肿瘤组织间液压在肿瘤研究中的作用

在多种细胞因子作用下,肿瘤组织间液压(IFP)增高.其对肿瘤的早期诊断、病情进展、预后生存有一定的指示作用,特别是对于患者治疗方案的选择及疗效有较大的指导、预测作用.针对肿瘤组织间液压增高机制的靶向性治疗,极大地提高了肿瘤的疗效.     

Nicotinamide can lower tumor interstitial fluid pressure: mechanistic and therapeutic implications.

Several investigators have shown that nicotinamide (NA) may increase the tumor blood flow and/or alleviate temporal fluctuations in tumor blood flow and, consequently, increase pO2. However, the mechanisms of these changes in tumor blood flow are not understood, especially because NA lowers the mean arterial blood pressure in mice. Our hypothesis is that NA may decrease flow resistance in tumors, which would lower vascular pressure and tumor interstitial fluid pressure (TIFP). To test this hypothesis, we measured the physiological parameters: mean arterial blood pressure, TIFP, tumor water content, and hematocrit in C3H mice bearing FSaII tumors, before and after treatment with 500 mg/kg of NA. In control animals, TIFP increased with tumor growth up to 400 mm3, reached a plateau, and then decreased when the tumor size was above 1000 mm3 (n = 135). Tumor water content correlated significantly with TIFT (for tumors less than 500 mm3) (n = 26). NA caused approximately a 15% decrease in mean arterial blood pressure (P less than 0.05) and a 35% decrease in TIFP (P less than 0.001) at 2 h postinjection, without any change in hematocrit. The change in TIFP was found to be tumor size dependent. Specifically, NA decreased the TIFP by 47% (P less than 0.001) and 39% (P less than 0.001) in medium (200 to 500 mm3) and large (500 to 800 mm3) tumors, respectively. The decrease in TIFP in small (less than 200 mm3) and very large (greater than 800 mm3) tumors was not statistically significant (P greater than 0.1). Our results may explain the size-dependent enhancement in pO2 and radiation response reported by I. Lee and C. W. Song (Radiat. Res., 130: 65-71, 1992) for this tumor line. If our results could be confirmed in human tumors in situ, they would have significant implications in noninvasive measurements of TIFP using NMR and in cancer treatment using radiation, chemotherapy, and immunotherapy.     

Taxane-induced apoptosis decompresses blood vessels and lowers interstitial fluid pressure in solid tumors: clinical implications.

Elevated tumor interstitial fluid pressure (IFP) is partly responsible for the poor penetration and distribution of therapeutic agents in solid tumors. The etiology of tumor interstitial hypertension is poorly understood. We have postulated that the solid stress generated by tumor cells growing in a confined space compresses blood vessels and increases tumor microvascular pressure and IFP. To test the hypothesis that neoplastic cell loss would decompress blood vessels and lower IFP, we induced apoptosis in tumors with paclitaxel and docetaxel. Taxanes inhibited the growth of the murine mammary carcinoma (MCa-IV) and of the human soft tissue sarcoma (HSTS-26T). Taxanes induced apoptosis and reduced the density of intact neoplastic cells in both MCa-IV and HSTS-26T. To determine whether neoplastic cell loss decompressed blood vessels, we measured the diameter of tumor vessels in HSTS-26T tumors implanted in transparent dorsal skin fold chambers. At 48 and 96 h after paclitaxel, the diameter of tumor vessels was significantly increased. The increase in vascular diameters was associated with reductions in microvascular pressure and IFP. The changes in neoplastic cell density and IFP were also correlated. In the human glioblastoma U87, which is resistant to paclitaxel, the IFP and cellular density were not modified by paclitaxel treatment. Collectively, these results support the hypothesis that solid stress generated by neoplastic cell proliferation increases vascular resistance and IFP. The increase in vessel diameter induced by paclitaxel and docetaxel suggests that taxanes could improve tumor response by increasing the vascular surface area for delivery of therapeutic agents.     

Dynamic contrast-enhanced magnetic resonance imaging of tumor interstitial fluid pressure

Background and purpose

High interstitial fluid pressure (IFP) in the primary tumor has been shown to promote metastasis in melanoma xenografts and to predict for poor survival in cervical cancer patients. The potential usefulness of gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA)-based dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) for assessing tumor IFP noninvasively was investigated in the present study.

Materials and methods

A-07 and R-18 melanoma xenografts with and without necrotic regions were subjected to DCE-MRI and subsequent measurement of IFP. Tumor images of E·F (E is the initial extraction fraction of Gd-DTPA and F is blood perfusion) and λ (λ is proportional to extracellular volume fraction) were produced by Kety analysis of DCE-MRI series.

Results

In tumors without necrosis, significant inverse correlations were found between E·F and IFP, both for A-07 and R-18 tumors, and between λ and IFP for A-07 tumors. Significant correlations beween E·F and IFP or between λ and IFP could not be detected for tumors with necrotic regions.

Conclusions

DCE-MRI may be developed to be a useful noninvasive method for assessing IFP in tumors without necrosis. This possibility warrants further studies involving several physiologically different experimental tumor lines, as well as human tumors.     

Interstitial pressure gradients in tissue-isolated and subcutaneous tumors: implications for therapy

High interstitial fluid pressure (IFP) in solid tumors is associated with reduced blood flow as well as inadequate delivery of therapeutic agents such as monoclonal antibodies. In the present study, IFP was measured as a function of radial position within two rat tissue-isolated tumors (mammary adenocarcinoma R3230AC, 0.4-1.9 g, n = 9, and Walker 256 carcinoma, 0.5-5.0 g, n = 6) and a s.c. tumor (mammary adenocarcinoma R3230AC, 0.6-20.0 g, n = 7). Micropipettes (tip diameters 2 to 4 microns) connected to a servo-null pressure-monitoring system were introduced to depths of 2.5 to 3.5 mm from the tumor surface and IFP was measured while the micropipettes were retrieved to the surface. The majority (86%) of the pressure profiles demonstrated a large gradient in the periphery leading to a plateau of almost uniform pressure in the deeper layers of the tumors. Within isolated tumors, pressures reached plateau values at a distance of 0.2 to 1.1 mm from the surface. In s.c. tumors the sharp increase began in skin and levelled off at the skin-tumor interface. These results demonstrate for the first time that the IFP is elevated throughout the tumor and drops precipitously to normal values in the tumor's periphery or in the immediately surrounding tissue. These results confirm the predictions of our recently published mathematical model of interstitial fluid transport in tumors (Jain and Baxter, Cancer Res., 48: 7022-7032, 1988), offer novel insight into the etiology of interstitial hypertension, and suggest possible strategies for improved delivery of therapeutic agents.     

Hyperoxia increases the uptake of 5-fluorouracil in mammary tumors independently of changes in interstitial fluid pressure and tumor stroma

Background  

Hypoxia is associated with increased resistance to chemo- and radiation-therapy. Hyperoxic treatment (hyperbaric oxygen) has previously been shown to potentiate the effect of some forms of chemotherapy, and this has been ascribed to enhanced cytotoxicity or neovascularisation. The aim of this study was to elucidate whether hyperoxia also enhances any actual uptake of 5FU (5-fluorouracil) into the tumor tissue and if this can be explained by changes in the interstitium and extracellular matrix.     

Noninvasive magnetic resonance imaging of transport and interstitial fluid pressure in ectopic human lung tumors

Tumor response to blood borne drugs is critically dependent on the efficiency of vascular delivery and transcapillary transfer. However, increased tumor interstitial fluid pressure (IFP) forms a barrier to transcapillary transfer, leading to resistance to drug delivery. We present here a new, noninvasive method which estimates IFP and its spatial distribution in vivo using contrast-enhanced magnetic resonance imaging (MRI). This method was tested in ectopic human non-small-cell lung cancer which exhibited a high IFP of approximately 28 mm Hg and, for comparison, in orthotopic MCF7 human breast tumors which exhibited a lower IFP of approximately 14 mm Hg, both implanted in nude mice. The MRI protocol consisted of slow infusion of the contrast agent [gadolinium-diethylenetriaminepentaacetic acid (GdDTPA)] into the blood for approximately 2 hours, sequential acquisition of images before and during the infusion, and measurements of T1 relaxation rates before infusion and after blood and tumor GdDTPA concentration reached a steady state. Image analysis yielded parametric images of steady-state tissue GdDTPA concentration with high values of this concentration outside the tumor boundaries, approximately 1 mmol/L, declining in the tumor periphery to approximately 0.5 mmol/L, and then steeply decreasing to low or null values. The distribution of steady-state tissue GdDTPA concentration reflected the distribution of IFP, showing an increase from the rim inward, with a high IFP plateau inside the tumor. The changes outside the borders of the tumors with high IFP were indicative of convective transport through the interstitium. This work presents a noninvasive method for assessing the spatial distribution of tumor IFP and mapping barriers to drug delivery and transport.     

Therapeutic implications of tumor heterogeneity

At the outset of this review, we stated that we wished to raise some questions that challenge the commonly held view that tumor heterogeneity is of major significance to treatment failure. The nature of this challenge is the following: although tumor heterogeneity in sensitivity to therapeutic agents has been demonstrated repeatedly, using isolated subpopulations of cells, primarily in cell culture systems, there is very little work that has been directed toward asking the tough questions about how that heterogeneity actually impacts on the response to treatment in vivo. In our own work, when we have attempted to simulate heterogeneity, in vivo or in vitro with mixed populations of tumor cells, we have seen that the simple prediction that treatment response would reflect the sensitivities of the individual subpopulations was not valid. Tumor subpopulation interactions, influencing both growth and drug sensitivity, resulted in treatment responses that were either better or worse than would be expected. Shifts in the distribution of subpopulations under the influence of therapy did not necessarily correlate with treatment response. Marked differences in the relative proportions of subpopulations within tumors did not necessarily translate into marked differences in the behavior of whole tumors. Imposition of in vivo-like three-dimensional tissue architecture caused major changes in the overall drug sensitivity of individual subpopulations, beyond those seen as a result of heterogeneity. Of course we realize that our work is very limited, one tumor system and a few treatment protocols, but that is the challenge. Much more in-depth experimental and clinical research is necessary in order to evaluate how, and how much, tumor heterogeneity really does affect treatment. Without such work, efforts to devise more effective treatment strategies, based on common assumptions and theoretical models, rather than experimental analysis, can only be superficial and, ultimately, useless.     

The relationship between elevated interstitial fluid pressure and blood flow in tumors: a bioengineering analysis

Purpose: To examine the hypothesis that elevated interstitial fluid pressure (IFP) is a cause of reduced blood flow in tumors.

Materials and Methods: A physiologic model of tumor blood flow was developed based on a semipermeable, compliant capillary in the center of a spherical tumor. The model incorporates the interaction between the tumor vasculature and the interstitium, as mediated by IFP. It also incorporates the dynamic behavior of the capillary wall in response to changes in transmural pressure, and the effect of viscosity on blood flow.

Results: The model predicted elevated tumor IFP in the range of 0 to 56 mmHg. The capillary diameter in the setting of elevated IFP was greatest at the arterial end, and constricted to between 3.2 and 4.4 μm at the venous end. This corresponded to a 2.4- to 3.5-fold reduction in diameter along the length of the capillary. The IFP exceeded the intravascular pressure distally in the capillary, but vascular collapse did not occur. Capillary diameter constriction resulted in a 2.3- to 9.1-fold steady-state reduction in tumor blood flow relative to a state of near-zero IFP.

Conclusion: The results suggest that steady-state vascular constriction occurs in the setting of elevated IFP, and leads to reduced tumor blood flow. This may in turn contribute to the development of hypoxia, which is an important cause of radiation treatment failure in many tumors.     

Therapeutic implications of tumor physiology.

The advent of genetic engineering and hybridoma technology has led to the design and large-scale production of various novel therapeutic agents for the treatment of cancer. However, these agents have not yet realized their clinical potential, presumably due to physiologic resistance inherent in tumors. An improved understanding of tumor physiology is necessary for development of more effective cancer therapy regimens. This article discusses the physiologic barriers to the delivery of these agents to tumors and some strategies to overcome or exploit tumor physiology for therapeutic benefit.     

Effects of the vascular disrupting agent ZD6126 on interstitial fluid pressure and cell survival in tumors

Interstitial fluid pressure (IFP) is elevated in tumors due to abnormal vasculature, lack of lymphatic drainage, and alterations in the tumor interstitium. ZD6126 is a tubulin-binding agent that selectively disrupts tumor vasculature resulting in tumor necrosis. This study examined the effect of ZD6126 on tumor IFP and the response of tumors with different IFP levels to ZD6126. Pretreatment IFP was measured using the wick-in-needle method in tumors (murine KHT-C and human CaSki) growing i.m. in the hind legs of mice. Mice were treated i.p. with a single dose of ZD6126 (100 or 200 mg/kg) and posttreatment IFP measurements were made. Blood flow imaging was conducted using Doppler optical coherence tomography, whereas oxygen partial pressure was measured using a fiber optic probe. Clonogenic assays were done to determine tumor cell survival. In KHT-C tumors, IFP dropped significantly at 1 hour posttreatment, returned to pretreatment values at 3 hours, and then declined to approximately 25% of the pretreatment values by 72 hours. In CaSki tumors, the IFP decreased progressively, beginning at 1 hour, to approximately 30% of pretreatment values by 72 hours. Clonogenic cell survival data indicated that ZD6126 was less effective in tumors with high IFP values (>25 mm Hg). Vascular disrupting agents, such as ZD6126, can affect IFP levels and initial IFP levels may predict tumor response to these agents. The higher cell survival in high IFP tumors may reflect greater microregional blood flow limitations in these tumors and reduced access of the drug to the target endothelial cells.     

Reducing endothelial NOS activation and interstitial fluid pressure with n-3 PUFA offset tumor chemoresistance

The aim of this study was to determine how n-3 polyunsaturated fatty acid (PUFAs) counteracted tumor chemoresistance by restoring a functional vascularization. Rats with chemically induced mammary tumors were divided into two nutritional groups: a control group and a group fed with an n-3 PUFA-enriched diet. Both groups were treated with docetaxel. Functional vascular parameters (ultrasounds, interstitial fluid pressure) were determined for both nutritional groups before (W(0)) and during docetaxel treatment [every 2 h up to 1 week (W(+1)) for interstitial fluid pressure, at W(+1) for Evans blue extravasation and at W(+2) and W(+6) for ultrasounds]. In vitro n-3 PUFA-induced changes in endothelial cell migration, permeability and phosphorylation of endothelial nitric oxide synthase were evaluated using human umbilical vein endothelial cells. Whereas docetaxel stabilized tumor growth in the rat control group, it induced a 50% tumor regression in the n-3 PUFA group. Ultrasounds parameters were consistently lower in the n-3 PUFA group at all time points measured, down to ～50% at W(+6). A single dose of docetaxel in the n-3 PUFA group markedly reduced interstitial fluid pressure from 2 h after injection up to W(+1) when Evans blue extravasation was increased by 3-fold. A decreased activation of endothelial nitric oxide synthase in tumors of the n-3 PUFA group, and in human umbilical vein endothelial cell cultured with n-3 PUFA, points toward a PUFA-induced disruption of nitric oxide signaling pathway. This normalization of tumor vasculature functions under n-3 PUFA diet indicates that such a supplementation, by improving drug delivery in mammary tumors, could be a complementary clinical strategy to decrease anticancer drug resistance.     

Interference with TGF-beta1 and -beta3 in tumor stroma lowers tumor interstitial fluid pressure independently of growth in experimental carcinoma

A high tumor interstitial fluid pressure (TIFP) is a pathologic characteristic distinguishing the stroma of carcinomas from normal interstitial loose connective tissues. The role of TGF-beta1 and -beta3 in generating a high TIFP was investigated in xenografted experimental anaplastic thyroid carcinoma (ATC) derived from the human ATC cell line KAT-4. A single intravenous injection of a soluble recombinant TGF-beta receptor type II-murine Fc:IgG(2A) chimeric protein that specifically inhibits TGF-beta1 and -beta3, significantly lowered TIFP in a time and concentration dependent manner but did not change total tissue water content in the tumors. Tumor growth rate was higher in tumors treated with the TGF-beta1 and -beta3 inhibitor compared to control tumors during the first 10 days after administration of the inhibitor. The apoptotic index of carcinoma cells, and expression of the cell cycle inhibitor p27(Kip1), were, however, increased in TGF-beta1 and -beta3 inhibitor-treated tumors. Prolonged treatment periods and administration of a second dose of the inhibitor decreased tumor growth rate. The TGF-beta1 and -beta3 inhibitor did not affect proliferation or expression of phosphorylated Smad2 protein in KAT-4 cells cultured in vitro. Our results indicate that members of the TGF-beta family are potential targets for novel anti-cancer treatment directed to the stroma. First by controlling TIFP and by that potentially the uptake of anticancer drugs into tumors and second by their suggested role in maintaining a supportive tumor stroma.     

Mild elevation of body temperature reduces tumor interstitial fluid pressure and hypoxia and enhances efficacy of radiotherapy in murine tumor models

Human and rodent solid tumors often exhibit elevated interstitial fluid pressure (IFP). This condition is recognized as a prognostic indicator for reduced responses to therapy and decreased disease-free survival rate. In the present study, we tested whether induction of a thermoregulatory-mediated increase in tissue blood flow, induced by exposure of mice to mild environmental heat stress, could influence IFP and other vascular parameters within tumors. Using several murine tumor models, we found that heating results in a sustained reduction in tumor IFP correlating with increased tumor vascular perfusion (measured by fluorescent imaging of perfused vessels, laser Doppler flowmetry, and MRI) as well as a sustained reduction in tumor hypoxia. Furthermore, when radiation therapy was administered 24 hours postheating, we observed a significant improvement in efficacy that may be a result of the sustained reduction in tumor hypoxia. These data suggest, for the first time, that environmental manipulation of normal vasomotor function is capable of achieving therapeutically beneficial changes in IFP and microvascular function in the tumor microenvironment.     

The human tumor microenvironment: invasive (needle) measurement of oxygen and interstitial fluid pressure

Invasive needle-based assessments of the extracellular environment in human tumors have yielded important prognostic information that has shaped the direction of future translational research and begun to influence clinical practice. This review focuses on electrode measurements of oxygenation in human tumors, particularly in relation to the practicalities of applying these techniques in the clinic and the relationship to patient outcome. Elevated tumor interstitial fluid pressure (IFP) has been shown to be an important independent prognostic factor in cervix cancer. The pathophysiology of elevated IFP is discussed, along with possible explanations for the strong influence on patient outcome and directions for future research.     

Pulmonary and lymph node metastasis is associated with primary tumor interstitial fluid pressure in human melanoma xenografts

Interstitial fluid pressure (IFP) is elevated in many experimental and human tumors, and high IFP is associated with poor prognosis in human cancer. The significance of elevated IFP in the development of metastatic disease was investigated in the present work by using A-07 human melanoma xenografts as models of cancer in humans. IFP was measured with the micropipette technique (tumor periphery) and the wick-in-needle technique (tumor center). Tumor hypoxia was studied by immunohistochemistry using pimonidazole as a hypoxia marker and by using a radiobiological assay. High central tumor IFP was found to be associated with the development of pulmonary (P = 0.000085) and lymph node (P = 0.000036) metastases in small (150-200 mm(3)) A-07 tumors. Hypoxic cells could not be detected in these tumors. Our study suggests that interstitial hypertension may facilitate tumor cell intravasation and, hence, promote metastasis by mechanisms independent of tumor hypoxia.     

Resistance of tumor interstitial pressure to the penetration of intraperitoneally delivered antibodies into metastatic ovarian tumors.

PURPOSE: Despite evidence that regional chemotherapy improves the treatment of metastatic peritoneal ovarian carcinoma, monoclonal antibodies have not shown significant success in i.p. delivery. The present study was designed to address the hypothesis that convective penetration of macromolecular antineoplastic agents depends on a positive pressure difference between the i.p. therapeutic solution and the tumor. EXPERIMENTAL DESIGN: Nude rats with human ovarian xenografts implanted in the abdominal wall were used in experiments to facilitate in vivo measurement of tumor pressure and the treatment of the tumor with i.p. solutions at high pressures. Penetration of (125)I-labeled trastuzumab was measured with quantitative autoradiography. RESULTS: Tumor pressure profiles showed peak pressures of 32 mm Hg with mean pressures (+/- SD, mm Hg) in 12 SKOV3 tumors of 9.7 +/- 8.3 and in 15 OVCAR3 tumors of 12.5 +/- 7.0. I.p. therapeutic dwells at 6 to 8 mm Hg (maximum feasible pressure) showed significantly less penetration of trastuzumab than in adjacent normal muscle. To establish a driving force for convection into the tumor, various maneuvers were attempted to reduce tumor pressure, including treatment with taxanes or prostaglandin E(1), elimination of tumor circulation, and removal of the tumor capsule. Tumor decapsulation decreased the pressure to zero but did not enhance the penetration of antibody. Binding to specific trastuzumab receptors on each tumor was shown to be not a significant barrier to antibody penetration. CONCLUSIONS: The results only partially support our hypothesis and imply that the microenvironment of the tumor is in itself a major barrier to delivery of charged macromolecules.     

Hemostasis and tumor invasion. Therapeutic implications

Plasminogen activator activity (PAA) has been detected in various tumor cells or in their excretion products. In some cell systems PAA is a symptom of cell transformation, but its amount is questionably correlated with the invasiveness of the tumor cells. Procoagulant and aggregation activities on platelets, have been demonstrated in various tumor cells. There are weakly correlated with the metastatic potential of these cells. In vivo, the treatment of animals by modifiers of the hemostasis, or of the fibrinolysis systems provides contradictory results. Some reduction of metastatic diffusion and increase of life span have been noted with Warfarin. Clinical trials are scarce and their methodology is debatable. When conclusive, a lengthening of the life span has been observed, but not a reduction of the metastatic spread as metastases were still present.