FoxM1 inhibition sensitizes resistant glioblastoma cells to temozolomide by downregulating the expression of DNA-repair gene Rad51

FOXM1 transcriptional regulation

FOXM1 is a key transcriptional regulator involved in various biological processes in mammals, including carbohydrate and lipid metabolism, aging, immune regulation, development, and disease. Early studies have shown that FOXM1 acts as an oncogene by regulating cell proliferation, cell cycle, migration, metastasis, and apoptosis, as well as genes related to diagnosis, treatment, chemotherapy resistance, and prognosis. Researchers are increasingly focusing on FOXM1 functions in tumor microenvironment, epigenetics, and immune infiltration. However, researchers have not comprehensively described FOXM1's involvement in tumor microenvironment shaping, epigenetics, and immune cell infiltration. Here we review the role of FOXM1 in the formation and development of malignant tumors, and we will provide a comprehensive summary of the role of FOXM1 in transcriptional regulation, interacting proteins, tumor microenvironment, epigenetics, and immune infiltration, and suggest areas for further research.

Synthesis and Antitumour Evaluation of Tricyclic Indole-2-Carboxamides against Paediatric Brain Cancer Cells

Antitumour properties of some cannabinoids (CB) have been reported in the literature as early as 1970s, however there is no clear consensus to date on the exact mechanisms leading to cancer cell death. The indole-based WIN 55,212-2 and SDB-001 are both known as potent agonists at both CB1 and CB2 receptors, yet we demonstrate herein that only the former can exert in vitro antitumour effects when tested against a paediatric brain cancer cell line KNS42. In this report, we describe the synthesis of novel 3,4-fused tricyclic indoles and evaluate their functional potencies at both cannabinoid receptors, as well as their abilities to inhibit the growth or proliferation of KNS42 cells. Compared to our previously reported indole-2-carboxamides, these 3,4-fused tricyclic indoles had either completely lost activities, or, showed moderate-to-weak antagonism at both CB1 and CB2 receptors. Compound 23 displayed the most potent antitumour properties among the series. Our results further support the involvement of non-CB pathways for the observed antitumour activities of amidoalkylindole-based cannabinoids, in line with our previous findings. Transcriptomic analysis comparing cells treated or non-treated with compound 23 suggested the observed antitumour effects of 23 are likely to result mainly from disruption of the FOXM1-regulated cell cycle pathways.

FOXP3 promote the progression of glioblastoma via inhibiting ferroptosis mediated by linc00857/miR-1290/GPX4 axis

The oncogenic properties of members belonging to the forkhead box (FOX) family have been extensively documented in different types of cancers. In this study, our objective was to investigate the impact of FOXP3 on glioblastoma multiforme (GBM) cells. By conducting a screen using a small hairpin RNA (shRNA) library, we discovered a significant association between FOXP3 and ferroptosis in GBM cells. Furthermore, we observed elevated levels of FOXP3 in both GBM tissues and cell lines, which correlated with a poorer prognosis. FOXP3 was found to promote the proliferation of GBM cells by inhibiting cell ferroptosis in vitro and in vivo. Mechanistically, FOXP3 not only directly upregulated the transcription of GPX4, but also attenuated the degradation of GPX4 mRNA through the linc00857/miR-1290 axis, thereby suppressing ferroptosis and promoting proliferation. Additionally, the FOXP3 inhibitor epirubicin exhibited the ability to impede proliferation and induce ferroptosis in GBM cells both in vitro and in vivo. In summary, our study provided evidences that FOXP3 facilitates the progression of glioblastoma by inhibiting ferroptosis via the linc00857/miR-1290/GPX4 axis, highlighting FOXP3 as a potential therapeutic target for GBM.

The Promise of Combination Therapies with FOXM1 Inhibitors for Cancer Treatment

Forkhead box M1 (FOXM1) is a transcription factor in the forkhead (FOX) family, which is required for cellular proliferation in normal and neoplastic cells. FOXM1 is highly expressed in many different cancers, and its expression is associated with a higher tumor stage and worse patient-related outcomes. Abnormally high expression of FOXM1 in cancers compared to normal tissue makes FOXM1 an attractive target for pharmacological inhibition. FOXM1-inhibiting agents and specific FOXM1-targeted small-molecule inhibitors have been developed in the lab and some of them have shown promising efficacy and safety profiles in mouse models. While the future goal is to translate FOXM1 inhibitors to clinical trials, potential synergistic drug combinations can maximize anti-tumor efficacy while minimizing off-target side effects. Hence, we discuss the rationale and efficacy of all previously studied drug combinations with FOXM1 inhibitors for cancer therapies.

Targeting FBXO22 enhances radiosensitivity in non-small cell lung cancer by inhibiting the FOXM1/Rad51 axis

Radioresistance is a major constraint on the efficacy of lung cancer radiotherapy, but its mechanism has not been fully elucidated. Here, we found that FBXO22 was aberrantly highly expressed in lung cancer and that FBXO22 knockdown increased the radiosensitivity of lung cancer cells. Mechanistically, FBXO22 promoted Rad51 gene transcription by increasing the level of FOXM1 at the Rad51 promoter, thereby inducing the formation of lung cancer radioresistance. Furthermore, we found that deguelin, a potential inhibitor of FBXO22, enhanced radiosensitivity in an FBXO22/Rad51-dependent manner and was safely tolerated in vivo. Collectively, our results illustrate that FBXO22 induces lung cancer radioresistance by activating the FOXM1/Rad51 axis and provide preclinical evidence for the clinical translation of this critical target.

MGMT function determines the differential response of ATR inhibitors with DNA-damaging agents in glioma stem cells for GBM therapy

Background

The most prevalent cancer treatments cause cell death through DNA damage. However, DNA damage response (DDR) repair pathways, initiated by tumor cells, can withstand the effects of anticancer drugs, providing justification for combining DDR inhibitors with DNA-damaging anticancer treatments.

Methods

Cell viability assays were performed with CellTiter-Glo assay. DNA damage was evaluated using Western blotting analysis. RNA-seq and single-cell level expression were used to identify the DDR signatures. In vivo, studies were conducted in mice to determine the effect of ATris on TMZ sensitization.

Results

We found a subpopulation of glioma sphere-forming cells (GSCs) with substantial synergism with temozolomide (TMZ) using a panel of 3 clinical-grade ataxia-telangiectasia- and Rad3-related kinase inhibitors (ATRis), (elimusertib, berzosertib, and ceralasertib). Interestingly, most synergistic cell lines had O6-methylguanine-DNA methyltransferase (MGMT) promoter methylation, indicating that ATRi mainly benefits tumors with no MGMT repair. Further, TMZ activated the ATR-checkpoint kinase 1 (Chk1) axis in an MGMT-dependent way. TMZ caused ATR-dependent Chk1 phosphorylation and DNA double-strand breaks as shown by increased γH2AX. Increased DNA damage and decreased Chk1 phosphorylation were observed upon the addition of ATRis to TMZ in MGMT-methylated (MGMT-) GSCs. TMZ also improved sensitivity to ATRis in vivo, as shown by increased mouse survival with the TMZ and ATRi combination treatment.

Conclusions

This research provides a rationale for selectively targeting MGMT-methylated cells using ATRis and TMZ combination. Overall, we believe that MGMT methylation status in GBM could serve as a robust biomarker for patient selection for ATRi combined with TMZ.

Forkhead box transcription factors (FOXOs and FOXM1) in glioma: from molecular mechanisms to therapeutics

Glioma is the most aggressive and malignant type of primary brain tumor, comprises the majority of central nervous system deaths, and is categorized into different subgroups according to its histological characteristics, including astrocytomas, oligodendrogliomas, glioblastoma multiforme (GBM), and mixed tumors. The forkhead box (FOX) transcription factors comprise a collection of proteins that play various roles in numerous complex molecular cascades and have been discovered to be differentially expressed in distinct glioma subtypes. FOXM1 and FOXOs have been recognized as crucial transcription factors in tumor cells, including glioma cells. Accumulating data indicates that FOXM1 acts as an oncogene in various types of cancers, and a significant part of studies has investigated its function in glioma. Although recent studies considered FOXO subgroups as tumor suppressors, there are pieces of evidence that they may have an oncogenic role. This review will discuss the subtle functions of FOXOs and FOXM1 in gliomas, dissecting their regulatory network with other proteins, microRNAs and their role in glioma progression, including stem cell differentiation and therapy resistance/sensitivity, alongside highlighting recent pharmacological progress for modulating their expression.

FOXM1, MEK, and CDK4/6: New Targets for Malignant Peripheral Nerve Sheath Tumor Therapy

Malignant peripheral nerve sheath tumors (MPNSTs) are deadly sarcomas, which desperately need effective therapies. Half of all MPNSTs arise in patients with neurofibromatosis type I (NF1), a common inherited disease. NF1 patients can develop benign lesions called plexiform neurofibromas (PNFs), often in adolescence, and over time, some PNFs, but not all, will transform into MPNSTs. A deeper understanding of the molecular and genetic alterations driving PNF-MPNST transformation will guide development of more targeted and effective treatments for these patients. This review focuses on an oncogenic transcription factor, FOXM1, which is a powerful oncogene in other cancers but little studied in MPNSTs. Elevated expression of FOXM1 was seen in patient MPNSTs and correlated with poor survival, but otherwise, its role in the disease is unknown. We discuss what is known about FOXM1 in MPNSTs relative to other cancers and how FOXM1 may be regulated by and/or regulate the most commonly altered players in MPNSTs, particularly in the MEK and CDK4/6 kinase pathways. We conclude by considering FOXM1, MEK, and CDK4/6 as new, clinically relevant targets for MPNST therapy.

Development of an interfering peptide M1-20 with potent anti-cancer effects by targeting FOXM1

Disrupting protein-protein interactions (PPIs) has emerged as a promising strategy for cancer drug development. Interfering peptides disrupting PPIs can be rationally designed based on the structures of natural sequences mediating these interactions. Transcription factor FOXM1 overexpresses in multiple cancers and is considered an effective target for cancer therapeutic drug development. Using a rational design approach, we have generated a peptide library from the FOXM1 C-terminal sequence and screened FOXM1-binding peptides. Combining FOXM1 binding and cell inhibitory results, we have obtained a FOXM1-targeting interfering peptide M1-20 that is optimized from the natural parent peptide to the D-retro-inverso peptide. With improved stability characteristics, M1-20 inhibits proliferation and migration, and induces apoptosis of cancer cells. Mechanistically, M1-20 inhibits FOXM1 transcriptional activities by disrupting its interaction between the MuvB complex and the transcriptional co-activator CBP. These are consistent with the results that M1-20 suppresses cancer progression and metastasis without noticeable toxic and side effects in wild-type mice. These findings reveal that M1-20 has the potential to be developed as an anti-cancer drug candidate targeting FOXM1.

Multiomics analyses reveal DARS1-AS1/YBX1-controlled posttranscriptional circuits promoting glioblastoma tumorigenesis/radioresistance

The glioblastoma (GBM) stem cell-like cells (GSCs) are critical for tumorigenesis/therapeutic resistance of GBM. Mounting evidence supports tumor-promoting function of long noncoding RNAs (lncRNAs), but their role in GSCs remains poorly understood. By combining CRISPRi screen with orthogonal multiomics approaches, we identified a lncRNA DARS1-AS1-controlled posttranscriptional circuitry that promoted the malignant properties of GBM cells/GSCs. Depleting DARS1-AS1 inhibited the proliferation of GBM cells/GSCs and self-renewal of GSCs, prolonging survival in orthotopic GBM models. DARS1-AS1 depletion also impaired the homologous recombination (HR)-mediated double-strand break (DSB) repair and enhanced the radiosensitivity of GBM cells/GSCs. Mechanistically, DARS1-AS1 interacted with YBX1 to promote target mRNA binding and stabilization, forming a mixed transcriptional/posttranscriptional feed-forward loop to up-regulate expression of the key regulators of G1-S transition, including E2F1 and CCND1. DARS1-AS1/YBX1 also stabilized the mRNA of FOXM1, a master transcription factor regulating GSC self-renewal and DSB repair. Our findings suggest DARS1-AS1/YBX1 axis as a potential therapeutic target for sensitizing GBM to radiation/HR deficiency-targeted therapy.

Morin Sensitizes MDA-MB-231 Triple-Negative Breast Cancer Cells to Doxorubicin Cytotoxicity by Suppressing FOXM1 and Attenuating EGFR/STAT3 Signaling Pathways

Considerable emphasis is being placed on combinatorial chemotherapeutic/natural treatments for breast cancer. This study reveals the synergistic anti-tumor activity of morin and Doxorubicin (Dox) co-treatment on MDA-MB-231 triple-negative breast cancer (TNBC) cell proliferation. Morin/Dox treatment promoted Dox uptake and induced DNA damage and formation of nuclear foci of p-H2A.X. Furthermore, DNA repair proteins, RAD51 and survivin, and cell cycle proteins, cyclin B1 and forkhead Box M1 (FOXM1), were induced by Dox alone but attenuated by morin/Dox co-treatment. In addition, Annexin V/7-AAD analysis revealed that necrotic cell death after co-treatment and apoptotic cell death by Dox alone were associated with the induction of cleaved PARP and caspase-7 without Bcl-2 family involvement. FOXM1 inhibition by thiostrepton showed that co-treatment caused FOXM1-mediated cell death. Furthermore, co-treatment downregulated the phosphorylation of EGFR and STAT3. Flow cytometry showed that the accumulation of cells in the G2/M and S phases might be linked to cellular Dox uptake, p21 upregulation, and cyclin D1 downregulation. Taken together, our study shows that the anti-tumor effect of morin/Dox co-treatment is due to the suppression of FOXM1 and attenuation of EGFR/STAT3 signaling pathways in MDA-MB-231 TNBC cells, which suggests that morin offers a means of improving therapeutic efficacy in TNBC patients.

RBBP4 regulates the expression of the Mre11-Rad50-NBS1 (MRN) complex and promotes DNA double-strand break repair to mediate glioblastoma chemoradiotherapy resistance

For treatment of glioblastoma (GBM), temozolomide (TMZ) and radiotherapy (RT) exert antitumor effects by inducing DNA double-strand breaks (DSBs), mainly via futile DNA mismatch repair (MMR) and inducing apoptosis. Here, we provide evidence that RBBP4 modulates glioblastoma resistance to chemotherapy and radiotherapy by recruiting transcription factors and epigenetic regulators that bind to their promoters to regulate the expression of the Mre11-Rad50-NBS1(MRN) complex and the level of DNA-DSB repair, which are closely associated with recovery from TMZ- and radiotherapy-induced DNA damage in U87MG and LN229 glioblastoma cells, which have negative MGMT expression. Disruption of RBBP4 induced GBM cell DNA damage and apoptosis in response to TMZ and radiotherapy and enhanced radiotherapy and chemotherapy sensitivity by the independent pathway of MGMT. These results displayed a possible chemo-radioresistant mechanism in MGMT negative GBM. In addition, the RBBP4-MRN complex regulation axis may provide an interesting target for developing therapy-sensitizing strategies for GBM.

MiR-4521 perturbs FOXM1-mediated DNA damage response in breast cancer

Introduction: Forkhead (FOX) transcription factors are involved in cell cycle control, cellular differentiation, maintenance of tissues, and aging. Mutation or aberrant expression of FOX proteins is associated with developmental disorders and cancers. FOXM1, an oncogenic transcription factor, is a promoter of cell proliferation and accelerated development of breast adenocarcinomas, squamous carcinoma of the head, neck, and cervix, and nasopharyngeal carcinoma. High FOXM1 expression is correlated with chemoresistance in patients treated with doxorubicin and Epirubicin by enhancing the DNA repair in breast cancer cells. Method: miRNA-seq identified downregulation of miR-4521 in breast cancer cell lines. Stable miR-4521 overexpressing breast cancer cell lines (MCF-7, MDA-MB-468) were developed to identify miR-4521 target gene and function in breast cancer. Results: Here, we showed that FOXM1 is a direct target of miR-4521 in breast cancer. Overexpression of miR-4521 significantly downregulated FOXM1 expression in breast cancer cells. FOXM1 regulates cell cycle progression and DNA damage response in breast cancer. We showed that miR-4521 expression leads to increased ROS levels and DNA damage in breast cancer cells. FOXM1 plays a critical role in ROS scavenging and promotes stemness which contributes to drug resistance in breast cancer. We observed that breast cancer cells stably expressing miR-4521 lead to cell cycle arrest, impaired FOXM1 mediated DNA damage response leading to increased cell death in breast cancer cells. Additionally, miR-4521-mediated FOXM1 downregulation perturbs cell proliferation, invasion, cell cycle progression, and epithelial-to-mesenchymal progression (EMT) in breast cancer. Discussion: High FOXM1 expression has been associated with radio and chemoresistance contributing to poor patient survival in multiple cancers, including breast cancer. Our study showed that FOXM1 mediated DNA damage response could be targeted using miR-4521 mimics as a novel therapeutic for breast cancer.

Temozolomide increases heat shock proteins in extracellular vesicles released from glioblastoma cells

BACKGROUND

Glioblastoma (GBM) is the most malignant and the fastest-progressing type of primary brain tumours. Temozolomide (TMZ) is a chemotherapeutic drug for the treatment of GBM. Extracellular vesicles (EVs) have been recently confirmed to have a substantial role in the GBM, and their contents released from GBM cells have been considered a target for treatment. The purpose of this study is to evaluate the impact of TMZ on heat shock proteins (HSPs) derived from EVs originated from GBM cell lines (U87-MG and LN229) and the significance of EVs in response to chemotherapy in GBM.

METHODS AND RESULTS

NTA, ELISA, and immunoblotting were used to characterization studies of EVs and results showed that U87-MG cells released many EVs compared to LN229 cells. The effect of TMZ treatments on HSPs expression levels were assessed with immunoblotting and was found to be led to increases in HSF-1, Hsp90, Hsp70, Hsp60 and Hsp27 expression in GBM cells and their EV contents, which these increases are related to therapeutic resistance. What is more, in Real-time PCR studies showing which signalling pathways might be associated with these increases, it was observed that TMZ triggered the expression of RAD51 and MDM2 genes in cells and EV contents. More strikingly, we discover a correlation between EV and parental cells in regard of mRNA and protein level in both cell lines as a result of TMZ treatment.

CONCLUSIONS

Our data suggest of EVs in the treatment of GBM may have potential biomarkers that can be used to investigate the treatment response.

Impact of Neoadjuvant Bevacizumab on Neuroradiographic Response and Histological Findings Related to Tumor Stemness and the Hypoxic Tumor Microenvironment in Glioblastoma: Paired Comparison Between Newly Diagnosed and Recurrent Glioblastomas

Background

Previously, we reported that bevacizumab (Bev) produces histological and neuroradiographic alterations including changes in tumor oxygenation, induction of an immunosupportive tumor microenvironment, and inhibition of stemness. To confirm how those effects vary during Bev therapy, paired samples from the same patients with newly diagnosed glioblastoma (GBM) who received preoperative neoadjuvant Bev (neoBev) were investigated with immunohistochemistry before and after recurrence.

Methods

Eighteen samples from nine patients with newly diagnosed GBM who received preoperative neoBev followed by surgery and chemoradiotherapy and then autopsy or salvage surgery after recurrence were investigated. The expression of carbonic anhydrase 9 (CA9), hypoxia-inducible factor-1 alpha (HIF-1α), nestin, and Forkhead box M1 (FOXM1) was evaluated with immunohistochemistry.

For comparison between neoBev and recurrent tumors, we divided the present cohort into two groups based on neuroradiographic response: good and poor responders (GR and PR, respectively) to Bev were defined by the tumor regression rate on T1-weighted images with gadolinium enhancement (T1Gd) and fluid-attenuated inversion recovery images. Patterns of recurrence after Bev therapy were classified as cT1 flare-up and T2-diffuse/T2-circumscribed. Furthermore, we explored the possibility of utilizing FOXM1 as a biomarker of survival in this cohort.

Results

A characteristic “pseudo-papillary”-like structure containing round-shaped tumor cells clustered adjacent to blood vessels surrounded by spindle-shaped tumor cells was seen only in recurrent tumors. Tumor cells at the outer part of the “pseudo-papillary” structure were CA9-positive (CA9+)/HIF-1α+, whereas cells at the inner part of this structure were CA9−/HIF-1α+ and nestin+/FOXM1+. CA9 and HIF-1α expression was lower in T1Gd-GR and decreased in the “T2-circumscribed/T2-diffuse” pattern compared with the “T1 flare-up” pattern, suggesting that tumor oxygenation was frequently observed in T1Gd-GR in initial tumors and in the “T2-circumscribed/T2-diffuse” pattern in recurrent tumors. FOXM1 low-expression tumors tended to have a better prognosis than that of FOXM1 high-expression tumors.

Conclusion

A “pseudo-papillary” structure was seen in recurrent GBM after anti-vascular endothelial growth factor therapy. Bev may contribute to tumor oxygenation, leading to inhibition of stemness and correlation with a neuroimaging response during Bev therapy. FOXM1 may play a role as a biomarker of survival during Bev therapy.

TRIM56 Reduces Radiosensitization of Human Glioblastoma by Regulating FOXM1-Mediated DNA Repair

Recurrent glioblastoma is characterized by resistance to radiotherapy or chemotherapy. In this study, we investigated the role of TRIM56 in radiosensitization and its potential underlying molecular mechanism. TRIM56 expression levels were measured in glioblastoma tissues and cell lines by immunohistochemical staining, western blot, and qRT-PCR. MTT assay, colony formation assay, and TUNEL assay were used to investigate the effect of TRIM56 on cell viability, cell proliferation, and cell apoptosis. Co-immunoprecipitation was used to clarify the interaction between TRIM56 and FOXM1. Finally, tumor xenograft experiments were performed to analyze the effect of TRIM56 on tumor growth in vivo. The expression of TRIM56 was significantly increased in glioblastoma tissues and cell lines and its expression was associated with poor prognosis of patients with glioblastoma. Moreover, TRIM56 reduced the radiosensitivity of glioblastoma cells and promoted DNA repairment. Mechanistically, TRIM56 promoted FOXM1 protein level, enhanced the stability of FOXM1 by de-ubiquitination, and promoted DNA damage repair through FOXM1 in glioblastoma cells. TRIM56 could reduce the radiosensitivity of glioblastoma in vivo. TRIM56 may suppress the radiosensitization of human glioblastoma by regulating FOXM1-mediated DNA repair. Targeting the TRIM56 may be an effective method to reverse radiotherapy-resistant in glioblastoma recurrent.

Next generation sequencing of BRCA genes in glioblastoma multiform Egyptian patients: a pilot study

BACKGROUND

Germ line mutations of BRCA1 and BRCA2 were correlated with a variety of cancer Authors aimed to use next-generation sequencing (NGS) to detect BRCA1 and BRCA2 germ line mutations in glioblastoma multiform (GBM) Egyptian patients.

MATERIALS AND METHODS

Genomic DNA was extracted from six GBM cases, amplified using Ion AmpliSeq BRCA1 and BRCA2 panel. DNA libraries were pooled, barcoded and finally sequenced using Ion Torrent Personal Genome Machine sequencer.

RESULTS

BRCA1 the previously reported rs1799966, rs1799950, rs16941 were found in five cases and they are in a linkage disequilibrium forming two distinct haplotypes, which might support their role in cancer predisposition. Out of the 18 reported variants in BRCA2, three denovo mutations were detected which leads to frame shift.

CONCLUSION

Further studies on large number of GBM patients and control cases to determine BRCA1 and BRCA2 germline mutations and haplotypes; diagnostic and prognostic role are encouraged.

SOCS5 contributes to temozolomide resistance in glioblastoma by regulating Bcl-2-mediated autophagy

Temozolomide (TMZ) is the primary chemotherapeutic drug for treating glioblastoma (GBM); however, the final clinical outcome is considerably limited by the poor response and resistance to TMZ. Although autophagy is thought to be associated with chemotherapy resistance and cancer cell survival, the precise molecular mechanisms underlying this process remain elusive. The suppressor of cytokine signaling (SOCS) family is widely distributed in vivo and exerts a range of effects on tumors; however, the expression pattern and role of SOCS in GBM remains unknown. In this study, we determined that high SOCS5 expression level was associated with poor prognosis and TMZ resistance in GBM. TMZ induced an increase in SOCS5 expression level and upregulated autophagy during the acquisition of drug resistance. The observed increase in the extent of autophagy was mediated by SOCS5. Mechanistically, SOCS5 enhances the transcription of Bcl-2. Knockdown of SOCS5 inhibited TMZ chemoresistance in GBM cells through the inhibition of Bcl-2 recruited autophagy; upregulation of Bcl-2 blocked this effect. In summary, our findings revealed the involvement and underlying mechanism of SOCS5 in TMZ resistance. SOCS5 plays a critical role in GBM chemoresistance and may serve as a novel prognostic marker and therapeutic target for chemotherapeutically treating drug-resistant GBM.

A novel DNA damage and repair-related gene signature to improve predictive capacity of overall survival for patients with gliomas

Gliomas, as the most lethal and malignant brain tumours in adults, remain a major challenge worldwide. DNA damage and repair‐related genes (DDRRGs) appear to play a significant role in gliomas, but the studies of DDRRGs are still insufficient. Herein, we systematically explored and analysed 1547 DDRRGs in 938 glioma samples from TCGA and CGGA datasets. Using least absolute shrinkage and selection operator (LASSO) Cox regression analysis, we identified a 16‐DDRRG signature, characterized by high‐risk and low‐risk patterns. This risk model harbours robust predictive capability for overall survival of glioma patients. We found the high‐risk score is strongly associated with well‐known malignant features of gliomas, such as the mesenchymal subtype, IDH‐wildtype, 1p/19q non‐codeletion and MGMT promoter unmethylated status. In addition, we found that the high‐risk score is also linked with multiple oncogenic pathways and therapeutic resistance. Significantly, we found the high‐risk group has higher enrichment of immunosuppressive cells (M2‐type macrophages, Tregs and MDSCs) and immune inhibition biomarkers (PD‐1, PD‐L1 and CTLA‐4). Lastly, we proved that SMC4, which has the highest positive regression coefficient in our risk model, is strongly linked with malignant progression and TMZ resistance of gliomas in a E2F1‐dependent manner.

Cannabidiol Inhibits RAD51 and Sensitizes Glioblastoma to Temozolomide in Multiple Orthotopic Tumor Models

Background

Cannabidiol (CBD), a nonpsychoactive cannabinoid with a low toxicity profile, has been shown to produce antitumor activity across cancers in part through selective production of reactive oxygen species (ROS) in tumor cells. The alkylating agent, temozolomide (TMZ), is standard of care for treatment of glioblastoma (GBM). It can trigger increased ROS to induce DNA damage. It has also been reported that downregulating the expression of RAD51, an important DNA damage repair protein, leads to sensitization of GBM to TMZ.

Methods

We determined the extent to which CBD enhanced the antitumor activity of TMZ in multiple orthotopic models of GBM. In addition, we investigated the potential for CBD to enhance the antitumor activity of TMZ through production of ROS and modulation of DNA repair pathways.

Results

CBD enhanced the activity of TMZ in U87 MG and U251 GBM cell lines and in patient-derived primary GBM163 cells leading to stimulation of ROS, activation of the ROS sensor AMP-activated protein kinase (AMPK), and upregulation of the autophagy marker LC3A. CBD produced a sensitization of U87 and GBM163-derived intracranial (i.c.) tumors to TMZ and significantly increased survival of tumor-bearing mice. However, these effects were not observed in orthotopic models derived from GBM with intact methylguanine methyltransferase (MGMT) expression. We further demonstrate that CBD inhibited RAD51 expression in MGMT-methylated models of GBM, providing a potential mechanism for tumor sensitization to TMZ by CBD.

Conclusion

These data support the potential therapeutic benefits of using CBD to enhance the antitumor activity of TMZ in GBM patients.

Artemisinin Mediates Its Tumor-Suppressive Activity in Hepatocellular Carcinoma Through Targeted Inhibition of FoxM1

The aberrant up-regulation of the oncogenic transcription factor Forkhead box M1 (FoxM1) is associated with tumor development, progression and metastasis in a myriad of carcinomas, thus establishing it as an attractive target for anticancer drug development. FoxM1 overexpression in hepatocellular carcinoma is reflective of tumor aggressiveness and recurrence, poor prognosis and low survival in patients. In our study, we have identified the antimalarial natural product, Artemisinin, to efficiently curb FoxM1 expression and activity in hepatic cancer cells, thereby exhibiting potential anticancer efficacy. Here, we demonstrated that Artemisinin considerably mitigates FoxM1 transcriptional activity by disrupting its interaction with the promoter region of its downstream targets, thereby suppressing the expression of numerous oncogenic drivers. Augmented level of FoxM1 is implicated in drug resistance of cancer cells, including hepatic tumor cells. Notably, FoxM1 overexpression rendered HCC cells poorly responsive to Artemisinin-mediated cytotoxicity while FoxM1 depletion in resistant liver cancer cells sensitized them to Artemisinin treatment, manifested in lower proliferative and growth index, drop in invasive potential and repressed expression of EMT markers with a concomitantly increased apoptosis. Moreover, Artemisinin, when used in combination with Thiostrepton, an established FoxM1 inhibitor, markedly reduced anchorage-independent growth and displayed more pronounced death in liver cancer cells. We found this effect to be evident even in the resistant HCC cells, thereby putting forth a novel combination therapy for resistant cancer patients. Altogether, our findings provide insight into the pivotal involvement of FoxM1 in the tumor suppressive activities of Artemisinin and shed light on the potential application of Artemisinin for improved therapeutic response, especially in resistant hepatic malignancies. Considering that Artemisinin compounds are in current clinical use with favorable safety profiles, the results from our study will potentiate its utility in juxtaposition with established FoxM1 inhibitors, promoting maximal therapeutic efficacy with minimal adverse effects in liver cancer patients.

Overexpression of HMGA1 confers radioresistance by transactivating RAD51 in cholangiocarcinoma

Cholangiocarcinomas (CCAs) are rare but aggressive tumors of the bile ducts. CCAs are often diagnosed at an advanced stage and respond poorly to current conventional radiotherapy and chemotherapy. High mobility group A1 (HMGA1) is an architectural transcription factor that is overexpressed in multiple malignant tumors. In this study, we showed that the expression of HMGA1 is frequently elevated in CCAs and that the high expression of this gene is associated with a poor prognosis. Functionally, HMGA1 promotes CCA cell proliferation/invasion and xenograft tumor growth. Furthermore, HMGA1 transcriptionally activates RAD51 by binding to its promoter through two HMGA1 response elements. Notably, overexpression of HMGA1 promotes radioresistance whereas its knockdown causes radiosensitivity of CCA cells to X-ray irradiation. Moreover, rescue experiments reveal that inhibition of RAD51 reverses the effect of HMGA1 on radioresistance and proliferation/invasion. These findings suggest that HMGA1 functions as a novel regulator of RAD51 and confers radioresistance in cholangiocarcinoma.

Dual Role of Integrin Alpha-6 in Glioblastoma: Supporting Stemness in Proneural Stem-Like Cells While Inducing Radioresistance in Mesenchymal Stem-Like Cells

Simple Summary

Glioblastoma stem-like cells (GSCs) are responsible for most of the malignant characteristics of glioblastoma, including therapeutic resistance, tumour recurrence, and tumour cellular heterogeneity. Therefore, increased understanding of the mechanisms regulating GSCs aggressiveness may help to improve patients’ outcomes. Here, we investigated the role of integrin a6 in controlling stemness and resistance to radiotherapy across proneural and mesenchymal molecular subtypes. We observed that integrin a6 had a clear role in stemness maintenance in proneural but not in mesenchymal GSCs. In addition, we proved a crucial role of integrin a6 in supporting mesenchymal GSCs resistance to ionizing radiation. Finally, we highlighted that integrin a6 may control different stem-associated features in GSCs, depending on the molecular subtype. The inhibition of integrin a6 limits stem-like malignant characteristics in both GSCs subtypes and thus may potentially control tumour relapse following conventional treatment.

Abstract

Therapeutic resistance after multimodal therapy is the most relevant cause of glioblastoma (GBM) recurrence. Extensive cellular heterogeneity, mainly driven by the presence of GBM stem-like cells (GSCs), strongly correlates with patients’ prognosis and limited response to therapies. Defining the mechanisms that drive stemness and control responsiveness to therapy in a GSC-specific manner is therefore essential. Here we investigated the role of integrin a6 (ITGA6) in controlling stemness and resistance to radiotherapy in proneural and mesenchymal GSCs subtypes. Using cell sorting, gene silencing, RNA-Seq, and in vitro assays, we verified that ITGA6 expression seems crucial for proliferation and stemness of proneural GSCs, while it appears not to be relevant in mesenchymal GSCs under basal conditions. However, when challenged with a fractionated protocol of radiation therapy, comparable to that used in the clinical setting, mesenchymal GSCs were dependent on integrin a6 for survival. Specifically, GSCs with reduced levels of ITGA6 displayed a clear reduction of DNA damage response and perturbation of cell cycle pathways. These data indicate that ITGA6 inhibition is able to overcome the radioresistance of mesenchymal GSCs, while it reduces proliferation and stemness in proneural GSCs. Therefore, integrin a6 controls crucial characteristics across GBM subtypes in GBM heterogeneous biology and thus may represent a promising target to improve patient outcomes.

Niclosamide exerts anticancer effects through inhibition of the FOXM1-mediated DNA damage response in prostate cancer

Niclosamide, an established anti-helminthic drug, has anticancer activity against various cancers including prostate cancer, but the underlying mechanisms have not yet been defined. We demonstrated the anticancer effects of niclosamide in castration-resistant prostate cancer (CRPC) cells, and elucidated the mechanism of action of niclosamide in CRPC. Niclosamide reduced cell proliferation and induced apoptosis of CRPC cells in vitro, and also reduced xenograft tumor growth in vivo. Niclosamide significantly increased the number of γH2AX- and 53BP1-positive cells. In RNA-sequencing, niclosamide induced extensive changes in gene expression including cell division, DNA replication, and DNA repair. Bioinformatics analysis using TCGA data set revealed that FOXM1 is an important target of niclosamide. In microarray assays, FOXM1 knockdown significantly inhibited several genes involved in DNA repair, and homologous recombination, in particular. Finally, FOXM1 strongly bound to EXO1 in CRPC cells, and FOXM1 knockdown significantly reduced EXO1-driven luciferase activity. Taken together, our results suggest that niclosamide exerts anticancer activity through inhibition of the FOXM1-mediated DNA damage response in CRPC.

Regulation of RAD51 at the Transcriptional and Functional Levels: What Prospects for Cancer Therapy?

The RAD51 recombinase is a critical effector of Homologous Recombination (HR), which is an essential DNA repair mechanism for double-strand breaks. The RAD51 protein is recruited onto the DNA break by BRCA2 and forms homopolymeric filaments that invade the homologous chromatid and use it as a template for repair. RAD51 filaments are detectable by immunofluorescence as distinct foci in the cell nucleus, and their presence is a read out of HR proficiency. RAD51 is an essential gene, protecting cells from genetic instability. Its expression is low and tightly regulated in normal cells and, contrastingly, elevated in a large fraction of cancers, where its level of expression and activity have been linked with sensitivity to genotoxic treatment. In particular, BRCA-deficient tumors show reduced or obliterated RAD51 foci formation and increased sensitivity to platinum salt or PARP inhibitors. However, resistance to treatment sets in rapidly and is frequently based on a complete or partial restoration of RAD51 foci formation. Consequently, RAD51 could be a highly valuable therapeutic target. Here, we review the multiple levels of regulation that impact the transcription of the RAD51 gene, as well as the post-translational modifications that determine its expression level, recruitment on DNA damage sites and the efficient formation of homofilaments. Some of these regulation levels may be targeted and their impact on cancer cell survival discussed.

BKM120 sensitizes BRCA-proficient triple negative breast cancer cells to olaparib through regulating FOXM1 and Exo1 expression

Poly (ADP-ribose) polymerase (PARP) inhibitors offer a significant clinical benefit for triple-negative breast cancers (TNBCs) with BRCA1/2 mutation. However, the narrow clinical indication limits the development of PARP inhibitors. Phosphoinositide 3-kinase (PI3K) inhibition sensitizes BRCA-proficient TNBC to PARP inhibition, which broadens the indication of PARP inhibitors. Previously researches have reported that PI3K inhibition induced the defect of homologous recombination (HR) mediated repair by downregulating the expression of BRCA1/2 and Rad51. However, the mechanism for their synergistic effects in the treatment of TNBC is still unclear. Herein, we focused on DNA damage, DNA single-strand breaks (SSBs) repair and DNA double-strand breaks (DSBs) repair three aspects to investigate the mechanism of dual PI3K and PARP inhibition in DNA damage response. We found that dual PI3K and PARP inhibition with BKM120 and olaparib significantly reduced the proliferation of BRCA-proficient TNBC cell lines MDA-MB-231 and MDA231-LM2. BKM120 increased cellular ROS to cause DNA oxidative damage. Olaparib resulted in concomitant gain of PARP1, forkhead box M1 (FOXM1) and Exonuclease 1 (Exo1) while inhibited the activity of PARP. BKM120 downregulated the expression of PARP1 and PARP2 to assist olaparib in blocking PARP mediated repair of DNA SSBs. Meanwhile, BKM120 inhibited the expression of BRAC1/2 and Rad51/52 to block HR mediated repair through the PI3K/Akt/NFκB/c-Myc signaling pathway and PI3K/Akt/ FOXM1/Exo1 signaling pathway. BKM120 induced HR deficiency expanded the application of olaparib to HR proficient TNBCs. Our findings proved that PI3K inhibition impaired the repair of both DNA SSBs and DNA DSBs. FOXM1 and Exo1 are novel therapeutic targets that serves important roles in DNA damage response.

FOXM1 Inhibition in Ovarian Cancer Tissue Cultures Affects Individual Treatment Susceptibility Ex Vivo

Simple Summary

Late diagnosis of ovarian cancer is a major reason for the high mortality rate of this tumor entity. The time to determine tumor susceptibility to treatment is scarce and resistance to therapy occurs very frequently. Here, we aim for a model system that can determine tumor response to (I) study novel drugs and (II) enhance patient stratification. Tissue specimens (n = 10) were acquired from fresh surgical samples. Tissue cultures were cultivated and treated with clinically relevant therapeutics and an FOXM1 inhibitor for 3–6 days. The transcription factor FOXM1 is a key regulator of tumor survival affecting multiple cancerogenic target genes. Gene expression of FOXM1 and its targets BRCA1/2 and RAD51 were investigated together with tumor susceptibility. Tissue cultures successfully demonstrated the individual benefit of FOXM1 inhibition and revealed the potency of the complex model system for oncological research.

Abstract

Diagnosis in an advanced state is a major hallmark of ovarian cancer and recurrence after first line treatment is common. With upcoming novel therapies, tumor markers that support patient stratification are urgently needed to prevent ineffective therapy. Therefore, the transcription factor FOXM1 is a promising target in ovarian cancer as it is frequently overexpressed and associated with poor prognosis. In this study, fresh tissue specimens of 10 ovarian cancers were collected to investigate tissue cultures in their ability to predict individual treatment susceptibility and to identify the benefit of FOXM1 inhibition. FOXM1 inhibition was induced by thiostrepton (3 µM). Carboplatin (0.2, 2 and 20 µM) and olaparib (10 µM) were applied and tumor susceptibility was analyzed by tumor cell proliferation and apoptosis in immunofluorescence microscopy. Resistance mechanisms were investigated by determining the gene expression of FOXM1 and its targets BRCA1/2 and RAD51. Ovarian cancer tissue was successfully maintained for up to 14 days ex vivo, preserving morphological characteristics of the native specimen. Thiostrepton downregulated FOXM1 expression in tissue culture. Individual responses were observed after combined treatment with carboplatin or olaparib. Thus, we successfully implemented a complex tissue culture model to ovarian cancer and showed potential benefit of combined FOXM1 inhibition.

Mistletoe Extract Targets the STAT3-FOXM1 Pathway to Induce Apoptosis and Inhibits Metastasis in Breast Cancer Cells

Mistletoe extracts (Viscum album L.) have been widely used as complementary and alternative medicines for the treatment of cancer, and their cytotoxic effects have been reported on various types of cancer. However, the molecular targets of mistletoe extracts have not been well studied. Herein, we investigated molecules associated with the in vitro and in vivo anticancer effects of mistletoe extract using 4T1 murine breast cancer cells. Mistletoe extract induced apoptosis and inhibited the signal transducer and activator of transcription3 (STAT3) phosphorylation. This inhibition was accompanied by the downregulations of forkhead box M1 (FOXM1) and the DNA repair proteins, RAD51 and survivin. Mistletoe extract simultaneously increased the expression of the DNA damage marker proteins, phosphorylated H2A histone family member X (H2A.X), and phosphorylated p38. Furthermore, mistletoe extract effectively suppressed tumor growth in 4T1 tumor-bearing BALB/c mice. In addition to tumor growth inhibition, mistletoe extract inhibited lung metastasis in the tumor-bearing mice and cell invasiveness by downregulating the expressions of matrix metalloproteinases (MMPs), urokinase-type plasminogen activator (uPA), uPA receptor, and markers of epithelial-mesenchymal transition (snail and fibronectin). Taken together, our results suggest that mistletoe extract targets the STAT3-FOXM1 pathway for its cytotoxic effects, and that mistletoe extracts might be useful for the treatment of patients with cancers highly expressing the STAT3-FOXM1 pathway.

Replication stress and FOXM1 drive radiation induced genomic instability and cell transformation

In contrast to the vast majority of research that has focused on the immediate effects of ionizing radiation, this work concentrates on the molecular mechanism driving delayed effects that emerge in the progeny of the exposed cells. We employed functional protein arrays to identify molecular changes induced in a human bronchial epithelial cell line (HBEC3-KT) and osteosarcoma cell line (U2OS) and evaluated their impact on outcomes associated with radiation induced genomic instability (RIGI) at day 5 and 7 post-exposure to a 2Gy X-ray dose, which revealed replication stress in the context of increased FOXM1b expression. Irradiated cells had reduced DNA replication rate detected by the DNA fiber assay and increased DNA resection detected by RPA foci and phosphorylation. Irradiated cells increased utilization of homologous recombination-dependent repair detected by a gene conversion assay and DNA damage at mitosis reflected by RPA positive chromosomal bridges, micronuclei formation and 53BP1 positive bodies in G1, all known outcomes of replication stress. Interference with the function of FOXM1, a transcription factor widely expressed in cancer, employing an aptamer, decreased radiation-induced micronuclei formation and cell transformation while plasmid-driven overexpression of FOXM1b was sufficient to induce replication stress, micronuclei formation and cell transformation.

The forkhead box M1 (FOXM1) expression and antitumor effect of FOXM1 inhibition in malignant rhabdoid tumor

PURPOSE

Malignant rhabdoid tumor (MRT) is a rare, highly aggressive sarcoma with an uncertain cell of origin. Despite the existing standard of intensive multimodal therapy, the prognosis of patients with MRT is very poor. Novel antitumor agents are needed for MRT patients. Forkhead box transcription factor 1 (FOXM1) is overexpressed and is correlated with the pathogenesis in several human malignancies. In this study, we identified the clinicopathological and prognostic values of the expression of FOXM1 and its roles in the progression of MRT.

METHODS

We investigated the FOXM1 expression levels and their clinical significance in 23 MRT specimens using immunohistochemistry and performed clinicopathologic and prognostic analyses. We also demonstrated correlations between the downregulation of FOXM1 and oncological characteristics using small interfering RNA (siRNA) and FOXM1 inhibitor in MRT cell lines.

RESULTS

Histopathological analyses revealed that primary renal MRTs showed significantly low FOXM1 protein expression levels (p = 0.032); however, there were no significant differences in other clinicopathological characteristics or the survival rate. FOXM1 siRNA and FOXM1 inhibitor (thiostrepton) successfully downregulated the mRNA and protein expression of FOXM1 in vitro and the downregulation of FOXM1 inhibited cell proliferation, drug resistance to chemotherapeutic agents, migration, invasion, and caused the cell cycle arrest and apoptosis of MRT cell lines. A cDNA microarray analysis showed that FOXM1 regulated FANCD2 and NBS1, which are key genes for DNA damage repair.

CONCLUSION

This study demonstrates that FOXM1 may serve as a promising therapeutic target for MRT.

Genetic variants and cognitive functions in patients with brain tumors

BACKGROUND

Patients with brain tumors treated with radiotherapy (RT) and chemotherapy (CT) often experience cognitive dysfunction. We reported that single nucleotide polymorphisms (SNPs) in the APOE, COMT, and BDNF genes may influence cognition in brain tumor patients. In this study, we assessed whether genes associated with late-onset Alzheimer's disease (LOAD), inflammation, cholesterol transport, dopamine and myelin regulation, and DNA repair may influence cognitive outcome in this population.

METHODS

One hundred and fifty brain tumor patients treated with RT ± CT or CT alone completed a neurocognitive assessment and provided a blood sample for genotyping. We genotyped genes/SNPs in these pathways: (i) LOAD risk/inflammation/cholesterol transport, (ii) dopamine regulation, (iii) myelin regulation, (iv) DNA repair, (v) blood-brain barrier disruption, (vi) cell cycle regulation, and (vii) response to oxidative stress. White matter (WM) abnormalities were rated on brain MRIs.

RESULTS

Multivariable linear regression analysis with Bayesian shrinkage estimation of SNP effects, adjusting for relevant demographic, disease, and treatment variables, indicated strong associations (posterior association summary [PAS] ≥ 0.95) among tests of attention, executive functions, and memory and 33 SNPs in genes involved in: LOAD/inflammation/cholesterol transport (eg, PDE7A, IL-6), dopamine regulation (eg, DRD1, COMT), myelin repair (eg, TCF4), DNA repair (eg, RAD51), cell cycle regulation (eg, SESN1), and response to oxidative stress (eg, GSTP1). The SNPs were not significantly associated with WM abnormalities.

CONCLUSION

This novel study suggests that polymorphisms in genes involved in aging and inflammation, dopamine, myelin and cell cycle regulation, and DNA repair and response to oxidative stress may be associated with cognitive outcome in patients with brain tumors.

Aberrant ASPM expression mediated by transcriptional regulation of FoxM1 promotes the progression of gliomas

Gliomas are the most common form of malignant tumour in the central nervous system. However, the molecular mechanism of the tumorigenesis and progression of gliomas remains unclear. In this study, we used the GEO database to identify genes differentially expressed in gliomas and predict the prognosis of glioma. We observed that ASPM mRNA was increased obviously in glioma tissue, and higher ASPM mRNA expression predicted worse disease prognosis. ASPM was highly expressed in glioma cell lines U87‐MG and U251, and knockdown of ASPM expression in these cells significantly repressed the proliferation, migration and invasion ability and induced G0/G1 phase arrest. In addition, down‐regulation of ASPM suppressed the growth of glioma in nude mice. Five potential binding sites for transcription factor FoxM1 were predicted in the ASPM promoter. FoxM1 overexpression significantly increased the expression of ASPM and promoted the proliferation and migration of glioma cells, which was abolished by ASPM ablation. ChIP and dual‐luciferase reporter analysis confirmed that FoxM1 bound to the ASPM promoter at −236 to ‐230 bp and −1354 to ‐1348 bp and activated the transcription of ASPM directly. Collectively, our results demonstrated for the first time that aberrant ASPM expression mediated by transcriptional regulation of FoxM1 promotes the malignant properties of glioma cells.

Genomic analyses of early responses to radiation inglioblastoma reveal new alterations at transcription,splicing, and translation levels

High-dose radiation is the main component of glioblastoma therapy. Unfortunately, radio-resistance is a common problem and a major contributor to tumor relapse. Understanding the molecular mechanisms driving response to radiation is critical for identifying regulatory routes that could be targeted to improve treatment response. We conducted an integrated analysis in the U251 and U343 glioblastoma cell lines to map early alterations in the expression of genes at three levels: transcription, splicing, and translation in response to ionizing radiation. Changes at the transcriptional level were the most prevalent response. Downregulated genes are strongly associated with cell cycle and DNA replication and linked to a coordinated module of expression. Alterations in this group are likely driven by decreased expression of the transcription factor FOXM1 and members of the E2F family. Genes involved in RNA regulatory mechanisms were affected at the mRNA, splicing, and translation levels, highlighting their importance in radiation-response. We identified a number of oncogenic factors, with an increased expression upon radiation exposure, including BCL6, RRM2B, IDO1, FTH1, APIP, and LRIG2 and lncRNAs NEAT1 and FTX. Several of these targets have been previously implicated in radio-resistance. Therefore, antagonizing their effects post-radiation could increase therapeutic efficacy. Our integrated analysis provides a comprehensive view of early response to radiation in glioblastoma. We identify new biological processes involved in altered expression of various oncogenic factors and suggest new target options to increase radiation sensitivity and prevent relapse.

Interferon regulatory factor-1 suppresses DNA damage response and reverses chemotherapy resistance by downregulating the expression of RAD51 in gastric cancer

Recent studies have shown that IRF-1 plays a significant role in various tumour-induced chemoresistance, but its role and mechanism in gastric cancer-associated chemoresistance are not clear. Our study showed that IRF-1 expression could reverse gastric cancer-related chemoresistance. Dysregulated DNA repair is an important cause of chemoresistance. We established a chemoresistant gastric cancer cell line and found that drug-resistant gastric cancer cells had increased DNA repair ability and that IRF-1 regulated DNA damage repair. Further studies showed that IRF-1 inhibited the expression of RAD51 directly by binding to the RAD51 promoter to affect DNA damage repair; this binding reversed resistance. However, restoring the expression of RAD51 halted the inhibitory effect of IRF-1 partially. Also, we revealed that the overexpression of IRF-1 in a mouse model synergized with chemotherapeutic drugs to inhibit tumour growth. Finally, IRF-1 expression correlated with RAD51 expression in gastric cancer specimens. The expression of IRF-1 and RAD51 are both related to the survival duration of patients with gastric cancer. These results suggest that targeting IRF-1-RAD51 could be an effective approach to reversing multidrug resistance in gastric cancer.

Bortezomib inhibits growth and sensitizes glioma to temozolomide (TMZ) via down-regulating the FOXM1-Survivin axis

Background

High-grade glioma (HGG) is a fatal human cancer. Bortezomib, a proteasome inhibitor, has been approved for the treatment of multiple myeloma but its use in glioma awaits further investigation. This study aimed to explore the chemotherapeutic effect and the underlying mechanism of bortezomib on gliomas.

Methods

U251 and U87 cell viability and proliferation were detected by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay, tumor cell spheroid growth, and colony formation assay. Cell apoptosis and cell cycle were detected by flow cytometry. Temozolomide (TMZ)-insensitive cell lines were induced by long-term TMZ treatment, and cells with stem cell characteristics were enriched with stem cell culture medium. The mRNA levels of interested genes were measured via reverse transcription-quantitative polymerase chain reaction, and protein levels were determined via Western blotting/immunofluorescent staining in cell lines and immunohistochemical staining in paraffin-embedded sections. Via inoculating U87 cells subcutaneously, glioma xenograft models in nude mice were established for drug experiments. Patient survival data were analyzed using the Kaplan–Meier method.

Results

Bortezomib inhibited the viability and proliferation of U251 and U87 cells in a dose- and time-dependent manner by inducing apoptosis and cell cycle arrest. Bortezomib also significantly inhibited the spheroid growth, colony formation, and stem-like cell proliferation of U251 and U87 cells. When administrated in combination, bortezomib showed synergistic effect with TMZ in vitro and sensitized glioma to TMZ treatment both in vitro and in vivo. Bortezomib reduced both the mRNA and protein levels of Forkhead Box M1 (FOXM1) and its target gene Survivin. The FOXM1–Survivin axis was markedly up-regulated in established TMZ-insensitive glioma cell lines and HGG patients. Expression levels of FOXM1 and Survivin were positively correlated with each other and both related to poor prognosis in glioma patients.

Conclusions

Bortezomib was found to inhibit glioma growth and improved TMZ chemotherapy efficacy, probably via down-regulating the FOXM1–Survivin axis. Bortezomib might be a promising agent for treating malignant glioma, alone or in combination with TMZ.

DNA Repair Protein Rad51 Induces Tumor Growth and Metastasis in Esophageal Squamous Cell Carcinoma via a p38/Akt-Dependent Pathway

BACKGROUND

Rad51 is a protein which plays a vital role in DNA double-strand break repair and maintenance of telomeres. However, the underlying mechanism for its action in esophageal squamous cell carcinoma (ESCC) remains unclear.

PATIENTS AND METHODS

Eighty-seven patients with ESCC were enrolled in this study. Expression of Rad51 in ESCC was determined by immunohistochemistry and correlated with clinicopathological variables by Chi square test. The role of Rad51 in patient survival was determined by Kaplan-Meier estimates. The effects of Rad51 knockdown and overexpression on esophageal cancer growth, migration, and invasion were examined using TE8, CE81T, and KYSE70 cells. The mechanisms involved were also analyzed. Nude mice models were used for assessment of tumor growth.

RESULTS

Rad51 staining was predominantly observed in ESCC patients. ESCC patients with high Rad51 expression had significantly decreased survival (P < 0.001) combined with increased tumor size (P = 0.034) and lymph node metastasis (P = 0.039). Rad51 overexpression promoted, while its knockdown attenuated, esophageal cancer cell viability through cell cycle entry and migration/invasion via epithelial-mesenchymal transition. Moreover, Rad51 overexpression increased colony formation in vitro and tumor growth in vivo. In addition, high Rad51 expression increased cancer progression through the p38/Akt/Snail signaling pathway.

CONCLUSIONS

This study indicates a new biological role for Rad51 in ESCC progression. Rad51 may serve as a potential prognostic biomarker and therapeutic target for ESCC patients.

BRCA1 identified as a modulator of temozolomide resistance in P53 wild-type GBM using a high-throughput shRNA-based synthetic lethality screening

Glioblastoma multiforme (GBM), the most common type of primary brain tumor, is universally fatal, with a median survival duration ranging from 12-15 months despite maximum treatment efforts. Temozolomide (TMZ) is the current standard of care for GBM patients; however patients usually develop resistance to TMZ and limits its benefit. The identification of novel synergistic targets in GBM will lead to the development of new targeted drugs, which could be combined with broad-spectrum cytotoxic agents. In this study, we used a high-throughput synthetic lethality screen with a pooled short hairpin DNA repair library, in combination with TMZ, to identify targets that will enhance TMZ-induced antitumor effects. Using an unbiased bioinformatical analysis, we identified BRCA1 as a potential promising candidate gene that induced synthetic lethality with TMZ in glioma sphere-forming cells (GSCs). BRCA1 knockdown resulted in antitumor activity with TMZ in P53 wild-type GSCs but not in P53 mutant GSCs. TMZ treatment induced a DNA damage repair response; the activation of BRCA1 DNA repair pathway targets and knockdown of BRCA1, together with TMZ, led to increased DNA damage and cell death in P53 wild-type GSCs. Our study identified BRCA1 as a potential target that sensitizes TMZ-induced cell death in P53 wild-type GBM, suggesting that the combined inhibition of BRCA1 and TMZ treatment will be a successful targeted therapy for GBM patients.

PRRX1 isoforms cooperate with FOXM1 to regulate the DNA damage response in pancreatic cancer cells

PRRX1 is a homeodomain transcriptional factor, which has two isoforms, PRXX1A and PRRX1B. The PRRX1 isoforms have been demonstrated to be important in pancreatic cancer, especially in the regulation of epithelial-to-mesenchymal transition (EMT) in Pancreatic Ductal Adenocarcinoma (PDAC) and of mesenchymal-to-epithelial transition (MET) in liver metastasis. In order to determine the functional underpinnings of PRRX1 and its isoforms, we have unraveled a new interplay between PRRX1 and the FOXM1 transcriptional factors. Our detailed biochemical analysis reveals the direct physical interaction between PRRX1 and FOXM1 proteins that requires the PRRX1A/B 200-222/217 amino acid (aa) region and the FOXM1 Forkhead domain. Additionally, we demonstrate the cooperation between PRRX1 and FOXM1 in the regulation of FOXM1-dependent transcriptional activity. Moreover, we establish FOXM1 as a critical downstream target of PRRX1 in pancreatic cancer cells. We demonstrate a novel role for PRRX1 in the regulation of genes involved in DNA repair pathways. Indeed, we show that expression of PRRX1 isoforms may limit the induction of DNA damage in pancreatic cancer cells. Finally, we demonstrate that targeting FOXM1 with the small molecule inhibitor FDI6 suppress pancreatic cancer cell proliferation and induces their apoptotic cell death. FDI6 sensitizes pancreatic cancer cells to Etoposide and Gemcitabine induced apoptosis. Our data provide new insights into PRRX1's involvement in regulating DNA damage and provide evidence of a possible PRRX1-FOXM1 axis that is critical for PDAC cells.

The tumor suppressor FOXO3a mediates the response to EGFR inhibition in glioblastoma cells

PURPOSE

Although EGFR activation is a hallmark of glioblastoma (GBM), anti-EGFR therapy has so far not yielded the desired effects. Targeting PI3K/Akt has been proposed as a strategy to increase the cellular sensitivity to EGFR inhibitors. Here we evaluated the contribution of FOXO3a, a key Akt target, in the response of GBM cells to EGFR inhibition.

METHODS

FOXO3a activation was assessed by immunofluorescence and gene reporter assays, and by evaluating target gene expression using Western blotting and qRT-PCR. Cellular effects were evaluated using cell viability and apoptosis assays, i.e., Annexin V/PI staining and caspase 3/7 activity measurements. Drug synergism was evaluated by performing isobolographic analyses. Gene silencing experiments were performed using stable shRNA transfections.

RESULTS

We found that EGFR inhibition in GBM cells led to FOXO3a activation and to transcriptional modulation of its key targets, including repression of the oncogene FOXM1. In addition, we found that specific FOXO3a activation recapitulated the molecular effects of EGFR inhibition, and that the FOXO3a activator trifluoperazine, a FDA-approved antipsychotic agent, reduced GBM cell growth. Subsequent isobolographic analyses of combination experiments indicated that trifluoperazine and erlotinib cooperated synergistically and that their concomitant treatment induced a robust activation of FOXO3a, leading to apoptosis in GBM cells. Using gene silencing, we found that FOXO3a is essential for the response of GBM cells to EGFR inhibition.

CONCLUSIONS

Our data indicate that FOXO3a activation is a crucial event in the response of GBM cells to EGFR inhibition, suggesting that FOXO3a may serve as an actionable therapeutic target that can be modulated using FDA-approved drugs.

STAT1-mediated inhibition of FOXM1 enhances gemcitabine sensitivity in pancreatic cancer

Forkhead box protein M1 (FOXM1) was identified as an oncogenic transcription factor and master regulator of tumor progression and metastasis. FOXM1 expression often correlates with poor prognosis and chemotherapy resistance. In the present study, we investigated the association of FOXM1 expression and chemoresistance in pancreatic cancer. Elevated FOXM1 protein levels were associated with gemcitabine chemoresistance in patients with pancreatic cancer. In gemcitabine resistance cell line models of pancreatic cancer, FOXM1 expression increased, which induced gemcitabine chemoresistance in vitro. In pancreatic cancer cells treated with gemcitabine, FOXM1 affected nuclear factor κB (NF-κB) signaling activity. Immunohistochemical analysis demonstrated a negative association of FOXM1 expression and the level of phosphorylated signal transducer and activator of transcription 1 (pSTAT1) in human pancreatic cancer tissues. Dual-luciferase reporter assays and chromatin-immunoprecipitation assays demonstrated that pSTAT1 directly binds to the FOXM1 promoter to down-regulate its transcription. Interferon γ (IFNγ) promoted gemcitabine-induced cell apoptosis and inhibited cell proliferation in vitro and in vivo by FOXM1 inhibition. These data suggested that FOXM1 enhances chemoresistance to gemcitabine in pancreatic cancer. IFNγ could be used to down-regulate the expression of FOXM1 through STAT1 phosphorylation, thereby increasing the sensitivity of pancreatic cancer cells to gemcitabine. These studies suggested the sensitization by IFNγ in pancreatic ductal adenocarcinoma (PDAC) chemotherapy, which requires further clinical studies.

High FOXM1 expression is a prognostic marker for poor clinical outcomes in prostate cancer

Purpose: We aimed to investigate the expression of FOXM1 and to determine the relationships between FOXM1 expression and clinicopathologic characteristics in patients with PCa. Furthermore, we reconfirmed the prognostic impact of FOXM1 in different cohorts using already published data. Patients and Methods: Formalin-fixed, paraffin-embedded tissues were collected from patients with low- (n=17), intermediate- (n=36), and high-risk (n=29) disease, from patients with CRPC (n=2) and from patients with BPH (n=28). To analyze FOXM1 expression, we performed IHC analyses. Also, we analyzed gene expression data from cBioPortal to evaluate the associations between FOXM1 alteration and prognosis of PCa. Results: FOXM1 expression measured using Allred score differed between patients with BPH, and low-, intermediate-, and high-risk PCa (0.3, 1.5, 4.8, and 6.2, respectively; p<0.001). Patients with high FOXM1 expression had higher preoperative PSA levels (p=0.023), more advanced tumor stages (p=0.047), and higher pathologic Gleason score (p<0.001) than those with low FOXM1 expression. ROC curve analysis indicated that FOXM1 expression was a useful marker for discriminating PCa from BPH (AUC 0.851, 95% CI 0.783-0.920) and for discriminating high-risk PCa from low- and intermediate-risk PCa (AUC 0.807, 95% CI 0.719-0.894). In multivariate analyses, high FOXM1 expression was an independent predictor of BCR. Finally, in the TCGA dataset, FOXM1 alteration was associated with poor overall (p=4.521e-4) and disease-free survival (p=0.0108). Conclusions: In patients with PCa, high FOXM1 expression was associated with advanced tumor stages, high Gleason score, and poor prognosis. These data suggest a role of FOXM1 in biologically and clinically aggressive PCa.

Mesenchymal glioblastoma constitutes a major ceRNA signature in the TGF-β pathway

Rationale: Competitive endogenous RNA (ceRNA) networks play important roles in posttranscriptional regulation. Their dysregulation is common in cancer. However, ceRNA signatures have been poorly examined in the invasive and aggressive phenotypes of mesenchymal glioblastoma (GBM). This study aims to characterize mesenchymal glioblastoma at the mRNA-miRNA level and identify the mRNAs in ceRNA networks (micNET) markers and their mechanisms in tumorigenesis. Methods: The mRNAs in ceRNA networks (micNETs) of glioblastoma were investigated by constructing a GBM ceRNA network followed by integration with a STRING protein interaction network. The prognostic micNET markers of mesenchymal GBM were identified and validated across multiple datasets. ceRNA interactions were identified between micNETs and miR181 family members. LY2109761, an inhibitor of TGFBR2, demonstrated tumor-suppressive effects on both primary cultured cells and a patient-derived xenograft intracranial model. Results: We characterized mesenchymal glioblastoma at the mRNA-miRNA level and reported a ceRNA network that could separate the mesenchymal subtype from other subtypes. Six genes (TGFBR2, RUNX1, PPARG, ACSL1, GIT2 and RAP1B) that interacted with each other in both a ceRNA-related manner and in terms of their protein functions were identified as markers of the mesenchymal subtype. The coding sequence (CDS) and 3'-untranslated region (UTR) of TGFBR2 upregulated the expression of these genes, whereas TGFBR2 inhibition by siRNA or miR-181a/d suppressed their expression levels. Furthermore, mesenchymal subtype-related genes and the invasion phenotype could be reversed by suppressing the six mesenchymal marker genes. Conclusions: This study suggests that the micNETs may have translational significance in the diagnosis of mesenchymal GBM and may be novel therapeutic targets.

Principled multi-omic analysis reveals gene regulatory mechanisms of phenotype variation

Recent studies have analyzed large-scale data sets of gene expression to identify genes associated with interindividual variation in phenotypes ranging from cancer subtypes to drug sensitivity, promising new avenues of research in personalized medicine. However, gene expression data alone is limited in its ability to reveal cis-regulatory mechanisms underlying phenotypic differences. In this study, we develop a new probabilistic model, called pGENMi, that integrates multi-omic data to investigate the transcriptional regulatory mechanisms underlying interindividual variation of a specific phenotype—that of cell line response to cytotoxic treatment. In particular, pGENMi simultaneously analyzes genotype, DNA methylation, gene expression, and transcription factor (TF)-DNA binding data, along with phenotypic measurements, to identify TFs regulating the phenotype. It does so by combining statistical information about expression quantitative trait loci (eQTLs) and expression-correlated methylation marks (eQTMs) located within TF binding sites, as well as observed correlations between gene expression and phenotype variation. Application of pGENMi to data from a panel of lymphoblastoid cell lines treated with 24 drugs, in conjunction with ENCODE TF ChIP data, yielded a number of known as well as novel (TF, Drug) associations. Experimental validations by TF knockdown confirmed 41% of the predicted and tested associations, compared to a 12% confirmation rate of tested nonassociations (controls). An extensive literature survey also corroborated 62% of the predicted associations above a stringent threshold. Moreover, associations predicted only when combining eQTL and eQTM data showed higher precision compared to an eQTL-only or eQTM-only analysis using pGENMi, further demonstrating the value of multi-omic integrative analysis.

Olaparib-induced Adaptive Response Is Disrupted by FOXM1 Targeting that Enhances Sensitivity to PARP Inhibition

FOXM1 transcription factor network is activated in over 84% of cases in high-grade serous ovarian cancer (HGSOC), and FOXM1 upregulates the expression of genes involved in the homologous recombination (HR) DNA damage and repair (DDR) pathway. However, the role of FOXM1 in PARP inhibitor response has not yet been studied. This study demonstrates that PARP inhibitor (PARPi), olaparib, induces the expression and nuclear localization of FOXM1. On the basis of ChIP-qPCR, olaparib enhances the binding of FOXM1 to genes involved in HR repair. FOXM1 knockdown by RNAi or inhibition by thiostrepton decreases FOXM1 expression, decreases the expression of HR repair genes, such as BRCA1 and RAD51, and enhances sensitivity to olaparib. Comet and PARP trapping assays revealed increases in DNA damage and PARP trapping in FOXM1-inhibited cells treated with olaparib. Finally, thiostrepton decreases the expression of BRCA1 in rucaparib-resistant cells and enhances sensitivity to rucaparib. Collectively, these results identify that FOXM1 plays an important role in the adaptive response induced by olaparib and FOXM1 inhibition by thiostrepton induces "BRCAness" and enhances sensitivity to PARP inhibitors.Implications: FOXM1 inhibition represents an effective strategy to overcome resistance to PARPi, and targeting FOXM1-mediated adaptive pathways may produce better therapeutic effects for PARP inhibitors. Mol Cancer Res; 16(6); 961-73. ©2018 AACR.

FOXM1 and STAT3 interaction confers radioresistance in glioblastoma cells

Glioblastoma multiforme (GBM) continues to be the most frequently diagnosed and lethal primary brain tumor. Adjuvant chemo-radiotherapy remains the standard of care following surgical resection. In this study, using reverse phase protein arrays (RPPAs), we assessed the biological effects of radiation on signaling pathways to identify potential radiosensitizing molecular targets. We identified subsets of proteins with clearly concordant/discordant behavior between irradiated and non-irradiated GBM cells in vitro and in vivo. Moreover, we observed high expression of Forkhead box protein M1 (FOXM1) in irradiated GBM cells both in vitro and in vivo. Recent evidence of FOXM1 as a master regulator of metastasis and its important role in maintaining neural, progenitor, and GBM stem cells, intrigued us to validate it as a radiosensitizing target. Here we show that FOXM1 inhibition radiosensitizes GBM cells by abrogating genes associated with cell cycle progression and DNA repair, suggesting its role in cellular response to radiation. Further, we demonstrate that radiation induced stimulation of FOXM1 expression is dependent on STAT3 activation. Co-immunoprecipitation and co-localization assays revealed physical interaction of FOXM1 with phosphorylated STAT3 under radiation treatment. In conclusion, we hypothesize that FOXM1 regulates radioresistance via STAT3 in GBM cells. We also, show GBM patients with high FOXM1 expression have poor prognosis. Collectively our observations might open novel opportunities for targeting FOXM1 for effective GBM therapy.

ER stress in temozolomide-treated glioblastomas interferes with DNA repair and induces apoptosis

Glioblastoma multiforme (GBM) is a deadly grade IV brain tumor. Radiation in combination with temozolomide (TMZ), the current chemotherapeutic for GBMs, only provides 12–14 months survival post diagnosis. Because GBMs are dependent on both activation of the DNA damage pathway and the endoplasmic reticulum (ER) stress response, we asked if a novel ER stress inducing agent, JLK1486, increases the efficacy of TMZ.

We found that the combination of TMZ+JLK1486 resulted in decreased proliferation in a panel of adherent GBM cells lines and reduced secondary sphere formation in non-adherent and primary lines. Decreased proliferation correlated with increased cell death due to apoptosis. We found prolonged ER stress in TMZ+JLK1486 treated cells that resulted in sustained activation of the unfolded protein response (UPR) through increased levels of BiP, ATF4, and CHOP. In addition, TMZ+JLK1486 treatment caused decreased RAD51 levels, impairing DNA damage repair. Furthermore, we found delayed time to tumor doubling in TMZ+JLK1486 treated mice.

Our data shows that the addition of JLK1486 to TMZ increases the efficaciousness of the treatment by decreasing proliferation and inducing cell death. We propose increased cell death is due to two factors. One, prolonged ER stress driving the expression of the pro-apoptotic transcription factor CHOP, and, second, unresolved DNA double strand breaks, due to decreased RAD51 levels. The combination of TMZ+JLK1486 is a potential novel therapeutic combination and suggests an inverse relationship between unresolved ER stress and the DNA damage response pathway.