Vascular endothelial growth factor receptor-1 contributes to resistance to anti-epidermal growth factor receptor drugs in human cancer cells

PURPOSE: The resistance to selective EGFR inhibitors involves the activation of alternative signaling pathways, and Akt activation and VEGF induction have been described in EGFR inhibitor-resistant tumors. Combined inhibition of EGFR and other signaling proteins has become a successful therapeutic approach, stimulating the search for further determinants of resistance as basis for novel therapeutic strategies. EXPERIMENTAL DESIGN: We established human cancer cell lines with various degrees of EGFR expression and sensitivity to EGFR inhibitors and analyzed signal transducers under the control of EGFR-dependent and EGFR-independent pathways. RESULTS: Multitargeted inhibitor vandetanib (ZD6474) inhibited the growth and the phosphorylation of Akt and its effector p70S6 kinase in both wild-type and EGFR inhibitor-resistant human colon, prostate, and breast cancer cells. We found that the resistant cell lines exhibit, as common feature, VEGFR-1/Flt-1 overexpression, increased secretion of VEGF and placental growth factor, and augmented migration capabilities and that vandetanib is able to antagonize them. Accordingly, a new kinase assay revealed that in addition to VEGF receptor (VEGFR)-2, RET, and EGFR, vandetanib efficiently inhibits also VEGFR-1. The contribution of VEGFR-1 to the resistant phenotype was further supported by the demonstration that VEGFR-1 silencing in resistant cells restored sensitivity to anti-EGFR drugs and impaired migration capabilities, whereas exogenous VEGFR-1 overexpression in wild-type cells conferred resistance to these agents. CONCLUSIONS: This study shows that VEGFR-1 contributes to anti-EGFR drug resistance in different human cancer cells. Moreover, vandetanib inhibits VEGFR-1 activation, cell proliferation, and migration, suggesting its potential utility in patients resistant to EGFR inhibitors.     

Potential role for vascular endothelial growth factor‐D as an autocrine factor for human gastric carcinoma cells

Vascular endothelial growth factor (VEGF)‐D induces lymphangiogenesis by activating VEGF receptor (VEGFR)‐3, which is expressed mainly by lymphatic endothelial cells. VEGFR‐3 has also been detected in several types of malignant cells, but the significance of VEGFR‐3 expression by malignant cells remains unclear. We examined the expression and function of VEGF‐D/VEGFR‐3 in human gastric carcinoma cells. Expression of VEGF‐D and VEGFR‐3 was analyzed in three human gastric carcinoma cell lines and 29 surgical specimens. cDNA microarray analysis was used to examine the effect of VEGF‐D on the expression of genes associated with disease progression in VEGFR‐3‐expressing KKLS cells. VEGF‐D‐transfected cells and control cells were transplanted into the gastric wall of nude mice. In 10 of the 29 (34%) gastric carcinoma specimens and two of the three cell lines, cancer cells expressed both VEGF‐D and VEGFR‐3. In vitro treatment of KKLS cells with exogenous VEGF‐D increased expression of cyclin D1 and Bcl‐2 and stimulated cell proliferation. VEGF‐D transfection into KKLS cells resulted in stimulation of angiogenesis, lymphangiogenesis, and cell proliferation, and in inhibition of apoptosis. VEGF‐D may participate in the progression of human gastric carcinoma by acting via autocrine and paracrine mechanisms. (Cancer Sci 2010)     

Relationship between VEGF, EGF and invasion, metastasis of gastric cancer cells

Objective: To investigate the relationship between expression of vascular endothelial growth factor (VEGF), epidermal growth factor (EGF) and the biological properties of gastric cancer cells such as invasion and metastasis.Methods: RT-PCR was performed to semi-quantitatively detect the mRNA expressions of EGF, EGFR, VEGF and VEGFR in four kinds of gastric cancer cell lines BGC823, MGC803, HGC27 and SGC7901, which were classified by their differentiation degree in our experiment. We obtained cell line growth curves from MTT assays. The migration of gastric cancer cells was observed under inverted phase contrast microscope. The changes of invasion and adhesion were detected by a Transwell assay.Results: The growth rates slowed down sequentially in MGC803, HGC27, BGC823 and SGC7901(P＜0.05). The ability of migration, invasion and adhesion were reduced sequentially, and the difference was significant. The expressions of EGF, EGFR, VEGF and VEGFR were significantly stronger in MGC803 and HGC27 than in BGC823 and SGC7901 cells, and the difference was statistically significant(P＜0.05).Conclusion: The expressions of VEGF and EGF had close relationship with the properties of migration, adhesion and invasion of gastric cancer cells in vitro. Thus, targeting VEGF and EGF may be a potential therapeutic strategy for inhibiting peritoneal metastasis of gastric cancer.     

Vandetanib inhibits both VEGFR-2 and EGFR signalling at clinically relevant drug levels in preclinical models of human cancer

Vandetanib is a multi-targeted receptor tyrosine kinase inhibitor that is in clinical development for the treatment of solid tumours. This preclinical study examined the inhibition of two key signalling pathways (VEGFR-2, EGFR) at drug concentrations similar to those achieved in the clinic, and their contribution to direct and indirect antitumour effects of vandetanib. For in vitro studies, receptor phosphorylation was assessed by Western blotting and ELISA, cell proliferation was assessed using a cell viability endpoint, and effects on cell cycle determined using flow cytometry. For in vivo studies, Western blotting, ELISA and immunohistochemistry (IHC) were used to assess receptor phosphorylation. Cell culture experiments demonstrated that anti-proliferative effects of vandetanib resulted from inhibition of either EGFR or VEGFR-2 signalling in endothelial cells, but were associated with inhibition of EGFR signalling in tumour cells. Vandetanib inhibited both EGFR and VEGFR-2 signalling in normal lung tissue and in tumour xenografts. In a lung cancer model expressing an activating EGFR mutation, the activity of vandetanib was similar to that of a highly selective EGFR inhibitor (gefitinib), and markedly greater than that of a highly selective VEGFR inhibitor (vatalanib). These data suggest that at the plasma exposures achieved in the clinic, vandetanib will significantly inhibit both VEGFR-2 and EGFR signalling, and that both inhibition of angiogenesis and direct inhibition of tumour cell growth can contribute to treatment response.     

Administration of VEGF receptor tyrosine kinase inhibitor increases VEGF production causing angiogenesis in human small-cell lung cancer xenografts

Angiogenesis is mediated mainly by vascular endothelial growth factor (VEGF), and VEGF causes rapid growth in cancers, including human small-cell lung cancer (SCLC). The anti-angiogenic strategy of treating cancer using VEGF receptor (VEGFR) inhibition is currently of great interest. We tested the effects of the VEGFR2 tyrosine kinase inhibitor (TKI) vandetanib on the proliferation of two kinds of SCLC cell lines: SBC-1 cells, with detectable VEGFR2 expression and MS-1-L cells, without detectable VEGFR2 expression. To evaluate the anti-tumor and anti-angiogenic effects of vandetanib in vivo, we grafted SBC-1 and MS-1-L cells into mice. After a 3-week treatment, we measured the tumor size and histologically evaluated necrosis and apoptosis using H&E and TUNEL staining, respectively. The microvessels in the xenografts were also quantified by immunostaining of CD31. Vandetanib did not affect the proliferation of SBC-1 cells, but stimulated the growth of MS-1-L cells. In the SCLC xenograft model, vandetanib inhibited growth and tumor angiogenesis in a dose-dependent manner in SBC-1 xenografts. Vandetanib inhibited the growth of MS-1-L xenografts at a low dose (<12.5 mg/kg/day), but it did not affect tumor size or change microvessel counts at a higher dose. Interestingly, secretion of VEGF increased significantly in the MS-1-L cell line in the presence of a high dose of vandetanib in vitro. The effects of vandetanib on tumor angiogenesis were different in SBC-1 and MS-1-L cell lines. Production of angiogenic factors such as VEGF by the tumor potentially stimulates tumor angiogenesis and results in the acquisition of resistance to VEGFR TKI.     

Co-expression of receptor tyrosine kinases in esophageal adenocarcinoma and squamous cell cancer

This study aimed to define the co-expression pattern of target receptor tyrosine kinases (RTKs) in human esophageal adenocarcinoma and squamous cell cancer. The co-expression pattern of vascular endothelial growth factor receptor (VEGFR)1-3, platelet-derived growth factor receptor (PDGFR)alpha/beta and epidermal growth factor receptor 1 (EGFR1) was analyzed by RT-PCR in 50 human esophageal cancers (35 adenocarcinomas and 15 squamous cell cancers). In addition, IHC staining was applied for the confirmation of the expression and analysis of RTK localisation. The adenocarcinoma samples revealed VEGFR1 (97%), VEGFR2 (94%), VEGFR3 (77%), PDGFRalpha (91%), PDGFRbeta (85%) and EGFR1 (97%) expression at different intensities. Ninety-four percent of the esophageal adenocarcinomas expressed at least four out of six RTKs. Similarly, squamous cell cancers revealed VEGFR1 (100%), VEGFR2 (100%), VEGFR3 (53%), PDGFRalpha (100%), PDGFRbeta (87%) and EGFR1 (100%) expression at different intensities. All esophageal squamous cell carcinomas expressed at least four out of six RTKs. While VEGFR1-3 and PDGFRalpha and EGFR1 was expressed by tumor cells, PDGFRbeta was restricted to stromal cells, which also depicted a PDGFRalpha expression. Our results revealed a high rate of RTK co-expression in esophageal adenocarcinoma and squamous cell cancer and may encourage application of multi-target RTK inhibitors within a multimodal concept as a promising novel approach for innovative treatment strategies.     

Anti‐angiogenic therapies for gastric cancer

Tumor angiogenesis plays an important role in cancer cell proliferation and metastasis. In gastric cancer, among the numerous clinical trials investigating various anti‐angiogenic therapies, such as antivascular endothelial growth factor (VEGF) or anti‐VEGF receptor (VEGFR)‐2 monoclonal antibodies, VEGF‐Trap and VEGFR tyrosine kinase inhibitors, the anti‐VEGFR‐2 antibody ramucirumab was shown to prolong overall survival not only as a single agent but also in combination with paclitaxel as a second‐line chemotherapy. Additionally, apatinib, a selective VEGFR‐2 tyrosine kinase inhibitor, prolonged survival as a third‐line or later treatment option in patients with advanced gastric cancer. Preliminary results of studies investigating ramucirumab plus immune checkpoint inhibitors in gastric cancer were encouraging, and further investigations are ongoing. In China, apatinib in combination with cytotoxic agents is being investigated for systemic chemotherapy or maintenance therapy as an earlier treatment option. The clinical activity in gastric cancer of the multikinase inhibitor regorafenib was suggested in a randomized phase II study. A global phase III trial comparing regorafenib with placebo is currently ongoing. Further studies of anti‐angiogenic therapy combined with not only chemotherapy but also immune checkpoint inhibitors are also being pursued, providing hope for improved survival in patients with gastric cancer.     

Dual inhibition of epidermal growth factor receptor and vascular endothelial growth factor receptor phosphorylation by AEE788 reduces growth and metastasis of human colon carcinoma in an orthotopic nude mouse model

We studied growth factors and their receptors in tumor cells and tumor-associated endothelial cells as the therapeutic targets in colon cancer. Immunohistochemical analysis of 13 surgical specimens of human colon adenocarcinoma revealed that both tumor cells and tumor-associated endothelial cells in 11 of the 13 specimens expressed the epidermal growth factor (EGF), transforming growth factor alpha (TGF-alpha), EGF receptor (EGFR), phosphorylated EGFR (pEGFR), vascular endothelial growth factor (VEGF), VEGF receptor (VEGFR), and phosphorylated VEGFR (pVEGFR). HT29 human colon cancer cells growing orthotopically in the cecum of nude mice expressed a high level of EGF, EGFR, pEGFR, VEGF, VEGFR, and pVEGFR. Double-immunofluorescence staining found that tumor-associated mouse endothelial cells also expressed pEGFR and pVEGFR. Tumors in mice treated for 5 weeks with oral AEE788 (an inhibitor of EGFR and VEGFR tyrosine kinase) as a single agent or with CPT-11 alone were smaller (>50%) than those in control mice. Mice treated with the combination of AEE788 and CPT-11 had significantly smaller tumors (P < 0.01) and complete inhibition of lymph node metastasis. AEE788 alone or in combination with CPT-11 inhibited pEGFR, pVEGFR, and phosphorylated Akt expression on tumor-associated endothelial cells as well as on tumor cells. The combination therapy also significantly decreased microvessel density and tumor cell proliferation and increased the level of apoptosis in both tumor cells and tumor-associated endothelial cells. Collectively, these data suggest that the dual inhibition of EGFR and VEGFR signaling pathways in tumor cells and tumor-associated endothelial cells in combination with chemotherapy can provide a new approach to the treatment of colon cancer.     

HB‐EGF orchestrates the complex signals involved in triple‐negative and trastuzumab‐resistant breast cancer

A number of therapeutic strategies targeting epidermal growth factor receptor (EGFR) have not always led to success in the present state of breast cancer therapy. Notably, there is currently no way to treat trastuzumab‐resistant and triple‐negative breast cancer (TNBC). Here, we found that heparin‐binding epidermal growth factor‐like growth factor (HB‐EGF), a member of the EGFR ligands, was predominantly expressed in breast cancer and that treatment with crossreacting material 197 (CRM197), a specific inhibitor of HB‐EGF, blocked ERK as well as AKT activation via complexes of EGFR and unknown growth factor receptors in TNBC or through complexes of EGFR and human epidermal growth factor receptor‐2 in trastuzumab‐resistant breast cancer, caused significant cell apoptosis and inhibited tumor growth. Accordingly, we can provide a novel concept that a certain EGFR ligand is recognized as a rational target against breast cancer. In addition, it is plausible that CRM197 could be an effective anticancer agent for molecularly targeted therapies.     

Tumor cell and endothelial cell therapy of oral cancer by dual tyrosine kinase receptor blockade

Expression of the epidermal growth factor (EGF) and activation of its receptor (EGFR), a tyrosine kinase, are associated with progressive growth of head and neck cancer. Expression of the vascular endothelial growth factor (VEGF) is associated with angiogenesis and progressive growth of tumor. The tyrosine kinase inhibitor NVP-AEE788 (AEE788) blocks the EGF and VEGF signaling pathways. We examined the effects of AEE788 administered alone, or with paclitaxel (Taxol), on the progression of human head and neck cancer implanted orthotopically into nude mice. Cells of two different human oral cancer lines, JMAR and MDA1986, were injected into the tongues of nude mice. Mice with established tumors were randomized to receive three times per week oral AEE788, once weekly injected paclitaxel, AEE788 plus paclitaxel, or placebo. Oral tumors were resected at necropsy. Kinase activity, cell proliferation, apoptosis, and mean vessel density were determined by immunohistochemical immunofluorescent staining. AEE788 inhibited cell growth, induced apoptosis, and reduced the phosphorylation of EGFR, VEGFR-2, AKT, and mitogen-activated protein kinase in both cell lines. Mice treated with AEE788 and AEE788 plus paclitaxel had decreased microvessel density, decreased proliferative index, and increased apoptosis. Hence, AEE788 inhibited tumor vascularization and growth and prolonged survival. Inhibition of EGFR and VEGFR phosphorylation by AEE788 effectively inhibits cellular proliferation of squamous cell carcinoma of the head and neck, induces apoptosis of tumor endothelial cells and tumor cells, and is well tolerated in mice. These data recommend the consideration of patients with head and neck cancer for inclusion in clinical trials of AEE788.     

Responses of human colorectal tumor cells to treatment with the anti-epidermal growth factor receptor monoclonal antibody ICR62 used alone and in combination with the EGFR tyrosine kinase inhibitor gefitinib

The anti-epidermal growth factor receptor (EGFR) monoclonal antibody cetuximab has been approved for the treatment of patients with metastatic colorectal cancer. However, there is currently no reliable marker for response to therapy with the EGFR inhibitors. In this study, we investigated the sensitivity of 10 human colorectal tumor cell lines (DiFi, CCL218, CCL221, CCL225, CCL227, CCL228, CCL231, CCL235, CCL244, and HCT-116) to treatment with our anti-EGFR monoclonal antibody, ICR62, and/or the EGFR tyrosine kinase inhibitor, gefitinib. Of the cells examined, only DiFi contained high levels of constitutively active EGFR and were highly sensitive to treatment with both ICR62 (IC(50) = 0.52 nmol/L) and gefitinib (IC(50) = 27.5 nmol/L). In contrast, the growth of other tumor cell lines, which contained low levels of the EGFR, HER-2, and pAkt but comparable or even higher basal levels of phosphorylated mitogen-activated protein kinase (pMAPK), were relatively resistant to treatment with both inhibitors. Both ICR62 and gefitinib induced EGFR down-regulation, reduced the basal levels of pEGFR at five known tyrosine residues, pMAPK, and pAkt, and increased the sub-G(1) population in DiFi cells. However, treatment with a combination of ICR62 and gefitinib neither sensitized colorectal tumor cells that were insensitive to treatment with the single agent nor enhanced the growth-inhibitory effect of the single agent in DiFi cells. These results indicate that basal levels of pMAPK and pAkt are not good indicators of response to the EGFR inhibitors in colorectal cancer cells and dual targeting of the EGFR by a combination of ICR62 and gefitinib is not superior to treatment with a single agent.     

RAC1 inhibition as a therapeutic target for gefitinib‐resistant non‐small‐cell lung cancer

Although epidermal growth factor receptor (EGFR)‐tyrosine kinase inhibitors (EGFR‐TKI), including gefitinib, provide a significant clinical benefit in non‐small‐cell lung cancer (NSCLC) patients, the acquisition of drug resistance has been known to limit the efficacy of EGFR‐TKI therapy. In this study, we demonstrated the involvement of EGF‐EGFR signaling in NSCLC cell migration and the requirement of RAC1 in EGFR‐mediated progression of NSCLC. We showed the significant role of RAC1 pathway in the cell migration or lamellipodia formation by using gene silencing of RAC1 or induction of constitutive active RAC1 in EGFR‐mutant NSCLC cells. Importantly, the RAC1 inhibition suppressed EGFR‐mutant NSCLC cell migration and growth in vitro, and growth in vivo even in the gefitinib‐resistant cells. In addition, these suppressions by RAC1 inhibition were mediated through MEK or PI3K independent mechanisms. Collectively, these results open up a new opportunity to control the cancer progression by targeting the RAC1 pathway to overcome the resistance to EGFR‐TKI in NSCLC patients.     

Risk of venous thromboembolic events associated with VEGFR‐TKIs: A systematic review and meta‐analysis

Vascular endothelial growth factor receptor (VEGFR) tyrosine kinase inhibitors (TKIs) have been widely used in advanced cancers. Concerns have arisen regarding the risk of venous thromboembolism with the use of these drugs. Currently, the contribution of VEGFR‐TKIs to venous thromboembolism is still unknown. We performed a meta‐analysis to determine the incidence and relative risk (RR) of venous thromboembolism events (VTEs) associated with these agents. Eligible studies included phase II and III prospective trials evaluating US Food and Drug Administration approved VEGFR‐TKIs (pazopanib, sunitinib, sorafenib and vandetanib), and data on VTEs were available. Overall incidence rates, RR and 95% confidence intervals (CI) were calculated employing fixed‐ or random‐effects models depending on the heterogeneity of included trials. A total of 14 studies (4,430 patients) were selected for this meta‐analysis. The incidence of VTEs related to VEGFR‐TKIs was 3% (95%CI: 1.7–5.1%), and there was no statistically significant increase in the risk of VTEs for VEGFR‐TKIs versus controls in overall population (RR0.912, 95%CI: 0.617–1.348, p = 0.643). On subgroup analysis, no significant increase in the risk of VTEs was found among different VEGFR‐TKIs or tumor types. No evidence of publication bias was observed. The use of VEGFR‐TKIs does not significantly increase the risk of VTEs, the risk of VTEs in patients with cancer is driven predominantly by tumor types, host factors and concomitant usage of anticancer agents. These results would provide important information for clinicians who use VEGFR‐TKIs to treat patients with solid cancer.     

Induction of neuropilin-1 and vascular endothelial growth factor by epidermal growth factor in human gastric cancer cells

The epidermal growth factor receptor (EGF-R) pathway plays a pivotal role in the progression of human gastric cancer. The angiogenic factor vascular endothelial growth factor (VEGF) has been shown to be induced by EGF in various cancer cell lines. Neuropilin-1 (NRP-1) acts as a coreceptor for VEGF-165 and increases its affinity for VEGF receptor 2 (VEGFR-2) in endothelial cells. Furthermore, NRP-1 has been found to be expressed by tumour cells and has been shown to enhance tumour angiogenesis and growth in preclinical models. We examined the expression of NRP-1 mRNA and EGF-R protein in seven human gastric cancer cell lines. NRP-1 expression was expressed in five of seven cell lines, and EGF-R expression closely mirrored NRP-1 expression. Moreover, in EGF-R-positive NCI-N87 and ST-2 cells, EGF induced both NRP-1 and VEGF mRNA expression. C225, a monoclonal antibody to EGF-R, blocked EGF-induced NRP-1 and VEGF expression in NCI-N87 cells in a dose-dependent manner. The treatment of NCI-N87 cells with EGF resulted in increases in phosphorylation of Erk1/2, Akt, and P38. Blockade of the Erk, phosphatidylinositol-3 kinase/Akt, or P38 pathways in this cell line prevented EGF induction of NRP-1 and VEGF. These results suggest that regulation of NRP-1 expression in human gastric cancer is intimately associated with the EGF/EGF-R system. Activation of EGF-R might contribute to gastric cancer angiogenesis by a mechanism that involves upregulation of VEGF and NRP-1 expression via multiple signalling pathways.     

Safety profile of combined therapy inhibiting EFGR and VEGF pathways in patients with advanced non‐small‐cell lung cancer: A meta‐analysis of 15 phase II/III randomized trials

The efficacy of combined vascular endothelial growth factor (VEGF) and epidermal growth factor receptor (EGFR) inhibition in patients with advanced non‐small‐cell lung cancer (NSCLC) was well studied. However, few studies focused on the risk and adverse events (AEs) of combined targeted therapy. The aim of this meta‐analysis was to evaluate the safety profile of combined targeted therapy against EFGR and VEGF in patients with advanced NSCLC. A comprehensive literature search in MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials (CENTRAL), ASCO Abstracts and ESMO Abstracts was conducted. Eligible studies were randomized clinical trials (RCTs) that compared safety profile of combined therapy inhibiting EFGR and VEGF pathways with control groups (placebo, single EGFR or VEGF inhibition therapy, chemotherapy or a combination of them) in patients with advanced NSCLC. The endpoints included treatment discontinuation, treatment‐related deaths and AEs. The search identified 15 RCTs involving 6,919 patients. The outcomes showed that three of four pairwise comparisons detected more discontinuation due to AEs in combined targeted therapy, with odds ratio (OR) compared with the control groups ranged from 1.97 to 2.29. Treatment with combined inhibition therapy was associated with several all‐grade and grade 3 or 4 AEs (e.g. rash, diarrhea and hypertension). Also, there was a significantly higher incidence of treatment‐related deaths in combined inhibition using vandetanib versus single EGFR inhibition therapy (OR = 1.97, 95% CI 1.19–3.28). In conclusion, combined inhibition therapy against EGFR and VEGF in patients with advanced NSCLC was associated with increased toxicity. Increased AEs hinder patient compliance and reduce their quality of life, leading to dose reduction or discontinuation.     

Investigational agents in the management of non-small cell lung cancer

Novel therapeutic agents are playing an increasingly prominent role in the treatment of non-small cell lung cancer (NSCLC). Drugs that target important oncogenic proteins or pathways, whether used as monotherapy or in combination with established regimens, have largely supplanted traditional cytotoxic agents in modern clinical trials. In particular, inhibitors of the epidermal growth factor receptor (EGFR) and/or vascular endothelial growth factor (VEGF) pathways have shown significant clinical activity and in some cases have changed the standard of care for advanced NSCLC. In the past year, an unprecedented number of trials have been reported using agents targeting the EGFR (erlotinib, gefitinib, cetuximab), VEGF (bevacizumab) or the VEGF receptor (sorafenib, sunitinib, cediranib), and inhibitors of both pathways (vandetanib, erlotinib, or cetuximab plus bevacizumab). This review focuses on recently reported trials of targeted agents that have the potential to affect the treatment of patients with NSCLC.     

Tas13D inhibits growth of SMMC-7721 cell via suppression VEGF and EGF expression

Objective: Taspine, isolated from Radix et Rhizoma Leonticis has demosntrated potential proctiective effectsagainst cancer. Tas13D, a novel taspine derivative synthetized by structure-based drug design, have been shownto possess interesting biological and pharmacological activities. The current study was designed to evaluateits antiproliferative activity and underlying mechanisms. Methods: Antiproliferative activity of tas13D wasevaluated by xenograft in athymic mice in vivo, and by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazoliumbromide (MTT) and cell migration assays with human liver cancer (SMMC-7721) cell lines in vitro. Dockingbetween tas13D and VEGFR and EGFR was studied by with a Sybyl/Surflex module. VEGF and EGF andtheir receptor expression was determined by ELISA and real-time PCR methods, respectively. Results: Ourpresent study showed that tas13D inhibited SMMC-7721 xenograft tumor growth, bound tightly with the activesite of kinase domains of EGFR and VEGFR, and reduced SMMC-7721 cell proliferation (IC=34.7 μmol/L)and migration compared to negative controls. VEGF and EGF mRNAs were significantly reduced by tas13Dtreatment in a dose-dependent manner, along with VEGF and EGF production. Conclusion: The obtained resultssuggest that tas13D inhibits tumor growth and cell proliferation by inhibiting cell migration, downregulatingmRNA expression of VEGF and EGF, and decreasing angiogenic factor production. Tas13D deserves furtherconsideration as a chemotherapeutic agent.     

Simultaneous targeting of Src kinase and receptor tyrosine kinase results in synergistic inhibition of renal cell carcinoma proliferation and migration

There have been recent improvements in the treatment for metastatic renal cell carcinoma (RCC) with receptor tyrosine kinase (RTK) inhibitors being one of newer treatment options. We hypothesized that simultaneous targeting of Src kinase and the RTK may have synergistic effects to further improve therapies on metastatic RCC. The effects of Src kinase inhibitor saracatinib and multiple RTK inhibitor sunitinib on RCC cell line (ACHN) and Caki-1 were studied. Saracatinib alone or in combination with sunitinib inhibited the migration of ACHN and Caki-1 cells in vitro. Activation of migration related components FAK, P130Cas and Paxillin were blocked by saracatinib at 0.05- to 3-μM concentrations. Combined treatment resulted in improved growth inhibition, greater loss of the S phase cell population and decreased clonogenic colony formation compared to sunitinib alone in the metastatic Caki-1 line. Molecular studies in Caki-1 showed that saracatinib alone and in combination with sunitinib inhibited phosphorylation of the cell progression regulator c-Myc in a dose-dependent manner. Sunitinib alone or in combination suppressed cyclin-D1 expression with the combination showing greater dose-dependent effect. Sunitinib inhibited vascular endothelial growth factor (VEGF) secretion through the inhibition of STAT3 signaling and VEGF biosynthesis. HIF1-α expression in normoxic and hypoxic conditions in Caki-1 cells was inhibited by either saracatinib or sunitinib when administered alone, however, a greater reduction occurred when these compounds were given in combination. Targeting Src kinase and RTK simultaneously with saracatinib and sunitinib resulted in 70-80% blockade of RCC cell migration, synergistic inhibition of cell growth and reduction of acquired drug resistance in Caki-1 cells. The results show promise for combination targeted therapy of RCC.     

Functional significance of VEGFR‐2 on ovarian cancer cells

Vascular endothelial growth factor receptor (VEGFR) has recently been discovered on ovarian cancer cells, but its functional significance is unknown and is the focus of this study. By protein analysis, A2780‐par and HeyA8 ovarian cancer cell lines expressed VEGFR‐1 and HeyA8 A2774, and SKOV3ip1 expressed VEGFR‐2. By in situ hybridization (ISH), 85% of human ovarian cancer specimens showed moderate to high VEGFR‐2 expression, whereas only 15% showed moderate to high VEGFR‐1 expression. By immunofluorescence, little or no VEGFR‐2 was detected in normal ovarian surface epithelial cells, whereas expression was detected in 75% of invasive ovarian cancer specimens. To differentiate between the effects of tumor versus host expression of VEGFR, nude mice were injected with SKOV3ip1 cells and treated with either human VEGFR‐2 specific antibody (1121B), murine VEGFR‐2 specific antibody (DC101) or the combination. Treatment with 1121B reduced SKOV3ip1 cell migration by 68% (p < 0.01) and invasion by 72% (p < 0.01), but exposure to VEGFR‐1 antibody had no effect. Treatment with 1121B effectively blocked VEGF‐induced phosphorylation of p130Cas. In vivo treatment with either DC101 or 1121B significantly reduced tumor growth alone and in combination in the SKOV3ip1 and A2774 models. Decreased tumor burden after treatment with DC101 or 1121B correlated with increased tumor cell apoptosis, decreased proliferative index, and decreased microvessel density. These effects were significantly greater in the combination group (p < 0.001). We show functionally active VEGFR‐2 is present on most ovarian cancer cells. The observed anti‐tumor activity of VEGF‐targeted therapies may be mediated by both anti‐angiogenic and direct anti‐tumor effects. © 2008 Wiley‐Liss, Inc.     

EGFR,pMAPK, pAkt and PTEN status by immunohistochemistry: correlation with clinical outcome in HER2-positive metastatic breast cancer patients treated with trastuzumab

BackgroundIn an attempt to identify markers of resistance to trastuzumab, we evaluated both the profiling of human epidermal growth factor receptor 2 (HER2)-positive tumor cells measuring the relative levels of EGFR, pMAPK, pAkt and PTEN and their correlations with clinical outcome in HER2-positive metastatic breast cancer patients treated with trastuzumab.Patients and methodsTumor tissues for this retrospective analysis were available from 45 out of 76 patients with metastatic breast cancer treated from April 1999 to March 2006 with trastuzumab-based therapy at our Institution. Evaluations of EGFR, pMAPK, pAkt and PTEN status by immunohistochemistry (IHC) were carried out on all 45 tissue samples and their correlations with response to trastuzumab, incidence of central nervous system (CNS) metastases, time to progression (TTP), overall survival from diagnosis of breast cancer (OS1), from diagnosis of metastatic disease (OS2) and from the start of trastuzumab (OS3) were analyzed.ResultsWe observed that TTP (P = 0.001) and median OS2 and OS3 were significantly longer in patients responsive to trastuzumab-based regimen compared with nonresponsive patients. EGFR, pMAPK, pAkt and PTEN status by IHC were not significantly associated with response to trastuzumab, TTP, overall survival (OS1, OS2, OS3) and CNS metastases incidence. A trend for shorter OS3 was observed for pMAPK-positive patients compared with pMAPK-negative patients (22.8 versus 31.2 months; P = 0.076). Median OS1 resulted shorter in 22 pAkt-positive patients (69.8 months) compared with 23 pAkt-negative patients (108.2 months); P = 0.091. It is likely that high expression of pMAPK (pMAPK-positive status) or pAkt (pAkt-positive status) could identify a subgroup of HER2-positive tumors with high activity of proliferation and survival pathways and with resistance to trastuzumab.ConclusionsIn HER2-positive metastatic breast cancers, EGFR, pMAPK, pAkt and PTEN status evaluated by IHC was not significantly associated with response to trastuzumab, TTP, OS and CNS metastases incidence. However, HER2 status determined by IHC and/or FISH assays may not be sufficient to predict response to trastuzumab-based therapy.