The role of cytokines in changing pathophysiology of solid tumors that leads to enhanced uptake and efficacy of stealth liposomal doxorubicin or cisplatin
2000 - 12 / 2004
Purpose: Systemic chemotherapy does not result in adequate intratumoral drug levels in the treatment of many solid tumors. High interstitial fluid pressure (IFP) and other pathophysiologic conditions at the tumor site are responsible for this. Some of these barriers may be overcome (in part) by using long-circulating liposomal formulations. Cytokines may enhance homing of these liposomes to the tumor, which results in a significant increase in intratumoral drug uptake and is reflected by enhanced anti-tumor efficacy. We have clearly demonstrated thus far that repeated systemic administration of low dose TNF plus doxorubicin liposomes results in an increased intratumoral uptake of liposomes and a significantly enhanced anti-tumor efficacy. We have shown that TNF increases vascular permeability in the tumor and others have shown a rapid drop in IFP by TNF. Low dose TNF can already bring about these effects indicating a new potential clinical role for TNF. Now that TNF has been registered as an anti-cancer drug in Europe for the setting of an isolated limb perfusion for advanced extremity sarcomas, TNF is here to stay, and the application of this drug in the clinic must be explored further. Moreover other registered cytokines, such as IL-2, can also exert clear modulation of vascular permeability and offer further opportunities. With the variety of our tumor models this potential can be adequately investigated. Plan of investigation: The project focuses on cytokine-mediated manipulation of solid tumor physiology with two cytokines that have been registered as anti-cancer drugs: TNF and IL2. The mechanisms by which they enhance anti-tumor effects of stealth liposomal doxorubicin (DOX-SL) and cisplatin (CDDP-SL) will be evaluated in both in vitro and in vivo models. The in vivo tumor models vary in vascularity from hyper- (BNI75), to intermediate (ROS-1), to hypo-vascularized (CC531). The in vivo tumor models are key. In the first place mechanistic studies will be conducted to examine the effect of treatment on the tumor associated vasculature (TAV). Secondly, anti-tumor efficacy will be evaluated. I. Mechanistic in vivo studies a) Permeability changes of the TAV will be measured by 1) extravasation of particles of defamed size, 2) changes in interstitial fluid pressure (IFP) and 3) changes in pH. b) Histology on sequential tumor and healthy tissue biopsies to evaluate vascular damage, cellular infiltrates, adhesion molecule expression on endothelial cells, cell aggregations to endothelial cells. c) Apoptosis of endothelial cells of the TAV and of tumor cells with annexin V and TUNEL. d) Drug levels in tumor tissue, using fluorescence photospectrometry, and HPLC/mass spectrometry. II. In vitro studies Effect of cytokines +/- cytotoxic drugs on tumor cells and HUVECS; cell survival, apoptosis, drug uptake, adhesion molecule expression. III. Efficacy studies a) For initial studies the limb tumor models are used, as they are already very well characterized by us. b) The liver model is used to validate the findings in an organ-metastasis setting. Secondly, treatment of liver tumor by hepatic artery infusion (HAI) allows repeated administrations and high local concentrations which could be of importance when a threshold for anti-tumor activity may not be overcome by systemic treatment. IV. Dorsal window flap model The dorsal window flap model is used to address specific questions on effect on the TAV. This model allows real time imaging of vascular damage, tissue penetration, cell adherence and tissue degradation. Possible results: This project may well identify new utilities of the cytokines TNF and IL2 in combination with long circulating liposomal cytotoxic drug formulations. It explores effects of these cytokines that can be achieved by clinically applicable doses and the mechanisms that thus far have been inadequately explored. It significantly enhances our knowledge of crucial pathophysiologic conditions of the tumors and how to manipulate them in the development of more efficacious anti-tumor strategies. Relevance for cancer research: Better insight into the thus far inadequately explored modulating of tumor pathophysiology by cytokines and how this modulation can be used to enhance the activity of other drugs and drug formulations such as liposomes is of general value to the field. The results of the project may then lead to the design of phase I-II studies in patients.