Inhibition of matrix metalloproteinase-2 enhances radiosensitivity by abrogating radiation-induced FoxM1-mediated G2/M arrest in A549 lung cancer cells

Abnormal expression of FOXM1 in carcinogenesis of renal cell carcinoma: From experimental findings to clinical applications

Renal cell carcinoma (RCC) is a prevalent malignancy within the genitourinary system. At present, patients with high-grade or advanced RCC continue to have a bleak prognosis. Mounting research have emphasized the significant involvement of Forkhead box M1 (FOXM1) in RCC development and progression. Therefore, it is imperative to consolidate the existing evidence regarding the contributions of FOXM1 to RCC tumorigenesis through a comprehensive review. This study elucidated the essential functions of FOXM1 in promoting RCC growth, invasion, and metastasis by regulating cell cycle progression, DNA repair, angiogenesis, and epithelial-mesenchymal transition (EMT). Also, FOXM1 might serve as a novel diagnostic and prognostic biomarker as well as a therapeutic target for RCC. Clinical findings demonstrated that the expression of FOXM1 was markedly upregulated in RCC samples, while a high level of FOXM1 was found to be associated with a poor overall survival rate of RCC. Furthermore, it is worth noting that FOXM1 may have a significant impact on the resistance of renal cell carcinoma (RCC) to radiotherapy. This observation suggests that inhibiting FOXM1 could be a promising strategy to impede the progression of RCC and enhance its sensitivity to radiotherapy. The present review highlighted the pivotal role of FOXM1 in RCC development. FOXM1 has the capacity to emerge as not only a valuable diagnostic and prognostic tool but also a viable therapeutic option for unresectable RCC.

Stromal Reprogramming by FAK Inhibition Overcomes Radiation Resistance to Allow for Immune Priming and Response to Checkpoint Blockade

The effects of radiotherapy (RT) on tumor immunity in pancreatic ductal adenocarcinoma (PDAC) are not well understood. To better understand if RT can prime antigen-specific T-cell responses, we analyzed human PDAC tissues and mouse models. In both settings, there was little evidence of RT-induced T-cell priming. Using in vitro systems, we found that tumor-stromal components, including fibroblasts and collagen, cooperate to blunt RT efficacy and impair RT-induced interferon signaling. Focal adhesion kinase (FAK) inhibition rescued RT efficacy in vitro and in vivo, leading to tumor regression, T-cell priming, and enhanced long-term survival in PDAC mouse models. Based on these data, we initiated a clinical trial of defactinib in combination with stereotactic body RT in patients with PDAC (NCT04331041). Analysis of PDAC tissues from these patients showed stromal reprogramming mirroring our findings in genetically engineered mouse models. Finally, the addition of checkpoint immunotherapy to RT and FAK inhibition in animal models led to complete tumor regression and long-term survival.

SIGNIFICANCE

Checkpoint immunotherapeutics have not been effective in PDAC, even when combined with RT. One possible explanation is that RT fails to prime T-cell responses in PDAC. Here, we show that FAK inhibition allows RT to prime tumor immunity and unlock responsiveness to checkpoint immunotherapy. This article is highlighted in the In This Issue feature, p. 2711.

Recombinantly expressed MeICT, a new toxin from Mesobuthus eupeus scorpion, inhibits glioma cell proliferation and downregulates Annexin A2 and FOXM1 genes

Gliomas are highly invasive and lethal malignancy that do not respond to current therapeutic approaches. Novel therapeutic agents are required to target molecular mechanisms involved in glioma progression. MeICT is a new short-chain toxin isolated from Mesobuthus eupeus scorpion venom. This toxin contained 34 amino acid residues and belongs to chloride channels toxins. In this study, the coding sequence of MeICT was cloned into the pET32Rh vector and a high yield of soluble recombinant MeICT was expressed and purified. Recombinant MeICT-His significantly inhibited the proliferation and migration of glioma cells at low concentration. In vivo studies showed that MeICT was not toxic when administrated to mice at high doses. We also determined the effect of MeICT on the mRNA expression of MMP-2, Annexin A2 and FOXM-2 that are key molecules in the progression and invasion of glioma. Expression of Annexin A2 and FOXM1 mRNA was significantly down-regulated following treatment with MeICT. However, no significant decrease in the expression of MMP-2 gene was identified. In this study a short toxin with four disulfide bonds was successfully produced and its anti-cancer effects was detected. Our findings suggest that recombinant MeICT can be considered as a new potent agent for glioma targeting.

MT1-MMP-dependent ECM processing regulates laminB1 stability and mediates replication fork restart

Radiotherapy remains a mainstay of treatment for a majority of cancer patients. We have previously shown that the membrane bound matrix metalloproteinase MT1-MMP confers radio- and chemotherapy resistance to breast cancer via processing of the ECM and activation of integrinβ1/FAK signaling. Here, we further discovered that the nuclear envelope protein laminB1 is a potential target of integrinβ1/FAK. FAK interacts with laminB1 contributing to its stability. Stable laminB1 is found at replication forks (RFs) where it is likely to allow the proper positioning of RF protection factors, thus preventing RF degradation. Indeed, restoration of laminB1 expression rescues replication fork stalling and collapse that occurs upon MT1-MMP inhibition, and reduces DNA damage in breast cancer cells. Together, these data highlight a novel mechanism of laminB1 stability and replication fork restart via MT1-MMP dependent extracelluar matrix remodeling.

An Integrated Analysis of the Response of Colorectal Adenocarcinoma Caco-2 Cells to X-Ray Exposure

Colorectal cancer is among the three top cancer types for incidence and the second in terms of mortality, usually managed with surgery, chemotherapy and radiotherapy. In particular, radiotherapeutic concepts are crucial for the management of advanced rectal cancer, but patients’ survival remains poor, despite advances in treatment modalities. The use of well-characterized in vitro cell culture systems offers an important preclinical strategy to study mechanisms at the basis of cell response to therapeutic agents, including ionizing radiation, possibly leading to a better understanding of the in vivo response to the treatment. In this context, we present an integrated analysis of results obtained in an extensive measurement campaign of radiation effects on Caco-2 cells, derived from human colorectal adenocarcinoma. Cells were exposed to X-rays with doses up to 10 Gy from a radiotherapy accelerator. We measured a variety of endpoints at different post-irradiation times: clonogenic survival after ~ 2 weeks; cell cycle distribution, cell death, frequency of micronucleated cells and atypical mitoses, activation of matrix metalloproteases (MMPs) and of different proteins involved in DNA damage response and cell cycle regulation at earlier time points, up to 48 h post-exposure. Combined techniques of flow cytometry, immunofluorescence microscopy, gelatin zymography and western blotting were used. For selected endpoints, we also addressed the impact of the irradiation protocol, comparing results obtained when cells are plated before irradiation or first-irradiated and then re-plated. Caco-2 resistance to radiation, previously assessed up to 72 h post exposure in terms of cell viability, does not translate into a high clonogenic survival. Survival is not affected by the irradiation protocol, while endpoints measured on a shorter time frame are. Radiation mainly induces a G₂-phase arrest, confirmed by associated molecular markers. The activation of death pathways is dose- and time-dependent, and correlates with a dose-dependent inhibition of MMPs. Genomic aberrations are also found to be dose-dependent. The phosphorylated forms of several proteins involved in cell cycle regulation increase following exposure; the key regulator FoxM1 appears to be downregulated, also leading to inhibition of MMP-2. A unified molecular model of the chain of events initiated by radiation is proposed to interpret all experimental results.

Combined Radiochemotherapy: Metalloproteinases Revisited

Besides cytotoxic DNA damage irradiation of tumor cells triggers multiple intra- and intercellular signaling processes, that are part of a multilayered, treatment-induced stress response at the unicellular and tumor pathophysiological level. These processes are intertwined with intrinsic and acquired resistance mechanisms to the toxic effects of ionizing radiation and thereby co-determine the tumor response to radiotherapy. Proteolysis of structural elements and bioactive signaling moieties represents a major class of posttranslational modifications regulating intra- and intercellular communication. Plasma membrane-located and secreted metalloproteinases comprise a family of metal-, usually zinc-, dependent endopeptidases and sheddases with a broad variety of substrates including components of the extracellular matrix, cyto- and chemokines, growth and pro-angiogenic factors. Thereby, metalloproteinases play an important role in matrix remodeling and auto- and paracrine intercellular communication regulating tumor growth, angiogenesis, immune cell infiltration, tumor cell dissemination, and subsequently the response to cancer treatment. While metalloproteinases have long been identified as promising target structures for anti-cancer agents, previous pharmaceutical approaches mostly failed due to unwanted side effects related to the structural similarities among the multiple family members. Nevertheless, targeting of metalloproteinases still represents an interesting rationale alone and in combination with other treatment modalities. Here, we will give an overview on the role of metalloproteinases in the irradiated tumor microenvironment and discuss the therapeutic potential of using more specific metalloproteinase inhibitors in combination with radiotherapy.

Tumor Microenvironment as a Regulator of Radiation Therapy: New Insights into Stromal-Mediated Radioresistance

Simple Summary

Cancer is multifaceted and consists of more than just a collection of mutated cells. These cancerous cells reside along with other non-mutated cells in an extracellular matrix which together make up the tumor microenvironment or tumor stroma. The composition of the tumor microenvironment plays an integral role in cancer initiation, progression, and response to treatments. In this review, we discuss how the tumor microenvironment regulates the response and resistance to radiation therapy and what targeted agents have been used to combat stromal-mediated radiation resistance.

Abstract

A tumor is a complex “organ” composed of malignant cancer cells harboring genetic aberrations surrounded by a stroma comprised of non-malignant cells and an extracellular matrix. Considerable evidence has demonstrated that components of the genetically “normal” tumor stroma contribute to tumor progression and resistance to a wide array of treatment modalities, including radiotherapy. Cancer-associated fibroblasts can promote radioresistance through their secreted factors, contact-mediated signaling, downstream pro-survival signaling pathways, immunomodulatory effects, and cancer stem cell-generating role. The extracellular matrix can govern radiation responsiveness by influencing oxygen availability and controlling the stability and bioavailability of growth factors and cytokines. Immune status regarding the presence of pro- and anti-tumor immune cells can regulate how tumors respond to radiation therapy. Furthermore, stromal cells including endothelial cells and adipocytes can modulate radiosensitivity through their roles in angiogenesis and vasculogenesis, and their secreted adipokines, respectively. Thus, to successfully eradicate cancers, it is important to consider how tumor stroma components interact with and regulate the response to radiation. Detailed knowledge of these interactions will help build a preclinical rationale to support the use of stromal-targeting agents in combination with radiotherapy to increase radiosensitivity.

Vascular and extracellular matrix remodeling by physical approaches to improve drug delivery at the tumor site

INTRODUCTION

Modern comprehensive studies of tumor microenvironment changes allowed scientists to develop new and more efficient strategies that will improve anticancer drug delivery on site. The tumor microenvironment, especially the dense extracellular matrix, has a recognized capability to hamper the penetration of conventional drugs. Development and co-applications of strategies aiming at remodeling the tumor microenvironment are highly demanded to improve drug delivery at the tumor site in a therapeutic prospect.

AREAS COVERED

Increasing indications suggest that classical physical approaches such as exposure to ionizing radiations, hyperthermia or light irradiation, and emerging ones as sonoporation, electric field or cold plasma technology can be applied as standalone or associated strategies to remodel the tumor microenvironment. The impacts on vasculature and extracellular matrix remodeling of these physical approaches will be discussed with the goal to improve nanotherapeutics delivery at the tumor site.

EXPERT OPINION

Physical approaches to modulate vascular properties and remodel the extracellular matrix are of particular interest to locally control and improve drug delivery and thus increase its therapeutic index. They are particularly powerful as adjuvant to nanomedicine delivery; the development of these technologies could have extremely widespread implications for cancer treatment.[Figure: see text].

Redirecting extracellular proteases to molecularly guide radiosensitizing drugs to tumors

Patients with advanced cancers are treated with combined radiotherapy and chemotherapy, however curability is poor and treatment side effects severe. Drugs sensitizing tumors to radiotherapy have been developed to improve cell kill, but tumor specificity remains challenging. To achieve tumor selectivity of small molecule radiosensitizers, we tested as a strategy active tumor targeting using peptide-based drug conjugates. We attached an inhibitor of the DNA damage response to antibody or cell penetrating peptides. Antibody drug conjugates honed in on tumor overexpressed cell surface receptors with high specificity but lacked efficacy when conjugated to the DNA damage checkpoint kinase inhibitor AZD7762. As an alternative approach, we synthesized activatable cell penetrating peptide scaffolds that accumulated within tumors based on matrix metalloproteinase cleavage. While matrix metalloproteinases are integral to tumor progression, they have proven therapeutically elusive. We harnessed these pro-tumorigenic extracellular proteases to spatially guide radiosensitizer drug delivery using cleavable activatable cell penetrating peptides. Here, we tested the potential of these two drug delivery platforms targeting distinct tumor compartments in combination with radiotherapy and demonstrate the advantages of protease triggered cell penetrating peptide scaffolds over antibody drug conjugates to deliver small molecule amine radiosensitizers.

Silencing of LINC00461 enhances radiosensitivity of lung adenocarcinoma cells by down-regulating HOXA10 via microRNA-195

Lung adenocarcinoma is recognized as one of the most recurrent tumours in adults. Long non‐coding RNAs (lncRNAs) are non–protein‐coding transcripts and have been demonstrated to regulate biological functions during tumorigenesis. Our study aims to investigate the underlying molecular mechanisms of LINC00461/microRNA‐195 (miR‐195)/HOXA10 responsible for its involvement in lung adenocarcinoma. We firstly selected differentially expressed lncRNAs and genes by the Cancer Genome Atlas (TCGA) database and Gene Expression Omnibus (GEO). The functional role of LINC00461 in lung adenocarcinoma was then determined using ectopic expression, knockdown and reporter assay experiments. Besides, we detected the expression profiles of LINC00461, miR‐195, HOXA10 and apoptosis‐ and invasion‐related genes. Cell proliferation, migration and invasion were evaluated. In vivo tumour formation ability was analysed. Overexpressed LINC00461 and HOXA10 but down‐regulated miR‐195 were observed in primary and metastatic lung adenocarcinoma. LINC00461 negatively regulated miR‐195, while miR‐195 negatively regulated HOXA10. Forced LINC00461 expression decreased expression of miR‐195 and Bax, increased expression of HOXA10, MMP‐2, MMP‐9 and Bcl‐2, promoted cell proliferation, migration and invasion as well as tumour formation, and enhanced radiosensitivity of lung adenocarcinoma cells. However, these effects were reversed by lentivirus‐mediated miR‐195–forced expression, thereby suggesting that miR‐195 could antagonize the harmful effect of LINC00461 on lung adenocarcinoma cells. Collectively, the present study provides evidence supporting the inhibitory effect of LINC00461 silencing on lung adenocarcinoma, which suppresses lung adenocarcinoma cell migration, invasion and radiosensitivity via HOXA10 by binding to miR‐195, which provides a promising basis for the targeted intervention treatment for human lung adenocarcinoma.

ShRNA-mediated matrix metalloproteinase-2 gene silencing protects normal cells and sensitizes cancer cells against ionizing-radiation induced damage

INTRODUCTION

Ionizing radiation (IR) affects healthy tissues during the treatment of cancer radiation therapy and other nuclear and radiological accidents. Some natural compounds showed nonspecific radioprotective activity with severe side effects. The present study is aimed to develop potent and specific radioprotective short hairpin RNA (shRNA), which selectively protects normal cells from IR by specifically targeting matrix metalloproteinases (MMP-2).

RESULTS

IR reduced the viability of human normal dermal fibroblasts (HDFs) in a dose-response manner. It enhanced the expression of MMP-2 at 10 Gy. Plasmid MMP-2shRNA (pMMP-2) reduced the IR (10 Gy) induced cytotoxicity analyzed by lactate dehydrogenase (LDH) assay, normalized IR induced cellular and morphological changes with enhanced the clonogenicity in 48 hours at 2 µg/mL. It reduced the ROS generation, released HDFs from G₂ /M arrest and rescued from apoptosis analyzed by DCFDA dye, cell cycle analysis by PI stain and annexin V assay, respectively. pMMP-2 also modulates the expression of EGFR and reduced IR induced expression of DNA damage response protein, ATM and increased the expression of repair proteins, KU70/KU80, and RAD51. In addition, decreased the expression of cell cycle regulatory proteins cyclin-dependent kinases (CDK1) and Cyclin B as well as proapoptotic proteins BAX, caspase-3, and Cytochrome-C and increased the expression of survival protein, Bcl-2. In contrary pMMP-2 decreased the LDH activity, survival fraction and blocked G₂ /M phase of cell cycle and increased apoptosis in MCF-7 cells. In addition, decreased the expression of EGFR, proapoptotic BAX and DNA repair proteins ATM, KU70/80 and RAD51, increased expression of cyclinB as well as CDK1.

CONCLUSION

Results conclude that pMMP-2 protected HDFs from IR and sensitized the MCF-7 cells. Therefore, pMMP-2 can be employed for better treatment of radiation accidents and during the treatment of radiotherapy.

Knockdown of PKM2 enhances radiosensitivity of cervical cancer cells

Background

Pyruvate kinase isozyme type M2 (PKM2) catalyzes the final step in glycolysis and has been found to be up-regulated in multiple human malignancies. However, whether PKM2 regulates the radiosensitivity of human cervical cancer (CC) remains unknown.

Methods

The expression of PKM2 in 94 patients with CC in the complete response (CR) and noncomplete response (nCR) groups, was evaluated by immunohistochemistry. The effect of PKM2 inhibition on radiosensitivity, the cell cycle, DNA damage, and apoptosis was evaluated by immunofluorescence analysis, colony formation assay, flow cytometry analysis and Western blotting.

Results

PKM2 expression was more highly expressed in the nCR group than that in CR group and PKM2 expression was enhanced in CC cells after ionizing radiation (IR). In addition, knockdown of PKM2 combined with IR significantly reduced cell growth, promoted apoptosis, and enhanced radiosensitivity. Additionally, knockdown of PKM2 with IR resulted in increased phosphorylation of DNA repair checkpoint proteins (ATM) and phosphorylated-H2AX. Moreover, knockdown of PKM2 combined with IR significantly increased the expression of cleaved caspase 3 and caspase 9, whereas Bcl2 expression was suppressed. Furthermore, knockdown of PKM2 combined with IR markedly reduced the expression of several cancer stem cell biomarkers in vitro, including NANOG, OCT4, SOX2, and Bmi1.

Conclusions

The results of our study suggests that PKM2 might be involved in mediating CC radiosensitivity and is identified as a potentially important target to enhance radiosensitivity in patients with CC.

The multifaceted roles of FOXM1 in pulmonary disease

Forkhead box M1 (FOXM1), a transcriptional regulator of G1/S and G2/M transition and M phase progression in the cell cycle, plays a principal role in many physiological and pathological processes. A growing number of studies have focused on the relationship between abnormal FOXM1 expression and pulmonary diseases, such as lung cancer, chronic obstructive pulmonary disease (COPD), asthma, acute lung injury (ALI), pulmonary fibrosis, and pulmonary arterial hypertension (PAH). These studies indicate that the FOXM1 regulatory network is a major predictor of poor outcomes, especially in lung cancer, and provide novel insight into various pulmonary diseases. For the first time, this review summarizes the mechanistic relationship between FOXM1 dysregulation and pulmonary diseases, the benefits of targeting abnormal FOXM1 expression, and the questions that remain to be addressed in the future.

FAST1 promotes the migration and invasion of colorectal cancer cells

BACKGROUND

The forkhead activin signal transducer 1 (FAST1) is involved in several oncogenic signaling pathways and its abnormal expression has been discovered in some cancers. Yet the role of FAST1 in colorectal cancer (CRC) remains largely unclear. Therefore, the goal of this study was to explore the function of FAST1 in CRC.

METHODS

In this study, we analyzed FAST1 expression and its relationship with clinicopathological parameters and prognostic significance in CRC via immunohistochemistry analysis. The effects and mechanisms of FAST1 on cell proliferation, migration and invasion were explored in vitro and in vivo.

RESULTS

We found that increased FAST1 as an independent prognostic factor was positively associated with TNM stage and pathological grade in CRC. FAST1 overexpression promoted the CRC cell proliferation, migration and invasion in vivo. Furthermore, mechanistic studies implicated that FAST1 enhanced the pulmonary metastasis of CRC cells through down-regulating E-cadherin levels.

CONCLUSIONS

In summary, FAST1 was significantly associated with CRC progression and could serve as an independent prognostic factor. FAST1 may be potential therapeutic target for CRC patients.

Vicenin-2: a potential radiosensitizer of non-small cell lung cancer cells

Non-small cell lung cancer (NSCLC) is a major form of cancer and is resistant to chemo- and radio-therapy. Vicenin-2 (VCN-2) is a flavonoid obtained from Ocimum sanctum L. and it has been reported to have radioprotective and anti-cancer properties. This study was conducted to check for the radiosensitizing potential of VCN-2 in the NSCLC cell line, NCI-H23. NCI-H23 cells were exposed to VCN-2 singularly, and to X-rays with and without prior VCN-2 treatment. Cytotoxicity assay, cell proliferation assay, caspase-3 activity assay, DNA fragmentation assay and Western blotting for Rad50, MMP-2 and p21 were performed to investigate the radiosensitizing properties of VCN-2. Fibroblast survival assay was performed using HEK293T cells to check for any adverse effects of VCN-2 on normal fibroblast cell line. VCN-2 singularly and in combination with radiation reduced the surviving cancer cells, increased caspase-3 activity, increased DNA fragmentation, increased the levels of Rad50 and lowered levels of MMP-2 and p21 proteins while being non-toxic and radioprotective to the fibroblast cells. VCN-2 showed a potent radiosensitizing property while also showing a chemotherapeutic property against NSCLC cell line NCI-H23.

Radiation-Induced Transformation of Immunoregulatory Networks in the Tumor Stroma

The implementation of novel cancer immunotherapies in the form of immune checkpoint blockers represents a major advancement in the treatment of cancer, and has renewed enthusiasm for identifying new ways to induce antitumor immune responses in patients. Despite the proven efficacy of neutralizing antibodies that target immune checkpoints in some refractory cancers, many patients do not experience therapeutic benefit, possibly owing to a lack of antitumor immune recognition, or to the presence of dominant immunosuppressive mechanisms in the tumor microenvironment (TME). Recent developments in this field have revealed that local radiotherapy (RT) can transform tumors into in situ vaccines, and may help to overcome some of the barriers to tumor-specific immune rejection. RT has the potential to ignite tumor immune recognition by generating immunogenic signals and releasing neoantigens, but the multiple immunosuppressive forces in the TME continue to represent important barriers to successful tumor rejection. In this article, we review the radiation-induced changes in the stromal compartments of tumors that could have an impact on tumor immune attack. Since different RT regimens are known to mediate strikingly different effects on the multifarious elements of the tumor stroma, special emphasis is given to different RT schedules, and the time after treatment at which the effects are measured. A better understanding of TME remodeling following specific RT regimens and the window of opportunity offered by RT will enable optimization of the design of novel treatment combinations.

The Impact of Radiation on the Tumor Microenvironment: Effect of Dose and Fractionation Schedules

In addition to inducing lethal DNA damage in tumor and stromal cells, radiation can alter the interactions of tumor cells with their microenvironment. Recent technological advances in planning and delivery of external beam radiotherapy have allowed delivery of larger doses per fraction (hypofractionation) while minimizing dose to normal tissues with higher precision. The effects of radiation on the tumor microenvironment vary with dose and fractionation schedule. In this review, we summarize the effects of conventional and hypofractionated radiation regimens on the immune system and tumor stroma. We discuss how these interactions may provide therapeutic benefit in combination with targeted therapies. Understanding the differential effects of radiation dose and fractionation can have implications for choice of combination therapies.

MicroRNA-320 Enhances Radiosensitivity of Glioma Through Down-Regulation of Sirtuin Type 1 by Directly Targeting Forkhead Box Protein M1

Glioma is the most common cancer in human brain system and seriously threatens human health. miRNA-320 has been demonstrated to be closely correlated with the development of glioma. However, its effect and molecular mechanism underlying radioresistance have not been fully elucidated in glioma. Here, RT-qPCR assay was used to assess the expressions of miR-320 and forkhead box protein M1 (FoxM1) mRNA in glioma tumor tissues and cells. The effects of miR-320, FoxM1 and sirtuin type 1 (Sirt1) on radiosensitivity in glioma cells were evaluated by clone formation assay, apoptosis assay, histone H2AX phosphorylation level (γH2AX) detection and caspase 3 activity analysis, respectively. The direct interaction between miR-320 and FoxM1 was detected by luciferase assay. The protein levels of FoxM1, Sirt1 and γH2AX were measured by western blot assay. We found that miR-320 expression was down-regulated and FoxM1 expression was up-regulated in radioresistant glioma tissues and IR-treated glioma cells. miR-320 overexpression dramatically enhanced radiosensitivity, promoted apoptosis, and improved γH2AX expression and caspase 3 activity in glioma cells. Luciferase reporter assay and western blot assay further validated that miR-320 suppressed FoxM1 expression by directly targeting 3' UTR region of FoxM1. Moreover, miR-320 inhibited Sirt1 expression via targeting FoxM1 in glioma cells. Furthermore, overexpression of FoxM1 and Sirt1 strikingly attenuated miR-320-induced increase of radiosensitivity, apoptosis and γH2AX expression in glioma cells. In conclusion, miR-320 enhanced radiosensitivity of glioma cells through down-regulation of Sirt1 by directly targeting FoxM1.

miRNA-200c enhances radiosensitivity of esophageal cancer by cell cycle arrest and targeting P21

Esophageal squamous cancer is one of the most fatal malignancies and often suffer recurrence after radiotherapy. Downregulation of miRNA-200c is associated with radiotolerance. We aim to investigate the role of miRNA-200c in radiosensitivity and develop a systemic treatment strategy for esophageal squamous cancer. Overexpression of miRNA-200c by transfection was determined by RT-PCR. Radiosensitizing effect of miRNA-200c on esophageal squamous cancer cells was determined by clonogenic assay and xenograft model. Cell cycle was analyzed by flow cytometry. The levels of Cyclin B1, cyclin D1, cyclin E1, CDK2, CDK4, Cdc2 and P21 protein expressions were detected by western blotting. The results of our study revealed that miRNA-200c enhanced the radiosensitivity significantly in esophageal squamous cancer cell line in vitro and in vivo. miRNA-200c induced G2/M and sub-G1 phase arrest and reduced S phase rate of the irradiated Eca-109 cells and downregulated expression levels of Cyclin B1, cdc2 and upregulated P21 expression level. Present results demonstrate that downregulation of miRNA-200c is associated with radiotolerance. miRNA-200c increases radiosensitivity by G2/M and sub-G1 phase arrest through modulating Cyclin B1, cdc2 and P21 expression levels.

Procyanidin-rich extract of natural cocoa powder causes ROS-mediated caspase-3 dependent apoptosis and reduction of pro-MMP-2 in epithelial ovarian carcinoma cell lines

Over the last four centuries, cocoa and chocolate have been described as having potential medicinal value. As of today, Theobroma cacao L. (Sterculiaceae) and its products are consumed worldwide. They are of great research interest because of the concentration dependent antioxidant as well as pro-oxidant properties of some of their polyphenolic constituents, specially procyanidins and flavan-3-ols such as catechin. This study was aimed at investigating the cellular and molecular changes associated with cytotoxicity, caused due pro-oxidant activity of cocoa catechins and procyanidins, in ovarian cancer cell lines. Extract of non-alkalized cocoa powder enriched with catechins and procyanidins was used to treat human epithelial ovarian cancer cell lines OAW42 and OVCAR3 at various concentrations ≤1000μg/mL. The effect of treatment on intracellular reactive oxygen species (ROS) levels was determined. Apoptotic cell death, post treatment, was evaluated microscopically and using flow cytometry by means of annexin-propidium iodide (PI) dual staining. Levels of active caspase-3 as a pro-apoptotic marker and matrix metalloproteinase 2 (MMP2) as an invasive potential marker were detected using Western blotting and gelatin zymography. Treatment with extract caused an increase in intracellular ROS levels in OAW42 and OVCAR3 cell lines. Bright field and fluorescence microscopy of treated cells revealed apoptotic morphology and DNA damage. Increase in annexin positive cell population and dose dependent upregulation of caspase-3 confirmed apoptotic cell death. pro-MMP2 was found to be downregulated in a dose dependent manner in cells treated with the extract. Treated cells also showed a reduction in MMP2 activity. Our data suggests that cocoa catechins and procyanidins are cytotoxic to epithelial ovarian cancer, inducing apoptotic morphological changes, DNA damage and caspase-3 mediated cell death. Downregulation of pro-MMP2 and reduction in active MMP2 levels imply a decrease in invasive potential of the cells. Apoptosis and MMP2 downregulation appear to be linked to the increase in intracellular ROS levels, caused due to the prooxidant effect of cocoa procyanidin extract.

The disintegrin, trimucrin, suppresses LPS-induced activation of phagocytes primarily through blockade of NF-κB and MAPK activation

In addition to antiplatelet activity, disintegrin, a small-mass RGD-containing polypeptide, has been shown to exert anti-inflammatory effects but the mechanism involved remains unclear. In this study, we report that trimucrin, a disintegrin from the venom of Trimeresurus mucrosquamatus, inhibits lipopolysaccharide (LPS)-induced stimulation of THP-1 and RAW 264.7 cells. We also investigate the underlying mechanism. Trimucrin decreased the release of proinflammatory cytokines including tumor necrosis factor α (TNFα), interleukin-6 (IL-6), nitric oxide, and reactive oxygen species (ROS), and inhibited the adhesion and migration of LPS-activated phagocytes. Trimucrin significantly blocked the expression of nuclear factor kappaB (NF-κB)-related downstream inducible enzymes such as inducible nitric oxide synthase (iNOS) and COX-2. In addition, its anti-inflammatory effect was associated with the decreased mitogen-activated protein kinase (MAPK) phosphorylation. Furthermore, trimucrin concentration dependently inhibited LPS-induced phosphorylation of focal adhesion kinase (FAK), PI3K, and Akt. Trimucrin also reversed the DNA-binding activity of NF-κB by suppressing the LPS-induced nuclear translocation of p65 and the cytosolic IκB release. Flow cytometric analyses showed that trimucrin bound to cells in a concentration-dependent manner. The anti-αVβ3 mAb also specifically decreased the binding of fluorescein isothiocyanate (FITC)-conjugated trimucrin. Binding assays demonstrated that integrin αVβ3 was the binding site for trimucrin on THP-1 and RAW 264.7 cells. In conclusion, we showed that trimucrin decreases the inflammatory reaction through the attenuation of iNOS expression and nitric oxide (NO) production by blocking MAP kinase and the NF-κB activation in LPS-stimulated THP-1 and RAW 264.7 cells.

Impacts of Ionizing Radiation on the Different Compartments of the Tumor Microenvironment

Radiotherapy (RT) is one of the most important modalities for cancer treatment. For many years, the impact of RT on cancer cells has been extensively studied. Recently, the tumor microenvironment (TME) emerged as one of the key factors in therapy resistance. RT is known to influence and modify diverse components of the TME. Hence, we intent to review data from the literature on the impact of low and high single dose, as well as fractionated RT on host cells (endothelial cells, fibroblasts, immune and inflammatory cells) and the extracellular matrix. Optimizing the schedule of RT (i.e., dose per fraction) and other treatment modalities is a current challenge. A better understanding of the cascade of events and TME remodeling following RT would be helpful to design optimal treatment combination.

In vivo optical imaging of MMP2 immuno protein antibody: tumor uptake is associated with MMP2 activity

Matrix metalloproteinase-2 (MMP2) is important in tumorigenesis, angiogenesis and tumor invasion. In this study, we investigated if the Cy5-tagged small immuno protein targeting the catalytic domain of human MMP2 (aMMP2-SIP) detects MMP2 in tumors non-invasively. For this purpose, we generated MMP2 expressing (empty vector EV) and knock-down (KD) HT1080, U373 and U87 cells, which were injected subcutaneously in the lateral flank of NMRI-nu mice. Optical imaging (Optix MX2) performed at 0.5, 2, 4, 8, 24 and 48 hour post injection (h.p.i.) of Cy5 tagged aMMP2-SIP, indicated significantly lower tumor to background ratios at both 24 (P = 0.0090) and 48 h.p.i. (P < 0.0001) for the U87 MMP2-KD compared to control tumors. No differences were found for HT1080 and U373 models. U87 MMP2-KD tumors had significantly lower MMP2 activity (P < 0.0001) than EV tumors as determined by gelatin zymography in tumor sections and lysates, while no differences were observed between EV and MMP2-KD in HT1080 and U373. In line with these data, only U87 MMP2-KD tumors had a reduced tumor growth compared to control tumors (P = 0.0053). aMMP2-SIP uptake correlates with MMP2 activity and might therefore be a potential non-invasive imaging biomarker for the evaluation of MMP2 activity in tumors.

Gene expression changes in residual advanced cervical cancer after radiotherapy: indicators of poor prognosis and radioresistance?

Background

Different sensitivity of advanced cervical cancer to irradiation can decrease effectiveness of radiotherapy in some cases. We attempted to identify the differentially expressed genes in residual cervical cancer after radiotherapy that might be associated with poor prognosis and radioresistance.

Material/Methods

Differential genes expression was identified by an oligonucleotide microarray in cervical cancer tissues before radiation and after a 50-Gy dose of radiation. The microarray results were validated by quantitative real-time PCR. CXCL12 was validated by immunohistochemistry in paraffin-embedded cervical cancer tissues before radiotherapy. The relationship between the differentiated gene and prognosis was validated by survival analysis.

Results

Hierarchic cluster analysis identified 238 differentiated genes that exhibited ≥3.0-fold change and p<0.05. We found 111 genes that were in persistent up-regulation and 127 in persistent down-regulation after a 50-Gy dose of radiation when compared with the control group. These genes were involved in processes such as cell growth and death, cell-apoptosis, cell cycle regulation, cell signaling, DNA synthesis and repair, and cell adhesion. High differential expression of CXCL12, CD74, FGF7, COL14A1, PRC1, and RAD54L genes was validated by quantitative PCR before and after radiotherapy. Survival analysis results showed that the high expression of CXCL12 was closely related to poor prognosis.

Conclusions

The higher expression of CXCL12 might be informative regarding poor prognosis in patients undergoing radical radiotherapy. The differentially expressed genes identified in our study might provide a new method for diagnosis and treatment of radioresistance in cervical cancer.

FoxM1: a novel tumor biomarker of lung cancer

FoxM1 is a member of the Forkhead box (Fox) family of transcription factors, which is expressed in actively dividing cells and is critical for cell cycle progression. Increased expression of FoxM1 was found in many tumors including non-small cell lung cancer (NSCLC). A more recent study showed FoxM1 is associated with poor prognosis of NSCLC patients through promoting tumor metastasis; elucidated FoxM1 could exert a direct effect on the prognosis of NSCLCs patients. In this review, we summarize the role FoxM1 in lung cancer in the hope of providing insights into the utility of FoxM1 as a novel biomarker of lung cancer.

Downregulation of the expression of B‑cell lymphoma-extra large by RNA interference induces apoptosis and enhances the radiosensitivity of non‑small cell lung cancer cells

B-cell lymphoma-extra large (Bcl-xL), an important member of anti-apoptotic Bcl-2 family, is involved in tumor progression and development. The overexpression of Bcl-xL is associated with radioresistance of human malignancies. The present study aimed to investigate the inhibitory effect of small interfering RNA (siRNA) on the expression of Bcl-xL in the A549 non-small lung cancer (NSCLC) cell line, and its role in inducing the apoptosis and increasing the radiosensitivity of A549 cells. An siRNA expression vector, pSilencer4-CMVneo-short hairpin (sh)RNA, was constructed and stably transfected into A549 cells. The effects of Bcl-xL-shRNA on cell proliferation, apoptosis and the protein expression levels of associated proteins were assessed in vitro in the A549 cells. The radiosensitivity of the A549 cells was evaluated using a clonogenic cell survival assay. The results demonstrated that the sequence-specific siRNA targeting Bcl-xL efficiently and specifically downregulated the mRNA and protein expression levels of Bcl-xL. The RNA interference-mediated downregulation in the expression of Bcl-xL inhibited cell proliferation, induced apoptosis and reduced the radioresistance of the NSCLC cells. These findings suggested that Bcl-xL may be a promising therapeutic approach for the treatment of NSCLC.

The miR-15 family enhances the radiosensitivity of breast cancer cells by targeting G2 checkpoints

Enhancing radiosensitivity is an important area of investigation for improving breast cancer therapy outcomes. The aim of this study was to assess the role of the miR-15 family in the radiosensitivity of breast cancer cells. MicroRNAs (miRNAs) encoded by the miR-15 cluster are known to induce G1 arrest and apoptosis by targeting G1 checkpoints and the anti-apoptotic B cell lymphoma 2 (BCL-2) gene. However, the effect of the miR-15 family on G2/M arrest and radiosensitivity remains poorly understood. In the current study, cells transfected with miR-15a/15b/16 mimic or inhibitor were irradiated and examined by: clonogenic assays, phosphorylated H2AX assay, flow cytometry, 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), real-time PCR and Western blot. Real-time PCR was also used to monitor time-dependent changes of miR-15a/15b/16 expression after irradiation. A putative target site for miR-15a/15b/16 within the Chk1 and Wee1 3' UTRs was confirmed using luciferase reporter assays. Additionally, siRNA was used to validate the effect of Chk1 and Wee1 on radiosensitivity in breast cancer cells. In our study, we investigated the effects of radiation on the miR-15 family and found a time-dependent change in the expression of miR-15a/15b/16 in breast cancer cells postirradiation, as well as an increase in miR-15 family-mediated sensitization of breast cancer cells to radiation. The increase in radiosensitivity induced by the miR-15 family was associated with persistent unrepaired DNA damage, abrogation of radiation-induced G2 arrest and suppressed cell proliferation, and appear to involve both the checkpoint kinase 1 (Chk1) and Wee1. In addition, we found that inhibition of the miR-15 family could not induce cell resistance to radiation. These findings suggest that the expression of the miR-15 family contributes to increased radiosensitivity of breast cancer cells by influencing G2/M checkpoint proteins.

Increased FOXM1 expression can stimulate DNA repair in normal hepatocytes in vivo but also increases nuclear foci associated with senescence

OBJECTIVES

FOXM1 is a transcription factor that has been shown to promote cell proliferation in many tissues during early development and high cell turnover tissues in adults. In a number of tumour cell lines, enrichment of FOXM1 has been shown to reduce the DNA damage response (DDR) and induction of senescence by a range of DNA-damaging agents, suggesting a role for the protein in DNA repair. Endogenous FOXM1 is expressed at detectable levels in hepatocytes of mice up to 2 weeks of age, but not in older mice. The aim of this investigation has been to better understand the role of the protein in DDR in normal cells in vivo.

MATERIALS AND METHODS

Mice with artificially prolonged elevated FOXM1 expression in hepatocytes, were exposed to alkylating diethylnitrosamine.

RESULTS

FOXM1-enriched mice had dampened DDR after treatment with this alkylating agent, which was consistent with observed increase in expression of genes involved in DNA repair. Paradoxically, mice with FOXM1 expression, within weeks after exposure to the DNA-damaging agent, had increased levels of potentially senescent hepatocytes with large nuclear foci, containing 53BP1. Similarly, spontaneous accumulation of these cells seen with normal ageing in mice was increased with FOXM1 enrichment.

CONCLUSION

Despite its known abilities to promote proliferation and DNA repair, and to reduce ROS, enrichment of FOXM1, as with other oncoproteins, may cause increased persistent DNA lesions and/or senescence in normal murine hepatocytes.

FOXM1: A key oncofoetal transcription factor in health and disease

Forkhead Box M1 (FOXM1) is a bona fide oncofoetal transcription factor, which orchestrates complex temporal and spatial gene expression throughout embryonic and foetal development as well as during adult tissue homeostasis and repair. Controlled FOXM1 expression and activity provides a balanced transcriptional programme to ensure proper growth and maturation during embryogenesis and foetal development as well as to manage appropriate homeostasis and repair of adult tissues. Conversely, deregulated FOXM1 upregulation likely affects cell migration, invasion, angiogenesis, stem cell renewal, DNA damage repair and cellular senescence, which impact tumour initiation, progression, metastasis, angiogenesis and drug resistance. A thorough understanding of the regulation and role of FOXM1 in health and in cancer should contribute to the development of better diagnostics and treatments for cancer as well as congenital disorders and other developmental diseases.

Knockdown of 14-3-3ζ enhances radiosensitivity and radio-induced apoptosis in CD133(+) liver cancer stem cells

14-3-3ζ is related to many cancer survival cellular processes. In a previous study, we showed that silencing 14-3-3ζ decreases the resistance of hepatocellular carcinoma (HCC) to chemotherapy. In this study, we investigated whether silencing 14-3-3ζ affects the radioresistance of cancer stem-like cells (CSCs) in HCC. Knockdown of 14-3-3ζ decreased cell viability and the number of spheres by reducing radioresistance in CSCs after γ-irradiation (IR). Furthermore, the levels of pro-apoptotic proteins were upregulated in CSCs via silencing 14-3-3ζ after IR. These results suggest that 14-3-3ζ knockdown enhances radio-induced apoptosis by reducing radioresistance in liver CSCs.

The transcription factor FOXM1 (Forkhead box M1): proliferation-specific expression, transcription factor function, target genes, mouse models, and normal biological roles

FOXM1 (Forkhead box M1) is a typical proliferation-associated transcription factor, which stimulates cell proliferation and exhibits a proliferation-specific expression pattern. Accordingly, both the expression and the transcriptional activity of FOXM1 are increased by proliferation signals, but decreased by antiproliferation signals, including the positive and negative regulation by protooncoproteins or tumor suppressors, respectively. FOXM1 stimulates cell cycle progression by promoting the entry into S-phase and M-phase. Moreover, FOXM1 is required for proper execution of mitosis. Accordingly, FOXM1 regulates the expression of genes, whose products control G1/S-transition, S-phase progression, G2/M-transition, and M-phase progression. Additionally, FOXM1 target genes encode proteins with functions in the execution of DNA replication and mitosis. FOXM1 is a transcriptional activator with a forkhead domain as DNA binding domain and with a very strong acidic transactivation domain. However, wild-type FOXM1 is (almost) inactive because the transactivation domain is repressed by three inhibitory domains. Inactive FOXM1 can be converted into a very potent transactivator by activating signals, which release the transactivation domain from its inhibition by the inhibitory domains. FOXM1 is essential for embryonic development and the foxm1 knockout is embryonically lethal. In adults, FOXM1 is important for tissue repair after injury. FOXM1 prevents premature senescence and interferes with contact inhibition. FOXM1 plays a role for maintenance of stem cell pluripotency and for self-renewal capacity of stem cells. The functions of FOXM1 in prevention of polyploidy and aneuploidy and in homologous recombination repair of DNA-double-strand breaks suggest an importance of FOXM1 for the maintenance of genomic stability and chromosomal integrity.

Identification of cell cycle-regulated genes periodically expressed in U2OS cells and their regulation by FOXM1 and E2F transcription factors

Characterization of the cell cycle–regulated transcripts in U2OS cells yielded 1871 unique genes. FOXM1 targets were identified via ChIP-seq, and novel targets in G2/M and S phases were verified using a real-time luciferase assay. ChIP-seq data were used to map cell cycle transcriptional regulators of cell cycle–regulated gene expression in U2OS cells.

We identify the cell cycle–regulated mRNA transcripts genome-wide in the osteosarcoma-derived U2OS cell line. This results in 2140 transcripts mapping to 1871 unique cell cycle–regulated genes that show periodic oscillations across multiple synchronous cell cycles. We identify genomic loci bound by the G2/M transcription factor FOXM1 by chromatin immunoprecipitation followed by high-throughput sequencing (ChIP-seq) and associate these with cell cycle–regulated genes. FOXM1 is bound to cell cycle–regulated genes with peak expression in both S phase and G2/M phases. We show that ChIP-seq genomic loci are responsive to FOXM1 using a real-time luciferase assay in live cells, showing that FOXM1 strongly activates promoters of G2/M phase genes and weakly activates those induced in S phase. Analysis of ChIP-seq data from a panel of cell cycle transcription factors (E2F1, E2F4, E2F6, and GABPA) from the Encyclopedia of DNA Elements and ChIP-seq data for the DREAM complex finds that a set of core cell cycle genes regulated in both U2OS and HeLa cells are bound by multiple cell cycle transcription factors. These data identify the cell cycle–regulated genes in a second cancer-derived cell line and provide a comprehensive picture of the transcriptional regulatory systems controlling periodic gene expression in the human cell division cycle.

FOXM1 (Forkhead box M1) in tumorigenesis: overexpression in human cancer, implication in tumorigenesis, oncogenic functions, tumor-suppressive properties, and target of anticancer therapy

FOXM1 (Forkhead box M1) is a typical proliferation-associated transcription factor and is also intimately involved in tumorigenesis. FOXM1 stimulates cell proliferation and cell cycle progression by promoting the entry into S-phase and M-phase. Additionally, FOXM1 is required for proper execution of mitosis. In accordance with its role in stimulation of cell proliferation, FOXM1 exhibits a proliferation-specific expression pattern and its expression is regulated by proliferation and anti-proliferation signals as well as by proto-oncoproteins and tumor suppressors. Since these factors are often mutated, overexpressed, or lost in human cancer, the normal control of the foxm1 expression by them provides the basis for deregulated FOXM1 expression in tumors. Accordingly, FOXM1 is overexpressed in many types of human cancer. FOXM1 is intimately involved in tumorigenesis, because it contributes to oncogenic transformation and participates in tumor initiation, growth, and progression, including positive effects on angiogenesis, migration, invasion, epithelial-mesenchymal transition, metastasis, recruitment of tumor-associated macrophages, tumor-associated lung inflammation, self-renewal capacity of cancer cells, prevention of premature cellular senescence, and chemotherapeutic drug resistance. However, in the context of urethane-induced lung tumorigenesis, FOXM1 has an unexpected tumor suppressor role in endothelial cells because it limits pulmonary inflammation and canonical Wnt signaling in epithelial lung cells, thereby restricting carcinogenesis. Accordingly, FOXM1 plays a role in homologous recombination repair of DNA double-strand breaks and maintenance of genomic stability, that is, prevention of polyploidy and aneuploidy. The implication of FOXM1 in tumorigenesis makes it an attractive target for anticancer therapy, and several antitumor drugs have been reported to decrease FOXM1 expression.

Forkhead box M1 (FoxM1) gene is a new STAT3 transcriptional factor target and is essential for proliferation, survival and DNA repair of K562 cell line

The forkhead box (Fox) M1 gene belongs to a superfamily of evolutionarily conserved transcriptional regulators that are involved in a wide range of biological processes, and its deregulation has been implicated in cancer survival, proliferation and chemotherapy resistance. However, the role of FoxM1, the signaling involved in its activation and its role in leukemia are poorly known. Here, we demonstrate by gene promoter analysis, Electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) assays that FoxM1 is a new target of the STAT3 transcriptional activator. Additionally, FoxM1 is transcriptionally dependent on STAT3 signaling activation. Furthermore, we verified that FoxM1 is crucial for K562 cell proliferation, cell cycle checkpoints and viability and could be related to chemotherapeutic resistance. By microarray analysis, we determined the signaling pathways related to FoxM1 expression and its role in DNA repair using K562 cells. Our results revealed new signaling involved in FoxM1 expression and its role in leukemic cells that elucidate cellular mechanisms associated with the development of leukemia and disease progression.

Notch signaling regulates tumor-induced angiogenesis in SPARC-overexpressed neuroblastoma

Despite existing aggressive treatment modalities, the prognosis for advanced stage neuroblastoma remains poor with significant long-term illness in disease survivors. Advance stage disease features are associated with tumor vascularity, and as such, angiogenesis inhibitors may prove useful along with current therapies. The matricellular protein, secreted protein acidic and rich in cysteine (SPARC), is known to inhibit proliferation and migration of endothelial cells stimulated by growth factors. Here, we sought to determine the effect of SPARC on neuroblastoma tumor cell-induced angiogenesis and to decipher the molecular mechanisms involved in angiogenesis inhibition. Conditioned medium from SPARC-overexpressed neuroblastoma cells (pSPARC-CM) inhibited endothelial tube formation, cell proliferation, induced programmed cell death and suppressed expression of pro-angiogenic molecules such as VEGF, FGF, PDGF, and MMP-9 in endothelial cells. Further analyses revealed that pSPARC-CM-suppressed expression of growth factors was mediated by inhibition of the Notch signaling pathway, and cells cultured on conditioned medium from tumor cells that overexpress both Notch intracellular domain (NICD-CM) and SPARC resumed the pSPARC-CM-suppressed capillary tube formation and growth factor expression in vitro. Further, SPARC overexpression in neuroblastoma cells inhibited neo-vascularization in vivo in a mouse dorsal air sac model. Furthermore, SPARC overexpression-induced endothelial cell death was observed by co-localization studies with TUNEL assay and an endothelial marker, CD31, in xenograft tumor sections from SPARC-overexpressed mice. Our data collectively suggest that SPARC overexpression induces endothelial cell apoptosis and inhibits angiogenesis both in vitro and in vivo.

A bioinformatics filtering strategy for identifying radiation response biomarker candidates

The number of biomarker candidates is often much larger than the number of clinical patient data points available, which motivates the use of a rational candidate variable filtering methodology. The goal of this paper is to apply such a bioinformatics filtering process to isolate a modest number (<10) of key interacting genes and their associated single nucleotide polymorphisms involved in radiation response, and to ultimately serve as a basis for using clinical datasets to identify new biomarkers. In step 1, we surveyed the literature on genetic and protein correlates to radiation response, in vivo or in vitro, across cellular, animal, and human studies. In step 2, we analyzed two publicly available microarray datasets and identified genes in which mRNA expression changed in response to radiation. Combining results from Step 1 and Step 2, we identified 20 genes that were common to all three sources. As a final step, a curated database of protein interactions was used to generate the most statistically reliable protein interaction network among any subset of the 20 genes resulting from Steps 1 and 2, resulting in identification of a small, tightly interacting network with 7 out of 20 input genes. We further ranked the genes in terms of likely importance, based on their location within the network using a graph-based scoring function. The resulting core interacting network provides an attractive set of genes likely to be important to radiation response.

SPARC overexpression inhibits cell proliferation in neuroblastoma and is partly mediated by tumor suppressor protein PTEN and AKT

Secreted protein acidic and rich in cysteine (SPARC) is also known as BM-40 or Osteonectin, a multi-functional protein modulating cell–cell and cell–matrix interactions. In cancer, SPARC is not only linked with a highly aggressive phenotype, but it also acts as a tumor suppressor. In the present study, we sought to characterize the function of SPARC and its role in sensitizing neuroblastoma cells to radio-therapy. SPARC overexpression in neuroblastoma cells inhibited cell proliferation in vitro. Additionally, SPARC overexpression significantly suppressed the activity of AKT and this suppression was accompanied by an increase in the tumor suppressor protein PTEN both in vitro and in vivo. Restoration of neuroblastoma cell radio-sensitivity was achieved by overexpression of SPARC in neuroblastoma cells in vitro and in vivo. To confirm the role of the AKT in proliferation inhibited by SPARC overexpression, we transfected neuroblastoma cells with a plasmid vector carrying myr-AKT. Myr-AKT overexpression reversed SPARC-mediated PTEN and increased proliferation of neuroblastoma cells in vitro. PTEN overexpression in parallel with SPARC siRNA resulted in decreased AKT phosphorylation and proliferation in vitro. Taken together, these results establish SPARC as an effector of AKT-PTEN-mediated inhibition of proliferation in neuroblastoma in vitro and in vivo.

Suppression of FOXM1 sensitizes human cancer cells to cell death induced by DNA-damage

Irradiation and DNA-damaging chemotherapeutic agents are commonly used in anticancer treatments. Following DNA damage FOXM1 protein levels are often elevated. In this study, we sought to investigate the potential role of FOXM1 in programmed cell death induced by DNA-damage. Human cancer cells after FOXM1 suppression were subjected to doxorubicin or γ-irradiation treatment. Our findings indicate that FOXM1 downregulation by stable or transient knockdown using RNAi or by treatment with proteasome inhibitors that target FOXM1 strongly sensitized human cancer cells of different origin to DNA-damage-induced apoptosis. We showed that FOXM1 suppresses the activation of pro-apoptotic JNK and positively regulates anti-apoptotic Bcl-2, suggesting that JNK activation and Bcl-2 down-regulation could mediate sensitivity to DNA-damaging agent-induced apoptosis after targeting FOXM1. Since FOXM1 is widely expressed in human cancers, our data further support the fact that it is a valid target for combinatorial anticancer therapy.

ZDHHC8 knockdown enhances radiosensitivity and suppresses tumor growth in a mesothelioma mouse model

Mesothelioma is an aggressive tumor caused by asbestos exposure, the incidence of which is predicted to increase globally. The prognosis of patients with mesothelioma undergoing conventional therapy is poor. Radiation therapy for mesothelioma is of limited use because of the intrinsic radioresistance of tumor cells compared with surrounding normal tissue. Thus, a novel molecular-targeted radiosensitizing agent that enhances the radiosensitivity of mesothelioma cells is required to improve the therapeutic efficacy of radiation therapy. ZDHHC8 knockdown reduces cell survival and induces an impaired G(2) /M checkpoint after X-irradiation in HEK293 cells. In the present study, we further analyzed the effect of the combination of ZDHHC8 knockdown and X-irradiation and assessed its therapeutic efficacy in mesothelioma models. SiRNA-induced ZDHHC8 knockdown in 211H and H2052 mesothelioma cells significantly reduced cell survival after X-irradiation. In 211H cells treated with ZDHHC8 siRNA and X-irradiation, the G(2) /M checkpoint was impaired and there was an increase in the number of cells with micronuclei, as well as apoptotic cells, in vitro. In 211H tumor-bearing mice, ZDHHC8 siRNA and X-irradiation significantly suppressed tumor growth, whereas ZDHHC8 siRNA alone did not. Immunohistochemical analysis showed decreased cell proliferation and induction of apoptosis in tumors treated with ZDHHC8 siRNA and X-irradiation, but not with ZDHHC8 siRNA alone. These results suggest that ZDHHC8 knockdown with X-irradiation induces chromosomal instability and apoptosis through the impaired G(2) /M checkpoint. In conclusion, the combination of ZDHHC8 siRNA and X-irradiation has the potential to improve the therapeutic efficacy of radiation therapy for malignant mesothelioma.

CD133+ liver cancer stem cells modulate radioresistance in human hepatocellular carcinoma

CD133 is a cancer stem-cell (CSC) marker associated with radioresistance and chemoresistance in various cancers. In the present study, CD133-expressing liver cancer cells following radiation exposure showed higher activation of MAPK/PI3K signaling pathway and reduction in reactive oxygen species levels compared to CD133- cells. The in vivo study with a xenograft model showed increased tumor formation in irradiated CD133+ cell-injected nude mice compared to the CD133- group, suggesting that CD133 contributes to radioresistance in HCC. Therefore, CD133-expressing liver cancer cells have anti-apoptotic and radioresistance properties that may be useful to improve anti-cancer treatments, including chemotherapy/radiotherapy of HCC.

MMP-2 siRNA inhibits radiation-enhanced invasiveness in glioma cells

Background

Our previous work and that of others strongly suggests a relationship between the infiltrative phenotype of gliomas and the expression of MMP-2. Radiation therapy, which represents one of the mainstays of glioma treatment, is known to increase cell invasion by inducing MMP-2. Thus, inhibition of MMP-2 provides a potential means for improving the efficacy of radiotherapy for malignant glioma.

Methodology/Principal Findings

We have tested the ability of a plasmid vector-mediated MMP-2 siRNA (p-MMP-2) to modulate ionizing radiation-induced invasive phenotype in the human glioma cell lines U251 and U87. Cells that were transfected with p-MMP-2 with and without radiation showed a marked reduction of MMP-2 compared to controls and pSV-transfected cells. A significant reduction of proliferation, migration, invasion and angiogenesis of cells transfected with p-MMP-2 and in combination with radiation was observed compared to controls. Western blot analysis revealed that radiation-enhanced levels of VEGF, VEGFR-2, pVEGFR-2, p-FAK, and p-p38 were inhibited with p-MMP-2-transfected cells. TUNEL staining showed that radiation did not induce apoptosis in U87 and U251 cells while a significant increase in TUNEL-positive cells was observed when irradiated cells were simultaneously transfected with p-MMP-2 as compared to controls. Intracranial tumor growth was predominantly inhibited in the animals treated with p-MMP-2 alone or in combination with radiation compared to controls.

Conclusion/Significance

MMP-2 inhibition, mediated by p-MMP-2 and in combination with radiation, significantly reduced tumor cell migration, invasion, angiogenesis and tumor growth by modulating several important downstream signaling molecules and directing cells towards apoptosis. Taken together, our results demonstrate the efficacy of p-MMP-2 in inhibiting radiation-enhanced tumor invasion and progression and suggest that it may act as a potent adjuvant for radiotherapy in glioma patients.

Suppression of MMP-2 attenuates TNF-α induced NF-κB activation and leads to JNK mediated cell death in glioma

Background

Abrogation of apoptosis for prolonged cell survival is essential in cancer progression. In our previous studies, we showed the MMP-2 downregulation induced apoptosis in cancer cell lines. Here, we attempt to investigate the exact molecular mechanism of how MMP-2 depletion leads to apoptosis in glioma xenograft cell lines.

Methodology/Principal Findings

MMP-2 transcriptional suppression by MMP-2siRNA (pM) induces apoptosis associated with PARP, caspase-8 and -3 cleavage in human glioma xenograft cells 4910 and 5310. Western blotting and cytokine array showed significant decrease in the cellular and secreted levels of TNF-α with concomitant reduction in TNFR1, TRADD, TRAF2, RIP, IKKβ and pIκBα expression levels resulting in inhibition of p65 phosphorylation and nuclear translocation in pM-treated cells when compared to mock and pSV controls. In addition MMP-2 suppression led to elevated Fas-L, Fas and FADD expression levels along with increased p38 and JNK phosphorylation. The JNK-activity assay showed prolonged JNK activation in pM-transfected cells. Specific inhibition of p38 with SB203580 did not show any effect whereas inhibition of JNK phosphorylation with SP600125 notably reversed pM-induced cleavage of PARP, caspase-8 and -3, demonstrating a significant role of JNK in pM-induced cell death. Supplementation of rhMMP-2 counteracted the effect of pM by remarkably elevating TNF-α, TRADD, IKKβ and pIκBα expression and decreasing FADD, Fas-L, and phospho-JNK levels. The EMSA analysis indicated significant reversal of pM-inhibited NF-κB activity by rhMMP-2 treatment which rescued cells from pM-induced cell death. In vivo studies indicated that pM treatment diminished intracranial tumor growth and the immuno histochemical analysis showed decreased phospho-p65 and enhanced phospho-JNK levels that correlated with increased TUNEL-positive apoptotic cells in pM-treated tumor sections.

Conclusion/Significance

In summary, our study implies a role of MMP-2 in the regulation of TNF-α mediated constitutive NF-κB activation and Fas-mediated JNK mediated apoptosis in glioma xenograft cells in vitro and in vivo.

αVβ3 integrin regulates macrophage inflammatory responses via PI3 kinase/Akt-dependent NF-κB activation

Controlling macrophage responses to pathogenic stimuli is critical for prevention of and recovery from the inflammatory state associated with the pathogenesis of many diseases. The adhesion receptor αVβ3 integrin is thought to be an important receptor that regulates macrophage differentiation and macrophage responses to external signaling, but it has not been previously identified as a contributor to macrophage-related inflammation. Using an in vitro model of human blood monocytes (Mo) and monocyte-derived macrophages (MDMs) we demonstrate that αVβ3 ligation results in sustained increases of the transcription factor NF-κB DNA-binding activity, as compared with control isotype-matched IgG(1). Activation of NF-κB parallels the increase of NF-κB-dependent pro-inflammatory cytokine mRNA expression in MDMs isolated from individual donors, for example, TNF-α (8- to 28-fold), IL-1β (15- to 30-fold), IL-6 (2- to 4-fold), and IL-8 (5- to 15-fold) whereas there is more than a 10-fold decrease in IL-10 mRNA level occurs. Upon ligation of the αVβ3 receptor, treatment with TNF-α (10 ng/ml) or LPS (200 ng/ml, 1,000 EU) results in the enhanced and synergistic activation of NF-κB and LPS-induced TNF-α secretion. As additional controls, an inhibitor of αVβ3 integrin, cyclic RGD (10 µg/ml; IC(50) = 7.6 µM), attenuates the effects of αVβ3 ligation, and the natural ligand of αVβ3 integrin, vitronectin, reproduces the effects of αVβ3 activation by an immobilizing anti-αVβ3 integrin mAb. We hypothesize that αVβ3 activation can maintain chronic inflammatory processes in pathological conditions and that the loss of αVβ3 ligation will allow macrophages to escape from the inflammatory state.

Two-fold elevation of expression of FoxM1 transcription factor in mouse embryonic fibroblasts enhances cell cycle checkpoint activity by stimulating p21 and Chk1 transcription

OBJECTIVES

Forkhead Box M1 (FoxM1) transcription factor regulates expression of cell cycle effective genes and is stabilized by checkpoint kinase 2 (Chk2) to stimulate expression of DNA repair enzymes in response to DNA damage. This study intended to test whether FoxM1 is involved in cell cycle checkpoint pathways.

MATERIALS AND METHODS

Analysis of senescence and cell proliferation in FoxM1 transgenic (TG) mouse embryonic fibroblasts (MEFs) with 2-fold elevation of FoxM1, and overexpression or knockdown of FoxM1 in an inducible FoxM1 expression cell line, or FoxM1 siRNA. Chromatin immunoprecipitation (ChIP), electrophoretic mobility shift assays (EMSA), and cotransfection to determine FoxM1 transcription targets, as well as RNase protection assays and western blot analysis, were performed.

RESULTS

Two-fold elevation of FoxM1 in FoxM1-TG-MEFs resulted in low levels of cell proliferation and increase in permanent cell cycle arrest at early passages (from passage 6 to 9). These phenotypes correlated with increased phosphorylation of p53 on Ser15, elevated expression of cell cycle inhibitor p21 and Chk1 at passage 3. FoxM1 was stabilized in response to DNA damage in MEFs and FoxM1 overexpression induced p21. Knockdown of FoxM1 resulted in decrease in Chk1. ChIP, EMSA and cotransfection assays confirmed that FoxM1 stimulated promoters of p21 and Chk1.

CONCLUSIONS

Chk1 and p21 are direct transcription targets of FoxM1 and FoxM1 participates in transcriptional responses to stress in normal cells.