The HGF/c-MET Pathway Is a Driver and Biomarker of VEGFR-inhibitor Resistance and Vascular Remodeling in Non-Small Cell Lung Cancer

Purpose: Resistance to VEGFR inhibitors is a major obstacle in the treatment of non-small cell lung cancer (NSCLC). We investigated the cellular mechanisms mediating resistance of NSCLCs to VEGFR tyrosine kinase inhibitors.Experimental Design: We generated murine models of human NSCLC and performed targeted inhibition studies with the VEGFR TKIs cediranib and vandetanib. We used species-specific hybridization of microarrays to compare cancer (human) and stromal (mouse) cell transcriptomes of TKI-sensitive and -resistant tumors. We measured tumor microvascular density and vessel tortuosity to characterize the effects of therapy on the tumor vascular bed. Circulating cytokine and angiogenic factor levels in patients enrolled in VEGFR TKI trials were correlated with clinical outcomes.Results: Murine xenograft models of human lung adenocarcinoma were initially sensitive to VEGFR TKIs, but developed resistance to treatment. Species-specific microarray analysis identified increased expression of stromal-derived hepatocyte growth factor (HGF) as a candidate mediator of TKI resistance and its receptor, c-MET, was activated in cancer cells and tumor-associated stroma. A transient increase in hypoxia-regulated molecules in the initial response phase was followed by adaptive changes resulting in a more tortuous vasculature. Forced HGF expression in cancer cells reduced tumor sensitivity to VEGFR TKIs and produced tumors with tortuous blood vessels. Dual VEGFR/c-MET signaling inhibition delayed the onset of the resistant phenotype and prevented the vascular morphology alterations. In patients with cancer receiving VEGFR TKIs, high pretreatment HGF plasma levels correlated with poorer survival.Conclusions: HGF/c-MET pathway mediates VEGFR inhibitor resistance and vascular remodeling in NSCLC. Clin Cancer Res; 23(18); 5489-501. ©2017 AACR.

Treatment of experimental human breast cancer and lung cancer brain metastases in mice by macitentan, a dual antagonist of endothelin receptors, combined with paclitaxel

BACKGROUND

We recently demonstrated that brain endothelial cells and astrocytes protect cancer cells from chemotherapy through an endothelin-dependent signaling mechanism. Here, we evaluated the efficacy of macitentan, a dual endothelin receptor (ETAR and ETBR) antagonist, in the treatment of experimental breast and lung cancer brain metastases.

METHODS

The effect of macitentan on astrocyte- and brain endothelial cell-mediated chemoprotective properties was measured in cytotoxic assays. We compared survival of mice bearing established MDA-MB-231 breast cancer or PC-14 non-small cell lung cancer (NSCLC) brain metastases that were treated with vehicle, macitentan, paclitaxel, or macitentan plus paclitaxel. Cell division, apoptosis, tumor vasculature, and expression of survival-related proteins were assessed by immunofluorescent microscopy.

RESULTS

Cancer cells and tumor-associated endothelial cells expressed activated forms of AKT and MAPK in vehicle- and paclitaxel-treated groups in both metastasis models, but these proteins were downregulated in metastases of mice that received macitentan. The survival-related proteins Bcl2L1, Gsta5, and Twist1 that localized to cancer cells and tumor-associated endothelial cells in vehicle- and paclitaxel-treated tumors were suppressed by macitentan. Macitentan or paclitaxel alone had no effect on survival. However, when macitentan was combined with paclitaxel, we noted a significant reduction in cancer cell division and marked apoptosis of both cancer cells and tumor-associated endothelial cells. Moreover, macitentan plus paclitaxel therapy significantly increased overall survival by producing complete responses in 35 of 35 mice harboring brain metastases.

CONCLUSIONS

Dual antagonism of ETAR and ETBR signaling sensitizes experimental brain metastases to paclitaxel and may represent a new therapeutic option for patients with brain metastases.

Dual Metronomic Chemotherapy with Nab-Paclitaxel and Topotecan Has Potent Antiangiogenic Activity in Ovarian Cancer

There is growing recognition of the important role of metronomic chemotherapy in cancer treatment. On the basis of their unique antiangiogenic effects, we tested the efficacy of nab-paclitaxel, which stimulates thrombospondin-1, and topotecan, which inhibits hypoxia-inducible factor 1-α, at metronomic dosing for the treatment of ovarian carcinoma. In vitro and in vivo SKOV3ip1, HeyA8, and HeyA8-MDR (taxane-resistant) orthotopic models were used to examine the effects of metronomic nab-paclitaxel and metronomic topotecan. We examined cell proliferation (Ki-67), apoptosis (cleaved caspase-3), and angiogenesis (microvessel density, MVD) in tumors obtained at necropsy. In vivo therapy experiments demonstrated treatment with metronomic nab-paclitaxel alone and in combination with metronomic topotecan resulted in significant reductions in tumor weight (62% in the SKOV3ip1 model, P < 0.01 and 96% in the HeyA8 model, P < 0.03) compared with vehicle (P < 0.01). In the HeyA8-MDR model, metronomic monotherapy with either cytotoxic agent had modest effects on tumor growth, but combination therapy decreased tumor burden by 61% compared with vehicle (P < 0.03). The greatest reduction in MVD (P < 0.05) and proliferation was seen in combination metronomic therapy groups. Combination metronomic therapy resulted in prolonged overall survival in vivo compared with other groups (P < 0.001). Tube formation was significantly inhibited in RF-24 endothelial cells exposed to media conditioned with metronomic nab-paclitaxel alone and media conditioned with combination metronomic nab-paclitaxel and metronomic topotecan. The combination of metronomic nab-paclitaxel and metronomic topotecan offers a novel, highly effective therapeutic approach for ovarian carcinoma that merits further clinical development.

Abstract 5463: Role of the endothelin axis in astrocyte and endothelial cell mediated chemoprotection of cancer cells

Background. Recent evidence suggests that astrocytes protect cancer cells from chemotherapy by stimulating the upregulation of anti-apoptotic genes in cancer cells. We investigated the possibility that activation of the endothelin axis orchestrates survival gene expression and chemoprotection in MDA-MB-231 breast cancer cells and H226 lung cancer cells.

Methods. Cancer cells, murine astrocytes, and murine fibroblasts were cultured in isolation and expression of endothelin (ET) peptides and ET receptors (ETAR and ETBR) was compared with expression on cancer cells and astrocytes (or cancer cells and fibroblasts) that were co-incubated for 48 hours. Type-specific endothelin receptor antagonists were used to evaluate the contribution of ETAR and ETBR to astrocyte-induced activation of the protein kinase B (AKT)/mitogen-activated protein kinase (MAPK) signal transduction pathways, anti-apoptotic gene expression, and chemoprotection of cancer cells. We also investigated the chemoprotective potential of brain endothelial cells and microglial cells.

Results. Gap junction signaling between astrocytes and MDA-MB-231 cancer cells stimulates upregulation of interleukin 6 (IL-6) and IL-8 expression in cancer cells, which increases ET-1 production from astrocytes and ET receptor expression on cancer cells. ET-1 signals for activation of AKT/MAPK and upregulation of survival proteins that protect cancer cells from taxol. Brain endothelial cell-mediated chemoprotection of cancer cells also involves endothelin signaling. Dual antagonism of ETAR and ETBR is required to abolish astrocyte- and endothelial cell-mediated chemoprotection.

Conclusions. Bidirectional signaling between astrocytes and cancer cells involves upregulation and activation of the endothelin axis, which protects cancer cells from cytotoxicity induced by chemotherapeutic drugs.

Citation Format: Mark S. Kim, Hyun Jin Choi, Ho-Jeong Lee, Junqin He, Qiuyu We, Robert R. Langley, Sin-Jin Kim, Isaiah J. Fidler. Role of the endothelin axis in astrocyte and endothelial cell mediated chemoprotection of cancer 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 5463. doi:10.1158/1538-7445.AM2015-5463

Macitentan, a Dual Endothelin Receptor Antagonist, in Combination with Temozolomide Leads to Glioblastoma Regression and Long-term Survival in Mice

PURPOSE

The objective of the study was to determine whether astrocytes and brain endothelial cells protect glioma cells from temozolomide through an endothelin-dependent signaling mechanism and to examine the therapeutic efficacy of the dual endothelin receptor antagonist, macitentan, in orthotopic models of human glioblastoma.

EXPERIMENTAL DESIGN

We evaluated several endothelin receptor antagonists for their ability to inhibit astrocyte- and brain endothelial cell-induced protection of glioma cells from temozolomide in chemoprotection assays. We compared survival in nude mice bearing orthotopically implanted LN-229 glioblastomas or temozolomide-resistant (LN-229(Res) and D54(Res)) glioblastomas that were treated with macitentan, temozolomide, or both. Tumor burden was monitored weekly with bioluminescence imaging. The effect of therapy on cell division, apoptosis, tumor-associated vasculature, and pathways associated with cell survival was assessed by immunofluorescent microscopy.

RESULTS

Only dual endothelin receptor antagonism abolished astrocyte- and brain endothelial cell-mediated protection of glioma cells from temozolomide. In five independent survival studies, including temozolomide-resistant glioblastomas, 46 of 48 (96%) mice treated with macitentan plus temozolomide had no evidence of disease (P < 0.0001), whereas all mice in other groups died. In another analysis, macitentan plus temozolomide therapy was stopped in 16 mice after other groups had died. Only 3 of 16 mice eventually developed recurrent disease, 2 of which responded to additional cycles of macitentan plus temozolomide. Macitentan downregulated proteins associated with cell division and survival in glioma cells and associated endothelial cells, which enhanced their sensitivity to temozolomide.

CONCLUSIONS

Macitentan plus temozolomide are well tolerated, produce durable responses, and warrant clinical evaluation in glioblastoma patients.

Modulation of the cancer cell transcriptome by culture media formulations and cell density

We investigated how varying the composition of cell culture formulations and growing cancer cells at different densities might affect tumor cell genotype. Specifically, we compared gene expression profiles generated by human MDA‑MB‑231 breast cancer cells cultured in different media [minimum essential medium (MEM), Dulbecco's modified Eagle's medium (DMEM), or Roswell Park Memorial Institute (RPMI)‑1640 medium] containing different concentrations of fetal bovine serum (FBS) or different sera (equine or bovine) that were grown at different cell densities. More than 2,000 genes were differentially modulated by at least a 2‑fold difference when MDA‑MB‑231 cancer cells were 90% confluent and compared with cultures that were 50% confluent. Altering the concentration of serum produced an even more pronounced effect on MDA‑MB‑231 cancer cell gene expression in that 2,981 genes were differentially expressed in a comparison between cells cultured in 0.1% FBS and same cell density cultures that were maintained in 10% FBS. A comparison between MDA‑MB‑231 cancer cells that were 90% confluent in MEM, DMEM, or RPMI‑1640 media, all containing 10% FBS, resulted in 8,925 differentially expressed genes. Moreover, one‑quarter (25.6%) of genes from our genome‑wide expression analysis were expressed at significantly different levels by cells grown in MEM, DMEM, or RPMI‑1640 media. Genes associated with epithelial‑mes-enchymal transition (EMT) were among the genes that were differentially modulated by cells grown in different cell culture formulations and these genes were verified at the protein level. Collectively, these results underscore the importance of accurate reporting and maintenance of uniform culture conditions to ensure reproducible results.

Role of the endothelin axis in astrocyte- and endothelial cell-mediated chemoprotection of cancer cells

BACKGROUND

Recent evidence suggests that astrocytes protect cancer cells from chemotherapy by stimulating upregulation of anti-apoptotic genes in those cells. We investigated the possibility that activation of the endothelin axis orchestrates survival gene expression and chemoprotection in MDA-MB-231 breast cancer cells and H226 lung cancer cells.

METHODS

Cancer cells, murine astrocytes, and murine fibroblasts were grown in isolation, and expression of endothelin (ET) peptides and ET receptors (ETAR and ETBR) compared with expression on cancer cells and astrocytes (or cancer cells and fibroblasts) that were co-incubated for 48 hours. Type-specific endothelin receptor antagonists were used to evaluate the contribution of ETAR and ETBR to astrocyte-induced activation of the protein kinase B (AKT)/mitogen-activated protein kinase (MAPK) signal transduction pathways, anti-apoptotic gene expression, and chemoprotection of cancer cells. We also investigated the chemoprotective potential of brain endothelial cells and microglial cells.

RESULTS

Gap junction signaling between MDA-MB-231 cancer cells and astrocytes stimulates upregulation of interleukin 6 (IL-6) and IL-8 expression in cancer cells, which increases ET-1 production from astrocytes and ET receptor expression on cancer cells. ET-1 signals for activation of AKT/MAPK and upregulation of survival proteins that protect cancer cells from taxol. Brain endothelial cell-mediated chemoprotection of cancer cells also involves endothelin signaling. Dual antagonism of ETAR and ETBR is required to abolish astrocyte- and endothelial cell-mediated chemoprotection.

CONCLUSIONS

Bidirectional signaling between astrocytes and cancer cells involves upregulation and activation of the endothelin axis, which protects cancer cells from cytotoxicity induced by chemotherapeutic drugs.

Antiangiogenic Therapy with Human Apolipoprotein(a) Kringle V and Paclitaxel in a Human Ovarian Cancer Mouse Model

INTRODUCTION: The present study compared the effect of combination therapy using human apolipoprotein(a) kringle V (rhLK8) to conventional chemotherapy with paclitaxel for human ovarian carcinoma producing high or low levels of vascular endothelial growth factor (VEGF). MATERIALS AND METHODS: Human ovarian carcinoma cells producing high (SKOV3ip1) or low (HeyA8) levels of VEGF were implanted into the peritoneal cavity of female nude mice. Seven days later, mice were randomized into four groups: control (vehicle), paclitaxel [5 mg/kg, weekly intraperitoneal (i.p.) injection], rhLK8 (50 mg/kg, daily i.p. injection), or the combination of paclitaxel and rhLK8. Mice were treated for 4 weeks and examined by necropsy. RESULTS: In mice implanted with SKOV3ip1 cells, rhLK8 treatment had no significant effect on tumor incidence or the volume of ascites but induced a significant decrease in tumor weight compared with control mice. Paclitaxel significantly reduced tumor weight and ascites volume, and combination treatment with paclitaxel and rhLK8 had an additive therapeutic effect. Similarly, in HeyA8 mice, the effect of combination treatment on tumor weight and tumor incidence was statistically significantly greater than that of paclitaxel or rhLK8 alone. Immunohistochemical analysis showed a significant decrease in microvessel density and a marked increase of apoptosis in tumor and tumor-associated endothelial cells in response to combination treatment with paclitaxel and rhLK8. CONCLUSION: Collectively, these results suggest that antiangiogenic therapy with rhLK8 in combination with taxane-based conventional chemotherapy could be effective for the treatment of ovarian carcinomas, regardless of VEGF status.

Coronary microvascular pericytes are the cellular target of sunitinib malate-induced cardiotoxicity

Sunitinib malate is a multitargeted receptor tyrosine kinase inhibitor used in the treatment of human malignancies. A substantial number of sunitinib-treated patients develop cardiac dysfunction, but the mechanism of sunitinib-induced cardiotoxicity is poorly understood. We show that mice treated with sunitinib develop cardiac and coronary microvascular dysfunction and exhibit an impaired cardiac response to stress. The physiological changes caused by treatment with sunitinib are accompanied by a substantial depletion of coronary microvascular pericytes. Pericytes are a cell type that is dependent on intact platelet-derived growth factor receptor (PDGFR) signaling but whose role in the heart is poorly defined. Sunitinib-induced pericyte depletion and coronary microvascular dysfunction are recapitulated by CP-673451, a structurally distinct PDGFR inhibitor, confirming the role of PDGFR in pericyte survival. Thalidomide, an anticancer agent that is known to exert beneficial effects on pericyte survival and function, prevents sunitinib-induced pericyte cell death in vitro and prevents sunitinib-induced cardiotoxicity in vivo in a mouse model. Our findings suggest that pericytes are the primary cellular target of sunitinib-induced cardiotoxicity and reveal the pericyte as a cell type of concern in the regulation of coronary microvascular function. Furthermore, our data provide preliminary evidence that thalidomide may prevent cardiotoxicity in sunitinib-treated cancer patients.

DNA-damage-induced nuclear export of precursor microRNAs is regulated by the ATM-AKT pathway

Expression of microRNAs (miRNAs) involves transcription of miRNA genes and maturation of the primary transcripts. Recent studies have shown that posttranscriptional processing of primary and precursor miRNAs is induced after DNA damage through regulatory RNA-binding proteins in the Drosha and Dicer complexes, such as DDX5 and KSRP. However, little is known about the regulation of nuclear export of pre-miRNAs in the DNA-damage response, a critical step in miRNA maturation. Here, we show that nuclear export of pre-miRNAs is accelerated after DNA damage in an ATM-dependent manner. The ATM-activated AKT kinase phosphorylates Nup153, a key component of the nucleopore, leading to enhanced interaction between Nup153 and Exportin-5 (XPO5) and increased nuclear export of pre-miRNAs. These findings define an important role of DNA-damage signaling in miRNA transport and maturation.

ATP11B mediates platinum resistance in ovarian cancer

Platinum compounds display clinical activity against a wide variety of solid tumors; however, resistance to these agents is a major limitation in cancer therapy. Reduced platinum uptake and increased platinum export are examples of resistance mechanisms that limit the extent of DNA damage. Here, we report the discovery and characterization of the role of ATP11B, a P-type ATPase membrane protein, in cisplatin resistance. We found that ATP11B expression was correlated with higher tumor grade in human ovarian cancer samples and with cisplatin resistance in human ovarian cancer cell lines. ATP11B gene silencing restored the sensitivity of ovarian cancer cell lines to cisplatin in vitro. Combined therapy of cisplatin and ATP11B-targeted siRNA significantly decreased cancer growth in mice bearing ovarian tumors derived from cisplatin-sensitive and -resistant cells. In vitro mechanistic studies on cellular platinum content and cisplatin efflux kinetics indicated that ATP11B enhances the export of cisplatin from cells. The colocalization of ATP11B with fluorescent cisplatin and with vesicular trafficking proteins, such as syntaxin-6 (STX6) and vesicular-associated membrane protein 4 (VAMP4), strongly suggests that ATP11B contributes to secretory vesicular transport of cisplatin from Golgi to plasma membrane. In conclusion, inhibition of ATP11B expression could serve as a therapeutic strategy to overcome cisplatin resistance.

The biology of brain metastasis

BACKGROUND

It is estimated that at least 200 000 cases of brain metastases occur each year in the US, which is 10 times the number of patients diagnosed with primary brain tumors. Brain metastasis is associated with poor prognosis, neurological deterioration, diminished quality of life, and extremely short survival. Favorable interactions between tumor cells and cerebral microvascular endothelial cells encourage tumor growth in the central nervous system, while tumor cell interactions with astrocytes protect brain metastases from the cytotoxic effects of chemotherapy.

CONTENT

We review the pathogenesis of brain metastasis and emphasize the contributions of microvascular endothelial cells and astrocytes to disease progression and therapeutic resistance. Animal models used to study brain metastasis are also discussed.

SUMMARY

Brain metastasis has many unmet clinical needs. There are few clinically relevant tumor models and no targeted therapies specific for brain metastases, and the mean survival for untreated patients is 5 weeks. Improved clinical outcomes are dependent on an enhanced understanding of the metastasis-initiating population of cells and the identification of microenvironmental factors that encourage disease progression in the central nervous system.

Crosstalk between the DNA damage response pathway and microRNAs

MicroRNAs (miRNAs) are a family of small, non-coding RNAs that control gene expression at the post-transcriptional level by destabilizing and inhibiting translation of their target messenger RNAs. MiRNAs are involved in the regulation of a number of fundamental biological processes, and their dysregulation is thought to contribute to several disease processes. Emerging evidence suggests that miRNAs also play a critical role in protecting the heritable genome by contributing to the regulation of the DNA damage response. Consequently, much recent investigative effort has been directed towards an improved understanding of how miRNAs are regulated in response to DNA damage. In this review, we discuss the most recent findings regarding the regulation of miRNA expression and the functional roles of miRNAs in the DNA damage response.

Selection of brain metastasis-initiating breast cancer cells determined by growth on hard agar

An approach that facilitates rapid isolation and characterization of tumor cells with enhanced metastatic potential is highly desirable. Here, we demonstrate that plating GI-101A human breast cancer cells on hard (0.9%) agar selects for the subpopulation of metastasis-initiating cells. The agar-selected cells, designated GI-AGR, were homogeneous for CD44(+) and CD133(+) and five times more invasive than the parental GI-101A cells. Moreover, mice injected with GI-AGR cells had significantly more experimental brain metastases and shorter overall survival than did mice injected with GI-101A cells. Comparative gene expression analysis revealed that GI-AGR cells were markedly distinct from the parental cells but shared an overlapping pattern of gene expression with the GI-101A subline GI-BRN, which was generated by repeated in vivo recycling of GI-101A cells in an experimental brain metastasis model. Data mining on 216 genes shared between GI-AGR and GI-BRN breast cancer cells suggested that the molecular phenotype of these cells is consistent with that of cancer stem cells and the aggressive basal subtype of breast cancer. Collectively, these results demonstrate that analysis of cell growth in a hard agar assay is a powerful tool for selecting metastasis-initiating cells in a heterogeneous population of breast cancer cells, and that such selected cells have properties similar to those of tumor cells that are selected based on their potential to form metastases in mice.

Biological roles of the Delta family Notch ligand Dll4 in tumor and endothelial cells in ovarian cancer

Emerging evidence suggests that the Notch/Delta-like ligand 4 (Dll4) pathway may offer important new targets for antiangiogenesis approaches. In this study, we investigated the clinical and biological significance of Dll4 in ovarian cancer. Dll4 was overexpressed in 72% of tumors examined in which it was an independent predictor of poor survival. Patients with tumors responding to anti-VEGF therapy had lower levels of Dll4 than patients with stable or progressive disease. Under hypoxic conditions, VEGF increased Dll4 expression in the tumor vasculature. Immobilized Dll4 also downregulated VEGFR2 expression in endothelial cells directly through methylation of the VEGFR2 promoter. RNAi-mediated silencing of Dll4 in ovarian tumor cells and tumor-associated endothelial cells inhibited cell growth and angiogenesis, accompanied by induction of hypoxia in the tumor microenvironment. Combining Dll4-targeted siRNA with bevacizumab resulted in greater inhibition of tumor growth, compared with control or treatment with bevacizumab alone. Together, our findings establish that Dll4 plays a functionally important role in both the tumor and endothelial compartments of ovarian cancer and that targeting Dll4 in combination with anti-VEGF treatment might improve outcomes of ovarian cancer treatment.

Abstract 3269: VEGF inhibitor resistance is associated with stromal EGFR activation and normalized revascularization in an orthotopic model of lung adenocarcinoma

Therapeutic resistance to angiogenesis inhibitors represents a major obstacle in the treatment of non-small cell lung cancer (NSCLC). Previously, we reported that acquired resistance of subcutaneous murine models of NSCLC to the anti-vascular endothelial growth factor (VEGF) antibody bevacizumab (BV) was mediated by upregulation and activation of the epidermal growth factor receptor (EGFR) signaling pathway in stromal cells. Here, we investigated the effects of BV and dual VEGFR/EGFR inhibition, and the mechanisms of therapeutic resistance in H441 NSCLC orthotopic tumors. Short-term BV treatment (2 weeks) resulted in a significant tumor volume reduction compared with vehicle-treated tumors (p=0.026). For survival analysis, tumor-bearing mice were randomized to receive vehicle, erlotinib (E), BV, erlotinib + BV (E + B), or the VEGFR/EGFR inhibitor vandetanib (V), until moribund. All therapies significantly prolonged survival compared with vehicle (p&lt;0.0001; E vs. vehicle p&lt;0.05). Long-term BV administration improved survival compared with E (median survival 77 vs. 58 days, p=0.00015); however, both E + BV and V treatments (median survival 101 and 91 days, respectively) prolonged survival compared with E or BV alone (p=0.0001 E + BV vs. E or BV; p=0.0004 V vs. E; p=0.022 V vs. BV). Microvessel density (MVD) was strongly decreased in BV-sensitive tumors compared with 2 week vehicle treatment (p=0.0008); however, tumors resistant to BV or dual VEGFR/EGFR inhibition showed revascularization with increased MVD compared with BV-sensitive tumors (p=0.045). In erlotinib-resistant group MVD was significantly lower than in BV-resistant tumors (p=0.034). Levels of p-EGFR increased in BV-resistant tumors compared with controls (p=0.039) and co-localized with the stroma supporting large, normalized vessels. This signaling was suppressed in tumors resistant to VEGFR/EGFR targeting compared with both controls and BV-resistant tumors (p=0.0001 E + BV vs. vehicle; p=0.0008 E + BV vs. BV; p = 0.011 V vs. vehicle; p=0.009 V vs. BV), demonstrating persistent EGFR blockade with treatment. Pericyte coverage increased in BV-resistant tumors compared with controls and BV-sensitive tumors (p=0.003 BV vs. vehicle; p&lt;0.0001 BV progression vs. BV 2 weeks). In tumors resistant to erlotinib or VEGFR/EGFR inhibition, pericyte coverage was reduced to levels comparable to controls (p=0.001 E vs. BV; p=0.054 E + BV vs. BV; p=0.007 V vs. BV). These findings demonstrate that in an orthotopic NSCLC model, resistance to BV is associated with tumor revascularization, featuring large, pericyte-covered vessels with increased perivascular EGFR activation. Dual VEGFR/EGFR blockade abrogates the BV-induced increase in pericyte coverage and delays the emergence of resistance. Stromal EGFR may contribute to VEGF inhibitor resistance through activation on perivascular cells.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3269. doi:10.1158/1538-7445.AM2011-3269

Upregulated stromal EGFR and vascular remodeling in mouse xenograft models of angiogenesis inhibitor-resistant human lung adenocarcinoma

Angiogenesis is critical for tumor growth and metastasis, and several inhibitors of angiogenesis are currently in clinical use for the treatment of cancer. However, not all patients benefit from antiangiogenic therapy, and those tumors that initially respond to treatment ultimately become resistant. The mechanisms underlying this, and the relative contributions of tumor cells and stroma to resistance, are not completely understood. Here, using species-specific profiling of mouse xenograft models of human lung adenocarcinoma, we have shown that gene expression changes associated with acquired resistance to the VEGF inhibitor bevacizumab occurred predominantly in stromal and not tumor cells. In particular, components of the EGFR and FGFR pathways were upregulated in stroma, but not in tumor cells. Increased activated EGFR was detected on pericytes of xenografts that acquired resistance and on endothelium of tumors with relative primary resistance. Acquired resistance was associated with a pattern of pericyte-covered, normalized revascularization, whereas tortuous, uncovered vessels were observed in relative primary resistance. Importantly, dual targeting of the VEGF and EGFR pathways reduced pericyte coverage and increased progression-free survival. These findings demonstrated that alterations in tumor stromal pathways, including the EGFR and FGFR pathways, are associated with, and may contribute to, resistance to VEGF inhibitors and that targeting these pathways may improve therapeutic efficacy. Understanding stromal signaling may be critical for developing biomarkers for angiogenesis inhibitors and improving combination regimens.

The seed and soil hypothesis revisited--the role of tumor-stroma interactions in metastasis to different organs

The fact that certain tumors exhibit a predilection for metastasis to specific organs has been recognized for well over a century now. An extensive body of clinical data and experimental research has confirmed Stephen Paget's original "seed and soil" hypothesis that proposed the organ-preference patterns of tumor metastasis are the product of favorable interactions between metastatic tumor cells (the "seed") and their organ microenvironment (the "soil"). Indeed, many of the first-line therapeutic regimens, currently in use for the treatment of human cancer are designed to target cancer cells (such as chemotherapy) and also to modulate the tumor microenvironment (such as antiangiogenic therapy). While some types of tumors are capable of forming metastases in virtually every organ in the body, the most frequent target organs of metastasis are bone, brain, liver and the lung. In this review, we discuss how tumor-stromal interactions influence metastasis in each of these organs.

Role of the gp85/trans-sialidases in Trypanosoma cruzi tissue tropism: preferential binding of a conserved peptide motif to the vasculature in vivo

Background

Transmitted by blood-sucking insects, the unicellular parasite Trypanosoma cruzi is the causative agent of Chagas' disease, a malady manifested in a variety of symptoms from heart disease to digestive and urinary tract dysfunctions. The reasons for such organ preference have been a matter of great interest in the field, particularly because the parasite can invade nearly every cell line and it can be found in most tissues following an infection. Among the molecular factors that contribute to virulence is a large multigene family of proteins known as gp85/trans-sialidase, which participates in cell attachment and invasion. But whether these proteins also contribute to tissue homing had not yet been investigated. Here, a combination of endothelial cell immortalization and phage display techniques has been used to investigate the role of gp85/trans-sialidase in binding to the vasculature.

Methods

Bacteriophage expressing an important peptide motif (denominated FLY) common to all gp85/trans-sialidase proteins was used as a surrogate to investigate the interaction of this motif with the endothelium compartment. For that purpose phage particles were incubated with endothelial cells obtained from different organs or injected into mice intravenously and the number of phage particles bound to cells or tissues was determined. Binding of phages to intermediate filament proteins has also been studied.

Findings and Conclusions

Our data indicate that FLY interacts with the endothelium in an organ-dependent manner with significantly higher avidity for the heart vasculature. Phage display results also show that FLY interaction with intermediate filament proteins is not limited to cytokeratin 18 (CK18), which may explain the wide variety of cells infected by the parasite. This is the first time that members of the intermediate filaments in general, constituted by a large group of ubiquitously expressed proteins, have been implicated in T. cruzi cell invasion and tissue homing.

Chagas' disease, caused by the protozoon Trypanosoma cruzi, is an ailment affecting approximately 12–14 million people in Iberoamerica and is becoming increasingly important in North America and Europe as a result of migratory currents. The parasite invades mainly cells of the heart or the walls of the digestive tract. The patients with symptoms develop heart disease or gastrointestinal motor disorders. We and others have implicated the T. cruzi gp85/trans-sialidase surface protein family in the attachment of the parasite to the host cells. These proteins share a peptide motif called FLY. The involvement of FLY in parasite interaction with endothelial cells from different organs has been studied using bacteriophages expressing the FLY peptide as surrogates. We found that phages expressing FLY bind to endothelial cells in an organ dependent manner, particularly in the heart. Also, this peptide binds strongly to intermediate cell filaments, like cytokeratins and vimentin. These results indicate that FLY might be an important contributor to tissue tropism. It also supports the notion that the vasculature and the endothelial cells are important players in Chagas' disease. These data may have important implications in the pathology of Chagas' disease and novel therapeutic approaches for patients afflicted with this disease.

Regulation of tumor angiogenesis by EZH2

Although VEGF-targeted therapies are showing promise, new angiogenesis targets are needed to make additional gains. Here, we show that increased Zeste homolog 2 (EZH2) expression in either tumor cells or in tumor vasculature is predictive of poor clinical outcome. The increase in endothelial EZH2 is a direct result of VEGF stimulation by a paracrine circuit that promotes angiogenesis by methylating and silencing vasohibin1 (vash1). Ezh2 silencing in the tumor-associated endothelial cells inhibited angiogenesis mediated by reactivation of VASH1, and reduced ovarian cancer growth, which is further enhanced in combination with ezh2 silencing in tumor cells. Collectively, these data support the potential for targeting ezh2 as an important therapeutic approach.

Vimentin is a novel anti-cancer therapeutic target; insights from in vitro and in vivo mice xenograft studies

BACKGROUND

Vimentin is a ubiquitous mesenchymal intermediate filament supporting mechano-structural integrity of quiescent cells while participating in adhesion, migration, survival, and cell signaling processes via dynamic assembly/disassembly in activated cells. Soft tissue sarcomas and some epithelial cancers exhibiting "epithelial to mesenchymal transition" phenotypes express vimentin. Withaferin-A, a naturally derived bioactive compound, may molecularly target vimentin, so we sought to evaluate its effects on tumor growth in vitro and in vivo thereby elucidating the role of vimentin in drug-induced responses.

METHODS AND FINDINGS

Withaferin-A elicited marked apoptosis and vimentin cleavage in vimentin-expressing tumor cells but significantly less in normal mesenchymal cells. This proapoptotic response was abrogated after vimentin knockdown or by blockade of caspase-induced vimentin degradation via caspase inhibitors or overexpression of mutated caspase-resistant vimentin. Pronounced anti-angiogenic effects of Withaferin-A were demonstrated, with only minimal effects seen in non-proliferating endothelial cells. Moreover, Withaferin-A significantly blocked soft tissue sarcoma growth, local recurrence, and metastasis in a panel of soft tissue sarcoma xenograft experiments. Apoptosis, decreased angiogenesis, and vimentin degradation were all seen in Withaferin-A treated specimens.

CONCLUSIONS

In light of these findings, evaluation of Withaferin-A, its analogs, or other anti-vimentin therapeutic approaches in soft tissue sarcoma and "epithelial to mesenchymal transition" clinical contexts is warranted.

Abstract 376: Increased HGF is associated with resistance to VEGFR tyrosine kinase inhibitors (TKIs) in non-small cell lung cancer (NSCLC)

Emergence of therapeutic resistance to angiogenesis inhibitors, the mechanisms of which are poorly understood, remains a major obstacle in treatment of NSCLC patients. Previously we reported that mechanisms governing resistance to anti-angiogenic therapy may involve both tumor and stromal cells in the tumor microenvironment. In this study we investigated potential mechanisms of resistance to the multi-tyrosine kinase inhibitors cediranib (AZD2171, Recentin®) and vandetanib (ZD6474, Zactima®) using NSCLC xenografts treated either for 2 weeks (sensitive tumors) or until resistance occurred. Quantification of TUNEL+ staining using laser scanning cytometry (LSC) showed increased apoptosis in H1975 xenografts sensitive to cediranib (p&lt;0.01) and vandetanib (p&lt;0.05) when compared with controls, whereas no changes were noticed at time of resistance. Microvessel density (MVD) was significantly increased in resistant H1975 xenografts compared with controls (p&lt;0.05) and sensitive tumors (p&lt;0.01), whereas in A549 model, vandetanib-resistance was associated with an angiogenic independent phenotype. To investigate stromal mechanisms of Vascular Endothelial Growth Factor Receptor (VEGFR) TKI resistance, we characterized the stromal angiogenic gene expression profiles of H1975 sensitive and resistant tumors using a mouse-specific gene expression array (mouseWG-6 v2 Expression BeadChip, Illumina®). Differentially modulated genes were selected based on a p&lt;0.005 of the univariate t-test and at least a 1.5 fold-change in expression and cross-referenced to defined list(s) of angiogenesis-related genes. Stromal Hgf (hepatocyte growth factor) was up-regulated in VEGFR TKI-resistant xenografts compared to sensitive tumors. Hgf up-regulation was confirmed at the protein level using immunofluorescent staining and confocal microscopy. HGF protein levels were strongly decreased after 2 weeks of treatment with cediranib and vandetanib (p&lt;0.01), whereas a significant increase in HGF was observed in resistant xenografts (p&lt;0.01). To assess whether HGF upregulation contributes to tumor resistance to TKIs, we implanted HGF-overexpressing and vector control HCC827 NSCLC cells into nude mice. In HCC827-vector control xenografts, cediranib inhibited tumor growth by 93%, whereas a 60% of growth inhibition was observed in HGF-overexpressing tumors. These data agree favorably with our previous analysis of clinical specimens from patients with stage IIIB/IV NSCLC that identified HGF as a predictive marker of resistance to vandetanib treatment alone when compared to chemotherapy or the combination of chemotherapy and vandetanib (p=0.033). Our results suggest that HGF up-regulation may resistance to VEGFR pathway inhibition and that the HGF/MET axis may represent a crucial target for NSCLCs that are resistant to anti-angiogenic therapy.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 376.

Abstract 3428: Astrocytes upregulate survival genes in tumor cells and induce protection from chemotherapy

Background. In the USA, more than 40% of cancer patients develop brain metastasis. The median survival of untreated patients is 1-2 months which may be extended to 6 months with conventional therapy. The resistance of tumor cells growing in the brain to chemotherapy has been attributed to the blood-brain barrier (BBB). Recent data, however, reveal that tumor cells growing in the brain release VEGF that leads to vascular permeability, ruling out that the BBB is a sole mechanism of drug resistance. Brain metastases are surrounded and infiltrated by activated astrocytes whose role in physiology is to protect neurons from toxicity. We became intrigued by the possibility that tumor cells exploit astrocytes for protection from apoptosis induced by chemotherapeutic drugs.

Material and Methods. Human breast cancer cells (MDA231) and human lung cancer cells (PC14Br4) were co-cultured with GFP-labeled murine astrocytes or NIH3T3 fibroblasts. Chemosensitivity assays against P-glycoprotein (P-gp)-1-associated chemotherapeutic agents, such as paclitaxel, adriamycin, vinblastine, and vincristine, or P-gp-1-dissociated agents such as 5-FU and cisplatinum, were performed by propidium iodide staining and FACS analysis. The development of tumor cell resistance from chemotherapeutic agents was correlated with gap junction communication and expression of survival genes. Identified genes were knocked-down by SiRNA and chemosensitivity was repeated for functional validation. Lastly, to confirm the influence of the microenvironment, tumor cells were first co-cultured with murine astrocytes or fibroblasts and then cultured with either murine astrocytes or fibroblasts. Chemosensitivity assays and gene arrays were performed.

Results. Direct cultures of murine astrocytes (but not fibroblasts) with human breast cancer cells or lung cancer cells protected the tumor cells against all tested chemotherapeutic agents, correlating with upregulation of survival genes including GSTA5, BCL2L1, and TWIST1, and activation of Akt and MAPK pathways in the tumor cells. The upregulation of the survival genes and consequent drug resistance were dependent on direct contact between the astrocytes and tumor cells through gap junctions. Knocking down the genes in the tumor cells using specific SiRNA rendered the tumor cells sensitive to the chemotherapeutic agents. The gene expression profiles and chemoresistance were transient, i.e., loss of direct contact of tumor cells with murine astrocytes resulted in loss of resistance and downregulation of the survival genes.

Conclusion. Our data clearly demonstrate that host cells, e.g., astrocytes, influence the biological behavior of tumor cells and reinforces the contention that successful therapy of brain metastasis requires targeting both tumor cells and the organ microenvironment.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3428.

Abstract 642: Vimentin is a novel anticancer therapeutic target

Vimentin is a ubiquitous mesenchymal intermediate filament supporting mechano-structural integrity of quiescent cells while participating in adhesion, migration, survival, and cell signaling processes via dynamic assembly/disassembly in activated cells. Soft tissue sarcomas and some epithelial cancers exhibiting “epithelial to mesenchymal transition” phenotypes express vimentin. Withaferin-A (WFA), a naturally derived bioactive compound, may molecularly target vimentin, so we sought to evaluate its effects on tumor growth in vitro and in vivo thereby elucidating the role of vimentin in drug-induced responses. WFA elicited marked apoptosis and vimentin cleavage in vimentin-expressing tumor cells but significantly less in normal mesenchymal cells. This proapoptotic response was abrogated after vimentin knockdown or by blockade of caspase-induced vimentin degradation via caspase inhibitors or overexpression of mutated caspase-resistant vimentin. Pronounced anti-angiogenic effects of WFA were demonstrated, with only minimal effects seen in non-proliferating endothelial cells. Moreover, WFA significantly blocked soft tissue sarcoma growth, local recurrence, and metastasis in a panel of soft tissue sarcoma xenograft experiments. Apoptosis, decreased angiogenesis, and vimentin degradation were all seen in WFA treated specimens. In light of these findings, evaluation of WFA, its analogs, or other anti-vimentin therapeutic approaches in soft tissue sarcoma and ”epithelial to mesenchymal transition” clinical contexts is warranted.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 642.

Cardiomyocyte PDGFR-beta signaling is an essential component of the mouse cardiac response to load-induced stress

PDGFR is an important target for novel anticancer therapeutics because it is overexpressed in a wide variety of malignancies. Recently, however, several anticancer drugs that inhibit PDGFR signaling have been associated with clinical heart failure. Understanding this effect of PDGFR inhibitors has been difficult because the role of PDGFR signaling in the heart remains largely unexplored. As described herein, we have found that PDGFR-beta expression and activation increase dramatically in the hearts of mice exposed to load-induced cardiac stress. In mice in which Pdgfrb was knocked out in the heart in development or in adulthood, exposure to load-induced stress resulted in cardiac dysfunction and heart failure. Mechanistically, we showed that cardiomyocyte PDGFR-beta signaling plays a vital role in stress-induced cardiac angiogenesis. Specifically, we demonstrated that cardiomyocyte PDGFR-beta was an essential upstream regulator of the stress-induced paracrine angiogenic capacity (the angiogenic potential) of cardiomyocytes. These results demonstrate that cardiomyocyte PDGFR-beta is a regulator of the compensatory cardiac response to pressure overload-induced stress. Furthermore, our findings may provide insights into the mechanism of cardiotoxicity due to anticancer PDGFR inhibitors.

Generation of an immortalized astrocyte cell line from H-2Kb-tsA58 mice to study the role of astrocytes in brain metastasis

Astrocytes play a critical role in maintaining cerebral homeostasis and their dysregulation is thought to contribute to the pathogenesis of several diseases, including brain cancer and metastasis. Similar to the human disease, we found that lung and melanoma metastases in the mouse brain are accompanied by a reactive gliosis. To begin to study the biology of astrocytes and examine how these cells might contribute to metastasis formation and progression in the brain, we generated a conditionally immortal astrocyte cell line from H-2Kb-tsA58 mice. Astrocytes grown in culture expressed glial fibrillary acid protein (GFAP), glutamate receptor 1, and the N-methyl-D-aspartate (NMDA) receptor. Astrocytes also expressed the glial-specific transporters excitatory amino acid transporter 1 (EAAT1) and EAAT2. Astrocytes grown under permissive conditions (33 degrees C) expressed SV40 large T antigen and had a doubling time of 36 h, whereas expression of SV40 large T antigen was negligible in astrocytes grown at 37 degrees C for 72 h, which coincided with a plateau in cell division. In a co-culture assay with human lung adenocarcinoma cells (PC14-PE6), astrocytes activated programs in the tumor cells that signal for cell division and survival. Hence, the immortalized cell line will be useful for studying the role of astrocytes in disease processes in the brain, such as metastasis.

EphA2 immunoconjugate as molecularly targeted chemotherapy for ovarian carcinoma

BACKGROUND

EphA2 is overexpressed in many types of human cancer but is absent or expressed at low levels in normal epithelial tissues. We investigated whether a novel immunoconjugate containing an anti-EphA2 monoclonal antibody (1C1) linked to a chemotherapeutic agent (monomethyl auristatin phenylalanine [MMAF]) through a noncleavable linker maleimidocaproyl (mc) had antitumor activity against ovarian cancer cell lines and tumor models.

METHODS

Specificity of 1C1-mcMMAF was examined in EphA2-positive HeyA8 and EphA2-negative SKMel28 ovarian cancer cells by antibody binding and internalization assays. Controls were phosphate-buffered saline (PBS), 1C1, or control IgG-mcMMAF. Viability and apoptosis were investigated in ovarian cancer cell lines and tumor models (10 mice per group). Antitumor activities were tested in the HeyA8-luc and SKOV3ip1 orthotopic mouse models of ovarian cancer. Endothelial cells were identified by use of immunohistochemistry and anti-CD31 antibodies. All statistical tests were two-sided.

RESULTS

The 1C1-mcMMAF immunoconjugate specifically bound to EphA2-positive HeyA8 cells but not to EphA2-negative cells and was internalized by HeyA8 cells. Treatment with 1C1-mcMMAF decreased the viability of HeyA8-luc cells in an EphA2-specific manner. In orthotopic mouse models, treatment with 1C1-mcMMAF inhibited tumor growth by 85%-98% compared with that in control mice (eg, for weight of HeyA8 tumors, 1C1-mcMMAF = 0.05 g and control = 1.03 g; difference = 0.98 g, 95% confidence interval [CI] = 0.40 to 1.58 g; P = .001). Even in bulkier disease models with HeyA8-luc cells, 1C1-mcMMAF treatment, compared with control treatment, caused regression of established tumors and increased survival of the mice (eg, 1C1-mcMMAF vs control, mean = 60.6 days vs 29.4 days; difference = 31.2 days, 95% CI = 27.6 to 31.2 days; P = .001). The antitumor effects of 1C1-mcMMAF therapy, in SKOV3ip1 tumors, for example, were statistically significantly related to decreased proliferation (eg, 1C1-mcMMAF vs control, mean = 44.1% vs 55.8% proliferating cells; difference = 11.7%, 95% CI = 2.45% to 20.9%; P = .01) and increased apoptosis of tumor cells (eg, 1C1-mcMMAF vs control, mean = 8.6% vs 0.9% apoptotic cells; difference = 7.7%, 95% CI = 3.8% to 11.7%; P < .001) and of mouse endothelial cells (eg, 1C1-mcMMAF vs control, mean 2.8% vs 0.4% apoptotic endothelial cells; difference = 2.4%, 95% CI = 1.4% to 4.6%; P = .034).

CONCLUSION

The 1C1-mcMMAF immunoconjugate had antitumor activity in preclinical models of ovarian carcinoma.

Estrous cycle modulates ovarian carcinoma growth

PURPOSE

The effects of reproductive hormones on ovarian cancer growth are not well understood. Here, we examined the effects of estrous cycle variation and specific reproductive hormones on ovarian cancer growth.

EXPERIMENTAL DESIGN

We investigated the role of reproductive hormones in ovarian cancer growth using both in vivo and in vitro models of tumor growth.

RESULTS

In vivo experiments using the HeyA8 and SKOV3ip1 ovarian cancer models showed that tumor cell inoculation during proestrus significantly increased tumor burden (251-273%) compared with injection during the estrus phase. Treatment of ovariectomized mice with 17beta-estradiol resulted in a 404% to 483% increase in tumor growth compared with controls. Progestins had no significant effect, but did block estrogen-stimulated tumor growth. Tumors collected from mice sacrificed during proestrus showed increased levels of vascular endothelial growth factor (VEGF) and microvessel density compared with mice injected during estrus. HeyA8, SKOV3ip1, and mouse endothelial (MOEC) cells expressed estrogen receptor alpha and beta and progesterone receptor at the protein and mRNA levels, whereas 2774 ovarian cancer cells were estrogen receptor-negative. In vitro assays showed that 17beta-estradiol significantly increased ovarian cancer cell adhesion to collagen in estrogen receptor-positive, but not in estrogen receptor-negative cells. Additionally, 17beta-estradiol increased the migratory potential of MOEC cells, which was abrogated by the mitogen-activated protein kinase (MAPK) inhibitor, PD 09859. Treatment with 17beta-estradiol activated MAPK in MOEC cells, but not in HeyA8 or SKOV3ip1 cells.

CONCLUSION

Our data suggest that estrogen may promote in vivo ovarian cancer growth, both directly and indirectly, by making the tumor microenvironment more conducive for cancer growth.

Biobehavioral influences on matrix metalloproteinase expression in ovarian carcinoma

PURPOSE

Stromal cells in the tumor microenvironment, such as macrophages, play an active role in tumor growth and angiogenesis. However, little is known about relationships of biobehavioral factors with angiogenic cytokines and matrix metalloproteinases (MMP) produced by stromal cells. This study examined distress, MMPs, and angiogenic cytokines in ovarian cancer patients and in vitro.

EXPERIMENTAL DESIGN

Patients suspected of ovarian cancer completed preoperative questionnaires. At surgery, 56 were confirmed to have epithelial ovarian cancer. Tumor samples were analyzed for macrophage (CD68(+)) and tumor cell levels of MMP-2, MMP-9, and vascular endothelial growth factor. In vitro stimulation of isolated macrophage cells by the stress hormones norepinephrine and cortisol was done to assess effects on MMP-9.

RESULTS

Depressed patients showed significant elevations of MMP-9 in CD68(+) cells, adjusting for stage (P<0.0001). Patients with higher levels of current stress (P=0.01), life stress over the last 6 months (P=0.004), and general negative affect (P=0.007) also showed significantly greater MMP-9 in CD68(+) cells. In contrast, higher social support was associated with lower levels of MMP-9 (P=0.023) and vascular endothelial growth factor (P=0.036) in tumor cells. In vitro analyses showed that macrophage MMP-9 production could be directly enhanced (up to a 2-fold increase) by the stress hormones norepinephrine and cortisol.

CONCLUSIONS

Ovarian cancer patients with elevated depressive symptoms, chronic stress, and low social support showed elevations in MMP-9 in tumor-associated macrophages. Direct in vitro enhancement of stromal MMP-9 production by stress hormones was also shown. These findings may have implications for patient outcomes in ovarian cancer.

Targeted induction of lung endothelial cell apoptosis causes emphysema-like changes in the mouse

Pulmonary gas exchange relies on a rich capillary network, which, together with alveolar epithelial type I and II cells, form alveolar septa, the functional units in the lung. Alveolar capillary endothelial cells are critical in maintaining alveolar structure, because disruption of endothelial cell integrity underlies several lung diseases. Here we show that targeted ablation of lung capillary endothelial cells recapitulates the cellular events involved in cigarette smoke-induced emphysema, one of the most prevalent nonneoplastic lung diseases. Based on phage library screening on an immortalized lung endothelial cell line, we identified a lung endothelial cell-binding peptide, which preferentially homes to lung blood vessels. This peptide fused to a proapoptotic motif specifically induced programmed cell death of lung endothelial cells in vitro as well as targeted apoptosis of the lung microcirculation in vivo. As early as 4 days following peptide administration, mice developed air space enlargement associated with enhanced oxidative stress, influx of macrophages, and up-regulation of ceramide. Given that these are all critical elements of the corresponding human emphysema caused by cigarette smoke, these data provide evidence for a central role for the alveolar endothelial cells in the maintenance of lung structure and of endothelial cell apoptosis in the pathogenesis of emphysema-like changes. Thus, our data enable the generation of a convenient mouse model of human emphysema. Finally, combinatorial screenings on immortalized cells followed by in vivo targeting establishes an experimental framework for discovery and validation of additional ligand-directed pharmacodelivery systems.

Modification of the primary tumor microenvironment by transforming growth factor alpha-epidermal growth factor receptor signaling promotes metastasis in an orthotopic colon cancer model

The transforming growth factor alpha (TGFalpha)/epidermal growth factor receptor (EGFR) signaling pathway appears to play a critical role in colon cancer progression, but the cellular and molecular mechanisms that contribute to metastasis remain unknown. KM12C colon cancer cell clones expressing high (C9) or negligible (C10) levels of TGFalpha were implanted into the cecal walls of nude mice. C9 tumors formed autocrine and paracrine EGFR networks, whereas C10 tumors were unable to signal through EGFR. The tumor microenvironment of C9, but not C10, contained cells enriched in vascular endothelial growth factor (VEGF) A, interleukin-8, and matrix metalloproteinases-2 and -9 and had a high vascular surface area. C9 tumors recruited a macrophage population that co-expressed F4/80 and lymphatic vessel endothelial hyaluronic acid receptor and produced VEGFC. The mean lymphatic density of C9 tumors was threefold higher than that of C10 tumors. C9, but not C10, tumor cells metastasized to regional lymph nodes in all mice and to the liver in 5 of 10 mice. Forced expression of TGFalpha in C10 tumor cells led to the generation of autocrine and paracrine EGFR signaling, macrophage recruitment, enhanced blood and lymphatic vascular surface areas, and increased lymphatic metastasis. Collectively, these data show that activation of TGFalpha-EGFR signaling in colon cancer cells creates a microenvironment that is conducive for metastasis, providing a rationale for efforts to inhibit EGFR signaling in TGFalpha-positive colon cancers.

Impact of vessel maturation on antiangiogenic therapy in ovarian cancer

OBJECTIVE

The purpose of this study was to examine the functional and therapeutic significance of pericytes in ovarian cancer vasculature.

STUDY DESIGN

Tumor vessel morphologic condition and efficacy of endothelial and pericyte targeting were examined with the use of in vivo ovarian cancer models. The expression of platelet-derived growth factor (PDGF) ligands and receptors was examined in endothelial, pericyte-like, and ovarian cancer cells.

RESULTS

Relative to normal vessels, tumor vasculature was characterized by loosely attached pericytes in reduced density. PDGF-BB was expressed predominantly by the endothelial and cancer cells, whereas PDGFRbeta was present in pericyte-like cells. PDGF-BB significantly increased the migration of and VEGF production by pericyte-like cells; PDGFRbeta blockade abrogated these effects. Dual VEGF (VEGF-Trap) and PDGF-B (PDGF-Trap) targeted therapy was more effective in inhibiting in vivo tumor growth than either agent alone.

CONCLUSION

Aberrations in the tumor microenvironment contribute to endothelial cell survival. Strategies that target both endothelial cells and pericytes should be considered for clinical trials.

A selective small molecule inhibitor of c-Met, PHA-665752, reverses lung premalignancy induced by mutant K-ras

The c-Met receptor tyrosine kinase has been implicated in cellular transformation induced by mutant Ras, a commonly activated proto-oncogene in non-small cell lung cancer (NSCLC). However, the role of c-Met has not been defined in K-ras-mutant NSCLC, a disease for which no effective targeted therapeutic options currently exist. To acquire a greater understanding of its role, we used genetic and pharmacologic approaches to inhibit c-Met in mice and cultured cells. In Kras(LA1) mice, which develop premalignant lung lesions that progress to multifocal lung adenocarcinomas owing to somatic mutations in K-ras, c-Met was expressed in multiple cell types within premalignant lung lesions, and high concentrations of HGF were detected in bronchoalveolar lavage samples. Short-term treatment with PHA-665752, a c-Met inhibitor, decreased the numbers of premalignant lung lesions and induced apoptosis in tumor cells and vascular endothelial cells within lesions. In cell culture, PHA-665752 induced apoptosis of a lung adenocarcinoma cell line derived from Kras(LA1) mice (LKR-13) and a murine lung endothelial cell line (MEC). c-Met depletion by siRNA transfection induced apoptosis of MECs but not LKR-13 cells. Collectively, these findings suggest that apoptosis was an on-target effect of PHA-665752 in MECs but not in LKR-13 cells. We conclude that PHA-665752 inhibited lung tumorigenesis in Kras(LA1) mice and may provide a novel therapeutic approach to the prevention of K-ras-mutant NSCLC.

Effect of interleukin-8 gene silencing with liposome-encapsulated small interfering RNA on ovarian cancer cell growth

BACKGROUND

Interleukin-8 (IL-8) is a proangiogenic cytokine that is overexpressed in many human cancers. We investigated the clinical and biologic significance of IL-8 in ovarian carcinoma using human samples and orthotopic mouse models.

METHODS

Tumor expression of IL-8 was assessed by immunohistochemistry among ovarian cancer patients (n = 102) with available clinical and survival data. We examined the effect of IL-8 gene silencing with small interfering RNAs incorporated into neutral liposomes (siRNA-DOPCs), alone and in combination with docetaxel, on in vivo tumor growth, angiogenesis (microvessel density), and tumor cell proliferation in mice (n = 10 per treatment group) bearing orthotopic taxane-sensitive (HeyA8 and SKOV3ip1) and taxane-resistant (SKOV3ip2.TR) ovarian tumors. All statistical tests were two-sided.

RESULTS

Of the 102 cancer specimens, 43 (42%) had high IL-8 expression and 59 (58%) had low or no IL-8 expression; high IL-8 expression was associated with advanced tumor stage (P = .019), high tumor grade (P = .031), and worse survival (median survival for patients with high vs low IL-8 expression: 1.62 vs 3.79 years; P < .001). Compared with empty liposomes, IL-8 siRNA-DOPC reduced the mean tumor weight by 32% (95% confidence interval [CI] = 14% to 50%; P = .03) and 52% (95% CI = 27% to 78%; P = .03) in the HeyA8 and SKOV3ip1 mouse models, respectively. In all three mouse models, treatment with IL-8 siRNA-DOPC plus the taxane docetaxel reduced tumor growth the most compared with empty liposomes (77% to 98% reduction in tumor growth; P < .01 for all). In the HeyA8 and SKOV3ip1 models, tumors from mice treated with IL-8 siRNA-DOPC alone had lower microvessel density than tumors from mice treated with empty liposomes (HeyA8: 34% lower, 95% CI = 32% to 36% lower [P = .002]; SKOV3ip1: 39% lower, 95% CI = 34% to 44% lower [P = .007]). Compared with empty liposomes, IL-8 siRNA-DOPC plus docetaxel reduced tumor cell proliferation by 35% (95% CI = 25% to 44%; P < .001) and 38% (95% CI = 28% to 48%; P < .001) in the HeyA8 and SKOV3ip1 models, respectively.

CONCLUSIONS

Increased IL-8 expression is associated with poor clinical outcome in human ovarian carcinoma, and IL-8 gene silencing decreases tumor growth through antiangiogenic mechanisms.

Intratumoral heterogeneity for expression of tyrosine kinase growth factor receptors in human colon cancer surgical specimens and orthotopic tumors

The design of targeted therapy, particularly patient-specific targeted therapy, requires knowledge of the presence and intratumoral distribution of tyrosine kinase receptors. To determine whether the expression of such receptors is constant or varies between and within individual colon cancer neoplasms, we examined the pattern of expression of the ligands, epidermal growth factor, vascular endothelial growth factor, and platelet-derived growth factor-B as well as their respective receptors in human colon cancer surgical specimens and orthotopic human colon cancers growing in the cecal wall of nude mice. The expression of the epidermal growth factor receptor and the vascular endothelial growth factor receptor on tumor cells and stromal cells, including tumor-associated endothelial cells, was heterogeneous in surgical specimens and orthotopic tumors. In some tumors, the receptor was expressed on both tumor cells and stromal cells, and in other tumors the receptor was expressed only on tumor cells or only on stromal cells. In contrast, the platelet-derived growth factor receptor was expressed only on stromal cells in both surgical specimens and orthotopic tumors. Examination of receptor expression in both individual surgical specimens and orthotopic tumors revealed that the platelet-derived growth factor receptor was expressed only on stromal cells and that the patterns of epidermal growth factor receptor and vascular endothelial growth factor receptor 2 expression differed between tumor cells. This heterogeneity in receptor expression among different tumor cells suggests that targeting a single tyrosine kinase may not yield eradication of the disease.

Expression of epidermal growth factor (EGF)/transforming growth factor-alpha by human lung cancer cells determines their response to EGF receptor tyrosine kinase inhibition in the lungs of mice

Epidermal growth factor receptor (EGFR) has been extensively targeted in the treatment of non-small cell lung cancer, producing responses in a small number of patients. To study the role of ligand expression in mediating response to EGFR antagonism, we injected NCI-H441 [EGFR and EGF/transforming growth factor-alpha (TGF-alpha) positive] or PC14-PE6 (EGFR positive and EGF/TGF-alpha negative) human lung adenocarcinoma cells into the lungs of nude mice. We randomized the mice to receive treatment with the EGFR tyrosine kinase inhibitors gefitinib or AEE788 or vehicle. Treatment of mice bearing NCI-H441 but not PC14-PE6 lung tumors resulted in a significant reduction in primary tumor growth, pleural effusion, and lymph node metastasis. Immunohistochemical analyses revealed that NCI-H441 and PC14-PE6 cells expressed EGFR but that the expression of EGF/TGF-alpha was high in NCI-H441 cells and very low in PC14-PE6 cells. Consequently, EGFR was activated in both tumor and tumor-associated endothelial cells in the NCI-H441 tumors but not in the PC14-PE6 tumors. Antagonism of EGFR signaling by treatment of mice with AEE788 decreased proliferation and increased apoptosis of both tumor cells and tumor-associated endothelial cells in NCI-H441 tumors but not in PC14-PE6 tumors. However, after transfection of PC14-PE6 cells with TGF-alpha, lung tumors derived from the transfected cells expressed and activated EGFR in both tumor and tumor-associated endothelial cells and tumors responded to treatment with AEE788. Collectively, these results strongly suggest that the response of human lung cancers growing orthotopically in mice to the inhibition of EGFR signaling is determined by ligand (EGF/TGF-alpha) expression by tumor cells. Our findings provide an additional explanation for the susceptibility of lung cancers to treatment with EGFR tyrosine kinase inhibitors.

Inflammatory cytokines induce MAdCAM-1 in murine hepatic endothelial cells and mediate alpha-4 beta-7 integrin dependent lymphocyte endothelial adhesion in vitro

Background

MAdCAM-1 plays a central role in T-lymphocyte homing to the gut, but its role in chronic liver inflammation remains unknown. Therefore, this study measured MAdCAM-1 expression, regulation, and function in cultured murine hepatic endothelial cells.

Methods

Cultures of hepatic endothelial cells (HEC) were prepared from mice expressing a temperature-sensitive SV40 large T antigen (H-2K^b-tsA58) under the control of an IFN-γ promoter. Time and dose dependent expression of MAdCAM-1 in response to TNF-α, IL-1β and IFN-γ was studied by immunoblotting. Lymphocyte adhesion was studied using α₄β₇integrin expressing lymphocytes (TK-1) +/- anti-MAdCAM-1 mAb.

Results

TNF-α induced MAdCAM-1 dose-and time-dependently with maximum expression at 20 ng/ml and at 48 hours. IL-1β also induced MAdCAM-1 to a lesser extent compared to TNF-α; IFN-γ did not induce MAdCAM-1. TNF-α significantly increased lymphocyte-endothelial adhesion (P < 0.01), which was reversed by anti-MAdCAM-1 antibody. MAdCAM-1 expression was also reduced by N-acetylcysteine and by two NO donors (SperNO, DETANO) suggesting that hepatic endothelial MAdCAM-1 is oxidant and NO regulated.

Conclusion

MAdCAM-1 is a major determinant of leukocyte recruitment in chronic inflammation and is expressed by HEC in response to IL-1β and TNF-α. This system may provide a useful model for studying inflammatory mechanisms in liver disease and help determine if controlled MAdCAM-1 expression might influence inflammation in liver disease.

The role of the organ microenvironment in the biology and therapy of cancer metastasis

By the time of diagnosis, primary neoplasms are biologically heterogeneous and contain subpopulations of cells with different metastatic potentials. The pathogenesis of a metastasis consists of many sequential steps that must be completed to produce clinically relevant lesions. During any of these steps, tumor cells interact with host factors in the microenvironment that the tumor cells can usurp. Treatment of metastasis can be directed against tumor cells and/or microenvironmental factors that support tumor growth, such as tumor-associated blood vessels.

A homeobox gene related to Drosophila distal-less promotes ovarian tumorigenicity by inducing expression of vascular endothelial growth factor and fibroblast growth factor-2

Homeobox genes control developmental patterning and are increasingly being found to be deregulated in tumors. The DLX4 homeobox gene maps to the 17q21.3-q22 region that is amplified in some epithelial ovarian cancers. Because amplification of this region correlates with poor prognosis, we investigated whether DLX4 overexpression contributes to aggressive behavior of this disease. DLX4 was not detected in normal ovary and cystadenomas, whereas its expression in ovarian carcinomas was strongly associated with high tumor grade and advanced disease stage. Overexpression of DLX4 in ovarian cancer cells promoted growth in low serum and colony formation. Imaging of mice bearing intraperitoneal tumors revealed that DLX4 overexpression substantially increased tumor burden. Tumors that overexpressed DLX4 were more vascularized than vector-control tumors. Conditioned medium of DLX4-overexpressing tumor cells was more effective than medium conditioned by vector-control cells in stimulating endothelial cell growth. These observations were associated with the ability of DLX4 to induce expression of vascular endothelial growth factor as well as intracellular and secreted isoforms of fibroblast growth factor-2. Moreover, increased levels of these fibroblast growth factor-2 isoforms induced vascular endothelial growth factor expression in tumor cells. This study reveals a novel role for a homeobox gene in ovarian tumorigenicity by its induction of a proangiogenic, growth-stimulatory molecular program.

Tumor cell-organ microenvironment interactions in the pathogenesis of cancer metastasis

The process of cancer metastasis is sequential and selective and contains stochastic elements. The growth of metastases represents the endpoint of many lethal events that few tumor cells can survive. Primary tumors consist of multiple subpopulations of cells with heterogeneous metastatic properties, and the outcome of metastasis depends on the interplay of tumor cells with various host factors. The findings that different metastases can originate from different progenitor cells account for the biological diversity that exists among various metastases. Even within a solitary metastasis of proven clonal origin, however, heterogeneity of biological characteristics can develop rapidly. The pathogenesis of metastasis depends on multiple interactions of metastatic cells with favorable host homeostatic mechanisms. Interruption of one or more of these interactions can lead to the inhibition or eradication of cancer metastasis. For many years, all of our efforts to treat cancer have concentrated on the inhibition or destruction of tumor cells. Strategies both to treat tumor cells (such as chemotherapy and immunotherapy) and to modulate the host microenvironment (including the tumor vasculature) should offer additional approaches for cancer treatment. The recent advances in our understanding of the biological basis of cancer metastasis present unprecedented possibilities for translating basic research to the clinical reality of cancer treatment.

Targeting receptor tyrosine kinase on lymphatic endothelial cells for the therapy of colon cancer lymph node metastasis

Oral treatment with the dual-receptor tyrosine kinase inhibitor AEE788 effectively reduces the number of peritumoral lymphatic vessels and the incidence of lymph node metastasis in nude mice with human HT29 colon cancer cells growing in the cecum. Whether inhibition of lymph node metastasis in colon cancer can be achieved by directly targeting lymphatic endothelial cells remains unclear. Using a microsurgical approach, we generated conditionally immortalized lymphatic endothelial cell lines from the H-2K(b)-tsA58 mouse mesentery and characterized these cells for the expression of lymphatic endothelial cell markers. Lymphatic endothelial cells were stimulated in culture with an array of tumor cell-produced cytokines, leading to the identification of redundant pathways for proliferation and survival. Treatment with AEE788 decreased the migration, proliferation, and survival of lymphatic endothelial cells, demonstrating that oral treatment with AEE788 effectively decreases the incidence of colon cancer lymphatic metastasis due, in part, to the direct inhibition of lymphatic endothelial cell signaling.

High expression of ligands for chemokine receptor CXCR2 in alveolar epithelial neoplasia induced by oncogenic kras

CXCL8, a ligand for the chemokine receptor CXCR2, was recently reported to be a transcriptional target of Ras signaling, but its role in Ras-induced tumorigenesis has not been fully defined. Here, we investigated the role of KC and MIP-2, the murine homologues of CXCL8, in Kras(LA1) mice, which develop lung adenocarcinoma owing to somatic activation of the KRAS oncogene. We first investigated biological evidence of CXCR2 ligands in Kras(LA1) mice. Malignant progression of normal alveolar epithelial cells to adenocarcinoma in Kras(LA1) mice was associated with enhanced intralesional vascularity and neutrophilic inflammation, which are hallmarks of chemoattraction by CXCR2 ligands. In in vitro migration assays, supernatants of bronchoalveolar lavage samples from Kras(LA1) mice chemoattracted murine endothelial cells, alveolar inflammatory cells, and the LKR-13 lung adenocarcinoma cell line derived from Kras(LA1) mice, an effect that was abrogated by pretreatment of the cells with a CXCR2-neutralizing antibody. CXCR2 and its ligands were highly expressed in LKR-13 cells and premalignant alveolar lesions in Kras(LA1) mice. Treatment of Kras(LA1) mice with a CXCR2-neutralizing antibody inhibited the progression of premalignant alveolar lesions and induced apoptosis of vascular endothelial cells within alveolar lesions. Whereas the proliferation of LKR-13 cells in vitro was resistant to treatment with the antibody, LKR-13 cells established as syngeneic tumors were sensitive, supporting a role for the tumor microenvironment in the activity of CXCR2. Thus, high expression of CXCR2 ligands may contribute to the expansion of early alveolar neoplastic lesions induced by oncogenic KRAS.

Construction of a novel constitutively active chimeric EGFR to identify new targets for therapy

Tumor cells and tumor-associated endothelial cells express activated epidermal growth factor receptor (EGFR) due to production of EGF-related ligands in the tumor microenvironment. To investigate the effect of perpetual EGFR activation on endothelial cells, we developed a novel method to generate constitutively active EGFR. We fused the entire intracellular domain of the EGFR to the N-terminus of the CD3zeta component of the T-cell receptor signaling complex. Expression of the chimeric receptor CD3-EGFR in EGFR-deficient human embryonic kidney cells resulted in ligand-independent sustained EGFR phosphorylation and in the induction of Akt, mitogen-activated protein kinase, and signal transducer and activator of transcription 3 (Stat3). Next, CD3-EGFR was stably expressed in murine brain endothelial cells where it signaled for the initiation of angiogenic programs, Stat3 activation, and continuous proliferation. A comparison between brain endothelial cells encoding CD3zeta and CD3-EGFR revealed that proangiogenic phenotype was modulated by the intracellular effector Stat3 and that suppression of this downstream target with the EGFR tyrosine kinase inhibitor PKI166 could revert this phenotype. Thus, our results validate the use of chimeric constitutively active receptors to replicate critical features observed in pathophysiological processes that can expedite the identification of novel therapeutic agents targeting EGFR activation and function.

Interleukin-6, secreted by human ovarian carcinoma cells, is a potent proangiogenic cytokine

Angiogenesis, a key rate-limiting step in the growth and dissemination of malignant tumors, is regulated by the balance between positive and negative effectors. Recent studies indicate that the pleiotropic cytokine interleukin-6 (IL-6) may contribute to the vascularization of some tumors by disrupting the equilibrium between positive and negative angiogenic regulatory molecules. We determined whether IL-6 participates in the angiogenesis observed during the progression of ovarian carcinoma. We measured IL-6 production by human ovarian cancer cell lines in vitro and in vivo. Not all cell lines secreted IL-6 in vitro; however, when the cell lines were implanted into the peritoneal cavity of female nude mice, every line secreted IL-6. Most human ovarian carcinoma cell lines tested secreted significant levels of the soluble IL-6 receptor (sIL-6R). Endothelial cell lines established from the ovary and mesentery of female H-2K(b)-tsA58 mice were tested for response to IL-6. Both endothelial cell lines expressed the IL-6R and their stimulation with the exogenous ligand significantly enhanced cell migration and activated the downstream signaling molecule signal transducers and activators of transcription 3. Dual immunohistochemical staining for IL-6R and CD31 revealed IL-6R expression on human endothelial cells within normal ovary and carcinoma specimens. Gelfoam sponges containing 0.4% agarose and IL-6 or basic fibroblast growth factor and implanted into the subcutis of BALB/c mice were vascularized to the same extent. Collectively, the data indicate that ovarian tumor cells secreted IL-6, a highly angiogenic cytokine that supports progression of disease.

Association of alphavbeta3 integrin expression with the metastatic potential and migratory and chemotactic ability of human osteosarcoma cells

INTRODUCTION

Expression of adhesion molecules such as alphavbeta3 integrin has been associated with the metastatic potential of tumor cells. The purpose of this study was to determine whether alphavbeta3 expression correlated with the metastatic potential of human osteosarcoma cells.

MATERIALS AND METHODS

We developed a series of sublines (LM2-LM7) from human osteosarcoma SAOS parental cells, with progressively increasing potential to form lung metastases in nude mice after intravenous injection. SAOS parental and LM2 cells were poorly metastatic, but LM7 cells resulted in visible metastatic lung nodules by 6-8 weeks. We quantified alphavbeta3 integrin expression using flow cytometry.

RESULTS

alphavbeta3 expression correlated with the metastatic potential of the cells, with LM7 cells showing the highest expression. LM7 cell adhesion to vitronectin decreased after treatment with echistatin, a RGD-containing peptide antagonist of alphavbeta3. LM7 cells demonstrated higher chemotactic activity than SAOS cells to a homogenate made from lung tissue. This chemotactic activity was also inhibited by echistatin. These data indicated that alphavbeta3 was critical for the migration of LM7 cells to the lung homogenate. Chemotaxis to a liver homogenate was the same for LM7 and SAOS cells. Migration of LM7 cells through lung endothelial cells was higher than that through liver endothelial cells, and echistatin again inhibited this migration.

CONCLUSIONS

alphavbeta3 integrin expression may play a role in the metastatic potential of osteosarcoma cells by enhancing the ability of the cells to migrate specifically to the lung. Alphavbeta3 integrin may therefore be a potential new target for osteosarcoma.

Modulation of bone microenvironment with zoledronate enhances the therapeutic effects of STI571 and paclitaxel against experimental bone metastasis of human prostate cancer

Prostate cancer cells metastasize to the bone where their interaction with osteoclasts and osteoblasts can lead to alterations in the structure of the bone. We determined whether the systemic administration of the bisphosphonate, zoledronate, could prevent bone lysis and halt the proliferation of human prostate cancer cells injected into the tibia of nude mice. Zoledronate did not affect the in vitro proliferation of human prostate cancer PC-3MM2 cells. The in vivo administration of zoledronate produced significant bone preservation but did not inhibit the progressive growth of PC-3MM2 cells. The systemic administration of STI571 (imatinib mesylate, Gleevec), an inhibitor of phosphorylation of the platelet-derived growth factor receptor, in combination with paclitaxel, produced apoptosis of tumor cells and bone- and tumor-associated endothelial cells. The systemic administration of zoledronate with STI571 and paclitaxel produced a significant preservation of bone structure, a decrease in tumor incidence and weight, and a decrease in incidence of lymph node metastasis. This therapeutic activity was correlated with inhibition of osteoclast function, inhibition of tumor cell proliferation, and induction of apoptosis in tumor-associated endothelial cells and tumor cells. Cancer is a heterogeneous disease that requires multimodality therapy. The present data recommend the combination of a bisphosphonate agent with protein tyrosine kinase inhibitor and an anticycling drug for the treatment of prostate cancer bone metastasis.

Development of an orthotopic model to study the biology and therapy of primary human lung cancer in nude mice

PURPOSE

This study was conducted to develop biologically relevant animal models of human lung cancer that are reproducible, inexpensive, and easy to perform.

EXPERIMENTAL DESIGN

Human lung adenocarcinoma (PC14PE6), bronchioloalveolar carcinoma (NCI-H358), squamous cell carcinoma (NCI-H226), poorly differentiated non-small cell lung cancer (NCI-H1299 and A549), or small cell lung cancer (NCI-H69) cells in Matrigel were injected percutaneously into the left lungs of nude mice. The growth pattern of the different lung cancer tumors was studied. For PC14PE6 and NCI-H358, the growth pattern in the subcutis and the response to paclitaxel were also studied.

RESULTS

As is observed for human primary lung cancer, tumors formed from a single focus of disease and progressed to a widespread and fatal thoracic process characterized by diffuse dissemination of lung cancer in both lungs and metastasis to intra- and extrathoracic lymph nodes. When the lung cancer cell lines were implanted s.c., systemic therapy with paclitaxel induced tumor regression. However, only a limited therapeutic response to paclitaxel was observed when the same cells were implanted orthotopically into the lung. Immunohistochemical analysis of tumor tissue revealed increased expression of the proangiogenic factors interleukin 8, basic fibroblast growth factor, and vascular endothelial growth factor/vascular permeability factor.

CONCLUSIONS

Our orthotopic models of human lung cancer confirm the "seed and soil" concept and likely provide more clinically relevant systems for the study of both non-small cell lung cancer and small cell lung cancer biology, and for characterizing novel therapeutic strategies.