Augmentation of radiation response with the vascular targeting agent ZD6126

PURPOSE: To examine the antivascular and antitumor activity of the vascular targeting agent ZD6126 in combination with radiation in lung and head-and-neck (H and N) cancer models. The overall hypothesis was that simultaneous targeting of tumor cells (radiation) and tumor vasculature (ZD6126) might enhance tumor cell killing. METHODS AND MATERIALS: A series of in vitro studies using human umbilical vein endothelial cells (HUVEC) and in vivo studies in athymic mice bearing human lung (H226) and H and N (squamous cell carcinoma [SCC]1, SCC6) tumor xenografts treated with ZD6126 and/or radiation were performed. RESULTS: ZD6126 inhibited the capillary-like network formation in HUVEC. Treatment of HUVEC with ZD6126 resulted in cell cycle arrest in G2/M, with decrease of cells in S phase and proliferation inhibition in a dose-dependent manner. ZD6126 augmented the cell-killing effect of radiation and radiation-induced apoptosis in HUVEC. The combination of ZD6126 and radiation further decreased tumor vascularization in an in vivo Matrigel angiogenesis assay. In tumor xenografts, ZD6126 enhanced the antitumor activity of radiation, resulting in tumor growth delay. CONCLUSIONS: These preclinical studies suggest that ZD6126 can augment the radiation response of proliferating endothelial H and N and lung cancer cells. These results complement recent reports suggesting the potential value of combining radiation with vascular targeting/antiangiogenic agents.     

EGFR blockade with ZD1839 ("Iressa") potentiates the antitumor effects of single and multiple fractions of ionizing radiation in human A431 squamous cell carcinoma. Epidermal growth factor receptor

PURPOSE: Signaling pathways initiated by the epidermal growth factor receptor (EGFR) play important roles in the response to ionizing radiation. In this study the consequences of inhibiting the EGFR on the response of A431 cells (human vulvar squamous cell carcinoma cells that overexpress EGFR) to radiation, were investigated in vitro and in vivo, using the selective EGFR-tyrosine kinase inhibitor, ZD1839 ("Iressa"). METHODS AND MATERIALS: The effect of ZD1839 on proliferation, apoptosis, and clonogenic survival after radiation was determined in vitro. For in vivo studies, athymic nude mice with established subcutaneous A431 xenografts (approximately 100 mm(3)) were treated with either a single 10 Gy fraction or 4 daily 2.5 Gy fractions of radiation with or without ZD1839 (75 mg/kg/day intraperitoneally for 10 days) to determine effects on tumor growth delay. RESULTS: Treatment of A431 cells with ZD1839 in vitro reduced proliferation, increased apoptosis, and reduced clonogenic survival after radiation. Strikingly greater than additive effects of ZD1839 in combination with radiation on tumor growth delay were observed in vivo after either a single 10 Gy fraction (enhancement ratio: 1.5) or multiple 4 x 2.5 Gy fractions (enhancement ratio: 4). ZD1839 reduced tumor vascularity, as well as levels of vascular endothelial growth factor (VEGF) protein and mRNA induced by stimulation with epidermal growth factor (EGF), suggesting a possible role of inhibition of angiogenesis in the effect. CONCLUSIONS: Inhibiting EGFR-mediated signal transduction cascades with ZD1839 potentiates the antitumor effect of single and multiple fractions of radiation. These data provide preclinical rationale for clinical trials of EGFR inhibitors including ZD1839 in combination with radiation.     

Enhancement of antitumor activity of ionizing radiation by combined treatment with the selective epidermal growth factor receptor-tyrosine kinase inhibitor ZD1839 (Iressa).

PURPOSE: The epidermal growth factor receptor (EGFR) is expressed in the majority of human epithelial cancers and has been implicated in the development of cancer cell resistance to cyotoxic drugs and to ionizing radiation. Experimental Design: We used ZD1839, a selective small molecule EGFR tyrosine kinase inhibitor currently in clinical development. We tested the antiproliferative and the proapoptotic activity of ZD1839 in combination with ionizing radiation in human colon (GEO), ovarian (OVCAR-3), non-small cell lung (A549 and Calu-6), and breast (MCF-7 ADR) cancer cell lines. The antitumor activity of this combination was also tested in nude mice bearing established GEO colon cancer xenografts. RESULTS: With ionizing radiation or ZD1839, a dose-dependent growth inhibition was observed in all of the cancer cell lines growing in soft agar. A cooperative antiproliferative and proapoptotic effect was obtained when cancer cells were treated with ionizing radiation followed by ZD1839. This effect was accompanied by inhibition in the expression of the antiapoptotic proteins bcl-xL and bcl-2, and by a suppression of the activated (phosphorylated) form of akt protein. Treatment of mice bearing established human GEO colon cancer xenografts with radiotherapy (RT) resulted in a dose-dependent tumor growth inhibition that was reversible upon treatment cessation. Long term GEO tumor growth regressions were obtained after RT in combination with ZD1839. This resulted in a significant improvement in survival of these mice as compared with the control group (P < 0.001), the RT-treated group (P < 0.001), or the ZD1839-treated group (P < 0.001). The only mice alive 10 weeks after tumor cell injection were in the RT-plus-ZD1839 group. Furthermore, 10% of mice in this group were alive and tumor-free after 26 weeks. Similar results were obtained in mice bearing established human A549 lung adenocarcinoma xenografts. Finally, the combined treatment with RT plus ZD1839 was accompanied by a significant potentiation in the inhibition of transforming growth factor alpha, vascular epidermal growth factor, and basic fibroblast growth factor expression in cancer cells, which resulted in significant antiangiogenic effects as determined by immunohistochemical count of neovessels within the GEO tumors. CONCLUSION: This study provides a rationale for evaluating in cancer patients the combination of ionizing radiation and selective EGFR tyrosine kinase inhibitors such as ZD1839.     

ZD1839 (Iressa) induces antiangiogenic effects through inhibition of epidermal growth factor receptor tyrosine kinase

Epidermal growth factor receptor (EGFR) tyrosine kinase is a potential target for anticancer therapy. ZD1839 (Iressa) is a selective inhibitor of EGFR tyrosine kinase. In this study, we investigated the question as to whether the antitumor effect of ZD1839 is partly attributable to antiangiogenic activity and the potential mechanisms involved. Both ZD1839 and SU5416 [a vascular endothelial growth factor (VEGF)-receptor tyrosine kinase inhibitor] inhibited the migration of human umbilical vein endothelial cell cocultivated with EGF-stimulated cancer cells. ZD1839 also inhibited EGF-induced migration and the formation of tube-like structures by human microvascular endothelial cells. Moreover, ZD1839 almost completely blocked EGF-induced neovascularization of mice cornea, and SU5416 partially blocked neovascularization. In contrast, ZD1839 did not inhibit VEGF-induced angiogenesis. However, EGF-induced up-regulation of the angiogenic factors, VEGF and IL-8, was almost completely blocked by ZD1839. The antitumor effects of ZD1839 could, therefore, be mediated in part by the inhibition of tumor angiogenesis through direct effects on microvascular endothelial cells that express EGFR and also through reduced production of proangiogenic factors by tumor cells.     

Inhibition of growth factor production and angiogenesis in human cancer cells by ZD1839 (Iressa), a selective epidermal growth factor receptor tyrosine kinase inhibitor.

The transforming growth factor-alpha/epidermal growth factor receptor (TGF-alpha-EGFR) autocrine pathway, which is involved in the development and the progression of human epithelial cancers, controls, in part, the production of angiogenic factors. These angiogenic factors, including vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF), are secreted by cancer cells to stimulate normal endothelial cell growth through paracrine mechanisms. ZD1839 (Iressa) is a p.o.-active, selective EGFR-tyrosine kinase inhibitor (TKI) in clinical trials in cancer patients. In this study, we evaluated the antiangiogenic and antitumor activity of ZD1839 in human colon (GEO, SW480, and CaCo2), breast (ZR-75-1 and MCF-7 ADR), ovarian (OVCAR-3), and gastric (KATO III and N87) cancer cells that coexpress TGF-alpha and EGFR. ZD1839 treatment determined a dose- and time-dependent growth inhibition accompanied by the decrease of VEGF, bFGF and TGF-alpha production in vitro. Treatment of immunodeficient mice bearing well-established, palpable GEO xenografts with ZD1839 determined a cytostatic dose-dependent tumor growth inhibition. Immunohistochemical analysis of GEO tumor xenografts after ZD1839 treatment revealed a significant dose-dependent reduction of TGF-alpha, bFGF, and VEGF expression in cancer cells and of neoangiogenesis, as determined by microvessel count. Furthermore, the antitumor activity of ZD1839 was potentiated in combination with the cytotoxic drug paclitaxel in GEO tumor xenografts. Tumor regression was observed in all mice after treatment with ZD1839 plus paclitaxel, and it was accompanied by a significant potentiation in inhibition of TGF-alpha, VEGF, and bFGF expression with a few or no microvessels. Furthermore, 6 of 16 mice bearing well-established, palpable GEO xenografts had no histological evidence of GEO tumors at the end of treatment with ZD1839 plus paclitaxel. These results demonstrate that the antitumor effect of ZD1839 is accompanied by inhibition in the production of autocrine and paracrine growth factors that sustain autonomous local growth and facilitate angiogenesis, and that this effect can be potentiated by the combined treatment with certain cytotoxic drugs, such as paclitaxel.     

Enhancement of tumor radioresponse by combined treatment with gefitinib (Iressa, ZD1839), an epidermal growth factor receptor tyrosine kinase inhibitor, is accompanied by inhibition of DNA damage repair and cell growth in oral cancer

Molecular blockade of EGFR with either an EGFR MAb or an EGFR TKI enhances the radiosensitivity of human SCCs. In the present study, we investigated whether treatment with the EGFR TKI gefitinib (Iressa, ZD1839) improves the response to radiotherapy in the OSCC cell lines HSC2 and HSC3. We examined potential mechanisms that may contribute to the enhanced radiation response induced by gefitinib. Growth inhibition was observed in vitro with radiation or gefitinib. A cooperative antiproliferative effect was obtained when cancer cells were treated with radiation followed by gefitinib. Cells treated with a combination of radiation and gefitinib arrested in G(1) and G(2)-M phases, with a decrease in the S-phase population. While radiation alone did not significantly affect MEK1/2 and p38 MAPK autophosphorylation, the combination of gefitinib and radiation completely inhibited the downstream signaling of EGFR. Results from DNA damage repair analysis in cultured OSCC cells demonstrated that gefitinib had a strong inhibitory effect on DNA-PKc pathways after radiation. Tumor xenograft studies demonstrated that the combination of gefitinib and radiation caused growth inhibition and tumor regression of well-established OSCC tumors in athymic mice; tumor volume was reduced from 1,008.2 to 231.4 mm(3) in HSC2 cells (p < 0.01) and from 284.2 to 12.4 mm(3) in HSC3 cells (p < 0.01). Immunohistochemical analysis of OSCC xenografts revealed that gefitinib caused a striking decrease in tumor cell proliferation when combined with radiotherapy. Overall, we conclude that gefitinib enhances tumor radioresponse by multiple mechanisms that may involve antiproliferative growth inhibition and effects on DNA repair after exposure to radiation.     

Cooperative antitumor effect of multitargeted kinase inhibitor ZD6474 and ionizing radiation in glioblastoma.

PURPOSE: Glioblastoma multiforme is an aggressive disease in which vascular endothelial growth factor (VEGF) and the EGF receptor (EGFR) are implicated in tumor growth, relapse, and resistance to radiotherapy and chemotherapy. The VEGF receptors VEGFR-1 (flt-1) and VEGFR-2 (KDR), typically present on endothelial cells, have also been identified in human glioblastoma tissues and cell lines. In addition, EGFR is dysregulated in the majority of human glioblastomas and EGFR overexpression correlates with shorter survival. We have investigated the antitumor and antiangiogenic effect of ZD6474, an inhibitor of both VEGFR and EGFR signaling as a single agent and in combination with ionizing radiation. EXPERIMENTAL DESIGN: We have used ZD6474 and/or ionizing radiation in human glioblastoma cell lines D54 and U251 in vitro and in nude mice bearing established xenografts. The effects of treatment on tumor blood vessels and protein expression were evaluated by Western blot and immunohistochemistry. RESULTS: As single agents, ionizing radiation and ZD6474 caused a dose-dependent inhibition of soft agar growth in D54 and U251 cell lines, whereas a cooperative effect was obtained in combination. Treatment of mice bearing D54 xenografts with either ZD6474 or radiotherapy alone caused tumor growth inhibition that was reversible upon treatment cessation. A cooperative and long-lasting inhibition of tumor growth was obtained with ZD6474 in combination with concomitant radiotherapy. The antiproliferative effect was accompanied by inhibition of VEGF protein expression and inhibition of angiogenesis as measured by vessel counting. CONCLUSION: This study shows the antitumor activity of ZD6474 in combination with ionizing radiation in glioblastoma both in vitro and in vivo, and provides a scientific rationale to evaluate ZD6474 alone or in combination with radiotherapy in patients affected by this disease.     

ZD1839 (Iressa) in non-small-cell lung cancer

The epidermal growth factor receptor (EGFR) signaling pathway plays an important role in a number of processes that are key to tumor progression, including cell proliferation, angiogenesis, metastatic spread, and inhibition of apoptosis. EGFR is expressed or overexpressed in non-small-cell lung cancer (NSCLC), and EGFR-mediated growth has been associated with advanced disease and poor prognosis in NSCLC patients. ZD1839 (Iressa) is an orally active, selective EGFR-tyrosine kinase inhibitor that blocks EGFR signal transduction. In preclinical studies using NSCLC cell lines, ZD1839 has been shown to inhibit tumor cell growth. In addition, ZD1839, as monotherapy and in combination with commonly used cytotoxic agents, has produced growth delay in NSCLC human xenografts. Preliminary results from phase I trials in patients with advanced disease have shown that ZD1839 has excellent bioavailability, an acceptable tolerability profile, and promising clinical activity in patients with a variety of tumor types, particularly in NSCLC. ZD1839 is currently in phase III clinical development for the treatment of advanced NSCLC.     

ZD1839 (Iressa): an orally active inhibitor of epidermal growth factor signaling with potential for cancer therapy

The epidermal growth factor receptor (EGFR) is a promising target for anticancer therapy because of its role in tumor growth, metastasis and angiogenesis, and tumor resistance to chemotherapy and radiotherapy. We have developed a low-molecular-weight EGFR tyrosine kinase inhibitor (EGFR-TKI), ZD1839 (Iressa(2) ). ZD1839, a substituted anilinoquinazoline, is a potent EGFR-TKI (IC(50) = 0.033 micro M) that selectively inhibits EGF-stimulated tumor cell growth (IC(50) = 0.054 micro M) and that blocks EGF-stimulated EGFR autophosphorylation in tumor cells. In studies with mice bearing a range of human tumor-derived xenografts, ZD1839 given p.o. once a day inhibited tumor growth in a dose-dependent manner. The level of expression of EGFR did not determine xenograft tumor sensitivity to ZD1839. Long-term ZD1839 (>3 months) treatment of mice bearing A431 xenografts was well tolerated, and ZD1839 completely inhibited tumor growth and induced regression of established tumors. No drug-resistant tumors appeared during ZD1839 treatment, but some tumors regrew after drug withdrawal. These studies indicate the potential utility of ZD1839 in the treatment of many human tumors and indicate that continuous once-a-day p.o. dosing might be a suitable therapeutic regimen.     

Antitumor effects of ZD6474 on head and neck squamous cell carcinoma

Angiogenesis is required for tumor growth and metastasis and, therefore, represents a target for cancer treatment. While many factors have been implicated in promoting angiogenesis, vascular endothelial growth factor (VEGF) plays a key role in tumor angiogenesis. ZD6474 is a potent VEGF receptor-2 (VEGFR-2) tyrosine kinase inhibitor which also has activity against the epidermal growth factor receptor (EGFR) tyrosine kinase. The purpose of this study was to investigate the sensitivity of head and neck squamous cell carcinoma (HNSCC) cell lines to ZD6474, and to evaluate its antitumor efficacy on HNSCC xenografts. This is the first demonstration of antitumor effects of ZD6474 on HNSCC. In vitro ZD6474 displayed antiproliferative effects on HNSCC cells and inhibition of VEGFR-2 and EGFR pathways. In vivo ZD6474 displayed antitumor activity, induced apoptosis and antiangiogenic activity on nude mice bearing an established xenograft of YCU-H891 cells. These results suggest that ZD6474 has the potential to inhibit two key pathways in tumor growth via inhibition of VEGF-dependent tumor angiogenesis and via inhibition of EGFR-dependent tumor cell proliferation.     

Combination of a selective cyclooxygenase-2 inhibitor with epidermal growth factor receptor tyrosine kinase inhibitor ZD1839 and protein kinase A antisense causes cooperative antitumor and antiangiogenic effect.

PURPOSE: Epidermal growth factor receptor (EGFR) and protein kinase A type I(PKAI) play an important role in the control of cancer cell growth and angiogenesis. Inhibitors of EGFR and PKAI have antitumor activity in vitro and in vivo in a variety of tumor types, and some of these agents are active after oral administration. Increasing evidence shows that cyclooxygenase (COX)-2 also plays a role in promoting cancer cell proliferation and angiogenesis. COX-2 expression can be induced by EGFR activation and is regulated by cAMP and PKA. Combination of an EGFR inhibitor with a nonselective COX-1/COX-2 inhibitor prevents the development of intestinal cancer in nude mice. Therefore, we investigated whether any cooperative antitumor effect can be obtained by the combined blockade of COX-2, EGFR, and PKAI. EXPERIMENTAL DESIGN: The COX-2 inhibitor SC-236 was combined with the selective EGFR tyrosine kinase inhibitor ZD1839 (Iressa) and the DNA/RNA-mixed backbone oligonucleotide AS-PKAI to study their effect on human cancer growth and angiogenesis, measuring vascular endothelial growth factor (VEGF) and basic fibroblast growth factor expression and vessel formation, in vitro and after oral administration of these agents in mice. RESULTS: A cooperative effect was observed with SC-236 in combination with either ZD1839 or AS-PKAI, as well as with all three agents together, on the proliferation of human colon and breast cancer cells in soft agar at doses that were ineffective for each agent alone. The antiproliferative effect was accompanied by inhibition of COX-2 expression. Moreover, combination of SC-236 with either agent or the triple combination markedly reduced VEGF secretion in the conditioned medium and completely suppressed VEGF and basic fibroblast growth factor expression. In nude mice bearing human colon cancer xenografts, a low, noninhibitory dose of SC-236 with ZD1839 and AS-PKAI, all given p.o., caused a dramatic cooperative antitumor effect, with no histological evidence of tumor in 60% of mice 5 weeks after treatment withdrawal, at which time all mice were alive. Moreover, analysis of tumor specimens revealed inhibition of vessel formation and expression of COX-2 and VEGF. CONCLUSIONS: This is the first demonstration that three novel agents blocking multiple signaling pathways, in absence of cytotoxic drugs, may have a potent antitumor and antiangiogenic activity after oral administration. Because all agents are under clinical evaluation, our results provide a rationale to translate this feasible therapeutic strategy into a clinical setting.     

The antitumor and antiangiogenic activity of vascular endothelial growth factor receptor inhibition is potentiated by ErbB1 blockade.

PURPOSE: Receptor tyrosine kinases of the ErbB family play important roles in the control of tumor growth. Vascular endothelial growth factor (VEGF) stimulates endothelial cell proliferation, enhances vascular permeability, and plays an important role in tumor vascularization. We evaluated the effects of selective VEGF receptor (VEGFR; PTK787/ZK222584) and ErbB (PKI166 and ZD1839) inhibitors on tumor growth and angiogenesis and asked whether additional therapeutic benefit was conferred by combination treatment. EXPERIMENTAL DESIGN: The antitumor activity of each inhibitor alone or in combination was assessed in human cancer models in immunocompromised mice. ErbB receptor expression and activation of downstream signaling pathway was evaluated in both tumor and endothelial cells. RESULTS: Both ErbB inhibitors significantly enhanced the antitumor activity of PTK787/ZK222584. In vitro, ErbB1 inhibition blocked VEGF release by tumor cells and proliferation of both tumor and endothelial cells. In an in vitro angiogenesis assay, epidermal growth factor (EGF) stimulated the release of VEGF by smooth muscle cells resulting in increased angiogenesis, a response blocked by administration of PTK787/ZK222584. Under basal condition, both ZD1839 and PTK787/ZK222584 blocked sprouting, likely via inhibition of an autocrine ErbB1 loop and VEGFR signaling, respectively, in endothelial cells. In conditions of limiting VEGF, EGF plays an important role in endothelial cell proliferation, survival, and sprouting. CONCLUSION: We have shown that activation of ErbB1 triggers a plethora of effects, including direct effects on tumor and endothelial cells and indirect effects mediated via induction of VEGF release. Simultaneous blockade of ErbB1 and VEGFR pathways results in a cooperative antitumor effect, indicating that this combination may represent a valid therapeutic strategy.     

The effects of ZD1839 (Iressa), a highly selective EGFR tyrosine kinase inhibitor, as a radiosensitiser in bile duct carcinoma cell lines

The signaling pathway that is initiated by binding of epidermal growth factor receptor (EGFR) and results in sustained signaling through PI3K plays an important role in a tumor's response to ionizing radiation. The current in vitro study explored both the effects of ZD1839 (Iressa), a highly selective EGFR tyrosine kinase inhibitor, as a radiosensitiser for bile duct carcinoma cell lines and ZD1839's general effects on cell growth in the same two lines. Secondly, we ensured suppression of radiation-induced phosphorylation of EGFR by ZD1839 using an immunoprecipitation technique. Furthermore, we examined radiation-induced phosphorylation of ERK, p38, JNK, and AKT with or without inhibitor with use of Western blot techniques and performed clonogenic assays to confirm radiosensitivity in the presence of a drug. ZD1839 inhibited cell growth of both cell lines and suppressed radiation-induced phosphorylation of EGFR. After exposure to radiation, there was an increase in phosphorylation of AKT as shown by Western blot. Treatment with either ZD1839 or LY294002 (the latter, a PI3K inhibitor) suppressed phosphorylation of AKT by Western blot. Both ZD1839 and LY294002 significantly suppressed colony formation by clonogenic assay; however, U0126 (a MEK1/2 inhibitor), SB203580 (a p38 inhibitor), and SP600125 (a JNK inhibitor) had no effect on colony formation. These results suggest that AKT may be a useful target molecule for enhancement of radiotherapy effect and that ZD1839 may have an important role in combination with radiotherapy for patients with bile duct carcinoma.     

表皮生长因子受体酪氨酸激酶抑制剂ZD1839与奥沙利铂联合对人肺癌A549细胞的作用

背景与目的:ZD1839是一种表皮生长因子受体酪氨酸激酶的小分子抑制剂,是目前肺癌分子靶向治疗中较为成熟的药物,因其单药临床有效率低,如何与化疗联合提高抗癌效应受到关注.本实验通过研究ZD1839联合奥沙利铂的不同给药方案对人肺腺癌细胞A549的杀伤作用,探讨两药联合的最佳模式.方法:以药物联合效应测定方法,评价ZD1839和奥沙利铂不同给药顺序对A549细胞的抑制作用,以流式细胞仪测定不同联合方案对A549细胞周期分布及凋亡率的影响.观察ZD1839、奥沙利铂不同给药方案作用时,裸鼠A549细胞移植瘤生长情况,测定肿瘤生长抑制率.结果:先奥沙利铂后ZD1839的序贯给药方案表现出明显的协同作用,药物联合指数为0.51±0.01;而先ZD1839后给予奥沙利铂时,药物联合指数为1.56±0.03,两药间为拮抗作用.先奥沙利铂后ZD1839组G2/M期细胞比例与其他组相比明显增加,达到37.9%(P＜0.05),细胞凋亡率达到22.3%.体内实验表明,先奥沙利铂后ZD1839组抑瘤率最高,达到58.9%;而先奥沙利铂 ZD1839 24 h后ZD1839 48 h组的抑瘤率为52.4%,ZD1839后奥沙利铂组的抑瘤率为30.6%.结论:先奥沙利铂后ZD1839序贯给药对A549细胞增殖的抑制作用更强.     

Combined anti-fetal liver kinase 1 monoclonal antibody and continuous low-dose doxorubicin inhibits angiogenesis and growth of human soft tissue sarcoma xenografts by induction of endothelial cell apoptosis

Vascular endothelial growth factor (VEGF) and VEGF receptor 2 [fetal liver kinase 1 (Flk-1)/kinase insert domain-containing receptor] have been shown to play a major role in tumor angiogenesis. In this study, we investigated whether anti-Flk-1 monoclonal antibody DC101 could therapeutically inhibit growth and angiogenesis of human soft tissue sarcoma, and we explored its capacity to enhance the tumoricidal effects of doxorubicin. Treatment of well-established leiomyosarcoma SKLMS-1 and rhabdomyosarcoma RD xenografts in severe combined immunodeficient mice with DC101 resulted in significant antitumor activity. In a parallel study, we compared tumor inhibition with continuous low-dose "antiangiogenic" schedule versus once-every-2-weeks high-dose standard schedule of doxorubicin. We found that continuous low-dose treatment inhibited the tumor growth of RD xenografts about 46.5% of that with standard-schedule treatment, but that continuous low-dose treatment did not inhibit the tumor growth of SKLMS-1 xenografts. Notably, combined DC101 and continuous low-dose doxorubicin resulted in more effective growth inhibition of SKLMS-1 and RD xenografts than has been observed with any agent alone in a long-term s.c. tumor xenograft model. The combination therapy was associated with no additional toxicity to the host animal compared with low-dose doxorubicin alone. Histological examination of xenografts showed significantly reduced microvessel counts in the tumors given combined therapy compared with the tumors given either agent alone. These results are consistent with an enhanced inhibition of angiogenesis in vivo by combined DC101 and doxorubicin using Matrigel plug assay. Additionally, DC101 plus doxorubicin directly exerted enhanced inhibitory effects on endothelial cell migration, proliferation, and tube-like formation in vitro. Furthermore, the combination induced an enhanced apoptosis of endothelial cells that was associated with an increase of capase-3 activity. Thus, the inhibition of angiogenesis and induction of endothelial cell apoptosis are likely important mechanisms for the antitumor activity of combined DC101 and doxorubicin. Collectively, our data suggested that anti-VEGF receptor 2 in combination with continuous low-dose doxorubicin may provide a new therapeutic approach for human soft tissue sarcoma in the clinic.     

Modulation of radiation response after epidermal growth factor receptor blockade in squamous cell carcinomas: inhibition of damage repair, cell cycle kinetics, and tumor angiogenesis.

We have recently demonstrated that molecular blockade of the epidermal growth factor receptor with the anti-epidermal growth factor receptor (EGFR) monoclonal antibody C225 enhances the in vitro radiosensitivity of human squamous cell carcinomas (SCCs) derived from the head and neck. In the present study, we further investigated the capacity of C225 to modulate the in vitro and in vivo radiation response of human SCC tumor cells and xenografts, and we examined several potential mechanisms that may contribute to the enhanced radiation response induced by C225. Tumor xenograft studies demonstrated complete regression of both newly established (20 mm3) and well-established (100 mm3) SCC tumors over a 55-100 day follow-up period in athymic mice treated with the combination of C225 (i.p. injection) and radiation. Cell cycle analysis via flow cytometry confirmed that combined treatment with C225 and radiation induced an accumulation of cells in the more radiosensitive cell cycle phases (G1, G2-M) with concurrent reduction in the proportion of cells in the more radioresistant S phase. Results from sublethal damage repair and potentially lethal damage repair analyses in cultured SCC cells demonstrated a strong inhibitory effect of C225 on postradiation damage repair. Further, exposure of SCC cells to C225 induced a redistribution of DNA-dependent protein kinase from the nucleus to the cytosol, suggesting one potential mechanism whereby C225 may influence the cellular response to radiation. Immunohistochemical analysis of SCC tumor xenografts after systemic administration of C225 demonstrated inhibition of the in vivo expression of tumor angiogenesis markers, including vascular endothelial growth factor and Factor VIII. Taken together, the collective data suggest that the profound in vivo antitumor activity identified in the xenograft setting when C225 is combined with radiation derives from more than simply the antiproliferative and cell cycle effects of EGFR system inhibition. In addition to antiproliferative growth inhibition, EGFR blockade with C225 appears to influence the capacity of human SCCs to effect DNA repair after exposure to radiation, and to express classic markers of tumor angiogenesis.     

ZD1839治疗头颈部肿瘤研究进展

头颈部肿瘤多过度表达表皮生长因子受体(EGFR)。EGFR酪氨酸激酶抑制剂ZD1839可阻断EGFR介导的信号转导途径,进而抑制肿瘤细胞增殖,将肿瘤细胞阻滞在G_1期,促进肿瘤细胞凋亡并抑制血管生成,与放化疗联合应用具有协同抗肿瘤作用,可用于头颈部肿瘤的治疗。现综述ZD1839治疗头颈部肿瘤的研究进展。     

ZD1839 ('Iressa'), a specific oral epidermal growth factor receptor-tyrosine kinase inhibitor, potentiates radiotherapy in a human colorectal cancer xenograft model

The effect of ZD1839 ('Iressa'), a specific inhibitor of the tyrosine kinase activity of the epidermal growth factor receptor, on the radiation response of human tumour cells (LoVo colorectal carcinoma) was evaluated in vitro and in vivo. ZD1839 (0.5 microM, incubated days 1-5) significantly increased the anti-proliferative effect of fractionated radiation treatment (2 Gy day(-1), days 1-3) on LoVo cells grown in vitro (P=0.002). ZD1839 combined with either single or fractionated radiotherapy in mice bearing LoVo tumour xenografts, also produced a highly significant increase in tumour growth inhibition (P< or = 0.001) when compared to treatment with either modality alone. The radio-potentiating effect of ZD1839 was more apparent when radiation was administered in a fractionated protocol. This phenomenon may be attributed to an anti proliferative effect of ZD1839 on tumour cell re-population between radiotherapy fractions. These data suggest radiotherapy with adjuvant ZD1839 could enhance treatment response. Clinical investigation of ZD1839 in combination with radiotherapy is therefore warranted.     

Barbigerone, an isoflavone, inhibits tumor angiogenesis and human non-small-cell lung cancer xenografts growth through VEGFR2 signaling pathways

Purpose

We previously reported that barbigerone (BA), an isoflavone isolated from Suberect Spatholobus, exhibited inhibitory effects on proliferation of many cancer cell lines in vitro. The objective of this study was to explore whether BA could effectively suppress tumor angiogenesis and tumor growth.

Methods

Zebrafish model and Matrigel assay were performed to access the anti-angiogenesis effects of BA. A549 and SPC-A1 tumor xenografts in mice models were used to examine the antitumor activity of BA. The anti-angiogenic effects and underlying mechanisms were also investigated using human umbilical vein endothelial cells (HUVECs) and A549 cells.

Results

In zebrafish model, 2.5???mol/L of BA significantly inhibited angiogenesis. Intravenous administration of BA effectively inhibited the tumor growth of A549 and SPC-A1 xenograft models in mice. The anti-angiogenic effect was indicated by CD31 immunohistochemical staining, Matrigel plug assay, and mouse aortic ring assay. BA could inhibit vascular endothelial growth factor (VEGF)-induced cell proliferation, migration, and capillary-like tuber formation of HUVECs in a dose-dependent manner, suggesting that BA inhibited tumorigenesis by targeting angiogenesis. Western blots revealed that BA directly inhibited the phosphorylation of VEGFR2, followed by inhibiting the activations of its downstream protein kinases, including ERK, p38, FAK, AKT, and expression of iNOS, but had no effect on COX2. Additionally, BA could also down-regulate VEGF secretion in A549 cancer cells, which may correlate with the suppression of ERK, AKT activation, indicating that BA inhibits tumor angiogenesis and tumor growth through VEGFR2 signaling pathways.

Conclusions

These findings suggest that BA may be a novel candidate in inhibiting tumor angiogenesis and NSCLC tumor growth.