radiation (RT) or chemoradiation therapy (CRT). Despite a plethora of promising experimental and preclinical findings, however, so far, only a very limited number of clinical trials have demonstrated a better outcome and/or patient benefit when RT or CRT are combined with targeted agents. The current review aims to summarize recent progress in molecular therapies targeting oncogenic drivers, DNA damage and cell cycle response, apoptosis signaling pathways, cell adhesion molecules, hypoxia, and the tumor microenvironment to impact therapy refractoriness and to boost radiation response. In addition, we will discuss recent advances in nanotechnology, e.g., RNA technologies and protein-degrading proteolysis-targeting chimeras (PROTACs) that may open new and innovative ways to benefit from molecular-targeted therapy approaches with improved efficacy.

Liquid-liquid phase separation in DNA double-strand breaks repair

DNA double-strand breaks (DSBs) are the fatal type of DNA damage mostly induced by exposure genome to ionizing radiation or genotoxic chemicals. DSBs are mainly repaired by homologous recombination (HR) and nonhomologous end joining (NHEJ). To repair DSBs, a large amount of DNA repair factors was observed to be concentrated at the end of DSBs in a specific spatiotemporal manner to form a repair center. Recently, this repair center was characterized as a condensate derived from liquid-liquid phase separation (LLPS) of key DSBs repair factors. LLPS has been found to be the mechanism of membraneless organelles formation and plays key roles in a variety of biological processes. In this review, the recent advances and mechanisms of LLPS in the formation of DSBs repair-related condensates are summarized.

Cyclin D1 promotes radioresistance through regulation of RAD51 in melanoma

Melanoma is a notoriously radioresistant type of skin cancer. Elucidation of the specific mechanisms underlying radioresistance is necessary to improve the clinical efficacy of radiation therapy. To identify the key factors contributing to radioresistance, five melanoma cell lines were selected for study and genes that were upregulated in relatively radioresistant melanomas compared with radiosensitive melanoma cells determined via RNA sequencing technology. In particular, we focused on cyclin D1 (CCND1), a well known cell cycle regulatory molecule. In radiosensitive melanoma, overexpression of cyclin D1 reduced apoptosis. In radioresistant melanoma cell lines, suppression of cyclin D1 with a specific inhibitor or siRNA increased apoptosis and decreased cell proliferation in 2D and 3D spheroid cultures. In addition, we observed increased expression of γ-H2AX, a molecular marker of DNA damage, even at a later time after γ-irradiation, under conditions of inhibition of cyclin D1, with a response pattern similar to that of radiosensitive SK-Mel5. In the same context, expression and nuclear foci formation of RAD51, a key enzyme for homologous recombination (HR), were reduced upon inhibition of cyclin D1. Downregulation of RAD51 also reduced cell survival to irradiation. Overall, suppression of cyclin D1 expression or function led to reduced radiation-induced DNA damage response (DDR) and triggered cell death. Our collective findings indicate that the presence of increased cyclin D1 potentially contributes to the development of radioresistance through effects on RAD51 in melanoma and could therefore serve as a therapeutic target for improving the efficacy of radiation therapy.

Antioxidative stress protein SRXN1 can be used as a radiotherapy prognostic marker for prostate cancer

PURPOSE

To explore the mechanisms of radiotherapy resistance and search for prognostic biomarkers for prostate cancer.

METHODS

The GSE192817 and TCGA PRAD datasets were selected and downloaded from the GEO and UCSC Xena databases. Differential expression and functional annotation analyses were applied to 52 tumour cell samples from GSE192817. Then, the ssGSEA or GSVA algorithms were applied to quantitatively score the biological functional activity of samples in the GSE192817 and TCGA PRAD datasets, combined with specific gene sets collected from the Molecular Signatures Database (MSigDB). Subsequently, the Wilcoxon rank-sum test was used to compare the differences in ssGSEA or GSVA scores among cell types or PRAD patients. Moreover, radiotherapy resistance-associated gene screening was performed on DU145 and PC3 cells (prostate cancer cells), and survival analysis was used to evaluate the efficacy of these genes for predicting the prognosis of PRAD patients.

RESULTS

A total of 114 genes that were differentially expressed in more than two different cancer cell types and associated with either sham surgery or radiotherapy treatment (X-ray or photon irradiation) were detected in cancer cells from GSE192817. Comparison of DNA damage-related ssGSEA scores between sham surgery and radiotherapy treatment in prostate cancer cells (DU145 and PC3) showed that photon irradiation was potentially more effective than X-ray treatment. In the TCGA PRAD dataset, patients treated with radiotherapy had much higher "GOBP_CELLULAR_RESPONSE_TO_DNA_DAMAGE_STIMULUS", "GOBP_G2_DNA_DAMAGE_CHECKPOINT" and "GOBP_INTRA_S_DNA_DAMAGE_CHECKPOINT" GSVA scores, and the Wilcoxon rank-sum test p values were 0.0005, 0.0062 and 0.0800, respectively. Furthermore, SRXN1 was upregulated in DU145 cells (resistant to X-ray irradiation compared to PC3 cells) after radiotherapy treatment, and low SRXN1 expression in patients was beneficial to radiotherapy outcomes. The log-rank test p value for PFS was 0.0072.

CONCLUSIONS

Radiotherapy can damage DNA and induce oxidative stress to kill tumour cells. In this study, we found that SRXN1, as an antioxidative stress gene, plays an important role in radiotherapy for prostate cancer treatment, and this gene is also a potential biomarker for predicting the prognosis of patients treated with radiotherapy.

Role of the cGAS-STING pathway in radiotherapy for non-small cell lung cancer

One of the most important therapeutic interventions for non-small cell lung cancer is radiotherapy. Ionizing radiation (IR) is classified by traditional radiobiology principles as a direct cytocidal therapeutic agent against cancer, although there is growing recognition of other antitumor immunological responses induced by this modality. The most effective therapeutic combinations to harness radiation-generated antitumor immunity and enhance treatment results for malignancies resistant to existing radiotherapy regimens could be determined by a more sophisticated understanding of the immunological pathways created by radiation. Innate immune signaling is triggered by the activation of cGAS-STING, and this promotes adaptive immune responses to help fight cancer. This identifies a molecular mechanism radiation can use to trigger antitumor immune responses by bridging the DNA-damaging ability of IR with the activation of CD8 + cytotoxic T cell-mediated killing of tumors. We also discuss radiotherapy-related parameters that affect cGAS-STING signaling, negative consequences of cGAS-STING activation, and intriguing treatment options being tested in conjunction with IR to support immune activation by activating STING-signaling. Improved therapeutic outcomes will result from a better understanding of how IR promotes cGAS-STING signaling in immune-based treatment regimens that maximize radiotherapy's anticancer effectiveness.

Advances in radiotherapy and immunity in hepatocellular carcinoma

Primary liver cancer is one of the most common malignant tumours worldwide; it caused approximately 830,000 deaths in 2020. Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer, accounting for over 80% of all cases. Various methods, including surgery, chemotherapy, radiotherapy, and radiofrequency ablation, have been widely used in the treatment of HCC. With the advancement of technology, radiotherapy has become increasingly important in the comprehensive treatment of HCC. However, due to the insufficient sensitivity of tumour cells to radiation, there are still multiple limitation in clinical application of radiotherapy. In recent years, the role of immunotherapy in cancer has been increasingly revealed, and more researchers have turned their attention to the combined application of immunotherapy and radiotherapy in the hope of achieving better treatment outcomes. This article reviews the progress on radiation therapy in HCC and the current status of its combined application with immunotherapy, and discusses the prospects and value of radioimmunotherapy in HCC.

MDM2 Inhibition in the Treatment of Glioblastoma: From Concept to Clinical Investigation

Inhibition of the interaction between MDM2 and p53 has emerged as a promising strategy for combating cancer, including the treatment of glioblastoma (GBM). Numerous MDM2 inhibitors have been developed and are currently undergoing rigorous testing for their potential in GBM therapy. Encouraging results from studies conducted in cell culture and animal models suggest that MDM2 inhibitors could effectively treat a specific subset of GBM patients with wild-type TP53 or functional p53. Combination therapy with clinically established treatment modalities such as radiation and chemotherapy offers the potential to achieve a more profound therapeutic response. Furthermore, an increasing array of other molecularly targeted therapies are being explored in combination with MDM2 inhibitors to increase the effects of individual treatments. While some MDM2 inhibitors have progressed to early phase clinical trials in GBM, their efficacy, alone and in combination, is yet to be confirmed. In this article, we present an overview of MDM2 inhibitors currently under preclinical and clinical investigation, with a specific focus on the drugs being assessed in ongoing clinical trials for GBM patients.

Maintaining Genome Integrity: Protein Kinases and Phosphatases Orchestrate the Balancing Act of DNA Double-Strand Breaks Repair in Cancer

DNA double-strand breaks (DSBs) are the most lethal DNA damages which lead to severe genome instability. Phosphorylation is one of the most important protein post-translation modifications involved in DSBs repair regulation. Kinases and phosphatases play coordinating roles in DSB repair by phosphorylating and dephosphorylating various proteins. Recent research has shed light on the importance of maintaining a balance between kinase and phosphatase activities in DSB repair. The interplay between kinases and phosphatases plays an important role in regulating DNA-repair processes, and alterations in their activity can lead to genomic instability and disease. Therefore, study on the function of kinases and phosphatases in DSBs repair is essential for understanding their roles in cancer development and therapeutics. In this review, we summarize the current knowledge of kinases and phosphatases in DSBs repair regulation and highlight the advancements in the development of cancer therapies targeting kinases or phosphatases in DSBs repair pathways. In conclusion, understanding the balance of kinase and phosphatase activities in DSBs repair provides opportunities for the development of novel cancer therapeutics.

Radiotherapy and radio-sensitization in H3K27M -mutated diffuse midline gliomas

BACKGROUND

H3^K27M mutated diffuse midline gliomas (DMGs) are extremely aggressive and the leading cause of cancer-related deaths in pediatric brain tumors with 5-year survival <1%. Radiotherapy is the only established adjuvant treatment of H3^K27M DMGs; however, the radio-resistance is commonly observed.

METHODS

We summarized current understandings of the molecular responses of H3^K27M DMGs to radiotherapy and provide crucial insights into current advances in radiosensitivity enhancement.

RESULTS

Ionizing radiation (IR) can mainly inhibit tumor cell growth by inducing DNA damage regulated by the cell cycle checkpoints and DNA damage repair (DDR) system. In H3K27M DMGs, the aberrant genetic and epigenetic changes, stemness genotype, and epithelial-mesenchymal transition (EMT) disrupt the cell cycle checkpoints and DDR system by altering the associated regulatory signaling pathways, which leads to the development of radio-resistance.

CONCLUSIONS

The advances in mechanisms of radio-resistance in H3^K27M  DMGs promote the potential targets to enhance the sensitivity to radiotherapy.

Radiosensitization of IDH-Mutated Gliomas through ZMYND8 - a Pathway to Improved Outcomes

Isocitrate dehydrogenase 1-mutant (IDH1m) gliomas are recalcitrant tumors for which radiotherapy remains a standard treatment. A recent study identified ZMYND8 as a key mediator of radioresistance for IDH1m gliomas, and pharmacologic targeting of this pathway may heighten radiotherapy-induced tumor response, providing a prospect of improved clinical outcomes. See related article by Carney et al., p. 1763.

Non-coding RNAs in radiotherapy resistance: Roles and therapeutic implications in gastrointestinal cancer

Radiotherapy has become an indispensable and conventional means for patients with advanced solid tumors including gastrointestinal cancer. However, innate or acquired radiotherapy resistance remains a significant challenge and greatly limits the therapeutic effect, which results in cancer relapse and poor prognosis. Therefore, it is an urgent need to identify novel biomarkers and therapeutic targets for clarify the biological characteristics and mechanism of radiotherapy resistance. Recently, lots of studies have revealed that non-coding RNAs (ncRNAs) are the potential indicators and regulators of radiotherapy resistance via the mediation of various targets/pathways in different cancers. These findings may serve as a potential therapeutic strategy to overcome radiotherapy resistance. In this review, we will shed light on the recent findings regarding the functions and regulatory mechanisms of ncRNAs following radiotherapy, and comprehensively discuss their potential as biomarkers and therapeutic targets in radiotherapy resistance of gastrointestinal cancer.

Spermine oxidase induces DNA damage and sensitizes fusion negative rhabdomyosarcoma cells to irradiation

Rhabdomyosarcoma (RMS) is a pediatric myogenic soft tissue sarcoma that includes fusion-positive (FP) and fusion-negative (FN) molecular subtypes. FP-RMS expresses PAX3-FOXO1 fusion protein and often shows dismal prognosis. FN-RMS shows cytogenetic abnormalities and frequently harbors RAS pathway mutations. Despite the multimodal heavy chemo and radiation therapeutic regimens, high risk metastatic/recurrent FN-RMS shows a 5-year survival less than 30% due to poor sensitivity to chemo-radiotherapy. Therefore, the identification of novel targets is needed. Polyamines (PAs) such as putrescine (PUT), spermidine (SPD) and spermine (SPM) are low-molecular-mass highly charged molecules whose intracellular levels are strictly modulated by specific enzymes. Among the latter, spermine oxidase (SMOX) regulates polyamine catabolism oxidizing SPM to SPD, which impacts cellular processes such as apoptosis and DNA damage response. Here we report that low SMOX levels are associated with a worse outcome in FN-RMS, but not in FP-RMS, patients. Consistently, SMOX expression is downregulated in FN-RMS cell lines as compared to normal myoblasts. Moreover, SMOX transcript levels are reduced FN-RMS cells differentiation, being indirectly downregulated by the muscle transcription factor MYOD. Noteworthy, forced expression of SMOX in two cell lines derived from high-risk FN-RMS: 1) reduces SPM and upregulates SPD levels; 2) induces G0/G1 cell cycle arrest followed by apoptosis; 3) impairs anchorage-independent and tumor spheroids growth; 4) inhibits cell migration; 5) increases γH2AX levels and foci formation indicative of DNA damage. In addition, forced expression of SMOX and irradiation synergize at activating ATM and DNA-PKCs, and at inducing γH2AX expression and foci formation, which suggests an enhancement in DNA damage response. Irradiated SMOX-overexpressing FN-RMS cells also show significant decrease in both colony formation capacity and spheroids growth with respect to single approaches. Thus, our results unveil a role for SMOX as inhibitor of tumorigenicity of FN-RMS cells in vitro. In conclusion, our in vitro results suggest that SMOX induction could be a potential combinatorial approach to sensitize FN-RMS to ionizing radiation and deserve further in-depth studies.

Application of individualized multimodal radiotherapy combined with immunotherapy in metastatic tumors

Radiotherapy is one of the mainstays of cancer treatment. More than half of cancer patients receive radiation therapy. In addition to the well-known direct tumoricidal effect, radiotherapy has immunomodulatory properties. When combined with immunotherapy, radiotherapy, especially high-dose radiotherapy (HDRT), exert superior systemic effects on distal and unirradiated tumors, which is called abscopal effect. However, these effects are not always effective for cancer patients. Therefore, many studies have focused on exploring the optimized radiotherapy regimens to further enhance the antitumor immunity of HDRT and reduce its immunosuppressive effect. Several studies have shown that low-dose radiotherapy (LDRT) can effectively reprogram the tumor microenvironment, thereby potentially overcoming the immunosuppressive stroma induced by HDRT. However, bridging the gap between preclinical commitment and effective clinical delivery is challenging. In this review, we summarized the existing studies supporting the combined use of HDRT and LDRT to synergistically enhance antitumor immunity, and provided ideas for the individualized clinical application of multimodal radiotherapy (HDRT+LDRT) combined with immunotherapy.

JNJ-64619178 radiosensitizes and suppresses fractionated ionizing radiation-induced neuroendocrine differentiation (NED) in prostate cancer

Background

Radiation therapy (RT) is a standard treatment regimen for locally advanced prostate cancer; however, its failure results in tumor recurrence, metastasis, and cancer-related death. The recurrence of cancer after radiotherapy is one of the major challenges in prostate cancer treatment. Despite overall cure rate of 93.3% initially, prostate cancer relapse in 20-30% patients after radiation therapy. Cancer cells acquire radioresistance upon fractionated ionizing radiation (FIR) treatment, eventually undergo neuroendocrine differentiation (NED) and transform into neuroendocrine-like cells, a mechanism involved in acquiring resistance to radiation therapy. Radiosensitizers are agents that inhibit the repair of radiation-induced DNA damage. Protein arginine methyltransferase 5 (PRMT5) gets upregulated upon ionizing radiation treatment and epigenetically activates DNA damage repair genes in prostate cancer cells. In this study, we targeted PRMT5 with JNJ-64619178 and assessed its effect on DNA damage repair gene activation, radiosensitization, and FIR-induced NED in prostate cancer.

Methods

γH2AX foci analysis was performed to evaluate the DNA damage repair after radiation therapy. RT-qPCR and western blot were carried out to analyze the expression of DNA damage repair genes. Clonogenic assay was conducted to find out the surviving fraction after radiation therapy. NED was targeted with JNJ-64619178 in androgen receptor (AR) positive and negative prostate cancer cells undergoing FIR treatment.

Results

JNJ-64619178 inhibits DNA damage repair in prostate cancer cells independent of their AR status. JNJ-64619178 impairs the repair of ionizing radiation-induced damaged DNA by transcriptionally inhibiting the DNA damage repair gene expression and radiosensitizes prostate, glioblastoma and lung cancer cell line. It targets NED induced by FIR in prostate cancer cells.

Conclusion

JNJ-64619178 can radiosensitize and suppress NED induced by FIR in prostate cancer cells and can be a potential radiosensitizer for prostate cancer treatment.

Anticancer activity of methotrexate in electrochemotherapy and electrochemotherapy plus ionizing radiation treatments in human breast cancer cells

Traditional cancer treatments, such as chemotherapy and radiotherapy have several limitations. Therefore, their performance must be enhanced with combined methods. The purpose of this study is to investigate both the efficacy of electroporation (EP) on the activity of methotrexate (MTX) and the combined treatment of electrochemotherapy (ECT) + ionizing radiation (IR) in MCF-7 cancer cells. Different treatment techniques, such as EP, MTX, MTX + EP (ECT), 140 kV X-ray alone (IR_140kV), 500 kV X-ray alone (IR_500kV), ECT + IR_140kV and ECT + IR_500kV, were applied to cancer cells. Eight electric pulse trains with square wave (800 V/cm, 100 µs and 1 Hz) were used in EP and ECT applications. The MTT assay was used to assess the efficacy of the therapies used. When the EP, MTX, ECT, IR_140kV, and IR_500kV treatment groups were compared to the control group, there was a significant reduction in MCF-7 cancer cells viability (p < 0.05). ECT was the most effective of these treatments, decreasing viability of cancer cells to 58.78%. The ECT + IR_140kV and ECT + IR_500kV groups were compared to the ECT group to examine the impact of X-ray radiation on ECT treatment. When compared to the ECT alone group, both groups that exposed to X-rays after ECT had a significant decrease in cell viability (p < 0.05). Furthermore, viability of MCF-7 cells reduced to 46.38% in the ECT + IR_140kV group and 35.89% in the ECT + IR_500kV group. In conclusion, the study shows that the cytotoxicity of MTX is significantly increased in ECT treatment compared to standard chemotherapy (p < 0.05). In addition, ECT + IR combined therapy application is much more effective than MTX or ECT treatments alone.

The botanical drug PBI-05204, a supercritical CO2 extract of Nerium oleander, sensitizes alveolar and embryonal rhabdomyosarcoma to radiotherapy in vitro and in vivo

Treatment of rhabdomyosarcoma (RMS), the most common a soft tissue sarcoma in childhood, provides intensive multimodal therapy, with radiotherapy (RT) playing a critical role for local tumor control. However, since RMS efficiently activates mechanisms of resistance to therapies, despite improvements, the prognosis remains still largely unsatisfactory, mainly in RMS expressing chimeric oncoproteins PAX3/PAX7-FOXO1, and fusion-positive (FP)-RMS. Cardiac glycosides (CGs), plant-derived steroid-like compounds with a selective inhibitory activity of the Na+/K+-ATPase pump (NKA), have shown antitumor and radio-sensitizing properties. Herein, the therapeutic properties of PBI-05204, an extract from Nerium oleander containing the CG oleandrin already studied in phase I and II clinical trials for cancer patients, were investigated, in vitro and in vivo, against FN- and FP-RMS cancer models. PBI-05204 induced growth arrest in a concentration dependent manner, with FP-RMS being more sensitive than FN-RMS, by differently regulating cell cycle regulators and commonly upregulating cell cycle inhibitors p21Waf1/Cip1 and p27Cip1/Kip1. Furthermore, PBI-05204 concomitantly induced cell death on both RMS types and senescence in FN-RMS. Notably, PBI-05204 counteracted in vitro migration and invasion abilities and suppressed the formation of spheroids enriched in CD133+ cancer stem cells (CSCs). PBI-05204 sensitized both cell types to RT by improving the ability of RT to induce G2 growth arrest and counteracting the RT-induced activation of both Non‐Homologous End‐Joining and homologous recombination DSBs repair pathways. Finally, the antitumor and radio-sensitizing proprieties of PBI-05204 were confirmed in vivo. Notably, both in vitro and in vivo evidence confirmed the higher sensitivity to PBI-05204 of FP-RMS. Thus, PBI-05204 represents a valid radio-sensitizing agent for the treatment of RMS, including the intrinsically radio-resistant FP-RMS.

The lysosome as a novel therapeutic target of EGFR-mediated tumor inflammation

EGFR-mediated tumors have been targeted to overcome several different malignant cancers. EGFR overexpression and mutations are directly related to the malignancy, which makes the therapy more complicated. One reason for the malignancy is the induction of AP1 followed by inflammation via IL-6 secretion. Current therapeutic strategies to overcome EGFR-mediated tumors are tyrosine kinase inhibitors (TKIs), anti-EGFR monoclonal antibodies, and the combination of these two agents with classic chemotherapy or immune checkpoint inhibitors (ICIs). Although the strategies are straightforward and have shown promising efficacy in several studies, there are still hurdles to overcoming the adverse effects and limited efficacy. This study reviews the current therapeutic strategies to target EGFR family members, how they work, and their effects and limitations. We also suggest developing novel strategies to target EGFR-mediated tumors in a novel approach. A lysosome is the main custodial staff to discard unwanted amounts of EGFR and other receptor tyrosine kinase molecules. Targeting this organelle may be a new approach to overcoming EGFR-mediated cancers.

Acquired lymphedema: Molecular contributors and future directions for developing intervention strategies

Lymphedema is a debilitating chronic disease that mostly develops as an adverse reaction to cancer treatment modalities such as chemotherapy, surgery, and radiotherapy. Lymphedema also appears to be a deteriorating consequence of roundworm infections, as best represented by filariasis. According to its origin, lymphedema is classified as primary lymphedema and acquired lymphedema. The latter is an acquired condition that, hitherto, received a considerably low attention owing to the less number of fatal cases been reported. Notably, despite the low mortality rate in lymphedema, it has been widely reported to reduce the disease-free survival and thus the quality of life of affected patients. Hence, in this review, we focused on acquired lymphedema and orchestration of molecular interplays associated with either stimulation or inhibition of lymphedema development that were, in vast majority, clearly depicted in animal models with their specific and distinct technical approaches. We also discussed some recent progress made in phytochemical-based anti-lymphedema intervention strategies and the specific mechanisms underlying their anti-lymphedema properties. This review is crucial to understand not only the comprehensive aspects of the disease but also the future directions of the intervention strategies that can address the quality of life of affected patients rather than alleviating apparent symptoms only.

Cellular and Molecular Biological Alterations after Photon, Proton, and Carbon Ions Irradiation in Human Chondrosarcoma Cells Linked with High-Quality Physics Data

Chondrosarcomas are particularly difficult to treat due to their resistance to chemotherapy and radiotherapy. However, particle therapy can enhance local control and patient survival rates. To improve our understanding of the basic cellular radiation response, as a function of dose and linear energy transfer (LET), we developed a novel water phantom-based setup for cell culture experiments and characterized it dosimetrically. In a direct comparison, human chondrosarcoma cell lines were analyzed with regard to their viability, cell proliferation, cell cycle, and DNA repair behavior after irradiation with X-ray, proton, and carbon ions. Our results clearly showed that cell viability and proliferation were inhibited according to the increasing ionization density, i.e., LET, of the irradiation modes. Furthermore, a prominent G2/M arrest was shown. Gene expression profiling proved the upregulation of the senescence genes CDKN1A (p21), CDKN2A (p16NK4a), BMI1, and FOXO4 after particle irradiation. Both proton or C-ion irradiation caused a positive regulation of the repair genes ATM, NBN, ATXR, and XPC, and a highly significant increase in XRCC1/2/3, ERCC1, XPC, and PCNA expression, with C-ions appearing to activate DNA repair mechanisms more effectively. The link between the physical data and the cellular responses is an important contribution to the improvement of the treatment system.

In vivo dosimetry in pelvic brachytherapy

ADVANCES IN KNOWLEDGE

This paper describes the potential role for in vivo dosimetry in the reduction of uncertainties in pelvic brachytherapy, the pertinent factors for consideration in clinical practice, and the future potential for in vivo dosimetry in the personalisation of brachytherapy.

CRISPR/Cas9 mediated knocking out of OPN gene enhances radiosensitivity in MDA-MB-231 breast cancer cell line

PURPOSE

Although chemotherapy and radiotherapy in conjunction with surgery have been known as the standard methods for patients with breast cancer, they frequently face resistance due to the failure of cells to death. Accordingly, improving the results requires discovering novel therapeutic approaches based on the changes in the molecular biology of cancer cells. Osteopontin (OPN) is a secreted protein that previous studies have shown to be associated with progression, poor prognosis, and metastasis in breast cancer. The current study examined the synergistic effects of radiotherapy and knocking out of OPN gene, utilizing CRISPR/Cas9 technique in MDA-MB-231 breast cancer cells.

METHODS

We used to knock out the OPN gene by the two different gRNAs. The cells irradiated 24 h after transfection. The mRNA expression, tumor cell proliferation, cell cycle distribution, growth, and apoptosis were measured. Moreover, activation of Chk1 and AKT were measured via western blot.

RESULTS

We demonstrated the OPN knocking out along with radiation led to the promotion of apoptosis, suppression of downstream genes, reduction of cell viability, and inhibition of cell-cycle progression. The western blot analysis has indicated that the knocking out of the OPN gene along with radiotherapy changes DNA damage responses substantially.

CONCLUSIONS

The OPN gene knocking out with radiotherapy might be an efficient approach to overcome the radioresistance in breast cancer.

Functional Immune Cell-Derived Exosomes Engineered for the Trilogy of Radiotherapy Sensitization

The limited efficacy of radiotherapy leads to radio-resistance and high rates of tumor recurrence and metastasis, which is caused by tumor hypoxia, rapid DNA damage repair, and especially the suppressive immune microenvironment of tumor. Lots of immune cell-derived exosomes can regulate antitumor immunity, but their application in enhancing radiotherapy is rarely studied. Herein, as a model of concept, M1 macrophage-derived exosomes (M1Exos) is engineered as effective radiotherapy sensitizers, realizing the trilogy of radiotherapy sensitization: 1) M1Exos is engineered to express catalases on the inside of membrane, which can effectively relieve tumor hypoxia, and enhance DNA damage. 2) The DNA damage repair inhibitor is loaded in M1Exos to effectively inhibit DNA damage repair. 3) M1Exos can polarize M2 macrophages into M1 phenotypes, and the anti-PD-L1 nanobody engineered on the outside of M1Exos can relieve the immunosuppression of T cells, both ultimately leading to the remodeling of the tumor suppressive microenvironment. The trilogy of radiotherapy sensitization achieves excellent antitumor efficacy, exhibiting the good utility of engineering immune cell-derived exosomes as radiotherapy sensitizers, inspiring the future efforts to explore different kinds of immune cell-derived exosomes for enhanced radiotherapy.

Nanoparticles-Based Strategies to Improve the Delivery of Therapeutic Small Interfering RNA in Precision Oncology

Small interfering RNA (siRNA) can selectively suppress the expression of disease-causing genes, holding great promise in the treatment of human diseases, including malignant cancers. In recent years, with the development of chemical modification and delivery technology, several siRNA-based therapeutic drugs have been approved for the treatment of non-cancerous liver diseases. Nevertheless, the clinical development of siRNA-based cancer therapeutics remains a major translational challenge. The main obstacles of siRNA therapeutics in oncology include both extracellular and intracellular barriers, such as instability under physiological conditions, insufficient tumor targeting and permeability (particularly for extrahepatic tumors), off-target effects, poor cellular uptake, and inefficient endosomal escape. The development of clinically suitable and effective siRNA delivery systems is expected to overcome these challenges. Herein, we mainly discuss recent strategies to improve the delivery and efficacy of therapeutic siRNA in cancer, including the application of non-viral nanoparticle-based carriers, the selection of target genes for therapeutic silencing, and the combination with other therapeutic modalities. In addition, we also provide an outlook on the ongoing challenges and possible future developments of siRNA-based cancer therapeutics during clinical translation.

Activation of Stimulation of Interferon Genes (STING) Signal and Cancer Immunotherapy

Stimulator of interferon gene (STING), an intracellular receptor in the endoplasmic reticulum, could induce the production of cytokines such as type I interferon (IFN) by activating the cGAS-STING signal pathway. In recent years, activation of STING has shown great potential to enhance anti-tumor immunity and reshape the tumor microenvironment, which is expected to be used in tumor immunotherapy. A number of STING agonists have demonstrated promising biological activity and showed excellent synergistic anti-tumor effects in combination with other cancer therapies in preclinical studies and some clinical trials. The combination of STING agonists and ICI also showed a potent effect in improving anti-tumor immunity. In this review, we introduce the cGAS-STING signaling pathway and its effect in tumor immunity and discuss the recent strategies of activation of the STING signaling pathway and its research progress in tumor immunotherapy.

PARP Inhibitors: A New Horizon for Patients with Prostate Cancer

The introduction of PARP inhibitors (PARPi) in prostate cancer is a milestone and provides a pathway to hope in fighting this disease. It is the first time that drugs, based on the concept of synthetic lethality, have been approved for prostate cancer. In addition, it is also the first time that genetic mutation tests have been included in the therapeutic algorithm of this disease, representing a significant step forward for precision and personalized treatment of prostate cancer. The objectives of this review are: (1) understanding the mechanism of action of PARPi in monotherapy and combinations; (2) gaining insights on patient selection for PARPi; (3) exposing the pivotal studies that have allowed its approval, and; (4) offering an overview of the ongoing trials. Nevertheless, many unsolved questions remain, such as the number of patients who could potentially benefit from PARPi, whether to use PARPi in monotherapy or in combination, and when is the best time to use them in advanced or localized disease. To answer these and other questions, many clinical trials are underway. Some of them have recently demonstrated promising results that may favor the introduction of new combinations in metastatic castration-resistant prostate cancer.

Monoubiquitination in Homeostasis and Cancer

Monoubiquitination is a post-translational modification (PTM), through which a single ubiquitin molecule is covalently conjugated to a lysine residue of the target protein. Monoubiquitination regulates the activity, subcellular localization, protein-protein interactions, or endocytosis of the substrate. In doing so, monoubiquitination is implicated in diverse cellular processes, including gene transcription, endocytosis, signal transduction, cell death, and DNA damage repair, which in turn regulate cell-cycle progression, survival, proliferation, and stress response. In this review, we summarize the functions of monoubiquitination and discuss how this PTM modulates homeostasis and cancer.

Characterization of radiation-induced micronuclei associated with premature senescence, and their selective removal by senolytic drug, ABT-263

Radiotherapy is well-recognized as an efficient non-invasive remedy for cancer treatment. Since 10 Gy, a weekly total dose for conventional radiotherapy, was proven to create unreparable and residual DNA double-strand breaks (DSBs), they were found to give rise to mitotic failure, such as mitotic catastrophe, which resulted in multiple micronuclei associated with premature senescence. We demonstrated that pulverization of micronuclear DNA was caspase-dependent and triggered not ATM-dependent but DNA-PK-dependent DNA damage response, including phosphorylation of histone H2AX. Pulverization of micronuclear DNA and senescence-associated secretory phenotype (SASP) worsen tumor microenvironment after radiotherapy, so that senolytic drug was applied to eliminate senescent cancer cells. Prematurely senescent cancer cells with micronuclei caused by 10 Gy of γ-irradiation were subjected to 5 μM of ABT-263, a Bcl-2 family inhibitor, and selective cancer cell death by apoptosis was observed, while ABT-263 had little effect on growing cancer cells. Western blot analysis showed augmented expression of both apoptotic and anti-apoptotic proteins in senescent cells, indicating that increased apoptotic factors are essential for selective apoptotic cell death in combination with ABT-263. Our results suggested that selective elimination of senescent cells alleviates SASP and micronuclei-mediated the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) activation, both of which lead to unfavorable adverse effects caused by radiotherapy.

PARP inhibitors as a radiosensitizer: a future promising approach in prostate cancer?

Poly (ADP-ribose) polymerase (PARP) inhibitors (iPARPs) have shown efficacy in homologous recombination (HR) deficiency patients with advanced castration resistant prostate cancer and have shown a radiosensitizing effect in preclinical and early clinical trials. Preclinical data in prostate cancer cells suggest a similar cytotoxic effect with half the radiation dose under the effect of Olaparib or Rucaparib irrespective of HR status. Due to the biologic synergy of radiotherapy (RT) and iPARPs, the risk of recurrence of high-risk prostate cancer and the morbidity associated with prostate cancer local treatment, this interesting strategy seems promising, and a better understanding of the clinical implications remains to be elucidated.

Dual-functional significance of ATM-mediated phosphorylation of spindle assembly checkpoint component Bub3 in mitosis and the DNA damage response

Both the DNA damage response (DDR) and the mitotic checkpoint are critical for the maintenance of genomic stability. Among proteins involved in these processes, the Ataxia-Telangiectasia Mutated (ATM) kinase is required for both activation of the DDR and the spindle assembly checkpoint (SAC). In mitosis without DNA damage, the enzymatic activity of ATM is enhanced; however, substrates of ATM in mitosis are unknown. Using Stable Isotope Labeled Amino Acid in cell culture (SILAC)-mass spectrometry analysis, we identified a number of proteins that can potentially be phosphorylated by ATM during mitosis. This list is highly enriched in proteins involved in cell cycle regulation and the DDR. Among them, we further validated that ATM phosphorylated Budding Uninhibited by Benzimidazoles 3 (Bub3), a major component of the SAC, on serine 135 both in vitro and in vivo. During mitosis, this phosphorylation promoted activation of another SAC component, Bub1. Mutation of Bub3 serine 135 to alanine led to a defect in SAC activation. Furthermore, we found that ATM-mediated phosphorylation of Bub3 on serine 135 was also induced by ionizing radiation-induced DNA damage. However, this event resulted in independent signaling involving interaction with the Ku70-Ku80-DNA-PKcs sensor/kinase complex, leading to efficient non-homologous end joining repair. Taken together, we highlight the functional significance of the crosstalk between the kinetochore-oriented signal and double strand break repair pathways via ATM phosphorylation of Bub3 on serine 135.

Targeted Cancer Therapy Based on Acetylation and Deacetylation of Key Proteins Involved in Double-Strand Break Repair

DNA double-strand breaks (DSBs) play an important role in promoting genomic instability and cell death. The precise repair of DSBs is essential for maintaining genome integrity during cancer progression, and inducing genomic instability or blocking DNA repair is an important mechanism through which chemo/radiotherapies exert killing effects on cancer cells. The two main pathways that facilitate the repair of DSBs in cancer cells are homologous recombination (HR) and non-homologous end-joining (NHEJ). Accumulating data suggest that the acetylation and deacetylation of DSB repair proteins regulate the initiation and progression of the cellular response to DNA DSBs, which may further affect the chemosensitivity or radiosensitivity of cancer cells. Here, we focus on the role of acetylation/deacetylation in the regulation of ataxia-telangiectasia mutated, Rad51, and 53BP1 in the HR pathway, as well as the relevant roles of PARP1 and Ku70 in NHEJ. Notably, several histone deacetylase (HDAC) inhibitors targeting HR or NHEJ have been demonstrated to enhance chemo/radiosensitivity in preclinical studies. This review highlights the essential role of acetylation/deacetylation in the regulation of DSB repair proteins, suggesting that HDAC inhibitors targeting the HR or NHEJ pathways that downregulate DNA DSB repair genes may be worthwhile cancer therapeutic agents.

Applications of nanodosimetry in particle therapy planning and beyond

This topical review summarizes underlying concepts of nanodosimetry. It describes the development and current status of nanodosimetric detector technology. It also gives an overview of Monte Carlo track structure simulations that can provide nanodosimetric parameters for treatment planning of proton and ion therapy. Classical and modern radiobiological assays that can be used to demonstrate the relationship between the frequency and complexity of DNA lesion clusters and nanodosimetric parameters are reviewed. At the end of the review, existing approaches of treatment planning based on relative biological effectiveness (RBE) models or dose-averaged linear energy transfer are contrasted with an RBE-independent approach based on nandosimetric parameters. Beyond treatment planning, nanodosimetry is also expected to have applications and give new insights into radiation protection dosimetry.

A two-stage genome-wide association study of radiation-induced acute toxicity in head and neck cancer

BACKGROUND

Most head and neck cancer (HNC) patients receive radiotherapy (RT) and develop toxicities. This genome-wide association study (GWAS) was designed to identify single nucleotide polymorphisms (SNPs) associated with common acute radiation-induced toxicities (RITs) in an HNC cohort.

METHODS

A two-stage GWAS was performed in 1279 HNC patients treated with RT and prospectively scored for mucositis, xerostomia, sticky saliva, and dysphagia. The area under the curve (AUC) was used to estimate the average load of toxicity during RT. At the discovery study, multivariate linear regression was used in 957 patients, and the top-ranking SNPs were tested in 322 independent replication cohort. Next, the discovery and the replication studies were meta-analyzed.

RESULTS

A region on 5q21.3 containing 16 SNPs showed genome-wide (GW) significance association at P-value < 5.0 × 10-8 with patient-rated acute xerostomia in the discovery study. The top signal was rs35542 with an adjusted effect size of 0.17*A (95% CI 0.12 to 0.23; P-value <  = 3.78 × 10-9). The genome wide significant SNPs were located within three genes (EFNA5, FBXL17, and FER). In-silico functional analysis showed these genes may be involved in DNA damage response and co-expressed in minor salivary glands. We found 428 suggestive SNPs (P-value < 1.0 × 10-5) for other toxicities, taken to the replication study. Eleven of them showed a nominal association (P-value < 0.05).

CONCLUSIONS

This GWAS suggested novel SNPs for patient-rated acute xerostomia in HNC patients. If validated, these SNPs and their related functional pathways could lead to a predictive assay to identify sensitive patients to radiation, which may eventually allow a more individualized RT treatment.

Clinical and Preclinical Outcomes of Combining Targeted Therapy With Radiotherapy

In the era of precision medicine, radiation medicine is currently focused on the precise delivery of highly conformal radiation treatments. However, the tremendous developments in targeted therapy are yet to fulfill their full promise and arguably have the potential to dramatically enhance the radiation therapeutic ratio. The increased ability to molecularly profile tumors both at diagnosis and at relapse and the co-incident progress in the field of radiogenomics could potentially pave the way for a more personalized approach to radiation treatment in contrast to the current ‘‘one size fits all’’ paradigm. Few clinical trials to date have shown an improved clinical outcome when combining targeted agents with radiation therapy, however, most have failed to show benefit, which is arguably due to limited preclinical data. Several key molecular pathways could theoretically enhance therapeutic effect of radiation when rationally targeted either by directly enhancing tumor cell kill or indirectly through the abscopal effect of radiation when combined with novel immunotherapies. The timing of combining molecular targeted therapy with radiation is also important to determine and could greatly affect the outcome depending on which pathway is being inhibited.

MS-275 (Entinostat) Promotes Radio-Sensitivity in PAX3-FOXO1 Rhabdomyosarcoma Cells

Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma of childhood. About 25% of RMS expresses fusion oncoproteins such as PAX3/PAX7-FOXO1 (fusion-positive, FP) while fusion-negative (FN)-RMS harbors RAS mutations. Radiotherapy (RT) plays a crucial role in local control but metastatic RMS is often radio-resistant. HDAC inhibitors (HDACi) radio-sensitize different cancer cells types. Thus, we evaluated MS-275 (Entinostat), a Class I and IV HDACi, in combination with RT on RMS cells in vitro and in vivo. MS-275 reversibly hampered cell survival in vitro in FN-RMS RD (RASmut) and irreversibly in FP-RMS RH30 cell lines down-regulating cyclin A, B, and D1, up-regulating p21 and p27 and reducing ERKs activity, and c-Myc expression in RD and PI3K/Akt/mTOR activity and N-Myc expression in RH30 cells. Further, MS-275 and RT combination reduced colony formation ability of RH30 cells. In both cell lines, co-treatment increased DNA damage repair inhibition and reactive oxygen species formation, down-regulated NRF2, SOD, CAT and GPx4 anti-oxidant genes and improved RT ability to induce G2 growth arrest. MS-275 inhibited in vivo growth of RH30 cells and completely prevented the growth of RT-unresponsive RH30 xenografts when combined with radiation. Thus, MS-275 could be considered as a radio-sensitizing agent for the treatment of intrinsically radio-resistant PAX3-FOXO1 RMS.

Multifunctional MnO2-based nanoplatform-induced ferroptosis and apoptosis for synergetic chemoradiotherapy

Background: Radiosensitizers that can effectively consume glutathione provide broad prospects for enhancing the efficacy and reducing the side effects of radiotherapy. Aim: To explore the potential role of CuS@mSiO₂@MnO₂ nanocomposites in synergetic chemoradiotherapy. Methods: Nanocomposites were characterized by transmission electron microscopy, UV-Vis spectrometry and dynamic light scattering and were loaded with doxorubicin (DOX). The uptake and biodistribution of nanocomposites were observed by CCK8 assay, MRI and confocal laser scanning microscopy. The radiosensitization effect of nanocomposites and nanocomposites/DOX was assessed both in vitro and in vivo. Results: In vitro application of nanocomposites, with an average diameter of 30 nm and ζ-potential of 13.2 ± 0.4 mV, in combination with radiotherapy, depleted glutathione and induced ferroptosis and apoptosis. Nanocomposites/DOX exhibited tumor cell damage in vivo. Conclusion: We propose that this glutathione-depleting nanosystem could be a radiosensitizer as well as a drug transporter.

Novel Radiation Therapy Paradigms and Immunomodulation: Heresies and Hope

Radiation therapy benefits the majority of patients across the spectrum of cancer types. However, both local and distant tumor recurrences limit its clinical success. While departing from the established tenet of fractionation in clinical radiotherapy, ablative-intensity hypofractionated radiotherapy, especially stereotactic radiosurgery and stereotactic ablative radiotherapy, has emerged as an alternative paradigm achieving unprecedented rates of local tumor control. Direct tumor cell killing has been assumed to be the primary therapeutic mode of action of such ablative radiation. But with increasing recognition that tumor responses also depend on the immunostimulatory or immunosuppressive status of the tumor microenvironment, the immunologic effect of ablative radiotherapy is emerging as a key contributor to antitumor response. More recently, novel radiation modalities, such as spatially fractionated radiotherapy and ultrahigh dose rate FLASH irradiation, that venture even further from conventional paradigms have shown promise of increasing the therapeutic index of radiation therapy with the potential of immunomodulation. Here, we review the immunomodulatory impact of novel radiation therapy paradigms, heretofore considered radiobiological heresies, a deeper understanding of which is imperative to realizing fully their potential for more curative cancer therapy.

Targeting protein-protein interactions in the DNA damage response pathways for cancer chemotherapy

Cellular DNA damage response (DDR) is an extensive signaling network that orchestrates DNA damage recognition, repair and avoidance, cell cycle progression and cell death. DDR alteration is a hallmark of cancer, with the deficiency in one DDR capability often compensated by a dependency on alternative pathways endowing cancer cells with survival and growth advantage. Targeting these DDR pathways has provided multiple opportunities for the development of cancer therapies. Traditional drug discovery has mainly focused on catalytic inhibitors that block enzyme active sites, which limits the number of potential drug targets within the DDR pathways. This review article describes the emerging approach to the development of cancer therapeutics targeting essential protein-protein interactions (PPIs) in the DDR network. The overall strategy for the structure-based design of small molecule PPI inhibitors is discussed, followed by an overview of the major DNA damage sensing, DNA repair, and DNA damage tolerance pathways with a specific focus on PPI targets for anti-cancer drug design. The existing small molecule inhibitors of DDR PPIs are summarized that selectively kill cancer cells and/or sensitize cancers to front-line genotoxic therapies, and a range of new PPI targets are proposed that may lead to the development of novel chemotherapeutics.

Multiplexed bioluminescence-mediated tracking of DNA double-strand break repairs in vitro and in vivo

The dynamics of DNA double-strand break (DSB) repairs including homology-directed repair and nonhomologous end joining play an important role in diseases and therapies. However, investigating DSB repair is typically a low-throughput and cross-sectional process, requiring disruption of cells and organisms for subsequent nuclease-, sequencing- or reporter-based assays. In this protocol, we provide instructions for establishing a bioluminescent repair reporter system using engineered Gaussia and Vargula luciferases for noninvasive tracking of homology-directed repair and nonhomologous end joining, respectively, induced by SceI meganuclease, SpCas9 or SpCas9 D10A nickase-mediated editing. We also describe complementation with orthogonal DSB repair assays and omics analyses to validate the reporter readouts. The bioluminescent repair reporter system provides longitudinal and rapid readout (~seconds per sample) to accurately and efficiently measure the efficacy of genome-editing tools and small-molecule modulators on DSB repair. This protocol takes ~2-4 weeks to establish, and as little as 2 h to complete the assay. The entire bioluminescent repair reporter procedure can be performed by one person with standard molecular biology expertise and equipment. However, orthogonal DNA repair assays would require a specialized facility that performs Sanger sequencing or next-generation sequencing.

The Importance of Being PI3K in the RAS Signaling Network

Ras proteins are essential mediators of a multitude of cellular processes, and its deregulation is frequently associated with cancer appearance, progression, and metastasis. Ras-driven cancers are usually aggressive and difficult to treat. Although the recent Food and Drug Administration (FDA) approval of the first Ras G12C inhibitor is an important milestone, only a small percentage of patients will benefit from it. A better understanding of the context in which Ras operates in different tumor types and the outcomes mediated by each effector pathway may help to identify additional strategies and targets to treat Ras-driven tumors. Evidence emerging in recent years suggests that both oncogenic Ras signaling in tumor cells and non-oncogenic Ras signaling in stromal cells play an essential role in cancer. PI3K is one of the main Ras effectors, regulating important cellular processes such as cell viability or resistance to therapy or angiogenesis upon oncogenic Ras activation. In this review, we will summarize recent advances in the understanding of Ras-dependent activation of PI3K both in physiological conditions and cancer, with a focus on how this signaling pathway contributes to the formation of a tumor stroma that promotes tumor cell proliferation, migration, and spread.

Changes in T Lymphocyte Subsets in Different Tumors Before and After Radiotherapy: A Meta-analysis

Purpose

Radiation therapy (RT) induces an immune response, but the relationship of this response with tumor type is not fully understood. This meta-analysis further elucidated this relationship by analyzing the changes in T lymphocyte subsets in different tumors before and after radiotherapy.

Methods

We searched English-language electronic databases including PubMed, EMBASE, and the Cochrane Library to collect studies on the changes in peripheral blood CD3+ T lymphocytes, CD4+ T lymphocytes, and CD8+ T lymphocytes before and after radiotherapy in tumor patients from January 2015 to April 2021. The quality of the included literature was evaluated using the NOS scale provided by the Cochrane Collaboration, and statistical software RevMan 5.4 was used to analyze the included literature. P<0.05 was considered to indicate statistical significance.

Results

A total of 19 studies in 16 articles involving 877 tumor patients were included. All data were collected within 1 month before or after radiotherapy. Meta-analysis showed that numbers of CD3+ T lymphocytes (SMD: -0.40; 95% CI [-0.75, -0.04]; p = 0.03) and CD4+ T lymphocytes (SMD: -0.43; 95% CI: [-0.85, -0.02]; p = 0.04) were significantly reduced after radiotherapy compared with before treatment, but there was no statistically significant difference for CD8+ T lymphocytes (SMD: 0.33; 95% CI: [-0.88, 0.74]; p = 0.12). Subgroup analysis showed that peripheral blood T lymphocytes decreased in head and neck cancer. However, in prostate cancer and breast cancer, there was no significant change in peripheral blood. 1 month after radiotherapy, it has a potential proliferation and activation effect on lymphocytes in esophageal cancer and lung cancer. The results showed that CD8+T lymphocytes increased in peripheral blood after SBRT. Radiotherapy alone reduced CD3+ T lymphocyte numbers.

Conclusions

Within 1 month of radiotherapy, patients have obvious immunological changes, which can cause apoptosis and reduction of T lymphocytes, and affect the balance of peripheral blood immune cells. The degree of immune response induced by radiotherapy differed between tumor types.

Romidepsin (FK228) fails in counteracting the transformed phenotype of rhabdomyosarcoma cells but efficiently radiosensitizes, in vitro and in vivo, the alveolar phenotype subtype

PURPOSE

Herein we describe the in vitro and in vivo activity of FK228 (Romidepsin), an inhibitor of class I HDACs, in counteracting and radiosensitizing embryonal (ERMS, fusion-negative) and alveolar (ARMS, fusion-positive) rhabdomyosarcoma (RMS).

METHODS

RH30 (ARMS, fusion-positive) and RD (ERMS, fusion-negative) cell lines and human multipotent mesenchymal stromal cells (HMSC) were used. Flow cytometry analysis, RT-qPCR, western blotting and enzymatic assays were performed. Irradiation was delivered by using an x-6 MV photon linear accelerator. FK228 (1.2 mg/kg) in vivo activity, combined or not with radiation therapy (2 Gy), was assessed in murine xenografts.

RESULTS

Compared to HMSC, RMS expressed low levels of class I HDACs. In vitro, FK228, as single agents, reversibly downregulated class I HDACs expression and activity and induced oxidative stress, DNA damage and a concomitant growth arrest associated with PARP-1-mediated transient non-apoptotic cell death. Surviving cells upregulated the expression of cyclin A, B, D1, p27, Myc and activated PI3K/Akt/mTOR and MAPK signaling, known to be differently involved in cancer chemoresistance. Interestingly, while no radiosensitizing effects were detected, in vitro or in vivo, on RD cells, FK228 markedly radiosensitized RH30 cells by impairing antioxidant and DSBs repair pathways in vitro. Further, FK228 when combined with RT in vivo significantly reduced tumor mass in mouse RH30 xenografts.

CONCLUSION

FK228 did not show antitumor activity as a single agent whilst its combination with RT resulted in radiosensitization of fusion-positive RMS cells, thus representing a possible strategy for the treatment of the most aggressive RMS subtype.

AEG-1 Knockdown Sensitizes Glioma Cells to Radiation Through Impairing Homologous Recombination Via Targeting RFC5

Radiotherapy is the most important adjuvant treatment for glioma; however, radioresistance is the major cause for inevitable recurrence and poor survival of glioma patients. Thus, this study aims to investigate the effect of astrocyte elevated gene-1 (AEG-1) on the radiosensitivity of glioma cells. Immunohistochemistry assay found that AEG-1 was generally overexpressed in glioma tissues and was correlated with poor clinicopathological features of glioma patients. AEG-1 knockdown inhibited proliferation of glioma cells. And γ-H2AX foci assay, colony formation assay, and flow cytometry analysis demonstrated that AEG-1 depletion enhanced radiosensitivity and promoted apoptosis as well as cell cycle arrest in G2 phase of glioma cells treated by ionizing radiation. Moreover, replication factor C5 (RFC5) was screened as the target of AEG-1 by using Affymetrix human gene expression array, and RFC5 expression was downregulated in AEG-1 knockdown glioma cells. Mechanistically, AEG-1 knockdown impaired homologous recombination repair activity induced by radiation through inhibiting RFC5 expression. Furthermore, the Kaplan-Meier analysis and multivariate Cox regression analysis indicated that high levels of AEG-1 and RFC5 were related to poor prognosis of glioma patients treated with radiotherapy. Taken together, our findings indicate that AEG-1 may serve as a reliable radiosensitizing target for glioma radiotherapy.