Pharmacologic inhibition of ATR and ATM offers clinically important distinctions to enhancing platinum or radiation response in ovarian, endometrial, and cervical cancer cells

A targetable OSGIN1 - AMPK - SLC2A3 axis controls the vulnerability of ovarian cancer to ferroptosis

Despite advances in various chemotherapy regimens, current therapeutic options are limited for ovarian cancer patients. Oxidative stress-induced growth inhibitor 1 (OSGIN1), which is a tumor suppressor gene known to regulate the cellular stress response and apoptosis, is associated with ovarian cancer development. However, the underlying mechanisms involved in ferroptosis regulation have not been elucidated. Thus, this study aimed to investigate the effect and underlying regulatory mechanism of the OSGIN1 gene on ovarian cancer cells. Our results demonstrated that loss of the OSGIN1 gene promoted ovarian cancer growth and conferred resistance to drug-induced ferroptosis. Mechanistically, the loss of OSGIN1 activates AMPK signaling through ATM, leading to the upregulation of SLC2A3, which protects cells from ferroptosis and renders them insensitive to ferroptosis inducers. Notably, an SLC2A3-neutralizing antibody enhances the ferroptosis-inducing and anticancer effects of sorafenib on ovarian cancer patient-derived xenograft tumors. Overall, anti-SLC2A3 therapy is a promising method to improve ovarian cancer treatment by targeting ferroptosis.

ATRX loss inhibits DDR to strengthen radio-sensitization in p53-deficent HCT116 cells

Identifying novel targets for molecular radiosensitization is critical for improving the efficacy of colorectal cancer (CRC) radiotherapy. Alpha-thalassemia/mental retardation X-linked (ATRX), a member of the SWI/SNF-like chromatin remodeling protein family, functions in the maintenance of genomic integrity and the regulation of apoptosis and senescence. However, whether ATRX is directly involved in the radiosensitivity of CRC remains unclear. Our results showed that silencing ATRX increased the radiosensitivity of HCT116 CRC cells, which was further strengthened when p53 was depleted. To explore the potential mechanism, we focused on the impact of the ionizing radiation (IR)-induced DNA damage response (DDR), apoptosis, and senescence and the activation of the Daxx/MDM2/p53 pathway caused by ATRX loss. The results showed that IR induced DNA damage and G2/M arrest after depleting ATRX, especially in p53-depleted HCT116 cells, and inhibited ATM/Chk2 pathway activation, indicating that ATRX loss leads to failure of triggering the ATM/Chk2 pathway. Accordingly, ATRX loss promotes cell apoptosis and attenuates cell senescence. Interestingly, our results indicate that ATRX loss upregulates p53 function via the Daxx/MDM2 pathway to mediate radiosensitivity. Thus, ATRX may represent a novel radiosensitizing target for CRC, particularly p53-deficient CRC.

High-Grade Endometrial Cancer: Molecular Subtypes, Current Challenges, and Treatment Options

Although many recent advancements have been made in women's health, perhaps one of the most neglected areas of research is the diagnosis and treatment of high-grade endometrial cancer (EnCa). The molecular classification of EnCa in concert with histology was a major step forward. The integration of profiling for mismatch repair deficiency and Human Epidermal Growth Factor 2 (HER2) overexpression, can further inform treatment options, especially for drug resistant recurrent disease. Recent early phase trials suggest that regardless of subtype, combination therapy with agents that have distinct mechanisms of action is a fruitful approach to the treatment of high-grade EnCa. Unfortunately, although the importance of diagnosis and treatment of high-grade EnCa is well recognized, it is understudied compared to other gynecologic and breast cancers. There remains a tremendous need to couple molecular profiling and biomarker development with promising treatment options to inform new treatment strategies with higher efficacy and safety for all who suffer from high-grade recurrent EnCa.

The KRAS, ATR and CHEK1 expression levels in endometrial cancer are the risk factors predicting recurrence

Endometrial cancer is the most prevalent gynecologic malignancy with a high risk of recurrence. Local recurrence occurs in 7-20% of patients with treated stage I cancer within 3 years after primary treatment. In this study, we found significantly elevated mRNA expression levels of the oncoprotein KRAS, along with two replicative stress markers, ATR and CHEK1, in samples of endometrial carcinomas of endometrium (ECE) from patients with relapse. In contrast, mRNA expression levels of the studied genes were low and uniform in samples from patients without relapse. Elevated levels of KRAS protein and the phosphorylated form of ATR/CHEK1 were distinguishing features of recurrent ECE. A strong positive correlation was found between elevated mRNA and protein levels of the studied molecules. Elevated KRAS protein levels are characteristic of poorly differentiated (G3) endometrial carcinomas with deep myometrial invasion in patients without recurrence. In contrast, in patients with recurrence, higher protein levels of KRAS, pATR and pCHEK1 were observed in samples of G1-2 endometrial carcinomas, with statistically significant differences confirmed for pATR. High pCHEK1 protein levels are associated with deep tumor invasion in the myometrium among patients with recurrence. ROC analysis confirmed that evaluating the specificity and sensitivity of KRAS, pATR and pCHEK1 predicts recurrence development in patients with ECE. Our findings indicate that markers of replicative stress may play a significant role in ECE pathogenesis. Determining their levels in tumor samples after primary treatment could help define patients at high risk of recurrence and guide consequent courses of treatment.

Metronomic dosing of ovarian cancer cells with the ATR inhibitor AZD6738 leads to loss of CDC25A expression and resistance to ATRi treatment

OBJECTIVE

ATR kinase inhibitors promote cell killing by inducing replication stress and through potentiation of genotoxic agents in gynecologic cancer cells. To explore mechanisms of acquired resistance to ATRi in ovarian cancer, we characterized ATRi-resistant ovarian cancer cells generated by metronomic dosing with the clinical ATR inhibitor AZD6738.

METHODS

ATRi-resistant ovarian cancer cells (OVCAR3 and OV90) were generated by dosing with AZD6738 and assessed for sensitivity to Chk1i (LY2603618), PARPi (Olaparib) and combination with cisplatin or a CDK4/6 inhibitor (Palbociclib). Models were characterized by diverse methods including silencing CDC25A in OV90 cells and assessing impact on ATRi response. Serum proteomic analysis of ATRi-resistant OV90 xenografts was performed to identify circulating biomarker candidates of ATRi-resistance.

RESULTS

AZD6738-resistant cell lines are refractory to LY2603618, but not to Olaparib or combinations with cisplatin. Cell cycle analyses showed ATRi-resistant cells exhibit G1/S arrest following AZD6738 treatment. Accordingly, combination with Palbociclib confers resistance to AZD6738. AZD6738-resistant cells exhibit altered abundances of G1/S phase regulatory proteins, including loss of CDC25A in AZD6738-resistant OV90 cells. Silencing of CDC25A in OV90 cells confers resistance to AZD6738. Serum proteomics from AZD6738-resistant OV90 xenografts identified Vitamin D-Binding Protein (GC), Apolipoprotein E (APOE) and A1 (APOA1) as significantly elevated in AZD6738-resistant backgrounds.

CONCLUSIONS

We show that metronomic dosing of ovarian cancer cells with AZD6738 results in resistance to ATR/ Chk1 inhibitors, that loss of CDC25A expression represents a mechanism of resistance to ATRi treatment in ovarian cancer cells and identify several circulating biomarker candidates of CDC25A low, AZD6738-resistant ovarian cancer cells.

Genetic characteristics of platinum-sensitive ovarian clear cell carcinoma

OBJECTIVE

Most ovarian clear cell carcinomas are resistant to platinum-based chemotherapy, while a small subset shows a positive response. The aim of this study was to clarify the clinical, pathological and genetic characteristics of platinum-sensitive ovarian clear cell carcinomas.

METHODS

The study included 53 patients with stage III-IV ovarian clear cell carcinoma who had residual tumours after primary surgery and received platinum-based therapy between 2009 and 2018. A retrospective examination of platinum sensitivity was performed using the criterion of ≥6 months from the last day of first-line platinum therapy until recurrence/progression. Cases determined to be platinum-sensitive were subjected to immunohistochemical staining, genomic analyses using target sequencing (i.e. NCC Oncopanel) and homologous recombination deficiency (myChoice® HRD Plus) assays.

RESULTS

Of the 53 stage III-IV ovarian clear cell carcinoma cases, 11 (21%) were platinum-sensitive. These cases showed better progression-free and overall survival than platinum-resistant cases (hazard ratio = 0.16, P < 0.001). Among the seven sensitive cases whose tumour tissues were available for molecular profiling, five were pure ovarian clear cell carcinoma based on pathological and genetic features, whereas the remaining two cases were re-diagnosed as high-grade serous ovarian carcinoma. The pure ovarian clear cell carcinomas lacked BRCA1 and BRCA2 mutations, consistent with the absence of the homologous recombination deficiency phenotype, whereas two cases (40%) had ATM mutations. By contrast, the two high-grade serous ovarian carcinoma cases had BRCA1 or BRCA2 mutations associated with the homologous recombination deficiency phenotype.

CONCLUSION

The subset of platinum-sensitive ovarian clear cell carcinomas includes a majority with pure ovarian clear cell carcinoma features that lack the homologous recombination deficiency phenotype.

Targeting DNA Damage Repair and Immune Checkpoint Proteins for Optimizing the Treatment of Endometrial Cancer

The dependence of cancer cells on the DNA damage response (DDR) pathway for the repair of endogenous- or exogenous-factor-induced DNA damage has been extensively studied in various cancer types, including endometrial cancer (EC). Targeting one or more DNA damage repair protein with small molecules has shown encouraging treatment efficacy in preclinical and clinical models. However, the genes coding for DDR factors are rarely mutated in EC, limiting the utility of DDR inhibitors in this disease. In the current review, we recapitulate the functional role of the DNA repair system in the development and progression of cancer. Importantly, we discuss strategies that target DDR proteins, including PARP, CHK1 and WEE1, as monotherapies or in combination with cytotoxic agents in the treatment of EC and highlight the compounds currently being evaluated for their efficacy in EC in clinic. Recent studies indicate that the application of DNA damage agents in cancer cells leads to the activation of innate and adaptive immune responses; targeting immune checkpoint proteins could overcome the immune suppressive environment in tumors. We further summarize recently revolutionized immunotherapies that have been completed or are now being evaluated for their efficacy in advanced EC and propose future directions for the development of DDR-based cancer therapeutics in the treatment of EC.

Could Inhibiting the DNA Damage Repair Checkpoint Rescue Immune-Checkpoint-Inhibitor-Resistant Endometrial Cancer?

Endometrial cancer (EC) is increasingly undermining female health worldwide, with poor survival rates for advanced or recurrent/metastatic diseases. The application of immune checkpoint inhibitors (ICIs) has opened a window of opportunity for patients with first-line therapy failure. However, there is a subset of patients with endometrial cancer who remain insensitive to immunotherapy alone. Therefore, it is necessary to develop new therapeutic agents and further explore reliable combinational strategies to optimize the efficacy of immunotherapy. DNA damage repair (DDR) inhibitors as novel targeted drugs are able to generate genomic toxicity and induce cell death in solid tumors, including EC. Recently, growing evidence has demonstrated the DDR pathway modulates innate and adaptive immunity in tumors. In this review, we concentrate on the exploration of the intrinsic correlation between DDR pathways, especially the ATM-CHK2-P53 pathway and the ATR-CHK1-WEE1 pathway, and oncologic immune response, as well as the feasibility of adding DDR inhibitors to ICIs for the treatment of patients with advanced or recurrent/metastatic EC. We hope that this review will offer some beneficial references to the investigation of immunotherapy and provide a reasonable basis for "double-checkpoint inhibition" in EC.

Association of variations in the CAT and prognosis in lung cancer patients with platinum-based chemotherapy

PURPOSE: To explore the relationship between ATM, ATR and CAT polymorphisms and prognosis of lung cancer patients received platinum-based chemotherapy.

METHODS: 404 patients with lung cancer who received platinum-chemotherapy were enrolled and DNA typing was performed. Cox regression analysis and stratification analyses was performed to assess relationships between OS and PFS with SNPs genotypes. The prognosis of lung adenocarcinomaand squamous cell carcinomapatients was analyzed with The Cancer Genome Atlas (TCGA) database according to the grouping of CAT expression.

RESULTS:CAT rs769217 was significantly related to PFS of patients with lung cancer who received platinum-chemotherapy. In the Additive model, rs769217 was associated with PFS (HR = 0.747, 95% CI = 0.581–0.960, p = 0.023). In the Dominant model, CT and TT genotypes led to lung cancer progression 0.738 times more than CC genotype. In stratification analyses of association between CAT rs769217 polymorphisms and PFS, the HR of patients at stage IV in additive model was 0.73, and HR was 0.745 (p = 0.034) in dominant model. For OS analyses, HR was 0.672 in the older lung cancer patients (&gt;55 years old) in additive model. Meanwhile, in the Dominant model, it was found that the older patients with CT and TT genotypes had better prognosis, and the risk of death after receiving platinum-based chemotherapy was 0.692 times that of patients with CC genotype (p = 0.037). TCGA data shows that LUAD patients with high CAT expression have longer OS (p = 0.020).

CONCLUSION:CAT rs769217 is significantly related to PSF of platinum-based chemotherapy in lung cancer patients and may be a biomarker for predicting the prognosis of lung cancer patients with platinum-based chemotherapy.

Fighting resistance: post-PARP inhibitor treatment strategies in ovarian cancer

Poly (ADP-ribose) polymerase inhibitors (PARPis) represent a therapeutic milestone in the management of epithelial ovarian cancer. The concept of 'synthetic lethality' is exploited by PARPi in tumors with defects in DNA repair pathways, particularly homologous recombination deficiency. The use of PARPis has been increasing since its approval as maintenance therapy, particularly in the first-line setting. Therefore, resistance to PARPi is an emerging issue in clinical practice. It brings an urgent need to elucidate and identify the mechanisms of PARPi resistance. Ongoing studies address this challenge and investigate potential therapeutic strategies to prevent, overcome, or re-sensitize tumor cells to PARPi. This review aims to summarize the mechanisms of resistance to PARPi, discuss emerging strategies to treat patients post-PARPi progression, and discuss potential biomarkers of resistance.

DNA Damage Response Alterations in Ovarian Cancer: From Molecular Mechanisms to Therapeutic Opportunities

The DNA damage response (DDR), a set of signaling pathways for DNA damage detection and repair, maintains genomic stability when cells are exposed to endogenous or exogenous DNA-damaging agents. Alterations in these pathways are strongly associated with cancer development, including ovarian cancer (OC), the most lethal gynecologic malignancy. In OC, failures in the DDR have been related not only to the onset but also to progression and chemoresistance. It is known that approximately half of the most frequent subtype, high-grade serous carcinoma (HGSC), exhibit defects in DNA double-strand break (DSB) repair by homologous recombination (HR), and current evidence indicates that probably all HGSCs harbor a defect in at least one DDR pathway. These defects are not restricted to HGSCs; mutations in ARID1A, which are present in 30% of endometrioid OCs and 50% of clear cell (CC) carcinomas, have also been found to confer deficiencies in DNA repair. Moreover, DDR alterations have been described in a variable percentage of the different OC subtypes. Here, we overview the main DNA repair pathways involved in the maintenance of genome stability and their deregulation in OC. We also recapitulate the preclinical and clinical data supporting the potential of targeting the DDR to fight the disease.

Molecular mechanisms of long noncoding RNAs associated with cervical cancer radiosensitivity

Despite advances in cervical cancer screening and human papilloma virus (HPV) vaccines, cervical cancer remains a global health burden. The standard treatment of cervical cancer includes surgery, radiation therapy, and chemotherapy. Radiotherapy (RT) is the primary treatment for advanced-stage disease. However, due to radioresistance, most patients in the advanced stage have an adverse outcome. Recent studies have shown that long noncoding RNAs (lncRNAs) participate in the regulation of cancer radiosensitivity by regulating DNA damage repair, apoptosis, cancer stem cells (CSCs), and epithelial-mesenchymal transition (EMT). In this review, we summarize the molecular mechanisms of long noncoding RNAs in cervical cancer and radiosensitivity, hoping to provide a theoretical basis and a new molecular target for the cervical cancer RT in the clinic.

On the need for standardized reporting of photophysical parameters of in vitro photodynamic therapy studies

In vitro dose escalation experiments are one of the first gatekeepers in therapeutic evaluation and development. This also holds for evaluating novel photosensitizers (PS) and Photodynamic Therapy (PDT) co-therapies as needed to provide dose response guidelines before engaging in further pre-clinical studies. The dose needed to achieve 50% cell kill (LD₅₀) is a standard metric to report the potency of a therapeutic agents that is widely accepted for single-drug therapies. In reporting results of PDT experiments, which involve delivery of both drug and light, it is inherently more complicated to identify such a convenient dose response metric that actually captures the larger space of treatment parameters. In addition to ubiquitous sources of biological variability that apply broadly in biomedical research, PDT treatment efficacy is determined by multiple key parameters that may or may not have been documented, including PS concentration and light fluence, where the latter is itself a function of the spectral properties of the light source used (often not described), not to mention dose rate, fractionation and other parameters that potentially vary between individual studies. It is impossible to compare results between two study when, for example one reports LD₅₀ PS concentration without providing essential light dosimetry details. Motivated by this challenge in comparing outcomes and establishing reproducibility of in vitro PDT studies, we endeavored to perform a meta-analysis of the reporting of PDT results by converting, where possible, the disparately reported experimental details into a consistent metric that could be used to compare across studies. In this context we adopt here the number of photons absorbed by photosensitizers per unit volume to affect a 50% decline in cell survival as a standardized metric. By choosing this metric one can acknowledge the quantum-based generation of cytotoxins. While this metric does not cover every possible source of variability between any two studies, for a PS with known optical properties, this does encapsulate PS concentration as well as irradiance and spectral properties of light delivered. For the sake of focus we adopt this approach for study of reported results with two photosensitizers, Protoporphyrin IX, either synthesized in the cells by aminolevulinic acid or administered exogenously, and Chlorin e6. A literature search was performed to identify in vitro studies with these two photosensitizers and collect necessary information to calculate the absorbed photon LD₅₀ threshold for each study. Only approximately 1/10 of the manuscripts reporting on in vitro studies provide the minimum required information to calculate the threshold values. While the majority of the determined threshold values are within a factor of 10, the range of threshold values spanned close to 7 orders of magnitude for both photosensitizers. To contrast with single-agent therapies, a similar exercise was performed for chemotherapeutic drugs targeting cellular mitosis or tyrosine kinase inhibitors resulted in an LD₅₀ or IC₅₀ range of 1-2 orders of magnitude, with LD₅₀ or IC₅₀ values for a single cell line being within a factor of 5. This review underscores challenges in the reporting of in vitro PDT efficacy. In many cases it takes considerable effort to extract the necessary methodology information to make meaningful comparison between PDT studies. Only when results between studies can be compared is it possible to begin to assess reproducibility which, as shown here, can be a major issue. Hence, guidelines need to be developed and enforced through the peer review process for meaningful reporting of preclinical PDT results in order for the most promising sensitizers and co-therapies to be identified and translated into the clinic.

Improving cervical cancer survival-A multifaceted strategy to sustain progress for this global problem

Cervical cancer is associated with profound socioeconomic and racial disparities in incidence, mortality, morbidity, and years of life lost. The last standard-of-care treatment innovation for locally advanced cervical cancer occurred in 1999, when cisplatin chemotherapy was added to pelvic radiation therapy (chemoradiation therapy). Chemoradiation therapy is associated with a 30%-50% failure rate, and there is currently no cure for recurrent or metastatic disease. The enormity of the worldwide clinical problem of cervical cancer morbidity and mortality as well as the egregiously unchanged mortality rate over the last several decades are recognized by the National Institutes of Health as urgent priorities. This is reflected within the Office of Research on Women's Health effort to advance National Institutes of Health research on the health of women, as highlighted in a recent symposium. In the current review, the authors address the state of the science and opportunities to improve cervical cancer survival with an emphasis on improving access, using technology in innovative and widely implementable ways, and improving current understanding of cervical cancer biology. LAY SUMMARY: Cervical cancer is associated with profound socioeconomic and racial disparities in incidence, mortality, morbidity, and years of life lost. In this review, the state of the science and opportunities to improve cervical cancer survival are presented with an emphasis on improving access, using technology in innovative and widely implementable ways, and improving current understanding of cervical cancer biology.

ATR Inhibitors in Platinum-Resistant Ovarian Cancer

Platinum-resistant ovarian cancer (PROC) is one of the deadliest types of epithelial ovarian cancer, and it is associated with a poor prognosis as the median overall survival (OS) is less than 12 months. Targeted therapy is a popular emerging treatment method. Several targeted therapies, including those using bevacizumab and poly (ADP-ribose) polymerase inhibitor (PARPi), have been used to treat PROC. Ataxia telangiectasia and RAD3-Related Protein Kinase inhibitors (ATRi) have attracted attention as a promising class of targeted drugs that can regulate the cell cycle and influence homologous recombination (HR) repair. In recent years, many preclinical and clinical studies have demonstrated the efficacy of ATRis in PROC. This review focuses on the anticancer mechanism of ATRis and the progress of research on ATRis for PROC.

Prognostic significance of MATR3 in stage I and II non-small cell lung cancer patients

PURPOSE

Matrin 3 (MATR3) is a nuclear matrix protein involved in mRNA stabilization, nuclear retention of hyper-edited RNAs, and RNA splicing. The role of MATR3 in cancer is still unclear. The present study aimed to investigate expression levels and prognostic significance of MATR3 in stage I and II non-small cell lung cancer (NSCLC) patients.

METHODS

We examined MATR3 protein immunohistochemically in tumoral and non-tumoral tissue sections from n = 67 NSCLC patients treated at hospital, and MATR3 mRNA from The Cancer Genome Atlas (TCGA) cohort with respect to valid prognostic and predictive features, as well as treatment outcome.

RESULTS

Significantly higher immunohistochemical levels of MATR3 protein were found in tumor-adjacent tissue compared to cancer (p = 0.049). A decrease in MATR3 protein expression was found to be a significant independent adverse prognostic factor for patients overall survival (p = 0.007). By contrast, we observed higher MATR3 mRNA levels in tumoral tissue compared to control lung tissues (p < 0.001). Based on the TCGA dataset, we reported that high MATR3 mRNA level was significantly associated with worse OS of NSCLC patients (p < 0.001); however, it was not an independent prognostic marker (p = 0.156). The discrepancies in prognostic significance of MATR3 gene mRNA and protein levels imply a need for further investigation.

CONCLUSION

In conclusion, the present study warrants further investigation into the biological and prognostic value of MATR3 as a potential prognostic marker in early-stage NSCLC patients.

ATR inhibition sensitizes liposarcoma to doxorubicin by increasing DNA damage

Liposarcomas account for approximately 20% of all adult sarcomas and have limited therapeutic options outside of surgery. Inhibition of ataxia-telangiectasia and Rad3 related protein kinase (ATR) has emerged as a promising chemotherapeutic strategy in various cancers. However, its activation, expression, and function in liposarcoma remain unkown. In this study, we investigated the expression, function, and potential of ATR as a therapeutic target in liposarcoma. Activation and expression of ATR in liposarcoma was analyzed by immunohistochemistry, which was further explored for correlation with patient clinical characteristics. ATR-specific siRNA and the ATR inhibitor VE-822 were applied to determine the effect of ATR inhibition on liposarcoma cell proliferation and anti-apoptotic activity. Migration activity and clonogenicity were examined using wound healing and clonogenic assays. ATR (p-ATR) was overexpressed in 88.1% of the liposarcoma specimens and correlated with shorter overall survival in patients. Knockdown of ATR via specific siRNA or inhibition with VE-822 suppressed liposarcoma cell growth, proliferation, migration, colony-forming ability, and spheroid growth. Importantly, ATR inhibition significantly and synergistically enhanced liposarcoma cell line chemosensitivity to doxorubicin. Our findings support ATR as critical to liposarcoma proliferation and doxorubicin resistance. Therefore, the addition of ATR inhibition to a standard doxorubicin regimen is a potential treatment strategy for liposarcoma.

Observation of the cervical microbiome in the progression of cervical intraepithelial neoplasia

OBJECTIVE

Cervical microbial community in the cervical intraepithelial neoplasia and cervical cancer patients was analysed to study its composition, diversity and signalling pathways by high-throughput 16S rDNA sequencing,and the candidate genes associated with occurrence and progression of cervical intraepithelial neoplasia were screened out and the model was established to predict the evolution of cervical intraepithelial neoplasia malignant transformation from the cervical microbial genes aspect.

METHODS

Cervical tissues of normal, cervical intraepithelial neoplasia and cervical cancer patients without receiving any treatment were collected. The correlation between candidate genes and cervical intraepithelial neoplasia progression was initially determined by analyzing the microbial flora. Real-time fluorescence quantitative PCR was used to detect the expression of candidate genes in different cervical tissues, ROC curve and logistic regression was used to analyse and predict the risk factors related to the occurrence and progression of cervical intraepithelial neoplasia. Finally, the early warning model of cervical intraepithelial neoplasia occurrence and progression is established.

RESULTS

Cervical tissues from normal, cervical intraepithelial neoplasia and cervical cancer patients were collected for microbial community high-throughput 16S rDNA sequencing. The analysis revealed five different pathways related to cervical intraepithelial neoplasia. 10 candidate genes were selected by further bioinformatics analysis and preliminary screening. Real time PCR, ROC curve and Logistic regression analysis showed that human papillomavirus infection, TCT severity, ABCG2, TDG, PCNA were independent risk factors for cervical intraepithelial neoplasia. We used these indicators to establish a random forest model. Seven models were built through different combinations. The model 4 (ABCG2 + PCNA + TDG) was the best early warning model for the occurrence and progression of CIN.

CONCLUSIONS

A total of 5 differential pathways and 10 candidate genes related to occurrence and progression of cervical intraepithelial neoplasia were found in cervical microbial community. This study firstly identified the genes from cervical microbial community that play an important role in the occurrence and progression of cervical intraepithelial neoplasia. At the same time, the early warning model including ABCG2 + PCNA+TDG genes provided a new idea and target for clinical prediction and blocking the evolution of cervical intraepithelial neoplasia malignant transformation from the aspect of cervical microbiological related genes.

Pharmacologic inhibition of ataxia telangiectasia and Rad3-related (ATR) in the treatment of head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) poses significant treatment challenges, with high recurrence rates for locally advanced disease despite aggressive therapy typically involving a combination of surgery, radiation therapy, and/or chemotherapy. HNSCCs commonly exhibit reduced or absent TP53 function due to genomic alterations or human papillomavirus (HPV) infection, leading to dependence on the S- and G2/M checkpoints for cell cycle regulation. Both of these checkpoints are activated by Ataxia Telangiectasia and Rad3-related (ATR), which tends to be overexpressed in HNSCC relative to adjacent normal tissues and represents a potentially promising therapeutic target, particularly in combination with other treatments. ATR is a DNA damage signaling kinase that is activated in response to replication stress and single-stranded DNA breaks, such as those induced by radiation therapy and certain chemotherapies. ATR kinase inhibitors are currently being investigated in several clinical trials as part of the management of locally advanced, recurrent, or metastatic HNSCC, along with other malignancies. In this review article, we summarize the rationale and preclinical data supporting incorporation of ATR inhibition into therapeutic regimens for HNSCC.

[Place of PARP inhibitors in the treatment of endometrial and cervical cancers]

New molecular therapeutic approaches have emerged in recent years for advanced gynaecological cancers, including targeted therapies such as poly-ADP-ribose polymerase inhibitors (PARPi). These have demonstrated efficacy in high-grade serous ovarian cancers in patients carrying a mutation in the BRCA gene, which predisposes them to breast and ovarian cancers. Clinical and pre-clinical data suggest that the activity of PARPi inhibitors may not be limited to BRCA mutated tumours and may involve the homologous recombination pathway. These data raise the question of the potential efficacy of PARPi in advanced endometrial and cervical cancers where treatment options are currently limited. At present, there are few data available on the activity of PARPi in endometrial and cervical cancers, but some results seem promising. In this review, we present a synthesis of the available studies concerning PARPi in endometrial and cervical cancer.

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.

Nerolidol inhibits proliferation of leiomyoma cells via reactive oxygen species-induced DNA damage and downregulation of the ATM/Akt pathway

Nerolidol (3,7,11-trimethyl-1,6,10-dodecatrien-3-ol), a sesquiterpene alcohol present in aromatic essential oils of numerous plants, has been reported to possess anticancer activity. The potential therapeutic effect of nerolidol on uterine fibroids (UF), the most common benign tumor of the uterus worldwide, is unknown. In this study, we examined the anti-UF potential of nerolidol in ELT3 cells, a rat leiomyoma cell line widely used as an in vitro model, to identify the potential therapeutic agents for UF. We observed that treatment with cis- or trans-nerolidol inhibited cell proliferation in a dose-dependent manner and induced cell cycle arrest in the G1 phase, which was accompanied by reduction in Akt phosphorylation and downregulation of cyclin D1, cyclin-dependent kinase 4 (CDK4), and CDK6 protein expression. The proliferation-inhibiting activity of nerolidol correlated with the generation of intracellular reactive oxygen species (ROS), which was suppressed by N-acetyl-l-cysteine, a ROS inhibitor. Nerolidol treatment also increased the percentage of cells for which tail moment could be calculated using an alkaline comet assay, and induced p-γH2AX^ser139 expression, which indicated induction of DNA damage. We also observed downregulation of ATM and its phosphorylation after nerolidol treatment; furthermore, treatment with KU-55933, an ATM kinase inhibitor, mimicked the inhibitory effects of nerolidol treatment on cell proliferation and Akt phosphorylation. In conclusion, nerolidol displayed anti-UF activity in a leiomyoma cell model via ROS-induced DNA damage and G1 phase cell cycle arrest by inhibiting the expression and activation of the ATM/Akt pathway. Our data suggests that nerolidol is a potential therapeutic agent for UF.

Radiation induces NORAD expression to promote ESCC radiotherapy resistance via EEPD1/ATR/Chk1 signalling and by inhibiting pri-miR-199a1 processing and the exosomal transfer of miR-199a-5p

BACKGROUND

Radioresistance, a poorly understood phenomenon, results in the failure of radiotherapy and subsequent local recurrence, threatening a large proportion of patients with ESCC. To date, lncRNAs have been reported to be involved in diverse biological processes, including radioresistance.

METHODS

FISH and qRT-PCR were adopted to examine the expression and localization of lncRNA-NORAD, pri-miR-199a1 and miR-199a-5p. Electron microscopy and nanoparticle tracking analysis (NTA) were conducted to observe and identify exosomes. High-throughput microRNAs sequencing and TMT mass spectrometry were performed to identify the functional miRNA and proteins. A series of in vitro and in vivo experiments were performed to investigate the biological effect of NORAD. ChIP, RIP-qPCR, co-IP and dual-luciferase reporter assays were conducted to explore the interaction of related RNAs and proteins.

RESULTS

We show here that DNA damage activates the noncoding RNA NORAD, which is critical for ESCC radioresistance. NORAD was expressed at high levels in radioresistant ESCC cells. Radiation treatment promotes NORAD expression by enhancing H3K4me2 enrichment in its sequence. NORAD knockdown cells exhibit significant hypersensitivity to radiation in vivo and in vitro. NORAD is required to initiate the repair and restart of stalled forks, G2 cycle arrest and homologous recombination repair upon radiation treatment. Mechanistically, NORAD inhibits miR-199a-5p expression by competitively binding PUM1 from pri-miR-199a1, inhibiting the processing of pri-miR-199a1. Mature miR-199a-5p in NORAD knockdown cells is packaged into exosomes; miR-199a-5p restores the radiosensitivity of radioresistant cells by targeting EEPD1 and then inhibiting the ATR/Chk1 signalling pathway. Simultaneously, NORAD knockdown inhibits the ubiquitination of PD-L1, leading to a better response to radiation and anti-PD-1 treatment in a mouse model.

CONCLUSIONS

Based on the findings of this study, lncRNA-NORAD represents a potential treatment target for improving the efficiency of immunotherapy in combination with radiation in ESCC.

Hydroxygenkwanin Increases the Sensitivity of Liver Cancer Cells to Chemotherapy by Inhibiting DNA Damage Response in Mouse Xenograft Models

Molecules involved in DNA damage response (DDR) are often overexpressed in cancer cells, resulting in poor responses to chemotherapy and radiotherapy. Although treatment efficacy can be improved with the concomitant use of DNA repair inhibitors, the accompanying side effects can compromise the quality of life of patients. Therefore, in this study, we identified a natural compound that could inhibit DDR, using the single-strand annealing yeast-cell analysis system, and explored its mechanisms of action and potential as a chemotherapy adjuvant in hepatocellular carcinoma (HCC) cell lines using comet assay, flow cytometry, Western blotting, immunofluorescence staining, and functional analyses. We developed a mouse model to verify the in vitro findings. We found that hydroxygenkwanin (HGK) inhibited the expression of RAD51 and progression of homologous recombination, thereby suppressing the ability of the HCC cell lines to repair DNA damage and enhancing their sensitivity to doxorubicin. HGK inhibited the phosphorylation of DNA damage checkpoint proteins, leading to apoptosis in the HCC cell lines. In the mouse xenograft model, HGK enhanced the sensitivity of liver cancer cells to doxorubicin without any physiological toxicity. Thus, HGK can inhibit DDR in liver cancer cells and mouse models, making it suitable for use as a chemotherapy adjuvant.

Sensors and Inhibitors for the Detection of Ataxia Telangiectasia Mutated (ATM) Protein Kinase

Recruitment and activation of the ataxia telangiectasia mutated (ATM) kinase regulate multiple cell-cycle checkpoints relevant to complex biological events like DNA damage repair and apoptosis. Molecularly specific readouts of ATM using protein assays, fluorescence, or radiolabeling have advanced significantly over the past few years. This Review covers the molecular imaging techniques that enable the visualization of ATM-from traditional quantitative protein assays to the potential use of ATM inhibitors to generate new imaging agents to interrogate ATM. We are confident that molecular imaging coupled with advanced technologies will play a pivotal role in visualizing and understanding the biology of ATM and accelerate its applications in the diagnosis and monitoring of disease, including radiation therapy and patient stratification.

DNA Repair Pathways in Cancer Therapy and Resistance

DNA repair pathways are triggered to maintain genetic stability and integrity when mammalian cells are exposed to endogenous or exogenous DNA-damaging agents. The deregulation of DNA repair pathways is associated with the initiation and progression of cancer. As the primary anti-cancer therapies, ionizing radiation and chemotherapeutic agents induce cell death by directly or indirectly causing DNA damage, dysregulation of the DNA damage response may contribute to hypersensitivity or resistance of cancer cells to genotoxic agents and targeting DNA repair pathway can increase the tumor sensitivity to cancer therapies. Therefore, targeting DNA repair pathways may be a potential therapeutic approach for cancer treatment. A better understanding of the biology and the regulatory mechanisms of DNA repair pathways has the potential to facilitate the development of inhibitors of nuclear and mitochondria DNA repair pathways for enhancing anticancer effect of DNA damage-based therapy.

Challenges of the current precision medicine approach for pancreatic cancer: A single institution experience between 2013 and 2017

Recent research on genomic profiling of pancreatic ductal adenocarcinoma (PDAC) has identified many potentially actionable alterations. However, the feasibility of using genomic profiling to guide routine clinical decision making for PDAC patients remains unclear. We retrospectively reviewed PDAC patients between October 2013 and December 2017, who underwent treatment at the Johns Hopkins Hospital and had clinical tumor next-generation sequencing (NGS) through commercial resources. Ninety-two patients with 93 tumors tested were included. Forty-eight (52%) patients had potentially curative surgeries. The median time from the tissue available to the NGS testing ordered was 229 days (interquartile range 62-415). A total of three (3%) patients had matched targeted therapies based on genomic profiling results. Genomic profiling guided personalized treatment for PDAC patients is feasible, but the percentage of patients who receive targeted therapy is low. The main challenges are ordering NGS testing early in the clinical course of the disease and the limited evidence of using a targeted approach in these patients. A real-time department level genomic testing ordering system in combination with an evidence-based flagging system for potentially actionable alterations could help address these shortcomings.

Alternate therapeutic pathways for PARP inhibitors and potential mechanisms of resistance

Homologous recombination (HR) repair deficiency impairs the proper maintenance of genomic stability, thus rendering cancer cells vulnerable to loss or inhibition of DNA repair proteins, such as poly(ADP-ribose) polymerase-1 (PARP-1). Inhibitors of nuclear PARPs are effective therapeutics for a number of different types of cancers. Here we review key concepts and current progress on the therapeutic use of PARP inhibitors (PARPi). PARPi selectively induce synthetic lethality in cancer cells with homologous recombination deficiencies (HRDs), the most notable being cancer cells harboring mutations in the BRCA1 and BRCA2 genes. Recent clinical evidence, however, shows that PARPi can be effective as cancer therapeutics regardless of BRCA1/2 or HRD status, suggesting that a broader population of patients might benefit from PARPi therapy. Currently, four PARPi have been approved by the Food and Drug Administration (FDA) for the treatment of advanced ovarian and breast cancer with deleterious BRCA mutations. Although PARPi have been shown to improve progression-free survival, cancer cells inevitably develop resistance, which poses a significant obstacle to the prolonged use of PARP inhibitors. For example, somatic BRCA1/2 reversion mutations are often identified in patients with BRCA1/2-mutated cancers after treatment with platinum-based therapy, causing restoration of HR capacity and thus conferring PARPi resistance. Accordingly, PARPi have been studied in combination with other targeted therapies to overcome PARPi resistance, enhance PARPi efficacy, and sensitize tumors to PARP inhibition. Moreover, multiple clinical trials are now actively underway to evaluate novel combinations of PARPi with other anticancer therapies for the treatment of PARPi-resistant cancer. In this review, we highlight the mechanisms of action of PARP inhibitors with or without BRCA1/2 defects and provide an overview of the ongoing clinical trials of PARPi. We also review the current progress on PARPi-based combination strategies and PARP inhibitor resistance.

ATR and p-ATR are emerging prognostic biomarkers and DNA damage response targets in ovarian cancer

Background:

Although ataxia-telangiectasia and Rad3 related (ATR) has an established role in the DNA damage response of various cancers, its clinical and prognostic significance in ovarian cancer remains largely unknown. The aims of this study were to assess the expression, function, and clinical prognostic relationship of ATR and phospho-ATR ser428 (p-ATR) in ovarian cancer.

Methods:

We confirmed ATR and p-ATR expression by immunohistochemistry (IHC) in a unique ovarian cancer tissue microarray constructed of paired primary, recurrent, and metastatic tumor tissues from 26 individual patients. ATR-specific small interfering RNA (siRNA) and ATR inhibitor VE-822 were applied to determine the effects of ATR inhibition on ovarian cancer cell proliferation, apoptosis, and DNA damage. ATR expression and the associated proteins of the ATR/Chk1 pathway in ovarian cancer cell lines were evaluated by Western blotting. The clonogenicity was also examined using clonogenic assays. A three dimensional (3D) cell culture model was performed to mimic the in vivo ovarian cancer environment to further validate the effects of ATR inhibition on ovarian cancer cells.

Results:

We show recurrent ovarian cancer tissues express higher levels of ATR and p-ATR than their patient-matched primary tumor counterparts. Additionally, higher expression of p-ATR correlates with decreased survival in ovarian cancer patients. Treatment of ovarian cancer cells with ATR specific siRNA or ATR inhibitor VE-822 led to significant apoptosis and inhibition of cellular proliferation, with reduced phosphorylation of Chk1 (p-Chk1), Cdc25c (p-Cdc25c), Cdc2 (p-Cdc2), and increased expression of cleaved PARP and γH2AX. Inhibition of ATR also suppressed clonogenicity and spheroid growth of ovarian cancer cells.

Conclusion:

Our results support the ATR and p-ATR pathway as a prognostic biomarker, and targeting the ATR machinery is an emerging therapeutic approach in the treatment of ovarian cancer.

Comparison of Patient Susceptibility Genes Across Breast Cancer: Implications for Prognosis and Therapeutic Outcomes

Hereditary breast cancer syndromes affect a small (10–15% of cases) but significant group of patients. BRCA1 and BRCA2 are the most familiar and well-studied genes associated with inherited breast cancer. However, mutations in the high-penetrance genes, TP53, PTEN, CDH1, MSH1, MLH1, MSH6, PMS2, PALB2, and STK11, and in the moderate-penetrance genes, CHEK2, ATM, and BRIP1, also correlate with high lifetime risks of breast cancer and other malignancies as well. Advances in breast cancer genetics have led to an improved perception of diagnosis and screening strategies. The specific considerations and challenges involved in treating this unique population have become a fertile ground for research. Indeed, these genes and downstream molecular pathways have now become potential therapeutic targets in breast cancer patients, including those with BRCA1 or BRCA2 mutations. This review describes the variety of hereditary breast cancer genes, from their molecular origins to the prognosis and multidisciplinary clinical decision-making processes. Key publications and other reported recent clinical trials and guidelines are provided.

Determinants of Sensitivity to Radiotherapy in Endometrial Cancer

Radiotherapy is one of the cornerstone treatments for endometrial cancer and has successfully diminished the risk of local recurrences after surgery. However, a considerable percentage of patients suffers tumor relapse due to radioresistance mechanisms. Knowledge about the molecular determinants that confer radioresistance or radiosensitivity in endometrial cancer is still partial, as opposed to other cancers. In this review, we have highlighted different central cellular signaling pathways and processes that are known to modulate response to radiotherapy in endometrial cancer such as PI3K/AKT, MAPK and NF-κB pathways, growth factor receptor signaling, DNA damage repair mechanisms and the immune system. Moreover, we have listed different clinical trials employing targeted therapies against some of the aforementioned signaling pathways and members with radiotherapy. Finally, we have identified the latest advances in radiotherapy that have started being utilized in endometrial cancer, which include modern radiotherapy and radiogenomics. New molecular and genetic studies in association with the analysis of radiation responses in endometrial cancer will assist clinicians in taking suitable decisions for each individual patient and pave the path for personalized radiotherapy.

Augmenting the therapeutic window of radiotherapy: A perspective on molecularly targeted therapies and nanomaterials

Radiation therapy is a cornerstone of modern cancer therapy alongside surgery, chemotherapy, and immunotherapy, with over half of all cancer patients receiving radiation therapy as part of their treatment regimen. Development of novel radiation sensitizers that can improve the therapeutic window of radiation therapy are sought after, particularly for tumors at an elevated risk of local and regional recurrence such as locally-advanced lung, head and neck, and gastrointestinal tumors. This review discusses clinical strategies to enhance radiotherapy efficacy and decrease toxicity, hence, increasing the overall therapeutic window. A focus is given to the molecular targets that have been identified and their associated mechanisms of action in enhancing radiotherapy. Examples include cell survival and proliferation signaling such as the EGFR and PI3K/AKT/mTOR pathways, DNA repair genes including PARP and ATM/ATR, angiogenic growth factors, epigenetic regulators, and immune checkpoint proteins. By manipulating various mechanisms of tumor resistance to ionizing radiation (IR), targeted therapies hold significant value to increase the therapeutic window of radiotherapy. Further, the use of novel nanoparticles to enhance radiotherapy is also reviewed, including nanoparticle delivery of chemotherapies, metallic (high-Z) nanoparticles, and nanoparticle delivery of targeted therapies - all of which may improve the therapeutic window of radiotherapy by enhancing the tumor response to IR or reducing normal tissue toxicity.

DNA Repair and Ovarian Carcinogenesis: Impact on Risk, Prognosis and Therapy Outcome

There is ample evidence for the essential involvement of DNA repair and DNA damage response in the onset of solid malignancies, including ovarian cancer. Indeed, high-penetrance germline mutations in DNA repair genes are important players in familial cancers: BRCA1, BRCA2 mutations or mismatch repair, and polymerase deficiency in colorectal, breast, and ovarian cancers. Recently, some molecular hallmarks (e.g., TP53, KRAS, BRAF, RAD51C/D or PTEN mutations) of ovarian carcinomas were identified. The manuscript overviews the role of DNA repair machinery in ovarian cancer, its risk, prognosis, and therapy outcome. We have attempted to expose molecular hallmarks of ovarian cancer with a focus on DNA repair system and scrutinized genetic, epigenetic, functional, and protein alterations in individual DNA repair pathways (homologous recombination, non-homologous end-joining, DNA mismatch repair, base- and nucleotide-excision repair, and direct repair). We suggest that lack of knowledge particularly in non-homologous end joining repair pathway and the interplay between DNA repair pathways needs to be confronted. The most important genes of the DNA repair system are emphasized and their targeting in ovarian cancer will deserve further attention. The function of those genes, as well as the functional status of the entire DNA repair pathways, should be investigated in detail in the near future.

DNA damage checkpoint kinases in cancer

DNA damage response (DDR) pathway prevents high level endogenous and environmental DNA damage being replicated and passed on to the next generation of cells via an orchestrated and integrated network of cell cycle checkpoint signalling and DNA repair pathways. Depending on the type of damage, and where in the cell cycle it occurs different pathways are involved, with the ATM-CHK2-p53 pathway controlling the G1 checkpoint or ATR-CHK1-Wee1 pathway controlling the S and G2/M checkpoints. Loss of G1 checkpoint control is common in cancer through TP53, ATM mutations, Rb loss or cyclin E overexpression, providing a stronger rationale for targeting the S/G2 checkpoints. This review will focus on the ATM-CHK2-p53-p21 pathway and the ATR-CHK1-WEE1 pathway and ongoing efforts to target these pathways for patient benefit.

The DNA damage response pathway as a land of therapeutic opportunities for colorectal cancer

BACKGROUND

Colorectal cancer (CRC) represents a major cause of cancer deaths worldwide. Although significant progress has been made by molecular and immune therapeutic approaches, prognosis of advanced stage disease is still dismal. Alterations in the DNA damage response (DDR) pathways are emerging as novel targets for treatment across different cancer types. However, even though preclinical studies have shown the potential exploitation of DDR alterations in CRC, systematic and comprehensive testing is lagging and clinical development is based on analogies with other solid tumors according to a tissue-agnostic paradigm. Recently, functional evidence from patient-derived xenografts and organoids have suggested that maintenance with PARP inhibitors might represent a therapeutic opportunity in CRC patients previously responsive to platinum-based treatment.

DESIGN AND RESULTS

In this review, we highlight the most promising preclinical data and systematically summarize published clinical trials in which DDR inhibitors have been used for CRC and provide evidence that disappointing results have been mainly due to a lack of clinical and molecular selection.

CONCLUSIONS

Future preclinical and translational research will help in better understanding the role of DDR alterations in CRC and pave the way to novel strategies that might have a transformative impact on treatment by identifying new therapeutic options including tailored use of standard chemotherapy.

Therapeutic Targets and Opportunities in Endometrial Cancer: Update on Endocrine Therapy and Nonimmunotherapy Targeted Options

Worldwide, the incidence of endometrial cancer is increasing. Although the prognosis remains good for patients diagnosed with early-stage disease, for those diagnosed with recurrent or metastatic disease, options have been limited, and prognosis is short. Optimizing and identifying new well-tolerated treatments for women living with endometrial cancer is a top priority. A new era is dawning where we are starting to see the integration of clinically relevant genomic and pathologic data to inform and refine treatment strategies for women with endometrial cancer. Here, we focus on reviewing nonimmunotherapy-based targeted treatment options and emerging directions for women with endometrial cancer.

Anti-Tumor Effect of Inhibition of DNA Damage Response Proteins, ATM and ATR, in Endometrial Cancer Cells

While the incidence of endometrial cancer continues to rise, the therapeutic options remain limited for advanced or recurrent cases, and most cases are resistant to therapy. The anti-tumor effect of many chemotherapeutic drugs and radiotherapy depends on the induction of DNA damage in cancer cells; thus, activation of DNA damage response (DDR) pathways is considered an important factor affecting resistance to therapy. When some DDR pathways are inactivated, inhibition of other DDR pathways can induce cancer-specific synthetic lethality. Therefore, DDR pathways are considered as promising candidates for molecular-targeted therapy for cancer. The crosstalking ataxia telangiectasia mutated and Rad3 related and checkpoint kinase 1 (ATR-Chk1) and ataxia telangiectasia mutated and Rad3 related and checkpoint kinase 2 (ATM-Chk2) pathways are the main pathways of DNA damage response. In this study, we investigated the anti-tumor effect of inhibitors of these pathways in vitro by assessing the effect of the combination of ATM or ATR inhibitors and conventional DNA-damaging therapy (doxorubicin (DXR), cisplatin (CDDP), and irradiation) on endometrial cancer cells. Both the inhibitors enhanced the sensitivity of cells to DXR, CDDP, and irradiation. Moreover, the combination of ATR and Chk1 inhibitors induced DNA damage in endometrial cancer cells and inhibited cell proliferation synergistically. Therefore, these molecular therapies targeting DNA damage response pathways are promising new treatment strategies for endometrial cancer.

Omega-3 Docosahexaenoic Acid Is a Mediator of Fate-Decision of Adult Neural Stem Cells

The mammalian brain is enriched with lipids that serve as energy catalyzers or secondary messengers of essential signaling pathways. Docosahexaenoic acid (DHA) is an omega-3 fatty acid synthesized de novo at low levels in humans, an endogenous supply from its precursors, and is mainly incorporated from nutrition, an exogeneous supply. Decreased levels of DHA have been reported in the brains of patients with neurodegenerative diseases. Preventing this decrease or supplementing the brain with DHA has been considered as a therapy for the DHA brain deficiency that could be linked with neuronal death or neurodegeneration. The mammalian brain has, however, a mechanism of compensation for loss of neurons in the brain: neurogenesis, the birth of neurons from neural stem cells. In adulthood, neurogenesis is still present, although at a slower rate and with low efficiency, where most of the newly born neurons die. Neural stem/progenitor cells (NSPCs) have been shown to require lipids for proper metabolism for proliferation maintenance and neurogenesis induction. Recent studies have focused on the effects of these essential lipids on the neurobiology of NSPCs. This review aimed to introduce the possible use of DHA to impact NSPC fate-decision as a therapy for neurodegenerative diseases.

DNA damage response and repair in ovarian cancer: Potential targets for therapeutic strategies

Ovarian cancer is among the most lethal gynecologic malignancies with a poor survival prognosis. The current therapeutic strategies involve surgery and chemotherapy. Research is now focused on novel agents especially those targeting DNA damage response (DDR) pathways. Understanding the DDR process in ovarian cancer necessitates having a detailed knowledge on a series of signaling mediators at the cellular and molecular levels. The complexity of the DDR process in ovarian cancer and how this process works in metastatic conditions is comprehensively reviewed. For evaluating the efficacy of therapeutic agents targeting DNA damage in ovarian cancer, we will discuss the components of this system including DDR sensors, DDR transducers, DDR mediators, and DDR effectors. The constituent pathways include DNA repair machinery, cell cycle checkpoints, and apoptotic pathways. We also will assess the potential of active mediators involved in the DDR process such as therapeutic and prognostic candidates that may facilitate future studies.

ATR inhibition sensitizes HPV- and HPV+ head and neck squamous cell carcinoma to cisplatin

OBJECTIVES

Cisplatin is commonly used in the treatment of head and neck squamous cell carcinoma (HNSCC), and the repair of cisplatin-induced DNA damage involves activation of the DNA damage response protein ataxia telangiectasia and Rad3-related (ATR). Resistance to cisplatin therapy exacerbates adverse toxicities and is associated with poor outcomes. Since repair of cisplatin-induced DNA damage contributes to resistance, we hypothesized that inhibition of ATR using AZD6738, a well-tolerated and orally-bioavailable inhibitor, would enhance the sensitivity of HNSCC cells and tumors to cisplatin.

MATERIALS AND METHODS

A panel of human papilloma virus-negative (HPV^-) and HPV⁺ HNSCC cell lines were treated with cisplatin in the absence or presence of AZD6738, and effects on cell viability, colony formation, apoptosis signaling, and DNA damage were assessed. The impact of co-treatment with cisplatin plus AZD6738 on the growth of HPV^- and HPV⁺ cell line- and patient-derived xenograft tumors was also examined.

RESULTS

Inhibition of ATR with AZD6738 enhanced cisplatin-induced growth inhibition of HNSCC cell lines and tumors, in association with increased apoptosis signaling and DNA damage. Both HPV^- and HPV⁺ models were sensitized to cisplatin by ATR inhibition.

CONCLUSION

Inhibition of ATR promotes sensitization to cisplatin in preclinical in vitro and in vivo models of HPV^- and HVP⁺ HNSCC, supporting clinical evaluation of this strategy in this disease.

Stable Acinar Progenitor Cell Model Identifies Treacle-Dependent Radioresistance

Radiotherapy for head and neck cancers can result in extensive damage to the salivary glands, significantly affecting patient quality of life. However, the salivary gland can recover in patients receiving lower doses of radiation. In addition, there is considerable interest in delineating the mechanisms by which stem cells survive radiation exposure and promote tissue regeneration. In this study, we isolated stable radioresistant acinar progenitor cells from the submaxillary gland of the Sprague Dawley rat. Progenitor cells are characterized as c-Kit^high/alpha-amylase⁺ and are resistant to X rays (≤5 Gy).We further isolated a radiosensitive acinar counterpart, characterized as c-Kit^low/alpha-amylase⁺, which is effectively killed by exposure to 2 Gy X ray of radiation. Phosphopeptides with homology to the treacle protein (TCOF1) were disproportionately increased in progenitor cells, compared to their radiosensitive counterparts. Silencing of TCOF1 expression (shRNA) radiosensitized progenitor cells, a response conserved in human cells with TCOF1 knockdown. Collectively, these observations indicate that radiation resistance is an intrinsic property of c-Kit^high salivary gland progenitor cells. Since human salivary gland stem cells with c-Kit expression are believed to have enhanced regenerative potencies, our model system provides a stable platform to investigate molecular features associated with c-Kit expression that may contribute to protection or stabilization of the stem cell niche.

Recent advances of therapeutic targets based on the molecular signature in breast cancer: genetic mutations and implications for current treatment paradigms

Breast cancer is the most common malignancy in women all over the world. Genetic background of women contributes to her risk of having breast cancer. Certain inherited DNA mutations can dramatically increase the risk of developing certain cancers and are responsible for many of the cancers that run in some families. Regarding the widespread multigene panels, whole exome sequencing is capable of providing the evaluation of genetic function mutations for development novel strategy in clinical trials. Targeting the mutant proteins involved in breast cancer can be an effective therapeutic approach for developing novel drugs. This systematic review discusses gene mutations linked to breast cancer, focusing on signaling pathways that are being targeted with investigational therapeutic strategies, where clinical trials could be potentially initiated in the future are being highlighted.

SALL4 induces radioresistance in nasopharyngeal carcinoma via the ATM/Chk2/p53 pathway

Radiotherapy is the mainstay and primary curative treatment modality in nasopharyngeal carcinoma (NPC), whose efficacy is limited by the development of intrinsic and acquired radioresistance. Thus, deciphering new molecular targets and pathways is essential for enhancing the radiosensitivity of NPC. SALL4 is a vital factor in the development and prognosis of various cancers, but its role in radioresistance remains elusive. This study aimed to explore the association of SALL4 expression with radioresistance of NPC. It was revealed that SALL4 expression was closely correlated with advanced T classification of NPC patients. Inhibition of SALL4 reduced proliferation and sensitized cells to radiation both in vitro and in vivo. Furthermore, SALL4 silencing increased radiation-induced DNA damage, apoptosis, and G2/M arrest in CNE2 and CNE2R cells. Moreover, knockdown of SALL4 impaired the expression of p-ATM, p-Chk2, p-p53, and anti-apoptosis protein Bcl-2, while pro-apoptosis protein was upregulated. These findings indicate that SALL4 could induce radioresistance via ATM/Chk2/p53 pathway and its downstream proteins related to apoptosis. Targeting SALL4 might be a promising approach for the development of novel radiosensitizing therapeutic agents for radioresistant NPC patients.

Evaluation of ATM Kinase Inhibitor KU-55933 as Potential Anti-Toxoplasma gondii Agent

Toxoplasma gondii is an apicomplexan protozoan parasite with a complex life cycle composed of multiple stages that infect mammals and birds. Tachyzoites rapidly replicate within host cells to produce acute infection during which the parasite disseminates to tissues and organs. Highly replicative cells are subject to Double Strand Breaks (DSBs) by replication fork collapse and ATM, a member of the phosphatidylinositol 3-kinase (PI3K) family, is a key factor that initiates DNA repair and activates cell cycle checkpoints. Here we demonstrate that the treatment of intracellular tachyzoites with the PI3K inhibitor caffeine or ATM kinase-inhibitor KU-55933 affects parasite replication rate in a dose-dependent manner. KU-55933 affects intracellular tachyzoite growth and induces G1-phase arrest. Addition of KU-55933 to extracellular tachyzoites also leads to a significant reduction of tachyzoite replication upon infection of host cells. ATM kinase phosphorylates H2A.X (γH2AX) to promote DSB damage repair. The level of γH2AX increases in tachyzoites treated with camptothecin (CPT), a drug that generates fork collapse, but this increase was not observed when co-administered with KU-55933. These findings support that KU-55933 is affecting the Toxoplasma ATM-like kinase (TgATM). The combination of KU-55933 and other DNA damaging agents such as methyl methane sulfonate (MMS) and CPT produce a synergic effect, suggesting that TgATM kinase inhibition sensitizes the parasite to damaged DNA. By contrast, hydroxyurea (HU) did not further inhibit tachyzoite replication when combined with KU-55933.

Low ATM expression and progression-free and overall survival in advanced gastric cancer patients treated with first-line XELOX chemotherapy

BACKGROUND

Gastric cancer (GC) is a leading cause of cancer-specific mortality with limited biologically informed treatments. The ataxia telangiectasia mutated (ATM) gene is critically involved in the repair of double-stranded DNA breaks and a component of DNA damage repair (DDR) pathways. Platinum salts are hypothesized to have increased efficacy in tumors deficient in DDR pathways. We sought to investigate an association between ATM status and response to XELOX in a homogenous first line GC patient cohort.

METHODS

A clinically annotated cohort of 137 Korean patients with advanced GC treated with first-line XELOX was retrospectively examined for ATM status by immunohistochemistry. Correlation between ATM expression and clinicopathologic variables was performed by two-tailed, unpaired t-tests and Fisher's exact tests. Kaplan-Meier survival analysis curves and Cox proportional hazards models were used to evaluate for independent predictors of disease-free survival (DFS) and overall survival (OS).

RESULTS

Low ATM expression was observed in 19.0% (26/137) of patients and was not associated with clinicopathologic features or response rate to XELOX. Univariate, but not multivariable, logistic regression and Cox analysis identified ATM as an independent risk factor influencing OS and DFS. A higher ECOG score independently predicted worse survival [hazard ratio (HR) 2.96, P=0.016] and complete surgical resection independently protected against progression of disease (HR 0.69, P=0.007).

CONCLUSIONS

Low ATM expression was not associated with increased response rates to XELOX in a single-institution cohort of advanced GC patients. Similarly, ATM status did not predict DFS or OS after platinum-based chemotherapy.

Mutagenic assessment of chemotherapy and Smac mimetic drugs in cells with defective DNA damage response pathways

DNA damaging therapies can spur the formation of therapy-related cancers, due to mis-repair of lesions they create in non-cancerous cells. This risk may be amplified in patients with impaired DNA damage responses. We disabled key DNA damage response pathways using genetic and pharmacological approaches, and assessed the impact of these deficiencies on the mutagenicity of chemotherapy drugs or the "Smac mimetic" GDC-0152, which kills tumor cells by targeting XIAP, cIAP1 and 2. Doxorubicin and cisplatin provoked mutations in more surviving cells deficient in ATM, p53 or the homologous recombination effector RAD51 than in wild type cells, but suppressing non-homologous end joining (NHEJ) by disabling DNA-PKcs prevented chemotherapy-induced mutagenesis. Vincristine-induced mutagenesis required p53 and DNA-PKcs but was not affected by ATM status, consistent with it provoking ATM-independent p53-mediated activation of caspases and CAD, which creates DNA lesions in surviving cells that could be mis-repaired by NHEJ. Encouragingly, GDC-0152 failed to stimulate mutations in cells with proficient or defective DNA damage response pathways. This study highlights the elevated oncogenic risk associated with treating DNA repair-deficient patients with genotoxic anti-cancer therapies, and suggests a potential advantage for Smac mimetic drugs over traditional therapies: a reduced risk of therapy-related cancers.

Discovery of a Series of 3-Cinnoline Carboxamides as Orally Bioavailable, Highly Potent, and Selective ATM Inhibitors

We report the discovery of a novel series of 3-cinnoline carboxamides as highly potent and selective ataxia telangiectasia mutated (ATM) kinase inhibitors. Optimization of this series focusing on potency and physicochemical properties (especially permeability) led to the identification of compound 21, a highly potent ATM inhibitor (ATM cell IC₅₀ 0.0028 μM) with excellent kinase selectivity and favorable physicochemical and pharmacokinetics properties. In vivo, 21 in combination with irinotecan showed tumor regression in the SW620 colorectal tumor xenograft model, superior inhibition to irinotecan alone. Compound 21 was selected for preclinical evaluation alongside AZD0156.

Dual inhibition of ATR and ATM potentiates the activity of trabectedin and lurbinectedin by perturbing the DNA damage response and homologous recombination repair

Trabectedin (Yondelis^®, ecteinascidin-743, ET-743) is a marine-derived natural product approved for treatment of advanced soft tissue sarcoma and relapsed platinum-sensitive ovarian cancer. Lurbinectedin is a novel anticancer agent structurally related to trabectedin. Both ecteinascidins generate DNA double-strand breaks that are processed through homologous recombination repair (HRR), thereby rendering HRR-deficient cells particularly sensitive. We here characterize the DNA damage response (DDR) to trabectedin and lurbinectedin in HeLa cells. Our results show that both compounds activate the ATM/Chk2 (ataxia-telangiectasia mutated/checkpoint kinase 2) and ATR/Chk1 (ATM and RAD3-related/checkpoint kinase 1) pathways. Interestingly, pharmacological inhibition of Chk1/2, ATR or ATM is not accompanied by any significant improvement of the cytotoxic activity of the ecteinascidins while dual inhibition of ATM and ATR strongly potentiates it. Accordingly, concomitant inhibition of both ATR and ATM is an absolute requirement to efficiently block the formation of γ-H2AX, MDC1, BRCA1 and Rad51 foci following exposure to the ecteinascidins. These results are not restricted to HeLa cells, but are shared by cisplatin-sensitive and -resistant ovarian carcinoma cells. Together, our data identify ATR and ATM as central coordinators of the DDR to ecteinascidins and provide a mechanistic rationale for combining these compounds with ATR and ATM inhibitors.