Inhibition of DNA-repair genes Ercc1 and Mgmt enhances temozolomide efficacy in gliomas treatment: a pre-clinical study

Glioma-astrocyte connexin43 confers temozolomide resistance through activation of the E2F1/ERCC1 axis

BACKGROUND

Glioma is the most prevalent and lethal tumor of the central nervous system. Routine treatment with temozolomide (TMZ) would unfortunately result in inevitable recurrence and therapy resistance, severely limiting therapeutic efficacy. Tumor-associated astrocytes (TAAs) are key components of the tumor microenvironment and increasing evidence has demonstrated that aberrant expression of connexin43 (Cx43) was closely associated with glioma progression and TMZ resistance. However, the specific role of Cx43 in mediating TMZ resistance through glioma and astrocyte interactions has not been fully explored.

METHODS

The expression and prognostic value of Cx43 were evaluated in tumor samples and clinical databases. ShRNA-medicated knockdown and Gfap-Cre Cx43flox/flox gene mouse were used to assess the role and functional significance of Cx43 in vitro and in vivo. Moreover, we performed mass spectrometry analysis, chromatin immunoprecipitation, and other biochemical assays to define the molecular mechanisms by which Cx43 promotes TMZ resistance.

RESULTS

We confirmed that the upregulation of Cx43 expression between TAAs and glioma cells contributed to TMZ resistance and tumor recurrence. Genetic knockdown or pharmacological inhibition of Cx43 enhanced TMZ-induced cytotoxicity. Mechanistically, elevated Cx43 expression induced β-catenin accumulation at the cell surface of glioma cells, suppressing T-cell factor/lymphoid enhancer-binding factor transcription. This led to impaired miR-205-5p expression and subsequent activation of the E2F1/ERCC1 axis, which eventually led to chemoresistance.

CONCLUSIONS

Our study reveals a novel regulatory mechanism in which the Cx43/miR-205-5p/E2F1/ERCC1 axis contributes to TMZ resistance in glioma. These findings further highlight the potential of targeting Cx43 as a therapeutic strategy in glioma.

Functional germline variants in DNA damage repair pathways are associated with altered survival in adults with glioma treated with temozolomide

Background

Temozolomide (TMZ) treatment has demonstrated, but variable, impact on glioma prognosis. This study examines associations of survival with DNA repair gene germline polymorphisms among glioma patients who did and did not have TMZ treatment. Identifying genetic markers which sensitize tumor cells to TMZ could personalize therapy and improve outcomes.

Methods

We evaluated TMZ-related survival associations of pathogenic germline SNPs and genetically predicted transcript levels within 34 DNA repair genes among 1504 glioma patients from the UCSF Adult Glioma Study and Mayo Clinic whose diagnoses spanned pre- and post-TMZ eras within the major known glioma prognostic molecular subtypes.

Results

Among those who received TMZ, 5 SNPs were associated with overall survival, but not in those who did not receive TMZ. Only rs2308321-G, in MGMT, was associated with decreased survival (HR=1.21, p=0.019) for all glioma subtypes. Rs73191162-T (near UNG), rs13076508-C (near PARP3), rs7840433-A (near NEIL2), and rs3130618-A (near MSH5) were only associated with survival and TMZ treatment for certain subtypes, suggesting subtype-specific germline chemo-sensitization.Genetically predicted elevated compared to normal brain expression of PNKP was associated with dramatically worse survival for TMZ-treated patients with IDH-mutant and 1p/19q non-codeleted gliomas (p=0.015). Similarly, NEIL2 and TDG expressions were associated with altered TMZ-related survival only among certain subtypes.

Conclusions

Functional germline alterations within DNA repair genes were associated with TMZ sensitivity, measured by overall survival, among adults with glioma, these variants should be evaluated in prospective analyses and functional studies.

Chlorpromazine overcomes temozolomide resistance in glioblastoma by inhibiting Cx43 and essential DNA repair pathways

BACKGROUND

In the fight against GBM, drug repurposing emerges as a viable and time-saving approach to explore new treatment options. Chlorpromazine, an old antipsychotic medication, has recently arisen as a promising candidate for repositioning in GBM therapy in addition to temozolomide, the first-line standard of care. We previously demonstrated the antitumor efficacy of chlorpromazine and its synergistic effects with temozolomide in suppressing GBM cell malignant features in vitro. This prompted us to accomplish a Phase II clinical trial to evaluate the efficacy and safety of adding chlorpromazine to temozolomide in GBM patients with unmethylated MGMT gene promoter. In this in vitro study, we investigate the potential role of chlorpromazine in overcoming temozolomide resistance.

METHODS

In our experimental set, we analyzed Connexin-43 expression at both the transcriptional and protein levels in control- and chlorpromazine-treated GBM cells. DNA damage and subsequent repair were assessed by immunofluorescence of γ-H2AX and Reverse-Phase Protein microArrays in chlorpromazine treated GBM cell lines. To elucidate the relationship between DNA repair systems and chemoresistance, we analyzed a signature of DNA repair genes in GBM cells after treatment with chlorpromazine, temozolomide and Connexin-43 downregulation.

RESULTS

Chlorpromazine treatment significantly downregulated connexin-43 expression in GBM cells, consequently compromising connexin-dependent cellular resilience, and ultimately contributing to cell death. In line with this, we observed concordant post-translational modifications of molecular determinants involved in DNA damage and repair pathways. Our evaluation of DNA repair genes revealed that temozolomide elicited an increase, while chlorpromazine, as well as connexin-43 silencing, a decrease in DNA repair gene expression in GBM cells.

CONCLUSIONS

Chlorpromazine potentiates the cytotoxic effects of the alkylating agent temozolomide through a mechanism involving downregulation of Cx43 expression and disruption of the cell cycle arrest essential for DNA repair processes. This finding suggests that chlorpromazine may be a potential therapeutic strategy to overcome TMZ resistance in GBM cells by inhibiting their DNA repair mechanisms.

Albumin-bound paclitaxel augment temozolomide treatment sensitivity of glioblastoma cells by disrupting DNA damage repair and promoting ferroptosis

BACKGROUND

Temozolomide (TMZ) treatment efficacy in glioblastoma (GBM) patients has been limited by resistance in the clinic. Currently, there are no clinically proven therapeutic options available to restore TMZ treatment sensitivity. Here, we investigated the potential of albumin-bound paclitaxel (ABX), a novel microtubule targeting agent, in sensitizing GBM cells to TMZ and elucidated its underlying molecular mechanism.

METHODS

A series of in vivo and in vitro experiments based on two GBM cell lines and two primary GBM cells were designed to evaluate the efficacy of ABX in sensitizing GBM cells to TMZ. Further proteomic analysis and validation experiments were performed to explore the underlying molecular mechanism. Finally, the efficacy and mechanism were validated in GBM patients derived organoids (PDOs) models.

RESULTS

ABX exhibited a synergistic inhibitory effect on GBM cells when combined with TMZ in vitro. Combination treatment of TMZ and ABX was highly effective in suppressing GBM progression and significantly prolonged the survival oforthotopic xenograft nude mice, with negligible side effects. Further proteomic analysis and experimental validation demonstrated that the combined treatment of ABX and TMZ can induce sustained DNA damage by disrupting XPC and ERCC1 expression and nuclear localization. Additionally, the combination treatment can enhance ferroptosis through regulating HOXM1 and GPX4 expression. Preclinical drug-sensitivity testing based on GBM PDOs models confirmed that combination therapy was significantly more effective than conventional TMZ monotherapy.

CONCLUSION

Our findings suggest that ABX has the potential to enhance TMZ treatment sensitivity in GBM, which provides a promising therapeutic strategy for GBM patients.

Transcriptomic Profiling of DNA Damage Response in Patient-Derived Glioblastoma Cells before and after Radiation and Temozolomide Treatment

Glioblastoma is a highly aggressive, invasive and treatment-resistant tumour. The DNA damage response (DDR) provides tumour cells with enhanced ability to activate cell cycle arrest and repair treatment-induced DNA damage. We studied the expression of DDR, its relationship with standard treatment response and patient survival, and its activation after treatment. The transcriptomic profile of DDR pathways was characterised within a cohort of isocitrate dehydrogenase (IDH) wild-type glioblastoma from The Cancer Genome Atlas (TCGA) and 12 patient-derived glioblastoma cell lines. The relationship between DDR expression and patient survival and cell line response to temozolomide (TMZ) or radiation therapy (RT) was assessed. Finally, the expression of 84 DDR genes was examined in glioblastoma cells treated with TMZ and/or RT. Although distinct DDR cluster groups were apparent in the TCGA cohort and cell lines, no significant differences in OS and treatment response were observed. At the gene level, the high expression of ATP23, RAD51C and RPA3 independently associated with poor prognosis in glioblastoma patients. Finally, we observed a substantial upregulation of DDR genes after treatment with TMZ and/or RT, particularly in RT-treated glioblastoma cells, peaking within 24 h after treatment. Our results confirm the potential influence of DDR genes in patient outcome. The observation of DDR genes in response to TMZ and RT gives insight into the global response of DDR pathways after adjuvant treatment in glioblastoma, which may have utility in determining DDR targets for inhibition.

Combinatorial Effect of PLK1 Inhibition with Temozolomide and Radiation in Glioblastoma

Simple Summary

There is a critical need to identify readily translatable adjuncts to potentiate the dismal median survivals of only 15–20 months in glioblastoma (GBM) patients after standard of care, i.e., concurrent Temozolomide (TMZ) and radiation (XRT) therapy. Here we demonstrated that the Polo-like kinase 1 (PLK1) inhibitor volasertib, which has been employed in cancer clinical trials, has activity against GBM in the contexts of both as monotherapy and as an adjunct to standard of care (SOC). In addition to corroborating the known effects of volasertib, we found novel impacts of volasertib on mitochondrial membrane potential, ROS generation, persistent DNA damage and signaling pathways such as ERK/MAPK, AMPK and glucocorticoid receptor. Together these studies support the potential importance of PLK1 inhibitors as an adjunct to GBM SOC therapy that warrants further preclinical investigation.

Abstract

New strategies that improve median survivals of only ~15–20 months for glioblastoma (GBM) with the current standard of care (SOC) which is concurrent temozolomide (TMZ) and radiation (XRT) treatment are urgently needed. Inhibition of polo-like kinase 1 (PLK1), a multifunctional cell cycle regulator, overexpressed in GBM has shown therapeutic promise but has never been tested in the context of SOC. Therefore, we examined the mechanistic and therapeutic impact of PLK1 specific inhibitor (volasertib) alone and in combination with TMZ and/or XRT on GBM cells. We quantified the effects of volasertib alone and in combination with TMZ and/or XRT on GBM cell cytotoxicity/apoptosis, mitochondrial membrane potential (MtMP), reactive oxygen species (ROS), cell cycle, stemness, DNA damage, DNA repair genes, cellular signaling and in-vivo tumor growth. Volasertib alone and in combination with TMZ and/or XRT promoted apoptotic cell death, altered MtMP, increased ROS and G2/M cell cycle arrest. Combined volasertib and TMZ treatment reduced side population (SP) indicating activity against GBM stem-like cells. Volasertib combinatorial treatment also significantly increased DNA damage and reduced cell survival by inhibition of DNA repair gene expression and modulation of ERK/MAPK, AMPK and glucocorticoid receptor signaling. Finally, as observed in-vitro, combined volasertib and TMZ treatment resulted in synergistic inhibition of tumor growth in-vivo. Together these results identify new mechanisms of action for volasertib that provide a strong rationale for further investigation of PLK1 inhibition as an adjunct to current GBM SOC therapy.

DNA damage repair in glioblastoma: current perspectives on its role in tumour progression, treatment resistance and PIKKing potential therapeutic targets

BACKGROUND

The aggressive, invasive and treatment resistant nature of glioblastoma makes it one of the most lethal cancers in humans. Total surgical resection is difficult, and a combination of radiation and chemotherapy is used to treat the remaining invasive cells beyond the tumour border by inducing DNA damage and activating cell death pathways in glioblastoma cells. Unfortunately, recurrence is common and a major hurdle in treatment, often met with a more aggressive and treatment resistant tumour. A mechanism of resistance is the response of DNA repair pathways upon treatment-induced DNA damage, which enact cell-cycle arrest and repair of DNA damage that would otherwise cause cell death in tumour cells.

CONCLUSIONS

In this review, we discuss the significance of DNA repair mechanisms in tumour formation, aggression and treatment resistance. We identify an underlying trend in the literature, wherein alterations in DNA repair pathways facilitate glioma progression, while established high-grade gliomas benefit from constitutively active DNA repair pathways in the repair of treatment-induced DNA damage. We also consider the clinical feasibility of inhibiting DNA repair in glioblastoma and current strategies of using DNA repair inhibitors as agents in combination with chemotherapy, radiation or immunotherapy. Finally, the importance of blood-brain barrier penetrance when designing novel small-molecule inhibitors is discussed.

Genotoxic therapy and resistance mechanism in gliomas

Glioma is one of the most common and lethal brain tumors. Surgical resection followed by radiotherapy plus chemotherapy is the current standard of care for patients with glioma. The existence of resistance to genotoxic therapy, as well as the nature of tumor heterogeneity greatly limits the efficacy of glioma therapy. DNA damage repair pathways play essential roles in many aspects of glioma biology such as cancer progression, therapy resistance, and tumor relapse. O6-methylguanine-DNA methyltransferase (MGMT) repairs the cytotoxic DNA lesion generated by temozolomide (TMZ), considered as the main mechanism of drug resistance. In addition, mismatch repair, base excision repair, and homologous recombination DNA repair also play pivotal roles in treatment resistance as well. Furthermore, cellular mechanisms, such as cancer stem cells, evasion from apoptosis, and metabolic reprogramming, also contribute to TMZ resistance in gliomas. Investigations over the past two decades have revealed comprehensive mechanisms of glioma therapy resistance, which has led to the development of novel therapeutic strategies and targeting molecules.

Excision repair cross-complementing group 2 upregulation is a potential predictive biomarker for oral squamous cell carcinoma recurrence

Oral cancer is the fourth most common type of cancer among males in Taiwan, and the prognosis for patients with advanced-stage oral squamous cell carcinoma (OSCC) remains poor. The present study investigated the prognostic value of three DNA repair genes, namely excision repair cross-complementing group 1 (ERCC1), ERCC2 and X-ray repair cross-complementing group 1 (XRCC1) in OSCC. The protein expression levels of XRCC1, ERCC1 and ERCC2 in oral cell lines were analyzed via western blotting and immunohistochemistry using samples from 98 patients with biopsy-proven OSCC, while the χ2 test was used to analyze the clinicopathological association. Kaplan-Meier estimates were used to determine the prognostic value of XRCC1, ERCC1 and ERCC2 for overall survival, and the log-rank test was used to evaluate the significance of differences. Multivariate analysis revealed a positive association between ERCC2 expression and OSCC recurrence (19.64-fold; 95% CI, 5.00-77.1; P<0.001). In addition, the high protein expression levels of XRCC1, ERCC1 and ERCC2 were associated with poor disease-free and overall survival rates. Therefore, the present study suggested that high ERCC2 expression may be a risk factor for OSCC recurrence.

Design, Synthesis, and Molecular Docking Study of New Tyrosyl-DNA Phosphodiesterase 1 (TDP1) Inhibitors Combining Resin Acids and Adamantane Moieties

In this paper, a series of novel abietyl and dehydroabietyl ureas, thioureas, amides, and thioamides bearing adamantane moieties were designed, synthesized, and evaluated for their inhibitory activities against tyrosil-DNA-phosphodiesterase 1 (TDP1). The synthesized compounds were able to inhibit TDP1 at micromolar concentrations (0.19–2.3 µM) and demonstrated low cytotoxicity in the T98G glioma cell line. The effect of the terpene fragment, the linker structure, and the adamantane residue on the biological properties of the new compounds was investigated. Based on molecular docking results, we suppose that adamantane derivatives of resin acids bind to the TDP1 covalent intermediate, forming a hydrogen bond with Ser463 and hydrophobic contacts with the Phe259 and Trp590 residues and the oligonucleotide fragment of the substrate.

Transcription Factor ZNF326 Upregulates the Expression of ERCC1 and HDAC7 and its Clinicopathologic Significance in Glioma

Previous reports that we have coauthored have shown that transcription factor ZNF326 can upregulate the expression of ERCC1 and HDAC7, and downregulate the expression of LTBP4 and ZNF383 in lung-cancer cells. However, whether tissue-specificity of the ZNF326 function exists in glioma tissue remains unclear. In this study, overexpression or knockdown of ZNF326 in glioma cells caused upregulation or downregulation, respectively, of the protein and micro RNA (mRNA) levels of ERCC1 and HDAC7. The levels of LTBP4 and ZNF383 were not significantly changed. Immunohistochemical results showed that ZNF326 was not only highly expressed in glioma but was also positively correlated with the expression of ERCC1 and HDAC7. Moreover, the expression of ERCC1 and HDAC7 was enhanced with the increase in tumor grade. However, there was no correlation between ZNF326 and the expression of LTBP4 and ZNF383. Therefore, the detection of ZNF326, ERCC1, and HDAC7 expressions was useful for identifying different grades of glioma.

The role of DNA damage response in chemo- and radio-resistance of cancer cells: Can DDR inhibitors sole the problem?

Up to now, many improvements have been made in providing more therapeutic strategies for cancer patients. The lack of susceptibility to common therapies like chemo- and radio-therapy is one of the reasons why we need more methods in the field of cancer therapy. DNA damage response (DDR) is a set of mechanisms which identifies DNA lesions and triggers the repair process for restoring DNA after causing an arrest in the cell cycle. The ability of DDR in maintaining the genome stability and integrity can be favorable to cancerous cells which are exposed to radiation therapy or are treated with chemotherapeutic agents. When DDR mechanisms are error-free in cancer cells, they can escape the expected cellular death and display resistance to treatment. In this regard, targeting different components of DDR can help to increase the susceptibility of advanced tumors to chemo- and radio-therapy.

Safety of transcranial direct current stimulation in healthy participants

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Transcranial Direct Current Stimulation (tDCS) is mostly reported as safe.

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BUT it could induce life-changing conditions in healthy volunteers.

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Scientific community MUST be warned that tDCS may be harmful and protect healthy volunteers.

Proneural and mesenchymal glioma stem cells display major differences in splicing and lncRNA profiles

Therapy resistance and recurrence in high-grade gliomas are driven by their populations of glioma stem cells (GSCs). Thus, detailed molecular characterization of GSCs is needed to develop more effective therapies. We conducted a study to identify differences in the splicing profile and expression of long non-coding RNAs in proneural and mesenchymal GSC cell lines. Genes related to cell cycle, DNA repair, cilium assembly, and splicing showed the most differences between GSC subgroups. We also identified genes distinctly associated with survival among patients of mesenchymal or proneural subgroups. We determined that multiple long non-coding RNAs with increased expression in mesenchymal GSCs are associated with poor survival of glioblastoma patients. In summary, our study established critical differences between proneural and mesenchymal GSCs in splicing profiles and expression of long non-coding RNA. These splicing isoforms and lncRNA signatures may contribute to the uniqueness of GSC subgroups, thus contributing to cancer phenotypes and explaining differences in therapeutic responses.

DNA repair genes in astrocytoma tumorigenesis, progression and therapy resistance

Glioblastoma (GBM) is the most common and malignant type of primary brain tumor, showing rapid development and resistance to therapies. On average, patients survive 14.6 months after diagnosis and less than 5% survive five years or more. Several pieces of evidence have suggested that the DNA damage signaling and repair activities are directly correlated with GBM phenotype and exhibit opposite functions in cancer establishment and progression. The functions of these pathways appear to present a dual role in tumorigenesis and cancer progression. Activation and/or overexpression of ATRX, ATM and RAD51 genes were extensively characterized as barriers for GBM initiation, but paradoxically the exacerbated activity of these genes was further associated with cancer progression to more aggressive stages. Excessive amounts of other DNA repair proteins, namely HJURP, EXO1, NEIL3, BRCA2, and BRIP, have also been connected to proliferative competence, resistance and poor prognosis. This scenario suggests that these networks help tumor cells to manage replicative stress and treatment-induced damage, diminishing genome instability and conferring therapy resistance. Finally, in this review we address promising new drugs and therapeutic approaches with potential to improve patient survival. However, despite all technological advances, the prognosis is still dismal and further research is needed to dissect such complex mechanisms.

Synthetic lethality between BRCA1 deficiency and poly(ADP-ribose) polymerase inhibition is modulated by processing of endogenous oxidative DNA damage

Poly(ADP-ribose) polymerases (PARPs) facilitate the repair of DNA single-strand breaks (SSBs). When PARPs are inhibited, unrepaired SSBs colliding with replication forks give rise to cytotoxic double-strand breaks. These are normally rescued by homologous recombination (HR), but, in cells with suboptimal HR, PARP inhibition leads to genomic instability and cell death, a phenomenon currently exploited in the therapy of ovarian cancers in BRCA1/2 mutation carriers. In spite of their promise, resistance to PARP inhibitors (PARPis) has already emerged. In order to identify the possible underlying causes of the resistance, we set out to identify the endogenous source of DNA damage that activates PARPs. We argued that if the toxicity of PARPis is indeed caused by unrepaired SSBs, these breaks must arise spontaneously, because PARPis are used as single agents. We now show that a significant contributor to PARPi toxicity is oxygen metabolism. While BRCA1-depleted or -mutated cells were hypersensitive to the clinically approved PARPi olaparib, its toxicity was significantly attenuated by depletion of OGG1 or MYH DNA glycosylases, as well as by treatment with reactive oxygen species scavengers, growth under hypoxic conditions or chemical OGG1 inhibition. Thus, clinical resistance to PARPi therapy may emerge simply through reduced efficiency of oxidative damage repair.

Reduced expression of DNA repair genes and chemosensitivity in 1p19q codeleted lower-grade gliomas

BACKGROUND

Lower-grade gliomas (LGGs, defined as WHO grades II and III) with 1p19q codeletion have increased chemosensitivity when compared to LGGs without 1p19q codeletion, but the mechanism is currently unknown.

METHODS

RNAseq data from 515 LGG patients in the Cancer Genome Atlas (TCGA) were analyzed to compare the effect of expression of the 9 DNA repair genes located on chromosome arms 1p and 19q on progression free survival (PFS) and overall survival (OS) between patients who received chemotherapy and those who did not. Chemosensitivity of cells with DNA repair genes knocked down was tested using MTS cell proliferation assay in HS683 cell line and U251 cell line.

RESULTS

The expression of 9 DNA repair genes on 1p and 19q was significantly lower in 1p19q-codeleted tumors (n = 175) than in tumors without the codeletion (n = 337) (p < 0.001). In LGG patients who received chemotherapy, lower expression of LIG1, POLD1, PNKP, RAD54L and MUTYH was associated with longer PFS and OS. This difference between chemotherapy and non-chemotherapy groups in the association of gene expression with survival was not observed in non-DNA repair genes located on chromosome arms 1p and 19q. MTS assays showed that knockdown of DNA repair genes LIG1, POLD1, PNKP, RAD54L and MUTYH significantly inhibited recovery in response to temozolomide when compared with control group (p < 0.001).

CONCLUSIONS

Our results suggest that reduced expression of DNA repair genes on chromosome arms 1p and 19q may account for the increased chemosensitivity of LGGs with 1p19q codeletion.

Myxopapillary Ependymoma of Lumbar Soft Tissue: A Case Report With Gene Expression Evaluation

Primary extraspinal myxopapillary ependymoma (MPE) is an exceptionally rare lesion that is mainly located in the subcutaneous sacrococcygeal region. We describe the first case of MPE that presented as an intramuscular tumor mass located in the lumbar area. Absence of the visible connection with the spinal cord and lack of any other tumors in the reported case argue for the primary ectopic origin of the MPE. The differential diagnosis of MPE is discussed. Additionally, we evaluated the expression level of molecular biomarkers that have a prognostic value in central nervous system tumors.

Genome-wide DNA copy number analysis in clonally expanded human ovarian cancer cells with distinct invasive/migratory capacities

Ovarian cancer has the worst prognosis of any gynecological malignancy, and generally presents with metastasis at advanced stages. Copy number variation (CNV) frequently contributes to the alteration of oncogenic drivers. In this study, we sought to identify genetic targets in heterogeneous clones from human ovarian cancers cells. We used array-based technology to systematically assess all the genes with CNVs in cell models clonally expanded from A2780 and SKOV3 ovarian cancer cell lines with distinct highly and minimally invasive/migratory capacities. We found that copy number alterations differed between matched highly and minimally invasive/migratory subclones, differentially affecting specific functional processes including immune response processes, DNA damage repair, cell cycle and cell proliferation. We also identified seven genes as strong candidates, including DDB1, ERCC1, ERCC2, PRPF19, BCAT1, CDKN1B and MARK4, by integrating the above data with gene expression and clinical outcome data. Thus, by determining the molecular signatures of heterogeneous invasive/migratory ovarian cancer cells, we identified genes that could be specifically targeted for the treatment and prognosis of advanced ovarian cancers.

Efficacy of Onalespib, a Long-Acting Second-Generation HSP90 Inhibitor, as a Single Agent and in Combination with Temozolomide against Malignant Gliomas

Purpose: HSP90, a highly conserved molecular chaperone that regulates the function of several oncogenic client proteins, is altered in glioblastoma. However, HSP90 inhibitors currently in clinical trials are short-acting, have unacceptable toxicities, or are unable to cross the blood-brain barrier (BBB). We examined the efficacy of onalespib, a potent, long-acting novel HSP90 inhibitor as a single agent and in combination with temozolomide (TMZ) against gliomas in vitro and in vivoExperimental Design: The effect of onalespib on HSP90, its client proteins, and on the biology of glioma cell lines and patient-derived glioma-initiating cells (GSC) was determined. Brain and plasma pharmacokinetics of onalespib and its ability to inhibit HSP90 in vivo were assessed in non-tumor-bearing mice. Its efficacy as a single agent or in combination with TMZ was assessed in vitro and in vivo using zebrafish and patient-derived GSC xenograft mouse glioma models.Results: Onalespib-mediated HSP90 inhibition depleted several survival-promoting client proteins such as EGFR, EGFRvIII, and AKT, disrupted their downstream signaling, and decreased the proliferation, migration, angiogenesis, and survival of glioma cell lines and GSCs. Onalespib effectively crossed the BBB to inhibit HSP90 in vivo and extended survival as a single agent in zebrafish xenografts and in combination with TMZ in both zebrafish and GSC mouse xenografts.Conclusions: Our results demonstrate the long-acting effects of onalespib against gliomas in vitro and in vivo, which combined with its ability to cross the BBB support its development as a potential therapeutic agent in combination with TMZ against gliomas. Clin Cancer Res; 23(20); 6215-26. ©2017 AACR.

Extracellular Vesicles As Modulators of Tumor Microenvironment and Disease Progression in Glioma

Diffuse gliomas are lethal tumors of the central nervous system (CNS) characterized by infiltrative growth, aggressive nature, and therapeutic resistance. The recent 2016 WHO classification for CNS tumors categorizes diffuse glioma into two major types that include IDH wild-type glioblastoma, which is the predominant type and IDH-mutant glioblastoma, which is less common and displays better prognosis. Recent studies suggest presence of a distinct cell population with stem cell features termed as glioma stem cells (GSCs) to be causal in driving tumor growth in glioblastoma. The presence of a stem and progenitor population possibly makes glioblastoma highly heterogeneous. Significantly, tumor growth is driven by interaction of cells residing within the tumor with the surrounding milieu termed as the tumor microenvironment. It comprises of various cell types such as endothelial cells, secreted factors, and the surrounding extracellular matrix, which altogether help perpetuate the proliferation of GSCs. One of the important mediators critical to the cross talk is extracellular vesicles (EVs). These nano-sized vesicles play important roles in intercellular communication by transporting bioactive molecules into the surrounding milieu, thereby altering cellular functions and/or reprogramming recipient cells. With the growing information on the contribution of EVs in modulation of the tumor microenvironment, it is important to determine their role in both supporting as well as promoting tumor growth in glioma. In this review, we provide a comprehensive overview of the role of EVs in tumor progression and glioma pathogenesis.

Linc00152 Functions as a Competing Endogenous RNA to Confer Oxaliplatin Resistance and Holds Prognostic Values in Colon Cancer

Long noncoding RNAs act as crucial regulators in plenty of human cancers, yet their potential roles and molecular mechanisms in chemoresistance are poorly understood. This study showed that a novel lncRNA, long intergenic noncoding RNA 152 (Linc00152 ), promoted tumor progression and conferred resistance to oxaliplatin (L-OHP)-induced apoptosis in vitro and in vivo. It antagonized chemosensitivity through acting as a competing endogenous RNA to modulate the expression of miR-193a-3p, and then erb-b2 receptor tyrosine kinase 4 (ERBB4). Knockdown of ERBB4 in colon cancer cells decreased AKT phosphorylation, which resulted in decreased L-OHP resistance. Consistent with above findings, the specific AKT signaling inhibitor and activator were used, respectively, which demonstrated that Linc00152 contributed to L-OHP resistance at least partly through activating AKT pathway. Further studies indicated that Linc00152 was increased and appeared to be an independent prognostic factor for decreased survival and increased disease recurrence in stage II and III colon cancer patients undergoing L-OHP-based chemotherapy after surgery. Collectively, our findings established Linc00152 as a candidate prognostic indicator of outcome and drug responsiveness in colon cancer patients, and the involvement of competing endogenous RNAs mechanism in Linc00152/miR-193a-3p/ERBB4/AKT signaling axis may provide a novel choice in the investigation of drug resistance.