P53 and radiation responses

DNA-damage orchestrates self-renewal and differentiation via reciprocal p53 family and Hippo/Wnt/TGF-β pathway activation in embryonic stem cells

The mechanism by which DNA-damage affects self-renewal and pluripotency remains unclear. DNA damage and repair mechanisms have been largely elucidated in mutated cancer cells or simple eukaryotes, making valid interpretations on early development difficult. Here we show the impact of ionizing irradiation on the maintenance and early differentiation of mouse embryonic stem cells (ESCs). Our findings demonstrate that irradiation induces the upregulation of the p53 family genes, including p53, p63, and p73, resulting in elevated expression of the E3 ubiquitin ligases Itch and Trim32. Consequently, this impairs ESC maintenance by reducing the protein levels of key pluripotency transcription factors in both mouse ESCs and early embryos. Notably, our study reveals that irradiation-induced DNA damage leads to the recruitment of the BAF complex, causing it to dissociate from its binding sites on the target genes associated with the Yap, Wnt, and TGF-β pathways, thereby increasing signaling and promoting differentiation of ESCs into all three lineages. Importantly, pathway inhibition demonstrates that DNA damage accelerated ESC differentiation relies on Wnt and TGF-β, and is selectively dependent on p53 or p63/ p73 for mesoderm and endoderm respectively. Finally, our study reveals that p53 family proteins form complexes with effector proteins of key signaling pathways which actively contribute to ESC differentiation. In summary, this study uncovered a mechanism by which multiple differentiation signaling pathways converge on the p53 family genes to promote ESC differentiation and are impacted by exposure to ionizing radiation.

Gene regulation and signaling transduction in mediating the self-renewal, differentiation, and apoptosis of spermatogonial stem cells

ABSTRACT

Infertility has become one of the most serious diseases worldwide, and 50% of this disease can be attributed to male-related factors. Spermatogenesis, by definition, is a complex process by which spermatogonial stem cells (SSCs) self-renew to maintain stem cell population within the testes and differentiate into mature spermatids. It is of great significance to uncover gene regulation and signaling pathways that are involved in the fate determinations of SSCs with aims to better understand molecular mechanisms underlying human spermatogenesis and identify novel targets for gene therapy of male infertility. Significant achievement has recently been made in demonstrating the signaling molecules and pathways mediating the fate decisions of mammalian SSCs. In this review, we address key gene regulation and crucial signaling transduction pathways in controlling the self-renewal, differentiation, and apoptosis of SSCs, and we illustrate the networks of genes and signaling pathways in SSC fate determinations. We also highlight perspectives and future directions in SSC regulation by genes and their signaling pathways. This review could provide novel insights into the genetic regulation of normal and abnormal spermatogenesis and offer molecular targets to develop new approaches for gene therapy of male infertility.

NAD+ Metabolic Enzyme Inhibitor as Radiosensitizer for Malignant Meningioma and its Modulation of P53 Expression

Surgical resection followed by radiotherapy (RT) is recommended for malignant meningioma, but poor outcome is unavoidable. To improve the efficacy of RT in malignant meningioma, a targeted radiosensitizer can be added. Nicotinamide phosphoribosyltransferase (NAMPT), highly expressed in high-grade meningiomas, may play a role in determining the radioresponse. Herein, we evaluated the impact of NAMPT inhibition on radiosensitivity in malignant meningioma in vivo and in vitro. IOMM-Lee and TTMM705 cells were treated with NAMPT inhibition (FK866 or shRNA NAMPT) before irradiation. The subsequent clonogenic assay demonstrated significantly increased radiosensitivity. Combination treatment with FK866 and irradiation significantly increased the number of G2/M-phase cells, percentage of apoptotic cells, and γ-H2A.X level compared with FK866 or RT alone. We examined the effect of NAMPT inhibition on NMI and p53 expression in IOMM-Lee and TTMM705 cells. NAMPT inhibition by FK866 and shRNA treatment increased NMI, p53, CDKN1A and BAX expression. Additionally, we assessed the efficacy of FK866/RT combination treatment in vivo. The combination treatment exhibited increased antitumor efficacy compared with either treatment alone. The Ki67 level was significantly lower, and the p53 and γ-H2A.X levels were significantly higher in the combination treatment group than in the other three groups. In conclusion, these results indicate that FK866 improves radiosensitivity in malignant meningioma, an effect that may be attributed to the increase in p53 expression.

Somatic gene mutations involved in DNA damage response/Fanconi anemia signaling are tissue- and cell-type specific in human solid tumors

With significant advancements in the study of DNA Damage Response (DDR) and Fanconi Anemia (FA) signaling, we previously introduced the term "FA signaling" to encompass "all signaling transductions involving one or more FA proteins." This network has now evolved into the largest cellular defense network, integrating over 30 key players, including ATM, ATR, BLM, HRR6, RAD18, FANCA, FANCB, FANCC, BRCA2, FANCD2, FANCE, FANCF, FANCG, FANCI, BRIP1, FANCL, FANCM, PALB2, RAD51C, SLX4, ERCC4, RAD51, BRCA1, UBE2T, XRCC2, MAD2L2, RFWD3, FAAP20, FAAP24, FAAP100, and CENPX. This system responds to both endogenous and exogenous cellular insults. However, the mutational signatures associated with this defense mechanism in non-FA human cancers have not been extensively explored. In this study, we report that different types of human cancers are characterized by distinct somatically mutated genes related to DDR/FA signaling, each accompanied by a unique spectrum of potential driver mutations. For example, in pan-cancer samples, ATM emerges as the most frequently mutated gene (5%) among the 31 genes analyzed, with the highest number of potential driver mutations (1714), followed by BRCA2 (4% with 970 putative driver mutations). However, this pattern is not universal across specific cancer types. For example, FANCT is the most frequently mutated gene in breast (14%) and liver (4%) cancers. In addition, the alteration frequency of DDR/FA signaling due to these mutations exceeds 70% in a subtype of prostate cancer, with each subtype of brain, breast, lung, and prostate cancers displaying distinct patterns of gene alteration frequency. Furthermore, these gene alteration patterns significantly impact patient survival and disease-free periods. Collectively, our findings not only enhance our understanding of cancer development and progression but also have significant implications for cancer patient care and prognosis, particularly in the development of effective therapeutic strategies.

Senescence and senolysis in cancer: The latest findings

Aging is a life phenomenon that occurs in most living organisms and is a major risk factor for many diseases, including cancer. Cellular senescence is a cellular trait induced by various genomic and epigenetic stresses. Senescent cells are characterized by irreversible cell growth arrest and excessive secretion of inflammatory cytokines (senescence-associated secretory phenotypes, SASP). Chronic tissue microinflammation induced by SASP contributes to the pathogenesis of a variety of age-related diseases, including cancer. Senolysis is a promising new strategy to selectively eliminate senescent cells in order to suppress chronic inflammation, suggesting its potential use as an anticancer therapy. This review summarizes recent findings on the molecular basis of senescence in cancer cells and senolysis.

APR-246 as a radiosensitization strategy for mutant p53 cancers treated with alpha-particles-based radiotherapy

Radiation therapy (RT) remains a common treatment for cancer patients worldwide, despite the development of targeted biological compounds and immunotherapeutic drugs. The challenge in RT lies in delivering a lethal dose to the cancerous site while sparing the surrounding healthy tissues. Low linear energy transfer (low-LET) and high linear energy transfer (high-LET) radiations have distinct effects on cells. High-LET radiation, such as alpha particles, induces clustered DNA double-strand breaks (DSBs), potentially inducing cell death more effectively. However, due to limited range, alpha-particle therapies have been restricted. In human cancer, mutations in TP53 (encoding for the p53 tumor suppressor) are the most common genetic alteration. It was previously reported that cells carrying wild-type (WT) p53 exhibit accelerated senescence and significant rates of apoptosis in response to RT, whereas cells harboring mutant p53 (mutp53) do not. This study investigated the combination of the alpha-emitting atoms RT based on internal Radium-224 (224Ra) sources and systemic APR-246 (a p53 reactivating compound) to treat tumors with mutant p53. Cellular models of colorectal cancer (CRC) or pancreatic ductal adenocarcinoma (PDAC) harboring mutant p53, were exposed to alpha particles, and tumor xenografts with mutant p53 were treated using 224Ra source and APR-246. Effects on cell survival and tumor growth, were assessed. The spread of alpha emitters in tumors was also evaluated as well as the spatial distribution of apoptosis within the treated tumors. We show that mutant p53 cancer cells exhibit radio-sensitivity to alpha particles in vitro and to alpha-particles-based RT in vivo. APR-246 treatment enhanced sensitivity to alpha radiation, leading to reduced tumor growth and increased rates of tumor eradication. Combining alpha-particles-based RT with p53 restoration via APR-246 triggered cell death, resulting in improved therapeutic outcomes. Further preclinical and clinical studies are needed to provide a promising approach for improving treatment outcomes in patients with mutant p53 tumors.

Dynamic role of CUL4B in radiation-induced intestinal injury-regeneration

CUL4B, a crucial scaffolding protein in the largest E3 ubiquitin ligase complex CRL4B, is involved in a broad range of physiological and pathological processes. While previous research has shown that CUL4B participates in maintaining intestinal homeostasis and function, its involvement in facilitating intestinal recovery following ionizing radiation (IR) damage has not been fully elucidated. Here, we utilized in vivo and in vitro models to decipher the role of CUL4B in intestinal repair after IR-injury. Our findings demonstrated that prior to radiation exposure, CUL4B inhibited the ubiquitination modification of PSME3, which led to the accumulation of PSME3 and subsequent negative regulation of p53-mediated apoptosis. In contrast, after radiation, CUL4B dissociated from PSME3 and translocated into the nucleus at phosphorylated histones H2A (γH2AX) foci, thereby impeding DNA damage repair and augmenting p53-mediated apoptosis through inhibition of BRCA1 phosphorylation and RAD51. Our study elucidated the dynamic role of CUL4B in the repair of radiation-induced intestinal damage and uncovered novel molecular mechanisms underlying the repair process, suggesting a potential therapeutic strategy of intestinal damage after radiation therapy for cancers.

Cell fate regulation governed by p53: Friends or reversible foes in cancer therapy

Cancer is a leading cause of death worldwide. Targeted therapies aimed at key oncogenic driver mutations in combination with chemotherapy and radiotherapy as well as immunotherapy have benefited cancer patients considerably. Tumor protein p53 (TP53), a crucial tumor suppressor gene encoding p53, regulates numerous downstream genes and cellular phenotypes in response to various stressors. The affected genes are involved in diverse processes, including cell cycle arrest, DNA repair, cellular senescence, metabolic homeostasis, apoptosis, and autophagy. However, accumulating recent studies have continued to reveal novel and unexpected functions of p53 in governing the fate of tumors, for example, functions in ferroptosis, immunity, the tumor microenvironment and microbiome metabolism. Among the possibilities, the evolutionary plasticity of p53 is the most controversial, partially due to the dizzying array of biological functions that have been attributed to different regulatory mechanisms of p53 signaling. Nearly 40 years after its discovery, this key tumor suppressor remains somewhat enigmatic. The intricate and diverse functions of p53 in regulating cell fate during cancer treatment are only the tip of the iceberg with respect to its equally complicated structural biology, which has been painstakingly revealed. Additionally, TP53 mutation is one of the most significant genetic alterations in cancer, contributing to rapid cancer cell growth and tumor progression. Here, we summarized recent advances that implicate altered p53 in modulating the response to various cancer therapies, including chemotherapy, radiotherapy, and immunotherapy. Furthermore, we also discussed potential strategies for targeting p53 as a therapeutic option for cancer.

The Radiosensitizing Potentials of Silymarin/Silibinin in Cancer: A Systematic Review

INTRODUCTION

Although radiotherapy is one of the main cancer treatment modalities, exposing healthy organs/tissues to ionizing radiation during treatment and tumor resistance to ionizing radiation are the chief challenges of radiotherapy that can lead to different adverse effects. It was shown that the combined treatment of radiotherapy and natural bioactive compounds (such as silymarin/silibinin) can alleviate the ionizing radiation-induced adverse side effects and induce synergies between these therapeutic modalities. In the present review, the potential radiosensitization effects of silymarin/silibinin during cancer radiation exposure/radiotherapy were studied.

METHODS

According to the PRISMA guideline, a systematic search was performed for the identification of relevant studies in different electronic databases of Google Scholar, PubMed, Web of Science, and Scopus up to October 2022. We screened 843 articles in accordance with a predefined set of inclusion and exclusion criteria. Seven studies were finally included in this systematic review.

RESULTS

Compared to the control group, the cell survival/proliferation of cancer cells treated with ionizing radiation was considerably less, and silymarin/silibinin administration synergistically increased ionizing radiation-induced cytotoxicity. Furthermore, there was a decrease in the tumor volume, weight, and growth of ionizing radiation-treated mice as compared to the untreated groups, and these diminutions were predominant in those treated with radiotherapy plus silymarin/ silibinin. Furthermore, the irradiation led to a set of biochemical and histopathological changes in tumoral cells/tissues, and the ionizing radiation-induced alterations were synergized following silymarin/silibinin administration (in most cases).

CONCLUSION

In most cases, silymarin/silibinin administration could sensitize the cancer cells to ionizing radiation through an increase of free radical formation, induction of DNA damage, increase of apoptosis, inhibition of angiogenesis and metastasis, etc. However, suggesting the use of silymarin/silibinin during radiotherapeutic treatment of cancer patients requires further clinical studies.

Radioprotective efficacy of Astilbin in mitigating radiation-induced lung injury through inhibition of p53 acetylation

Radiation-induced lung injury (RILI) is a common side effect in thoracic tumor patients undergoing radiotherapy. At present, there is no ideal radio-protective agent which is widely used in RILI treatment. Astilbin (AST), a bioactive flavonoid, exhibits various biological effects, including anti-inflammatory, antioxidant, and anti-fibrotic activities, which partly result from reducing oxidative stress and inflammation in various pathogenic conditions. However, the protective efficacy of AST to ameliorate RILI has not been reported. In this study, we employed network pharmacology, RNA sequencing, and experimental evaluation to reveal the effects and pharmacological mechanism of AST to treat RILI in vivo and in vitro. We observed that AST reduced radiation-induced apoptosis, DNA damage, inflammatory reactions, and the reactive oxygen species (ROS) level in human normal lung epithelial cells BEAS-2B. Further study showed that AST treatment significantly ameliorated RILI by reducing the radiation-induced pathology changes and inflammatory reaction of lung tissue in C57BL/6J mice. Mechanistically, the expression of epithelial-mesenchymal transition (EMT) markers and radiation-triggered acetylation of the p53 protein were alleviated by AST treatment. Furthermore, AST alleviated the acetylation of p53 after intervention of Trichostatin A (TSA). Our data indicate that AST can alleviate RILI by inhibiting inflammatory reactions and the EMT process through decreasing the expression of p53 acetylation. In conclusion, our study suggests that AST has great potential to be a new protective and therapeutic compound for RILI.

Multimodality local ablative therapy of 23 lung metastases with surgical resection and percutaneous cryoablation in a patient with Li-Fraumeni Syndrome: A case report

Patients with Li-Fraumeni syndrome (LFS) are prone to develop a variety of malignancies due to insufficient activity of the encoded tumor suppressor protein P53, including adrenocortical carcinoma, breast cancer, lung cancer, pancreatic cancer, and sarcoma. In the setting of LFS, local treatment options for lung metastases are limited to surgery and thermal ablation since radiotherapy and some systemic therapies predispose patients to additional future malignancies. We present the case of a 45-year-old woman with LFS with leiomyosarcoma metastases to both lungs who underwent bilateral wedge resections to treat a total of eight lung metastases followed by six percutaneous cryoablation sessions to treat 15 additional lung metastases over a period of 24 months. Our case demonstrates the option of multimodal local ablative therapies for lung metastases in patients with LFS, including percutaneous cryoablation.

Epigenetics as a determinant of radiation response in cancer

Radiation therapy is a cornerstone of modern cancer treatment. Treatment is based on depositing focal radiation to the tumor to inhibit cell growth, proliferation and metastasis, and to promote the death of cancer cells. In addition, radiation also affects non-tumor cells in the tumor microenvironmental (TME). Radiation resistance of the tumor cells is the most common cause of treatment failure, allowing survival of cancer cell and subsequent tumor growing. Molecular radioresistance comprises genetic and epigenetic characteristics inherent in cancer cells, or characteristics acquired after exposure to radiation. Furthermore, cancer stem cells (CSCs) and non-tumor cells into the TME as stromal and immune cells have a role in promoting and maintaining radioresistant tumor phenotypes. Different regulatory molecules and pathways distinctive of radiation resistance include DNA repair, survival signaling and cell death pathways. Epigenetic mechanisms are one of the most relevant events that occur after radiotherapy to regulate the expression and function of key genes and proteins in the differential radiation-response. This article reviews recent data on the main molecular mechanisms and signaling pathways related to the biological response to radiotherapy in cancer; highlighting the epigenetic control exerted by DNA methylation, histone marks, chromatin remodeling and m6A RNA methylation on gene expression and activation of signaling pathways related to radiation therapy response.

Genetic markers associated with adverse reactions of radioiodine therapy in thyroid cancer patients

OBJECTIVES

Radioactive iodine therapy is considered for patients with certain clinicopathological factors that predict a significant risk of recurrence, distant metastases of thyroid cancer or disease-specific mortality. The aim of the study was to investigate the association between polymorphisms of genes, products of which are involved in the processes of DNA damage response and autophagy, and the adverse reactions of radioiodine therapy in thyroid cancer patients.

METHODS

The study included 181 patients (37 men, 144 women; median age 56 [41; 66.3] years) with histologically confirmed thyroid cancer and a history of thyroidectomy who received radioiodine therapy. NFKB1, ATM, ATG16L2, ATG10, TGFB1, and TNF polymorphisms were determined by allele-specific realtime-PCR.

RESULTS

The frequency of adverse reactions was the following: gastrointestinal symptoms - 57.9 %, local symptoms - 65.8 %, cerebral symptoms - 46.8 %, fatigue - 54.4 %; signs of sialoadenitis six months after radioiodine therapy - 25.2 %. TT genotype carriers of ATG10 rs1864183 had higher frequency of gastrointestinal symptoms (vs. CC+CT), the CC genotype carriers of ATG10 rs10514231 had significantly more frequent cerebral symptoms (vs. CT+TT), as well as AA genotype carriers of TGFB1 rs1800469 (vs. AG+GG). CC genotype of ATG10 rs10514231 increased the incidence of radioiodine-induced fatigue, whereas GA genotype of the ATM rs11212570 had a protective role against fatigue. TGFB1 rs1800469 was associated with signs of sialoadenitis six months after radioiodine therapy.

CONCLUSIONS

Genetic factors may contribute to the occurrence of adverse reactions of radioiodine therapy in thyroid cancer patients.

Elucidation of the anti-lung cancer mechanism of Juan-Liu-San-Jie prescription based on network pharmacology and experimental validation

Lung cancer is a malignancy characterized by high morbidity and mortality, with lung adenocarcinoma being the most prevalent subtype. Our preliminary studies have demonstrated that the Juan-Liu-San-Jie (JLSJ) prescription, a Traditional Chinese Medicine prescription, possesses anti-lung adenocarcinoma cancer properties. However, the molecular mechanism underlying the therapeutic effects of the JLSJ prescription for lung adenocarcinoma remains incompletely elucidated. To address the knowledge gap, the present study employed network pharmacology to identify potential therapeutic targets. Specifically, the study utilized TCMSP, TCMID, and related references, as well as ChemMapper, to identify and predict the main active components and potential targets. Additionally, differentially expressed genes associated with the disease were obtained from the microarray dataset GSE19804 and GSE118370. The protein-protein Interaction network and Target-pathway network were then constructed. We also conducted Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses, and subsequently presented the top 20 enriched pathways. The results indicated that the anti-lung cancer effects of JLSJ prescription may be attributed to its ability to mediate apoptosis of tumor cells, potentially through the PI3K/Akt signaling pathway. Then, a series of in vitro and in vivo experiments were conducted to validate the molecular mechanism predicted by network pharmacology. The findings of the in vivo study suggested that the JLSJ prescription could inhibit the growth of xenograft tumors of lung adenocarcinoma with fewer adverse effects. Also, the in vitro experiments corroborated that the JLSJ prescription could induce apoptosis of A549 cells. Furthermore, the upregulation of pro-apoptosis-related proteins and mRNAs, coupled with the downregulation of anti-apoptotic-related proteins and mRNAs, was observed. In conclusion, inducing apoptosis by inhibiting the PI3K/Akt signaling pathway was one of the underlying mechanisms by which the JLSJ prescription exerted its anti-lung adenocarcinoma effect.

Genetic markers associated with adverse reactions of radioiodine therapy in thyroid cancer patients

OBJECTIVES

Radioactive iodine therapy is considered for patients with certain clinicopathological factors that predict a significant risk of recurrence, distant metastases of thyroid cancer or disease-specific mortality. The aim of the study was to investigate the association between polymorphisms of genes, products of which are involved in the processes of DNA damage response and autophagy, and the adverse reactions of radioiodine therapy in thyroid cancer patients.

METHODS

The study included 181 patients (37 men, 144 women; median age 56 [41; 66.3] years) with histologically confirmed thyroid cancer and a history of thyroidectomy who received radioiodine therapy. NFKB1, ATM, ATG16L2, ATG10, TGFB1, and TNF polymorphisms were determined by allele-specific realtime-PCR.

RESULTS

The frequency of adverse reactions was the following: gastrointestinal symptoms - 57.9 %, local symptoms - 65.8 %, cerebral symptoms - 46.8 %, fatigue - 54.4 %; signs of sialoadenitis six months after radioiodine therapy - 25.2 %. TT genotype carriers of ATG10 rs1864183 had higher frequency of gastrointestinal symptoms (vs. CC+CT), the CC genotype carriers of ATG10 rs10514231 had significantly more frequent cerebral symptoms (vs. CT+TT), as well as AA genotype carriers of TGFB1 rs1800469 (vs. AG+GG). CC genotype of ATG10 rs10514231 increased the incidence of radioiodine-induced fatigue, whereas GA genotype of the ATM rs11212570 had a protective role against fatigue. TGFB1 rs1800469 was associated with signs of sialoadenitis six months after radioiodine therapy.

CONCLUSIONS

Genetic factors may contribute to the occurrence of adverse reactions of radioiodine therapy in thyroid cancer patients.

An integrative systems biology strategy to support the development of adverse outcome pathways (AOPs): a case study on radiation-induced microcephaly

Adverse Outcome Pathways (AOPs) are useful tools for assessing the potential risks associated with exposure to various stressors, including chemicals and environmental contaminants. They provide a framework for understanding the causal relationships between different biological events that can lead to adverse outcomes (AO). However, developing an AOP is a challenging task, particularly in identifying the molecular initiating events (MIEs) and key events (KEs) that constitute it. Here, we propose a systems biology strategy that can assist in the development of AOPs by screening publicly available databases, literature with the text mining tool AOP-helpFinder, and pathway/network analyses. This approach is straightforward to use, requiring only the name of the stressor and adverse outcome to be studied. From this, it quickly identifies potential KEs and literature providing mechanistic information on the links between the KEs. The proposed approach was applied to the recently developed AOP 441 on radiation-induced microcephaly, resulting in the confirmation of the KEs that were already present and identification of new relevant KEs, thereby validating the strategy. In conclusion, our systems biology approach represents a valuable tool to simplify the development and enrichment of Adverse Outcome Pathways (AOPs), thus supporting alternative methods in toxicology.

Prevalence, causes and impact of TP53-loss phenocopying events in human tumors

BACKGROUND

TP53 is a master tumor suppressor gene, mutated in approximately half of all human cancers. Given the many regulatory roles of the corresponding p53 protein, it is possible to infer loss of p53 activity - which may occur due to alterations in trans - from gene expression patterns. Several such alterations that phenocopy p53 loss are known, however additional ones may exist, but their identity and prevalence among human tumors are not well characterized.

RESULTS

We perform a large-scale statistical analysis on transcriptomes of ~ 7,000 tumors and ~ 1,000 cell lines, estimating that 12% and 8% of tumors and cancer cell lines, respectively, phenocopy TP53 loss: they are likely deficient in the activity of the p53 pathway, while not bearing obvious TP53 inactivating mutations. While some of these cases are explained by amplifications in the known phenocopying genes MDM2, MDM4 and PPM1D, many are not. An association analysis of cancer genomic scores jointly with CRISPR/RNAi genetic screening data identified an additional common TP53-loss phenocopying gene, USP28. Deletions in USP28 are associated with a TP53 functional impairment in 2.9-7.6% of breast, bladder, lung, liver and stomach tumors, and have comparable effect size to MDM4 amplifications. Additionally, in the known copy number alteration (CNA) segment harboring MDM2, we identify an additional co-amplified gene (CNOT2) that may cooperatively boost the TP53 functional inactivation effect of MDM2. An analysis of cancer cell line drug screens using phenocopy scores suggests that TP53 (in)activity commonly modulates associations between anticancer drug effects and various genetic markers, such as PIK3CA and PTEN mutations, and should thus be considered as a drug activity modifying factor in precision medicine. As a resource, we provide the drug-genetic marker associations that differ depending on TP53 functional status.

CONCLUSIONS

Human tumors that do not bear obvious TP53 genetic alterations but that phenocopy p53 activity loss are common, and the USP28 gene deletions are one likely cause.

Aging microenvironment and antitumor immunity for geriatric oncology: the landscape and future implications

The tumor microenvironment (TME) has been extensively investigated; however, it is complex and remains unclear, especially in elderly patients. Senescence is a cellular response to a variety of stress signals, which is characterized by stable arrest of the cell cycle and major changes in cell morphology and physiology. To the best of our knowledge, senescence leads to consistent arrest of tumor cells and remodeling of the tumor-immune microenvironment (TIME) by activating a set of pleiotropic cytokines, chemokines, growth factors, and proteinases, which constitute the senescence-associated secretory phenotype (SASP). On the one hand, the SASP promotes antitumor immunity, which enhances treatment efficacy; on the other hand, the SASP increases immunosuppressive cell infiltration, including myeloid-derived suppressor cells (MDSCs), regulatory T cells (Tregs), M2 macrophages, and N2 neutrophils, contributing to TIME suppression. Therefore, a deeper understanding of the regulation of the SASP and components contributing to robust antitumor immunity in elderly individuals with different cancer types and the available therapies is necessary to control tumor cell senescence and provide greater clinical benefits to patients. In this review, we summarize the key biological functions mediated by cytokines and intercellular interactions and significant components of the TME landscape, which influence the immunotherapy response in geriatric oncology. Furthermore, we summarize recent advances in clinical practices targeting TME components and discuss potential senescent TME targets.

The role of truncated p53 isoforms in the DNA damage response

The tumour suppressor p53 is activated following genotoxic stress and regulates the expression of target genes involved in the DNA damage response (DDR). The discovery that p53 isoforms alter the transcription of p53 target genes or p53 protein interactions unveiled an alternative DDR. This review will focus on the role p53 isoforms play in response to DNA damage. The expression of the C-terminally truncated p53 isoforms may be modulated via DNA damage-induced alternative splicing, whereas alternative translation plays an important role in modulating the expression of N-terminally truncated isoforms. The DDR induced by p53 isoforms may enhance the canonical p53 DDR or block cell death mechanisms in a DNA damage- and cell-specific manner, which could contribute to chemoresistance in a cancer context. Thus, a better understanding of the involvement of p53 isoforms in the cell fate decisions could uncover potential therapeutic targets in cancer and other diseases.

Characterization of cellular senescence patterns predicts the prognosis and therapeutic response of hepatocellular carcinoma

Background: Hepatocellular carcinoma (HCC) is a prevalent malignancy with a high mortality rate. Cellular senescence, an irreversible state of cell cycle arrest, plays a paradoxical role in cancer progression. Here, we aimed to identify Hepatocellular carcinoma subtypes by cellular senescence-related genes (CSGs) and to construct a cellular senescence-related gene subtype predictor as well as a novel prognostic scoring system, which was expected to predict clinical outcomes and therapeutic response of Hepatocellular carcinoma. Methods: RNA-seq data and clinical information of Hepatocellular carcinoma patients were derived from The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC). The "multi-split" selection was used to screen the robust prognostic cellular senescence-related genes. Unsupervised clustering was performed to identify CSGs-related subtypes and a discriminant model was obtained through multiple statistical approaches. A CSGs-based prognostic model-CSGscore, was constructed by LASSO-Cox regression and stepwise regression. Immunophenoscore (IPS) and Tumor Immune Dysfunction and Exclusion (TIDE) were utilized to evaluate the immunotherapy response. Tumor stemness indices mRNAsi and mDNAsi were used to analyze the relationship between CSGscore and stemness. Results: 238 robust prognostic differentially expressed cellular senescence-related genes (DECSGs) were used to categorize all 336 hepatocellular carcinoma patients of the TCGA-LIHC cohort into two groups with different survival. Two hub genes, TOP2A and KIF11 were confirmed as key indicators and were used to form a precise and concise cellular senescence-related gene subtype predictor. Five genes (PSRC1, SOCS2, TMEM45A, CCT5, and STC2) were selected from the TCGA training dataset to construct the prognostic CSGscore signature, which could precisely predict the prognosis of hepatocellular carcinoma patients both in the training and validation datasets. Multivariate analysis verified it as an independent prognostic factor. Besides, CSGscore was also a valuable predictor of therapeutic responses in hepatocellular carcinoma. More downstream analysis revealed the signature genes were significantly associated with stemness and tumor progression. Conclusion: Two subtypes with divergent outcomes were identified by prognostic cellular senescence-related genes and based on that, a subtype indicator was established. Moreover, a prognostic CSGscore system was constructed to predict the survival outcomes and sensitivity of therapeutic responses in hepatocellular carcinoma, providing novel insight into hepatocellular carcinoma biomarkers investigation and design of tailored treatments depending on the molecular characteristics of individual patients.

p53 Modulates Radiosensitivity in Head and Neck Cancers-From Classic to Future Horizons

p53, initially considered a tumor suppressor, has been the subject of research related to cancer treatment resistance in the last 30 years. The unfavorable response to multimodal therapy and the higher recurrence rate, despite an aggressive approach, make HNSCC a research topic of interest for improving therapeutic outcomes, even if it is only the sixth most common malignancy worldwide. New advances in molecular biology and genetics include the involvement of miRNA in the control of the p53 pathway, the understanding of mechanisms such as gain/loss of function, and the development of different methods to restore p53 function, especially for HPV-negative cases. The different ratio between mutant p53 status in the primary tumor and distant metastasis originating HNSCC may serve to select the best therapeutic target for activating an abscopal effect by radiotherapy as a "booster" of the immune system. P53 may also be a key player in choosing radiotherapy fractionation regimens. Targeting any pathway involving p53, including tumor metabolism, in particular the Warburg effect, could modulate the radiosensitivity and chemo-sensitivity of head and neck cancers.

Utility of melatonin in mitigating ionizing radiation-induced testis injury through synergistic interdependence of its biological properties

Background

Ionizing radiations (IR) have widespread useful applications in our daily life; however, they have unfavorable effects on reproductive health. Maintaining testicular health following IR exposure is an important requirement for reproductive potential. The current study explored the role of melatonin (MLT) in mitigating IR-induced injury in young adult rat testis.

Methods

Rats were given daily MLT (25 mg/kg) for 3 and 14 days after receiving 4 Gy γ-radiation.

Results

Serum MLT levels and other antioxidants, including glutathione content, and the activity of glutathione peroxidase and glutathione reductase in the testis of the irradiated rats were remarkably maintained by MLT administration in irradiated rats. Hence, the hydrogen peroxide level declined with remarkably reduced formation of oxidative stress markers, 4-hydroxynonenal, and 8-Hydroxy-2′-deoxyguanosine in the testis of irradiated animals after MLT administration. The redox status improvement caused a remarkable regression of proapoptotic protein (p53, Cyto-c, and caspase-3) in the testis and improved inflammatory cytokines (CRP and IL-6), and anti-inflammatory cytokine (interleukin IL-10) in serum. This is associated with restoration of disturbed sex hormonal balance, androgen receptor upregulation, and testicular cell proliferation activity in irradiated rats, explaining the improvement of sperm parameters (count, motility, viability, and deformation). Consequently, spermatogenic cell depletion and decreased seminiferous tubule diameter and perimeter were attenuated by MLT treatment post irradiation. Moreover, the testis of irradiated-MLT-treated rats showed well-organized histological architecture and normal sperm morphology.

Conclusions

These results show that radiation-induced testicular injury is mitigated following IR exposure through synergistic interdependence between the antioxidant, anti-inflammatory, anti-apoptotic, and anti-DNA damage actions of MLT.

Molecular Targeting of the Most Functionally Complex Gene in Precision Oncology: p53

While chemotherapy is a key treatment strategy for many solid tumors, it is rarely curative, and most tumor cells eventually become resistant. Because of this, there is an unmet need to develop systemic treatments that capitalize on the unique mutational landscape of each patient's tumor. The most frequently mutated protein in cancer, p53, has a role in nearly all cancer subtypes and tumorigenesis stages and therefore is one of the most promising molecular targets for cancer treatment. Unfortunately, drugs targeting p53 have seen little clinical success despite promising preclinical data. Most of these drug compounds target specific aspects of p53 inactivation, such as through inhibiting negative regulation by the mouse double minute (MDM) family of proteins. These treatment strategies fail to address cancer cells' adaptation mechanisms and ignore the impact that p53 loss has on the entire p53 network. However, recent gene therapy successes show that targeting the p53 network and cellular dysfunction caused by p53 inactivation is now possible and may soon translate into successful clinical responses. In this review, we discuss p53 signaling complexities in cancer that have hindered the development and use of p53-targeted drugs. We also describe several current therapeutics reporting promising preclinical and clinical results.

Differential responses to 223Ra and Alpha-particles exposure in prostate cancer driven by mitotic catastrophe

Introduction

Radium-223 (223Ra) has been shown to have an overall survival benefit in metastatic castration-resistant prostate cancer (mCRPC) involving bone. Despite its increased clinical usage, relatively little is known regarding the mechanism of action of 223Ra at the cellular level.

Methods

We evaluated the effects of 223Ra irradiation in a panel of cell lines and then compared them with standard X-ray and external alpha-particle irradiation, with a particular focus on cell survival and DNA damage repair kinetics.

Results

223Ra exposures had very high, cell-type-dependent RBE50% ranging from 7 to 15. This was significantly greater than external alpha irradiations (RBE50% from 1.4 to 2.1). These differences were shown to be partially related to the volume of 223Ra solution added, independent of the alpha-particle dose rate, suggesting a radiation-independent mechanism of effect. Both external alpha particles and 223Ra exposure were associated with delayed DNA repair, with similar kinetics. Additionally, the greater treatment efficacy of 223Ra was associated with increased levels of residual DNA damage and cell death by mitotic catastrophe.

Conclusions

These results suggest that 223Ra exposure may be associated with greater biological effects than would be expected by direct comparison with a similar dose of external alpha particles, highlighting important challenges for future therapeutic optimization.

Exploiting senescence for the treatment of cancer

Senescence is a cellular response to a variety of stress signals that is characterized by a stable withdrawal from the cell cycle and major changes in cell morphology and physiology. While most research on senescence has been performed on non-cancer cells, it is evident that cancer cells can also mount a senescence response. In this Review, we discuss how senescence can be induced in cancer cells. We describe the distinctive features of senescent cancer cells and how these changes in cellular physiology might be exploited for the selective eradication of these cells (senolysis). We discuss activation of the host immune system as a particularly attractive way to clear senescent cancer cells. Finally, we consider the challenges and opportunities provided by a 'one-two punch' sequential treatment of cancer with pro-senescence therapy followed by senolytic therapy.

PARP inhibitor olaparib enhances the efficacy of radiotherapy on XRCC2-deficient colorectal cancer cells

The use of PARP inhibitors in combination with radiotherapy is a promising strategy to locally enhance DNA damage in tumors. Loss of XRCC2 compromises DNA damage repairs, and induced DNA damage burdens may increase the reliance on PARP-dependent DNA repairs of cancer cells to render cell susceptibility to PARP inhibitor therapy. Here we tested the hypothesis that XRCC2 loss sensitizes colorectal cancer (CRC) to PARP inhibitor in combination with radiotherapy (RT). We show that high levels of XRCC2 or PARP1 in LARC patients were significantly associated with poor overall survival (OS). Co-expression analyses found that low levels of PARP1 and XRCC2 were associated with better OS. Our in vitro experiments indicated that olaparib+IR led to reduced clonogenic survival, more DNA damage, and longer durations of cell cycle arrest and senescence in XRCC2-deficient cells relative to wild-type cells. Furthermore, our mouse xenograft experiments indicated that RT + olaparib had greater anti-tumor effects and led to long-term remission in mice with XRCC2-deficient tumors. These findings suggest that XRCC2-deficient CRC acquires high sensitivity to PARP inhibition after IR treatment and supports the clinical development for the use of olaparib as a radiosensitizer for treatment of XRCC2-deficient CRC.

Hyaluronic Acid: Known for Almost a Century, but Still in Vogue

Hyaluronic acid (HA) has a special position among glycosaminoglycans. As a major component of the extracellular matrix (ECM). This simple, unbranched polysaccharide is involved in the regulation of various biological cell processes, whether under physiological conditions or in cases of cell damage. This review summarizes the history of this molecule's study, its distinctive metabolic pathway in the body, its unique properties, and current information regarding its interaction partners. Our main goal, however, is to intensively investigate whether this relatively simple polymer may find applications in protecting against ionizing radiation (IR) or for therapy in cases of radiation-induced damage. After exposure to IR, acute and belated damage develops in each tissue depending upon the dose received and the cellular composition of a given organ. A common feature of all organ damage is a distinct change in composition and structure of the ECM. In particular, the important role of HA was shown in lung tissue and the variability of this flexible molecule in the complex mechanism of radiation-induced lung injuries. Moreover, HA is also involved in intermediating cell behavior during morphogenesis and in tissue repair during inflammation, injury, and would healing. The possibility of using the HA polymer to affect or treat radiation tissue damage may point to the missing gaps in the responsible mechanisms in the onset of this disease. Therefore, in this article, we will also focus on obtaining answers from current knowledge and the results of studies as to whether hyaluronic acid can also find application in radiation science.

Recent advances in radiosensitivity determinants in melanoma

PURPOSE OF REVIEW

Radiotherapy has been proven to be useful but insufficient in melanoma management due to the intrinsic radioresistance of melanoma cells. Elucidation of the molecular mechanisms and pathways related to resistance/sensitivity to radiotherapy in melanoma is of paramount importance. In this review, we will summarize and discuss the recent 'discoveries' and advances in radiosensitivity determinants in melanoma.

RECENT FINDINGS

The different levels of radiosensitivity among the various melanoma tumors could be attributed to the DNA damage signaling and repair proteins, tumor microenvironment, hypoxia, cell metabolism, glutathione and redox balance, protein kinase signaling pathways as well as pigmentation and melanin content.

SUMMARY

It is therapeutically important to elucidate the factors involved in radiation resistance/sensitivity of melanoma. More importantly, improving radiosensitivity may 'widen the clinical utility' in melanoma of this important therapeutic modality.

Radiation-induced C-reactive protein triggers apoptosis of vascular smooth muscle cells through ROS interfering with the STAT3/Ref-1 complex

Damage to normal tissue can occur over a long period after cancer radiotherapy. Free radical by radiation can initiate or accelerate chronic inflammation, which can lead to atherosclerosis. However, the underlying mechanisms remain unclear. Vascular smooth muscle cells (VSMCs) proliferate in response to JAK/STAT3 signalling. C-reactive protein (CRP) can induce VSMCs apoptosis via triggering NADPH oxidase (NOX). Apoptotic VSMCs promote instability and inflammation of atherosclerotic lesions. Herein, we identified a VSMCs that switched from proliferation to apoptosis through was enhanced by radiation-induced CRP. NOX inhibition using lentiviral sh-p22^phox prevented apoptosis upon radiation-induced CRP. CRP overexpression reduced the amount of STAT3/Ref-1 complex, decreased JAK/STAT phosphorylation and formed a new complex of Ref-1/CRP in VSMC. Apoptosis of VSMCs was further increased by CRP co-overexpressed with Ref-1. Functional inhibition of NOX or p53 also prevented apoptotic activity of the CRP-Ref-1 complex. Immunofluorescence showed co-localization of CRP, Ref-1 and p53 with α-actin-positive VSMC in human atherosclerotic plaques. In conclusion, radiation-induced CRP increased the VSMCs apoptosis through Ref-1, which dissociated the STAT3/Ref-1 complex, interfered with JAK/STAT3 activity, and interacted with CRP-Ref-1, thus resulting in transcription-independent cell death via p53. Targeting CRP as a vascular side effect of radiotherapy could be exploited to improve curability.

Advances in the Current Understanding of How Low-Dose Radiation Affects the Cell Cycle

Cells exposed to ionizing radiation undergo a series of complex responses, including DNA damage, reproductive cell death, and altered proliferation states, which are all linked to cell cycle dynamics. For many years, a great deal of research has been conducted on cell cycle checkpoints and their regulators in mammalian cells in response to high-dose exposures to ionizing radiation. However, it is unclear how low-dose ionizing radiation (LDIR) regulates the cell cycle progression. A growing body of evidence demonstrates that LDIR may have profound effects on cellular functions. In this review, we summarize the current understanding of how LDIR (of up to 200 mGy) regulates the cell cycle and cell-cycle-associated proteins in various cellular settings. In light of current findings, we also illustrate the conceptual function and possible dichotomous role of p21^Waf1, a transcriptional target of p53, in response to LDIR.

Radiotherapy and radiosensitization in breast cancer: Molecular targets and clinical applications

Relatively poor survival outcomes are observed in advanced or metastatic breast cancer, where local control of the primary or metastatic disease may be achieved by surgical resection, local ablative and radiation therapies. Radioresistance, poses a major challenge in achieving durable oncologic outcomes, mandating development of novel management strategies. Although multimodality approaches that combine radiotherapy with chemotherapy, or systemic agents, are utilized for radiosensitization and treatment of various malignancies, this approach has not yet found its clinical application in breast cancer. Some agents for breast cancer treatment can serve as radiosensitizers, creating an opportunity to enhance effects of radiation while providing systemic disease control. Hence, combination of radiotherapy with radiosensitizing agents have the potential to improve oncologic outcomes in advanced or metastatic breast cancer. This review discusses molecular targets for radiosensitization and novel systemic agents that have potential for clinical use as radiosensitizers in breast cancer.

Focal Point of Fanconi Anemia Signaling

Among human genetic diseases, Fanconi Anemia (FA) tops all with its largest number of health complications in nearly all human organ systems, suggesting the significant roles played by FA genes in the maintenance of human health. With the accumulated research on FA, the encoded protein products by FA genes have been building up to the biggest cell defense signaling network, composed of not only 22+ FA proteins but also ATM, ATR, and many other non-FA proteins. The FA D2 group protein (FANCD2) and its paralog form the focal point of FA signaling to converge the effects of its upstream players in response to a variety of cellular insults and simultaneously with downstream players to protect humans from contracting diseases, including aging and cancer. In this review, we update and discuss how the FA signaling crucially eases cellular stresses through understanding its focal point.

Effects of radiation on tumor vasculature

Radiation has been utilized as a direct cytotoxic tumorcidal modality, however, the effect of radiation on tumor vasculature influences response to anticancer therapies. Although numerous reports have demonstrated vascular changes in irradiated tumors, the findings and implications are extensive and at times contradictory depending on the radiation dose, timing, and models used. In this review, we focus on the radiation-mediated effects on tumor vasculature with respect to doses used, timing postradiation, vasculogenesis, adhesion molecule expression, permeability, and pericyte coverage, including the latest findings.

Inhibition of nonsense-mediated decay rescues p53β/γ isoform expression and activates the p53 pathway in MDM2-overexpressing and select p53-mutant cancers

Inactivation of p53 is present in almost every tumor, and hence, p53-reactivation strategies are an important aspect of cancer therapy. Common mechanisms for p53 loss in cancer include expression of p53-negative regulators such as MDM2, which mediate the degradation of wildtype p53 (p53α), and inactivating mutations in the TP53 gene. Currently, approaches to overcome p53 deficiency in these cancers are limited. Here, using non–small cell lung cancer and glioblastoma multiforme cell line models, we show that two alternatively spliced, functional truncated isoforms of p53 (p53β and p53γ, comprising exons 1 to 9β or 9γ, respectively) and that lack the C-terminal MDM2-binding domain have markedly reduced susceptibility to MDM2-mediated degradation but are highly susceptible to nonsense-mediated decay (NMD), a regulator of aberrant mRNA stability. In cancer cells harboring MDM2 overexpression or TP53 mutations downstream of exon 9, NMD inhibition markedly upregulates p53β and p53γ and restores activation of the p53 pathway. Consistent with p53 pathway activation, NMD inhibition induces tumor suppressive activities such as apoptosis, reduced cell viability, and enhanced tumor radiosensitivity, in a relatively p53-dependent manner. In addition, NMD inhibition also inhibits tumor growth in a MDM2-overexpressing xenograft tumor model. These results identify NMD inhibition as a novel therapeutic strategy for restoration of p53 function in p53-deficient tumors bearing MDM2 overexpression or p53 mutations downstream of exon 9, subgroups that comprise approximately 6% of all cancers.

Osteosarcoma of the sternum after radiotherapy for breast cancer in a patient with suspected hereditary cancer syndrome: a case report

Introduction:

Radiation-induced malignancies are a rare phenomenon. Post-radiation sarcoma accounts for 0·5–5·5% of all sarcomas. Adjuvant radiotherapy (RT) after surgery plays a significant role in the treatment of breast cancer. Sarcomas of the breast, chest wall, sternum, axilla or supraclavicular region have been reported as a rare complication of RT for breast cancer. Osteosarcoma (OS) of the sternal bone is a rarely reported entity. OS of the sternum secondary to therapeutic ionising radiation is an even rarer diagnosis, and no such cases have been reported in India as per our literature search. Here we report such a case of post-radiation sarcoma after breast cancer treatment—OS presenting in the sternum and both the second ribs in a young lady.

Findings:

Our patient developed a sarcoma within a previously irradiated field. The latent period was 7·5 years. She initially suffered from a breast carcinoma for which she underwent radical surgery in the form of modified radical mastectomy. She also received 50 Gy RT dose to the chest wall and axilla. She subsequently developed an OS of chest wall in the high-dose region of RT. Another key factor is the high possibility of familial/hereditary cancer inheritance syndrome like Li-Fraumeni in our patient. Though she was never tested for p53 mutations, her young age at first diagnosis (26 years), extremely strong positive family history and spectra of cancers affecting her first-degree blood relatives (brain tumours, leukaemia) strongly hint at the possibility of such a cancer syndrome. Retrospectively, the question certainly arises, given her young age and family history, whether this patient was a right candidate for RT even once as compared to the fact that she received radiation twice.

Relationship between p53 status and the bioeffect of ionizing radiation

Radiotherapy is widely used in the clinical treatment of cancer patients and it may be used alone or in combination with surgery or chemotherapy to inhibit tumor development. However, radiotherapy may at times not kill all cancer cells completely, as certain cells may develop radioresistance that counteracts the effects of radiation. The emergence of radioresistance is associated with the genetic background and epigenetic regulation of cells. p53 is an important tumor suppressor gene that is expressed at low levels in cells. However, when cells are subjected to stress-induced stimulation, the expression level of p53 increases, thereby preventing genomic disruption. This mechanism has important roles in maintaining cell stability and inhibiting carcinogenesis. However, mutation and deletion destroy the anticancer function of p53 and may induce carcinogenesis. In tumor radiotherapy, the status of p53 expression in cancer cells has a close relationship with radiotherapeutic efficacy. Therefore, understanding how p53 expression affects the cellular response to radiation is of great significance for solving the problem of radioresistance and improving radiotherapeutic outcomes. For the present review, the literature was searched for studies published between 1979 and 2021 using the PubMed database (https://pubmed.ncbi.nlm.nih.gov/) with the following key words: Wild-type p53, mutant-type p53, long non-coding RNA, microRNA, gene mutation, radioresistance and radiosensitivity. From the relevant studies retrieved, the association between different p53 mutants and cellular radiosensitivity, as well as the molecular mechanisms of p53 affecting the radiosensitivity of cells, were summarized. The aim of the present study was to provide useful information for understanding and resolving radioresistance, to help clinical researchers develop more accurate treatment strategies and to improve radiotherapeutic outcomes for cancer patients with p53 mutations.

The p53 Protein Family in the Response of Tumor Cells to Ionizing Radiation: Problem Development

Survival mechanisms are activated in tumor cells in response to therapeutic ionizing radiation. This reduces a treatment's effectiveness. The p53, p63, and p73 proteins belonging to the family of proteins that regulate the numerous pathways of intracellular signal transduction play a key role in the development of radioresistance. This review analyzes the p53-dependent and p53-independent mechanisms involved in overcoming the resistance of tumor cells to radiation exposure.

Radiopotentiation Profiling of Multiple Inhibitors of the DNA Damage Response for Early Clinical Development

Radiotherapy is an effective anticancer treatment, but combinations with targeted agents that maximize efficacy while sparing normal tissue are needed. Here, we assess the radiopotentiation profiles of DNA damage response inhibitors (DDRi) olaparib (PARP1/2), ceralasertib (ATR), adavosertib (WEE1), AZD0156 (ATM), and KU-60648 (DNA-PK). We performed a radiotherapy combination screen and assessed how drug concentration and cellular DDR deficiencies influence the radiopotentiation ability of DDRi. We pre-selected six lung cancer cell lines with different genetic/signaling aberrations (including mutations in TP53 and ATM) and assessed multiple concentrations of DDRi in combination with a fixed radiotherapy dose by clonogenic assay. The effective concentration of DDRi in radiotherapy combinations is lower than that required for single-agent efficacy. This has the potential to be exploited further in the context of DDR deficiencies to increase therapeutic index and we demonstrate that low concentrations of AZD0156 preferentially sensitized p53-deficient cells. Moreover, testing multiple concentrations of DDRi in radiotherapy combinations indicated that olaparib, ceralasertib, and adavosertib have a desirable safety profile showing moderate increases in radiotherapy dose enhancement with increasing inhibitor concentration. Small increases in concentration of AZD0156 and particularly KU-60648, however, result in steep increases in dose enhancement. Radiopotentiation profiling can inform on effective drug doses required for radiosensitization in relation to biomarkers, providing an opportunity to increase therapeutic index. Moreover, multiple concentration testing demonstrates a relationship between drug concentration and radiotherapy effect that provides valuable insights that, with future in vivo validation, can guide dose-escalation strategies in clinical trials.

Mutant p53 Mediates Sensitivity to Cancer Treatment Agents in Oesophageal Adenocarcinoma Associated with MicroRNA and SLC7A11 Expression

TP53 gene mutations occur in 70% of oesophageal adenocarcinomas (OACs). Given the central role of p53 in controlling cellular response to therapy we investigated the role of mutant (mut-) p53 and SLC7A11 in a CRISPR-mediated JH-EsoAd1 TP53 knockout model. Response to 2 Gy irradiation, cisplatin, 5-FU, 4-hydroxytamoxifen, and endoxifen was assessed, followed by a TaqMan OpenArray qPCR screening for differences in miRNA expression. Knockout of mut-p53 resulted in increased chemo- and radioresistance (2 Gy survival fraction: 38% vs. 56%, p < 0.0001) and in altered miRNA expression levels. Target mRNA pathways analyses indicated several potential mechanisms of treatment resistance. SLC7A11 knockdown restored radiosensitivity (2 Gy SF: 46% vs. 73%; p = 0.0239), possibly via enhanced sensitivity to oxidative stress. Pathway analysis of the mRNA targets of differentially expressed miRNAs indicated potential involvement in several pathways associated with apoptosis, ribosomes, and p53 signaling pathways. The data suggest that mut-p53 in JH-EsoAd1, despite being classified as non-functional, has some function related to radio- and chemoresistance. The results also highlight the important role of SLC7A11 in cancer metabolism and redox balance and the influence of p53 on these processes. Inhibition of the SLC7A11-glutathione axis may represent a promising approach to overcome resistance associated with mut-p53.

Oropharyngeal squamous cell carcinoma: p16/p53 immunohistochemistry as a strong predictor of HPV tumour status

AIMS

Oropharyngeal squamous cell carcinomas (OPSCC) related to human papillomavirus (HPV) infection have a better prognosis than those without HPV infection. Although p16^INK4a overexpression is used as a surrogate marker for HPV infection, 5-20% of p16-positive OPSCC are described as being unrelated to HPV infection, with worse overall survival compared to OPSCC-related HPV. There is therefore a risk of undertreating a proportion of OPSCC patients falsely considered to be HPV-driven because of p16 positivity. TP53 mutations are highly prevalent in OPSCC driven by mutagens in tobacco and alcohol. We describe herein a combined p16/p53 algorithm to predict HPV tumour status in OPSCC.

METHODS AND RESULTS

A total of 110 OPSCC were identified in the database of the pathology department and were studied using p16 and p53 immunohistochemistry. For p16-positive or p16-negative/wild-type patterns-p53 (WT-p53) cases (n = 63), DNA in-situ hybridisation for high-risk HPV was performed, and if negative the HPV status was controlled by HPV DNA polymerase chain reaction (PCR) (n = 19). A significant association between TP53 mutation and pattern of p53 expression was found (WT-p53, seven of 16, P < 0.001). The p16-positive/WT-p53 was significantly associated with HPV⁺ tumour status (p16-positive/WT-p53, 50 of 110, P < 0.001). Interestingly, a subset of p16-positive OPSCC was unrelated to HPV (13.5%, eight of 59), and showed mutant-type staining of p53 expression.

CONCLUSIONS

The p16 protein immunopositivity in conjunction with the mutant-type pattern of p53 staining helped to reclassify a subset of p16-positive OPSCC as OPSCC-unrelated HPV. This approach could be routinely applied by pathologists involved in the management of OPSCC, because of their potential therapeutic implications.

Ferroptosis as a mechanism to mediate p53 function in tumor radiosensitivity

Ferroptosis, a form of regulated cell death triggered by lipid peroxidation, was recently identified as an important mechanism in radiotherapy (RT)-mediated tumor suppression and radioresistance, although the exact genetic contexts in which to target ferroptosis in RT remains to be defined. p53 is the most commonly mutated gene in human cancers and a major effector to RT. Here, we identify ferroptosis as a critical mechanism to mediate p53 function in tumor radiosensitivity. Mechanistically, RT-mediated p53 activation antagonizes RT-induced SLC7A11 expression and represses glutathione synthesis, thereby promoting RT-induced lipid peroxidation and ferroptosis. p53 deficiency promotes radioresistance in cancer cells or tumors at least partly through SLC7A11-mediated ferroptosis inhibition. Ferroptosis inducers (FINs) that inhibit SLC7A11 exert significant radiosensitizing effects in tumor organoids and patient-derived xenografts with p53 mutation or deficiency. Finally, we show that RT-induced ferroptosis correlates with p53 activation and better clinical outcomes to RT in cancer patients. Together, our study uncovers a previously unappreciated role of ferroptosis in p53-mediated radiosensitization and suggest using FINs in combination with RT to treat p53-mutant cancers.

Ferroptosis, radiotherapy, and combination therapeutic strategies

Ferroptosis, an iron-dependent form of regulated cell death driven by peroxidative damages of polyunsaturated-fatty-acid-containing phospholipids in cellular membranes, has recently been revealed to play an important role in radiotherapy-induced cell death and tumor suppression, and to mediate the synergy between radiotherapy and immunotherapy. In this review, we summarize known as well as putative mechanisms underlying the crosstalk between radiotherapy and ferroptosis, discuss the interactions between ferroptosis and other forms of regulated cell death induced by radiotherapy, and explore combination therapeutic strategies targeting ferroptosis in radiotherapy and immunotherapy. This review will provide important frameworks for future investigations of ferroptosis in cancer therapy.

The CD44high Subpopulation of Multifraction Irradiation-Surviving NSCLC Cells Exhibits Partial EMT-Program Activation and DNA Damage Response Depending on Their p53 Status

Ionizing radiation (IR) is used for patients diagnosed with unresectable non-small cell lung cancer (NSCLC). However, radiotherapy remains largely palliative due to the survival of specific cell subpopulations. In the present study, the sublines of NSCLC cells, A549IR (p53wt) and H1299IR (p53null) survived multifraction X-ray radiation exposure (MFR) at a total dose of 60 Gy were investigated three weeks after the MFR course. We compared radiosensitivity (colony formation), expression of epithelial-mesenchymal transition (EMT) markers, migration activity, autophagy, and HR-dependent DNA double-strand break (DSB) repair in the bulk and entire CD44high/CD166high CSC-like populations of both parental and MFR survived NSCLC cells. We demonstrated that the p53 status affected: the pattern of expression of N-cadherin, E-cadherin, Vimentin, witnessing the appearance of EMT-like phenotype of MFR-surviving sublines; 1D confined migratory behavior (wound healing); the capability of an irradiated cell to continue to divide and form a colony of NSCLC cells before and after MFR; influencing the CD44/CD166 expression level in MFR-surviving NSCLC cells after additional single irradiation. Our data further emphasize the impact of p53 status on the decay of γH2AX foci and the associated efficacy of the DSB repair in NSCLC cells survived after MFR. We revealed that Rad51 protein might play a principal role in MFR-surviving of p53 null NSCLC cells promoting DNA DSB repair by homologous recombination (HR) pathway. The proportion of Rad51 + cells elevated in CD44high/CD166high population in MFR-surviving p53wt and p53null sublines and their parental cells. The p53wt ensures DNA-PK-mediated DSB repair for both parental and MFR-surviving cells irrespectively of a subsequent additional single irradiation. Whereas in the absence of p53, a dose-dependent increase of DNA-PK-mediated non-homologous end joining (NHEJ) occurred as an early post-irradiation response is more intensive in the CSC-like population MFR-surviving H1299IR, compared to their parental H1299 cells. Our study strictly observed a significantly higher content of LC3 + cells in the CD44high/CD166high populations of p53wt MFR-surviving cells, which enriched the CSC-like cells in contrast to their p53null counterparts. The additional 2 Gy and 5 Gy X-ray exposure leads to the dose-dependent increase in the proportion of LC3 + cells in CD44high/CD166high population of both parental p53wt and p53null, but not MFR-surviving NSCLC sublines. Our data indicated that autophagy is not necessarily associated with CSC-like cells’ radiosensitivity, emphasizing that careful assessment of other milestone processes (such as senescence and autophagy-p53-Zeb1 axis) of primary radiation responses may provide new potential targets modulated for therapeutic benefit through radiosensitizing cancer cells while rescuing normal tissue. Our findings also shed light on the intricate crosstalk between autophagy and the p53-related EMT, by which MFR-surviving cells might obtain an invasive phenotype and metastatic potential.

Oncolytic Adenovirus H101 Synergizes with Radiation in Cervical Cancer Cells

BACKGROUND

A major challenge in cervical cancer radiotherapy is tailoring the radiation doses efficiently to eliminate malignant cells and reduce the side effects in normal tissues. Oncolytic adenovirus drug H101 was recently tested and approved as a topical adjuvant treatment for several malignancies.

OBJECTIVE

This study aimed to evaluate the potential neoadjuvant radiotherapy benefits of H101 by testing the inhibitory function of H101 in combination with radiation in different cervical cancer cells.

METHODS

Human cervical cancer cell lines C33a, SiHa, CaSki, and HeLa were treated with varying concentrations of H101 alone or in combination with radiation (2 Gy or 4 Gy). Cell viability and apoptosis were measured at the indicated time intervals. HPV16 E6 and cellular p53 mRNA expression alteration was measured by qRT-PCR. In situ RNA scope was used to determine HPV E6 status. P53 protein alterations were detected by Western blot.

RESULTS

Cell viability and apoptosis assays revealed that the combination of a high dose of H101 (MOI=1000, 10000) with radiation yielded a synergistic anticancer effect in all tested cervical cancer cell lines (P<0.05), with the greatest effect achieved in HPV-negative C33a cells (P<0.05). Low-HPV16-viral-load SiHa cells were more sensitive to the combination therapy than high-HPV16- viral-load CaSki cells (P<0.05). The combined treatment reduced HPV16 E6 expression and increased cellular P53 levels compared to those observed with radiation alone in SiHa and CaSki cells (P<0.05).

CONCLUSION

Oncolytic adenovirus H101 effectively enhances the antitumor efficacy of radiation in cervical cancer cells and may serve as a novel combination therapy for cervical cancer.

Single Cell Detection of the p53 Protein by Mass Cytometry

Simple Summary

Investigation of protein expression in cancer cells is an important part of the diagnostic process. Increasing knowledge about expression of different proteins has been exploited for prognostic assessments and in some cases also for selection of treatment. The p53 protein has proven important in development of various cancers, and the expression of this protein and its signaling pathway is therefore of interest when examining cancer patient samples. Here, we present mass cytometry as a tool for detection of p53 expression. Mass cytometry allows for measurement of up to 50 parameters per sample with single cell resolution, and we aim to demonstrate its potential for p53-focused research.

Abstract

Purpose: The p53 protein and its post-translational modifications are distinctly expressed in various normal cell types and malignant cells and are usually detected by immunohistochemistry and flow cytometry in contemporary diagnostics. Here, we describe an approach for simultaneous multiparameter detection of p53, its post-translational modifications and p53 pathway-related signaling proteins in single cells using mass cytometry. Method: We conjugated p53-specific antibodies to metal tags for detection by mass cytometry, allowing the detection of proteins and their post-translational modifications in single cells. We provide an overview of the antibody validation process using relevant biological controls, including cell lines treated in vitro with a stimulus (irradiation) known to induce changes in the expression level of p53. Finally, we present the potential of the method through investigation of primary samples from leukemia patients with distinct TP53 mutational status. Results: The p53 protein can be detected in cell lines and in primary samples by mass cytometry. By combining antibodies for p53-related signaling proteins with a surface marker panel, we show that mass cytometry can be used to decipher the single cell p53 signaling pathway in heterogeneous patient samples. Conclusion: Single cell profiling by mass cytometry allows the investigation of the p53 functionality through examination of relevant downstream signaling proteins in normal and malignant cells. Our work illustrates a novel approach for single cell profiling of p53.

Cytochrome P4501B1 in bone marrow is co-expressed with key markers of mesenchymal stem cells. BMS2 cell line models PAH disruption of bone marrow niche development functions

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous pollutants that are metabolized to carcinogenic dihydrodiol epoxides (PAHDE) by cytochrome P450 1B1 (CYP1B1). This metabolism occurs in bone marrow (BM) mesenchymal stem cells (MSC), which sustain hematopoietic stem and progenitor cells (HSPC). In BM, CYP1B1-mediated metabolism of 7, 12-dimethylbenz[a]anthracene (DMBA) suppresses HSPC colony formation within 6 h, whereas benzo(a)pyrene (BP) generates protective cytokines. MSC, enriched from adherent BM cells, yielded the bone marrow stromal, BMS2, cell line. These cells express elevated basal CYP1B1 that scarcely responds to Ah receptor (AhR) inducers. BMS2 cells exhibit extensive transcriptome overlap with leptin receptor positive mesenchymal stem cells (Lepr+ MSC) that control the hematopoietic niche. The overlap includes CYP1B1 and the expression of HSPC regulatory factors (Ebf3, Cxcl12, Kitl, Csf1 and Gas6). MSC are large, adherent fibroblasts that sequester small HSPC and macrophage in the BM niche (Graphic abstract). High basal CYP1B1 expression in BMS2 cells derives from interactions between the Ah-receptor enhancer and proximal promoter SP1 complexes, boosted by autocrine signaling. PAH effects on BMS2 cells model Lepr+MSC niche activity. CYP1B1 metabolizes DMBA to PAHDE, producing p53-mediated mRNA increases, long after the in vivo HSPC suppression. Faster, direct p53 effects, favored by stem cells, remain possible PAHDE targets. However, HSPC regulatory factors remained unresponsive. BP is less toxic in BMS2 cells, but, in BM, CYP1A1 metabolism stimulates macrophage cytokines (Il1b > Tnfa> Ifng) within 6 h. Although absent from BMS2 and Lepr+MSC, their receptors are highly expressed. The impact of this cytokine signaling in MSC remains to be determined.

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BMS2 and Lepr+MSC cells co-express CYP1B1 and 12 functional niche activity markers.

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CYP1B1 mRNA in BMS2 cells depends on activation of SP1 coupled to an AhR enhancer unit.

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DMBA metabolism by CYP1B1 activates p53 gene targets in BMS2 cells far more than BP.

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HSPC suppression by CYP1B1 generation of PAHDE requires rapid, non-genomic targets.

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BMS2 and Lepr+MSC share receptors activated by BP stimulation of macrophage cytokines.

Regulation of DNA Damage Response and Homologous Recombination Repair by microRNA in Human Cells Exposed to Ionizing Radiation

Ionizing radiation may be of both artificial and natural origin and causes cellular damage in living organisms. Radioactive isotopes have been used significantly in cancer therapy for many years. The formation of DNA double-strand breaks (DSBs) is the most dangerous effect of ionizing radiation on the cellular level. After irradiation, cells activate a DNA damage response, the molecular path that determines the fate of the cell. As an important element of this, homologous recombination repair is a crucial pathway for the error-free repair of DNA lesions. All components of DNA damage response are regulated by specific microRNAs. MicroRNAs are single-stranded short noncoding RNAs of 20–25 nt in length. They are directly involved in the regulation of gene expression by repressing translation or by cleaving target mRNA. In the present review, we analyze the biological mechanisms by which miRNAs regulate cell response to ionizing radiation-induced double-stranded breaks with an emphasis on DNA repair by homologous recombination, and its main component, the RAD51 recombinase. On the other hand, we discuss the ability of DNA damage response proteins to launch particular miRNA expression and modulate the course of this process. A full understanding of cell response processes to radiation-induced DNA damage will allow us to develop new and more effective methods of ionizing radiation therapy for cancers, and may help to develop methods for preventing the harmful effects of ionizing radiation on healthy organisms.

Deciphering MET-dependent modulation of global cellular responses to DNA damage by quantitative phosphoproteomics

Increasing evidence suggests that interference with growth factor receptor tyrosine kinase (RTK) signaling can affect DNA damage response (DDR) networks, with a consequent impact on cellular responses to DNA-damaging agents widely used in cancer treatment. In that respect, the MET RTK is deregulated in abundance and/or activity in a variety of human tumors. Using two proteomic techniques, we explored how disrupting MET signaling modulates global cellular phosphorylation response to ionizing radiation (IR). Following an immunoaffinity-based phosphoproteomic discovery survey, we selected candidate phosphorylation sites for extensive characterization by targeted proteomics focusing on phosphorylation sites in both signaling networks. Several substrates of the DDR were confirmed to be modulated by sequential MET inhibition and IR, or MET inhibition alone. Upon combined treatment, for two substrates, NUMA1 S395 and CHEK1 S345, the gain and loss of phosphorylation, respectively, were recapitulated using invivo tumor models by immunohistochemistry, with possible utility in future translational research. Overall, we have corroborated phosphorylation sites at the intersection between MET and the DDR signaling networks, and suggest that these represent a class of proteins at the interface between oncogene-driven proliferation and genomic stability.

Radiation resistance in head and neck squamous cell carcinoma: dire need for an appropriate sensitizer

Radiation is a significant treatment for patients with head and neck cancer. Despite advances to improve treatment, many tumors acquire radiation resistance resulting in poor survival. Radiation kills cancer cells by inducing DNA double-strand breaks. Therefore, radiation resistance is enhanced by efficient repair of damaged DNA. Head and neck cancers overexpress EGFR and have a high frequency of p53 mutations, both of which enhance DNA repair. This review discusses the clinical criteria for radiation resistance in patients with head and neck cancer and summarizes how cancer cells evade radiation-mediated apoptosis by p53- and epidermal growth factor receptor (EGFR)-mediated DNA repair. In addition, we explore the role of cancer stem cells in promoting radiation resistance, and how the abscopal effect provides rationale for combination strategies with immunotherapy.