FIELD OF THE INVENTIONThis invention relates to the use of microporous membranes in which is enclosed isolated living malignant tissue for the purpose of inducing a strong immune response after introduction in a body cavity in the treatment of malignant tumors.[0002]
The invention relates especially to the use of artificial membranes, which are not only compatible with the physiological environment in the body but enable the exchange of macromolecular and cellular components of the immune system in both directions without allowing the leakage of malignant cells into the blood and lymphatic circulation (i.e. after introduction of the membrane with the isolated tissue into the body cavity in a suitable holder).[0003]
DESCRIPTION OF THE PRIOR ARTA very efficient method in the treatment of cancer is known under the term “devitalization”. The devitalization surgical technique has been described extensively in the literature not only in its application in model experiments using animals (Fortyn, K., et al. Z.exp.Chir.Transplant.kunstl. Organe. 18 :34-41, 1985; Fortyn, K. et al. Acta Chirurgica Hungarica. 29 (2) :163-172, 1988) but also in clinical practice particularly in connection with tumor affections of the gastrointestinal tract (Fortyn, K., et al. Klinicka onkologie. 1 : 7-10, 1989).[0004]
Devitalization is a surgical intervention which is aimed to interrupt all vascular supply, i.e. simultaneously the arterial flow and venous reflux in a delimited mass of tissue in the body. This stops blood circulation in the affected area, the filtration of serum from the capillaries is brought to a halt and the production of lymph ceases. The ensuing ischaemia affects nerve extremities in the tissue. The transmission of impulses is thus interrupted and the perception of pain in the devitalized site is relieved. The devascularized tissue is gradually resorbed and the process provokes an immune response by which metastases are eliminated.[0005]
The critical physiological condition of the devitalization surgical intervention is that it does not lead to the immediate damaging of the integrity of the plasma membrane of cells in the affected tissue. There is no massive necrotic cytolysis typical for ischaemia which is produced by obstruction of arterial flow and generally leads to the liberation of larger quantities of allergens. These penetrate the tissue not only locally but may also enter the blood and lymphatic circulation. Ischaemia under such conditions normally causes undesirable inflammatory reactions but in extreme cases it may even provoke a fatal systemic shock. This is observed especially in various forms of directed embolization which must not be confused with devitalization.[0006]
The physiological effect which is produced by devitalization differs from the effect of simple arterial obstruction in that ordinary embolization mainly leads to the interruption of the oxygen supply while other blood components can still penetrate the affected tissue by venous reflux. Because venous blood deprived of oxygen and saturated with carbon dioxide has a lower value pH a greater amount of calcium which is bound to proteins in the blood is liberated. The lowering of the energetic reserve of ATP in cells as a result of ischaemia disrupts the electric potential at the plasma membrane which is necessary for maintaining normal levels of the intracellular concentration of calcium. With the onset of ischaemia and by the continuing supply of nutrients from the venous reflux, calcium enters tissue cells in larger amounts and activates Ca[0007]2+ dependent phospholipases. This leads to irreversible damage of the plasma membrane resulting in leakage and massive cellular lysis.
In spite of the fact that devitalization involves a more consequent ischaemia, massive necrotic cytolysis is prevented because the affected tissue is not supplied with blood components that could provoke the disruption of the plasma membrane.[0008]
Following devitalization, when venous reflux is arrested, the integrity of the plasma membrane is preserved not only in healthy cells but also in the malignant cells of the affected tissue. The determining circumstance for devitalization to exert its therapeutical effect is the high degree of ischaemia and the lack of growth factors which are two important physiological conditions necessary for immune system triggering of apoptosis or programmed cellular death. In such an environment, cellular distress and immune system signals are generated by all forms of leucocytes particularly monocytes and lymphocytes present in the tissue prior to devitalization. On the other hand, in the case of simple embolization, apoptosis is not likely to occur because the depletion of growth factors and an increasing concentration of intracellular calcium which act in opposition will inhibit the mechanisms normally responsible for its triggering. When apoptosis or programmed cellular death is initiated, cellular disintegration is progressive and is genetically controlled in such a way that it does not lead to the liberation of larger amounts of allergens either locally or into the general circulation. Devitalization, therefore, does not provoke an inflammatory reaction which in acute cases may create an adverse physiological environment linked with the risk of necrotic infection. Apoptosis normally leads to the fragmentation of cellular components and these are progressively phagocytised by competent leucocytes especially macrophages. The affected cellular mass is gradually degraded to simple components by specific enzymes and this contributes to the positive stimulation of the entire immune system. Simultaneously, antigens liberated from malignant cells under these conditions begin to be recognized as non-self and the immune system is mobilized to destroy malignancies in the whole body. The activity is due not only to leucocytes which infiltrate the affected area under the effect of chemotaxis but also leucocytes which are present in the tissue prior to the devitalization intervention.[0009]
In principle, devitalization as a surgical technique in which devascularized or completely isolated malignant tissue is left in the body can be applied in the treatment of all types of solid tumors in most organs of the body. A certain exception are soft and highly vascularized tissues and those which are surgically inaccessible. A typical example is brain tissue. Another major disadvantage of the standard devitalization technique is the fact that its application is indicated especially in cases where the tumor affection was diagnosed too late to expect complete remission following either radical surgery or any other type of treatment. These are mostly situations when there is important invasion of the malignancy into surrounding tissues, lymph nodes and even other organs. This means that after the devitalization intervention the possible secondary dissemination of malignant cells does not represent any new potential danger for the patient. In this connection, it is therefore necessary to consider the possibility of an eventual slower immune response if the intervention is carried out at an earlier stage of the tumor affection when it is not possible to predict the reaction of the organism. In such a case, a larger mass of isolated malignant tissue left in a body cavity can be linked with the risk of a more important dissemination of malignant cells even before the immune system is fully mobilized to react and with no possibility of clinically monitoring the progress of the intervention and interrupting it without serious consequences should there be any anomalous behavior.[0010]
SUMMARY OF THE INVENTIONThe invention relates to a device for inducing a generalized immune response against primary solid tumors and metastases in cancer therapy. This device acts by enclosing autologous living malignant tissue in an inhibitive ischemic environment formed by a porous membrane inside a holder which can take any suitable anatomically compatible shape when introduced either partially or integrally at an implantation site in a body cavity. The membrane generally has pores larger than 2 microns but smaller than the mean size of the cells of the biological tissue which is enclosed in the holder. Thus, the size of the pores is specifically chosen so that all forms of large immunologically active leucocytes can pass freely in and out of the holder while smaller malignant cells of specific tumors remain safely trapped inside without the risk of their secondary dissemination at the implantation site. Preferably, the size of the pores of the membrane ranges from about 6-15 microns.[0011]
The holder is generally provided with a tubular shape and is equipped with a cutting member at its inner extremity to cut away fibrous tissue overgrowing the membrane during clinical application of the device. The cutting member of the holder is conveniently designed as a sliding tube or ring possessing a sharp edge. Also, the holder can include tubular extensions for the sampling of biological material during clinical application of the device.[0012]
The holder advantageously includes electrodes for the control of physiological factors, such as internal and external temperature. Also, the holder can include an electrode for the control of pH, an electrode for the control of the redox potential, or an electrode for the control of pO2. The holder also can include bioelectrodes, or a heating element. The membrane is preferably made from a hydrophilic plastic material that is compatible with the physiological environment of the body cavity.[0013]
Another embodiment of the invention relates to a method for inducing an immune response against malignant cells and tumors in cancer therapy, which comprises enclosing living malignant biological tissue in a space formed by a microporous membrane inside a holder which is introduced either partially or integrally into a body cavity. Any of the holders described herein can be used in this method.[0014]
The holder generally has the form of an endoscopic tube which is introduced into the body cavity for a defined period and then removed without the need of a more important surgical intervention. Also, holder may be provided with a flexible extension for integral introduction into the body on the principle of an endoscope. For convenience, the holder may be provided with openings for sampling needles and electrodes.[0015]