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Abstract

  1. Top of page
  2. Abstract
  3. Materials and Methods
  4. Results
  5. Discussion
  6. Acknowledgments
  7. Disclosure Statement
  8. References

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)

Survivin, a member of the inhibitor of apoptosis protein family, has been implicated in cell survival and regulation of mitosis in cancer.(1–3) Compared with the relatively low expression observed in a variety of normal tissues associated with self-renewal, survivin is highly expressed in a broad range of solid tumors and hematological malignancies.(3) Moreover, elevated survivin expression is correlated with negative prognostic factors in a variety of tumor types.(4–11) Studies have shown that survivin suppression induces tumor cell apoptosis and enhances sensitivity to apoptosis induced by existing anticancer drugs and other apoptotic stimuli.(12) Therefore, survivin deprivation may offer a new avenue for anticancer treatment.

YM155, a novel small-molecule survivin suppressant, has been shown to suppress survivin with little effect on expression levels of other IAP family or Bcl-2-related proteins. The molecular mechanisms responsible for YM155-mediated survivin suppression are under evaluation through identification of YM155-interacting molecules that bind to the survivin gene promoter regions. YM155 has demonstrated antitumor activity, with survivin suppression and tumor cell apoptosis, in various human cancer models including hormone-refractory prostate cancer (HRPC)-derived PC-3 human tumor xenograft models.(13) In the present study, the antitumor effects of YM155 have been evaluated in a wide variety of human cancer cell lines and xenograft models to further characterize its preclinical efficacy profile.

Materials and Methods

  1. Top of page
  2. Abstract
  3. Materials and Methods
  4. Results
  5. Discussion
  6. Acknowledgments
  7. Disclosure Statement
  8. References

Cell lines, cultures and reagents.  The human cancer cell lines were obtained from American Type Culture Collection (Manassas, VA, USA), Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH (Braunschweig, Germany), European Collection of Cell Culture (Wiltshire, UK) and Dainippon Pharmaceutical Co. Ltd (Osaka, Japan). Cells were maintained in RPMI 1640 or Dulbecco’ modified Eagle medium (Life Technologies Inc., Gaithersburg, MD, USA), supplemented with 5% or 10% heat-inactivated fetal bovine serum (Invitrogen Co., NY, USA) in a humidified incubator with 5% CO2 at 37°C. For the in vivo studies, cultured cells were collected, suspended and then mixed with an equivalent volume of Matrigel Basement Membrane Matrix (Becton Dickinson Co., Bedford, MA, USA) prior to xenografting as previously described.(13)

YM155 monobromide (YM155; Astellas Pharma, Inc., Tokyo, Japan), cisplatin (Nippon, Kayaku Co., Ltd, Tokyo, Japan), and paclitaxel (Sigma–Aldrich, St. Louis, MO, USA) were dissolved in dimethyl sulfoxide and diluted in saline to a final concentration of <0.1% for in vitro studies. For the in vivo studies, YM155 was dissolved and diluted in saline immediately before administration. Cisplatin was diluted in saline, whereas paclitaxel was diluted in a 50% Cremophor EL/50% ethanol mixture and subsequently in saline. YM155 was s.c. administered by continuous infusion as previously described.(13) Vehicle control groups received vehicle administered in a manner similar to that of each active agent.

In vitro cell growth inhibition assay.  The in vitro antiproliferative activity of YM155 was measured using the sulforhodamine B assay(14–16) with the mean log growth inhibition of 50% (GI50) value calculated by logistic analysis.(13) The p53 status for individual cell lines was established by reference to the International Agency for Research on Cancer database.(17)

Total RNA preparation and real-time polymerase chain reaction.  Total RNA was isolated from cells, cDNA was synthesized and real-time PCR conducted as previously described.(13) All sets of reactions were conducted in triplicate with specific primer pairs of target human genes from survivin and cyclophilin C (CYC), a ubiquitously expressed housekeeping gene. Primer sequences were designed using Primer Express version 1.0 (Applied Biosystems, Foster City, CA, USA). The following sequences were selected: human survivin (forward) 5′-CTGCCTGGCAGCCCTTT-3′ and (reverse) 5′-CCTCC AAGAAGGGCCAGTTC-3′; and human CYC (forward) 5′-CAGACTGCGGCAAGATCGA-3′ and (reverse) 5′-ATGTCCCTGTGCCCTACTCCTT-3′. To calculate the relative gene expression levels, the quantity value for survivin was normalized and deducted from the corresponding quantity value for CYC mRNA in each well. For comparison across cancer cell lines, relative gene expression levels were expressed as a percentage of the value for PC-3 cells (expression value assumed to be 100%). For the in vivo studies, relative gene expression levels were expressed as a percentage of the control (control value assumed to be 100%).

In vivo study animals and measurements. 

Subcutaneous xenograft studies.  Five-week-old male nude mice (BALB/c nu/nu; Charles River Japan, Inc., Kanagawa, Japan) were used as detailed below. NCI-H358, Calu 6, A375 and UM-UC-3 (2–3 × 106/0.1 mL/ mouse) were s.c. injected into the flanks of mice and allowed to reach a tumor volume of >100 mm3, respectively. For the NCI-H358 model, mice were randomized into groups (= 5) to receive s.c. YM155 (up to 10 mg/kg as a 3-day continuous infusion per week for 2 weeks), i.v. cisplatin (single daily dose five times a week for 2 weeks at doses up to 3 mg/kg), i.v. paclitaxel (single daily dose five times a week for 2 weeks at doses up to 20 mg/kg) or vehicle control, and observation continued until day 35. For Calu 6, mice were randomized into groups (= 4) to receive s.c. YM155 (5 mg/kg as a 7-day continuous infusion) or saline control, and observation continued until day 14. The Calu 6 tumors were excised from the animals under chloroform anesthesia on days 0, 1, 3, 7 and 14, and divided equally into two samples. One half was processed for histological analysis and the other was snap frozen and stored at −80°C until used for the analysis of survivin expression. For the A375 model, mice were divided into groups (= 6) to receive s.c. YM155 (doses up to 10 mg/kg as a 3-day continuous infusion per week for 2 weeks) or saline control, and observation continued until day 14. For UM-UC-3 models, the mice were divided into groups (= 5) to receive s.c. YM155 (doses of up to 5 mg/kg per day as a 3-day continuous infusion per week for 2 weeks) or saline control, and observation continued until day 14.

Orthotopic xenograft studies.  Human breast cancer derived MDA-MB-231 cells (5 × 106/50 μL/mouse) were injected into the third mammary fat pads of 8- to 12-week-old female SCID mice (Mus musculus, Animal Resource Centre, Canning Vale, WA, Australia). Twenty-nine days after inoculation, 60 mice were randomized into groups (= 10) to receive s.c. YM155 (2 and 5 mg/kg per day as a 7-day continuous infusion) or saline control, and observation continued until day 27.

Antitumor and bodyweight assessments.  Bodyweight and tumor diameter were measured twice weekly during the study period using calipers, and mean tumor volume was determined by calculating the volume of an ellipsoid using the formula (length × width2 × 0.5). The first day of administration was designated day 0. Antitumor activity was expressed as percent inhibition of tumor growth from the baseline value. The percent inhibition of tumor growth on day X was calculated for each group using the following formula: MTV = 100 × (1 × [{MTV of the treated group on day X}−{MTV of the treated group on day 0}]/[{MTV of the control group on day X}−{MTV of the control group on day 0}]), where MTV is mean tumor volume.

Immunohistochemical studies.  Tumor samples were fixed with 4% paraformaldehyde and embedded in paraffin, and 5-μm sections were prepared. For assessments of morphology and mitotic index (MI), the sections were stained with hematoxylin–eosin. Apoptosis was assessed using TUNEL staining, with cellular DNA fragmentation detected using an in situ apoptosis detection kit (Takara Bio Inc., Shiga, Japan). Survivin expression was evaluated using a rabbit anti-survivin IgG (IBL Co. Ltd, Gunma, Japan) pretreated overnight by incubation with mouse kidney powder (Rockland Immunochemicals Inc., Gilbertsville, PA, USA) to reduce non-specific binding followed by biotinylated anti-rabbit IgG and strepavidin–biotin complex (Dako, Carpinteria, CA, USA). Antigen retrieval was not performed. All immunohistochemistry (IHC) reactions were visualized using the Envision System (Envision HRP, Dako, Carpinteria, CA, USA) and incubated with diaminobenzidine solution (survivin; Muto Pure Chemical Co. Ltd, Tokyo, Japan; others, Dako, Carpinteria, CA, USA). All sections were counterstained with hematoxylin–eosin. For evaluation of mitotic and apoptotic indices, the number of positive nuclei/cells per 1000 tumor cells from four microscopic visual fields containing non-necrotic tumor components was calculated.

Statistical analysis.  To evaluate the correlation between survivin expression levels and cancer cell line YM155 sensitivity, relative gene expression levels were compared with cell line log-transformed GI50 data. Correlations were determined using Pearson’s correlation coefficient. For in vivo studies, values were expressed as the mean ± standard error (SE). Tumor volumes and toxicity data were compared using Dunnett’s multiple range test. For the evaluation of survivin mRNA and mitotic, proliferation and apoptotic indices, the relative expression levels of all YM155-treated groups were compared to control group values. Data were analysed by two-way repeated measures anova followed by Student’s t-test. All analyses were done with JMP statistical software (SAS Institute Inc., Cary, NC, USA); P < 0.05 was the threshold for statistical significance.

Results

  1. Top of page
  2. Abstract
  3. Materials and Methods
  4. Results
  5. Discussion
  6. Acknowledgments
  7. Disclosure Statement
  8. References

YM155 potently inhibits the growth of a wide range of human cancer cell lines.  The antiproliferative activity of YM155 against 119 human cancer cell lines and five known chemo-resistant cell lines in vitro is presented in Table 1 and Figure 1. YM155 inhibited the growth of the majority of human cancer cell lines tested, with the greatest activity in non-Hodgkin’s lymphoma (NHL)-, HRPC-, ovarian cancer-, sarcoma-, non-small-cell lung cancer (NSCLC)-, breast cancer-, leukemia- and melanoma-derived cell lines, with a mean log GI50 value of 15 nM (Table 1). While survivin mRNA was overexpressed in cell lines across all tumor types examined (Fig. 1a), the GI50 value of YM155 for those cell lines only marginally correlated (R2 = 0.12, P = 0.033) with survivin mRNA expression levels (Fig. 1b). The mean GI50 values of YM155 were 11 and 16 nM for p53 mut/null and p53 WT cell lines, respectively (Fig. 1c), suggesting that YM155 potently inhibits the growth of a wide variety of human tumor cell lines regardless of their p53 status.

Table 1.   Cell growth inhibition by YM155 in a large-scale panel of human cancer cell lines in vitro
 GI50 (nM) GI50 (nM) GI50 (nM) GI50 (nM) GI50 (nM)
  1. Total: 124 cell lines. Bold indicates cell lines with p53 mut/null. Italic indicates cell lines with p53 WT.

NSCLCMelanomaProstateSarcomaLymphoma
NCI-H5221.5KUL58-MEL1.2PPC-12.3MES-SA1.4RL0.35
NCI-H231.8RPMI-79513.2DU1454.0SK-ES-12.2Daudi2.3
COR-L232.6SK-MEL-54.2PC-38.2HT-10804.0Jurkat5.3
A4272.9A3756.3TSU-Pr18.2SK-LMS-111HH5.4
NCI-H3585.1SK-MEL-287.622Rv111GCT12Raji12
NCI-H6616.0SK-MEL-211BreastSW87238U93738
CaLu 66.8A375-SM12MDA-MB-4680.64U-2197870Leukemia
Calu-17.1Hs 294T18MDA-MB-2312.9KidneyHL-603.3
SK-MES-110G-36131MDA-MB-4354.2BB65-RCC9.8BV-1735.1
NCI-H22611UZG4-MEL36T-47D9.4BB64-RCC15K-5626.6
PC-1411Malme-3M100BT-209.5Caki-129MOLT-47.1
NCI-H46031BB74-MEL290SK-BR-310ACHN34CCRF-CEM81
A54967BladderZR-75-120LB996-RCC85KCK-22510
LB37-NSCLC260ECV3048.0MCF-729LB1047-RCC130Myeloma
SCLC56378.1BT-54932A-498170PRMI-822611
NCI-H692.5UM-UC-38.7OvaryLB1828-RCC240ARH-7727
DMS1143.1RT435OVCAR-31.6PancreasMC/CAR160
DMS53540SW78054PA-11.7PANC-12.6Resistant cell lines
ColonJ8276RMG-13.8SW199011IGROV-1/CDDP1.7
HCT1163.0LB796-BLC85SW6267.3HPAF-II17CEM/C2170
DLD-14.9T-2488IGROV-17.3BxPC-330A549/R>1000
LOVO6.9SCaBER110ES-216MIA PaCa-233MCF-7/ADR>1000
SW6208.5Head and neckSK-OV-316CFPAC-188MCF-7/mdr-1>1000
CoLo20525LB902-HNSCC3.3Caov-317Glioma  
HT2933KB6.3StomachCGL000122  
HCT-1542LB1617-HNSCC9.6AGS0.83CGL000224  
WiDr50BB49-HNSCC24Hs 746T7.3U-87 MG59  
LS 174T50BB30-HNSCC83NCI-N8732    
COLO 320DM780LB771-HNSCC490Kato III44    
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Figure 1.  Correlation between intracellular survivin levels and antiproliferative activity of YM155 against human cancer cell lines. (a) Survivin expression levels. (b) Survivin expression levels with YM155 antitumor activity. (c) Relationship between p53 status and YM155 antitumor activity. CNS, central nervous system; GI50, mean log growth inhibition of 50%; HRPC, hormone-refractory prostate cancer; LN, logarithm natural; NSCLC, non-small-cell lung cancer.

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The chemo-resistant cell lines IGROV-1/CDDP (GI50: 1.7 nM) and CEM/C2 (GI50: 170 nM) were as sensitive to YM155 as the corresponding parental cell lines IGROV-1 (GI50: 7.3 nM) and CCRF-CEM (GI50: 81 nM). In contrast, MCF-7/ADR, MCF-7/mdr-1 and A549/R cell lines expressing the MDR phenotype were significantly less sensitive (GI50: >1000 nM) to YM155 than the corresponding parental cell lines MCF-7 (GI50: 29 nM) and A549 (GI50: 67 nM). These results suggest that universal MDR-expressing cell lines show cross-resistance to YM155.

YM155 induces regression of tumors in mice from various human cancer xenografts.  The in vivo antitumor activity of YM155 was evaluated in melanoma (A375), bladder (UM-UC-3) and estrogen receptor-negative breast (MDA-MB-231) cancer xenograft models (Fig. 2). In the A375 s.c. xenograft model, YM155 significantly inhibited the growth of tumor by 80% at 1 mg/kg, and also induced tumor regression from day 0 at 3 and 10 mg/kg (Fig. 2a). In the UM-UC-3 s.c. xenograft model, YM155 significantly inhibited the growth of tumor by 87% at 3 mg/kg, and also induced tumor regression from day 0 at 10 mg/kg (Fig. 2b). In the MDA-MB-231 orthotopic xenograft model, 2 and 5 mg/kg of YM155 resulted in significant tumor regression from day 0, and complete regression was observed at 5 mg/kg in two of 10 mice on day 27 (Fig. 2c). No significant decrease in bodyweight was observed in any YM155-treated animals tested during the experiment (Fig. 2d). These results suggest that YM155 is effective in a wide variety of human cancer xenograft models without showing systemic toxicity as indicated by bodyweight loss.

image

Figure 2.  YM155-induced tumor regression in various human s.c. xenografted tumors in mice. (a) A375 malignant melanoma. (b) UM-UC-3 superficial bladder cancer. (c,d) Orthotopic MDA-MB-231 breast cancer. **P < 0.01 versus controls. NS, not significant versus controls. CR, complete regression.

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YM155 induces regressions of tumors without significant weight loss in human NSCLC xenografted mice.  As shown in Figure 3a, YM155 administered as 3-day continuous infusions at 3 and 10 mg/kg induced complete inhibition of tumor growth in the NCI-H358 human NSCLC xenograft model compared with the control group, and induced significant tumor regressions (41% and 70% when compared with initial tumor volumes) without affecting bodyweight on day 14. Although cisplatin (3 mg/kg) exhibited 75% inhibition of tumor growth on day 14 (Fig. 3b), this was accompanied by a significant decrease in bodyweight. Paclitaxel (20 mg/kg) induced complete inhibition of tumor growth and significant regression of tumor volume (46%) on day 14 (Fig. 3c), but a marked decrease in bodyweight was concurrently observed. Importantly, more than 3 weeks after the last dosing of each drug (day 35), YM155 and paclitaxel continued to maintain significant antitumor activity compared with control groups. In contrast, cisplatin did not retain any significant antitumor activity. Both cisplatin and paclitaxel continued to cause significantly decreased bodyweight when compared with the control groups on day 35. These results suggest that YM155 has a more tolerable safety profile than cisplatin and paclitaxel, as determined by the effects on bodyweight, and YM155 has a longer time-to-progression than cisplatin. These results indicate that YM155 provides a greater margin of safety and efficacy than conventional anticancer drugs in this model.

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Figure 3.  Tumor growth inhibitory effects on bodyweight in s.c. xenografted NCI-H358 tumors in mice. (a) YM155. (b) Cisplatin. (c) Paclitaxel. *< 0.05, **P < 0.01 versus controls. MTD, maximum tolerated dose; NS, not significant versus controls; vertical bars, SE (= 5).

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Tumor regression induced by YM155 is accompanied by suppression of intratumoral survivin and induction of apoptosis.  YM155 was administered in the human Calu 6 NSCLC xenograft model as a 7-day continuous infusion at 5 mg/kg from day 0 through day 7. YM155 completely inhibited growth of Calu 6 tumor xenografts and induced tumor regression from day 0 (Fig. 4a). No tumor regrowth was observed until day 14.

image

Figure 4.  Tumor regression and survivin suppression induced by YM155 in s.c. xenografted Calu 6 human non-small-cell lung cancer tumors in mice. (a) Tumor regression. (b) Intratumoral survivin expression. (c) Mitotic index. (d) Apoptotic index. Data are expressed as mean ± SE (= 4). *< 0.05, **< 0.01 versus controls. NS, not significant versus controls (Student’s t-test).

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Survivin mRNA levels were measured by real-time PCR in the tumors obtained from the control saline- and the YM155-treated mice (Fig. 4b). Mitotic and apoptotic indices were also calculated from the numbers of positive nuclei/cells in the tumors by conducting TUNEL and hematoxylin–eosin staining in each tumor sample (Fig. 4c,d). Survivin protein was detected in both the cytoplasm and nucleus of Calu 6 tumors from saline-treated mice, whereas no survivin was observed in the surrounding host-derived fibroblasts (Fig. 5). In the tumors from YM155-treated mice, survivin protein and mRNA were significantly decreased starting from day 3 (Figs 4b,5). Survivin re-expression was observed on day 14, 7 days after the end of the YM155 treatment. In addition, YM155 concomitantly increased the apoptotic index in tumors (Fig. 4d), with increases statistically significant compared with the control group (P < 0.01 on days 3 and 7, and P < 0.05 on day 14). The mean apoptotic index on days 3, 7 and 14 was 0.03%, 0.15% and 0.1% in the control group and 1.1%, 0.98% and 0.35% in the YM155 group, respectively (Fig. 4d). Mitotic cells with morphological features of metaphase, anaphase or telophase were observed in the control groups; however, MI fell significantly during the YM155 treatment (P < 0.01 on days 1, 3 and 7, and P < 0.05 on day 14), and the mean MI dropped by approximately 60% to 80% during the YM155 treatment from day 1 through day 14 (Fig. 4c). These results indicate that YM155-induced tumor regression is accompanied by downregulation of intratumoral survivin and apoptosis induction.

image

Figure 5. In situ detection of survivin in Calu 6 tumors treated with YM155.

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Discussion

  1. Top of page
  2. Abstract
  3. Materials and Methods
  4. Results
  5. Discussion
  6. Acknowledgments
  7. Disclosure Statement
  8. References

Survivin is a novel target for anticancer therapy,(18) with its inhibition shown to disturb cell proliferation and induce apoptosis in a range of tumor types.(19–26) In the present study, we have demonstrated the potent antitumor activity of YM155 against a broad variety of human tumor cell lines. However, given marginal correlation of GI50 with survivin mRNA, the sensitivity of the cell lines to YM155 cannot simply be explained by survivin expression. Although an antitumor effect distinct from survivin cannot be excluded, YM155 at 10 μM had little or no effect on numerous receptors and ion channels (except for sodium channels; data not shown). Furthermore, YM155 (10 μM in 10% charcoal-free FBS conditions) did not induce cell death in normal human cells (data not shown). In addition, it should be noted that the antitumor effects of YM155 occur in the absence of any common side-effects typically seen with conventional chemotherapeutics.

Previous studies have suggested that YM155 may be incorporated into cancer cells in a carrier-mediated manner.(27,28) In line with those findings, our preliminary investigations suggest that the level of intracellular incorporation of YM155 varies between different cell lines and that a significant correlation exists for YM155 between intracellular concentration and in vitro sensitivity (data not shown). In addition, YM155 was less effective in MCF-7/ADR and MCF-7/mdr-1 cell lines expressing the MDR phenotype than in the corresponding parental cells (Table 1). It should be noted that those differences in the intracellular concentration of YM155 could be the result of the altered interaction of multiple drug influx and efflux transporters. As YM155 is a substrate for MDR proteins as evidenced by the in vitro inhibition of p-glycoprotein-mediated transport by YM155 across Caco-2 cell monolayers (data not shown), it is unlikely that YM155 can overcome acquired drug resistance through the expression of MDR proteins. YM155 also showed no cross-resistance against cisplatin-resistant IGROV-1/CDDP and camptothecin-resistant CEM-C2 cells (Table 1). These results indicate the potential of YM155 in cisplatin- or camptothecin-pretreated cancer patients.

YM155 significantly suppressed mRNA and protein levels of survivin in p53-deficient Calu 6 tumors (Figs 4,5). Abnormal expression of p53 has been reported in a variety of cancers,(29) with p53 alteration shown to be a poor prognostic marker in several tumor types.(30–32) It is well established that survivin expression is repressed by WT p53(33–35) and that loss of WT p53 function in tumor cells may contribute to an upregulation of survivin and resistance to conventional chemotherapeutic agents. In the 60 cell lines of the NCI cell screen, cells with a mutant p53 sequence tended to exhibit less growth inhibition in this screen than the WT p53 cell lines when treated with the majority of clinically used anticancer agents, including DNA cross-linking agents, antimetabolites and topoisomerase I and II inhibitors.(18,36) In the current study, YM155 inhibited the in vitro growth of cell lines irrespective of p53 status, and exhibited significant in vivo antitumor activity in various p53-mutated or p53-defective human tumor xenograft models of NSCLC (Calu 6 and NCI-H358), bladder (UM-UC-3) and breast (MDA-MB-231) cancer. We have previously demonstrated that YM155 can inhibit the expression of survivin in both p53 wild-type and deficient cell lines,(13) and the current data support those findings. If such broad preclinical effectiveness is translated into clinical efficacy in tumors with p53 mutations, YM155 would represent an important advance over conventional chemotherapeutic agents.

In the NCI-H358 xenograft model, YM155 displayed superior anticancer activity to that of cisplatin or paclitaxel at highly tolerable dosage levels (Fig. 3). There is significant literature to suggest the optimal use of survivin suppressants or inhibitors in combination with conventional chemotherapeutic agents. Downregulation of survivin by antisense or small interfering RNA (siRNA) induced apoptosis and sensitized tumor cells to radiation therapy,(10) etoposide(20) and doxorubicin treatment(37) in NSCLC. Transfection with survivin antisense also rendered cisplatin-resistant human melanoma-derived cells susceptible to cisplatin.(38) Furthermore, anti-survivin siRNA sensitized human melanoma-derived cells to Apo2L/TRAIL with a marked increase in apoptosis, and the effect was more potent than that of siRNA against Bcl-2.(39) Iwasa et al.(40) recently reported that YM155 sensitized NSCLC cells to radiation and this effect of YM155 is likely attributable to the inhibition of DNA repair and enhancement of apoptosis. It would appear that evaluations of YM155 with radiation and other conventional chemotherapeutic agents, as well as molecular targeted agents in various cancer models, are warranted to identify the clinical role of YM155.

In summary, YM155 has demonstrated potent anticancer activity against a broad spectrum of human cancer cell lines and various human-derived tumor xenograft mouse models by altering intratumoral survivin expression levels and a subsequent direct apoptosis induction. Such potent antitumor activity is in accordance with data from a PC-3 tumor xenograft model,(13) and also compares favorably with results from recently completed Phase I/II clinical studies in which a tumor response was observed in a number of different tumor types in patients receiving YM155.(41–44) Further investigations of YM155 in a wide range of tumor types are clearly warranted.

Acknowledgments

  1. Top of page
  2. Abstract
  3. Materials and Methods
  4. Results
  5. Discussion
  6. Acknowledgments
  7. Disclosure Statement
  8. References

This study was supported by Astellas Pharma, Inc. The authors thank the entire team members at Astellas Pharma Inc., Astellas Pharma Global Development, Inc. and Caudex Medical Inc. for their stimulating discussions and comments on the manuscript, and Drs T. Shishido and K. Nakano (Astellas Research Technology Co., Ltd, Osaka, Japan) and Drs M. Takeuchi and Y. Maeda (Sapporo General Pathology Laboratory Co., Ltd, Sapporo, Japan) for conducting immunohistochemical studies.

Disclosure Statement

  1. Top of page
  2. Abstract
  3. Materials and Methods
  4. Results
  5. Discussion
  6. Acknowledgments
  7. Disclosure Statement
  8. References

The research was funded by Astellas Pharma, Inc. All authors are employees of Astellas Pharma, Inc. The authors have no further conflicts of interest to disclose.

References

  1. Top of page
  2. Abstract
  3. Materials and Methods
  4. Results
  5. Discussion
  6. Acknowledgments
  7. Disclosure Statement
  8. References
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