In Vitro and In Vivo Analysis of RTK Inhibitor Efficacy and Identification of Its Novel Targets in Glioblastomas

Treatment for glioblastoma consists of radiotherapy and temozolomide-based chemotherapy. However, virtually all patients recur, leading to a fatal outcome. Receptor tyrosine kinase (RTK)-targeted therapy has been the focus of attention in novel treatment options for these patients. Here, we compared the efficacy of imatinib, sunitinib, and cediranib in glioblastoma models. In the present work, the biologic effect of the drugs was screened by viability, cell cycle, apoptosis, migration, and invasion in vitro assays or in vivo by chick chorioallantoic membrane assay. Intracellular signaling was assessed by Western blot and the RTK targets were identified using phospho-RTK arrays. The amplified status of KIT, PDGFRA, and VEGFR2 genes was assessed by quantitative polymerase chain reaction. In a panel of 10 glioblastoma cell lines, we showed that cediranib was the most potent. In addition, cediranib and sunitinib synergistically sensitize the cells to temozolomide. Cediranib efficacy was shown to associate with higher cytostatic and unique cytotoxic effects in vitro and both antitumoral and antiangiogenic activity in vivo, which could associate with its great capacity to inhibit mitogen-activated protein kinase (MAPK) and AKT pathways. The molecular status of KIT, PDGFRA, and VEGFR2 did not predict glioblastoma cell responsiveness to any of the RTK inhibitors. Importantly, phospho-RTK arrays revealed novel targets for cediranib and sunitinib therapy. In conclusion, the novel targets found may be of value as future biomarkers for therapy response in glioblastoma and lead to the rational selection of patients for effective molecular targeted treatment.     

Combined RNAi-Mediated Suppression of Rictor and EGFR Resulted in Complete Tumor Regression in an Orthotopic Glioblastoma Tumor Model

The PI3K/AKT/mTOR pathway is commonly over activated in glioblastoma (GBM), and Rictor was shown to be an important regulator downstream of this pathway. EGFR overexpression is also frequently found in GBM tumors, and both EGFR and Rictor are associated with increased proliferation, invasion, metastasis and poor prognosis. This research evaluated in vitro and in vivo whether the combined silencing of EGFR and Rictor would result in therapeutic benefits. The therapeutic potential of targeting these proteins in combination with conventional agents with proven activity in GBM patients was also assessed. In vitro validation studies were carried out using siRNA-based gene silencing methods in a panel of three commercially available human GBM cell lines, including two PTEN mutant lines (U251MG and U118MG) and one PTEN-wild type line (LN229). The impact of EGFR and/or Rictor silencing on cell migration and sensitivity to chemotherapeutic drugs in vitro was determined. In vivo validation of these studies was focused on EGFR and/or Rictor silencing achieved using doxycycline-inducible shRNA-expressing U251MG cells implanted orthotopically in Rag2M mice brains. Target silencing, tumor size and tumor cell proliferation were assessed by quantification of immunohistofluorescence-stained markers. siRNA-mediated silencing of EGFR and Rictor reduced U251MG cell migration and increased sensitivity of the cells to irinotecan, temozolomide and vincristine. In LN229, co-silencing of EGFR and Rictor resulted in reduced cell migration, and increased sensitivity to vincristine and temozolomide. In U118MG, silencing of Rictor alone was sufficient to increase this line’s sensitivity to vincristine and temozolomide. In vivo, while the silencing of EGFR or Rictor alone had no significant effect on U251MG tumor growth, silencing of EGFR and Rictor together resulted in a complete eradication of tumors. These data suggest that the combined silencing of EGFR and Rictor should be an effective means of treating GBM.     

Curcumin induces EGFR degradation in lung adenocarcinoma and modulates p38 activation in intestine: the versatile adjuvant for gefitinib therapy

Background

Non-small cell lung cancer (NSCLC) patients with L858R or exon 19 deletion mutations in epidermal growth factor receptor (EGFR) have good responses to the tyrosine kinase inhibitor (TKI), gefitinib. However, patients with wild-type EGFR and acquired mutation in EGFR T790M are resistant to gefitinib treatment. Here, we showed that curcumin can improve the efficiency of gefitinib in the resistant NSCLC cells both in vitro and in vivo models.

Methods/Principal Findings

After screening 598 herbal and natural compounds, we found curcumin could inhibit cell proliferation in different gefitinib-resistant NSCLC cell lines; concentration-dependently down-regulate EGFR phosphorylation through promoting EGFR degradation in NSCLC cell lines with wild-type EGFR or T790M EGFR. In addition, the anti-tumor activity of gefitinib was potentiated via curcumin through blocking EGFR activation and inducing apoptosis in gefitinib-resistant NSCLC cell lines; also the combined treatment with curcumin and gefitinib exhibited significant inhibition in the CL1-5, A549 and H1975 xenografts tumor growth in SCID mice through reducing EGFR, c-MET, cyclin D1 expression, and inducing apoptosis activation through caspases-8, 9 and PARP. Interestingly, we observed that the combined treatment group represented better survival rate and less intestinal mucosal damage compare to gefitinib-alone therapy. We showed that curcumin attenuated the gefitinib-induced cell proliferation inhibition and apoptosis through altering p38 mitogen-activated protein kinase (MAPK) activation in intestinal epithelia cell.

Conclusions/Significance

Curcumin potentiates antitumor activity of gefitinib in cell lines and xenograft mice model of NSCLC through inhibition of proliferation, EGFR phosphorylation, and induction EGFR ubiquitination and apoptosis. In addition, curcumin attenuates gefitinib-induced gastrointestinal adverse effects via altering p38 activation. These findings provide a novel treatment strategy that curcumin as an adjuvant to increase the spectrum of the usage of gefitinib and overcome the gefitinib inefficiency in NSCLC patients.     

Inhibition of TRPM7 with waixenicin A reduces glioblastoma cellular functions

Glioblastoma (GBM) is the most common malignant primary brain tumour originating in the CNS. Median patient survival is <15 months with standard treatment which consists of surgery alongside radiation therapy and temozolomide chemotherapy. However, because of the aggressive nature of GBM, and the significant toxicity of these adjuvant therapies, long-term therapeutic effects are unsatisfactory. Thus, there is urgency to identify new drug targets for GBM. Recent evidence shows that the transient receptor potential melastatin 7 (TRPM7) cation channel is aberrantly upregulated in GBM and its inhibition leads to reduction of GBM cellular functions. This suggests that TRPM7 may be a potential drug target for GBM treatment. In this study, we assessed the effects of the specific TRPM7 antagonist waixenicin A on human GBM cell lines U87 or U251 both in vitro and in vivo. First, we demonstrated in vitro that application of waixenicin A reduced TRPM7 protein expression and inhibited the TRPM7-like currents in GBM cells. We also observed reduction of GBM cell viability, migration, and invasion. Using an intracranial xenograft GBM mouse model, we showed that with treatment of waixenicin A, there was increased cleaved caspase 3 activity, alongside reduction in Ki-67, cofilin, and Akt activity in vivo. Together, these data demonstrate higher GBM cell apoptosis, and lower proliferation, migration, invasion and survivability following treatment with waixenicin A.     

Focal Adhesion Kinase Inhibitors in Combination with Erlotinib Demonstrate Enhanced Anti-Tumor Activity in Non-Small Cell Lung Cancer

Blockade of epidermal growth factor receptor (EGFR) activity has been a primary therapeutic target for non-small cell lung cancers (NSCLC). As patients with wild-type EGFR have demonstrated only modest benefit from EGFR tyrosine kinase inhibitors (TKIs), there is a need for additional therapeutic approaches in patients with wild-type EGFR. As a key component of downstream integrin signalling and known receptor cross-talk with EGFR, we hypothesized that targeting focal adhesion kinase (FAK) activity, which has also been shown to correlate with aggressive stage in NSCLC, would lead to enhanced activity of EGFR TKIs. As such, EGFR TKI-resistant NSCLC cells (A549, H1299, H1975) were treated with the EGFR TKI erlotinib and FAK inhibitors (PF-573,228 or PF-562,271) both as single agents and in combination. We determined cell viability, apoptosis and 3-dimensional growth in vitro and assessed tumor growth in vivo. Treatment of EGFR TKI-resistant NSCLC cells with FAK inhibitor alone effectively inhibited cell viability in all cell lines tested; however, its use in combination with the EGFR TKI erlotinib was more effective at reducing cell viability than either treatment alone when tested in both 2- and 3-dimensional assays in vitro, with enhanced benefit seen in A549 cells. This increased efficacy may be due in part to the observed inhibition of Akt phosphorylation when the drugs were used in combination, where again A549 cells demonstrated the most inhibition following treatment with the drug combination. Combining erlotinib with FAK inhibitor was also potent in vivo as evidenced by reduced tumor growth in the A549 mouse xenograft model. We further ascertained that the enhanced sensitivity was irrespective of the LKB1 mutational status. In summary, we demonstrate the effectiveness of combining erlotinib and FAK inhibitors for use in known EGFR wild-type, EGFR TKI resistant cells, with the potential that a subset of cell types, which includes A549, could be particularly sensitive to this combination treatment. As such, further evaluation of this combination therapy is warranted and could prove to be an effective therapeutic approach for patients with inherent EGFR TKI-resistant NSCLC.     

Marsdenia tenacissima extract enhances gefitinib efficacy in non-small cell lung cancer xenografts

PurposeThe stem of Marsdenia tenacissima (Roxb.) Wight et Arn. has long been used as a medicine to treat cancer in China. Our previous in vitro results showed that Marsdenia tenacissima extract (MTE) overcomes gefitinib resistance in non-small cell lung cancer (NSCLC) cells. However, it is unknown whether MTE could enhance gefitinib efficacy in vivo. The present study was intended to investigate the in vivo anti-tumour activity of MTE combined with gefitinib.MethodsHuman NSCLC H460 (K-ras mutation) or H1975 cells (EGFR T790M mutation) were subcutaneously inoculated into nude mice. Tumour volume and body weight were measured regularly. Resected tumours were weighed after the animals were sacrificed. Immunoblotting or immunohistochemistry was used to assess the cellular proliferation and apoptosis in xenograft tumour tissue. Expression of the EGFR downstream pathways and c-Met were measured with western blot analysis to explore possible mechanisms.ResultsMTE (5, 10, 20 g/kg) dose-dependently reduced tumour growth and induced cell apoptosis. MTE suppressed EGFR related signals, and 20 g/kg was the most effective dose. Low-dose MTE (5 g/kg) significantly enhanced gefitinib efficacy in resistant H460 and H1975 xenografts. The combination inhibited tumour proliferation and induced cell apoptosis in both resistant NSCLC xenografts. Constitutive activation of the PI3K/Akt and MEK/ERK pathways is related to EGFR-TKI resistance. Accordingly, phosphorylation of PI3K/Akt/mTOR and ERK1/2 was suppressed after combination treatment. Simultaneously, cross-talked c-Met and EGFR were also prominently lowered in the presence of MTE combined with gefitinib.ConclusionThe present results suggest that the combination of MTE and gefitinib may be a promising therapeutic approach to enhance gefitinib efficacy in resistant NSCLC.     

Phosphorylation of Glutathione S-Transferase P1 (GSTP1) by Epidermal Growth Factor Receptor (EGFR) Promotes Formation of the GSTP1-c-Jun N-terminal kinase (JNK) Complex and Suppresses JNK Downstream Signaling and Apoptosis in Brain Tumor Cells

Under normal physiologic conditions, the glutathione S-transferase P1 (GSTP1) protein exists intracellularly as a dimer in reversible equilibrium with its monomeric subunits. In the latter form, GSTP1 binds to the mitogen-activated protein kinase, JNK, and inhibits JNK downstream signaling. In tumor cells, which frequently are characterized by constitutively high GSTP1 expression, GSTP1 undergoes phosphorylation by epidermal growth factor receptor (EGFR) at tyrosine residues 3, 7, and 198. Here we report on the effect of this EGFR-dependent GSTP1 tyrosine phosphorylation on the interaction of GSTP1 with JNK, on the regulation of JNK downstream signaling by GSTP1, and on tumor cell survival. Using in vitro and in vivo growing human brain tumors, we show that tyrosine phosphorylation shifts the GSTP1 dimer-monomer equilibrium to the monomeric state and facilitates the formation of the GSTP1-JNK complex, in which JNK is functionally inhibited. Targeted mutagenesis and functional analysis demonstrated that the increased GSTP1 binding to JNK results from phosphorylation of the GSTP1 C-terminal Tyr-198 by EGFR and is associated with a >2.5-fold decrease in JNK downstream signaling and a significant suppression of both spontaneous and drug-induced apoptosis in the tumor cells. The findings define a novel mechanism of regulatory control of JNK signaling that is mediated by the EGFR/GSTP1 cross-talk and provides a survival advantage for tumors with activated EGFR and high GSTP1 expression. The results lay the foundation for a novel strategy of dual EGFR/GSTP1 for treating EGFR+ve, GSTP1 expressing GBMs.     

DW-MRI as a Predictive Biomarker of Radiosensitization of GBM through Targeted Inhibition of Checkpoint Kinases

PURPOSE: The inherent treatment resistance of glioblastoma (GBM) can involve multiple mechanisms including checkpoint kinase (Chk1/2)-mediated increased DNA repair capability, which can attenuate the effects of genotoxic chemotherapies and radiation. The goal of this study was to evaluate diffusion-weighted magnetic resonance imaging (DW-MRI) as a biomarker for Chk1/2 inhibitors in combination with radiation for enhancement of treatment efficacy in GBM. EXPERIMENTAL DESIGN: We evaluated a specific small molecule inhibitor of Chk1/2, AZD7762, in combination with radiation using in vitro human cell lines and in vivo using a genetically engineered GBM mouse model. DW-MRI and T1-contrast MRI were used to follow treatment effects on intracranial tumor cellularity and growth rates, respectively. RESULTS: AZD7762 inhibited clonal proliferation in a panel of GBM cell lines and increased radiosensitivity in p53-mutated GBM cell lines to a greater extent compared to p53 wild-type cells. In vivo efficacy of AZD7762 demonstrated a dose-dependent inhibitory effect on GBM tumor growth rate and a reduction in tumor cellularity based on DW-MRI scans along with enhancement of radiation efficacy. CONCLUSION: DW-MRI was found to be a useful imaging biomarker for the detection of radiosensitization through inhibition of checkpoint kinases. Chk1/2 inhibition resulted in antiproliferative activity, prevention of DNA damage-induced repair, and radiosensitization in preclinical GBM tumor models, both in vitro and in vivo. The effects were found to be maximal in p53-mutated GBM cells. These results provide the rationale for integration of DW-MRI in clinical translation of Chk1/2 inhibition with radiation for the treatment of GBM.     

Inhibition of Caveolin-1 Restores Myeloid Cell Function in Human Glioblastoma

Background

Gliomas are the most common primary brain tumor in both children and adults. The prognosis for glioblastoma (GBM), the most common type of malignant glioma, has remained dismal, with median survival a little over one year despite maximal therapy with surgery, chemotherapy, and radiation. Although immunotherapy has become increasingly successful against many systemic tumors, clinical efficacy against brain tumors has been limited. One reason for this is an incomplete understanding of the local immunologic tumor microenvironment, particularly the function of large numbers of infiltrating myeloid derived cells. Monocytes/microglia are myeloid derived immunomodulatory cells, and they represent the predominant infiltrating immune cell population in gliomas. Our group has previously demonstrated using complementary in vitro and in vivo approaches that GBM tumor cells polarize tumor-associated myeloid cells (TAMs) and suppress their immunostimulatory function.

Methods and Results

To better understand the mechanisms responsible for this immunosuppression, we used gene expression profiling of stimulated monocytes in the presence or absence of GBM tumor cells. Our analysis identified caveolin-1 (CAV1), a plasma membrane molecule with pleiotropic functions, as significantly up-regulated in monocytes in the presence of GBMs. We validated these findings ex vivo by confirming up-regulation of CAV1 in TAMs isolated from GBMs immediately after surgical resection. Finally, we demonstrate that siRNA inhibition of CAV1 restores myeloid cell function, as measured by TNF-alpha secretion, in the presence of GBMs.

Conclusions

Restoration of TAM function through pharmacologic blockage of CAV1 may facilitate more successful immunotherapeutic strategies directed against a variety of solid human tumors infiltrated by TAMs.     

Sulforaphane attenuates EGFR signaling in NSCLC cells

Background

EGFR, a receptor tyrosine kinase (RTK), is frequently overexpressed and mutated in non-small cell lung cancer (NSCLC). Tyrosine kinase inhibitors (TKIs) have been widely used in the treatment of many cancers, including NSCLC. However, intrinsic and acquired resistance to TKI remains a common obstacle. One strategy that may help overcome EGFR-TKI resistance is to target EGFR for degradation. As EGFR is a client protein of heat-shock protein 90 (HSP90) and sulforaphane is known to functionally regulate HSP90, we hypothesized that sulforaphane could attenuate EGFR-related signaling and potentially be used to treat NSCLC.

Results

Our study revealed that sulforaphane displayed antitumor activity against NSCLC cells both in vitro and in vivo. The sensitivity of NSCLC cells to sulforaphane appeared to positively correlate with the inhibition of EGFR-related signaling, which was attributed to the increased proteasomal degradation of EGFR. Combined treatment of NSCLC cells with sulforaphane plus another HSP90 inhibitor (17-AAG) enhanced the inhibition of EGFR-related signaling both in vitro and in vivo.

Conclusions

We have shown that sulforaphane is a novel inhibitory modulator of EGFR expression and is effective in inhibiting the tumor growth of EGFR-TKI-resistant NSCLC cells. Our findings suggest that sulforaphane should be further explored for its potential clinical applications against NSCLC.     

In silico studies on marine actinomycetes as potential inhibitors for Glioblastoma multiforme

Glioblastoma multiforme (GBM) is considered to be the most common and often deadly disorder which affects the brain. It is caused by the over expression of proteins such as ephrin type-A receptor 2 (EphA2), epidermal growth factor receptor (EGFR) and EGFRvIII. These 3 proteins are considered to be the potential therapeutic targets for GBM. Among these, EphA2 is reported to be over-expressed in ˜90% of GBM. Herein we selected 35 compounds from marine actinomycetes, 5 in vitro and in vivo studied drug candidates and 4 commercially available drugs for GBM which were identified from literature and analysed by using comparative docking studies. Based on the glide scores and other in silico parameters available in Schrödinger, two selected marine actinomycetes compounds which include Tetracenomycin D and Chartreusin exhibited better binding energy among all the compounds studied in comparative docking. In this study we have demonstrated the inhibition of the 3 selected targets by the two bioactive compounds from marine actinomycetes through in-silico docking studies. Furthermore molecular dynamics simulation were also been performed to check the stability and the amino acids interacted with the 3 molecular targets (EphA2 receptor, EGFR, EGFRvIII) for GBM. Our results suggest that Tetracinomycin D and Chartreusin are the novel and potential inhibitor for the treatment of GBM.     

Translational Validation of Personalized Treatment Strategy Based on Genetic Characteristics of Glioblastoma

Glioblastoma (GBM) heterogeneity in the genomic and phenotypic properties has potentiated personalized approach against specific therapeutic targets of each GBM patient. The Cancer Genome Atlas (TCGA) Research Network has been established the comprehensive genomic abnormalities of GBM, which sub-classified GBMs into 4 different molecular subtypes. The molecular subtypes could be utilized to develop personalized treatment strategy for each subtype. We applied a classifying method, NTP (Nearest Template Prediction) method to determine molecular subtype of each GBM patient and corresponding orthotopic xenograft animal model. The models were derived from GBM cells dissociated from patient''s surgical sample. Specific drug candidates for each subtype were selected using an integrated pharmacological network database (PharmDB), which link drugs with subtype specific genes. Treatment effects of the drug candidates were determined by in vitro limiting dilution assay using patient-derived GBM cells primarily cultured from orthotopic xenograft tumors. The consistent identification of molecular subtype by the NTP method was validated using TCGA database. When subtypes were determined by the NTP method, orthotopic xenograft animal models faithfully maintained the molecular subtypes of parental tumors. Subtype specific drugs not only showed significant inhibition effects on the in vitro clonogenicity of patient-derived GBM cells but also synergistically reversed temozolomide resistance of MGMT-unmethylated patient-derived GBM cells. However, inhibitory effects on the clonogenicity were not totally subtype-specific. Personalized treatment approach based on genetic characteristics of each GBM could make better treatment outcomes of GBMs, although more sophisticated classifying techniques and subtype specific drugs need to be further elucidated.     

Alteration in Mir-21/PTEN Expression Modulates Gefitinib Resistance in Non-Small Cell Lung Cancer

Resistance to TKI treatment is a major obstacle in effective treatment of NSCLC. Besides EGFR mutation status, the mechanisms involved are largely unknown. Some evidence supports a role for microRNA 21 in modulating drug sensitivity of chemotherapy but its role in NSCLC TKI resistance still remains unexplored. This study aimed to investigate whether NSCLC miR-21 mediated resistance to TKIs also results from Pten targeting. Here, we show miR-21 promotes cancer by negatively regulating Pten expression in human NSCLC tissues: high miR-21 expression levels were associated with shorter DFS in 47 NSCLC patients; high miR-21/low Pten expression levels indicated a poor TKI clinical response and shorter overall survival in another 46 NSCLC patients undergoing TKI treatment. In vitro assays showed that miR-21 was up-regulated concomitantly to down-regulation of Pten in pc-9/GR cells in comparison with pc-9 cells. Moreover, over-expression of miR-21 significantly decreased gefitinib sensitivity by down-regulating Pten expression and activating Akt and ERK pathways in pc-9 cells, while miR-21 knockdown dramatically restored gefitinib sensitivity of pc-9/GR cells by up-regulation of Pten expression and inactivation of AKT and ERK pathways, in vivo and in vitro. We propose alteration of miR-21/Pten expression as a novel mechanism for TKI resistance in NSCLC cancer. Our findings provide a new basis for using miR 21/Pten-based therapeutic strategies to reverse gefitinib resistance in NSCLC.     

Epidermal Growth Factor Receptor Inhibition Reduces Angiogenesis via Hypoxia-Inducible Factor-1α and Notch1 in Head Neck Squamous Cell Carcinoma

Angiogenesis, a marker of cancer development, affects response to radiotherapy sensibility. This preclinical study aims to understand the receptor tyrosine kinase-mediated angiogenesis in head neck squamous cell carcinoma (HNSCC). The receptor tyrosine kinase activity in a transgenic mouse model of HNSCC was assessed. The anti-tumorigenetic and anti-angiogenetic effects of cetuximab-induced epidermal growth factor receptor (EGFR) inhibition were investigated in xenograft and transgenic mouse models of HNSCC. The signaling transduction of Notch1 and hypoxia-inducible factor-1α (HIF-1α) was also analyzed. EGFR was overexpressed and activated in the Tgfbr1/Pten deletion (2cKO) mouse model of HNSCC. Cetuximab significantly delayed tumor onset by reducing tumor angiogenesis. This drug exerted similar effects on heterotopic xenograft tumors. In the human HNSCC tissue array, increased EGFR expression correlated with increased HIF-1α and micro vessel density. Cetuximab inhibited tumor-induced angiogenesis in vitro and in vivo by significantly downregulating HIF-1α and Notch1. EGFR is involved in the tumor angiogenesis of HNSCC via the HIF-1α and Notch1 pathways. Therefore, targeting EGFR by suppressing hypoxia- and Notch-induced angiogenesis may benefit HNSCC therapy.     

Multi-Kinase Inhibitor C1 Triggers Mitotic Catastrophe of Glioma Stem Cells Mainly through MELK Kinase Inhibition

Glioblastoma multiforme (GBM) is a highly lethal brain tumor. Due to resistance to current therapies, patient prognosis remains poor and development of novel and effective GBM therapy is crucial. Glioma stem cells (GSCs) have gained attention as a therapeutic target in GBM due to their relative resistance to current therapies and potent tumor-initiating ability. Previously, we identified that the mitotic kinase maternal embryonic leucine-zipper kinase (MELK) is highly expressed in GBM tissues, specifically in GSCs, and its expression is inversely correlated with the post-surgical survival period of GBM patients. In addition, patient-derived GSCs depend on MELK for their survival and growth both in vitro and in vivo. Here, we demonstrate evidence that the role of MELK in the GSC survival is specifically dependent on its kinase activity. With in silico structure-based analysis for protein-compound interaction, we identified the small molecule Compound 1 (C1) is predicted to bind to the kinase-active site of MELK protein. Elimination of MELK kinase activity was confirmed by in vitro kinase assay in nano-molar concentrations. When patient-derived GSCs were treated with C1, they underwent mitotic arrest and subsequent cellular apoptosis in vitro, a phenotype identical to that observed with shRNA-mediated MELK knockdown. In addition, C1 treatment strongly induced tumor cell apoptosis in slice cultures of GBM surgical specimens and attenuated growth of mouse intracranial tumors derived from GSCs in a dose-dependent manner. Lastly, C1 treatment sensitizes GSCs to radiation treatment. Collectively, these data indicate that targeting MELK kinase activity is a promising approach to attenuate GBM growth by eliminating GSCs in tumors.     

Fasting Enhances the Response of Glioma to Chemo- and Radiotherapy

Background

Glioma, including anaplastic astrocytoma and glioblastoma multiforme (GBM) are among the most commonly diagnosed malignant adult brain tumors. GBM is a highly invasive and angiogenic tumor, resulting in a 12 to 15 months median survival. The treatment of GBM is multimodal and includes surgical resection, followed by adjuvant radio-and chemotherapy. We have previously reported that short-term starvation (STS) enhances the therapeutic index of chemo-treatments by differentially protecting normal cells against and/or sensitizing tumor cells to chemotoxicity.

Methodology and Principal Findings

To test the effect of starvation on glioma cells in vitro, we treated primary mouse glia, murine GL26, rat C6 and human U251, LN229 and A172 glioma cells with Temozolomide in ad lib and STS mimicking conditions. In vivo, mice with subcutaneous or intracranial models of GL26 glioma were starved for 48 hours prior to radio- or chemotherapy and the effects on tumor progression and survival were measured. Starvation-mimicking conditions sensitized murine, rat and human glioma cells, but not primary mixed glia, to chemotherapy. In vivo, starvation for 48 hours, which causes a significant reduction in blood glucose and circulating insulin-like growth factor 1 (IGF-1) levels, sensitized both subcutaneous and intracranial glioma models to radio-and chemotherapy.

Conclusion

Starvation-induced cancer sensitization to radio- or chemotherapy leads to extended survival in the in vivo glioma models tested. These results indicate that fasting and fasting-mimicking interventions could enhance the efficacy of existing cancer treatments against aggressive glioma in patients.     

Using the MCF10A/MCF10CA1a Breast Cancer Progression Cell Line Model to Investigate the Effect of Active,Mutant Forms of EGFR in Breast Cancer Development and Treatment Using Gefitinib

Background

Basal-like and triple negative breast cancer (TNBC) share common molecular features, poor prognosis and a propensity for metastasis to the brain. Amplification of epidermal growth factor receptor (EGFR) occurs in ~50% of basal-like breast cancer, and mutations in the epidermal growth factor receptor (EGFR) have been reported in up to ~ 10% of Asian TNBC patients. In non-small cell lung cancer several different mutations in the EGFR tyrosine kinase domain confer sensitivity to receptor tyrosine kinase inhibitors, but the tumourigenic potential of EGFR mutations in breast cells and their potential for targeted therapy is unknown.

Materials and Methods

Constructs containing wild type, G719S or E746-A750 deletion mutant forms of EGFR were transfected into the MCF10A breast cells and their tumorigenic derivative, MCF10CA1a. The effects of EGFR over-expression and mutation on proliferation, migration, invasion, response to gefitinib, and tumour formation in vivo was investigated. Copy number analysis and whole exome sequencing of the MCF10A and MCF10CA1a cell lines were also performed.

Results

Mutant EGFR increased MCF10A and MCF10CA1a proliferation and MCF10A gefitinib sensitivity. The EGFR-E746-A750 deletion increased MCF10CA1a cell migration and invasion, and greatly increased MCF10CA1a xenograft tumour formation and growth. Compared to MCF10A cells, MCF10CA1a cells exhibited large regions of gain on chromosomes 3 and 9, deletion on chromosome 7, and mutations in many genes implicated in cancer.

Conclusions

Mutant EGFR enhances the oncogenic properties of MCF10A cell line, and increases sensitivity to gefitinib. Although the addition of EGFR E746-A750 renders the MCF10CA1a cells more tumourigenic in vivo it is not accompanied by increased gefitinib sensitivity, perhaps due to additional mutations, including the PIK3CA H1047R mutation, that the MCF10CA1a cell line has acquired. Screening TNBC/basal-like breast cancer for EGFR mutations may prove useful for directing therapy but, as in non-small cell lung cancer, accompanying mutations in PIK3CA may confer gefitinib resistance.