贝伐单抗治疗高级别脑胶质瘤的研究进展

脑胶质瘤中3/4以上的患者为高级别脑胶质瘤,其恶性程度高,术后易复发,预后极差。虽然术后同步放化疗能使高级别脑胶质瘤患者生存获益,但其仅能延长有限的生存时间。近年来,肿瘤的分子靶向治疗逐渐成为研究热点。血管内皮生长因子在脑胶质瘤及其周围组织中高表达,调控着肿瘤的生长过程,是脑胶质瘤治疗的有效靶点。贝伐单抗能够特异性地阻止血管内皮生长因子与其受体结合,抑制肿瘤血管的形成;同时还能使肿瘤血管正常化,改善血管通透性,增加肿瘤组织有效药物浓度,从而达到其抗肿瘤的作用。本文就贝伐单抗的作用机制及近些年贝伐单抗单药与联合化疗或其他药物治疗高级别脑胶质瘤的研究进展进行综述。      

'Accidental' anti-angiogenic drugs. anti-oncogene directed signal transduction inhibitors and conventional chemotherapeutic agents as examples

A number of drugs currently being tested in clinical trials as possible angiogenesis inhibitors were not originally developed with the intention of suppressing tumour angiogenesis. Thalidomide and interferon alpha are obvious examples of such drugs. This list of 'accidental' angiogenesis inhibitors may include established agents such as conventional cytotoxic chemotherapeutic drugs as well as the new generation of anticancer drugs known as anti-oncoprotein signal transduction inhibitors. With respect to the former, the potential of such drugs to inhibit angiogenesis could be the result of their ability to cause collateral damaging effects on cycling endothelial cells found in newly formed blood vessels, or inhibiting other vital endothelial cell functions necessary for angiogenesis. The antitumour vascular side-effects of chemotherapy may be optimised by administering such drugs continuously on a more frequent (e.g. weekly or even daily) basis at levels well below the maximum tolerated dose (MTD), especially when this is done in combination with newly developed anti-angiogenic drugs such as vascular endothelial cell growth factor (VEGF) receptor blocking antibodies. This strategy may minimise or delay the problems of host toxicity and acquired drug resistance. The possibility of anti-angiogenic effects mediated by signal transduction inhibitors such as ras farnesyltransferase inhibitors (ras FTI's), or drugs which block receptor tyrosine kinases (e.g. ErbB2/neu) such as Herceptin, may be the consequence of such oncogenes inducing or upregulating various pro-angiogenic molecules such as VEGF (vascular endothelial cell growth factor) in tumour cells. Hence, treatment of tumour cells with such drugs can lead to downregulation of tumour cell-associated VEGF expression and this can contribute to an anti-angiogenic effect of the drug in vivo. In addition, some of these drugs may also affect certain 'activated' endothelial cell functions directly so as to block angiogenesis. An awareness of the potential of such conventional or experimental anticancer drugs to affect tumour growth through blockade or suppression of angiogenesis has implications for how anticancer drugs may be used clinically, either alone, or in combination with other drugs to optimally treat cancer.     

Bevacizumab-induced transient remodeling of the vasculature in neuroblastoma xenografts results in improved delivery and efficacy of systemically administered chemotherapy.

PURPOSE: Dysfunctional tumor vessels can be a significant barrier to effective cancer therapy. However, increasing evidence suggests that vascular endothelial growth factor (VEGF) inhibition can effect transient "normalization" of the tumor vasculature, thereby improving tumor perfusion and, consequently, delivery of systemic chemotherapy. We sought to examine temporal changes in tumor vascular function in response to the anti-VEGF antibody, bevacizumab. EXPERIMENTAL DESIGN: Established orthotopic neuroblastoma xenografts treated with bevacizumab were evaluated at serial time points for treatment-associated changes in intratumoral vascular physiology, penetration of systemically administered chemotherapy, and efficacy of combination therapy. RESULTS: After a single bevacizumab dose, a progressive decrease in tumor microvessel density to <30% of control was observed within 7 days. Assessment of the tumor microenvironment revealed a rapid, sustained decrease in both tumor vessel permeability and tumor interstitial fluid pressure, whereas intratumoral perfusion, as assessed by contrast-enhanced ultrasonography, was improved, although this latter change abated by 1 week. Intratumoral drug delivery mirrored these changes; penetration of chemotherapy was improved by as much as 81% when given 1 to 3 days after bevacizumab, compared with when both drugs were given concomitantly, or 7 days apart. Finally, administering topotecan to tumor-bearing mice 3 days after bevacizumab resulted in greater tumor growth inhibition (36% of control size) than with monotherapy (88% bevacizumab, 54% topotecan) or concomitant administration of the two drugs (44%). CONCLUSIONS: Bevacizumab-mediated VEGF blockade effects alterations in tumor vessel physiology that allow improved delivery and efficacy of chemotherapy, although careful consideration of drug scheduling is required to optimize antitumor activity.     

Dopamine increases the efficacy of anticancer drugs in breast and colon cancer preclinical models.

PURPOSE: Because neurotransmitter dopamine inhibits vascular permeability factor/vascular endothelial growth factor (VEGF)-induced angiogenesis and as anti-VEGF agents act synergistically with anticancer drugs, we therefore investigated whether dopamine can increase the efficacies of these drugs. EXPERIMENTAL DESIGN: The effect of dopamine was investigated in human breast cancer-(MCF-7) and colon (HT29) cancer-bearing mice. Experimental groups received either dopamine or doxorubicin or dopamine plus doxorubicin in MCF-7 tumor-bearing mice, and either dopamine or 5-fluorouracil or dopamine plus 5-fluorouracil in HT29-bearing mice. Thereafter, tumor growth, angiogenesis, tumor cell apoptosis, life span, and the effect of dopamine on the growth and survival of tumor cells in vitro were determined. Finally, the effects of dopamine on tumor vascular permeability; on VEGF receptor-2, mitogen-activated protein kinase, and focal adhesion kinase phosphorylation; and also on the proliferation and migration of tumor endothelial cells were investigated. RESULTS: Dopamine, in combination with anticancer drugs, significantly inhibited tumor growth and increased the life span when compared with treatment with dopamine or anticancer drugs alone. Dopamine had no direct effects on the growth and survival of tumor cells. The antiangiogenic action of dopamine was mediated by inhibiting proliferation and migration of tumor endothelial cells through suppression of VEGF receptor-2, mitogen-activated protein kinase, and focal adhesion kinase phosphorylation. CONCLUSION: Our study shows that dopamine significantly enhances the efficacies of commonly used anticancer drugs and also indicates that an inexpensive drug like dopamine, which is being extensively used in the clinics, might have a role as an antiangiogenic agent for the treatment of breast and colon cancer.     

Radiation improves the distribution and uptake of liposomal doxorubicin (caelyx) in human osteosarcoma xenografts

Liposomal drug delivery appears to improve the antitumor effect and reduce toxicity compared with the free drug. The therapeutic index may be improved further by combining cytotoxic drugs and radiotherapy. Successful therapy requires that the cytotoxic agents reach the tumor cells. Therefore, we studied tumor growth and the microdistribution of liposomal doxorubicin (Caelyx) with and without additional ionizing radiation in human osteosarcoma xenografts in athymic mice. Caelyx was injected i.v. 1 day before single or fractionated radiotherapy. Both chemoirradiation regimens induced significant tumor growth delays and worked synergistically. Confocal laser scanning microscopy showed that intact liposomes were located in close proximity to endothelial cells, and the distribution of released doxorubicin was heterogeneous. Before radiotherapy, hardly any doxorubicin was localized in the central parts of the tumor. Radiotherapy increased the tumor uptake of doxorubicin by a factor of two to four, with drug being redistributed farther from the vessels in the tumor periphery and located around vessels in the central parts of the tumor. Colocalization of doxorubicin and hypoxic cells showed no distribution of drug into hypoxic areas. Dynamic contrast-enhanced magnetic resonance imaging (MRI) 1 day before the injection of Caelyx and 2 days after treatment start showed that the combined treatment reduced the vascular volume and the vascular transfer rate of the MRI tracer. The results show that chemoirradiation with Caelyx induces synergistic treatment effects. Improved intratumoral drug uptake and distribution are responsible to some extent for the enhanced antitumor effect.     

Angiogenesis and apoptosis

This review assembles the laboratory and clinical evidence that cytotoxic chemotherapy and antiangiogenic therapy are each dependent on endothelial cell apoptosis. During cytotoxic chemotherapy, apoptosis of endothelial cells in the vascular bed of tumors precedes apoptosis of tumor cells, even when the tumor has been made drug resistant. Administration of an angiogenesis inhibitor which is not directly cytotoxic to tumor cells can increase tumor cell apoptosis and inhibit tumor growth by inhibiting endothelial proliferation and migration and/or by inducing endothelial apoptosis. Furthermore, oncogene expression and loss of tumor suppressor gene activity can at once protect tumor cells against apoptosis and increase their angiogenic output. Both of these survival advantages conferred on the tumor can be overcome by antiangiogenic therapy. They can also be overcome by cytotoxic chemotherapy administered on a low dose 'antiangiogenic schedule' which continuously exposes endothelial cells in the tumor bed to the drug. As a result, endothelial apoptosis can be demonstrated to precede tumor cell apoptosis, and tumors regress or are inhibited, whether or not the tumor cells are resistant to the drug, and with little or no host toxicity. In contrast, cytotoxic chemotherapy administered on a 'conventional schedule' of maximal tolerated dose followed by an off-therapy interval, becomes ineffective after drug resistance is acquired.On the basis of these experimental findings, chemotherapy of cancer may possibly be improved-i.e. decreased drug resistance and decreased toxic side-effects-by changing dose and schedule to maximize apoptosis of endothelial cells in the vascular bed of tumors. Further improvement may be achieved by combining angiogenesis inhibitors with 'antiangiogenic chemotherapy'.     

加用重组人血管内皮抑素的TACE治疗对肝癌组织VEGF和MVD的影响

目的 探讨经导管肝动脉化疗栓塞（TACE）中加用抗血管生成药物治疗肝细胞癌（HCC）后肝癌组织中血管内皮生长因子（VEGF）和微血管密度（MVD）的变化情况。方法 经确诊的HCC患者85例按照数字表法随机分为TACE组（对照组）和TACE中加用重组人血管内皮抑素组（治疗组）;对照组和治疗组均给予常规化疗栓塞药物,治疗组加用重组人血管内皮抑素注射液（恩度）30mg栓塞;TACE术当天和第28天分别穿刺取肿瘤组织,对其进行VEGF和MVD的测定。结果 对照组治疗前、后的MVD分别为61.76±20.12和 62.64±22.83（P＞0.05）,VEGF分别为125.94±75.41和190.07±86.96 （P＜0.01）;治疗组治疗前、后的MVD分别为62.00±24.18和51.48±15.79（P＜0.01）,VEGF分别为127.10±77.81和88.47±75.89（P＜0.01）。 治疗组和对照组的1年生存率分别为62.5％（25／40）和61.9％（26／42）。结论 TACE能够减少HCC组织内已生成的血管数量,影响VEGF分泌,促进病灶内新生血管生成;TACE术中栓塞加用恩度能够有效降低HCC组织中MVD和VEGF表达,增加TACE抗肿瘤血管生成的效果。     

Novel antivascular efficacy of metronomic docetaxel therapy in prostate cancer: hnRNP K as a player

Tumor growth requires a competent vascular supply and angiogenesis is now considered a potential target for cancer treatment. Chemotherapeutic drugs, and docetaxel in particular, chronically administered using a frequent schedule at low dose (metronomic dosing), can cause potent antiangiogenic effects by targeting the endothelial cells of newly growing blood vessels. Because the exposure to cytotoxic drugs could target both endothelial and tumor cells, we investigated the effects of “metronomic docetaxel” on hormone refractory prostate carcinoma cells. In vitro, metronomic therapy lowered tumor cell viability, inducing apoptosis and reducing the invasive potential at 10‐ to100‐fold lower concentrations as compared with the maximum tolerated dose. Metronomic regimens resulted in a significant reduction of vascular endothelial cell growth factor expression and up‐regulation of endogenous angiogenesis inhibitors. Our studies suggest that heterogeneous nuclear ribonucleoprotein K is a mediator of the effects we observed. Targeting heterogeneous nuclear ribonucleoprotein K may serve as a specific antimetastasis and antiangiogenic therapy and could be a potential predictive marker to determine the optimal dose and schedule for metronomic chemotherapy regimens. These findings highlight the multiple effects that may characterize antiangiogenic metronomic chemotherapy and suggest that docetaxel might act as antitumor compound by affecting both cancer and endothelial cells at the same drug concentration. Careful optimization of drug scheduling and dosages will be required to maximize antitumor responses with metronomic approaches. © 2009 UICC     

Trimodal cancer treatment: beneficial effects of combined antiangiogenesis, radiation, and chemotherapy

It has been suggested that chemotherapy and radiotherapy could favorably be combined with antiangiogenesis in dual anticancer strategy combinations. Here we investigate the effects of a trimodal strategy consisting of all three therapy approaches administered concurrently. We found that in vitro and in vivo, the antiendothelial and antitumor effects of the triple therapy combination consisting of SU11657 (a multitargeted small molecule inhibitor of vascular endothelial growth factor and platelet-derived growth factor receptor tyrosine kinases), Pemetrexed (a multitargeted folate antimetabolite), and ionizing radiation were superior to all single and dual combinations. The superior effects in human umbilical vein endothelial cells and tumor cells (A431) were evident in cell proliferation, migration, tube formation, clonogenic survival, and apoptosis assays (sub-G1 and caspase-3 assessment). Exploring potential effects on cell survival signaling, we found that radiation and chemotherapy induced endothelial cell Akt phosphorylation, but SU11657 could attenuate this process in vitro and in vivo in A431 human tumor xenografts growing s.c. on BALB/c nu/nu mice. Triple therapy further decreased tumor cell proliferation (Ki-67 index) and vessel count (CD31 staining), and induced greater tumor growth delay versus all other therapy regimens without increasing apparent toxicity. When testing different treatment schedules for the A431 tumor, we found that the regimen with radiotherapy (7.5 Gy single dose), given after the institution of SU11657 treatment, was more effective than radiotherapy preceding SU11657 treatment. Accordingly, we found that SU11657 markedly reduced intratumoral interstitial fluid pressure from 8.8 +/- 2.6 to 4.2 +/- 1.5 mm Hg after 1 day. Likewise, quantitative T2-weighed magnetic resonance imaging measurements showed that SU11657-treated mice had reduced intratumoral edema. Our data indicates that inhibition of Akt signaling by antiangiogenic treatment with SU11657 may result in: (a) normalization of tumor blood vessels that cause prerequisite physiologic conditions for subsequent radio/chemotherapy, and (b) direct resensitization of endothelial cells to radio/chemotherapy. We conclude that trimodal cancer therapy combining antiangiogenesis, chemotherapy, and radiotherapy has beneficial molecular and physiologic effects to emerge as a clinically relevant antitumor strategy.     

Experimental characterization of recurrent ovarian immature teratoma cells after optimal surgery

Minimal optimal surgery without chemotherapy is often performed for patients with ovarian immature teratoma, which frequently occurs in young women who hope for future pregnancies. If tumors recur after the operation, anticancer drug chemotherapy is often administered, although few studies have highlighted differences between the recurrent and the primary tumor cells. Therefore, we have established experimental animal models of recurrent ovarian immature teratoma cells after optimal surgery and characterized the anticancer drug sensitivity and antigenicity of the recurrent tumors. Surgically-excised tumor cells of a grade II ovarian immature teratoma were cultured in vitro and transplanted into nude mice to establish stable cell lines. Differential drug sensitivity and antigenicity of the tumor cells were compared between the primary and the nude mouse tumors. Nude mouse tumor cells showed a normal 46XX karyotype. Cultured primary cells showed a remarkably high sensitivity to paclitaxel, docetaxel, adriamycin and pirarubicin, compared to peritoneal cancer cells obtained from a patient with ovarian adenocarcinomatous peritonitis. The drug sensitivity of teratoma cells to 5-fluorouracil, bleomycin or peplomycin was also significantly higher. However, there was no significant difference in sensitivity to platinum drugs between the primary teratoma and the peritoneal adenocarcinoma cells. As for nude mouse tumor cells, sensitivity to 12 anticancer drugs was significantly lower than that of the primary tumor cells, while there was little difference in sensitivity to carboplatin or peplomycin between the primary and nude mouse tumor cells. Flow cytometry showed that the expression of smooth muscle actin (SMA) significantly decreased in nude mouse tumor cells when compared to cultured primary cells. In conclusion, ovarian immature teratomas with normal karyotypes have a malignant potential to recur after minimal surgery. During nude mouse transplantation, SMA-overexpressing cells appeared to be selectively excluded and nude mouse tumor cells were less sensitive to the majority of anticancer drugs than the primary tumor cells. These results indicate that after optimal surgery for ovarian immature teratoma, recurrent cells can be more resistant to anticancer drugs than the primary tumors. Therefore, it is likely that adjuvant chemotherapy lowers the risk of ovarian immature teratomas recurring after optimal surgery. BEP and PBV regimens are frequently given to teratoma patients. However, paclitaxel/carboplatin or docetaxel/carboplatin, which are the most effective chemotherapy treatments for epithelial ovarian cancer patients, are considered to be an alternative regimen, especially in the prevention of reproductive toxicity.     

抗肿瘤血管生成靶向治疗进展

血管生成是肿瘤生长和转移的关键。抗血管生成是一种癌策略,其目标是抗为活跃增殖的肿瘤细胞提供氧气和营养的新生血管。通过阻断新血管的生成抑制癌症的生长和转移。目前,最确定的抑制肿瘤血管生成的方法是阻断血管内皮生长因子（vascular endothelial growth factor,VEGF）通路。但最近,一些非VEGF因子如血小板衍生因子（platelet-derived growth factor,PDGF）、成纤维细胞生长因子（fibroblast growth factor,FGF）、肝细胞生长因子（hepatocyte growth factor,HGF）及血管生成素（angiogenin,Ang）等也参与肿瘤血管生成,强调有必要发展药物针对多种促血管生成途径。     

Peptide-mediated targeting to tumor blood vessels of lung cancer for drug delivery

Antiangiogenesis therapies for the treatment of cancers hold the promise of high efficacy and low toxicity. In vivo phage display was used to identify peptides specifically targeting tumor blood vessels. The peptide SP5-52 recognized tumor neovasculature but not normal blood vessels in severe combined immunodeficiency mice bearing human tumors. Synthetic peptide was shown to inhibit the binding of PC5-52 phage particles to the tumor mass in the competitive inhibition assay. Several selected phage clones displayed the consensus motif, proline-serine-proline, and this motif was crucial for peptide binding to the tumor neovasculature. SP5-52 peptides also bound vascular endothelial growth factor-stimulated human umbilical vein endothelial cells and blood vessels of human lung cancer surgical specimens. Furthermore, this targeting phage was shown to home to tumor tissues from eight different types of human tumor xenografts following in vivo phage display experiments. An SP5-52 peptide-linked liposome carrying doxorubicin enhanced the therapeutic efficacy of the drug, markedly decreased tumor blood vessels, and resulted in higher survival rates of human lung and oral cancer-bearing xenograft mice. The current study indicates that ligand-targeted therapy offers improved therapeutic effects over conventional anticancer drug therapy, and that the peptide SP5-52 specifically targets tumor neovasculature and is a good candidate for targeted drug delivery to solid tumors.     

Combretastatin family member OXI4503 induces tumor vascular collapse through the induction of endothelial apoptosis

The mechanism of tumor cell killing by OXI4503 was investigated by studying vascular functional and morphological changes post drug administration. SCID mice bearing MHEC5-T hemangioendothelioma were given a single dose of OXI4503 at 100 mg/kg. Tumor blood flow, measured by microsphere fluorescence, was reduced by 50% at 1 hr, and reached a maximum level 6-24 hr post drug treatment. Tumor vascular permeability, measured by Evan's blue and hemoglobin, increased significantly from 3 hr and peaked at 18 hr. The elevated tumor vessel permeability was accompanied by an increase in vascular endothelial growth factor (VEGF) from 1 hr post drug treatment. Immunohistochemical staining for CD31 and laminin showed that tumor blood vessels were affected as early as 3 hr but more prominent from 6 hr. From 12 hr, the vessel structure was completely destroyed. Histopathological and double immunohistochemical staining showed morphological change and induction of apoptosis in endothelial cells at 1-3 hr, followed by tumor cell necrosis from 6-72 hr. There were no statistically significant changes of Evan's blue and hemoglobin contents in liver tissue over the time course. These results suggest that OXI4503 selectively targets tumor blood vessels, and induces blood flow shutdown while it enhances tumor blood vessel permeability. The early induction of endothelial cell apoptosis leads to functional changes of tumor blood vessels and finally to the collapse of tumor vasculature, resulting in massive tumor cell necrosis. The time course of the tumor vascular response observed with OXI4503 treatment supports this drug for development as a stand alone therapy, and also lends support for the use of the drug in combination with other cancer therapies.     

Immunohistochemical study of VEGF,angiopoietin 2 and their receptors in the neovascularization following microinjection of C6 glioma cells into rat brain

BACKGROUND: Recent papers suggest that two angiogenic factors (angiopoietin 2 and vascular endothelial growth factor) cooperate in tumoral angiogenesis to support the growing tumor. The purpose of the present work was to demonstrate the existence of such cooperation in a longitudinal study of a brain tumor model during tumor growth by means of immunohistochemistry. MATERIALS AND METHODS: The study was performed on 31 rats bearing C6 glioma. At different stages of tumor growth, the histological aspects were described and sections were immunostained for VEGF, Ang-2 and their receptors VEGFR-1, VEGFR-2 and Tie-2. Immunostaining was semi-quantitatively analyzed and the localization of immunostained cells was reported. RESULTS: Ang-2 and Tie-2 were detected in the endothelial cells of vessels surrounded by tumor cells, occuring early in our study, with immunostaining taking place from day 4 to day 24. Immunostaining with VEGF (on tumoral cells) and VEGFR-2 (on endothelial cells) was present after 8 days of tumor growth. A clear increase of vessel density can be observed at the periphery of the tumors after 16 days of tumor growth. At that time, areas of necrosis were present in the tumor with concomitant VEGF and Ang-2 expression. CONCLUSION: The present study demonstrated cooperation between the early effect of Ang-2 and the secondary effect of VEGF to elaborate new vessels in a longitudinal study of experimental brain tumors. This study is favorable to the new model of tumor angiogenesis, with successive vessel cooption, regression and growth mediated by angiopoietins and VEGF.     

Dynamic Contrast-Enhanced Magnetic Resonance Imaging of Vascular Changes Induced by Sunitinib in Papillary Renal Cell Carcinoma Xenograft Tumors

To investigate further the antiangiogenic potential of sunitinib for renal cell carcinoma (RCC) treatment, its effects on tumor vasculature were monitored by dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) using an orthotopic KCI-18 model of human RCC xenografts in nude mice. Tumor-bearing mice were treated with various doses of sunitinib, and vascular changes were assessed by DCE-MRI and histologic studies. Sunitinib induced dose-dependent vascular changes, which were observed both in kidney tumors and in normal kidneys by DCE-MRI. A dosage of 10 mg/kg per day caused mild changes in Gd uptake and clearance kinetics in kidney tumors. A dosage of 40 mg/kg per day induced increased vascular tumor permeability with Gd retention, probably resulting from the destruction of tumor vasculature, and also caused vascular alterations of normal vessels. However, sunitinib at 20 mg/kg per day caused increased tumor perfusion and decreased vascular permeability associated with thinning and regularization of tumor vessels while mildly affecting normal vessels as confirmed by histologic diagnosis. Alterations in tumor vasculature resulted in a significant inhibition of KCI-18 RCC tumor growth at sunitinib dosages of 20 and 40 mg/kg per day. Sunitinib also exerted a direct cytotoxic effect in KCI-18 cells in vitro. KCI-18 cells and tumors expressed vascular endothelial growth factor receptor 2 and platelet-derived growth factor receptor β molecular targets of sunitinib that were modulated by the drug treatment. These data suggest that a sunitinib dosage of 20 mg/kg per day, which inhibits RCC tumor growth and regularizes tumor vessels with milder effects on normal vessels, could be used to improve blood flow for combination with chemotherapy. These studies emphasize the clinical potential of DCE-MRI in selecting the dose and schedule of antiangiogenic compounds.     

Effect of treatment schedule on antitumor activity of glycolate-0,0'-diammineplatinum(II), a new platinum derivative: comparison with cis-diamminedichloroplatinum(II)

The effect of treatment schedule on the antitumor activity of a new platinum derivative, glycolate-0,0'-diammineplatinum (II) (254S) compared with cis- diamminedichloroplatinum (II) (CDDP) was investigated using ascites L1210 leukemia and solid Lewis lung carcinoma. The drugs were given i.p. by three treatments: as a single injection, as three injections at 4 day intervals and as 9 daily continuous injections. 254S produced a marked increase of lifespan in mice by all three treatment schedules (about 100% ILS), although the consecutive treatment of 254S needed more total doses against L1210 leukemia. The antitumor activity of 254S was, however, inferior to that of CDDP. Moreover, 254S did not show certain dependence on treatment schedule, while CDDP was rather dependent on treatment schedule. The single injection (day 1) of CDDP exhibited the most potent antitumor activity. On the other hand, although the single injection of CDDP showed more host toxicity than the other treatment schedules and the consecutive treatment needed more total doses, neither drug showed any definite schedule dependency against Lewis lung carcinoma. Moreover, the tumor growth inhibitory activity of 254S was almost the same as or slightly superior to that of CDDP. Both drugs produced about 70% (days 14-17) and 50% (day 20) tumor weight inhibitions against early and advanced Lewis lung carcinoma, respectively.     

Experimental studies on subrenal capsule assay using cyclosporin A treated mice--the optimal treatment schedules of CsA and anticancer agents (mitomycin C and 5-fluorouracil)

We studied fundamentally subrenal capsule assay, using human tumor specimens (breast, gastric and colon cancers) serially transplanted in nude mice. When cancer anticancer agents such as mitomycin C (MMC) and 5-fluorouracil (5-FU) were injected into immunocompetent mice treated with various dosages of cyclosporin A (CsA) after tumor implantation, optimal schedule of each drug was examined on the points of effects and toxicity against host mice. The following results were obtained. Control groups were set up as immunocompetent mice which treated daily with 60 mg/kg CsA from day 1 after tumor implantation. Optimal treatment schedule was judged as MMC 3 mg/kg i.v. injection on day 1 following by daily 60 mg/kg CsA treatment, and 5-FU was injected 25 mg/kg subcutaneous injection every day from day 1 without CsA treatment, each schedule showed an appropriate anti-tumor activity profiles against implanted tumor xenografts, and had less toxicity to the hosts.     

Vascular endothelial growth factor as a target for anticancer therapy

The development of a vascular supply is a critical factor in the growth and metastatic spread of malignant tumors. Of the multitude of growth factors that regulate physiological and pathological angiogenesis, vascular endothelial growth factor (VEGF) is believed to be the most important. There is evidence that overexpression of VEGF is correlated with an adverse prognosis, at least in some tumors. Tumor-expressed VEGF is particularly attractive as a target for anticancer therapy because its angiogenesis-promoting activity is at the level of the endothelial cell and, compared with agents that directly target tumor cells, tumor penetration is less critical for VEGF inhibitors. Moreover, recent work has shown that inhibiting tumor angiogenesis increases the effectiveness of coadministered chemotherapy and radiotherapy. This suggests that drugs that target VEGF or its receptors can be combined with traditional treatment modalities to ensure maximum effectiveness. A variety of agents aimed at blocking VEGF or its receptor-signaling system are currently being developed for the treatment of cancer. Of these, bevacizumab, a humanized monoclonal antibody directed at VEGF, is the most advanced in clinical development and has shown promising results in clinical trials.     

Functional-characterization of developing tumor vascular system and drug delivery (review)

This review summarizes our recent experiments on the process of tumor vascularization and character of tumor vessels. By vitalscopic observation with transparent chambers in rats, we found that the sites where tumor vessels originated were usually terminal portions of terminal arterioles and that an intricate tumor vascular network was constructed from incorporated preexisting vessels and newly formed vessels by three different modes, i.e., sprouting, cross-connecting and splitting. Observation and hydrogen clearance studies showed that tumor blood flow changed remarkably during the development of the tumor vascular network. At an early stage of tumor growth, there were some regions of high flow in the tumor. At an advanced stage, however, there was a rapid increase in low-flow or no-flow areas which were resistant to access of anticancer drugs and oxygen. Angiotensin II-induced hypertension produced a several-fold increase in tumor blood flow without increasing tissue blood flow of normal tissues. These good conditions for drug delivery to tumor tissue are able to enhance therapeutic effects of chemotherapy, irradiation, antibody and photodynamic therapy.     

Dosage regimen optimization in cancer chemotherapy using a mathematical model

In cancer chemotherapy, it is important to design treatment strategies that ensure a desired rate of tumor cell kill without unacceptable toxicity. To optimize treatment, we used a mathematical model describing the pharmacokinetics of anticancer drugs, antitumor efficacy, and drug toxicity. This model was associated with constraints on the allowed plasma concentrations, drug exposure, and leukopenia. Given a schedule of drug administrations, the mathematical model optimized the drug doses that could minimize the tumor burden while limiting toxicity on the white blood cells. Simulation suggests that the optimal drug administration is an initial high dose chemotherapy up to saturation of constraints associated with normal cell toxicity followed by a maintenance continuous infusion at a moderate rate. Data related to etoposide investigations were next used in a feasibility study. Simulations made with the usual clinical protocols and optimized protocols revealed that model-based optimal drug doses lead to greater cytoreduction. Also, examples showed how to use this new approach for the dose ranging problem and they evaluated the sensitivity of the optimized protocols with respect to the clinical constraints.