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Background Effective chemotherapy rapidly reduces the spin--lattice relaxation of water protons (T1) in solid tumours and this change (ΔT1) often precedes and strongly correlates with the eventual change in tumour volume (TVol). To understand the biological nature of ΔT1, we have performed studies in vivo and ex vivo with the allosteric mTOR inhibitor, everolimus. Mice bearing RIF-1 tumours were studied by magnetic resonance imaging (MRI) to determine TVol and T1, and MR spectroscopy (MRS) to determine levels of the proliferation marker choline and levels of lipid apoptosis markers, prior to and 5 days (endpoint) after daily treatment with vehicle or everolimus (10 mg/kg). At the endpoint, tumours were ablated and an entire section analysed for cellular and necrotic quantification and staining for the proliferation antigen Ki67 and cleaved-caspase-3 as a measure of apoptosis. The number of blood-vessels (BV) was evaluated by CD31 staining. Mice bearing B16/BL6 melanoma tumours were studied by MRI to determine T1 under similar everolimus treatment. At the endpoint, cell bioluminescence of the tumours was measured ex vivo. Results Everolimus blocked RIF-1 tumour growth and significantly reduced tumour T1 and total choline (Cho) levels, and increased polyunsaturated fatty-acids which are markers of apoptosis. Immunohistochemistry showed that everolimus reduced the%Ki67+ cells but did not affect caspase-3 apoptosis, necrosis, BV-number or cell density. The change in T1 (ΔT1) correlated strongly with the changes in TVol and Cho and%Ki67+. In B16/BL6 tumours, everolimus also decreased T 1 and this correlated with cell bioluminescence; another marker of cell viability. Receiver-operating-characteristic curves (ROC) for everolimus on RIF-1 tumours showed that ΔT1 had very high levels of sensitivity and specificity (ROCAUC = 0.84) and this was confirmed for the cytotoxic patupilone in the same tumour model (ROCAUC = 0.97). Conclusion These studies suggest that ΔT1 is not a measure of cell density but reflects the decreased number of remaining viable and proliferating tumour cells due to perhaps cell and tissue destruction releasing proteins and/or metals that cause T1 relaxation. ΔT1 is a highly sensitive and specific predictor of response. This MRI method provides the opportunity to stratify a patient population during tumour therapy in the clinic. [ABSTRACT FROM AUTHOR]

Comparative pharmacokinetic (PK) analysis of the mTOR inhibitor RAD001 (everolimus) in rats and mice. Blood cell partitioning, plasma protein binding and PK parameters of RAD001 in blood and tissues (including brain) of both mice and rats were determined. PK modeling predicted plasma/blood and tumor levels from a variety of regimens and these were compared with the known human PK profile. DCE-MRI was used to compare tumor vascularity between mice and rats. Estimation of IC50 values in vitro and ED50 values in vivo were used to provide an indication of anti-tumor activity. The PK properties of RAD001 differed between mice and rats, including erythrocyte partitioning, plasma protein binding, plasma/blood t1/2, oral bioavailability, volume of distribution, tissue/tumor penetration and elimination. Modeling of tumor and blood/plasma PK suggested that in mice, multiple daily administrations result in a ~2-fold increase in tumor levels of RAD001 at steady state, whereas in rats, a ~7.9-fold increase would occur. Weekly high-dose regimens were predicted not to facilitate tumor accumulation in either species. Total tumor levels of RAD001 were four- to eight-fold greater in rats than in mice. Rat tumors had a >2-fold greater plasma content and permeability compared to mouse tumors, which could contribute to differences in tumor drug uptake. Maximal antitumor effects (T/C of 0.04–0.35) were observed in both species after daily administration with similar Cmax and AUC values of unbound (free) RAD001. These free levels of RAD001 are exceeded in serum from cancer patients receiving clinically beneficial daily regimens. In rodents, brain penetration of RAD001 was poor, but was dose-dependent and showed over-proportional uptake in rats with a longer t1/2 compared to the systemic circulation. The PK of RAD001 differed between mice and rats, with rats having a PK profile closer to that of humans. High intermittent doses of RAD001 may be more appropriate for treatment of brain tumors. [ABSTRACT FROM AUTHOR]

Patupilone is a microtubule stabilizer (MTS) currently in clinical development. Here, we evaluate the anti-cancer activity in vitro and in vivo in comparison to paclitaxel and describe the pharmacokinetics (PK) of patupilone in tumor-bearing nude mice and rats. The potency in vitro of patupilone and two other MTS, paclitaxel and ixabepilone, was determined using human colon carcinoma cell lines with low (HCT-116, HT-29, RKO) and high (HCT-15) P-glycoprotein expression (P-gp), as well as two multi-drug resistance (MDR) model cell pairs, MCF7/ADR and KB-8511 cells and their respective drug-sensitive parental counterparts. The PK of patupilone was investigated in nude mice bearing HCT-15 or HT-29 xenografts and in rats bearing s.c. pancreatic CA20498 tumors or A15 glioma tumors. Anti-cancer activity in vivo was compared to that of paclitaxel using three different human tumor colon models. The retention and efficacy of patupilone was compared in small and large HT-29 xenografts whose vascularity was determined by non-invasive magnetic resonance imaging. Patupilone was highly potent in vitro against four different colon carcinoma cell lines including those showing multi-drug-resistance. In contrast, paclitaxel and ixabepilone displayed significantly reduced activity with markedly increased resistance factors. In both rats and mice, a single i.v. bolus injection of patupilone (1.5–4 mg/kg) rapidly distributed from plasma to all tissues and was slowly eliminated from muscle, liver and small intestine, but showed longer retention in tumor and brain with no apparent elimination over 24 h. Patupilone showed significant activity against three human colon tumor models in vivo, unlike paclitaxel, which only had activity against low P-gp expressing tumors. In HT-29 tumors, patupilone activity and retention were independent of tumor size, blood volume and flow. The high potency of patupilone, which is not affected by P-gp expression either in vitro or in vivo, and favorable PK, independent of tumor vascularity, suggest that it should show significant activity in colorectal cancer and in other indications where high P-gp expression may compromise taxane activity. [ABSTRACT FROM AUTHOR]

Background: Effective chemotherapy rapidly reduces the spin-lattice relaxation of water protons (T1) in solid tumours and this change (ΔT1) often precedes and strongly correlates with the eventual change in tumour volume (TVol). To understand the biological nature of ΔT1, we have performed studies in vivo and ex vivo with the allosteric mTOR inhibitor, everolimus.Methods: Mice bearing RIF-1 tumours were studied by magnetic resonance imaging (MRI) to determine TVol and T1, and MR spectroscopy (MRS) to determine levels of the proliferation marker choline and levels of lipid apoptosis markers, prior to and 5 days (endpoint) after daily treatment with vehicle or everolimus (10 mg/kg). At the endpoint, tumours were ablated and an entire section analysed for cellular and necrotic quantification and staining for the proliferation antigen Ki67 and cleaved-caspase-3 as a measure of apoptosis. The number of blood-vessels (BV) was evaluated by CD31 staining. Mice bearing B16/BL6 melanoma tumours were studied by MRI to determine T1 under similar everolimus treatment. At the endpoint, cell bioluminescence of the tumours was measured ex vivo.Results: Everolimus blocked RIF-1 tumour growth and significantly reduced tumour T1 and total choline (Cho) levels, and increased polyunsaturated fatty-acids which are markers of apoptosis. Immunohistochemistry showed that everolimus reduced the %Ki67+ cells but did not affect caspase-3 apoptosis, necrosis, BV-number or cell density. The change in T1 (ΔT1) correlated strongly with the changes in TVol and Cho and %Ki67+. In B16/BL6 tumours, everolimus also decreased T1 and this correlated with cell bioluminescence; another marker of cell viability. Receiver-operating-characteristic curves (ROC) for everolimus on RIF-1 tumours showed that ΔT1 had very high levels of sensitivity and specificity (ROCAUC = 0.84) and this was confirmed for the cytotoxic patupilone in the same tumour model (ROCAUC = 0.97).Conclusion: These studies suggest that ΔT1 is not a measure of cell density but reflects the decreased number of remaining viable and proliferating tumour cells due to perhaps cell and tissue destruction releasing proteins and/or metals that cause T1 relaxation. ΔT1 is a highly sensitive and specific predictor of response. This MRI method provides the opportunity to stratify a patient population during tumour therapy in the clinic. [ABSTRACT FROM AUTHOR]

Presents a study that examined pharmacokinetics and pharmacodynamics of fluorinated drugs through the use of magnetic resonance spectroscopy. Information on ifosfamide; Barriers that limit access of drugs to many parts of the tumor; Factors that have been used to increase tumor blood flow.

Solid tumors have a raised interstitial fluid pressure (IFP) due to high vessel permeability, low lymphatic drainage, poor perfusion, and high cell density around the blood vessels. To investigate tumor IFP as an early-response biomarker, we have tested the effect of seven anticancer chemotherapeutics including cytotoxics and targeted cytostatics in 13 experimental tumor models. IFP was recorded with the wick-in-needle method. Models were either ectopic or orthotopic and included mouse and rat syngeneic as well as human xenografts in nude mice. The mean basal IFP was between 4.4 and 15.2mm Hg; IFP was lowest in human tumor xenografts and highest in rat syngeneic models. Where measured, basal IFP correlated positively with relative tumor blood volume (rTBV) determined by dynamic contrast-enhanced magnetic resonance imaging. Most chemotherapeutics sooner (2 or 3 days) or later (6 or 7 days) lowered tumor IFP significantly, and the cytotoxic patupilone caused the greatest decrease in IFP. In rat mammary orthotopic BN472 tumors, significant drug-induced decreases in IFP and rTBV correlated positively with each other for both patupilone and the cytostatic vatalanib. In the two orthotopic models studied, early decreases in IFP were significantly (P ≤ .005) correlated with late changes in tumor volume. Thus, drug-induced decreases in tumor IFP are an early marker of response to therapy, which could aid clinical development. [ABSTRACT FROM AUTHOR]

Derazantinib (DZB) is an inhibitor of fibroblast growth factor receptors 1-3 (FGFR1-3), with additional activity against colony-stimulating-factor-1 receptor (CSF1R). We have profiled the activity of DZB in gastric cancer (GC) as monotherapy and combined with paclitaxel, and explored means of stratifying patients for treatment. The antiproliferative potency of DZB in vitro was quantified in 90 tumor cell lines and shown to correlate significantly with FGFR expression (<0.01) but not with FGFR DNA copy-number (CN) or FGFR mutations. In four GC cell lines in vitro , little or no synergy was observed with paclitaxel. In athymic nude mice, bearing cell-line derived xenografts (CDX) or patient-derived xenograft (PDX) GC models, DZB efficacy correlated highly significantly with FGFR gene expression ( r2 = 0.58; P = 0.0003; n = 18), but not FGFR mutations or DNA-CN. In FGFR-driven GC models, DZB had comparable efficacy to three other FGFR inhibitors and was more efficacious than paclitaxel. DZB had dose-dependent plasma pharmacokinetics but showed low brain penetration at all doses. GC models (one CDX and six PDX) were tested for sensitivity to the combination of DZB and paclitaxel and characterized by immunohistochemistry. The combination showed synergy (5) or additivity (2), and no antagonism, with synergy significantly associated ( P < 0.05) with higher levels of M2-type macrophages. The association of strong efficacy of the combination in vivo with M2 macrophages, which are known to express CSF1R, and the absence of synergy in vitro is consistent with the tumor microenvironment also being a factor in DZB efficacy and suggests additional means by which DZB could be stratified for cancer treatment in the clinic., (Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.)

Combined radiochemotherapy treatment modalities are in use for many indications and therefore of high interest. Even though a combined modality in clinical use is often driven by pragmatic aspects, mechanistic preclinical-based concepts of interaction are of importance in order to translate and implement an optimal combination and scheduling of two modalities into the clinics. The use of microtubule stabilising agents is a promising strategy for anti-cancer therapy as a part of combined treatment modality with ionising radiation. Traditionally, microtubule targeting agents are classified as cytotoxic chemotherapeutics and are mostly used in a maximally tolerated dose regimen. Apart from direct cytotoxicity and similar to mechanisms of molecular targeting agents, microtubule stabilising agents interfere with multiple cellular processes, which can be exploited as part of combined treatment modalities. Recent preclinical investigations on the combination of ionising radiation and microtubule stabilising agents reveal new mechanistic interactions on the cellular and tumour level and elucidate the supra-additive tumour response observed particularly in vivo. The major focus on the mechanism of interaction was primarily based on radiosensitisation due to cell cycle arrest in the most radiosensitive G2/M-phase of the cell cycle. However, other mechanisms of interaction such as reoxygenation and direct as well as indirect endothelial damage have also been identified. In this review we summarise and allocate additive and synergistic effects induced by the combined treatment of clinically relevant microtubule stabilising agents and ionising radiation along a described radiobiological framework encompassing distinct mechanisms relevant for exploiting the combination of drugs and ionising radiation., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Background: Patients with glioblastoma (GBM) inevitably develop recurrent or progressive disease after initial multimodal treatment and have a median survival of 6-9 months from time of progression. To date, there is no accepted standard treatment for GBM relapse or progression. Patupilone (EPO906) is a novel natural microtubule-stabilizing cytotoxic agent that crosses the blood-brain barrier and has been found to have preclinical activity in glioma models., Methods: This is a single-institution, early-phase I/II trial of GBM patients with tumor progression who qualified for second surgery with the goal of evaluating efficacy and safety of the single-agent patupilone (10 mg/m(2), every 3 weeks). Patients received patupilone 1 week prior to second surgery and every 3 weeks thereafter until tumor progression or toxicity. Primary end points were progression-free survival (PFS) and overall survival (OS) at 6 months as well as patupilone concentration in tumor tissue. Secondary end points were toxicity, patupilone concentration in plasma and translational analyses for predictive biomarkers., Results: Nine patients with a mean age of 54.6 ± 8.6 years were recruited between June 2008 and April 2010. Median survival and 1-year OS after second surgery were 11 months (95% CI, 5-17 months) and 45% (95% CI, 14-76), respectively. Median PFS was 1.5 months (95% CI, 1.3-1.7 months) and PFS6 was 22% (95% CI, 0-46), with 2 patients remaining recurrence-free at 9.75 and 22 months. At the time of surgery, the concentration of patupilone in tumor tissue was 30 times higher than in the plasma. Tumor response was not predictable by the tested biomarkers. Treatment was generally well tolerated with no hematological, but cumulative, though reversible sensory neuropathy grade ≤3 was seen in 2 patients (22%) at 8 months and grade 4 diarrhea in the 2nd patient (11%). Non-patupilone-related peri-operative complications occurred in 2 patients resulting in discontinuation of patupilone therapy. There were no neurocognitive changes 3 months after surgery compared to baseline., Conclusions: In recurrent GBM, patupilone can be given safely pre- and postoperatively. The drug accumulates in the tumor tissue. The treatment results in long-term PFS in some patients. Patupilone represents a valuable novel compound which deserves further evaluation in combination with radiation therapy in patients with GBM., (Copyright © 2012 S. Karger AG, Basel.)

The use of microtubule stabilizing agents (MSAs) is a promising strategy for anti-cancer therapy alone and as part of combined treatment modalities with ionizing radiation. However MSA-provoked molecular and cellular processes including the regulation of intercellular, paracrine signaling pathways are far from clear. Here we investigated the interference of the novel, clinically relevant MSA patupilone (epothilone B) with the tumor-cell derived vascular endothelial growth factor (VEGF), which is most relevant for tumor angiogenesis. Low-dose, sub-nanomolar concentrations of patupilone specifically reduced hypoxia-driven stabilization of the transcription factor HIF-1α in the patupilone-sensitive lung adenocarcinoma cell line A549, but not in the mutant derivative cell line A549.EpoB40. Patupilone further reduced hypoxia-induced VEGF expression and secretion but only in the A549 wildtype cell line. In the wildtype cell line, ionizing radiation alone induced hypoxia-dependent VEGF-expression but a strong dominant counteracting effect of patupilone was always observed when ionizing radiation was combined with patupilone, on the level of HIF-1α protein stability, VEGF-expression and VEGF-secretion. These results demonstrate that patupilone and ionizing radiation dysregulate hypoxia-induced stress responses, which might contribute to the potency of this promising, combined treatment modality., (Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.)

Sorafenib targets the Raf/mitogen-activated protein kinase, VEGF, and platelet-derived growth factor pathways and prolongs survival patients in advanced hepatocellular carcinoma (HCC). Everolimus inhibits the mammalian target of rapamycin, a kinase overactive in HCC. To investigate whether the antitumor effects of these agents are additive, we compared a combined and sequential treatment regimen of everolimus and sorafenib with monotherapy. After hepatic implantation of Morris Hepatoma (MH) cells, rats were randomly allocated to everolimus (5 mg/kg, 2×/week), sorafenib (7.5 mg/kg/d), combined everolimus and sorafenib, sequential sorafenib (2 weeks) then everolimus (3 weeks), or control groups. MRI quantified tumor volumes. Erk1/2, 4E-BP1, and their phosphorylated forms were quantified by immunoblotting. Angiogenesis was assessed in vitro by aortic ring and tube formation assays, and in vivo with Vegf-a mRNA and vascular casts. After 35 days, tumor volumes were reduced by 60%, 85%, and 55%, relative to controls, in everolimus, the combination, and sequential groups, respectively (P < 0.01). Survival was longest in the combination group (P < 0.001). Phosphorylation of 4E-BP1 and Erk1/2 decreased after everolimus and sorafenib, respectively. Angiogenesis decreased after all treatments (P < 0.05), although sorafenib increased Vegf-a mRNA in liver tumors. Vessel sprouting was abundant in control tumors, lower after sorafenib, and absent after the combination. Intussusceptive angiogenic transluminal pillars failed to coalesce after the combination. Combined treatment with everolimus and sorafenib exerts a stronger antitumoral effect on MH tumors than monotherapy. Everolimus retains antitumoral properties when administered sequentially after sorafenib. This supports the clinical use of everolimus in HCC, both in combination with sorafenib or after sorafenib.

The aim was to determine the potential of the allosteric mammalian target of rapamycin inhibitor, everolimus, to act in combination with cytotoxic anticancer compounds in vitro and in vivo. A concomitant combination in vitro showed no evidence of antagonism, but enhanced the antiproliferative effects (additive to synergistic) with cisplatin, doxorubicin, 5-fluorouracil, gemcitabine, paclitaxel, and patupilone. Everolimus (1-5 mg/kg/d orally) was evaluated for antitumor activity in vivo alone or in combination with suboptimal cytotoxic doses using athymic nude mice bearing subcutaneous human H-596 lung, KB-31 cervical, or HCT-116 colon tumor xenografts. Everolimus monotherapy was very well tolerated and caused inhibition of tumor growth, rather than regression, and this was associated with a dose-dependent decline in tumor pS6 levels, a key downstream protein of mammalian target of rapamycin. At the doses used, the cytotoxics inhibited tumor growth and caused tolerable body-weight loss. Concomitant combinations of cisplatin, doxorubicin, paclitaxel, or patupilone with everolimus produced cooperative antitumor effects, in some cases producing regressions without clinically significant increases in toxicity. In contrast, combinations with gemcitabine and 5-fluorouracil were less well tolerated. Alternative administration schedules were tested for cisplatin, gemcitabine, or paclitaxel combined with everolimus: these did not dramatically affect cisplatin or gemcitabine activity or tolerability but were antagonistic for paclitaxel. Everolimus showed promising maintenance activity after treatment with doxorubicin or paclitaxel ceased. Overall, the results confirm that everolimus is an effective, well-tolerated suppressor of experimental human tumor growth, and although it did not show strong potentiation of efficacy, antitumor activity in vivo was increased without marked increases in toxicity, supporting clinical use of everolimus as a partner for conventional cytotoxics.

Purpose: Identification of a generic response biomarker by comparison of chemotherapeutics with different action mechanisms on several noninvasive biomarkers in experimental tumor models., Experimental Design: The spin-lattice relaxation time of water protons (T(1)) was quantified using an inversion recovery-TrueFISP magnetic resonance imaging method in eight different experimental tumor models before and after treatment at several different time points with five different chemotherapeutics. Effects on T(1) were compared with other minimally invasive biomarkers including vascular parameters, apparent diffusion coefficient, and interstitial fluid pressure, and were correlated with efficacy at the endpoint and histologic parameters., Results: In all cases, successful chemotherapy significantly lowered tumor T(1) compared with vehicle and the fractional change in T(1) (DeltaT(1)) correlated with the eventual change in tumor size (range: r(2) = 0.21, P < 0.05 to r(2) = 0.73, P < 0.0001), except for models specifically resistant to that drug. In RIF-1 tumors, interstitial fluid pressure was decreased, but apparent diffusion coefficient and permeability increased in response to the microtubule stabilizer patupilone and 5-fluorouracil. Although DeltaT(1) was small (maximum of -20%), the variability was very low (5%) compared with other magnetic resonance imaging methods (24-48%). Analyses ex vivo showed unchanged necrosis, increased apoptosis, and decreased %Ki67 and total choline, but only Ki67 and choline correlated with DeltaT(1). Correlation of Ki67 and DeltaT(1) were observed in other models using patupilone, paclitaxel, a VEGF-R inhibitor, and the mammalian target of rapamycin inhibitor everolimus., Conclusions: These results suggest that a decrease in tumor T(1) reflects hypocellularity and is a generic marker of response. The speed and robustness of the method should facilitate its use in clinical trials.

Purpose: Comparison of the antiangiogenic/vascular properties of the oral mammalian target of rapamycin (mTOR) inhibitor RAD001 (everolimus) and the vascular endothelial growth factor receptor (VEGFR) inhibitor vatalanib (PTK/ZK)., Experimental Design: Antiproliferative activity against various tumor histotypes and downstream effects on the mTOR pathway were measured in vitro. In vivo, antitumor activity, plasma, and tumor RAD001 levels were measured. Activity in several different angiogenic/vascular assays in vitro and in vivo was assessed and compared with PTK/ZK., Results: RAD001 inhibited proliferation in vitro (IC50 values<1 nmol/L to >1 micromol/L), and in sensitive and insensitive tumor cells, pS6 kinase and 4E-BP1 were inhibited. Activity in vitro did not correlate with activity in vivo and significant responses were seen in tumors with IC50 values>10-fold higher than tumor RAD001 concentrations. In vitro, RAD001 inhibited the proliferation of VEGF-stimulated and fibroblast growth factor-stimulated human endothelial cells but not dermal fibroblasts and impaired VEGF release from both sensitive and insensitive tumor cells but did not inhibit migration of human endothelial cells. In vivo, in tumor models derived from either sensitive or insensitive cells, RAD001 reduced Tie-2 levels, the amount of mature and immature vessels, total plasma, and tumor VEGF. RAD001 did not affect blood vessel leakiness in normal vasculature acutely exposed to VEGF nor did it affect tumor vascular permeability (Ktrans) as measured by dynamic contrast-enhanced magnetic resonance imaging. However, the pan-VEGFR inhibitor PTK/ZK inhibited endothelial cell migration and vascular permeability but had less effect on mature vessels compared with RAD001., Conclusions: VEGFR and mTOR inhibitors show similar but also distinct effects on tumor vascular biology, which has implications for their clinical activity alone or in combination.

Purpose: The combined treatment modality of ionizing radiation (IR) and the clinically relevant microtubule-stabilizing compound patupilone (epothilone B, EPO906) is a promising approach for anticancer therapy. Here, we investigated the role of the tumor microenvironment for the supra-additive in vivo response in tumor xenografts derived from patupilone-sensitive and patupilone-resistant non-small cell lung cancer cells., Experimental Design: The treatment response to a combined regimen of patupilone and IR was investigated in vitro and in tumor xenografts derived from wild-type A549 and A549.EpoB40 cells, which are resistant to patupilone due to a beta-tubulin mutation., Results: In both A549 and A549.EpoB40 cells, proliferative activity and clonogenicity were reduced in response to IR, whereas patupilone, as expected, inhibited proliferation of the mutant cell line with reduced potency. Combined treatment with patupilone and IR induced a cytotoxic effect in vitro in an additive way in A549 cells but not in the tubulin-mutated, patupilone-resistant A549.EpoB40 cells. A supra-additive tumor growth delay was induced by combined treatment in xenografts derived from A549 cells but not in xenografts derived from A549.EpoB40 cells. Histologic analysis revealed a significant decrease in tumor cell proliferation (Ki-67) and microvessel density and a treatment-dependent change of tumor hypoxia in A549 but not A549.EpoB40 xenografts., Conclusions: Using a genetically defined patupilone-sensitive and patupilone-resistant tumor model, we here showed that the major cytotoxic effect of the combined treatment modality of IR and patupilone is directed against the tumor cell compartment. The induced antiangiogenic effect derives indirectly from the tumor cell.

Dysregulated angiogenesis and high tumor vasculature permeability, two vascular endothelial growth factor (VEGF)-mediated processes and hallmarks of human tumors, are in part phosphatidylinositol 3-kinase (PI3K) dependent. NVP-BEZ235, a dual PI3K/mammalian target of rapamycin (mTOR) inhibitor, was found to potently inhibit VEGF-induced cell proliferation and survival in vitro and VEGF-induced angiogenesis in vivo as shown with s.c. VEGF-impregnated agar chambers. Moreover, the compound strongly inhibited microvessel permeability both in normal tissue and in BN472 mammary carcinoma grown orthotopically in syngeneic rats. Similarly, tumor interstitial fluid pressure, a phenomenon that is also dependent of tumor permeability, was significantly reduced by NVP-BEZ235 in a dose-dependent manner on p.o. administration. Because RAD001, a specific mTOR allosteric inhibitor, was ineffective in the preceding experiments, we concluded that the effects observed for NVP-BEZ235 are in part driven by PI3K target modulation. Hence, tumor vasculature reduction was correlated with full blockade of endothelial nitric oxide (NO) synthase, a PI3K/Akt-dependent but mTORC1-independent effector involved in tumor permeability through NO production. In the BN472 tumor model, early reduction of permeability, as detected by K(trans) quantification using the dynamic contrast-enhanced magnetic resonance imaging contrasting agent P792 (Vistarem), was found to be a predictive marker for late-stage antitumor activity by NVP-BEZ235.

Purpose: To characterize tumor vascularization by dynamic-contrast enhanced (DCE) MRI using low and medium molecular weight paramagnetic contrast agents (CA) and inversion recovery (IR) true fast imaging with steady state precession (TrueFISP) in tumor-bearing rats and mice., Materials and Methods: T(1) mapping was performed using IR True FISP in phantoms and in vivo at 4.7 T and validated with a segmented IR gradient-echo (IR GE) method. CA concentration in DCE-MRI studies in vivo was calculated from time-series T(1) maps using the CAs GdDOTA and P792 (low and medium molecular weight, respectively). Standard vascular input functions (VIFs) were measured in the jugular veins and were used for modeling of the CA kinetics with a two-compartment model. In rat breast tumors, vascular permeability (transfer constant K(trans)), fractional plasma volume v(p), and fractional leakage space v(e) were quantified and parametric maps were generated., Results: The IR TrueFISP T(1) was slightly underestimated in phantoms and overestimated in vivo (10%) with respect to IR GE. VIFs showed only small interindividual variation. Mean K(trans) values were 0.062 +/- 0.017 min(-1) for GdDOTA and 0.015 +/- 0.005 min(-1) for P792 (N = 12). Mean v(e) and v(p) values were 0.15 +/- 0.04 (0.09 +/- 0.03) and 0.04 +/- 0.01 (0.03 +/- 0.01) for GdDOTA (P792)., Conclusion: DCE-MRI with IR TrueFISP provided absolute values for K(trans), v(p), and v(e). Direct comparison between GdDOTA and P792 revealed significant differences in the VIF, model-fit-quality, permeability, leakage space, and plasma volume. The larger molecular weight CA P792 appears to be better for measuring tumor vascular parameters.

Purpose: Evaluation of vascular disruptive activity in orthotopic models as potential surrogate biomarkers of tumor response to the microtubule-stabilizing agent patupilone., Experimental Design: Mice bearing metastatic B16/BL6 melanoma and rats bearing mammary BN472 tumors received vehicle or efficacious patupilone doses (4 and 0.8-1.5 mg/kg i.v., respectively). Tumor vascularity assessment by dynamic contrast-enhanced or dynamic susceptibility contrast magnetic resonance imaging and interstitial fluid pressure (IFP) occurred at baseline, 2 days (mice and rats), and 6 days (rats) after treatment and were compared with histologic measurements and correlated with tumor response., Results: In B16/BL6 metastases, patupilone (4 mg/kg) induced a 21 +/- 5% decrease (P < 0.001) in tumor blood volume and a 32 +/- 15% decrease (P = 0.02) in IFP after 2 days and reduced tumor growth and vessel density (>42%) after 2 weeks (P < or = 0.014). Patupilone dose-dependently inhibited BN472 tumor growth (day 6) and reduced IFP on days 2 and 6 (-21% to -70%), and the percentage change in IFP correlated (P < 0.01) with the change in tumor volume. In both models, histology and vascular casts confirmed decreases in tumor blood volume. One patupilone (0.8 mg/kg) administration decreased (P < 0.01) tumor IFP (54 +/- 4%), tumor blood volume (50 +/- 6%), and vessel diameter (40 +/- 11%) by day 6 but not the apparent diffusion coefficient, whereas histology showed that apoptosis was increased 2.4-fold and necrosis was unchanged. Apoptosis correlated negatively (P < 0.001) with IFP, tumor blood volume, and tumor volume, whereas tumor blood volume and IFP were correlated positively (P = 0.0005)., Conclusions: Vascular disruptive effects of patupilone were detected in situ using dynamic contrast-enhanced or dynamic susceptibility contrast magnetic resonance imaging and IFP. Changes in IFP preceded and correlated with tumor response, suggesting that IFP may be a surrogate biomarker for patupilone efficacy.

Purpose: To investigate the physiological origins responsible for the varying blood oxygenation level dependent (BOLD) magnetic resonance imaging (MRI) responses to carbogen (95% O(2)/5% CO(2)) breathing observed with different tumor types., Materials and Methods: Susceptibility contrast-enhanced MRI using the exogenous blood pool contrast agent NC100150 to determine blood volume and vessel size, and immunohistochemical-derived morphometric parameters, were determined in GH3 prolactinomas and RIF-1 fibrosarcomas, both grown in mice, which exhibited very different BOLD responses to carbogen., Results: Administration of NC100150 increased the R(2)* and R(2) rates of both tumor types, and indicated a significant four-fold larger blood volume in the GH3 tumor. The ratio deltaR(2)*/deltaR(2) showed that the capillaries in the GH3 were two-fold larger than those in the RIF-1, in agreement with morphometric analysis. Carbogen breathing induced a significant 25% decrease in R(2)* in the GH3 prolactinoma, whereas the response in the RIF-1 fibrosarcoma was negligible., Conclusion: Low blood volume and small vessel size (and hence reduced hematocrit) are two reasons for the lack of R(2)* change in the RIF-1 with carbogen breathing. BOLD MRI is sensitive to erythrocyte-perfused vessels, whereas exogenous contrast agents interrogate the total perfused vascular volume. BOLD MRI, coupled with a carbogen challenge, provides information on functional, hemodynamic tumor vasculature., (Copyright 2003 Wiley-Liss, Inc.)

Hypoxia-inducible factor-1 (HIF-1) regulates many pathways potentially important for tumor growth, including angiogenesis and glycolysis. Most attention has focused on its role in the response to hypoxia, but HIF-1 is also constitutively expressed in many tumors. To analyze the role of this pathway in vivo, we used magnetic resonance (MR) methods and complementary techniques to monitor metabolic changes in tumors derived from HEPA-1 mouse hepatoma lines that were either wild type (WT) or deficient in hypoxia-inducible transcription factor HIF-1beta (c4). The c4 tumors grew significantly more slowly than the WT tumors (P < 0.05), but were examined at a similar size (0.4-0.6 g). At the tumor size used in these studies, no differences in vascularity were observed, and MR parameters measured that related to tumor blood flow, vascularity, and oxygenation demonstrated no significant differences between the two tumor types. Unexpectedly, the ATP content of the c4 tumor was approximately 5 times less than in the WT tumor [measured in tumor extracts (P < 0.001) and by metabolic imaging (P < 0.05)]. Noninvasive (31)P MR spectroscopy showed that the nucleoside triphosphate/P(i) ratio of the two tumor types was similar, so the low ATP content of the c4 tumors was not caused by (or a cause of) impaired cellular bioenergetics. Rather, glycine, an essential precursor for de novo purine formation, was significantly lower in the c4 tumors (P < 0.05), suggesting that ATP synthesis was impaired in the mutant tumor cells. Supporting evidence for this hypothesis came from the significantly lower concentrations of betaine, phosphocholine, and choline in the c4 tumors (P < 0.05); these are intermediates in an alternative pathway for glycine synthesis. No significant differences were seen in lactate or glucose content. MR resonances from phosphodiesters, which relate to the metabolic turnover of phospholipid membranes, were significantly lower in the WT tumors than in the c4 tumors, both in vivo (P < 0.05) and in extracts (P < 0.01). We propose that loss of up-regulation of expression of the genes for glucose transporters and glycolytic enzymes in the c4 tumors decreased formation of glycine, an essential precursor of ATP synthesis, and thus caused the low ATP content of the c4 tumors. In summary, these data suggest that disruption of the HIF-1 pathway in these tumor cells impairs the supply of anabolic precursors required for cell synthesis. They suggest potential biochemical targets that may be modified by therapy blocking HIF-1 function.