The MDM2-p53 Axis Represents a Therapeutic Vulnerability Unique to Glioma Stem Cells

The prevention of tumor recurrence by the successful targeting of glioma stem cells endowed with a tumor-initiating capacity is deemed the key to the long-term survival of glioblastoma patients. Glioma stem cells are characterized by their marked therapeutic resistance; however, recent evidence suggests that they have unique vulnerabilities that may be therapeutically targeted. We investigated MDM2 expression levels in glioma stem cells and their non-stem cell counterparts and the effects of the genetic and pharmacological inhibition of MDM2 on the viability of these cells as well as downstream molecular pathways. The results obtained showed that MDM2 expression was substantially higher in glioma stem cells than in their non-stem cell counterparts and also that the inhibition of MDM2, either genetically or pharmacologically, induced a more pronounced activation of the p53 pathway and apoptotic cell death in the former than in the latter. Specifically, the inhibition of MDM2 caused a p53-dependent increase in the expression of BAX and PUMA and a decrease in the expression of survivin, both of which significantly contributed to the apoptotic death of glioma stem cells. The present study identified the MDM2-p53 axis as a novel therapeutic vulnerability, or an Achilles' heel, which is unique to glioma stem cells. Our results, which suggest that non-stem, bulk tumor cells are less sensitive to MDM2 inhibitors, may help guide the selection of glioblastoma patients suitable for MDM2 inhibitor therapy.

CEP-1347 Dually Targets MDM4 and PKC to Activate p53 and Inhibit the Growth of Uveal Melanoma Cells

Uveal melanoma (UM) is among the most common primary intraocular neoplasms in adults, with limited therapeutic options for advanced/metastatic disease. Since UM is characterized by infrequent p53 mutation coupled with the overexpression of MDM4, a major negative regulator of p53, we aimed to investigate in this study the effects on UM cells of CEP-1347, a novel MDM4 inhibitor with a known safety profile in humans. We also examined the impact of CEP-1347 on the protein kinase C (PKC) pathway, known to play a pivotal role in UM cell growth. High-grade UM cell lines were used to analyze the effects of genetic and pharmacological inhibition of MDM4 and PKC, respectively, as well as those of CEP-1347 treatment, on p53 expression and cell viability. The results showed that, at its clinically relevant concentrations, CEP-1347 reduced not only MDM4 expression but also PKC activity, activated the p53 pathway, and effectively inhibited the growth of UM cells. Importantly, whereas inhibition of either MDM4 expression or PKC activity alone failed to efficiently activate p53 and inhibit cell growth, inhibition of both resulted in effective activation of p53 and inhibition of cell growth. These data suggest that there exists a hitherto unrecognized interaction between MDM4 and PKC to inactivate the p53-dependent growth control in UM cells. CEP-1347, which dually targets MDM4 and PKC, could therefore be a promising therapeutic candidate in the treatment of UM.

Antagonizing MDM2 Overexpression Induced by MDM4 Inhibitor CEP-1347 Effectively Reactivates Wild-Type p53 in Malignant Brain Tumor Cells

The development of MDM4 inhibitors as an approach to reactivating p53 in human cancer is attracting increasing attention; however, whether they affect the function of MDM2 and how they interact with MDM2 inhibitors remain unknown. We addressed this question in the present study using CEP-1347, an inhibitor of MDM4 protein expression. The effects of CEP-1347, the genetic and/or pharmacological inhibition of MDM2, and their combination on the p53 pathway in malignant brain tumor cell lines expressing wild-type p53 were investigated by RT-PCR and Western blot analyses. The growth inhibitory effects of CEP-1347 alone or in combination with MDM2 on inhibition were examined by dye exclusion and/or colony formation assays. The treatment of malignant brain tumor cell lines with CEP-1347 markedly increased MDM2 protein expression, while blocking CEP-1347-induced MDM2 overexpression by genetic knockdown augmented the effects of CEP-1347 on the p53 pathway and cell growth. Blocking the MDM2-p53 interaction using the small molecule MDM2 inhibitor RG7112, but not MDM2 knockdown, reduced MDM4 expression. Consequently, RG7112 effectively cooperated with CEP-1347 to reduce MDM4 expression, activate the p53 pathway, and inhibit cell growth. The present results suggest the combination of CEP-1347-induced MDM2 overexpression with the selective inhibition of MDM2's interaction with p53, while preserving its ability to inhibit MDM4 expression, as a novel and rational strategy to effectively reactivate p53 in wild-type p53 cancer cells.

The Novel MDM4 Inhibitor CEP-1347 Activates the p53 Pathway and Blocks Malignant Meningioma Growth In Vitro and In Vivo

A significant proportion of meningiomas are clinically aggressive, but there is currently no effective chemotherapy for meningiomas. An increasing number of studies have been conducted to develop targeted therapies, yet none have focused on the p53 pathway as a potential target. In this study, we aimed to determine the in vitro and in vivo effects of CEP-1347, a small-molecule inhibitor of MDM4 with known safety in humans. The effects of CEP-1347 and MDM4 knockdown on the p53 pathway in human meningioma cell lines with and without p53 mutation were examined by RT-PCR and Western blot analyses. The growth inhibitory effects of CEP-1347 were examined in vitro and in a mouse xenograft model of meningioma. In vitro, CEP-1347 at clinically relevant concentrations inhibited MDM4 expression, activated the p53 pathway in malignant meningioma cells with wild-type p53, and exhibited preferential growth inhibitory effects on cells expressing wild-type p53, which was mostly mimicked by MDM4 knockdown. CEP-1347 effectively inhibited the growth of malignant meningioma xenografts at a dose that was far lower than the maximum dose that could be safely given to humans. Our findings suggest targeting the p53 pathway with CEP-1347 represents a novel and viable approach to treating aggressive meningiomas.

Domatinostat Targets the FOXM1-Survivin Axis to Reduce the Viability of Ovarian Cancer Cells Alone and in Combination with Chemotherapeutic Agents

The deregulation of the FOXM1 transcription factor is a key molecular alteration in ovarian cancer, contributing to the development and progression of ovarian cancer via activation of the target genes. As such, FOXM1 is a highly attractive therapeutic target in the treatment of ovarian cancer, but there has been no clinically tested FOXM1 inhibitor to date. We investigated in this study the effects of domatinostat, a class I-selective HDAC inhibitor currently in the clinical stage of development as a cancer therapeutic, on the expression of FOXM1 and viability of ovarian cancer cells. Cell viability, as well as protein and mRNA expression of FOXM1 and its transcriptional target survivin, was examined after domatinostat treatment of TOV21G and SKOV3 ovarian cancer cell lines in the absence or presence of cisplatin and paclitaxel. The effect of FOXM1 knockdown on survivin expression and those of genetic and pharmacological inhibition of survivin alone or in combination with the chemotherapeutic agents on cell viability were also examined. Domatinostat reduced the protein and mRNA expression of FOXM1 and survivin and also the viability of ovarian cancer cells alone and in combination with cisplatin or paclitaxel at clinically relevant concentrations. Knockdown experiments showed survivin expression was dependent on FOXM1 in ovarian cancer cells. Survivin inhibition was sufficient to reduce the viability of ovarian cancer cells alone and in combination with the chemotherapeutic agents. Our findings suggest that domatinostat, which effectively targets the FOXM1-survivin axis required for the viability of ovarian cancer cells, is a promising option for the treatment of ovarian cancer.

Givinostat Inhibition of Sp1-dependent MGMT Expression Sensitizes Glioma Stem Cells to Temozolomide

BACKGROUND/AIM

Givinostat is a pan-histone deacetylase (HDAC) inhibitor that has demonstrated excellent tolerability as well as efficacy in patients with polycythemia vera. Accumulating in vitro and in vivo evidence suggests givinostat is also promising as a therapeutic agent targeting glioma stem cells (GSCs), the cancer stem cells of glioblastoma (GBM) considered responsible for its intractable nature. However, it remains to be shown how givinostat impacts the therapeutic effects of temozolomide, a DNA-alkylating agent and the key component of GBM treatment given not only during postoperative radiotherapy but also thereafter as maintenance chemotherapy.

MATERIALS AND METHODS

The effects of givinostat and knockdown of O⁶-methylguanine-DNA methyltransferase (MGMT) or Sp1 on the mRNA and protein expression of relevant genes in human GSC lines were examined by RT-PCR and western blot analyses. The dye exclusion method was used to evaluate cell viability.

RESULTS

Givinostat enhanced the cytotoxic activity of temozolomide in GSC lines expressing MGMT, in which the MGMT expression was shown to contribute to their temozolomide resistance. Givinostat inhibited MGMT expression in GSCs and, in parallel, the expression of Sp1, a transcription factor involved in the control of MGMT promoter activity. Knockdown experiments demonstrated Sp1 expression was indeed required for MGMT expression in GSCs.

CONCLUSION

Givinostat, in addition to its own cytotoxic activity, sensitizes GSCs to temozolomide by inhibiting Sp1-dependent MGMT expression in GSCs. Combining givinostat with temozolomide could therefore be a rational therapeutic strategy to effectively eliminate GSCs and thus help overcome the therapy resistance of GBM.

ACT-19 A REPORT OF PHASE I PART OF PHASE I/II STUDY OF MAINTENANCE THERAPY WITH METFORMIN AND TEMOZOLOMIDE FOR GLIOBLASTOMA

Background

Glioblastoma (GBM) is an aggressive primary brain tumor with poor prognosis. One strategy for overcoming resistance is developing a new therapy targeting the cancer stem/initiating cells. We have shown that the antidiabetic drug metformin (MF) can induce differentiation of stem-like glioma-initiating cells and suppress tumor formation through AMPK-FOXO3 activation. We conducted a phase I/II study to examine the clinical effect of MF combined with standard maintenance temozolomide (TMZ). Here, we report the result of phase I part and the current status of phase II part.

Patients and Methods

Patients between 20 and 74 years of age with supratentorial GBM histologically diagnosed according to the World Health Organization 2016 classification were eligible. MF dose-escalation was planned using a 3 + 3 design. Dose-limiting toxicities (DLTs) were assessed during the first 6 weeks after MF initiation.

Results

Between February 2021 and January 2022, the first three patients were treated with 1,500 mg/day MF and the next four patients were treated with 2,250 mg/day MF, which is the maximum dose approved in Japan. The median age of the patients was 41 years. Three tumors (42.9 %) were IDH1/2 mutants and 4 (57.1 %) were IDH1/2 wild-types. No DLTs were observed. The most common adverse effects were appetite loss, nausea, and diarrhea, which were observed in three patients. All of them were manageable, with grade 1 or 2. Only one grade 3 seizure was reported, which was likely related to the tumor. Two patients experienced tumor progression at 6.0 and 6.1 months, and one died 12.2 months after initial surgery. The other five patients remained stable at the last follow-up.

Conclusion

MF dose of up to 2,250 mg/day combined with maintenance TMZ appeared to be well tolerated, and we proceeded to phase II study with 2,250 mg/day MF.

Metformin with Temozolomide for Newly Diagnosed Glioblastoma: Results of Phase I Study and a Brief Review of Relevant Studies

Glioblastoma (GBM) inevitably recurs due to a resistance to current standard therapy. We showed that the antidiabetic drug metformin (MF) can induce the differentiation of stem-like glioma-initiating cells and suppress tumor formation through AMPK-FOXO3 activation. In this study, we design a phase I/II study to examine the clinical effect of MF. We aim to determine a recommended phase II MF dose with maintenance temozolomide (TMZ) in patients with newly diagnosed GBM who completed standard concomitant radiotherapy and TMZ. MF dose-escalation was planned using a 3 + 3 design. Dose-limiting toxicities (DLTs) were assessed during the first six weeks after MF initiation. Three patients were treated with 1500 mg/day MF and four patients were treated with 2250 mg/day MF between February 2021 and January 2022. No DLTs were observed. The most common adverse effects were appetite loss, nausea, and diarrhea, all of which were manageable. Two patients experienced tumor progression at 6.0 and 6.1 months, and one died 12.2 months after initial surgery. The other five patients remained stable at the last follow-up session. The MF dose of up to 2250 mg/day combined with maintenance TMZ appeared to be well tolerated, and we proceeded to a phase II study with 2250 mg/day MF.

Inhibition of the Phospholipase Cε-c-Jun N-Terminal Kinase Axis Suppresses Glioma Stem Cell Properties

Glioma stem cells (GSCs), the cancer stem cells of glioblastoma multiforme (GBM), contribute to the malignancy of GBM due to their resistance to therapy and tumorigenic potential; therefore, the development of GSC-targeted therapies is urgently needed to improve the poor prognosis of GBM patients. The molecular mechanisms maintaining GSCs need to be elucidated in more detail for the development of GSC-targeted therapy. In comparison with patient-derived GSCs and their differentiated counterparts, we herein demonstrated for the first time that phospholipase C (PLC)ε was highly expressed in GSCs, in contrast to other PLC isoforms. A broad-spectrum PLC inhibitor suppressed the viability of GSCs, but not their stemness. Nevertheless, the knockdown of PLCε suppressed the survival of GSCs and induced cell death. The stem cell capacity of residual viable cells was also suppressed. Moreover, the survival of mice that were transplanted with PLCε knockdown-GSCs was longer than the control group. PLCε maintained the stemness of GSCs via the activation of JNK. The present study demonstrated for the first time that PLCε plays a critical role in maintaining the survival, stemness, and tumor initiation capacity of GSCs. Our study suggested that PLCε is a promising anti-GSC therapeutic target.

HDAC Class I Inhibitor Domatinostat Preferentially Targets Glioma Stem Cells over Their Differentiated Progeny

Cancer stem cells (CSCs) are in general characterized by higher resistance to cell death and cancer therapies than non-stem differentiated cancer cells. However, we and others have recently revealed using glioma stem cells (GSCs) as a model that, unexpectedly, CSCs have specific vulnerabilities that make them more sensitive to certain drugs compared with their differentiated counterparts. We aimed in this study to discover novel drugs targeting such Achilles’ heels of GSCs as anti-GSC drug candidates to be used for the treatment of glioblastoma, the most therapy-resistant form of brain tumors. Here we report that domatinostat (4SC-202), a class I HDAC inhibitor, is one such candidate. At concentrations where it showed no or minimal growth inhibitory effect on differentiated GSCs and normal cells, domatinostat effectively inhibited the growth of GSCs mainly by inducing apoptosis. Furthermore, GSCs that survived domatinostat treatment lost their self-renewal capacity. These results suggested that domatinostat is a unique drug that selectively eliminates GSCs not only physically by inducing cell death but also functionally by inhibiting their self-renewal. Our findings also imply that class I HDACs and/or LSD1, another target of domatinostat, may possibly have a specific role in the maintenance of GSCs and therefore could be an attractive target in the development of anti-GSC therapies.

ET-7 Roles for hENT1 and dCK in gemcitabine sensitivity and malignancy of meningioma

Background: High-grade meningiomas are aggressive tumors with high morbidity and mortality rates that frequently recur even after surgery and adjuvant radiotherapy. However, limited information is currently available on the biology of these tumors, and no alternative adjuvant treatment options exist. Although we previously demonstrated that high-grade meningioma cells were highly sensitive to gemcitabine in vitro and in vivo, the underlying molecular mechanisms remain unknown. Methods: We examined the roles of hENT1 (human equilibrative nucleoside transporter 1) and dCK (deoxycytidine kinase) in the gemcitabine sensitivity and growth of meningioma cells in vitro. Tissue samples from meningiomas (26 WHO grade I and 21 WHO grade II/III meningiomas) were immunohistochemically analyzed for hENT1 and dCK as well as for Ki-67 as a marker of proliferative activity. Results: hENT1 and dCK, which play critical roles in the intracellular transport and activation of gemcitabine, respectively, were responsible for the high gemcitabine sensitivity of high-grade meningioma cells and were strongly expressed in high-grade meningiomas. hENT1 expression was required for the proliferation and survival of high-grade meningioma cells and dCK expression. Furthermore, high hENT1 and dCK expression levels correlated with stronger tumor cell proliferative activity and shorter survival in meningioma patients. Conclusions: The present results suggest that hENT1 is a key molecular factor influencing the growth capacity and gemcitabine sensitivity of meningioma cells and also that hENT1, together with dCK, may be a viable prognostic marker for meningioma patients as well as a predictive marker of their responses to gemcitabine.

ET-6 Gemcitabine radiosensitization primes irradiated malignant meningioma cells for senolytic elimination by navitoclax

BACKGROUND: Malignant meningioma is an aggressive tumor that requires adjuvant radiotherapy after surgery, yet there has been no standard systemic therapy established so far. We have demonstrated that malignant meningioma cells are exquisitely sensitive to gemcitabine due to their increased expression of hENT1 and dCK, which play critical roles in the intracellular transport and activation of gemcitabine, respectively (Takeda et al. Oncotarget 8:90996, 2017; Yamamoto et al., Neuro-Oncol 23:945, 2021). Significantly, in support of our findings, the efficacy and safety of gemcitabine have recently been documented in a small case series of patients with recurrent meningiomas, which has further led to a phase 2 clinical trial to evaluate the efficacy of gemcitabine in recurrent high-grade meningiomas (Khaddar et al., South Asian J Cancer 9:261, 2020). Besides its efficacy as a single agent, gemcitabine reportedly has a radiosensitizing effect in pancreatic cancer. However, it remains unknown whether or how gemcitabine interacts with ionizing radiation (IR) in malignant meningioma cells. METHODS: We examined radiosensitization effects of gemcitabine using malignant meningioma cell lines and xenografts (s.c. and i.c.) and explored the underlying mechanisms. RESULTS: Gemcitabine sensitized malignant meningioma cells remarkably to IR through the induction of senescence both in vitro and in vivo. Gemcitabine augmented the intracellular production of reactive oxygen species (ROS) by IR, which, together with cell growth suppression/senescence induced by this combination, was inhibited by N-acetyl-cysteine, suggesting a pivotal role for ROS in these combinatorial effects. Navitoclax, a senolytic drug, further enhanced the effects of the combination of gemcitabine and IR in vitro and in vivo by strongly inducing apoptotic cell death in senescent cells. CONCLUSION: These results suggest that gemcitabine is not only a promising radiosensitizer for malignant meningioma but also creates in combination with IR a therapeutic vulnerability of senescent meningioma cells to senolytics. (submitted for publication)

Gemcitabine radiosensitization primes irradiated malignant meningioma cells for senolytic elimination by navitoclax

Background

Malignant meningioma is an aggressive tumor that requires adjuvant radiotherapy after surgery, yet there has been no standard systemic therapy established so far. We recently reported that malignant meningioma cells are highly sensitive to gemcitabine; however, it remains unknown whether or how gemcitabine interacts with ionizing radiation (IR) in malignant meningioma cells.

Methods

We examined the radiosensitization effects of gemcitabine using malignant meningioma cell lines and xenografts and explored the underlying mechanisms.

Results

Gemcitabine sensitized malignant meningioma cells to IR through the induction of senescence both in vitro and in vivo. Gemcitabine augmented the intracellular production of reactive oxygen species (ROS) by IR, which, together with cell growth suppression/senescence induced by this combination, was inhibited by N-acetyl-cysteine, suggesting a pivotal role for ROS in these combinatorial effects. Navitoclax, a senolytic drug that inhibits Bcl-2 proteins, further enhanced the effects of the combination of gemcitabine and IR by strongly inducing apoptotic cell death in senescent cells.

Conclusion

These results not only indicate the potential of gemcitabine as a candidate radiosensitizer for malignant meningioma, but also reveal a novel role for gemcitabine radiosensitization as a means to create a therapeutic vulnerability of senescent meningioma cells to senolytics.

Targeting Folate Metabolism Is Selectively Cytotoxic to Glioma Stem Cells and Effectively Cooperates with Differentiation Therapy to Eliminate Tumor-Initiating Cells in Glioma Xenografts

Glioblastoma (GBM) is one of the deadliest of all human cancers. Developing therapies targeting GBM cancer stem cells or glioma stem cells (GSCs), which are deemed responsible for the malignancy of GBM due to their therapy resistance and tumor-initiating capacity, is considered key to improving the dismal prognosis of GBM patients. In this study, we found that folate antagonists, such as methotrexate (MTX) and pemetrexed, are selectively cytotoxic to GSCs, but not to their differentiated counterparts, normal fibroblasts, or neural stem cells in vitro, and that the high sensitivity of GCSs to anti-folates may be due to the increased expression of RFC-1/SLC19A1, the reduced folate carrier that transports MTX into cells, in GSCs. Of note, in an in vivo serial transplantation model, MTX alone failed to exhibit anti-GSC effects but promoted the anti-GSC effects of CEP1347, an inducer of GSC differentiation. This suggests that folate metabolism, which plays an essential role specifically in GSCs, is a promising target of anti-GSC therapy, and that the combination of cytotoxic and differentiation therapies may be a novel and promising approach to effectively eliminate cancer stem cells.

Lurasidone Sensitizes Cancer Cells to Osimertinib by Inducing Autophagy and Reduction of Survivin

BACKGROUND/AIM

Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) are key drugs in cancer treatment due to their minor adverse effects and outstanding anticancer effects. However, drugs for overcoming EGFR-TKI resistance are not in clinical use so far. Therefore, to overcome resistance, we focused on lurasidone, a new antipsychotic drug, due to its mild adverse effect profile from the viewpoint of drug repositioning.

MATERIALS AND METHODS

We explored the effects of lurasidone alone or in combination with EGFR-TKI on the growth of osimertinib-resistant cancer cells the anti-apoptotic marker expression such as survivin, and autophagy levels by LC-3B expression.

RESULTS

Within a non-toxic concentration range in normal cells, lurasidone and osimertinib combination therapy showed a growth-inhibitory effect in osimertinib-resistant cancer cells in vitro and in vivo. Furthermore, lurasidone decreased survivin expression and mildly induced autophagy.

CONCLUSION

Lurasidone may increase the sensitivity to osimertinib in osimertinib-resistant cancer cells in drug repurposing.

Roles for hENT1 and dCK in gemcitabine sensitivity and malignancy of meningioma

Background

High-grade meningiomas are aggressive tumors with high morbidity and mortality rates that frequently recur even after surgery and adjuvant radiotherapy. However, limited information is currently available on the biology of these tumors, and no alternative adjuvant treatment options exist. Although we previously demonstrated that high-grade meningioma cells were highly sensitive to gemcitabine in vitro and in vivo, the underlying molecular mechanisms remain unknown.

Methods

We examined the roles of hENT1 (human equilibrative nucleoside transporter 1) and dCK (deoxycytidine kinase) in the gemcitabine sensitivity and growth of meningioma cells in vitro. Tissue samples from meningiomas (26 WHO grade I and 21 WHO grade II/III meningiomas) were immunohistochemically analyzed for hENT1 and dCK as well as for Ki-67 as a marker of proliferative activity.

Results

hENT1 and dCK, which play critical roles in the intracellular transport and activation of gemcitabine, respectively, were responsible for the high gemcitabine sensitivity of high-grade meningioma cells and were strongly expressed in high-grade meningiomas. hENT1 expression was required for the proliferation and survival of high-grade meningioma cells and dCK expression. Furthermore, high hENT1 and dCK expression levels correlated with stronger tumor cell proliferative activity and shorter survival in meningioma patients.

Conclusions

The present results suggest that hENT1 is a key molecular factor influencing the growth capacity and gemcitabine sensitivity of meningioma cells and also that hENT1, together with dCK, may be a viable prognostic marker for meningioma patients as well as a predictive marker of their responses to gemcitabine.

Therapeutic targeting of pancreatic cancer stem cells by dexamethasone modulation of the MKP-1-JNK axis

Postoperative recurrence from microscopic residual disease must be prevented to cure intractable cancers, including pancreatic cancer. Key to this goal is the elimination of cancer stem cells (CSCs) endowed with tumor-initiating capacity and drug resistance. However, current therapeutic strategies capable of accomplishing this are insufficient. Using in vitro models of CSCs and in vivo models of tumor initiation in which CSCs give rise to xenograft tumors, we show that dexamethasone induces expression of MKP-1, a MAPK phosphatase, via glucocorticoid receptor activation, thereby inactivating JNK, which is required for self-renewal and tumor initiation by pancreatic CSCs as well as for their expression of survivin, an anti-apoptotic protein implicated in multidrug resistance. We also demonstrate that systemic administration of clinically relevant doses of dexamethasone together with gemcitabine prevents tumor formation by CSCs in a pancreatic cancer xenograft model. Our study thus provides preclinical evidence for the efficacy of dexamethasone as an adjuvant therapy to prevent postoperative recurrence in patients with pancreatic cancer.

ML-09 The REAL-WORLD of Elderly PCNSL Therapy in Tohoku and Niigata Area According to Retrospective Analysis: A Collaborative Investigation of the Tohoku Brain Tumor Study Group

Introduction: Recently, the number of cases of primary central nervous system lymphoma in elderly patients(EL-PCNSL) has been increasing. However, the treatment may be insufficient because of poor performance status and pre- and posttreatment complications. Therefore, we analyzed the risk factors for EL-PCNSL in the Tohoku and Niigata areas of Japan and clarified the REAL-WORLD of EL-PCNSL therapy. Materials & Methods: We investigated surgical and nonsurgical cases of patients aged 71 years or older from eight facilities during the last 8 years. We analyzed patient information, radiotherapy/chemotherapy or not, PFS, OS, RRs, second-line therapy, pre- and posttreatment complications, outcomes, and risk factors for poor prognosis. The log-rank test was used for univariate analysis, and Cox regression analysis was used for a multivariate analysis of risk factors. Results: Of the 142 cases registered, five differed from PCNSL pathologically, three receiving BSC were excluded, 31 were treated without biopsy, three were treated based on CSF-findings, and 100 were treated with biopsy. Total 134 cases were followed. The median age was 76 years, pretreatment KPS was 50%, and 118 cases(88%) had 217 pretreatment complications. The treatment contents consisted of various combinations depending on the attending physician. The retrospective overall PFS was 16 months and OS was 24 months. In the early treatment phase, out of 16 cases with dropout, four tumor and four complication deaths occurred. There were 77 deaths(58%), 39 internal tumor deaths(51%), and 33 complication deaths(43%). Poor prognostic risk factors were <60% posttreatment KPS, complications involving pretreatment cardiovascular and central nervous system disease, posttreatment pneumonia or severe infection, and absence of radiation or chemotherapy. Conclusions: Pretreatment KPS did not affect poor outcomes, but posttreatment KPS <60% and pre- and posttreatment complications did. Radiotherapy and chemotherapy are reportedly effective, but additional research to clarify the details of these modalities is needed.

Molecular Features and Prognostic Factors of Pleomorphic Xanthoastrocytoma: A Collaborative Investigation of the Tohoku Brain Tumor Study Group

Pleomorphic xanthoastrocytoma (PXA) is a rare glial tumor, however, its histological differentiation from high-grade gliomas is often difficult. Molecular characteristics may contribute to a better diagnostic discrimination. Prognostic factors of PXA are also important but few relevant reports have been published. This study investigated the molecular features and prognostic factors of PXAs. Seven university hospitals participated in this study by providing retrospective clinical data and tumor samples of PXA cases between 1993 and 2014. Tumor samples were analyzed for immunohistochemical (IHC) neuronal and glial markers along with Ki67. The status of the BRAF and TERT promoter (TERTp) mutation was also evaluated using the same samples, followed by feature extraction of PXA and survival analyses. In all, 19 primary cases (17 PXA and 2 anaplastic PXA) were included. IHC examination revealed the stable staining of nestin and the close association of synaptophysin to NFP. Of the PXA cases, 57% had the BRAF mutation and only 7% had the TERTp mutation. On univariate analysis, age (≥60 years), preoperative Karnofsky performance status (KPS) (≤80%), and marked peritumoral edema were significantly associated with progression-free survival (PFS). No independent factor was indicated by the multivariate analysis. In conclusion, PXA was characterized by positive nestin staining and a few TERTp mutations. The neuronal differential marker and BRAF status may help in diagnosis. Patient age, preoperative KPS, and marked perifocal edema were associated with PFS. The present study is limited because of small number of cases and its retrospective nature. Further clinical study is needed.

Inhibition of Retinoblastoma Cell Growth by CEP1347 Through Activation of the P53 Pathway

BACKGROUND/AIM

Despite advances in treatment modalities, the visual prognosis of retinoblastoma still remains unsatisfactory, underscoring the need to develop novel therapeutic approaches.

MATERIALS AND METHODS

The effect on the growth of six human retinoblastoma cell lines and a normal human fibroblast cell line of CEP1347, a small-molecule kinase inhibitor originally developed for the treatment of Parkinson's disease and therefore with a known safety profile in humans, was examined. The role of the P53 pathway in CEP1347-induced growth inhibition was also investigated.

RESULTS

CEP1347 selectively inhibited the growth of retinoblastoma cell lines expressing murine double minute 4 (MDM4), a P53 inhibitor. Furthermore, CEP1347 reduced the expression of MDM4 and activated the P53 pathway in MDM4-expressing retinoblastoma cells, which was required for the inhibition of their growth by CEP1347.

CONCLUSION

We propose CEP1347 as a promising candidate for the treatment of retinoblastomas, where functional inactivation of P53 as a result of MDM4 activation is reportedly common.

Doxazosin, a Classic Alpha 1-Adrenoceptor Antagonist, Overcomes Osimertinib Resistance in Cancer Cells via the Upregulation of Autophagy as Drug Repurposing

Osimertinib, which is a third-generation epidermal growth factor receptor tyrosine kinase inhibitor, is an important anticancer drug because of its high efficacy and excellent safety profile. However, resistance against osimertinib is inevitable; therefore, therapeutic strategies to overcome the resistance are needed. Doxazosin, a classic quinazoline-based alpha 1-adrenoceptor antagonist is used to treat hypertension and benign prostatic hyperplasia with a known safety profile. The anticancer effects of doxazosin have been examined in various types of malignancies from the viewpoint of drug repositioning or repurposing. However, it currently remains unclear whether doxazosin sensitizes cancer cells to osimertinib. Herein, we demonstrated that doxazosin induced autophagy and enhanced the anticancer effects of osimertinib on the cancer cells and cancer stem cells of non-small cell lung cancer, pancreatic cancer, and glioblastoma at a concentration at which the growth of non-tumor cells was not affected. The osimertinib-sensitizing effects of doxazosin were suppressed by 3-methyladenine, an inhibitor of autophagy, which suggested that the effects of doxazosin were mediated by autophagy. The present study provides evidence for the efficacy of doxazosin as a combination therapy with osimertinib to overcome resistance against osimertinib.

Verteporfin inhibits oxidative phosphorylation and induces cell death specifically in glioma stem cells

Glioblastoma multiforme (GBM) is the most malignant primary brain tumour in adults. Since glioma stem cells (GSCs) are associated with therapeutic resistance as well as the initiation and recurrence in GBM, therapies targeting GSCs are considered to be effective for long-term survival in GBM. Several reports suggested that oxidative phosphorylation (OXPHOS) of cancer stem cells is important for their survival; however, the requirement of OXPHOS in GSCs remains unclear. Few effective and safe agents that target GSC mitochondria are available in clinical settings. In this study, we demonstrated that GSCs had high OXPHOS activity compared with isogenic differentiated GSCs and that GSC survival depended on their OXPHOS activity. Remarkably, we showed that complexes III and IV had broad therapeutic windows and that the expression levels of mitochondrial DNA-coded components of complexes III and IV were elevated in GSCs compared with differentiated GSCs. Moreover, our search of the Food and Drug Administration-approved drugs for those targeting GSC mitochondria revealed that verteporfin (Visudyne^® ), a drug approved for macular degeneration, was a novel GSC-specific cytotoxic compound that reduced OXPHOS activity. Importantly, the cytotoxic effect of verteporfin was specific to GSCs without any toxicity to normal cells, and the IC₅₀ of approximately 200 nm was ten times less than its maximum blood concentration in humans. Overall, these findings indicated that high mitochondrial OXPHOS of GSCs is a potential GSC-specific vulnerability and that clinically available drugs, such as verteporfin, might become novel GSC-specific cytotoxic agents.

Spironolactone, a Classic Potassium-Sparing Diuretic, Reduces Survivin Expression and Chemosensitizes Cancer Cells to Non-DNA-Damaging Anticancer Drugs

Spironolactone, a classical diuretic drug, is used to treat tumor-associated complications in cancer patients. Spironolactone was recently reported to exert anti-cancer effects by suppressing DNA damage repair. However, it currently remains unclear whether spironolactone exerts combinational effects with non-DNA-damaging anti-cancer drugs, such as gemcitabine and epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs). Using the cancer cells of lung cancer, pancreatic cancer, and glioblastoma, the combinational effects of spironolactone with gemcitabine and osimertinib, a third-generation EGFR-TKI, were examined in vitro with cell viability assays. To elucidate the underlying mechanisms, we investigated alterations induced in survivin, an anti-apoptotic protein, by spironolactone as well as the chemosensitization effects of the suppression of survivin by YM155, an inhibitor of survivin, and siRNA. We also examined the combinational effects in a mouse xenograft model. The results obtained revealed that spironolactone augmented cell death and the suppression of cell growth by gemcitabine and osimertinib. Spironolactone also reduced the expression of survivin in these cells, and the pharmacological and genetic suppression of survivin sensitized cells to gemcitabine and osimertinib. This combination also significantly suppressed tumor growth without apparent adverse effects in vivo. In conclusion, spironolactone is a safe candidate drug that exerts anti-cancer effects in combination with non-DNA-damaging drugs, such as gemcitabine and osimertinib, most likely through the suppression of survivin.

Brexpiprazole Reduces Survivin and Reverses EGFR Tyrosine Kinase Inhibitor Resistance in Lung and Pancreatic Cancer

BACKGROUND/AIM

Although epidermal growth factor receptor (EGFR) is frequently activated in lung and pancreatic cancers, the efficacy of EGFR tyrosine kinase inhibitors (EGFR-TKIs) is limited. Recently, brexpiprazole, an antipsychotic drug, was reported to chemosensitize glioma cells to osimertinib, a third-generation EGFR-TKI, by suppressing survivin, an anti-apoptotic protein, but their combinational effects on lung and pancreatic cancers remain unknown. The aim of this study was to examine the combinational effects of brexpiprazole and osimertinib on lung and pancreatic cancer cells in vitro and in vivo.

MATERIALS AND METHODS

YM155, a suppressor of survivin, siRNA, and immunoblot were used to examine the role of survivin in osimertinib-resistance. The effect of drugs on cell viability in vitro was examined by trypan blue staining. The in vivo effects of drugs on tumor growth were examined using a xenograft mouse model.

RESULTS

Brexpiprazole exerted combinational effects with osimertinib in vitro. Pharmacological and genetic suppression of survivin chemosensitized the cells to osimertinib. Moreover, the combination of brexpiprazole and osimertinib effectively suppressed tumor growth in a mouse xenograft model.

CONCLUSION

Brexpiprazole is a promising drug for lung and pancreatic cancer in combination with osimertinib.

In vitro and in vivo anti-tumor effects of brexpiprazole, a newly-developed serotonin-dopamine activity modulator with an improved safety profile

From the perspective of psycho-oncology, antipsychotics are widely used for patients with cancer. Although some antipsychotic drugs have anti-tumor effects, these antipsychotic drugs are not applicable for cancer patients because of their severe side effects. Brexpiprazole, a novel serotonin-dopamine modulator with an improved side effect profile, was developed as a drug that is structurally and pharmacologically related to aripiprazole, which was reported to have anti-cancer effects. However, it remains unknown whether brexpiprazole has anti-cancer effects. In this study, we examined whether brexpiprazole has anti-tumor effects in cancer cells and cancer stem cells (CSCs) of glioblastoma, pancreatic cancer, and lung cancer. Brexpiprazole suppressed cell growth and induced cell death in the cancer cells and the CSCs, and decreased the CSC properties of the CSCs. Brexpiprazole did not exert any cytotoxic effects on non-cancer cells at the anti-cancer effect-inducing concentration. In the cancer cells and the CSCs, brexpiprazole reduced the expression of survivin, an anti-apoptotic protein, whose reduction sensitizes tumor cells to chemotherapeutic reagents. In the preclinical model in which pancreatic CSCs were subcutaneously implanted into nude mice, brexpiprazole suppressed tumor growth, in addition to reducing the expression of Sox2, a marker for CSCs, and survivin. This suggests that brexpiprazole is a promising antipsychotic drug with anti-tumor effects and an improved safety profile.

AS602801 Sensitizes Ovarian Cancer Stem Cells to Paclitaxel by Down-regulating MDR1

BACKGROUND/AIM

AS602801, an anti-cancer stem cell (CSC) candidate drug, sensitizes ovarian CSCs to paclitaxel and carboplatin by reducing the expression of survivin, an anti-apoptotic protein. The aim of the study was to examine the effect of AS602801 on the expression of multi drug resistance protein 1 (MDR1).

MATERIALS AND METHODS

Using two ovarian CSC lines, A2780 CSLC and TOV-21G CSLC, mechanisms other than survivin down-regulation were examined by comparing the effects of AS602801 and YM155, an inhibitor of survivin. After screening for the expression of ATP-binding cassette (ABC) transporters with or without AS602801 treatment, the sensitivity of cells to paclitaxel, carboplatin, and cisplatin was examined following knockdown of the ABC transporter.

RESULTS

The combinational effect of AS602801 on paclitaxel was less dependent on survivin than the effect on carboplatin. AS602801 reduced the expression of MDR1, an ABC transporter. Knockdown of MDR1 sensitized the cells to paclitaxel, but not to carboplatin or cisplatin.

CONCLUSION

AS602801 chemosensitized ovarian CSCs to paclitaxel by reducing the expression of MDR1.

AS602801, an Anticancer Stem Cell Candidate Drug, Reduces Survivin Expression and Sensitizes A2780 Ovarian Cancer Stem Cells to Carboplatin and Paclitaxel

BACKGROUND

AS602801, a novel inhibitor of c-Jun N-terminal kinase (JNK), suppresses tumor initiation capacity and metastatic potential of cancer stem cells (CSCs). However, it remains unknown whether this inhibitor can chemosensitize CSCs.

MATERIALS AND METHODS

Using A2780 CSLC, a CSC line derived from ovarian cancer, this study examined the combinational effects of AS602801 and carboplatin or paclitaxel and explored the mechanism of those effects.

RESULTS

AS602801 chemosensitized A2780 CSLC cells to carboplatin and paclitaxel. With respect to the mechanism of chemosensitization, the expression of survivin, an anti-apoptotic protein, was reduced by AS602801. Pharmacological and genetic inhibition of survivin chemosensitized the cells to carboplatin and paclitaxel. Suppression of survivin by AS602801 was also observed in other types of CSCs and non-CSCs.

CONCLUSION

AS602801, which reduces survivin expression, can chemosensitize ovarian CSCs and is a candidate drug that targets the chemoresistance, tumor-initiating capacity and metastasis of CSCs.

AS602801, an Anti-Cancer Stem Cell Drug Candidate, Suppresses Gap-junction Communication Between Lung Cancer Stem Cells and Astrocytes

BACKGROUND/AIM

Cancer stem cells (CSCs) are associated with tumorigenesis, recurrence, and metastasis. Cell-cell communication via gap junctions (GJs) between metastatic cancer cells and astrocytes is necessary for brain metastasis. Agents targeting communication between CSCs and astrocytes are expected to suppress brain metastasis.

MATERIALS AND METHODS

Using the A549 CSC, a cancer stem-like cell derived from A549, we examined the effect of AS602801, an anti-cancer stem cell agent whose safety has been confirmed in a phase 2 clinical trial, on GJ communication and connexin expression using a dye-transfer assay and immunoblot analysis, respectively.

RESULTS

AS602801 specifically suppressed cell-cell communication in A549 CSCs without any suppression of GJ communication in astrocytes; it also decreased the expression of connexin 43, a constituent of GJs, in A549 CSCs.

CONCLUSION

The anti-cancer stem cell agent, AS602801, is a potential drug candidate against brain metastasis.

Involvement of GLUT1-mediated glucose transport and metabolism in gefitinib resistance of non-small-cell lung cancer cells

Use of epidermal growth factor receptor (EGFR) inhibitors represented by gefitinib and erlotinib has become the standard of treatment for non-small-cell lung cancers (NSCLCs) with activating EGFR mutations. However, the majority of NSCLCs, which overexpress EGFR without such mutations, are resistant to EGFR inhibitors, and the mechanism(s) behind such primary resistance of NSCLCs without activating EGFR mutations to EGFR inhibitors still remains poorly understood. Here in this study, we show that glucose metabolism mediated by GLUT1, a facilitative glucose transporter, is involved in gefitinib resistance of NSCLC cells. We found that GLUT1 expression and glucose uptake were increased in resistant NSCLC cells after gefitinib treatment and that genetic as well as pharmacological inhibition of GLUT1 sensitized not only NSCLC cells with primary resistance but also those with acquired resistance to gefitinib. In vivo, the combination of systemic gefitinib and a GLUT1 inhibitor, both of which failed to inhibit tumor growth when administered alone, significantly inhibited the growth of xenograft tumors formed by the implantation of NSCLC cells with wild-type EGFR (wt-EGFR). Since our data indicated that GLUT1 was similarly involved in erlotinib resistance, our findings suggest that the activity of GLUT1-mediated glucose metabolism could be a critical determinant for the sensitivity of NSCLC cells to EGFR inhibitors and that concurrent GLUT1 inhibition may therefore be a mechanism-based approach to treating NSCLCs resistant to EGFR inhibitors, including those with wt-EGFR.

A Small-molecule Kinase Inhibitor, CEP-1347, Inhibits Survivin Expression and Sensitizes Ovarian Cancer Stem Cells to Paclitaxel

BACKGROUND

Chemoresistance of cancer stem cells (CSCs) is considered a major cause of post-treatment recurrence that negatively impacts the prognosis of patients with ovarian cancer.

MATERIALS AND METHODS

Using CSCs derived from two different ovarian cancer cell lines, we searched for molecules implicated in the chemoresistance of ovarian CSCs and also drugs with which to target those molecules.

RESULTS

Knockdown of survivin overexpressed in ovarian CSCs resulted in increased sensitivity to paclitaxel. Treatment at clinically relevant concentrations with CEP-1347, a mixed lineage kinase inhibitor with a known safety profile in humans, reduced survivin expression in ovarian CSCs and sensitized them to paclitaxel.

CONCLUSION

Survivin overexpression plays a key role in the chemoresistance of ovarian CSCs. Introduction of CEP-1347, which targets survivin expression in ovarian CSCs, as a chemosensitizer for conventional ovarian cancer chemotherapy may serve as a rational and feasible approach for better management of ovarian cancer.

The novel JNK inhibitor AS602801 inhibits cancer stem cells in vitro and in vivo

A phase 2 clinical trial investigating the efficacy and safety of AS602801, a newly developed JNK inhibitor, in the treatment of inflammatory endometriosis is complete. We are now examining whether AS602801 acts against human cancer cells in vitro and in vivo. In vitro, AS602801 exhibited cytotoxicity against both serum-cultured non-stem cancer cells and cancer stem cells derived from human pancreatic cancer, non-small cell lung cancer, ovarian cancer and glioblastoma at concentrations that did not decrease the viability of normal human fibroblasts. AS602801 also inhibited the self-renewal and tumor-initiating capacity of cancer stem cells surviving AS602801 treatment. Cancer stem cells in established xenograft tumors were reduced by systemic administration of AS602801 at a dose and schedule that did not adversely affect the health of the tumor-bearing mice. These findings suggest AS602801 is a promising anti-cancer stem cell agent, and further investigation of the utility of AS602801 in the treatment of cancer seems warranted.

Olanzapine, an Atypical Antipsychotic, Inhibits Survivin Expression and Sensitizes Cancer Cells to Chemotherapeutic Agents

BACKGROUND/AIM

Olanzapine, an atypical antipsychotic, is now increasingly used as an off-label indication for the management of cancer patients with chemotherapy-induced nausea and vomiting (CINV). However, how olanzapine affects cancer cells per se remains poorly understood.

MATERIALS AND METHODS

The effects of olanzapine treatment and survivin knockdown, alone or in combination with chemotherapeutic agents, on survivin expression and cell viability were investigated in human cancer cell lines.

RESULTS

Olanzapine reduced survivin expression in lung and pancreatic cancer stem cell (CSC) lines and sensitized them to chemotherapeutic agents such as 5-fluorouracil, gemcitabine, and cisplatin in a survivin expression-dependent manner. Olanzapine also reduced survivin expression and chemosensitized serum-cultured, non-CSC ovarian cancer cells that expressed survivin.

CONCLUSION

Olanzapine may benefit cancer patients not only as an antiemetic for CINV, but also by enhancing the effects of chemotherapeutic agents through down-regulation of survivin, which has been implicated in multidrug chemoresistance.

Repositioning CEP-1347, a chemical agent originally developed for the treatment of Parkinson's disease, as an anti-cancer stem cell drug

CEP-1347 is a mixed lineage kinase inhibitor tested in a large-scale phase 2/3 clinical trial in early Parkinson’s disease, in which its safety and tolerability, but nevertheless not efficacy, was demonstrated. Here we identify by drug repositioning CEP-1347 as a potential anti-cancer stem cell drug. In vitro, CEP-1347 efficiently induced differentiation and inhibited the self-renewal and tumor-initiating capacities of human cancer stem cells from glioblastoma as well as from pancreatic and ovarian cancers at clinically-relevant concentrations, without impairing the viability of normal fibroblasts and neural stem cells. In vivo, a 10-day systemic administration of CEP-1347 at a dose that was less than 1/10 the mouse equivalent of the dose safely given to humans for 2 years was sufficient to effectively reduce tumor-initiating cancer stem cells within established tumors in mice. Furthermore, the same treatment protocol significantly extended the survival of mice receiving orthotopic implantation of glioma stem cells. Together, our findings suggest that CEP-1347 is a promising candidate for cancer stem cell-targeting therapy and that further clinical and preclinical studies are warranted to evaluate its efficacy in cancer treatment.

Licochalcone A specifically induces cell death in glioma stem cells via mitochondrial dysfunction

Glioblastoma multiforme is the most malignant primary intrinsic brain tumor. Glioma stem cells (GSCs) are associated with chemoradiotherapy resistance and the recurrence of glioblastomas after conventional therapy. The targeting of GSCs is potentially an effective treatment for the long‐term survival of glioblastoma patients. Licochalcone A, a natural chalconoid from licorice root, exerts anticancer effects; however, its effect on GSCs remains unknown. We found that Licochalcone A induced massive caspase‐dependent death in GSCs but not in differentiated GSCs nor normal somatic and neural stem cells. Prior to cell death, Licochalcone A caused mitochondrial fragmentation and reduced the membrane potential and ATP production in GSCs. Thus, Licochalcone A induces mitochondrial dysfunction and shows promise as an anticancer stem cell drug.

Impact of H3K27 Demethylase Inhibitor GSKJ4 on NSCLC Cells Alone and in Combination with Metformin

BACKGROUND

GSKJ4, an H3K27 demethylase inhibitor, reportedly exhibits antitumor activity against specific cancers harboring genetic alterations in genes encoding chromatin modulators. However, its potential as an anticancer agent against human cancers not associated with such genetic alterations, including non-small cell lung cancer (NSCLC), remains unknown.

MATERIALS AND METHODS

The effect of GSKJ4 on the growth of three NSCLC cell lines and normal lung fibroblasts was investigated using the WST-8, dye exclusion, and colony formation assays.

RESULTS

GSKJ4, alone and in combination with an anti-diabetic drug metformin, induced cell death and inhibited the growth of NSCLC cell lines efficiently at concentrations non-toxic to normal cells, irrespective of their genetic backgrounds (mutations in the KRAS, TP53 and EGFR genes) and also of their resistance to cisplatin and paclitaxel.

CONCLUSION

GSKJ4, being a promising anticancer agent for NSCLC, may be effective against a wider spectrum of cancers than previously thought.

Rho-Associated Protein Kinase (ROCK) Inhibitors Inhibit Survivin Expression and Sensitize Pancreatic Cancer Stem Cells to Gemcitabine

BACKGROUND

Targeting pathways regulating survivin expression, which has been implicated in multidrug resistance of cancer cells, is a promising strategy to overcome cancer chemoresistance. To date, the role of rho-associated protein kinases (ROCKs) in survivin expression remains largely unknown.

MATERIALS AND METHODS

The effects of ROCK inhibitors Y-27632 and fasudil on survivin expression and cell viability were determined by immunoblot analysis and dye exclusion, respectively, in PANC-1 CSLC, a cancer stem cell line derived from a serum-cultured, gemcitabine-sensitive pancreatic cancer cell line, PANC-1.

RESULTS

siRNA-mediated knockdown of survivin revealed that the gemcitabine resistance of PANC-1 CSLC was dependent on survivin expression. Both Y-27632 and fasudil, reduced survivin expression in PANC-1 CSLC cells and sensitized them to gemcitabine. ROCK inhibition also reduced survivin expression in various other human cancer cell lines.

CONCLUSION

Small molecule inhibitor-mediated targeting of ROCK may be a viable strategy to overcome cancer chemoresistance through down-regulation of survivin.

Aripiprazole, an Antipsychotic and Partial Dopamine Agonist, Inhibits Cancer Stem Cells and Reverses Chemoresistance

BACKGROUND

There is a growing interest in repurposing antipsychotic dopamine antagonists for cancer treatment; however, antipsychotics are often associated with an increased risk of fatal events. The anticancer activities of aripiprazole, an antipsychotic drug with partial dopamine agonist activity and an excellent safety profile, remain unknown.

MATERIALS AND METHODS

The effects of aripiprazole alone or in combination with chemotherapeutic agents on the growth, sphere-forming ability and stem cell/differentiation/chemoresistance marker expression of cancer stem cells, serum-cultured cancer cells from which they were derived, and normal cells were examined.

RESULTS

At concentrations non-toxic to normal cells, aripiprazole inhibited the growth of serum-cultured cancer cells and cancer stem cells. Furthermore, aripiprazole induced differentiation and inhibited sphere formation, as well as stem cell marker expression of cancer stem cells while inhibiting their survivin expression and sensitizing them to chemotherapeutic agents.

CONCLUSION

Repurposing aripiprazole as an anticancer stem cell drug may merit further consideration.

JNK suppression of chemotherapeutic agents-induced ROS confers chemoresistance on pancreatic cancer stem cells

Chemoresistance associated with cancer stem cells (CSCs), which is now being held responsible for the pervasive therapy resistance of pancreatic cancer, poses a major challenge to the successful management of this devastating malignancy. However, the molecular mechanism underlying the marked chemoresistance of pancreatic CSCs remains largely unknown. Here we show that JNK, which is upregulated in pancreatic CSCs and contributes to their maintenance, is critically involved in the resistance of pancreatic CSCs to 5-fluorouracil (5-FU) and gemcitabine (GEM). We found that JNK inhibition effectively sensitizes otherwise chemoresistant pancreatic CSCs to 5-FU and GEM. Significantly, JNK inhibition promoted 5-FU- and GEM-induced increase in intracellular reactive oxygen species (ROS), and scavenging intracellular ROS by use of N-acetylcysteine impaired JNK inhibition-mediated promotion of the cytotoxicity of 5-FU and GEM. Our findings thus suggest that JNK may contribute to the chemoresistance of pancreatic CSCs through prevention of chemotherapeutic agents-induced increase in intracellular ROS. Our findings also suggest that JNK inhibition combined with 5-FU- and/or GEM-based regimens may be a rational therapeutic approach to effectively eliminate pancreatic CSCs.

GSKJ4, A Selective Jumonji H3K27 Demethylase Inhibitor, Effectively Targets Ovarian Cancer Stem Cells

BACKGROUND/AIM

Global increase in the trimethylation of histone H3 at lysine 27 (H3K27me3) has been associated with the differentiation of normal stem cells and cancer cells, however, the role of H3K27me3 in the control of cancer stem cells (CSCs) remains poorly understood. We investigated the impact of increased H3K27me3 on CSCs using a selective H3K27 demethylase inhibitor GSKJ4.

MATERIALS AND METHODS

The effect of GSKJ4 on the viability as well as on the self-renewal and tumor-initiating capacity of CSCs derived from the A2780 human ovarian cancer cell line was examined.

RESULTS

GSKJ4 induced cell death in A2780 CSCs at a concentration non-toxic to normal human fibroblasts. GSKJ4 also caused loss of self-renewal and tumor-initiating capacity of A2780 CSCs surviving GSKJ4 treatment.

CONCLUSION

Our findings suggest that H3K27 methylation may have an inhibitory role in the maintenance of CSCs and that GSKJ4 may represent a novel class of CSC-targeting agents.

Time-staggered inhibition of JNK effectively sensitizes chemoresistant ovarian cancer cells to cisplatin and paclitaxel

Ovarian cancer is the most lethal gynecological malignancy, for which platinum- and taxane-based chemotherapy plays a major role. Chemoresistance of ovarian cancer poses a major obstacle to the successful management of this devastating disease; however, effective measures to overcome platinum and taxane resistance are yet to be established. In the present study, while investigating the mechanism underlying the chemoresistance of ovarian cancer, we found that JNK may have a key role in the resistance of ovarian cancer cells to cisplatin and paclitaxel. Importantly, whereas simultaneous application of a JNK inhibitor and either of the chemotherapeutic agents had contrasting effects for cisplatin (enhanced cytotoxicity) and paclitaxel (decreased cytotoxicity), JNK inhibitor treatment prior to chemotherapeutic agent application invariably enhanced the cytotoxicity of both drugs, suggesting that the basal JNK activity is commonly involved in the chemoresistance of ovarian cancer cells to cisplatin and paclitaxel in contrast to drug‑induced JNK activity which may have different roles for these two drugs. Furthermore, we confirmed using non-transformed human and rodent fibroblasts that sequential application of the JNK inhibitor and the chemotherapeutic agents did not augment their toxicity. Thus, our findings highlight for the first time the possible differential roles of the basal and induced JNK activities in the chemoresistance of ovarian cancer cells and also suggest that time‑staggered JNK inhibition may be a rational and promising strategy to overcome the resistance of ovarian cancer to platinum- and taxane-based chemotherapy.

Targeting the facilitative glucose transporter GLUT1 inhibits the self-renewal and tumor-initiating capacity of cancer stem cells

Increased glucose metabolism is now recognized as an emerging hallmark of cancer. Recent studies have shown that glucose metabolism is even more active in cancer stem cells (CSCs), a rare population of cancer cells with the capacity to self-renew and initiate tumors, and that CSCs are dependent on glycolysis for their survival/growth. However, the role of glucose metabolism in the control of their self-renewal and tumor-initiating capacity per se still remains obscure. Moreover, much remains unknown as to which of the numerous molecules involved in the glucose metabolism is suitable as a target to control CSCs. Here we demonstrate that the facilitative glucose transporter GLUT1 is essential for the maintenance of pancreatic, ovarian, and glioblastoma CSCs. Notably, we found that WZB117, a specific GLUT1 inhibitor, could inhibit the self-renewal and tumor-initiating capacity of the CSCs without compromising their proliferative potential in vitro. In vivo, systemic WZB117 administration inhibited tumor initiation after implantation of CSCs without causing significant adverse events in host animals. Our findings indicate GLUT1-dependent glucose metabolism has a pivotal role not only in the growth and survival of CSCs but also in the maintenance of their stemness and suggest GLUT1 as a promising target for CSC-directed cancer therapy.

Abstract 2228: Requirement of JNK signaling for self-renewal and tumor-initiating capacity of ovarian cancer stem cells

Background/Aim: Activation of the c-JUN N-terminal kinase (JNK) signaling pathway has been associated with poor survival of patients with ovarian cancer, but the role(s) and significance of JNK signaling in ovarian cancer cells remain poorly understood. Here in this study, we aimed to investigate the role of JNK specifically in ovarian cancer stem cells (CSCs).

Materials and Methods: The effect of JNK inhibition on the self-renewal (CSC marker expression, sphere-forming ability) and tumor-initiating capacity was examined in CSCs derived from A2780 human ovarian cancer cell line. JNK inhibition was achieved either pharmacologically or genetically by use of RNA interference.

Results: Both pharmacological and genetic targeting of JNK resulted in loss of self-renewal and tumor-initiating capacity of A2780 CSCs.

Conclusion: Our findings demonstrate, to our knowledge for the first time, that JNK has a pivotal role in the maintenance of ovarian CSCs.

Citation Format: Manabu Seino, Masashi Okada, Keita Shibuya, Shizuka Seino, Shuhei Suzuki, Hiroyuki Takeda, Tsuyoshi Ohta, Hirohisa Kurachi, Kiyoshi Ito, Satoru Nagase, Chifumi Kitanaka. Requirement of JNK signaling for self-renewal and tumor-initiating capacity of ovarian cancer stem cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2228. doi:10.1158/1538-7445.AM2015-2228

Targeting the K-Ras--JNK axis eliminates cancer stem-like cells and prevents pancreatic tumor formation

Cancer cells with self-renewal and tumor-initiating capacity, either quiescent (cancer stem cells, CSCs) or proliferating (cancer stem-like cells, CSLCs), are now deemed responsible for the pervasive therapy resistance of pancreatic cancer, one of the deadliest human cancers characterized by high prevalence of K-Ras mutation. However, to date, much remains unknown how pancreatic CSCs/CSLCs are regulated. Here we show that the K-Ras – JNK axis plays a pivotal role in the maintenance of pancreatic CSCs/CSLCs. In vitro inhibition of JNK, either pharmacological or genetic, caused loss of the self-renewal and tumor-initiating capacity of pancreatic CSLCs. Importantly, JNK inhibition in vivo via systemic JNK inhibitor administration, which had no discernible effect on the general health status of mice, efficiently depleted the CSC/CSLC population within pre-established pancreatic tumor xenografts. Furthermore, knockdown of K-Ras in pancreatic CSLCs with K-Ras mutation led to downregulation of the JNK pathway as well as in loss of self-renewal and tumor-initiating capacity. Together, our findings suggest that pancreatic CSCs/CSLCs are dependent on K-Ras activation of JNK and also suggest that the K-Ras – JNK axis could be a potential target in CSC/CSLC-directed therapies against pancreatic cancer.

Differential contribution of ROS to resveratrol-induced cell death and loss of self-renewal capacity of ovarian cancer stem cells

BACKGROUND/AIM

Cancer stem cells (CSCs) are considered to contribute to the poor prognosis of ovarian cancer as a major cause of fatal recurrence. Identification of effective measures to eliminate ovarian CSCs through induction of cell death and/or loss of self-renewal capacity would, therefore, be key to successful management of ovarian cancer.

MATERIALS AND METHODS

The effects of resveratrol on the viability and self-renewal capacity of CSCs derived from A2780 human ovarian cancer cells were examined. The involvement of reactive oxygen species (ROS) was also investigated.

RESULTS

At a non-toxic to normal human fibroblasts concentration, resveratrol effectively killed ovarian CSCs independently of ROS, while ROS-dependently impaired the self-renewal capacity of ovarian CSCs that survived resveratrol treatment.

CONCLUSION

Our findings not only shed light on a novel mechanism of action for resveratrol but also suggest that resveratrol, or its analogs, may be useful for CSC-directed therapy against ovarian cancer.

Requirement of JNK signaling for self-renewal and tumor-initiating capacity of ovarian cancer stem cells

BACKGROUND/AIM

Activation of the c-JUN N-terminal kinase (JNK) signaling pathway has been associated with poor survival of ovarian cancer patients, but the role(s) and significance of JNK signaling in ovarian cancer cells remain poorly understood. In the present study, we aimed to investigate the role of JNK specifically in ovarian cancer stem cells (CSCs).

MATERIALS AND METHODS

The effect of JNK inhibition on the self-renewal (CSC marker expression, sphere-forming ability) and tumor-initiating capacity was examined in CSCs derived from the A2780 human ovarian cancer cell line. JNK inhibition was achieved either pharmacologically or genetically by use of RNA interference.

RESULTS

Both pharmacological and genetic targeting of JNK resulted in loss of self-renewal and tumor-initiating capacity of A2780 CSCs.

CONCLUSION

Our findings demonstrate, to our knowledge for the first time, that JNK has a pivotal role in the maintenance of ovarian CSCs.

JNK Signaling in the Control of the Tumor-Initiating Capacity Associated with Cancer Stem Cells

Deregulation of c-Jun NH2-terminal kinase (JNK) signaling occurs frequently in a variety of human cancers, yet the exact role(s) of JNK deregulation in cancer cell biology remains to be fully elucidated. Our recent demonstration that the activity of JNK is required not only for self-renewal of glioma stem cells but also for their tumor initiation has, however, identified a new role for JNK in the control of the stemness and tumor-initiating capacity of cancer cells. Significantly, transient JNK inhibition was sufficient to cause sustained loss of the tumor-initiating capacity of glioma stem cells, suggesting that the phenotype of "lost tumor-initiating capacity" may be as stable as the differentiated state and that the tumor-initiating capacity might therefore be under the control of JNK through an epigenetic mechanism that also governs stemness and differentiation. Here, in this article, we review the role and mechanism of JNK in the control of this "stemness-associated tumor-initiating capacity" (STATIC), a new hypothetical concept we introduce in this review article. Since the idea of STATIC is essentially applicable to both cancer types that do and do not follow the cancer stem cell hypothesis, we also give consideration to the possible involvement of JNK-mediated control of STATIC in a wide range of human cancers in which JNK is aberrantly activated. Theoretically, successful targeting of STATIC through JNK could contribute to long-term control of cancer. Issues to be considered before clinical application of therapies targeting this JNK-STATIC axis are also discussed.

Flotillin-1 regulates oncogenic signaling in neuroblastoma cells by regulating ALK membrane association

Neuroblastomas harbor mutations in the nonreceptor anaplastic lymphoma kinase (ALK) in 8% to 9% of cases where they serve as oncogenic drivers. Strategies to reduce ALK activity offer clinical interest based on initial findings with ALK kinase inhibitors. In this study, we characterized phosphotyrosine-containing proteins associated with ALK to gain mechanistic insights in this setting. Flotillin-1 (FLOT1), a plasma membrane protein involved in endocytosis, was identified as a binding partner of ALK. RNAi-mediated attenuation of FLOT1 expression in neuroblastoma cells caused ALK dissociation from endosomes along with membrane accumulation of ALK, thereby triggering activation of ALK and downstream effector signals. These features enhanced the malignant properties of neuroblastoma cells in vitro and in vivo. Conversely, oncogenic ALK mutants showed less binding affinity to FLOT1 than wild-type ALK. Clinically, lower expression levels of FLOT1 were documented in highly malignant subgroups of human neuroblastoma specimens. Taken together, our findings suggest that attenuation of FLOT1-ALK binding drives malignant phenotypes of neuroblastoma by activating ALK signaling.

JNK contributes to temozolomide resistance of stem-like glioblastoma cells via regulation of MGMT expression

While elimination of the cancer stem cell population is increasingly recognized as a key to successful treatment of cancer, the high resistance of cancer stem cells to conventional chemoradiotherapy remains a therapeutic challenge. O6-methylguanine DNA methyltransferase (MGMT), which is frequently expressed in cancer stem cells of glioblastoma, has been implicated in their resistance to temozolomide, the first-line chemotherapeutic agent against newly diagnosed glioblastoma. However, much remains unknown about the molecular regulation that underlies MGMT expression and temozolomide resistance of glioblastoma cancer stem cells. Here, we identified JNK as a novel player in the control of MGMT expression and temozolomide resistance of glioblastoma cancer stem cells. We showed that inhibition of JNK, either pharmacologically or by RNA interference, in stem-like glioblastoma cells derived directly from glioblastoma tissues reduces their MGMT expression and temozolomide resistance. Importantly, sensitization of stem-like glioblastoma cells to temozolomide by JNK inhibition was dependent on MGMT expression, implying that JNK controls temozolomide resistance of stem-like glioblastoma cells through MGMT expression. Our findings suggest that concurrent use of JNK inhibitors with temozolomide may be a rational therapeutic approach to effectively target the cancer stem cell population in the treatment of glioblastoma.

Specific role of JNK in the maintenance of the tumor-initiating capacity of A549 human non-small cell lung cancer cells

Deregulation of c-Jun NH2-terminal kinase (JNK) signaling is now increasingly reported in a variety of human malignancies. Non-small cell lung cancer (NSCLC) is among such human malignancies with aberrant JNK activation; yet the exact role(s) of JNK deregulation in NSCLC biology, in particular in vivo, remains unclear. Here, we demonstrated a specific role of JNK in the control of the tumor-initiating capacity of A549 cells derived from human lung adenocarcinoma, a major subtype of NSCLC. Despite its potent inhibitory activity on A549 cell growth in vitro, SP600125, a reversible JNK inhibitor, failed to inhibit the growth of pre-established A549 xenografts in vivo when systemically administered. Nevertheless, the same SP600125 treatment caused a marked reduction in the tumor-initiating population within the A549 tumors, suggesting that JNK may be specifically required in vivo for the maintenance of the tumor-initiating population of tumor cells rather than for proliferation and survival of the entire cell population. Furthermore, A549 cells either pre-treated with SP600125 or transiently transfected with siRNAs against the JNK genes in vitro showed substantially reduced ability to initiate tumor formation upon implantation into nude mice, implying that the cell intrinsic JNK activity of A549 cells is essential for the maintenance of their tumor-initiating capacity. To our knowledge, this is the first demonstration that JNK is involved in the control of the tumor-initiating capacity of NSCLC cells. Our findings also give rise to an intriguing possibility that therapies targeting JNK could contribute to prevention of relapse and/or metastasis of NSCLC through elimination of tumor-initiating cells.