CXCL12–CXCR7 axis is important for tumor endothelial cell angiogenic property

We reported that tumor endothelial cells (TECs) differ from normal endothelial cells (NECs) in many aspects, such as gene expression profiles. Although CXCR7 is reportedly highly expressed in blood vessels of several tumors, its function in TECs is still unknown. To investigate this role, we isolated TECs from mouse tumor A375SM xenografts, and compared them with NECs from normal mouse dermis. After confirming CXCR7 upregulation in TECs, we analyzed its function using CXCR7 siRNA and CXCR7 inhibitor; CCX771. CXCR7 siRNA and CCX771 inhibited migration, tube formation and resistance to serum starvation in TECs but not in NECs. ERK1/2 phosphorylation was inhibited by CXCR7 knockdown in TECs. These results suggest that CXCR7 promotes angiogenesis in TECs via ERK1/2 phosphorylation. Using ELISA, we also detected CXCL12, a ligand of CXCR7, in conditioned medium from TECs, but not from NECs. CXCL12 neutralizing antibody significantly inhibited TEC random motility. VEGF stimulation upregulated CXCR7 expression in NECs, implying that VEGF mediates CXCR7 expression in endothelial cells. A CXCR7 inhibitor, CCX771 also inhibited tumor growth, lung metastasis and tumor angiogenesis in vivo. Taken together, the CXCL12–CXCR7 autocrine loop affects TEC proangiogenic properties, and could be the basis for an antiangiogenic therapy that specifically targets tumor blood vessels rather than normal vessels.     

Combination of carmustine and selenite effectively inhibits tumor growth by targeting androgen receptor,androgen receptor‐variants,and Akt in preclinical models: New hope for patients with castration resistant prostate cancer

Despite established androgen receptor (AR) antagonists, AR/AR‐variants signaling remain a major obstacle for the successful treatment of castration resistant prostate cancer (CRPC). In addition, CRPC cells adapt to survive via AR‐independent pathways to escape next generation therapies. Therefore, there is an urgent need for drugs that can target these signaling pathways in CRPC. In this study, we sought to determine whether carmustine and selenite in combination could induce apoptosis and inhibit growth of CRPC in‐vitro and in‐vivo. CRPC (22Rv1, VCaP, and PC‐3) cell lines in culture and xenograft mouse were used. Combination of carmustine and selenite treatment significantly increased reactive oxygen species, apoptosis and growth inhibition in CRPC cells with down regulation of anti‐apoptotic (Bcl‐2 and Mcl‐1) and proliferative proteins (c‐Myc and cyclin‐D1). This effect was associated with complete reduction of AR/AR‐variants, AR‐V7, PSA and significant induction of p27Kip1. Combination treatment substantially abolished phospho‐Akt, phospho‐GSK‐3β, and anchorage‐independent growth in AR‐positive and AR‐negative cells. Consistent with in‐vitro results, combination treatment effectively induced apoptosis and completely inhibited xenograft tumor growth and markedly reduced AR/AR‐variants, AR‐V7, PSA, and Bcl‐2 in xenograft tumors without causing genotoxicity in host mice. Individual agent treatment showed only partial effect. The combination treatment showed a significant synergistic effect. The present study is the first to demonstrate that the combination of carmustine and selenite treatment completely suppressed CRPC tumor growth by reducing AR/AR‐variants and Akt signaling. Our findings suggest that the combination of carmustine and selenite could constitute a promising next‐generation therapy for successful treatment of patients with CRPC.     

A novel calcium-dependent mechanism of acquired resistance to IGF-1 receptor inhibition in prostate cancer cells

Inhibition of the mitogenic insulin-like growth factor receptor 1 (IGF-1R) signaling axis is a compelling treatment strategy for prostate cancer. Combining the IGF-1R inhibitor ganitumab (formerly AMG 479) with standard of care androgen-deprivation therapy greatly delays prostate cancer recurrence in xenograft models; however, a significant proportion of these tumors ultimately acquire resistance to ganitumab. Here we describe the development of a stable and reproducible ganitumab-resistant VCaP human prostate cancer cell derivative termed VCaP/GanR to investigate the mechanism of acquired resistance to IGF-1R inhibition. Unlike parental VCaP, VCaP/GanR did not undergo apoptosis following ganitumab treatment. VCaP/GanR did not express increased levels of IGF-1R, insulin receptor, or phospho-AKT compared to parental VCaP. VCaP/GanR exhibited increased levels of phospho-S6 indicative of increased mTOR activity. However, acquired resistance to ganitumab was not dependent on increased mTOR activity in VCaP/GanR. Phospho-proteomic arrays revealed alterations in several calcium-regulated signaling components in VCaP/GanR compared to VCaP. Reduction of intracellular calcium using cell-permeable calcium-specific chelators restored ganitumab sensitivity to VCaP/GanR through inhibition of cell-cycle progression. These data suggest a new mechanism of resistance to IGF-1R inhibition involving calcium-mediated proliferation effects. Such pathways should be considered in future clinical studies of IGF-1R inhibitors in prostate cancer.     

Clinical and biological significance of CXCR5 expressed by prostate cancer specimens and cell lines

Chemokines and chemokine receptors have been shown to be involved in metastatic process of prostate cancer (PCa). In this study, we show primary PCa tissues and cell lines (LNCaP and PC3) express CXCR5, a specific chemokine receptor for CXCL13. Expression of CXCR5 was significantly higher (p < 0.001) in PCa cases than compared to normal match (NM) tissues. CXCR5 intensity correlated (R² = 0.97) with Gleason score. While prostate tumor tissues with Gleason scores ≥ 7, displayed predominantly nuclear CXCR5 expression patterns, PCa specimens with Gleason scores ≤ 6 showed predominantly membrane and cytoplasmic expression patterns that were comparable to benign prostatic hyperplasia (BPH). Similar to tissue expression, PCa cell lines expressed significantly more CXCR5 than normal prostatic epithelial cells (PrECs), and CXCR5 expression was distributed among intracellular and extracellular compartments. Functional in vitro assays showed higher migratory and invasive potentials toward CXCL13, an effect that was mediated by CXCR5. In both PCa cell lines, CXCL13 treatment increased the expression of collagenase‐1 or matrix metalloproteinase‐1 (MMP‐1), collagenase‐3 (MMP‐13), stromelysin‐1 (MMP‐3), stromelysin‐2 (MMP‐10) and stromelysin‐3 (MMP‐11). These data demonstrate the clinical and biological relevance of the CXCL13‐CXCR5 pathway and its role in PCa cell invasion and migration. © 2009 UICC     

Inhibition of the HER2-YB1-AR axis with Lapatinib synergistically enhances Enzalutamide anti-tumor efficacy in castration resistant prostate cancer

Incurable castration-resistant prostate cancer (CRPC) is driven by androgen receptor (AR) activation. Potent therapies that prevent AR signaling, such as Enzalutamide (ENZ), are mainstay treatments for CRPC; however patients eventually progress with ENZ resistant (ENZR) disease. In this study, we investigated one mechanism of ENZ resistance, and tried to improve therapeutic efficiency of ENZ. We found HER2 expression is increased in ENZR tumors and cell lines, and is induced by ENZ treatment of LNCaP cells. ENZ-induced HER2 overexpression was dependent on AKT-YB1 activation and modulated AR activity. HER2 dependent AR activation in LNCaP and ENZR cells was effectively blocked by treatment with the EGFR/HER2 inhibitor Lapatinib, which reduced cell viability and increased apoptosis. Despite efficacy in vitro, in vivo monotherapy with Lapatinib did not prevent ENZR tumor growth. However, combination treatment of Lapatinib with ENZ most effectively induced cell death in LNCaP cells in vitro and was more effective than ENZ alone in preventing tumor growth in an in vivo model of CRPC. These results suggest that while HER2 overexpression and subsequent AR activation is a targetable mechanism of resistance to ENZ, therapy using Lapatinib is only a rational therapeutic approach when used in combination with ENZ in CRPC.     

Systemic GLIPR1‐ΔTM protein as a novel therapeutic approach for prostate cancer

GLIPR1 is a p53 target gene known to be downregulated in prostate cancer, and increased endogenous GLIPR1 expression has been associated with increased production of reactive oxygen species, increased apoptosis, decreased c‐Myc protein levels and increased cell cycle arrest. Recently, we found that upregulation of GLIPR1 in prostate cancer cells increases mitotic catastrophe through interaction with heat shock cognate protein 70 (Hsc70) and downregulation of Aurora kinase A and TPX2. In this study, we evaluated the mechanisms of recombinant GLIPR1 protein (glioma pathogenesis‐related protein 1‐transmembrane domain deleted [GLIPR1‐ΔTM]) uptake by prostate cancer cells and the efficacy of systemic GLIPR1‐ΔTM administration in a prostate cancer xenograft mouse model. GLIPR1‐ΔTM was selectively internalized by prostate cancer cells, leading to increased apoptosis through reactive oxygen species production and to decreased c‐Myc protein levels. Interestingly, GLIPR1‐ΔTM was internalized through clathrin‐mediated endocytosis in association with Hsc70. Systemic administration of GLIPR1‐ΔTM significantly inhibited VCaP xenograft growth. GLIPR1‐ΔTM showed no evidence of toxicity following elimination from mouse models 8 hr after injection. Our results demonstrate that GLIPR1‐ΔTM is selectively endocytosed by prostate cancer cells, leading to increased reactive oxygen species production and apoptosis, and that systemic GLIPR1‐ΔTM significantly inhibits growth of VCaP xenografts without substantial toxicity.     

The addition of AG-013736 to fractionated radiation improves tumor response without functionally normalizing the tumor vasculature

Although antiangiogenic strategies have proven highly promising in preclinical studies and some recent clinical trials, generally only combinations with cytotoxic therapies have shown clinical effectiveness. An ongoing question has been whether conventional therapies are enhanced or compromised by antiangiogenic agents. The present studies were designed to determine the pathophysiologic consequences of both single and combined treatments using fractionated radiotherapy plus AG-013736, a receptor tyrosine kinase inhibitor that preferentially inhibits vascular endothelial growth factor receptors. DU145 human prostate xenograft tumors were treated with (a) vehicle alone, (b) AG-013736, (c) 5x2 Gy/wk radiotherapy fractions, or (d) the combination. Automated image processing of immunohistochemical images was used to determine total and perfused blood vessel spacing, overall hypoxia, pericyte/collagen coverage, proliferation, and apoptosis. Combination therapy produced an increased tumor response compared with either monotherapy alone. Vascular density progressively declined in concert with slightly increased alpha-smooth muscle actin-positive pericyte coverage and increased overall tumor hypoxia (compared with controls). Although functional vessel endothelial apoptosis was selectively increased, reductions in total and perfused vessels were generally proportionate, suggesting that functional vasculature was not specifically targeted by combination therapy. These results argue against either an AG-013736- or a combination treatment-induced functional normalization of the tumor vasculature. Vascular ablation was mirrored by the increased appearance of dissociated pericytes and empty type IV collagen sleeves. Despite the progressive decrease in tumor oxygenation over 3 weeks of treatment, combination therapy remained effective and tumor progression was minimal.     

Fatigue,treatment satisfaction and health‐related quality of life among patients receiving novel drugs suppressing androgen signalling for the treatment of metastatic castrate‐resistant prostate cancer

Clinical studies have demonstrated the benefits of abiraterone acetate + prednisone (AAP) and enzalutamide (ENZ) in significantly improving survival among metastatic castration‐resistant prostate cancer (mCRPC) patients. However, evidence regarding patient's real‐world experience, particularly with respect to fatigue, treatment satisfaction and health‐related quality of life (HRQoL) is limited. Interviews were initially conducted with patients (n = 38) and carers (n = 12) to elicit qualitative data regarding their experiences. Findings informed the design of a quantitative, multinational online survey of mCRPC patients (n = 152) receiving AAP or ENZ. Participants completed validated questionnaires assessing fatigue (Brief Fatigue Inventory), treatment satisfaction (Cancer Therapy Satisfaction Questionnaire) and HRQoL (EuroQol‐5‐Dimensions). Results indicated that patients were generally satisfied with these therapies, more specifically with reductions in prostate‐specific antigen levels and extended survival. Fatigue was commonly linked to poor HRQoL and responses indicated that significantly fewer patients in the AAP group reported feeling usually tired or fatigued in the last week compared to the ENZ group (33% vs. 55%, p = 0.006 respectively). Findings highlight the benefit of AAP and ENZ in promoting the “quality” of extended survival. That fatigue was lower among patients receiving AAP may be important for informing treatment decisions. Further research is needed to gain deeper insights.     

Preclinical characterization of AEG35156/GEM 640, a second-generation antisense oligonucleotide targeting X-linked inhibitor of apoptosis.

PURPOSE: Cancer cells can use X-linked inhibitor of apoptosis (XIAP) to evade apoptotic cues, including chemotherapy. The antitumor potential of AEG35156, a novel second-generation antisense oligonucleotide directed toward XIAP, was assessed in human cancer models when given as a single agent and in combination with clinically relevant chemotherapeutics. EXPERIMENTAL DESIGN: AEG35156 was characterized for its ability to cause dose-dependent reductions of XIAP mRNA and protein in vitro and in vivo, to sensitize cancer cell lines to death stimuli, and to exhibit antitumor activity in multiple human cancer xenograft models as a single agent or in combination with chemotherapy. RESULTS: AEG35156 reduced XIAP mRNA levels with an EC50 of 8 to 32 nmol/L and decreased XIAP protein levels by >80%. Loss of XIAP protein correlated with increased sensitization to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis in Panc-1 pancreatic carcinoma cells. AEG35156 exhibited potent antitumor activity relative to control oligonucleotides in three human cancer xenograft models (prostate, colon, and lung) and was capable of inducing complete tumor regression when combined with taxanes. Antitumor effects of AEG35156 correlated with suppression of tumor XIAP levels. CONCLUSIONS: AEG35156 reduces XIAP levels and sensitizes tumors to chemotherapy. AEG35156 is presently under clinical assessment in multiple phase I trials in cancer patients as a single agent and in combination with docetaxel in solid tumors or cytarabine/idarubicin in leukemia.     

Lymphatic zip codes in premalignant lesions and tumors

Blood vessels in tumors are morphologically and functionally distinct from normal resting blood vessels. We probed lymphatic vessels in premalignant lesions and tumors by in vivo screening of phage-displayed peptide libraries, asking whether they too have distinctive signatures. The resulting peptides begin to define such signatures. One peptide identified the lymphatics in a human melanoma xenograft. Another recognized the lymphatics in prostate cancers but not in premalignant prostate lesions; this peptide similarly identifies human prostate cancer lymphatics. A third was selective for the lymphatics in the premalignant prostate lesions. A fourth identified the lymphatics in dysplasias and squamous carcinomas of the cervix and skin. None recognize lymphatics in normal tissues. Thus, tumor development is associated with organ- and stage-specific changes in lymphatics. Systemic treatment of mice with fusions of a lymphatic homing peptide and a proapoptotic motif reduced the number of tumor lymphatics in prostate tumor and melanoma, forecasting future lymphatic targeting agents for detection and therapeutic intervention.     

Evaluation of combined (177)Lu-DOTA-8-AOC-BBN (7-14)NH(2) GRP receptor-targeted radiotherapy and chemotherapy in PC-3 human prostate tumor cell xenografted SCID mice

The focus of this study was to evaluate the therapeutic benefit of combined gastrin-releasing peptide (GRP) receptor-targeted radiotherapy (TRT) with chemotherapy, using the PC-3 xenograft severe combined immunodeficiency (SCID) mouse model. (177)Lu-DOTA-8-AOC-BBN(7-14)NH(2) is a radiotherapeutic peptide that specifically targets the gastrin-releasing peptide receptor overexpressed on primary and metastatic prostate cancer. The chemotherapeutic agents, docetaxel and estramustine, were administered as single agents or in combination with the receptor-targeted radiotherapeutic agent. Combination receptor TRT/chemotherapy studies were begun 21 days postxenografting and were conducted as multiple-dose trials. The GRP receptor TRT agent was administered every 14 days, and single and combination chemotherapy dose regimens were given weekly. Tumor size, body weight, and body condition score were evaluated twice-weekly and a hematology profile once-weekly. Therapy study tumor volumes were evaluated by way of a repeated measures analysis of variance (ANOVA). Tumor volume measurements at 12 days postdose administration demonstrated a statistically significant (two-tailed P-value <0.05) tumor growth suppression in all experimental groups receiving GRP receptor-targeted radiotherapy, when compared to the control group. The two combined GRP receptor TRT/chemotherapy treatment groups demonstrated the greatest tumor growth suppression of all treatment groups. In comparing the two combined GRP receptor TRT/chemotherapy groups to the GRP receptor TRT alone group, a statistically significant difference was demonstrated for the combined groups by day 30, postdose administration. These data demonstrate that GRP receptor-targeted radiation therapy, using (177)Lu-DOTA-8-AOC-BBN(7-14)NH(2), used either alone or in combination with conventional chemotherapy, can suppress the growth of androgen- independent prostate cancer (AIPC).     

CXCL12受体抑制剂调控三阴性乳腺癌放射治疗的敏感性

目的 探讨趋化因子12（CXCL12）受体CXCR4抑制剂AMD3100对人乳腺癌MDA-MB 231细胞裸鼠移植瘤的放射增敏效应及其作用机制。方法 建立人乳腺癌裸鼠移植瘤模型,并随机分为4组：对照组、AMD3100处理组、放射治疗组和联合治疗组（AMD3100+放疗）;称量肿瘤的重量并测量移植瘤的体积,计算放射增敏比,绘制肿瘤生长曲线;实时荧光定量PCR（QPCR）检测CXCR4和表皮生长因子受体（EGFR）基因表达;蛋白质印迹法检测CXCR4、EGFR和基质金属蛋白酶-9（MMP-9）蛋白表达。结果 经统计CXCR4抑制剂AMD3100的放射增敏比为1:45。QPCR结果显示,与对照组比较,CXCR4和EGFR基因的相对表达量在AMD3100处理组、放射治疗组及联合治疗组分别下调60％、45％、82％和56％、48％、73％,差异有统计学意义（P＜0.05）。单纯AMD3100治疗或者放射治疗均能使CXCR4、EGFR表达下调（P＜0.05）,联合治疗较单纯AMD3100治疗和放疗更能显著地抑制CXCR4和EGFR的表达（P＜0.05）。Western blotting结果显示,与对照组比较,CXCR4、EGFR及MMP-9在AMD3100处理组、放射治疗组及联合治疗组中的蛋白相对表达量均下调（P＜0.05）。AMD3100与放疗均可抑制CXCR4、EGFR及MMP-9的表达,两者联用较单一治疗的效果更加显著（P＜0.05）。     

Downregulation of CXCR7 inhibits proliferative capacity and stem cell-like properties in breast cancer stem cells

Breast cancer stem cells (bCSCs) are considered an obstacle in breast cancer therapy because they exhibit long-term proliferative potential, phenotypic plasticity and high resistance to the current therapeutics. CXC chemokine receptor type 7 (CXCR7), which provides a growth advantage to breast cancer cells, has recently been demonstrated to play an important role in the maintenance of stem cell-like properties in the CSCs of glioblastoma and lung cancer, yet its role in bCSCs remains elusive. In this study, CD44⁺/CD24^low bCSC-enriched cells (bCSCs for short) were isolated from MCF-7 cells, and CXCR7 was stably knocked down in bCSCs via lentivirus-mediated transduction with CXCR7 short hairpin RNA (shRNA). Knockdown of CXCR7 in bCSCs decreased the proportion of CD44⁺/CD24^low cells, and markedly reduced the clonogenicity of the cells. Moreover, silencing of CXCR7 downregulated the expression of stem cell markers, such as aldehyde dehydrogenase 1 (ALDH1), Oct4, and Nanog. In addition, CXCR7 silencing in bCSCs suppressed cell proliferation and G1/S transition in vitro, and delayed tumor growth in vivo in a xenograft mouse model. In situ immunohistochemical analysis revealed a reduction in Ki-67 expression and enhanced apoptosis in the xenograft tumors as a result of CXCR7 silencing. Furthermore, combined treatment with CXCR7 silencing and epirubicin displayed an outstanding anti-tumor effect compared with either single treatment. Our study demonstrates that CXCR7 plays a critical role in the maintenance of stem cell-like properties and promotion of growth in bCSCs, and suggests that CXCR7 may be a candidate target for bCSCs in breast cancer therapy.

     

CXCR4 Inhibition with AMD3100 Sensitizes Prostate Cancer to Docetaxel Chemotherapy

Several in vitro and in vivo models have revealed the key role of CXCR4/CXCL12 axis in tumor-stroma interactions. Stromal cells present in the tumor microenvironment express high levels of CXCL12 protein, directly stimulating proliferation and migration of CXCR4-expressing cancer cells. This specific prosurvival influence of stromal cells on tumor cells is thought to protect them from cytotoxic chemotherapy and is postulated as a possible explanation for the minimal residual disease in hematological and solid cancers. Therefore, CXCR4/CXCL12 signaling is an attractive therapeutic target in cancer, as proven in preclinical leukemia mouse models, where CXCR4 inhibition sensitized cancer cells to conventional chemotherapy. This study investigates whether inhibition of CXCR4 with the specific inhibitor AMD3100 sensitizes human prostate cancer cells to docetaxel. We showed that both mouse and human stromal cell lines have a protective effect on PC3-luc cells by promoting their survival after chemotherapy. Furthermore, we demonstrated that AMD3100 sensitizes PC3-luc cells to docetaxel. In a subcutaneous xenograft mouse model of human prostate carcinoma, we showed that a combination of docetaxel and AMD3100 exerts increased antitumor effect compared with docetaxel alone. We concluded that CXCR4 inhibition chemosensitizes prostate cancer cells, both in vitro and in vivo. To explore the relevance of these findings, we analyzed CXCR4 expression levels in human prostate cancer samples. We found that cancer cells present in bone metastatic lesions express higher CXCR4 levels relative to the cells present in primary tumors and lymph node metastatic lesions. These findings underscore the potential of CXCR4 inhibitors as chemosensitizing agents.     

Natural IAP inhibitor Embelin enhances therapeutic efficacy of ionizing radiation in prostate cancer

Embelin is an active ingredient of traditional herbal medicine that exhibits anti-tumor effects in human prostate cancer cells. However, therapeutic effect of embelin in combination with conventional radiation therapy is not yet determined. In this study, we evaluate the sensitizing potential of embelin on ionizing radiation (IR) in a human prostate cancer model. In vitro, embelin combined with radiation potently suppressed prostate cancer PC-3 cell proliferation that was associated with S and G2/M arrest in cell cycle. Moreover, the combination treatment promoted caspase-independent apoptosis, as evidenced by the increased apoptotic cell death without caspase-3 activation, but not autophagy. Clonogenic survival assay showed that S-phase arrest was required for embelin-mediated radiosensitization. In vivo, embelin significantly improved tumor response to X-ray radiation in the PC-3 xenograft model. Combination therapy produced enhanced tumor growth delay and prolonged time to progression, with minimal systemic toxicity. Immunohistochemistry studies showed that embelin plus IR significantly inhibited cell proliferation, induced apoptosis, and decreased microvessel density in tumors as compared with either treatment alone, suggesting an enhanced combinatory inhibition on tumor suppression and angiogenesis. Our results demonstrate that embelin significantly facilitates tumor suppression by radiation therapy both in vitro and in vivo in the prostate cancer model. This finding warrants embelin as a novel adjuvant therapeutic candidate for the treatment of hormone-refractory prostate cancer that is resistant to radiation therapy.     

Effects of exemestane and tamoxifen in a postmenopausal breast cancer model.

PURPOSE: To optimize treatment strategies for postmenopausal breast cancer patients, we investigated the efficacy of the steroidal aromatase inhibitor exemestane alone or in combination with the antiestrogen tamoxifen in a xenograft model of postmenopausal breast cancer. We also determined the effects of these agents in sequential second-line therapy and the effect of the nonsteroidal aromatase inhibitor letrozole on tumors that progressed on the above treatments. Experimental: Aromatase-transfected human estrogen receptor-positive breast cancer cells (MCF-7Ca) were grown as tumors in ovariectomized athymic mice. Animals received subcutaneous injection with vehicle, tamoxifen, exemestane, tamoxifen plus exemestane, and letrozole. Tumor volumes were measured weekly. RESULTS: All treatments were effective initially in suppressing tumor growth as first-line therapy compared with vehicle treatment. Exemestane suppressed tumor growth to a greater extent than tamoxifen. However, the combination of tamoxifen plus exemestane was more effective than either drug alone. After tumor volumes doubled on initial treatment, the mice were crossed over to receive exemestane or tamoxifen. Tumor growth slowed briefly in mice treated with tamoxifen and crossed over to exemestane, but tumor growth continued unabated in those changed from exemestane to tamoxifen. However, letrozole was effective in both groups as third-line therapy for a limited period. Letrozole as initial single agent was the best overall treatment in terms of the degree of tumor suppression and the length of effectiveness of treatment. CONCLUSION: Exemestane was more effective in controlling tumor growth than tamoxifen. In addition, the combination of exemestane plus tamoxifen was clearly more effective than sequential use of these agents in the tumor model. However, the nonsteroidal aromatase inhibitor letrozole as first-line therapy was overall the most effective treatment in controlling tumor growth.     

CS2164, a novel multi‐target inhibitor against tumor angiogenesis,mitosis and chronic inflammation with anti‐tumor potency

Although inhibitors targeting tumor angiogenic pathway have provided improvement for clinical treatment in patients with various solid tumors, the still very limited anti‐cancer efficacy and acquired drug resistance demand new agents that may offer better clinical benefits. In the effort to find a small molecule potentially targeting several key pathways for tumor development, we designed, discovered and evaluated a novel multi‐kinase inhibitor, CS2164. CS2164 inhibited the angiogenesis‐related kinases (VEGFR2, VEGFR1, VEGFR3, PDGFRα and c‐Kit), mitosis‐related kinase Aurora B and chronic inflammation‐related kinase CSF‐1R in a high potency manner with the IC₅₀ at a single‐digit nanomolar range. Consequently, CS2164 displayed anti‐angiogenic activities through suppression of VEGFR/PDGFR phosphorylation, inhibition of ligand‐dependent cell proliferation and capillary tube formation, and prevention of vasculature formation in tumor tissues. CS2164 also showed induction of G2/M cell cycle arrest and suppression of cell proliferation in tumor tissues through the inhibition of Aurora B‐mediated H3 phosphorylation. Furthermore, CS2164 demonstrated the inhibitory effect on CSF‐1R phosphorylation that led to the suppression of ligand‐stimulated monocyte‐to‐macrophage differentiation and reduced CSF‐1R⁺ cells in tumor tissues. The in vivo animal efficacy studies revealed that CS2164 induced remarkable regression or complete inhibition of tumor growth at well‐tolerated oral doses in several human tumor xenograft models. Collectively, these results indicate that CS2164 is a highly selective multi‐kinase inhibitor with potent anti‐tumor activities against tumor angiogenesis, mitosis and chronic inflammation, which may provide the rationale for further clinical assessment of CS2164 as a therapeutic agent in the treatment of cancer.     

Eribulin mesylate reduces tumor microenvironment abnormality by vascular remodeling in preclinical human breast cancer models

Eribulin mesylate is a synthetic macrocyclic ketone analog of the marine sponge natural product halichondrin B and an inhibitor of microtubule dynamics. Some tubulin‐binding drugs are known to have antivascular (antiangiogenesis or vascular‐disrupting) activities that can target abnormal tumor vessels. Using dynamic contrast‐enhanced MRI analyses, here we show that eribulin induces remodeling of tumor vasculature through a novel antivascular activity in MX‐1 and MDA‐MB‐231 human breast cancer xenograft models. Vascular remodeling associated with improved perfusion was shown by Hoechst 33342 staining and by increased microvessel density together with decreased mean vascular areas and fewer branched vessels in tumor tissues, as determined by immunohistochemical staining for endothelial marker CD31. Quantitative RT‐PCR analysis of normal host cells in the stroma of xenograft tumors showed that eribulin altered the expression of mouse (host) genes in angiogenesis signaling pathways controlling endothelial cell–pericyte interactions, and in the epithelial–mesenchymal transition pathway in the context of the tumor microenvironment. Eribulin also decreased hypoxia‐associated protein expression of mouse (host) vascular endothelial growth factor by ELISA and human CA9 by immunohistochemical analysis. Prior treatment with eribulin enhanced the anti‐tumor activity of capecitabine in the MDA‐MB‐231 xenograft model. These findings suggest that eribulin‐induced remodeling of abnormal tumor vasculature leads to a more functional microenvironment that may reduce the aggressiveness of tumors due to elimination of inner tumor hypoxia. Because abnormal tumor microenvironments enhance both drug resistance and metastasis, the apparent ability of eribulin to reverse these aggressive characteristics may contribute to its clinical benefits.