Intra-arterial administration of beta-emitting particles that become trapped in the vascular bed of a tumour and remain there while delivering high doses, represents a unique approach in the treatment of both primary and metastatic liver tumours. Studies on selective internal radiation therapy of colorectal liver metastases using yttrium-90 glass microspheres have shown encouraging results. This study describes the biodistribution of 40-microm poly lactic acid microspheres loaded with radioactive holmium-166, after intra-arterial administration into the hepatic artery of rats with implanted liver tumours. Radioactivity measurements showed >95% retention of injected activity in the liver and its resident tumour. The average activity detected in other tissues was < or =0.1%ID/g, with incidental exceptions in the lungs and stomach. Very little 166Ho activity was detected in kidneys (<0.1%ID/g), thereby indicating the stability of the microspheres in vivo. Tumour targeting was very effective, with a mean tumour to liver ratio of 6. 1+/-2.9 for rats with tumour (n=15) versus 0.7+/-0.5 for control rats (n=6; P<0.001). These ratios were not significantly affected by the use of adrenaline. Histological analysis showed that five times as many large (>10) and medium-sized (4-9) clusters of microspheres were present within tumour and peritumoural tissue, compared with normal liver. Single microspheres were equally dispersed throughout the tumour, as well as normal liver parenchyma.

The central question to discuss in this review is whether the results of interleukin-2 (IL-2) treatment are still disappointing or again promising. Although in the (recent) past application of high doses of systemically applied rIL-2 has led to some success, the overall results are not as one had hoped. Considering these poor results it seems clear that the application of high systemic doses rIL-2 was not a good choice. IL-2 has been used more or less as a chemotherapeutic compound in the highest tolerable dose. This has led to a great number of unwanted toxic side-effects. In addition, these doses mainly stimulated nonspecific lymphokine-activated killer activity through low-affinity IL-2 receptors, which does not lead to systemic immunity. On the other hand, several groups have shown that application of intratumoral low doses of IL-2 can be highly effective against cancer and without toxic side-effects. Significant tumor loads constituting up to 6% of the total body weight of a mouse were eradicated after treatment with low-dose rIL-2 given locally. Furthermore local treatment can lead to eradication of a tumor at a distant site. This type of therapy is effective in many systems namely against different tumor types in mice, hepatocellular carcinoma in guinea-pigs and vulval papilloma and carcinoma and ocular carcinoma in cattle. Low-dose IL-2 is very effective in experimental animals if it is given relatively late after inoculation of the tumor cells. In other words, it seems necessary that some sort of immune reaction has started or is developing before low doses of rIL-2 effectively stimulate it. In fact there is strong evidence that T lymphocytes, both CD4+ and CD8+ cells, are directly involved in the process leading to induction of specific immunity. In our opinion rIL-2 therapy should therefore aim at the stimulation of such (originally weak) specific immune reaction. Under these conditions also systemic immunity can be induced. In conclusion, application of rIL-2 as a modality for cancer treatment is still promising. High priority should be given to a further delineation of the mechanisms involved after local application. The method of giving IL-2 systemically in the highest tolerable dose should be abandoned. Specific stimulation of the immune system by low-dose rIL-2 is a much more promising option.

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This study shows that local tumor treatment with low-dose recombinant interleukin-2 (IL-2) can mediate rejection of a large distant solid tumour. When SL2 lymphoma cells were injected intraperitoneally (i.p.) in syngeneic DBA/2 mice on day 0.70% of these mice were cured by daily i.p. injections with 20,000 units IL-2 on days 10-14. After injecting mice with SL2 both i.p. and subcutaneously (s.c.) on the flank. 50% of the mice treated i.p. with low-dose IL-2 rejected both the i.p. tumour and the large distant s.c. tumour. In contrast, i.p. IL-2 treatment on days 10-14 cured fewer than 10% of the mice bearing only a s.c. SL2 tumour. The described IL-2 immunotherapy also caused systemic tumour rejection in mice bearing both ascitic and solid P815 mastocytoma. Thus it was shown that low-dose IL-2 can induce systemic tumour rejection, when injected at a site of tumour growth. Interleukin-2-induced rejection of s.c. SL2 tumour was highly specific, as mice that were rejecting i.p. and solid s.c. SL2 lymphoma did not reject solid P815 mastocytoma, which was injected s.c. simultaneously on the other flank. Furthermore, solid s.c. tumours consisting of mixtures of SL2 and P815 were not rejected in mice that rejected i.p. SL2 or P815. We conclude that intratumoral injections of low-dose IL-2 can enhance an ongoing weak immune reaction against the tumour resulting in systemic tumour rejection.

Transforming growth factor Pl (TGFP1) and cisplatin induce apoptosis (programmed cell death, PCD) in human erythroleukemia K562 cells in an additive manner. After PCD was induced in K.562 cells, analysis of phospholipid composition, fatty acids and cholesterol content in their membranes showed a decrease in phosphatidylethanolamine and an increase in phosphatidylserine, cardiolipin and phosphatidic acid. Moreover, cisplatin but not TGFPl enhanced sphingomyeline levels in apoptotic cells, whereas TGFPl increased the amount of linoleic acid and, more remarkably, of cholesterol. The combination TGFPl fcisplatin produced membrane changes similar to those provoked by each inducer individually. Furthermore, the specific activities of 5-lipoxygenase and cytosolic phospholipase A,, both modulating the physical properties of membranes and membrane-lipid-mediated intracellular signalling, were enhanced by treatment with TGFPI or TGFP1 +cisplatin. These findings highlight the profound changes in cell membranes during the biochemical events of the apoptotic pathway.Keywords: programmed cell death ; biomembrane ; cholesterol ; lipoxygenase ; phospholipase A,.The mechanism of apoptosis (programmed cell death, PCD) remains to be fully elucidated. Despite the large array of inducers and effectors of apoptosis, the morphological features of PCD are highly conserved, suggesting a common sequence of final events. Even though the most defining parameters of apoptosis are nuclear changes, another morphological hallmark of apoptosis is the cell shrinkage associated with membrane blebbing [l, 21. Several PCD pathways require signal-transduction systems based on membrane receptors [Z] and membranederived lipid precursors of second messengers [3]. While the role of membranes in cell injury has been long recognized [4], major modifications should be expected in membranes of cells undergoing apoptosis, which might allow their specific recognition and elimination by macrophages [5].In the following study, we investigated the changes in membrane lipid composition during the induction of PCD in human erythroleukemia K.562 cells. Transforming growth factor PI (TGFPI) and/or cisplatin were used to induce apoptosis. TGFPl induces PCD in several cell lines [6, 71 by interacting with specific receptors on the cell surface [S]. Cisplatin, however, forces Abbreviations. PCD, programmed cell death ; TGFb1, transforming growth factor Dl ; sPLA,, secretory phospholipase A,; cPLA,, cytosolic phospholipase A, ; d,Ach, arachidonic acid; 5-HPA4Ach, 5-hydroperoxyarachidonic acid; G C N S , gas chromatography-mass spectrometry.Enzymes. Lipoxygenase (EC 1.13.11.12); phospholipase A, (EC 3.1 .I .4). cells into apoptosis [9] by forming complexes with nuclear DNA [lo]. We also assayed the activities of membrane-related enzymes in apoptotic cells, namely lipoxygenase and phospholipase A,. Several lipoxygenases are able to directly oxygenate biological membranes, introducing peroxides in the lipid bilayer [ l l -131. In particular, 5-lipoxygenase plays a role in ...