Hiroshi Koutoku

YM155, a novel survivin suppressant, enhances taxane-induced apoptosis and tumor regression in a human Calu 6 lung cancer xenograft model.

Survivin, an apoptotic inhibitor, is overexpressed in the majority of human tumor types and represents a novel target for anticancer therapy. Taxanes induce a mitotic cell-cycle block through the inhibition of microtubule depolymerization, with subsequent elevated expression/stabilization of survivin. We investigated the administration of survivin suppressant YM155 monobromide (YM155), in combination with docetaxel, in a human non-small-cell lung cancer (NSCLC) xenograft model. Animals received a 7-day continuous infusion of YM155, 2 mg/kg, and/or three bolus doses of docetaxel, 20 mg/kg, according to three dosing schedules: YM155 administered concomitantly with docetaxel, before docetaxel, and after docetaxel. YM155 administered either concomitantly with or before docetaxel showed significant antitumor activity (tumor regression ≥99%), with complete regression of the established human NSCLC-derived tumors in mice (eight of eight and seven of eight animals, respectively). Significantly fewer complete responses (three of eight animals) were achieved when YM155 was administered after docetaxel. No statistically significant decreases in body weight were observed in the combination versus docetaxel groups. YM155 administered concomitantly with docetaxel resulted in significant decreases in mitotic and proliferative indices, and in a significant increase in the apoptosis index. Elevated survivin expression was seen in tumors from mice treated with docetaxel alone; a significant reduction in survivin expression was seen in tumors from mice treated with YM155 alone or in combination with docetaxel, but not in the control group. These results indicate that in a human NSCLC xenograft model YM155 in combination with docetaxel diminished the accumulation of survivin by docetaxel and induced more intense apoptosis and enhanced antitumor activity, compared with single-agent YM155 or docetaxel.

Sepantronium Bromide (YM155) induces disruption of the ILF3/p54nrb complex, which is required for survivin expression

YM155, a small-molecule survivin suppressant, specifically binds to the transcription factor ILF3, which regulates the expression of survivin[1]. In this experiment we have demonstrated that p54(nrb) binds to the survivin promoter and regulates survivin expression. p54(nrb) forms a complex with ILF3, which directly binds to YM155. YM155 induces disruption of the ILF3/p54(nrb) complex, which results in a different subcellular localization between ILF3 and p54(nrb). Thus, identification of molecular targets of YM155 in suppression of the survivin pathway, might lead to development of its use as a novel potential target in cancers.

Interleukin Enhancer-binding Factor 3/NF110 Is a Target of YM155, a Suppressant of Survivin

Survivin is responsible for cancer progression and drug resistance in many types of cancer. YM155 selectively suppresses the expression of survivin and induces apoptosis in cancer cells in vitro and in vivo. However, the mechanism underlying these effects of YM155 is unknown. Here, we show that a transcription factor, interleukin enhancer-binding factor 3 (ILF3)/NF110, is a direct binding target of YM155. The enhanced survivin promoter activity by overexpression of ILF3/NF110 was attenuated by YM155 in a concentration-dependent manner, suggesting that ILF3/NF110 is the physiological target through which YM155 mediates survivin suppression. The results also show that the unique C-terminal region of ILF3/NF110 is important for promoting survivin expression and for high affinity binding to YM155.

YM155, a selective survivin suppressant, inhibits tumor spread and prolongs survival in a spontaneous metastatic model of human triple negative breast cancer.

Metastatic triple negative breast cancer [TNBC, with negative expression of estrogen and progesterone receptors and no overexpression of HER2/neu (ErbB-2)] remains a major therapeutic challenge because of its poor overall prognosis and lack of optimal targeted therapies. Survivin has been implicated as an important mediator of breast cancer cell growth and dysfunctions in apoptosis, and its expression correlates with a higher incidence of metastases and patient mortality; thus, survivin is an attractive target for novel anti-cancer agents. In previous studies, we identified YM155 as a small molecule that selectively suppresses survivin expression. YM155 inhibits the growth of a wide range of human cancer cell lines. Tumor regression induced by YM155 is associated with decreased intratumoral survivin expression, increased apoptosis and a decreased mitotic index. In the present study, we evaluated the antitumor efficacy of YM155 both in vitro and in vivo using preclinical TNBC models. We found that YM155 suppressed survivin expression, including that of its splice variants (survivin 2B, δEx3 and 3B), resulting in decreased cellular proliferation and spontaneous apoptosis of human TNBC cells. In a mouse xenograft model, continuous infusion of YM155 led to the complete regression of subcutaneously established tumors. Furthermore, YM155 reduced spontaneous metastases and significantly prolonged the survival of animals bearing established metastatic tumors in the MDA-MB-231-Luc-D3H2-LN orthotopic model. These results suggest that the survivin-suppressing activity of YM155 may offer a novel therapeutic option for patients with metastatic TNBC.

Antitumor effects of YM155, a novel survivin suppressant, against human aggressive non-Hodgkin lymphoma.

YM155, a novel small-molecule that down-regulates survivin, exhibits broad, potent antitumor activity against a range of human tumors. We evaluated the activity of YM155 in aggressive non-Hodgkin lymphoma. In a number of diffuse large B-cell lymphoma lines, YM155 exhibited 50% growth inhibition with values between 0.23 and 3.9 nM. Within in vivo xenograft models, continuous infusion of YM155 eradicated large, established subcutaneous WSU-DLCL-2 and Ramos tumors, with sustained efficacy observed through 4 cycles of YM155 therapy. YM155 increased survival significantly versus rituximab in disseminated Ramos models. This study suggests that YM155 may represent an effective treatment for aggressive lymphomas.

Stabilization of androgen receptor protein is induced by agonist, not by antagonists ☆

The action of nuclear receptor ligands in target tissues is specified mainly by the expression levels of their cognate nuclear receptors. The expression levels of these receptors are controlled through transcriptional and post-transcriptional events. Among post-transcriptional events, the effect of ligand on nuclear receptor protein turnover still remains largely unknown. Therefore, we studied the effects of agonist and antagonists on the turnover of the human androgen receptor (hAR) protein in stably transformed Chinese hamster ovary cells expressing exogenous hAR. Western blot analysis showed that the most potent androgen, dihydrotestosterone (DHT), stabilizes hAR with the induction of the transactivation function of hAR. However, this androgen-induced stabilization of hAR protein was abrogated by well-known androgen antagonists, hydroxyflutamide and bicalutamide (BIC), with inhibition of the transactivation function of hAR. Thus, the present study suggests that androgen antagonists exert their effects through, at least in part, abrogating the agonist-induced stabilization of hAR protein as well as blocking the ligand-induced transactivation function of hAR.

A Role of Androgen Receptor Protein in Cell Growth of an Androgen-Independent Prostate Cancer Cell Line

Prostate cancer, which develops due to androgen and is initially responsive to androgen deprivation therapy, often comes to acquire androgen deprivation therapy resistance in short order. We investigated the role of androgen receptor (AR) protein in an androgen-independent prostate cancer cell line using AR ligands and AR siRNA. Although the androgen-independent cell line scarcely responded to AR ligands, their growth was attenuated by ablation of AR protein by siRNA.

YM155: A Small Molecule Survivin Suppressant with Potent Antitumor Effect in Human Breast Cancer Models.

Background: Survivin, a member of the inhibitor of apoptosis (IAP) gene family, is a key regulator of apoptosis and mitosis. Aberrant expression of survivin is detected in various clinical tumors, but not in normal adult tissues. Increased survivin expression in cancer patients is an unfavorable prognostic marker correlating with decreased overall survival in several malignancies. Also, survivin expression has been implicated in tumor growth, progression, and resistance to conventional and targeted anticancer agents. YM155 is a novel small molecule survivin suppressant which has demonstated potent antitumor activity against a wide range of cancer cells and is currently in clinical development in a number of tumor types including breast cancer. In this study, we evaluated the therapeutic potential of YM155 against human breast cancer models.Material and Methods: Antiproliferative effect was evaluated by sulforhodamine B assay. In an assessment of gene expression changes, cell viability and caspase activation, cells were analyzed 48-96h post transfection of survivin siRNA or treatment with YM155. For antitumor experiments, three human triple negative breast cancer (TNBC), MRK-nu-1, MDA-MB-231 and MDA-MB-435 cells were subcutaneously or orthotopically implanted into female BALB/c nu/nu mice. After the tumors were established, YM155 was administered as a 7-day continuous sc infusion. Docetaxel was administered IV bolus.Results: In in vitro panel screening derived from human breast tumors, YM155 showed potent antiproliferative activity against breast cancer cell lines with GI 50 values ranging from 0.64 to 32 nM, regardless of ER-alpha, PR, HER-2 expression status. In MRK-nu-1 TNBC cells, YM155 resulted in suppression of survivin expression, caspase-3/7 activation, induction of spontaneous apoptosis, and growth inhibition in the same way that survivin siRNA did. In addition, 7-day continuous infusion of YM155 resulted in the complete regression without body weight loss in an MRK-nu-1 subcutaneous xenograft model, indicating that MRK-nu-1 cells highly depend on survivin for survival. In an MDA-MB-231 human TNBC orthotopic xenograft model, YM155 also induced more durable tumor regression compared with that of the docetaxel treatment group. In the combination study using an MDA-MB-435 orthotopic model, concomitant administration of YM155 and docetaxel showed substantial tumor regression more potently and for longer periods than each single compound administration alone without enhancement of body weight loss.Conclusions: YM155 plus docetaxel showed enhanced antitumor activity as compared to each compound alone without increase in weight loss in breast cancer models, suggesting that survivin suppression may constitute a valuable supplement to current treatment strategies in breast cancer. Since taxanes are commonly utilized in the treatment of breast cancer, these results support evaluating this combination in patients with advanced breast cancer. A phase 2 study of YM155 in combination with docetaxel in women with metastatic HER2 negative breast cancer is planned. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 3140.