Radiation-induced YAP activation confers glioma radioresistance via promoting FGF2 transcription and DNA damage repair

Targeting the Hippo pathway to prevent radioresistance brain metastases from the lung (Review)

The prognosis for patients with non‑small cell lung cancer (NSCLC), a cancer type which represents 85% of all lung cancers, is poor with a 5‑year survival rate of 19%, mainly because NSCLC is diagnosed at an advanced and metastatic stage. Despite recent therapeutic advancements, ~50% of patients with NSCLC will develop brain metastases (BMs). Either surgical BM treatment alone for symptomatic patients and patients with single cerebral metastases, or in combination with stereotactic radiotherapy (RT) for patients who are not suitable for surgery or presenting with fewer than four cerebral lesions with a diameter range of 5‑30 mm, or whole‑brain RT for numerous or large BMs can be administered. However, radioresistance (RR) invariably prevents the action of RT. Several mechanisms of RR have been described including hypoxia, cellular stress, presence of cancer stem cells, dysregulation of apoptosis and/or autophagy, dysregulation of the cell cycle, changes in cellular metabolism, epithelial‑to‑mesenchymal transition, overexpression of programmed cell death‑ligand 1 and activation several signaling pathways; however, the role of the Hippo signaling pathway in RR is unclear. Dysregulation of the Hippo pathway in NSCLC confers metastatic properties, and inhibitors targeting this pathway are currently in development. It is therefore essential to evaluate the effect of inhibiting the Hippo pathway, particularly the effector yes‑associated protein‑1, on cerebral metastases originating from lung cancer.

Role of renin angiotensin system inhibitors and metformin in Glioblastoma Therapy: a review

Glioblastoma multiforme (GBM) is a highly aggressive and incurable disease accounting for about 10,000 deaths in the USA each year. Despite the current treatment approach which includes surgery with chemotherapy and radiation therapy, there remains a high prevalence of recurrence. Notable improvements have been observed in persons receiving concurrent antihypertensive drugs such as renin angiotensin inhibitors (RAS) or the antidiabetic drug metformin with standard therapy. Anti-tumoral effects of RAS inhibitors and metformin have been observed in in vitro and in vivo studies. Although clinical trials have shown mixed results, the potential for the use of RAS inhibitors and metformin as adjuvant GBM therapy remains promising. Nevertheless, evidence suggest that these drugs exert multimodal antitumor actions; by particularly targeting several cancer hallmarks. In this review, we highlight the results of clinical studies using multidrug cocktails containing RAS inhibitors and or metformin added to standard therapy for GBM. In addition, we highlight the possible molecular mechanisms by which these repurposed drugs with an excellent safety profile might elicit their anti-tumoral effects. RAS inhibition elicits anti-inflammatory, anti-angiogenic, and immune sensitivity effects in GBM. However, metformin promotes anti-migratory, anti-proliferative and pro-apoptotic effects mainly through the activation of AMP-activated protein kinase. Also, we discussed metformin's potential in targeting both GBM cells as well as GBM associated-stem cells. Finally, we summarize a few drug interactions that may cause an additive or antagonistic effect that may lead to adverse effects and influence treatment outcome.

Differential Sensitivity to Ionizing Radiation in Gemcitabine-Resistant and Paclitaxel-Resistant Pancreatic Cancer Cells

PURPOSE

Chemoresistance remains a major challenge in treating pancreatic ductal adenocarcinoma (PDAC). Although chemoradiation has proven effective in other tumor types, such as head and neck squamous cell carcinoma, its role in PDAC and effect on acquired chemoresistance have yet to be fully explored. In this study, we investigated the sensitivity of gemcitabine-resistant (GR) and paclitaxel-resistant (PR) PDAC cells to ionizing radiation (IR) and their underlying mechanisms.

METHODS AND MATERIALS

GR and PR clones were generated from PANC-1, PATU-T, and SUIT2-007 pancreatic cancer cell lines. Cell survival after radiation was assessed using clonogenic assay, sulforhodamine B assay, apoptosis, and spheroid growth by bioluminescence. Radiation-induced DNA damage was assessed using Western blot, extra-long polymerase chain reaction, reactive oxygen species production, and immunofluorescence. Autophagy and modulation of the Hippo signaling pathway were investigated using proteomics, Western blot, immunofluorescence, and reverse-transcription quantitative polymerase chain reaction.

RESULTS

In both 2- and 3-dimensional settings, PR cells were more sensitive to IR and showed decreased β-globin amplification, indicating more DNA damage accumulation compared with GR or wild-type cells after 24 hours. Proteomic analysis of PR PATU-T cells revealed that the protein MST4, a kinase involved in autophagy and the Hippo signaling pathway, was highly downregulated. A differential association was found between autophagy and radiation treatment depending on the cell model. Interestingly, increased yes-associated protein nuclear localization and downstream Hippo signaling pathway target gene expression were observed in response to IR.

CONCLUSIONS

This was the first study investigating the potential of IR in targeting PDAC cells with acquired chemoresistance. Our results demonstrate that PR cells exhibit enhanced sensitivity to IR due to greater accumulation of DNA damage. Additionally, depending on the specific cellular context, radiation-induced modulation of autophagy and the Hippo signaling pathway emerged as potential underlying mechanisms, findings with potential to inform personalized treatment strategies for patients with acquired chemoresistance.

The transcription factor GATA3 positively regulates NRP1 to promote radiation-induced pulmonary fibrosis

Radiation-Induced Pulmonary Fibrosis (RIPF) frequently arises as a delayed complication following radiation therapy for thoracic cancers, encompassing lung, breast, and esophageal malignancies. Characterized by a relentless and irreversible accumulation of extracellular matrix (ECM) proteins within the lung parenchyma, RIPF presents a significant clinical challenge. While the modulation of gene expression by transcription factors is a recognized aspect in various pathologies, their specific role in the context of RIPF has been less clear. This study elucidates that ionizing radiation prompts the translocation of the transcription factor GATA3 into the nucleus. This translocation facilitates GATA3's binding to the NRP1 promoter, thereby enhancing the transcription and subsequent translation of NRP1. Further investigations demonstrate that the TGF-β pathway agonist, SRI-011381, can mitigate the effects of NRP1 knockdown on epithelial-mesenchymal transition (EMT) and ECM deposition, suggesting a pivotal role of the GATA3/NRP1/TGF-β axis in the pathogenesis of RIPF. In conclusion, our findings not only underscore the critical involvement of GATA3 in RIPF but also highlight the GATA3/NRP1/TGF-β signaling pathway as a promising target for therapeutic intervention in RIPF management.

E2F3/5/8 serve as potential prognostic biomarkers and new therapeutic direction for human bladder cancer

OBJECTS

Human bladder cancer (BC) is the most common urogenital system malignancy. E2F transcription factors (E2Fs) have been reported to be involved in the growth of various cancers. However, the expression patterns, prognostic value and immune infiltration in the tumor microenvironment of the 8 E2Fs in BC have yet fully to be explored.

METHODS AND STRATEGY

We investigated the differential expression of E2Fs in BC patients, the prognostic value and correlation with immune infiltration by analyzing a range of databases.

RESULTS

We found that the mRNA expression levels of E2F1/2/3/4/5/7/8 were significantly higher in BC patients than that of control tissues. And the increased mRNA expression levels of all E2Fs were associated with tumor stage of BC. The survival analysis revealed that the elevated mRNA expression levels of E2F3/5/8 were significantly correlated with the overall survival (OS) of BC patients. And the genetic changes of E2Fs in BC patients were associated with shorter overall survival (OS) and progression-free survival (PFS). In addition, we revealed that the E2F3/5/8 expressions were closely correlated with tumor-infiltrating lymphocytes (TILs).

CONCLUSIONS

E2F3/5/8 might serve as promising prognostic biomarkers and new therapeutic direction for BC patients.

Role of YAP Signaling in Regulation of Programmed Cell Death and Drug Resistance in Cancer

Although recent advances in cancer treatment significantly improved the prognosis of patients, drug resistance remains a major challenge. Targeting programmed cell death is a major approach of antitumor drug development. Deregulation of programmed cell death (PCD) contributes to resistance to a variety of cancer therapeutics. Yes-associated protein (YAP) and its paralog TAZ, the main downstream effectors of the Hippo pathway, are aberrantly activated in a variety of human malignancies. The Hippo-YAP pathway, which was originally identified in Drosophila, is well conserved in humans and plays a defining role in regulation of cell fate, tissue growth and regeneration. Activation of YAP signaling has emerged as a key mechanism involved in promoting cancer cell proliferation, metastasis, and drug resistance. Understanding the role of YAP/TAZ signaling network in PCD and drug resistance could facilitate the development of effective strategies for cancer therapeutics.

YY1 modulates the radiosensitivity of esophageal squamous cell carcinoma through KIF3B-mediated Hippo signaling pathway

Radiotherapy is an important strategy in the comprehensive treatment of esophageal squamous cell carcinoma (ESCC). However, effectiveness of radiotherapy is still restricted by radioresistance. Herein, we aimed to understand the mechanisms underlying ESCC radioresistance, for which we looked into the potential role of YY1. YY1 was upregulated in radioresistant tissues and correlated with poor prognosis of patients with ESCC. YY1 depletion enhanced the radiosensitivity of ESCC in vitro and in vivo. Multi-group sequencing showed that downregulation of YY1 inhibited the transcriptional activity of Kinesin Family Member 3B (KIF3B), which further activated the Hippo signaling pathway by interacting with Integrin-beta1 (ITGB1). Once the Hippo pathway was activated, its main effector, Yes-associated protein 1 (YAP1), was phosphorylated in the cytoplasm and its expression reduced in the nucleus, thus enhancing the radiosensitivity by regulating its targeted genes. Our study provides new insights into the mechanisms underlying ESCC radioresistance and highlights the potential role of YY1 as a therapeutic target for ESCC.

Carbon ions trigger DNA damage response to overcome radioresistance by regulating β-catenin signaling in quiescent HeLa cells

Quiescent cancer cells are major impediments to effective radiotherapy (RT) and exhibit limited sensitivity to traditional photon therapy. Herein, the functional role and underlying mechanism of carbon ions in overcoming the radioresistance of quiescent cervical cancer HeLa cells were determined. Briefly, serum withdrawal was used to induce synchronized quiescence in HeLa cells. Quiescent HeLa cells displayed strong radioresistance and DNA repair potential. After irradiation with carbon ions, the DNA damage repair pathway may markedly rely on error-prone nonhomologous end-joining in proliferating cells, whereas the high-precision homologous recombination pathway is more relevant in quiescent cells. This phenomenon could be explained by the ionizing radiation (IR)-induced cell cycle re-entry of quiescent cancer cells. There are three strategies for eradicating quiescent cancer cells using high-linear energy transfer (LET) carbon ions: direct cell death through complex DNA damage; apoptosis via an enhanced mitochondria-mediated intrinsic pathway; forced re-entry of quiescent cancer cells into the cell cycle, thereby improving their susceptibility to IR. Silencing β-catenin signaling is essential for maintaining the dormant state in quiescent cells. Herein, carbon ions activated the β-catenin pathway in quiescent cells, and inhibition of this pathway improved the resistance of quiescent HeLa cells to carbon ions by alleviating DNA damage, improving DNA damage repair, maintaining quiescent depth, and inhibiting apoptosis. Collectively, carbon ions conquer the radioresistance of quiescent HeLa cells by activating β-catenin signaling, which provides a theoretical basis for improved therapeutic effects in patients with middle-advanced-stage cervical cancer with radioresistance.

Reduced YAP1 and FOLR1 in gliomas predict better response to chemotherapeutics

Gliomas harbouring mutations in IDH1 (isocitrate dehydrogenase 1) are characterized by greater sensitivity to chemotherapeutics. These mutants also exhibit diminished levels of transcriptional coactivator YAP1 (yes-associated protein 1). Enhanced DNA damage in IDH1 mutant cells, as evidenced by γH2AX formation (phosphorylation of histone variant H2A.X) and ATM (serine/threonine kinase; ataxia telangiectasia mutated) phosphorylation, was accompanied by reduced FOLR1 (folate receptor 1) expression. Diminished FOLR1, concomitant with heightened γH2AX levels, was also observed in patient-derived IDH1 mutant glioma tissues. Chromatin immunoprecipitation, overexpression of mutant YAP1, and treatment with YAP1-TEAD (TEA domain transcription factors) complex inhibitor verteporfin demonstrated regulation of FOLR1 expression by YAP1 and its partner transcription factor TEAD2. TCGA (The Cancer Genome Atlas) data analysis demonstrated better patient survival with reduced FOLR1 expression. Depletion of FOLR1 rendered IDH1 wild-type gliomas more susceptible to temozolomide-mediated death. Despite heightened DNA damage, IDH1 mutants exhibited reduced levels of IL6 (interleukin 6) and IL8 (interleukin 8) - pro-inflammatory cytokines known to be associated with persistent DNA damage. While both FOLR1 and YAP1 influenced DNA damage, only YAP1 was involved in regulating IL6 and IL8. ESTIMATE and CIBERSORTx analyses revealed the association between YAP1 expression and immune cell infiltration in gliomas. By identifying the influence of YAP1-FOLR1 link in DNA damage, our findings suggest that simultaneous depletion of both could amplify the potency of DNA damaging agents, while concomitantly reducing the release of inflammatory mediators and potentially affecting immune modulation. This study also highlights the novel role of FOLR1 as a probable prognostic marker in gliomas, predicting responsiveness to temozolomide and other DNA damaging agents.

Most recent update of preclinical and clinical data on radioresistance and radiosensitivity of high-grade gliomas-a radiation oncologist's perspective

PURPOSE

This review article discusses the studies concerning advances in radiotherapy of high-grade gliomas published in the second half of 2021.

METHODS

A literature search was performed in PubMed using the terms ("gliom* and radio*") and time limits 1 July 2021-31 December 2021. The articles were then manually selected for relevance to the analyzed topics.

RESULTS

Considerable progress has been made in the preclinical field on the mechanisms of radioresistance and radiosensitization of high-grade gliomas (HGG). However, fewer early-phase (I/II) clinical trials have been performed and, of the latter, even fewer have produced results that justify moving to phase III. In the 6‑month period under consideration, no studies were published that would lead to a change in clinical practice and the overall survival (OS) of patients remained similar to that of 2005, the year in which it increased significantly for the last time thanks to introduction of the alkylating agent temozolomide.

CONCLUSION

After 17 years of stalemate in improving the OS of patients with HGG, an in-depth analysis of the causes should be carried out in order to identify whether the research efforts conducted so far, including in the radiotherapeutic field, have been the most effective or require improvement. In our opinion, in addition to the therapeutic difficulties related to the biology of HGG tumors (e.g., high infiltrating capacity, multiple resistance mechanisms, blood-brain barrier), some public research policy choices may also play a role, especially in consideration of the limited interest of the pharmaceutical industry in the field of rare cancers.

Epigenetic regulation of radioresistance: insights from preclinical and clinical studies

INTRODUCTION

Oftentimes, radiation therapy (RT) is ineffective due to the development of radioresistance (RR). However, studies have shown that targeting epigenetic modifiers to enhance radiosensitivity represents a promising direction of clinical investigation.

AREAS COVERED

This review discusses the mechanisms by which epigenetic modifiers alter radiosensitivity through dysregulation of MAPK-ERK and AKT-mTOR signaling. Finally, we discuss the clinical directions for targeting epigenetic modifiers and current radiology techniques used in the clinic.

METHODOLOGY

We searched PubMed and ScienceDirect databases from April 4^th, 2022 to October 18^th, 2022. We examined 226 papers related to radioresistance, epigenetics, MAPK, and PI3K/AKT/mTOR signaling. 194 papers were selected for this review. Keywords used for this search include, 'radioresistance,' 'radiosensitivity,' 'radiation,' 'radiotherapy,' 'particle radiation,' 'photon radiation,' 'epigenetic modifiers,' 'MAPK,' 'AKT,' 'mTOR,' 'cancer,' and 'PI3K.' We examined 41 papers related to clinical trials on the aforementioned topics. Outcomes of interest were safety, overall survival (OS), dose-limiting toxicities (DLT), progression-free survival (PFS), and maximum tolerated dose (MTD).

EXPERT OPINION

Current studies focusing on epigenetic mechanisms of RR strongly support the use of targeting epigenetic modifiers as adjuvants to standard cancer therapies. To further the success of such treatments and their clinical benefit , both preclinical and clinical studies are needed to broaden the scope of known radioresistant mechanisms.

The Molecular and Cellular Strategies of Glioblastoma and Non-Small-Cell Lung Cancer Cells Conferring Radioresistance

Ionizing radiation (IR) has been shown to play a crucial role in the treatment of glioblastoma (GBM; grade IV) and non-small-cell lung cancer (NSCLC). Nevertheless, recent studies have indicated that radiotherapy can offer only palliation owing to the radioresistance of GBM and NSCLC. Therefore, delineating the major radioresistance mechanisms may provide novel therapeutic approaches to sensitize these diseases to IR and improve patient outcomes. This review provides insights into the molecular and cellular mechanisms underlying GBM and NSCLC radioresistance, where it sheds light on the role played by cancer stem cells (CSCs), as well as discusses comprehensively how the cellular dormancy/non-proliferating state and polyploidy impact on their survival and relapse post-IR exposure.

Protein tyrosine phosphatase PTPL1 suppresses lung cancer through Src/ERK/YAP1 signaling

BACKGROUND

To reveal the function of protein tyrosine phosphatase-L1 (PTPL1) in lung adenocarcinoma.

METHODS

Lung cancer cell lines were transfected with short hairpin RNA against PTPL1 (shPTPL1 group) or negative control (shmock group). Quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting were used to verify the transfection efficacy. Cell proliferation was analyzed by ethynyldeoxyuridine (EdU), Cell counting kit 8 (CCK8), and colony formation assay after PTPL1 or PTPL1 and yes-associated protein (YAP1) knockdown. The effect of PTPL1 on tumor growth was examined in a xenograft lung cancer model.

RESULTS

PTPL1 was downregulated in various types of lung cancer cell lines. The EdU, CCK8, colony formation assays and investigation using a xenograft lung cancer model indicated that PTPL1 knockdown increased the proliferation of lung cancer cells. Mechanistically, PTPL1 knockdown induced the activation of the Proto-oncogene tyrosine-protein kinase SRC (Src)/Extracellular regulated MAP kinase (ERK) pathway and thereby promoted yes-associated protein (YAP1) nuclear translocation and activation.

CONCLUSIONS

In our study, PTPL1 played a crucial suppressive role in the pathogenesis of lung cancer potentially through counteracting the Src/ERK/YAP1 pathway.

Effect of mechanical forces on cellular response to radiation

While the cellular interactions and biochemical signaling has been investigated for long and showed to play a major role in the cell's fate, it is now also evident that mechanical forces continuously applied to the cells in their microenvironment are as important for tissue homeostasis. Mechanical cues are emerging as key regulators of cellular drug response and we aimed to demonstrate in this review that such effects should also be considered vital for the cellular response to radiation. In order to explore the mechanobiology of the radiation response, we reviewed the main mechanoreceptors and transducers, including integrin-mediated adhesion, YAP/TAZ pathways, Wnt/β-catenin signaling, ion channels and G protein-coupled receptors and showed their implication in the modulation of cellular radiosensitivity. We then discussed the current studies that investigated a direct effect of mechanical stress, including extracellular matrix stiffness, shear stress and mechanical strain, on radiation response of cancer and normal cells and showed through preliminary results that such stress effectively can alter cell response after irradiation. However, we also highlighted the limitations of these studies and emphasized some of the contradictory data, demonstrating that the effect of mechanical cues could involve complex interactions and potential crosstalk with numerous cellular processes also affected by irradiation. Overall, mechanical forces alter radiation response and although additional studies are required to deeply understand the underlying mechanisms, these effects should not be neglected in radiation research as they could reveal new fundamental knowledge for predicting radiosensitivity or understanding resistance to radiotherapy.

Feedforward loop between IMP1 and YAP/TAZ promotes tumorigenesis and malignant progression in glioblastoma

YAP/TAZ have been identified as master regulators in malignant phenotypes of glioblastoma (GBM); however, YAP/TAZ transcriptional disruptor in GBM treatment remains ineffective. Whether post-transcriptional dysregulation of YAP/TAZ improves GBM outcome is currently unknown. Here, we report that insulin-like growth factor 2 (IGF2) mRNA-binding protein 1 (IGF2BP1 or IMP1) is upregulated in mesenchymal GBM compared with proneural GBM and correlates with worse patient outcome. Overexpression of IMP1 in proneural glioma stem-like cells (GSCs) promotes while IMP1 knockdown in mesenchymal GSCs attenuates tumorigenesis and mesenchymal signatures. IMP1 binds to and stabilizes m6A-YAP mRNA, leading to activation of YAP/TAZ signaling, depending on its m6A recognition and binding domain. On the other hand, TAZ functions as enhancer for IMP1 expression. Collectively, our data reveal a feedforward loop between IMP1 and YAP/TAZ maintaining GBM/GSC tumorigenesis and malignant progression and a promising molecular target in GBM.

CD146 interaction with integrin β1 activates LATS1-YAP signaling and induces radiation-resistance in breast cancer cells

Radiotherapy is an indispensable modality in comprehensive treatment of breast cancer. However, inherent or acquired radiation resistance of tumors compromises the efficacy of radiotherapy. Herein, we found that CD146, a unique epithelial-to-mesenchymal transition (EMT) inducer particularly highly expressed in triple-negative breast cancer (TNBC), is dramatically induced by ionizing irradiation. Further study demonstrates that CD146 promotes tumor cell radioresistance in vitro and in vivo. Specifically, we report the underlying mechanism that CD146 activates YAP protein, and drives its relocation from plasma to nucleus by regulating LATS1, and promoting abnormal DNA damage repair, as well as inducing EMT and stemness. Moreover, CD146 can form a novel co-receptor complex with integrin β1 and induces radiation-resistance in breast cancer. Dual inhibition of CD146 and integrin β1 activity had a stronger inhibitory effect on breast cancer tumor growth and synergistically increased their sensitivity to radiotherapy. This study identifies a unique function of CD146 implicates with integrin β1 and YAP signaling, contributing to radiation resistance. Targeted therapy against CD146 or inhibition of integrin β1 is a potential strategy to overcome radiotherapeutic resistance of breast cancer.

Recent insight into the role and therapeutic potential of YAP/TAZ in gastrointestinal cancers

With the rapid development of cancer treatment, gastrointestinal (GI) cancers are still the most prevalent malignancies with high morbidity and mortality worldwide. Dysregulation of the Hippo signaling pathway has been recognized to play a critical role during cancer development and adopted for monitoring disease progression and therapy response. Despite the well-documented tumor proliferation and metastasis, recent efforts in two core Hippo components, Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ), have identified as the driving forces behind cancer metabolism, stemness, tumor immunity, and therapy resistance. Understanding the molecular mechanisms by which YAP/TAZ facilitates the tumorigenesis and progression of GI cancer, and identifying novel therapeutic strategies for targeting YAP/TAZ are crucial to GI cancer treatment and prevention. In this study, we summarize the latest findings on the function and regulatory mechanisms of YAP/TAZ in GI cancers, and highlight the translational significance of targeting YAP/TAZ for cancer therapies.

Radiation therapy affects YAP expression and intracellular localization by modulating lamin A/C levels in breast cancer

The microenvironment of breast cancer actively participates in tumorigenesis and cancer progression. The changes observed in the architecture of the extracellular matrix initiate an oncogene-mediated cell reprogramming, that leads to a massive triggering of YAP nuclear entry, and, therefore, to cancer cell proliferation, invasion and probably to increased radiation-resistance. However, it is not yet fully understood how radiotherapy regulates the expression and subcellular localization of YAP in breast cancer cells experiencing different microenvironmental stiffnesses. To elucidate the role of extracellular matrix stiffness and ionizing radiations on YAP regulation, we explored the behaviour of two different mammary cell lines, a normal epithelial cell line (MCF10A) and a highly aggressive and invasive adenocarcinoma cell line (MDA-MB-231) interacting with polyacrylamide substrates mimicking the mechanics of both normal and tumour tissues (∼1 and ∼13 kPa). We report that X-ray radiation affected in a significant way the levels of YAP expression, density, and localization in both cell lines. After 24 h, MCF10A and MDA-MB-231 increased the expression level of YAP in both nucleus and cytoplasm in a dose dependent manner and particularly on the stiffer substrates. After 72 h, MCF10A reduced mostly the YAP expression in the cytoplasm, whereas it remained high in the nucleus of cells on stiffer substrates. Tumour cells continued to exhibit higher levels of YAP expression, especially in the cytoplasmic compartment, as indicated by the reduction of nuclear/cytoplasmic ratio of total YAP. Then, we investigated the existence of a correlation between YAP localization and the expression of the nuclear envelope protein lamin A/C, considering its key role in modulating nuclear deformability and changes in YAP shuttling phenomena. As supposed, we found that the effects of radiation on YAP nucleus/cytoplasmic expression ratio, increasing in healthy cells and decreasing in tumour ones, were accompanied by lower and higher lamin A/C levels in MCF10A and MDA-MB-231 cells, respectively. These findings point to obtain a deeper knowledge of the role of the extracellular matrix and the effects of X-rays on YAP and lamin A/C expression that can be used in the design of doses and timing of radiation therapy.

SU4312 Represses Glioma Progression by Inhibiting YAP and Inducing Sensitization to the Effect of Temozolomide

SU4312, initially designed as a multi-target tyrosine kinase inhibitor, is consequently reported to inhibit tumor angiogenesis by blocking VEGFR. However, although SU4312 can penetrate the brain–blood barrier, its potential to inhibit glioma growth is unknown. In this study, we report that SU4312 inhibited glioma cell proliferation and down-regulated yes-associated protein (YAP), the key effector of the hippo pathway. The exogenous over-expression of YAP partially restored the inhibitory effect of SU4312 on glioma progression. Interestingly, SU4312 sensitized the antitumor effect of temozolomide, both in vitro and in vivo. Moreover, SU4312 decreased the M2tumor-associated macrophages and enhanced anti-tumor immunity by down-regulating the YAP-CCL2 axis. In conclusion, our results suggest that SU4312 represses glioma progression by down-regulating YAP transcription and consequently CCL2 secretion. SU4312 may be synergistic with temozolomide for glioma treatment.

Interplay of Developmental Hippo-Notch Signaling Pathways with the DNA Damage Response in Prostate Cancer

Prostate cancer belongs in the class of hormone-dependent cancers, representing a major cause of cancer incidence in men worldwide. Since upon disease onset almost all prostate cancers are androgen-dependent and require active androgen receptor (AR) signaling for their survival, the primary treatment approach has for decades relied on inhibition of the AR pathway via androgen deprivation therapy (ADT). However, following this line of treatment, cancer cell pools often become resistant to therapy, contributing to disease progression towards the significantly more aggressive castration-resistant prostate cancer (CRPC) form, characterized by poor prognosis. It is, therefore, of critical importance to elucidate the molecular mechanisms and signaling pathways underlying the progression of early-stage prostate cancer towards CRPC. In this review, we aim to shed light on the role of major signaling pathways including the DNA damage response (DDR) and the developmental Hippo and Notch pathways in prostate tumorigenesis. We recapitulate key evidence demonstrating the crosstalk of those pathways as well as with pivotal prostate cancer-related 'hubs' such as AR signaling, and evaluate the clinical impact of those interactions. Moreover, we attempt to identify molecules of the complex DDR-Hippo-Notch interplay comprising potentially novel therapeutic targets in the battle against prostate tumorigenesis.

Far beyond anti-angiogenesis: Benefits for anti-basicFGF therapy in cancer

Basic FGF (bFGF) was discovered as a typical inducer of angiogenesis and has already been studied for 3 decades. Recent evidence indicates that bFGF plays different roles and controls signaling pathways that participate in the hallmarks of cancer, underscoring bFGF an appealing target for anti-cancer therapy. However, the early clinical trials designed to block bFGF signaling showed safety without satisfiable benefits for cancer patients. In this review, we firstly discuss bFGF's canonical signaling pathways and later review newly identified bFGF's functions that contribute to the cancer hallmarks besides its typical role in angiogenesis. After, we summarize the role of bFGF as a therapeutic target in response to different cancer therapies including radiotherapy, chemotherapy, targeted therapy, immunotherapy, and highlight the difficulties we must solve regarding the design of drugs targeting specifically bFGF. We also emphasize the need, especially for natural bFGF traps, to deepen their molecular mechanisms of action considering the specific context of cancer with different FGFR status, as well as the urgence of stratifying patients for both anti-bFGF first line and second line anti-cancer therapy. Finally, a perspective on potential feed-forward oncogenic signaling pathways mediated by bFGF is made. We discuss the importance of developing additional robust biomarkers to select patients who will benefit from bFGF-targeted therapy, as well as the rationale of developing combinatory therapies targeting either bFGF and/or its intracellular (co)effectors. This would ultimately provide novel therapeutic strategies to fight cancer.

CD155 promotes radioresistance and malignancy of esophageal cancer by regulating Hippo-YAP pathway

The expression of CD155 has been observed to increase in various human cancers, but its role in the development of esophageal cancer (EC) is unclear. Radiotherapy is one of the primary therapeutic options for EC. However, radioresistance is still a severe issue in EC treatment. In this study, Oncomine database mining, immunohistochemistry, and survival analysis showed that higher expression of CD155 in patients with EC than in healthy controls. In vitro and in vivo, we found for the first time that irradiation increased the expression of CD155 in EC cells. CD155 knockdown inhibited cell proliferation and migration and tumor formation, and significantly increased radiosensitivity in EC. The in vivo model with high CD155 expression significantly promoted the proliferation and migration of EC cells. Furthermore, increased CD155 expression was associated with poor prognosis in patients with EC. CD155 regulated the Hippo-Yap pathway, influencing cell proliferation and migration. Therefore, CD155 is essential for the proliferation, migration, and radioresistance of EC. CD155 inhibition may be a viable strategy for improving radiation treatment efficacy in individuals with EC.

FRK inhibits glioblastoma progression via phosphorylating YAP and inducing its ubiquitylation and degradation by Siah1

BACKGROUND

We previously report that yes-associated protein (YAP), the core downstream effector of Hippo pathway, promotes the malignant progression of glioblastoma (GBM). However, although classical regulatory mechanisms of YAP are well explored, how YAP is modulated by the Hippo-independent manner remains poorly understood. Meanwhile, the nonreceptor tyrosine kinase Fyn-related kinase (FRK), which exhibits low expression and possesses tumor suppressor effects in GBM, is reported to be involved in regulation of protein phosphorylation. Here, we examined whether FRK could impede tumor progression by modulating YAP activities.

METHODS

Human GBM cells and intracranial GBM model were used to assess the effects of FRK and YAP on the malignant biological behaviors of GBM. Immunoblotting and immunohistochemistry were used to detect the expression of core proteins in GBM tissues. Co-immunoprecipitation, proximity ligation assay, luciferase assay and ubiquitination assay were utilized to determine the protein-protein interactions and related molecular mechanisms.

RESULTS

The expression levels of FRK and YAP were inversely correlated with each other in glioma tissues. In addition, FRK promoted the ubiquitination and degradation of YAP, leading to tumor suppression in vitro and in vivo. Mechanistically, FRK interacted with and phosphorylated YAP on Tyr391/407/444, which recruited the classical E3 ubiquitin ligase Siah1 to catalyze ubiquitination and eventually degradation of YAP. Siah1 is required for YAP destabilization initiated by FRK.

CONCLUSIONS

We identify a novel mechanism by which FRK orchestrates tumor-suppression effect through phosphorylating YAP and inducing its ubiquitination by Siah1. FRK-Siah1-YAP signaling axis may serve as a potential therapeutic target for GBM treatment.

YAP1/TAZ activity maintains vascular integrity and organismal survival

Radiation therapy is one of the major treatment modalities for patients with cancers. However, ionizing radiation (IR) damages not only cancer cells but also the surrounding vascular endothelial cells (ECs). Hippo pathway effector genes Yap1 and Taz are the two transcriptional coactivators that have crucial roles in tissue homeostasis and vascular integrity in various organs. However, their function in adult ECs at the steady state and after IR is poorly understood. Here, we report sex- and context-dependent roles of endothelial YAP1/TAZ in maintaining vascular integrity and organismal survival. EC-specific Yap1/Taz deletion compromised systemic vascular integrity, resulting in lethal circulation failure preferentially in male mice. Furthermore, EC-specific Yap1/Taz deletion induced acute lethality upon sublethal IR that was closely associated with exacerbated systemic vascular dysfunction and circulation failure. Consistent with these findings, RNA-seq analysis revealed downregulation of tight junction genes in Yap1/Taz-deleted ECs. Collectively, our findings highlight the importance of endothelial YAP1/TAZ for maintaining adult vascular function, which may provide clinical implications for preventing organ injury after radiation therapy.

Functions of Yes-association protein (YAP) in cancer progression and anticancer therapy resistance

The Hippo pathway, a highly conserved kinase cascade, regulates cell proliferation, apoptosis, organ size, and tissue homeostasis. Dysregulation of this pathway reportedly plays an important role in the progression of various human cancers. Yes-association protein (YAP), the Hippo pathway’s core effector, is considered a marker for cancer therapy and patient prognosis. In addition, studies have indicated that YAP is involved in promoting anticancer drug resistance. This review summarizes current knowledge on YAP’s role in cancer progression, anticancer drug resistance, and advances in the development of YAP-targeting drugs. A thorough understanding of the complex interactions among molecular, cellular, and environmental factors concerning YAP function in cancer progression may provide new insight into the underlying mechanism of anticancer drug resistance. It might lead to improved prognosis through novel combined therapies.

Hippo Pathway in Regulating Drug Resistance of Glioblastoma

Glioblastoma (GBM) represents the most common and malignant tumor of the Central Nervous System (CNS), affecting both children and adults. GBM is one of the deadliest tumor types and it shows a strong multidrug resistance (MDR) and an immunosuppressive microenvironment which remain a great challenge to therapy. Due to the high recurrence of GBM after treatment, the understanding of the chemoresistance phenomenon and how to stimulate the antitumor immune response in this pathology is crucial. The deregulation of the Hippo pathway is involved in tumor genesis, chemoresistance and immunosuppressive nature of GBM. This pathway is an evolutionarily conserved signaling pathway with a kinase cascade core, which controls the translocation of YAP (Yes-Associated Protein)/TAZ (Transcriptional Co-activator with PDZ-binding Motif) into the nucleus, leading to regulation of organ size and growth. With this review, we want to highlight how chemoresistance and tumor immunosuppression work in GBM and how the Hippo pathway has a key role in them. We linger on the role of the Hippo pathway evaluating the effect of its de-regulation among different human cancers. Moreover, we consider how different pathways are cross-linked with the Hippo signaling in GBM genesis and the hypothetical mechanisms responsible for the Hippo pathway activation in GBM. Furthermore, we describe various drugs targeting the Hippo pathway. In conclusion, all the evidence described largely support a strong involvement of the Hippo pathway in gliomas progression, in the activation of chemoresistance mechanisms and in the development of an immunosuppressive microenvironment. Therefore, this pathway is a promising target for the treatment of high grade gliomas and in particular of GBM.

Anti-invasive efficacy and survival benefit of the YAP-TEAD inhibitor Verteporfin in preclinical glioblastoma models

BACKGROUND

Glioblastoma (GBM) remains a largely incurable disease as current therapy fails to target the invasive nature of GBM growth in disease progression and recurrence. Here we use the FDA-approved drug and small molecule Hippo inhibitor Verteporfin to target YAP-TEAD activity, known to mediate convergent aspects of tumor invasion/metastasis, and assess the drug's efficacy and survival benefit in GBM models.

METHODS

Up to eight low-passage patient-derived GBM cell lines with distinct genomic drivers, including three primary/recurrent pairs, were treated with Verteporfin or vehicle to assess in-vitro effects on proliferation, migration, YAP-TEAD activity, and transcriptomics. Patient-derived orthotopic xenograft models (PDX) were used to assess Verteporfin's brain penetrance and effects on tumor burden and survival.

RESULTS

Verteporfin treatment disturbed YAP/TAZ-TEAD activity; disrupted transcriptome signatures related to invasion, epithelial-to-mesenchymal, and proneural-to-mesenchymal transition, phenocopying TEAD1-knockout effects; and impaired tumor migration/invasion dynamics across primary and recurrent GBM lines. In an aggressive orthotopic PDX GBM model, short-term Verteporfin treatment consistently diminished core and infiltrative tumor burden, which was associated with decreased tumor expression of Ki67, nuclear YAP, TEAD1, and TEAD-associated targets EGFR, CDH2 and ITGB1. Finally, long-term Verteporfin treatment appeared non-toxic and conferred survival benefit compared to vehicle in two PDX models: as monotherapy in primary (de-novo) GBM and in combination with Temozolomide chemoradiation in recurrent GBM, where VP treatment associated with increased MGMT methylation.

CONCLUSIONS

We demonstrate combined anti-invasive and anti-proliferative efficacy for Verteporfin with survival benefit in preclinical GBM models, indicating potential therapeutic value of this already FDA-approved drug if repurposed for glioblastoma patients.

Cell survival after DNA damage in the comet assay

The comet assay is widely used in basic research, genotoxicity testing, and human biomonitoring. However, interpretation of the comet assay data might benefit from a better understanding of the future fate of a cell with DNA damage. DNA damage is in principle repairable, or if extensive, can lead to cell death. Here, we have correlated the maximally induced DNA damage with three test substances in TK6 cells with the survival of the cells. For this, we selected hydrogen peroxide (H₂O₂) as an oxidizing agent, methyl methanesulfonate (MMS) as an alkylating agent and etoposide as a topoisomerase II inhibitor. We measured cell viability, cell proliferation, apoptosis, and micronucleus frequency on the following day, in the same cell culture, which had been analyzed in the comet assay. After treatment, a concentration dependent increase in DNA damage and in the percentage of non-vital and apoptotic cells was found for each substance. Values greater than 20-30% DNA in tail caused the death of more than 50% of the cells, with etoposide causing slightly more cell death than H₂O₂ or MMS. Despite that, cells seemed to repair of at least some DNA damage within few hours after substance removal. Overall, the reduction of DNA damage over time is due to both DNA repair and death of heavily damaged cells. We recommend that in experiments with induction of DNA damage of more than 20% DNA in tail, survival data for the cells are provided.