Takahito Nakahara

YM155, a Novel Small-Molecule Survivin Suppressant, Induces Regression of Established Human Hormone-Refractory Prostate Tumor Xenografts

Various accumulating evidence suggests that survivin, a member of the inhibitor of apoptosis (IAP) family, plays an important role in drug resistance and cancer cell survival in many types of cancer, including hormone-refractory prostate cancer (HRPC). Here, we characterized YM155, a novel small-molecule survivin suppressant, using a survivin gene promoter activity assay. YM155 suppressed expression of survivin and induced apoptosis in PC-3 and PPC-1 human HRPC cell lines at 10 nmol/L. In contrast, YM155 up to 100 nmol/L showed little effect on expression levels of other IAP- or Bcl-2-related proteins. In a s.c. xenografted PC-3 tumor model in mice, 3-day continuous infusions of YM155 at 3 to 10 mg/kg induced massive tumor regression accompanied by suppression of intratumoral survivin. YM155 also completely inhibited the growth of orthotopically xenografted PC-3 tumors. No significant decreases in body weight were observed in mice treated with YM155 during the experimental period. Pharmacokinetic analyses indicated that YM155 is highly distributed to tumors and at concentrations approximately 20-fold higher than those in plasma. Our findings represent the first attempt to show tumor regression and suppression of survivin in p53-deficient human HRPC cells by a single small molecular compound treatment. Further extensive investigation of YM155 in many types of cancer, including HRPC, seems to be worthwhile to develop this novel therapeutic approach.

Broad spectrum and potent antitumor activities of YM155, a novel small‐molecule survivin suppressant, in a wide variety of human cancer cell lines and xenograft models

Antitumor activities of YM155, a novel small‐molecule survivin suppressant, were investigated in a wide variety of human cancer cell lines and xenograft models. YM155 inhibited the growth of 119 human cancer cell lines, with the greatest activity in lines derived from non‐Hodgkin’s lymphoma, hormone‐refractory prostate cancer, ovarian cancer, sarcoma, non‐small‐cell lung cancer, breast cancer, leukemia and melanoma. The mean log growth inhibition of 50% (GI50) value was 15 nM. The mean GI50 values of YM155 were 11 nM for p53 mut/null cell lines and 16 nM for p53 WT cell lines, suggesting that YM155 inhibits the growth of human tumor cell lines regardless of their p53 status. In non‐small‐cell lung cancer (Calu 6, NCI‐H358), melanoma (A375), breast cancer (MDA‐MB‐231) and bladder cancer (UM‐UC‐3) xenograft models, 3‐ or 7‐day continuous infusions of YM155 (1–10 mg/kg) demonstrated significant antitumor activity without showing significant bodyweight loss. Tumor regressions induced by YM155 were associated with reduced intratumoral survivin expression levels, increased apoptosis and decreased mitotic indices. The broad and potent antitumor activity presented in the present study is indicative of the therapeutic potential of YM155 in the clinical setting. (Cancer Sci 2011; 102: 614–621)

Radiosensitizing Effect of YM155, a Novel Small-Molecule Survivin Suppressant, in Non–Small Cell Lung Cancer Cell Lines

Purpose: Survivin, a member of the inhibitor of apoptosis protein family, is an attractive target for cancer therapy. We have now investigated the effect of YM155, a small-molecule inhibitor of survivin expression, on the sensitivity of human non–small cell lung cancer (NSCLC) cell lines to γ-radiation. Experimental Design: The radiosensitizing effect of YM155 was evaluated on the basis of cell death, clonogenic survival, and progression of tumor xenografts. Radiation-induced DNA damage was evaluated on the basis of histone H2AX phosphorylation and foci formation. Results: YM155 induced down-regulation of survivin expression in NSCLC cells in a concentration- and time-dependent manner. A clonogenic survival assay revealed that YM155 increased the sensitivity of NSCLC cells to γ-radiation in vitro. The combination of YM155 and γ-radiation induced synergistic increases both in the number of apoptotic cells and in the activity of caspase-3. Immunofluorescence analysis of histone γ-H2AX also showed that YM155 delayed the repair of radiation-induced double-strand breaks in nuclear DNA. Finally, combination therapy with YM155 and γ-radiation delayed the growth of NSCLC tumor xenografts in nude mice to a greater extent than did either treatment modality alone. Conclusions: These results suggest that YM155 sensitizes NSCLC cells to radiation both in vitro and in vivo, and that this effect of YM155 is likely attributable, at least in part, to the inhibition of DNA repair and enhancement of apoptosis that result from the down-regulation of survivin expression. Combined treatment with YM155 and radiation warrants investigation in clinical trials as a potential anticancer strategy.

Antitumor activity of YM155, a selective small-molecule survivin suppressant, alone and in combination with docetaxel in human malignant melanoma models.

Purpose: Aggressive cell growth and chemoresistance are notorious obstacles in melanoma therapy. Accumulating evidence suggests that survivin is preferentially expressed in cancer cells and plays a crucial role in cell division and apoptosis dysfunction. Here, we evaluated the therapeutic potential of YM155, a selective survivin suppressant, alone and in combination with docetaxel using human melanoma models. Experimental Design: A375 and SK-MEL-5 human malignant melanoma cells were treated with siRNA, YM155, and/or docetaxel, and cell viability, mRNA and protein expression levels, cell-cycle distribution, and immunohistochemical staining were then evaluated. Furthermore, the efficacy of YM155 combined with docetaxel was further examined in established xenograft models. Results: Survivin suppression was sufficient to induce spontaneous apoptosis of melanoma cells. YM155 showed nanomolar antiproliferative effects and induced tumor regression in established melanoma xenograft models. Docetaxel showed antitumor activity against melanoma cells, although it also induced survivin upregulation and G2/M mitotic arrest; however, cotreatment with YM155 decreased survivin expression below basal levels. Combination treatment of YM155 and docetaxel induced a greater rate of apoptosis than the sum of the single-treatment rates and promoted tumor regression without enhanced body weight loss in the melanoma xenograft models. Conclusions: Survivin is responsible for the inherent low levels of spontaneous apoptosis in melanoma cells. The concomitant combination of YM155 with docetaxel diminished the accumulation of survivin in G2/M mitotic arrest, and induced more intense apoptosis compared with each single treatment. YM155 in combination with docetaxel is well tolerated and shows greater efficacy than either agent alone in mouse xenograft models. Clin Cancer Res; 17(16); 5423–31. ©2011 AACR.

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.

Carrier-Mediated Uptake of 1-(2-Methoxyethyl)-2-methyl-4,9-dioxo-3-(pyrazin-2-ylmethyl)-4,9-dihydro-1H-naphtho[2,3-d]imidazolium Bromide (YM155 Monobromide), a Novel Small-Molecule Survivin Suppressant, into Human Solid Tumor and Lymphoma Cells

1-(2-Methoxyethyl)-2-methyl-4,9-dioxo-3-(pyrazin-2-ylmethyl)-4,9-dihydro-1H-naphtho[2,3-d]imidazolium bromide (YM155 monobromide) is a novel small-molecule survivin suppressant that induces the down-regulation of survivin and exhibits potent antitumor activity in nude mice bearing the human hormone refractory prostate carcinoma cell line PC-3. In this study, radioluminographic determination of the in vivo distribution of radioactivity after administration of [14C]YM155 to PC-3-xenografted nude mice revealed a relatively high level of radioactivity in the PC-3 xenograft. Therefore, the uptake of [14C]YM155 was further characterized in vitro using PC-3, lung cancer (Calu-6 and NCI-H358), malignant melanoma (A375 and SK-MEL-5), and non-Hodgkins lymphoma (RL and Ramos) cell lines. The uptake of [14C]YM155 in these cell lines was dependent on incubation time, temperature, and drug concentration. The Michaelis-Menten constant values were similar among the seven cell lines (0.189–0.367 μM). The effects of various compounds on the uptake of [14C]YM155 were tested in PC-3, Calu-6, A375, RL, and Ramos cell lines. Of the compounds tested, the cationic transporter substrates/inhibitors (tetraethylammonium, 1-methyl-4-phenylpyridium, cimetidine, prazosin, corticosterone, verapamil, amantadine, procainamide, and N-methylnicotinamide) inhibited the uptake of [14C]YM155 to a similar extent among the five cell lines. The half-maximal inhibitory concentration values (IC50) of several compounds for the uptake of [14C]YM155 into PC-3 differed from those reported in the literature for human organic cation transporter 1 (OCT1/SLC22A1), OCT2 (SLC22A2), and OCT3 (SLC22A3). To summarize, YM155 was taken up into cancer cells in a carrier-mediated manner and with a similar affinity among all the cancer cell lines tested. An influx transporter(s) may contribute to this process.