Manabu Seino

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.

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.

Activation of estrogen receptor alpha by estradiol and cisplatin induces platinum-resistance in ovarian cancer cells

ABSTRACT Activation of Estrogen receptor (ER) α (α) promotes cell growth and influences the response of cancer cell to chemotherapeutic agents. However, the mechanism by which ERα activation antagonizes cells to chemotherapy-induced cytotoxicity remains unclear. Here, we investigated the effect of cisplatin on ERα activation. In addition, we examined whether down-regulation of ERα modulate cisplatin-mediated cytotoxicity using 2 human ovarian cancer cells (Caov-3 and Ovcar-3) transduced with ERα short hairpin RNA (shRNA). The proliferation assay showed that 17β-estradiol (E2) induced cell proliferation via activation of Akt and extracellular signal-regulated kinase (ERK) cascades, while shRNA mediated downregulation of ERα inhibited the cell proliferation. Immunoblot analysis revealed that cisplatin induced the phosphorylation of ERα at serine 118 via ERK cascade. Luciferase assay showed that cisplatin increases transcriptional activity of estrogen-responsive element (ERE). The E2-stimulated ERα activation attenuated cisplatin-induced cytotoxicity. Meanwhile, down-regulation of ERα inhibited E2-induced protective effect on cisplatin toxicity as determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. Moreover, Pretreatment with E2 followed by cisplatin decreased the expression of cleaved PARP, and increased the expression of anti-apoptotic protein Bcl-2. Collectively, our findings suggest that activation of ERα by E2 and cisplatin can induce platinum-resistance by increasing the expression of anti-apoptotic protein in ovarian cancer cells. Therefore, our findings provide valuable information that ERα might be a promising therapeutic target for platinum-resistant ovarian cancer.

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.

Metabolomic analysis of uterine serous carcinoma with acquired resistance to paclitaxel

Introduction Uterine serous carcinoma (USC) is more aggressive than other subtypes of endometrial carcinoma and is associated with a poor prognosis. We analyzed the metabolomic profile of USC with acquired resistance to paclitaxel. Results Glutathione (GSH) concentration in PTX-1 cells was higher than in USPC-1 cells. In addition, GSH concentration in the USPC-1 cells increased after treatment with paclitaxel but was unchanged in PTX-1 cells. Glucose-6-phosphate (G6P) and ribose-5-phosphate (R5P) concentrations in PTX-1 cells were higher than those in USPC-1 cells. G6P concentration in the USPC-1 cells was unchanged after treatment with paclitaxel, while it decreased in PTX-1 cells. Conclusion Our results indicate that increased GSH and glucose metabolism may be related to acquiring resistance to paclitaxel in USC and thus may be targets for anti-USC therapy. Materials and Methods We compared metabolic profiles and reactions to paclitaxel in both a wild type USC cell line (USPC-1) and PTX-1, a cell line derived from USPC-1 which acquired paclitaxel resistance, using a capillary electrophoresis CE-MS/MS system.

Tumor lysis syndrome associated with docetaxel and carboplatin in a case with recurrent endometrial cancer

Tumor lysis syndrome (TLS) is an oncological life-threatening complication characterized by hyperuricemia, hyperphosphatemia, and hyperkalemia, which can lead to acute renal failure, cardiac arrhythmias, cardiac arrest and seizures. Although TLS is a rare complication in patients with non-hematological malignancy, the mortality rate of TLS in solid tumors is higher than that in hematological malignancies. Acute renal injury is the most common cause of mortality associated with TLS in solid tumors. We report a case of TLS following chemotherapy for a recurrent uterine serous carcinoma. In this case, we speculated that the cause of death might be a pulmonary tumor embolism caused by TLS.

Primary Chemotherapy and Targeted Molecular Therapy of Epithelial Ovarian Cancer

The use of paclitaxel in addition to cisplatin resulted in the improvement of ovarian cancer treatment. Based on the results of several randomized clinical trials (RCTs), the combination of paclitaxel and carboplatin administered every 3 weeks intravenously (IV) or a dose-dense regimen of weekly paclitaxel plus carboplatin demonstrates high clinical benefit and has become the standard primary chemotherapy. However, ovarian cancer remains the gynecological cancer with the highest mortality rate despite the establishment of highly effective chemotherapeutic regimens. One strategy to obtain further chemotherapeutic efficacy in the primary treatment of advanced ovarian cancer is neoadjuvant chemotherapy (NAC), and another is intraperitoneal (IP) chemotherapy. NAC is gaining acceptance in cases in which complete resection is not possible with only primary debulking surgery. IP therapy has been reported to be superior to conventional IV chemotherapy; on the other hand, there are complications specific to IP therapy. Several RCTs are currently underway to address these issues. In recent years, molecularly targeted drugs have been widely used in cancer treatment, and they currently play major roles in the treatment of ovarian cancer. In this article, the molecularly targeted therapy used in initial chemotherapy and subsequent maintenance therapy for ovarian cancer will be discussed.

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