Glioma-associated endothelial cells are chemoresistant to temozolomide

Extracellular vesicles released by glioma cells are decorated by Annexin A2 allowing for cellular uptake via heparan sulfate

Extracellular vesicles (EVs) play a crucial role in regulating cell behavior by delivering their cargo to target cells. However, the mechanisms underlying EV-cell interactions are not well understood. Previous studies have shown that heparan sulfate (HS) on target cell surfaces can act as receptors for exosomes uptake, but the ligand for HS on EVs has not been identified. In this study, we isolated EVs from glioma cell lines and glioma patients and identified Annexin A2 (AnxA2) on EVs as a key HS-binding ligand and mediator of EV-cell interactions. Our findings suggest that HS plays a dual role in EV-cell interactions, where HS on EVs captures AnxA2, and on target cells, it acts as a receptor for AnxA2. Removal of HS from the EV surface inhibits EV-target cell interaction by releasing AnxA2. Furthermore, we found that AnxA2-mediated binding of EVs to vascular endothelial cells promotes angiogenesis, and that antibody against AnxA2 inhibited the ability of glioma-derived EVs to stimulate angiogenesis by reducing the uptake of EVs. Our study also suggests that the AnxA2-HS interaction may accelerate the glioma-derived EVs-mediated angiogenesis and that combining AnxA2 on glioma cells with HS on endothelial cells may effectively improve the prognosis evaluation of glioma patients.

EZH2-Myc driven glioblastoma elicited by cytomegalovirus infection of human astrocytes

Mounting evidence is identifying human cytomegalovirus (HCMV) as a potential oncogenic virus. HCMV has been detected in malignant gliomas. EZH2 and Myc play a potential oncogenic role, correlating with the glioma grade. Herewith, we present the first experimental evidence for HCMV as a reprogramming vector, straight through the dedifferentiation of mature human astrocytes, and generation of CMV-Elicited Glioblastoma Cells (CEGBCs) possessing glioblastoma-like traits. HCMV counterparts the progression of the perceived cellular and molecular mechanisms succeeding the transformation and invasion processes with CEGBCs involved in spheroid formation and invasiveness. Glioblastoma multiforme (GBM) biopsies were characterized by an elevated EZH2 and Myc expression, possessing a strong positive correlation between the aforementioned markers in the presence of HCMV. From GBM tissues, we isolated HCMV clinical strains that transformed HAs toward CEGBCs exhibiting upregulated EZH2 and Myc. Spheroids generated from CEGBCs possessed invasion potential and were sensitive to EZH2 inhibitor, ganciclovir, and temozolomide triple therapy. HCMV clinical strains transform HAs and fit with an HCMV-induced glioblastoma model of oncogenesis, and supports the tumorigenic properties of Myc and EZH2 which might be highly pertinent in the pathophysiology of astrocytic brain tumors and thereby paving the way for new therapeutic strategies.

Anti-Vascular Endothelial Growth Factor Therapy Abolishes Glioma-Associated Endothelial Cell-Induced Tumor Invasion

Tumor-remodeled endothelial cells not only facilitate the formation of tumor angiogenesis but also promote tumorigenesis. In this study, we aimed to explore the interaction between glioma-associated endothelial cells (GAEs) and glioma cells. We found that different subtypes of glioma owned distinct GAE abundance. Glioma patients with high GAE abundance exhibited poor prognosis. Both the results of the bioinformatics analysis and the in vitro co-culture system assay revealed that GAE promoted glioma cell invasion. Besides, anti-vascular endothelial growth factor (VEGF) therapy partially abolished the effects of GAE on gliomas. Moreover, anti-VEGF therapy upregulated IL-2 expression in GAE, and exogenous IL-2 administration inhibits GAE-induced glioma cell invasion. Collectively, our present study provides a novel outstanding of the interaction between GAE and glioma cells.

P4HA1 Regulates CD31 via COL6A1 in the Transition of Glioblastoma Stem-Like Cells to Tumor Endothelioid Cells

Glioblastoma multiforme (GBM) is a common intracranial malignancy characterized by abundant and aberrant vasculature. The efficiency of existing antivascular treatments remains unsatisfactory. The transition of glioblastoma stem-like cells (GSCs) into tumor endothelioid cells (ECs) has been thought to cause glioma neovascularization and anti-angiogenesis tolerance, but the mechanisms regulating glioma transdifferentiation remains unclear. Our previous study found that P4HA1 regulates GSCs vascular mimicry in a hypoxic microenvironment, but the detailed molecular mechanism has not been determined. In this study, candidate protein COL6A1 was screened by mass spectrometry. In vitro experiments show that P4HA1 regulates the expression of CD31 via COL6A1, with the levels of expression of P4HA1, COL6A1 and the vascular endothelial molecular markers CD31 showing positive correlations in vivo assay. Altering the expression of P4HA1 in GSCs altered the expression of COL6A1 and CD31, thereby inducing glioma angiogenesis. In conclusion, this study revealed that the P4HA1/COL6A1 axis modulates the transdifferentiation process of GSCs into ECs. Interrupting this signaling axis can inhibit glioma angiogenesis, suggesting that this axis may be a novel target for antivascular therapy in patients with glioma.

Determinants of resistance to VEGF-TKI and immune checkpoint inhibitors in metastatic renal cell carcinoma

Vascular endothelial growth factor tyrosine kinase inhibitors (VEGF-TKIs) have been the mainstay of treatment for patients with advanced renal cell carcinoma (RCC). Despite its early promising results in decreasing or delaying the progression of RCC in patients, VEGF-TKIs have provided modest benefits in terms of disease-free progression, as 70% of the patients who initially respond to the treatment later develop drug resistance, with 30% of the patients innately resistant to VEGF-TKIs. In the past decade, several molecular and genetic mechanisms of VEGF-TKI resistance have been reported. One of the mechanisms of VEGF-TKIs is inhibition of the classical angiogenesis pathway. However, recent studies have shown the restoration of an alternative angiogenesis pathway in modulating resistance. Further, in the last 5 years, immune checkpoint inhibitors (ICIs) have revolutionized RCC treatment. Although some patients exhibit potent responses, a non-negligible number of patients are innately resistant or develop resistance within a few months to ICI therapy. Hence, an understanding of the mechanisms of VEGF-TKI and ICI resistance will help in formulating useful knowledge about developing effective treatment strategies for patients with advanced RCC. In this article, we review recent findings on the emerging understanding of RCC pathology, VEGF-TKI and ICI resistance mechanisms, and potential avenues to overcome these resistance mechanisms through rationally designed combination therapies.

NEO100 enables brain delivery of blood‒brain barrier impermeable therapeutics

BACKGROUND

Intracarotid injection of mannitol has been applied for decades to support brain entry of therapeutics that otherwise do not effectively cross the blood-brain barrier (BBB). However, the elaborate and high-risk nature of this procedure has kept its use restricted to well-equipped medical centers. We are developing a more straightforward approach to safely open the BBB, based on the intra-arterial (IA) injection of NEO100, a highly purified version of the natural monoterpene perillyl alcohol.

METHODS

In vitro barrier permeability with NEO100 was evaluated by transepithelial/transendothelial electrical resistance and antibody diffusion assays. Its mechanism of action was studied by western blot, microarray analysis, and electron microscopy. In mouse models, we performed ultrasound-guided intracardiac administration of NEO100, followed by intravenous application of Evan's blue, methotrexate, checkpoint-inhibitory antibodies, or chimeric antigen receptor (CAR) T cells.

RESULTS

NEO100 opened the BBB in a reversible and nontoxic fashion in vitro and in vivo. It enabled greatly increased brain entry of all tested therapeutics and was well tolerated by animals. Mechanistic studies revealed effects of NEO100 on different BBB transport pathways, along with translocation of tight junction proteins from the membrane to the cytoplasm in brain endothelial cells.

CONCLUSION

We envision that this procedure can be translated to patients in the form of transfemoral arterial catheterization and cannulation to the cerebral arteries, which represents a low-risk procedure commonly used in a variety of clinical settings. Combined with NEO100, it is expected to provide a safe, widely available approach to enhance brain entry of any therapeutic.

Enhanced brain delivery and therapeutic activity of trastuzumab after blood-brain barrier opening by NEO100 in mouse models of brain-metastatic breast cancer

BACKGROUND

The antitumor efficacy of human epidermal growth factor receptor 2 (HER2)-targeted therapies, such as humanized monoclonal antibody trastuzumab (Herceptin®, Roche), in patients with breast-to-brain cancer metastasis is hindered by the low permeability of the blood-brain barrier (BBB). NEO100 is a high-purity version of the natural monoterpene perillyl alcohol, produced under current good manufacturing practice (cGMP) regulations, that was shown previously to reversibly open the BBB in rodent models. Here we investigated whether NEO100 could enable brain entry of trastuzumab to achieve greater therapeutic activity.

METHODS

An in vitro BBB, consisting of human astrocytes and brain endothelial cells, was used to determine trastuzumab penetration in the presence or absence of NEO100. For in vivo studies, we administered intravenous (IV) trastuzumab or the trastuzumab-drug conjugate ado-trastuzumab emtansine (T-DM1; Kadcyla®, Roche), to mouse models harboring intracranial HER2+ breast cancer, with or without BBB opening via IA NEO100. Brain and tumor tissues were examined for the presence of trastuzumab and infiltration of immune cells. Therapeutic impact was evaluated based on overall survival.

RESULTS

NEO100 greatly increased trastuzumab penetration across an in vitro BBB. In vivo, IA NEO100-mediated BBB opening resulted in brain tumor-selective accumulation of trastuzumab, without detectable presence in normal brain tissue, along with increased presence of immune cell populations. IV delivery of trastuzumab or T-DM1 achieved significantly greater overall survival of tumor-bearing mice when combined with IA NEO100.

CONCLUSION

IA NEO100 facilitates brain tumor entry of trastuzumab and T-DM1 and significantly enhances their therapeutic efficacy, along with increased antibody-dependent immune cell recruitment.

Immunohistochemical Analysis of DNA Repair- and Drug-Efflux-Associated Molecules in Tumor and Peritumor Areas of Glioblastoma

Glioblastoma (GBM), the most commonly occurring primary tumor arising within the central nervous system, is characterized by high invasiveness and poor prognosis. In spite of the improvement in surgical techniques, along with the administration of chemo- and radiation therapy and the incessant investigation in search of prospective therapeutic targets, the local recurrence that frequently occurs within the peritumoral brain tissue makes GBM the most malignant and terminal type of astrocytoma. In the current study, we investigated both GBM and peritumoral tissues obtained from 55 hospitalized patients and the expression of three molecules involved in the onset of resistance/unresponsiveness to chemotherapy: O6-methylguanine methyltransferase (MGMT), breast cancer resistance protein (BCRP1), and A2B5. We propose that the expression of these molecules in the peritumoral tissue might be crucial to promoting the development of early tumorigenic events in the tissue surrounding GBM as well as responsible for the recurrence originating in this apparently normal area and, accordingly, for the resistance to treatment with the standard chemotherapeutic regimen. Notably, the inverse correlation found between MGMT expression in peritumoral tissue and patients’ survival suggests a prognostic role for this protein.

Endothelial-Tumor Cell Interaction in Brain and CNS Malignancies

Glioblastoma and other brain or CNS malignancies (like neuroblastoma and medulloblastoma) are difficult to treat and are characterized by excessive vascularization that favors further tumor growth. Since the mean overall survival of these types of diseases is low, the finding of new therapeutic approaches is imperative. In this review, we discuss the importance of the interaction between the endothelium and the tumor cells in brain and CNS malignancies. The different mechanisms of formation of new vessels that supply the tumor with nutrients are discussed. We also describe how the tumor cells (TC) alter the endothelial cell (EC) physiology in a way that favors tumorigenesis. In particular, mechanisms of EC-TC interaction are described such as (a) communication using secreted growth factors (i.e., VEGF, TGF-β), (b) intercellular communication through gap junctions (i.e., Cx43), and (c) indirect interaction via intermediate cell types (pericytes, astrocytes, neurons, and immune cells). At the signaling level, we outline the role of important mediators, like the gasotransmitter nitric oxide and different types of reactive oxygen species and the systems producing them. Finally, we briefly discuss the current antiangiogenic therapies used against brain and CNS tumors and the potential of new pharmacological interventions that target the EC-TC interaction.

miR-18a Inhibits BMP4 and HIF-1α Normalizing Brain Arteriovenous Malformations

RATIONALE

Brain arteriovenous malformations (AVMs) are abnormal tangles of vessels where arteries and veins directly connect without intervening capillary nets, increasing the risk of intracerebral hemorrhage and stroke. Current treatments are highly invasive and often not feasible. Thus, effective noninvasive treatments are needed. We previously showed that AVM-brain endothelial cells (BECs) secreted higher VEGF (vascular endothelial growth factor) and lower TSP-1 (thrombospondin-1) levels than control BEC; and that microRNA-18a (miR-18a) normalized AVM-BEC function and phenotype, although its mechanism remained unclear.

OBJECTIVE

To elucidate the mechanism of action and potential clinical application of miR-18a as an effective noninvasive treatment to selectively restore the phenotype and functionality of AVM vasculature.

METHODS AND RESULTS

The molecular pathways affected by miR-18a in patient-derived BECs and AVM-BECs were determined by Western blot, RT-qPCR (quantitative reverse transcription polymerase chain reaction), ELISA, co-IP, immunostaining, knockdown and overexpression studies, flow cytometry, and luciferase reporter assays. miR-18a was shown to increase TSP-1 and decrease VEGF by reducing PAI-1 (plasminogen activator inhibitor-1/SERPINE1) levels. Furthermore, miR-18a decreased the expression of BMP4 (bone morphogenetic protein 4) and HIF-1α (hypoxia-inducible factor 1α), blocking the BMP4/ALK (activin-like kinase) 2/ALK1/ALK5 and Notch signaling pathways. As determined by Boyden chamber assays, miR-18a also reduced the abnormal AVM-BEC invasiveness, which correlated with a decrease in MMP2 (matrix metalloproteinase 2), MMP9, and ADAM10 (ADAM metallopeptidase domain 10) levels. In vivo pharmacokinetic studies showed that miR-18a reaches the brain following intravenous and intranasal administration. Intranasal co-delivery of miR-18a and NEO100, a good manufacturing practices-quality form of perillyl alcohol, improved the pharmacokinetic profile of miR-18a in the brain without affecting its pharmacological properties. Ultra-high-resolution computed tomography angiography and immunostaining studies in an Mgp^-/- AVM mouse model showed that miR-18a decreased abnormal cerebral vasculature and restored the functionality of the bone marrow, lungs, spleen, and liver.

CONCLUSIONS

miR-18a may have significant clinical value in preventing, reducing, and potentially reversing AVM.

Inhibition of motility by NEO100 through the calpain-1/RhoA pathway

OBJECTIVE

Glioblastoma (GBM) is the most aggressive type of brain tumor with a high rate of tumor recurrence, and it often develops resistance over time to current standard of care chemotherapy. Its highly invasive nature plays an essential role in tumor progression and recurrence. Glioma stem cells (GSCs) are a subpopulation of glioma cells highly resistant to treatments and are considered responsible for tumor recurrence.

METHODS

Patient-derived populations of GSCs were analyzed by western blot, MTT, and cytoplasmic calcium labeling to determine the cytotoxicity of NEO100. High-performance liquid chromatography was used to evaluate the levels of NEO100 in the cell culture supernatants. The effects of the compound on GSC motility were studied using Boyden chamber migration, 3D spheroid migration and invasion assays, and an mRNA expression PCR array. A RhoA activation assay, western blot, and immunofluorescence techniques were employed to confirm the signaling pathways involved. Intracranial implantation of GSCs in athymic mice was used to evaluate the effects of NEO100 in vivo on tumor progression and overall survival.

RESULTS

Here, the authors show how NEO100, a highly purified good manufacturing practices-quality form of perillyl alcohol, is cytotoxic for different subtypes of GSCs, regardless of the mechanisms of DNA repair present. At doses similar to the IC50 (half maximal inhibitory concentration) values, NEO100 induces ER stress and activates apoptotic pathways in all GSC populations tested. At subcytotoxic doses in the micromolar range, NEO100 blocks migration and invasion of GSCs. These results correlate with a decrease in calpain-1 expression and an increase in RhoA activation, leading to enhanced contractility of the GSCs. In addition, NEO100 blocks the activation of the kinases Src, p42/44 MAPK, Akt, and Stat3, all related to cell proliferation and migration. Intranasal administration of NEO100 in mice with GSC-derived intracranial tumors led to a decrease in tumor progression and a 32% increase in overall survival. Immunostaining studies showed that NEO100 induces apoptosis and reduces GSC invasion in vivo.

CONCLUSIONS

NEO100 could have significant value targeting GSCs and could be used for GBM therapy as either monotherapy or a coadjuvant therapy during temozolomide rest cycles.

Perivascular signals alter global gene expression profile of glioblastoma and response to temozolomide in a gelatin hydrogel

Glioblastoma (GBM) is the most common primary malignant brain tumor, with patients exhibiting poor survival (median survival time: 15 months). Difficulties in treating GBM include not only the inability to resect the diffusively-invading tumor cells, but also therapeutic resistance. The perivascular niche (PVN) within the GBM tumor microenvironment contributes significantly to tumor cell invasion, cancer stem cell maintenance, and has been shown to protect tumor cells from radiation and chemotherapy. In this study, we examine how the inclusion of non-tumor cells in culture with tumor cells within a hydrogel impacts the overall gene expression profile of an in vitro artificial perivascular niche (PVN) comprised of endothelial and stromal cells directly cultured with GBM tumor cells within a methacrylamide-functionalized gelatin hydrogel. Using RNA-seq, we demonstrate that genes related to angiogenesis and extracellular matrix remodeling are upregulated in the PVN model compared to hydrogels containing only tumor or perivascular niche cells, while downregulated genes are related to cell cycle and DNA damage repair. Signaling pathways and genes commonly implicated in GBM malignancy, such as MGMT, EGFR, PI3K-Akt signaling, and Ras/MAPK signaling are also upregulated in the PVN model. We describe the kinetics of gene expression within the PVN hydrogels over a course of 14 days, observing the patterns associated with tumor cell-mediated endothelial network co-option and regression. We finally examine the effect of temozolomide, a frontline chemotherapy used clinically against GBM, on the PVN culture. Notably, the PVN model is less responsive to TMZ compared to hydrogels containing only tumor cells. Overall, these results demonstrate that inclusion of cellular and matrix-associated elements of the PVN within an in vitro model of GBM allows for the development of gene expression patterns and therapeutic response relevant to GBM.

The Rolipram-Perillyl Alcohol Conjugate (NEO214) Is A Mediator of Cell Death through the Death Receptor Pathway

Glioblastoma (GBM) is a highly aggressive primary brain tumor with a poor prognosis. Treatment with temozolomide, standard of care for gliomas, usually results in drug resistance and tumor recurrence. Therefore, there is a great need for drugs that target GBM. NEO214 was generated by covalently linking rolipram to perillyl alcohol (POH) via a carbamate bond to form the rolipram-perillyl alcohol conjugate. We show here that NEO214 is effective against both temozolomide-sensitive and temozolomide-resistant glioma cells. Furthermore, NEO214 is effective for different mechanisms of temozolomide resistance: overexpression of MGMT (O⁶-methylguanine methyl-transferase); deficiency in specific mismatch repair proteins; and overexpression of base excision repair (BER) proteins. NEO214-induced cytotoxicity involves apoptosis triggered by endoplasmic reticulum (ER) stress, as well as activating the Death Receptor 5 (DR5)/TNF-related apoptosis-inducing ligand (TRAIL/Apo2L) pathway. In vitro studies show that glioma cells treated with NEO214 express DR5 and exhibit cell death in the presence of recombinant TRAIL, a growth factor constitutively produced by astrocytes. Our in vitro 3D coculture data show that induction of DR5 in glioma cells with NEO214 and TRAIL cause tumor cell death very effectively and specifically for glioma cells. In vivo studies show that NEO214 has antitumor efficacy in orthotropic syngeneic rodent tumor models. Furthermore, NEO214 has therapeutic potential especially for brain tumors because this drug can cross the blood-brain barrier (BBB), and is effective in the TRAIL-rich astrocyte microenvironment. NEO214 is a strong candidate for use in the treatment of GBMs.

NEO212, a conjugate of temozolomide and perillyl alcohol, blocks the endothelial-to-mesenchymal transition in tumor-associated brain endothelial cells in glioblastoma

As the endothelial-to-mesenchymal transition (EndMT) supports the pro-angiogenic and invasive characteristics of glioblastoma multiforme (GBM), blocking this process would be a promising approach to inhibit tumor progression and recurrence. Here, we demonstrate that glioma stem cells (GSC) induce EndMT in brain endothelial cells (BEC). TGF-β signaling is necessary, but not sufficient to induce this EndMT process. Cell-to-cell contact and the contribution of Notch signaling are also required. NEO212, a conjugate of temozolomide and perillyl alcohol, blocks EndMT induction and reverts the mesenchymal phenotype of tumor-associated BEC (TuBEC) by blocking TGF-β and Notch pathways. Consequently, NEO212 reduces the invasiveness and pro-angiogenic properties associated with TuBEC, without affecting control BEC. Intracranial co-implantation of BEC and GSC in athymic mice showed that EndMT occurs in vivo, and can be blocked by NEO212, supporting the potential clinical value of NEO212 for the treatment of GBM.

Perivascular signals alter global gene expression profile of glioblastoma and response to temozolomide in a gelatin hydrogel

Glioblastoma (GBM) is the most common primary malignant brain tumor, with patients exhibiting poor survival (median survival time: 15 months). Difficulties in treating GBM include not only the inability to resect the diffusively-invading tumor cells, but also therapeutic resistance. The perivascular niche (PVN) within the GBM tumor microenvironment contributes significantly to tumor cell invasion, cancer stem cell maintenance, and has been shown to protect tumor cells from radiation and chemotherapy. In this study, we examine how the inclusion of non-tumor cells in culture with tumor cells within a hydrogel impacts the overall gene expression profile of an in vitro artificial perivascular niche (PVN) comprised of endothelial and stromal cells directly cultured with GBM tumor cells within a methacrylamide-functionalized gelatin hydrogel. Using RNA-seq, we demonstrate that genes related to angiogenesis and extracellular matrix remodeling are upregulated in the PVN model compared to hydrogels containing only tumor or perivascular niche cells, while downregulated genes are related to cell cycle and DNA damage repair. Signaling pathways and genes commonly implicated in GBM malignancy, such as MGMT, EGFR, PI3K-Akt signaling, and Ras/MAPK signaling are also upregulated in the PVN model. We describe the kinetics of gene expression within the PVN hydrogels over a course of 14 days, observing the patterns associated with tumor cell-mediated endothelial network co-option and regression. We finally examine the effect of temozolomide, a frontline chemotherapy used clinically against GBM, on the PVN culture. Notably, the PVN model is less responsive to TMZ compared to hydrogels containing only tumor cells. Overall, these results demonstrate that inclusion of cellular and matrix-associated elements of the PVN within an in vitro model of GBM allows for the development of gene expression patterns and therapeutic response relevant to GBM.

The Adenosine A₃ Receptor Regulates Differentiation of Glioblastoma Stem-Like Cells to Endothelial Cells under Hypoxia

Glioblastoma (GBM) is a neoplasm characterized by an extensive blood vessel network. Hypoxic niches of GBM can induce tumorigenic properties of a small cell subpopulation called Glioblastoma stem-like cells (GSCs) and can also increase extracellular adenosine generation which activates the A₃ adenosine receptor (A₃AR). Moreover, GSCs potentiates the persistent neovascularization in GBM. The aim of this study was to determine if A₃AR blockade can reduce the vasculogenesis mediated by the differentiation of GSCs to Endothelial Cells (ECs) under hypoxia. We evaluated the expression of endothelial cell markers (CD31, CD34, CD144, and vWF) by fluorescence-activated cell sorting (FACS), and vascular endothelial growth factor (VEGF) secretion by ELISA using MRS1220 (A₃AR antagonist) under hypoxia. We validate our results using U87MG-GSCs A₃AR knockout (GSCs^A3-KO). The effect of MRS1220 on blood vessel formation was evaluated in vivo using a subcutaneous GSCs-tumor model. GSCs increased extracellular adenosine production and A₃AR expression under hypoxia. Hypoxia also increased the percentage of GSCs positive for endothelial cell markers and VEGF secretion, which was in turn prevented when using MRS1220 and in GSCs^A3-KO. Finally, in vivo treatment with MRS1220 reduced tumor size and blood vessel formation. Blockade of A₃AR decreases the differentiation of GSCs to ECs under hypoxia and in vivo blood vessel formation.

NEO212 Inhibits Migration and Invasion of Glioma Stem Cells

Glioblastoma multiforme is a malignant brain tumor noted for its extensive vascularity, aggressiveness, and highly invasive nature, suggesting that cell migration plays an important role in tumor progression. The poor prognosis in GBM is associated with a high rate of tumor recurrence, and resistance to the standard of care chemotherapy, temozolomide (TMZ). The novel compound NEO212, a conjugate of TMZ and perillyl alcohol (POH), has proven to be 10-fold more cytotoxic to glioma stem cells (GSC) than TMZ, and is active against TMZ-resistant tumor cells. In this study, we show that NEO212 decreases migration and invasion of primary cultures of patient-derived GSCs, in both mesenchymal USC02 and proneural USC04 populations. The mechanism by which NEO212 reduces migration and invasion appears to be independent of its DNA alkylating effects, which cause cytotoxicity during the first hours of treatment, and is associated with a decrease in the FAK/Src signaling pathway, an effect not exhibited by TMZ. NEO212 also decreases the production of matrix metalloproteinases MMP2 and MMP9, crucial for GSC invasion. Gene expression analysis of epithelial and mesenchymal markers suggests that NEO212 increases the expression of epithelial-like characteristics, suggesting a reversion of the epithelial-to-mesenchymal transition process. Furthermore, in an in vivo orthotopic glioma model, NEO212 decreases tumor progression by reducing invasion of GSCs, thereby increasing survival time of mice. These studies indicate that NEO212, in addition to cytotoxicity, can effectively reduce migration and invasion in GSCs, thus exhibiting significant clinical value in the reduction of invasion and malignant glioma progression. Mol Cancer Ther; 17(3); 625-37. ©2018 AACR.

Long non-coding RNA H19 regulates glioma angiogenesis and the biological behavior of glioma-associated endothelial cells by inhibiting microRNA-29a

Long non-coding RNAs (lncRNAs) play crucial roles in the development and progression of glioma. Previous studies indicated that lncRNA H19 regulated tumor carcinogenesis, angiogenesis and metastasis. This study aimed to investigate its functional role in glioma-induced endothelial cell proliferation, migration and tube formation as well as its possible molecular mechanisms. H19 was up-regulated in microvessels from glioma tissues and glioma-associated endothelial cells (GEC) cultured in glioma conditioned medium. Knockdown of H19 suppressed glioma-induced endothelial cell proliferation, migration and tube formation in vitro and meanwhile up-regulated the expression of miR-29a. Bioinformatics analysis and luciferase reporter assay defined that H19 mediated the above effects via directly binding to miR-29a. In addition, miR-29a targeted 3'-UTR region of vasohibin 2 (VASH2) and decreased its expression. VASH2 has been identified as an angiogenic factor. Knockdown of H19 also decreased the VASH2 expression by up-regulating miR-29a. In conclusion, the results indicated that knockdown of H19 suppressed glioma induced angiogenesis by inhibiting microRNA-29a, which may modulate the onset of glioma by regulating biological behaviors of glioma vascular endothelial cells.

Phase II trial of irinotecan and metronomic temozolomide in patients with recurrent glioblastoma

This phase II study was conducted to determine the efficacy and safety of metronomic temozolomide (TMZ) in combination with irinotecan in glioblastoma (GB) at first relapse. Patients with GB at first relapse received TMZ 50 mg/m/2day divided into three doses, except for a single 100 mg/m2 dose, administered between 3 and 6 h before every irinotecan infusion. Irinotecan was given intravenously at the previously established dose of 100 mg/m2 on days 8 and 22 of 28-day cycles. Treatment was given for a maximum of nine cycles or until progression or unacceptable toxicity occurred. Vascular endothelial growth factor and its soluble receptor 1, thrombospondin-1, microparticles, and microparticle-dependent procoagulant activity were measured in blood before treatment. The primary objective was 6-month progression-free survival (PFS). Twenty-seven evaluable patients were enrolled. Six-month PFS was 20.8%. Median PFS was 11.6 weeks (95% confidence interval: 7.5-15.7). Stable disease was the best response for nine (37.5%) patients, with a median duration of 11.2 weeks (4.2-35.85 weeks). No differences in PFS or response were observed among patients who relapsed during or after completion of adjuvant TMZ. Grade 3/4 adverse events included lymphopenia (15%), fatigue, diarrhea and febrile neutropenia (3.7% each), lymphopenia, neutropenia, and nausea/vomiting (11.1% each). One patient died from pneumonia and one patient died from pulmonary thromboembolism. Pretreatment levels of angiogenesis biomarkers, microparticles, and microparticle-related procoagulant activity were elevated in patients compared with healthy volunteers. This regimen is feasible, but failed to improve the results obtained with other second-line therapies in recurrent GB.

A novel drug conjugate, NEO212, targeting proneural and mesenchymal subtypes of patient-derived glioma cancer stem cells

Glioblastoma multiforme (GBM), a highly malignant brain tumor, accounts for half of all gliomas. Despite surgery, radiation and chemotherapy, the median survival is between 12 and 15 months. The poor prognosis is due to tumor recurrence attributed to chemoresistant glioma cancer stem cells (GSCs). Here we examined the effects of a novel compound NEO212, which is composed of two covalently conjugated anti-cancer compounds - temozolomide (TMZ) and perillyl alcohol (POH), on GSCs expressing either the proneural or mesenchymal gene signatures. These GSCs were obtained from patient-derived tumor tissue. Our findings demonstrate that NEO212 is 10 fold more cytotoxic to GSCs than TMZ (standard-of-care). Furthermore, NEO212 is effective against both proneural and clinically aggressive mesenchymal GSC subtypes. The mechanism of NEO212 mediated-cytotoxicity is through double-strand DNA breaks and apoptosis. In vivo studies show that NEO212 significantly delays tumor growth of both proneural and mesenchymal tumor stem cell populations. Patient-derived GSCs and tumors derived from these cells are highly reflective of the heterogeneity in human GBM. The efficacy of NEO212 against both GSC subtypes indicates that NEO212 has great clinical potential to effectively target GBM.

Tumor vasculature and glioma stem cells: Contributions to glioma progression

Glioblastoma multiforme (GBM), the most malignant of brain tumors, is characterized by extensive vascularization and a high degree of invasion. The current standard of care is not very effective, resulting in tumor recurrence with patients rarely surviving over 2 years. This tumor recurrence is attributed to the presence of chemo and radiation resistant glioma stem cells (GSCs). These cells are associated with vascular niches which regulate GSC self-renewal and survival. Recent studies suggest that while blood vessels support glioma stem cells, these tumor cells in turn may regulate and contribute to the tumor vasculature by transdifferentiating into endothelial cells directly or through the secretion of regulatory growth factors such as vascular endothelial growth factor (VEGF) and hepatoma derived growth factor (HDGF). The relationship between the tumor vasculature and the glioma stem cells is the subject of this review.

Current evidence of temozolomide and bevacizumab in treatment of gliomas

OBJECTIVE

This review article summarizes in vitro, in vivo, and clinical evidence pertaining to temozolomide (TMZ) and bevacizumab (BEV) efficacy and mechanism of action in gliomas.

METHODS

Relevant publications published before June 2013 in PubMed database were reviewed.

RESULTS

Temozolomide and BEV are current chemotherapeutic agents treating patients with high-grade glioma, including glioblastoma. In vitro and in vivo studies have proposed discordant cell death pathways for TMZ as either apoptosis or autophagy using different experimental setting details or cell lines. In addition, BEV may cause cell death through hypoxia-induced autophagy or unspecific indirect effects on cancer cells. The complexity of cancer cells in glioma has contributed to their resistance of both chemotherapies. In clinical trials, overall survival duration in glioma patients with recurrence (8-9 months) is lower than that in newly diagnosed patients (12-15 months).

CONCLUSION

Our collected data support the addition of radiotherapy, BEV, and other targeted agents to TMZ treatment, indicating prolonged survival duration in newly diagnosed patients. However, the optimal regimen for treating high-grade glioma cannot be concluded without more clinical trials.

Effects of single or combined treatments with radiation and chemotherapy on survival and danger signals expression in glioblastoma cell lines

The success of chemo- and radiotherapy in glioblastoma multiforme, the most common and lethal primary brain tumour, could rely on the induction of immunogenic tumour cell death and on the induction of anticancer immune response. In this study we investigated cell survival to single treatments or combination of X-rays and temozolomide in glioblastoma cell lines (T98G and U251MG) and we attempted to identify danger signals (HMGB1 and HSP70) released by dying cells in the microenvironment that could activate antitumour immunity contributing to the therapeutic efficacy of conventional treatments. Our data suggest that HSP70 translocates from cytoplasm to extracellular environment after an increase in radiation dose and HMGB1 translocates from the nucleus to the cytoplasm and subsequently is released into the extracellular space, confirming a role of these proteins as signals released after radiation-induced damage in glioblastoma cells. We also could state that TMZ had limited effectiveness in activating HMGB1 and HSP70 signalling and, instead, an adjuvant effect was observed in some combined treatments, depending on schedule, cell line, and timing. A big challenge in tumour therapy is, therefore, to identify the most beneficial combination and chronology of multiple treatment options to contribute to the improvement of the therapeutic outcome.

Argonaute-2 promotes miR-18a entry in human brain endothelial cells

BACKGROUND

Cerebral arteriovenous malformation (AVM) is a vascular disease exhibiting abnormal blood vessel morphology and function. miR-18a ameliorates the abnormal characteristics of AVM-derived brain endothelial cells (AVM-BEC) without the use of transfection reagents. Hence, our aim was to identify the mechanisms by which miR-18a is internalized by AVM-BEC. Since AVM-BEC overexpress RNA-binding protein Argonaute-2 (Ago-2) we explored the clinical potential of Ago-2 as a systemic miRNA carrier.

METHODS AND RESULTS

Primary cultures of AVM-BEC were isolated from surgical specimens and tested for endogenous miR-18a levels using qPCR. Conditioned media (CM) was derived from AVM-BEC cultures (AVM-BEC-CM). AVM-BEC-CM significantly enhanced miR-18a internalization. Ago-2 was detected using western blotting and immunostaining techniques. Ago-2 was highly expressed in AVM-BEC; and siAgo-2 decreased miR-18a entry into brain-derived endothelial cells. Only brain-derived endothelial cells were responsive to the Ago-2/miR-18a complex and not other cell types tested. Secreted products (eg, thrombospondin-1 [TSP-1]) were tested using ELISA. Brain endothelial cells treated with the Ago-2/miR-18a complex in vitro increased TSP-1 secretion. In the in vivo angiogenesis glioma model, animals were treated with miR-18a in combination with Ago-2. Plasma was obtained and tested for TSP-1 and vascular endothelial growth factor (VEGF)-A. In this angiogenesis model, the Ago-2/miR-18a complex caused a significant increase in TSP-1 and decrease in VEGF-A secretion in the plasma.

CONCLUSIONS

Ago-2 facilitates miR-18a entry into brain endothelial cells in vitro and in vivo. This study highlights the clinical potential of Ago-2 as a miRNA delivery platform for the treatment of brain vascular diseases.

Ex vivo behaviour of human bone tumor endothelial cells

Cooperation between endothelial cells and bone in bone remodelling is well established. In contrast, bone microvasculature supporting the growth of primary tumors and metastasis is poorly understood. Several antiangiogenic agents have recently been undergoing trials, although an extensive body of clinical data and experimental research have proved that angiogenic pathways differ in each tumor type and stage. Here, for the first time, we characterize at the molecular and functional level tumor endothelial cells from human bone sarcomas at different stages of disease and with different histotypes. We selected a CD31⁺ subpopulation from biopsies that displayed the capability to grow as adherent cell lines without vascular endothelial growth factor (VEGF). Our findings show the existence in human primary bone sarcomas of highly proliferative endothelial cells expressing CD31, CD44, CD105, CD146 and CD90 markers. These cells are committed to develop capillary-like structures and colony formation units, and to produce nitric oxide. We believe that a better understanding of tumor vasculature could be a valid tool for the design of an efficacious antiangiogenic therapy as adjuvant treatment of sarcomas.

Concentration- and schedule-dependent effects of chemotherapy on the angiogenic potential and drug sensitivity of vascular endothelial cells

The anti-angiogenic activity of chemotherapy is both dose- and schedule-dependent. While conventional maximum tolerated dose (MTD) chemotherapy exerts only mild and reversible anti-angiogenic effects, low-dose metronomic (LDM) chemotherapy was developed to specifically target tumour angiogenesis. However, the long-term effects of either MTD or LDM chemotherapy on vascular endothelial cells have never been investigated. Here, we demonstrated that repeated exposure to MTD and LDM chemotherapy differentially impact on the angiogenic potential and chemosensitivity of immortalized endothelial cells. Repeated MTD vinblastine treatment of vascular endothelial cells led to an increased proliferation rate and resistance to paclitaxel. In contrast, repeated LDM treatment with vinblastine or etoposide impaired the angiogenic potential of endothelial cells and increased their chemosensitivity. This effect was associated with a significant decrease in βII- and βIII-tubulin expression. Functional analysis using siRNA showed that silencing the expression of βIII-tubulin in endothelial cells significantly decreased their capacity to form vascular structures and increased their sensitivity to the anti-angiogenic and vascular-disrupting effects of chemotherapy, whereas silencing βII-tubulin expression had no effect. Collectively our results show that LDM chemotherapy impairs the angiogenic potential of endothelial cells while increasing their chemosensitivity-an effect at least in part mediated by the down-regulation of βIII-tubulin expression. Furthermore, our study suggests that βIII-tubulin represents an attractive therapeutic target to increase the anti-angiogenic effects of chemotherapy and overall anti-tumour efficacy.

The impact of bevacizumab on temozolomide concentrations in intracranial U87 gliomas

PURPOSE

An important question in the sequencing of anti-cancer therapies in patients with glioblastoma (GBM) is whether concurrent anti-angiogenesis therapies improve or impair brain concentrations of concomitantly administered cytotoxic therapies. The purpose of this study is to assess the intratumoral disposition of temozolomide (TMZ) via microdialysis before and after bevacizumab in an intracranial GBM xenograft model.

METHODS

Microdialysis probes were placed within tumor and contralateral brain in athymic rats bearing U87 intracerebral gliomas. TMZ (50 mg/kg oral) was administered 10 days thereafter. Extracellular fluid (ECF) was collected for 6 h. BEV was administered (10 mg/kg IV), and TMZ was re-dosed (50 mg/kg oral) 36 h thereafter with additional ECF collection. All ECF samples were assessed for TMZ concentration with liquid chromatography-tandem mass spectrometry.

RESULTS

Tumor TMZ mean area under the concentration-time curve (AUC(0-∞)) was 3.35 μg h/mL pre-BEV. Post-BEV, tumor mean TMZ AUC(0-∞) was 3.98 μg h/mL. In non-tumor brain, mean TMZ AUC(0-∞) pre-BEV was 3.22 μg h/mL and post-BEV was 3.34 μg h/mL.

CONCLUSIONS

There were no statistically significant changes in TMZ pharmacokinetics before or after BEV in the athymic rat U87 intracranial glioma model. BEV and TMZ are being investigated as a combination therapy in several ongoing studies for patients with glioma. These data reassuringly suggest that BEV does not significantly change the ECF tumor concentrations of TMZ in either tumor-bearing or normal brain when dosed 36 h prior to TMZ.

Modulation of tumor tolerance in primary central nervous system malignancies

Central nervous system tumors take advantage of the unique immunology of the CNS and develop exquisitely complex stromal networks that promote growth despite the presence of antigen-presenting cells and tumor-infiltrating lymphocytes. It is precisely this immunological paradox that is essential to the survival of the tumor. We review the evidence for functional CNS immune privilege and the impact it has on tumor tolerance. In this paper, we place an emphasis on the role of tumor-infiltrating myeloid cells in maintaining stromal and vascular quiescence, and we underscore the importance of indoleamine 2,3-dioxygenase activity as a myeloid-driven tumor tolerance mechanism. Much remains to be discovered regarding the tolerogenic mechanisms by which CNS tumors avoid immune clearance. Thus, it is an open question whether tumor tolerance in the brain is fundamentally different from that of peripheral sites of tumorigenesis or whether it simply stands as a particularly strong example of such tolerance.

Standard of care therapy for malignant glioma and its effect on tumor and stromal cells

Glioblastoma is the most common and deadly of the primary central nervous system tumors. Recent advances in molecular characterization have subdivided these tumors into at least three main groups. In addition, these tumors are cellularly complex with multiple stromal cell types contributing to the biology of the tumor and treatment response. Because essentially all glioma patients are treated with radiation, various chemotherapies and steroids, the tumor that finally kills them has been modified by these treatments. Most of the investigation of the effects of therapy on these tumors has focused on the glioma cells per se. However, despite the importance of the stromal cells in these tumors, little has been done to understand the effects of treatment on stromal cells and their contribution to disease. Understanding how current standard therapy affects the biology of the tumor and the tumor stroma may provide insight into the mechanisms that are important to the inhibition of tumor growth as well as the biology of recurrent tumors.

Tumor exploits alternative strategies to achieve vascularization

Neoangiogenesis is crucial for solid tumor growth and invasion, as the vasculature provides metabolic support and access to the circulation. Current antiangiogenic therapies have been designed on the assumption that endothelial cells forming the tumor vasculature exhibit genetic stability. Recent studies demonstrate that this is not the case. Tumor endothelial cells possess a distinct phenotype, differing from normal endothelial cells at both molecular and functional levels. This challenges the concept that tumor angiogenesis exclusively depends on normal endothelial cell recruitment from the surrounding vascular network. Indeed, recent data suggest alternative strategies for tumor vascularization. It has been reported that tumor vessels may derive from an intratumor embryonic-like vasculogenesis. This condition might be due to differentiation of normal stem and progenitor cells of hematopoietic origin or resident in tissues. Cancer stem cells may also participate in tumor vasculogenesis by virtue of their stem and progenitor cell properties. Finally, normal endothelial cells might be reprogrammed to a proangiogenic or dedifferentiated phenotype by genetic information transmitted from the tumor trough apoptotic bodies, or following mRNA and microRNA transfer by exosomes and microvesicles. In this review, we discuss the different aspects of intratumor angiogenesis and vasculogenesis, the known mechanisms involved, and the possible implications for the response to antiangiogenic therapy.

Immunotherapy of brain cancers: the past, the present, and future directions

Treatment of brain cancers, especially high grade gliomas (WHO stage III and IV) is slowly making progress, but not as fast as medical researchers and the patients would like. Immunotherapy offers the opportunity to allow the patient's own immune system a chance to help eliminate the cancer. Immunotherapy's strength is that it efficiently treats relatively small tumors in experimental animal models. For some patients, immunotherapy has worked for them while not showing long-term toxicity. In this paper, we will trace the history of immunotherapy for brain cancers. We will also highlight some of the possible directions that this field may be taking in the immediate future for improving this therapeutic option.

Feasibility study of 21-day-on/7-day-off temozolomide in children with brain tumors

Temozolomide (TMZ) is an oral alkylating agent with proven antitumoral activity in preclinical and clinical studies in adults with high-grade glioma (HGG). However, only limited efficacy has been reported in children with HGG using the 5-day schedule. This study investigated the safety of administering TMZ to children and adolescents with brain tumors over an extended period. Extended schedules have been proven to overcome chemoresistance without any major toxicity. The toxicity of TMZ, administered at 70 mg/m(2)/day orally for 21 consecutive days every 28 days, was assessed in children with brain tumors. A total of 156 courses of TMZ were given to 17 patients (median age 12.5 years, range 1-17 years), who were recruited into the study. Eleven patients had progressive or relapsing disease, and six patients were newly diagnosed. In this cohort no cases of toxic death or nonhematological toxicity were reported. In comparison with the 5-day schedule, thrombocytopenia and neutropenia were noted to be less frequent. Grades 3 and 4 lymphopenia occurred in 10.8 and 22.4% of courses, respectively; among the lymphopenic patients there was one case of disseminated zoster (meningoencephalitis and cutaneous involvement), one case of rotavirus gastroenteritis, and two cases of herpetic stomatitis reported. The objective response rate was 11.8%. Overall, 82.3% of patients showed stable disease. The prolonged TMZ schedule appeared to be well tolerated, with few cases of neutropenia or thrombocytopenia recorded. Nevertheless, prolonged exposure to TMZ was associated with lymphopenia and may lead to a higher rate of viral infections.

Hsp90 as a gatekeeper of tumor angiogenesis: clinical promise and potential pitfalls

Tumor vascularization is an essential modulator of early tumor growth, progression, and therapeutic outcome. Although antiangiogenic treatments appear promising, intrinsic and acquired tumor resistance contributes to treatment failure. Clinical inhibition of the molecular chaperone heat shock protein 90 (Hsp90) provides an opportunity to target multiple aspects of this signaling resiliency, which may elicit more robust and enduring tumor repression relative to effects elicited by specifically targeted agents. This review highlights several primary effectors of angiogenesis modulated by Hsp90 and describes the clinical challenges posed by the redundant circuitry of these pathways. The four main topics addressed include (1) Hsp90-mediated regulation of HIF/VEGF signaling, (2) chaperone-dependent regulation of HIF-independent VEGF-mediated angiogenesis, (3) Hsp90-dependent targeting of key proangiogenic receptor tyrosine kinases and modulation of drug resistance, and (4) consideration of factors such as tumor microenvironment that pose several challenges for the clinical efficacy of anti-angiogenic therapy and Hsp90-targeted strategies.

Metronomic chemotherapy: new rationale for new directions

Tumor angiogenesis is recognized as a major therapeutic target in the fight against cancer. The key involvement of angiogenesis in tumor growth and metastasis has started to redefine chemotherapy and new protocols have emerged. Metronomic chemotherapy, which is intended to prevent tumor angiogenesis, is based on more frequent and low-dose drug administrations compared with conventional chemotherapy. The potential of metronomic chemotherapy was revealed in animal models a decade ago and the efficacy of this approach has been confirmed in the clinic. In the past 5 years, multiple clinical trials have investigated the safety and efficacy of metronomic chemotherapy in a variety of human cancers. While the results have been variable, clinical studies have shown that these new treatment protocols represent an interesting alternative for either primary systemic therapy or maintenance therapy. We review the latest clinical trials of metronomic chemotherapy in adult and pediatric cancer patients. Accumulating evidence suggests that the efficacy of such treatment may not only rely on anti-angiogenic activity. Potential new mechanisms of action, such as restoration of anticancer immune response and induction of tumor dormancy are discussed. Finally, we highlight the research efforts that need to be made to facilitate the optimal development of metronomic chemotherapy.

Y-box binding protein-1 is a novel molecular target for tumor vessels

Y-box binding protein-1 (YB-1) is a member of the cold shock protein family and functions in transcription and translation. Many reports indicate that YB-1 is highly expressed in tumor cells and is a marker for tumor aggressiveness and clinical prognosis. Here, we show clear evidence that YB-1 is expressed in the angiogenic endothelial cells of various tumors, such as glioblastoma, esophageal cancer, gastric cancer, colon cancer, and lung cancer, as well as in tumor cells. YB-1 was highly expressed in glomeruloid microvascular endothelial cells of brain tumors and microvessels in the desmoplastic region around multiple solid tumors. On the other hand, no or low YB-1 expression was observed in normal angiogenic endothelial cells from fetal kidney, newborn lung, and placenta. The endothelial cells in inflammatory regions of granulomas were also weakly labeled. Knockdown of YB-1 expression by small-interfering RNA induced G1 cell cycle arrest and inhibited the growth of human umbilical vein endothelial cells stimulated by growth factors. Taken together, YB-1 plays an important role in the growth of not only tumor cells but also tumor-associated endothelial cells, suggesting that YB-1 is a promising target for cancer therapy.

Inhibition of metalloproteinases derived from tumours: new insights in the treatment of human glioblastoma

Glioblastoma multiforme is the most commonly diagnosed malignant primary brain tumour in adults. Invasive behaviour is the pathological hallmark of malignant gliomas; consequently, its inhibition has been suggested as a therapeutic strategy. Tumour cell-derived gelatinases (matrix metalloproteinase-2, matrix metalloproteinase-9) can be considered prime factors in glioma invasiveness: their expression correlates with the progression and the degree of malignancy. Thus, broad spectrum matrix metalloproteinase inhibitors (MMP inhibitors) have been included in clinical trials. In the present study, the invasiveness, viability and progression of the human glioma cell line U87MG were investigated following treatment with N-O-isopropyl sulfonamido-based hydroxamates (compounds 1 and 2) as MMP-2 inhibitors used at nanomolar concentration. A standard broad spectrum MMP-inhibitor belonging to the classical tertiary sulfonamido-based hydroxamates family (CGS_27023A) was used too. The compounds 1 and 2 resulted in potent inhibition of cell invasiveness (P<0.0001) without affecting viability. In some clinical trials, the combined therapy of temozolomide (an alkylating agent used in glioma treatment) plus marimastat (a broad spectrum MMP inhibitor) has provided evidence of the importance of MMPs to tumor progression and invasiveness. On this basis, the effect on U87MG cells of a combined treatment with temozolomide, plus each of the two MMP inhibitors at nanomolar concentration, was investigated. The obtained data demonstrated the inhibition of cell invasiveness and viability after treatment. These results can help in developing clinical combined therapy using MMP inhibitors that, at low doses, increase the anticancer efficacy of chemotherapeutic drugs, probably without causing the side effects typical of broad-spectrum MMP inhibitors.