Cancer-initiating enriched cell lines from human glioblastoma: preparing for drug discovery assays

A new tyrosine kinase inhibitor K905-0266 inhibits proliferation and sphere formation of glioblastoma cancer cells

Glioblastoma (GBM) is the most prevalent malignant tumour of the central nervous system and carries a poor prognosis; average survival time after diagnosis is 14 months. Because of its unfavourable prognosis, novel therapies are needed. The aim of this study was to assess whether inhibition of GBM and GBM-derived cancer stem cells (CSCs) by a new tyrosine kinase inhibitor (TKI), K905-0266, is possible. To do this, we generated GBM (D54 and U87MG) cells expressing luciferase and characterised the inhibitory effects of the TKI with bioluminescent imaging (BLI) and western blot (WB). The effect of the TKI was then evaluated in CSCs. BLI showed significant inhibition of D54 and U87MG cells by TKI treatment. WB showed that the TKI decreased pERK and Bcl-2 level and increased cleaved caspase-3 level. Sphere formation was significantly reduced by the TKI in CSCs. Our results showed that a new TKI, K905-0266, effectively inhibited GBM and CSCs, making this a candidate for GBM therapy.

Role of EZH2 in cancer stem cells: from biological insight to a therapeutic target

Epigenetic modifications in cancer stem cells largely result in phenotypic and functional heterogeneity in many solid tumors. Increasing evidence indicates that enhancer of zeste homolog 2 (EZH2), the catalytic subunit of Polycomb repressor complex 2, is highly expressed in cancer stem cells of numerous malignant tumors and has a critical function in cancer stem cell expansion and maintenance. Here, we review up-to-date information regarding EZH2 expression patterns, functions, and molecular mechanisms in cancer stem cells in various malignant tumors and discuss the therapeutic potential of targeting EZH2 in tumors.

Blocking epithelial-to-mesenchymal transition in glioblastoma with a sextet of repurposed drugs: the EIS regimen

This paper outlines a treatment protocol to run alongside of standard current treatment of glioblastoma- resection, temozolomide and radiation. The epithelial to mesenchymal transition (EMT) inhibiting sextet, EIS Regimen, uses the ancillary attributes of six older medicines to impede EMT during glioblastoma. EMT is an actively motile, therapy-resisting, low proliferation, transient state that is an integral feature of cancers’ lethality generally and of glioblastoma specifically. It is believed to be during the EMT state that glioblastoma’s centrifugal migration occurs. EMT is also a feature of untreated glioblastoma but is enhanced by chemotherapy, by radiation and by surgical trauma. EIS Regimen uses the antifungal drug itraconazole to block Hedgehog signaling, the antidiabetes drug metformin to block AMP kinase (AMPK), the analgesic drug naproxen to block Rac1, the anti-fibrosis drug pirfenidone to block transforming growth factor-beta (TGF-beta), the psychiatric drug quetiapine to block receptor activator NFkB ligand (RANKL) and the antibiotic rifampin to block Wnt- all by their previously established ancillary attributes. All these systems have been identified as triggers of EMT and worthy targets to inhibit. The EIS Regimen drugs have a good safety profile when used individually. They are not expected to have any new side effects when combined. Further studies of the EIS Regimen are needed.

Optimized creation of glioblastoma patient derived xenografts for use in preclinical studies

BACKGROUND

Glioblastoma multiforme (GBM) is the most common and lethal brain tumor in adults, highlighting the need for novel treatment strategies. Patient derived xenografts (PDX) represent a valuable tool to accomplish this task.

METHODS

PDX were established by implanting GBM tissue subcutaneously. Engraftment success was compared between NMRI Foxn1nu and NOD/SCID as well as between fresh and cryopreserved tissue. Established PDX were analyzed histologically and molecularly. Five PDX were experimentally treated with different drugs to assess their potential for preclinical drug testing.

RESULTS

Establishment of PDX was attempted for 36 consecutive GBM cases with an overall success rate of 22.2% in NMRI Foxn1nu mice. No difference was observed between fresh or cryopreserved (20-1057 days) tissue in direct comparison (n = 10 cases). Additionally, engraftment was better in NOD/SCID mice (38.8%) directly compared to NMRI Foxn1nu mice (27.7%) (n = 18 cases). Molecular data and histology of the PDX compare well to the primary GBM. The experimental treatment revealed individual differences in the sensitivity towards several clinically relevant drugs.

CONCLUSIONS

The use of vitally frozen GBM tissue allows a more convenient workflow without efficiency loss. NOD/SCID mice appear to be better suited for initial engraftment of tumor tissue compared to NMRI Foxn1nu mice.

Potential use of glioblastoma tumorsphere: clinical credentialing

A decade ago, cancer stem cells (CSCs) were introduced as target cells for an innovative cancer treatment. Particularly, there have been a lot of biological researches on glioblastoma (GBM) CSCs. However, as there is a comprehensive change in the concept of CSCs, it is required to review how the different CSCs for patients can be clinically used, or clinical credentialing, and summarize the possibilities of clinical credentialing. In this regard, this review aims to introduce the tumorsphere obtained from GBM specimen and summarize the clinical dilemma and clinically applicable areas.

Role of WW domain proteins WWOX in development, prognosis, and treatment response of glioma

Glioblastoma multiforme (GBM) is the most aggressive and malignant brain tumor. Delicate microenvironment and lineage heterogeneity of GBM cells including infiltration, hypoxia, angiogenesis, and stemness make them highly resistant to current conventional therapies, with an average life expectancy for GBM patients of less than 15 months. Poor response to cytotoxic agents of GBM cells remains the major challenge of GBM treatment. Resistance of GBM to clinical treatment is a result of genomic alternation and deregulated signaling pathways, such as p53 mutation and apoptosis signaling blockage, providing cancer cells more opportunities for survival rather than cell death. WW domain-containing oxidoreductase (WWOX) is a tumor suppressor gene, commonly downregulated in various types of tumors, including GBM. It has been found that the reintroduction of WWOX induced p53-mutant GBM cells to undergo apoptosis, but not in p53 wild-type GBM cells, indicating WWOX is likely to reopen apoptosis pathways in a p53-independent manner in GBM. Identifying the crucial target modulated by WWOX deficiency provides a potential therapeutic target for GBM treatment. Here, we have reviewed the literatures about the role of WWOX in development, signaling pathway, prognosis, and treatment response in malignant glioma.

Isolation of cancer stem cells from three human glioblastoma cell lines: characterization of two selected clones

Cancer stem cells (CSC) were isolated via a non-adherent neurosphere assay from three glioma cell lines: LI, U87, and U373. Using a clonal assay, two clones (D2 and F11) were selected from spheres derived from LI cells and were characterized for the: expression of stem cell markers (CD133, Nestin, Musashi-1 and Sox2); proliferation; differentiation capability (determined by the expression of GalC, βIII-Tubulin and GFAP); Ca²⁺ signaling and tumorigenicity in nude mice. Both D2 and F11 clones expressed higher levels of all stem cell markers with respect to the parental cell line. Clones grew more slowly than LI cells with a two-fold increase in duplication time. Markers of differentiation (βIII-Tubulin and GFAP) were expressed at high levels in both LI cells and in neurospheres. The expression of Nestin, Sox2, and βIII-Tubulin was down-regulated in D2 and F11 when cultured in serum-containing medium, whereas Musashi-1 was increased. In this condition, duplication time of D2 and F11 increased without reaching that of LI cells. D2, F11 and parental cells did not express voltage-dependent Ca²⁺-channels but they exhibited increased intracellular Ca²⁺ levels in response to ATP. These Ca²⁺ signals were larger in LI cells and in spheres cultured in serum-containing medium, while they were smaller in serum-free medium. The ATP treatment did not affect cell proliferation. Both D2 and F11 induced the appearance of tumors when ortotopically injected in athymic nude mice at a density 50-fold lower than that of LI cells. All these data indicate that both clones have characteristics of CSC and share the same stemness properties. The findings regarding the expression of differentiation markers and Ca²⁺-channels show that both clones are unable to reach the terminal differentiation. Both D2 and F11 might represent a good model to improve the knowledge on CSC in glioblastoma and to identify new therapeutic approaches.

Phenotypic screening in cancer drug discovery - past, present and future

There has been a resurgence of interest in the use of phenotypic screens in drug discovery as an alternative to target-focused approaches. Given that oncology is currently the most active therapeutic area, and also one in which target-focused approaches have been particularly prominent in the past two decades, we investigated the contribution of phenotypic assays to oncology drug discovery by analysing the origins of all new small-molecule cancer drugs approved by the US Food and Drug Administration (FDA) over the past 15 years and those currently in clinical development. Although the majority of these drugs originated from target-based discovery, we identified a significant number whose discovery depended on phenotypic screening approaches. We postulate that the contribution of phenotypic screening to cancer drug discovery has been hampered by a reliance on 'classical' nonspecific drug effects such as cytotoxicity and mitotic arrest, exacerbated by a paucity of mechanistically defined cellular models for therapeutically translatable cancer phenotypes. However, technical and biological advances that enable such mechanistically informed phenotypic models have the potential to empower phenotypic drug discovery in oncology.