We have previously reported that transforming growth factor beta (TGF-beta) produced by rat hepatoma cell line KDH-8 cells suppressed the interleukin-2 (IL-2) production of T cells and the tumoricidal activity of macrophages in KDH-8 tumor-bearing rats and that the inhibition of TGF-beta production by low-dose bleomycin restored these activities significantly. In this study, we established three transfectant clones with stable expression of soluble TGF-beta receptor type II (sTRII), namely KT1, KT2 and KT3, and one with an empty vector used as control vector (KV), and then investigated the effects of sTRII on the tumorigenicity of KDH-8 cells and immune responses in syngeneic Wistar King Aptekman/Hok (WKAH) rats. We found that sTRII expressed in sTRII transfectants could abolish growth inhibition of Mv1Lu cells by TGF-beta1 produced by the cells themselves, and that tumor growth of KT2 and KT3 clones in vivo was suppressed significantly compared with that of parent, KV and KT1 clones. Furthermore, we demonstrated that IL-2 production of splenocytes and IL12p40 mRNA expression in tumor tissues were restored in rats inoculated with KT2 and KT3 clones, whereas such restoration was not observed in rats inoculated with parent, KV and KT1 clones. Combined with a low expression of sTRII in KT1 tumor tissues, these results suggest that sTRII may to some extent be able to abolish the tumor-promoting activity of TGF-beta, and imply that sTRII might have a therapeutic effect on TGF-beta-producing tumors.

Effects of a streptococcal preparation, OK-432, on precursors of lymphokine-activated killer (LAK) cells were observed in vivo. Total number of splenocytes and the ratio of asGM1+ cells increased gradually after i.v. administration of OK-432, reaching their peaks at 3 to 4 days. It was found that asGM1+ cells were nonadherent and large in size. There were little differences in the ratios of Thy-1+, Lyt-2+, and L3T4+ cells before and after OK-432 treatment. Mice were injected i.p. with recombinant interleukin 2 (rIL-2) at a dose of 5 x 10(4) U per mouse 4 days after OK-432 administration and LAK activity in their splenocytes was examined using natural killer (NK) resistant EL-4 target cells. Splenocytes in mice treated with both OK-432 and rIL-2 showed higher LAK activity than those in mice treated with rIL-2 alone. In vivo treatment with anti asGM1 antibody prior to rIL-2 injection abolished completely such augmentation of LAK activity in OK-432 treated mice. These results demonstrated that asGM1+ LAK precursor cells induced by OK-432 were effectively differentiated into LAK cells by rIL-2.

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Summary Using an under agarose migration (UAM) assay, we studied lymphokine-activated killer (LAK)-attractant activity in cultured conditioned medium of tumour tissues after chemotherapy as a possible mechanism of enhanced LAK cell accumulation into tumour tissues after chemotherapy. BMT-11 is a fibrosarcoma developed in C57BL/6 mice. The conditioned medium of BMT-11 tumour tissues obtained from mice treated with various anti-cancer drugs had chemotactic activity for LAK cells (LAK-attractant activity). mRNA expression of interleukin (IL)-la, IL-6, IL-8, interferon (IFN)-y, and tumour necrosis factor (TNF)-a was observed in untreated tumour tissues, which were not enhanced by cyclophosphamide treatment. mRNA expression of TGF-,IB was not detected in untreated tumour tissues by reverse transcription-polymerase chain reaction (RT-PCR), but was detected in tumour tissues treated with cyclophosphamide. Recombinant human TGF-,B1 showed LAK-attractant activity at a concentration of 0.1 ng ml-1 and 1 ng ml-', whereas fresh splenocytes were not attracted by TGF-f,1. Anti-TGF-,B1 antibody inhibited LAK-attractant activity in the conditioned medium of tumour tissues treated with cyclophosphamide to approximately 35% that of control at 100 Mg ml -l. These findings indicate that TGF-,13 produced in the tumour tissues of mice treated with anticancer drugs could be a LAK attractant. By a 4 h 51 Cr release assay of natural killer cell-resistant BMT-11 tumour cells, we observed that TGF-,B1 at a concentration from 0.01 ng ml-1 to 10 ng ml-1 did not inhibit LAK activity in an effector phase. Taken together, we suggest that TGF-,B1 produced in tumour tissues after chemotherapy participates in gathering transferred LAK cells and contributes to the therapeutic effects of transferred LAK cells.

With an in vitro static system using HUVEC (human umbilical vein-derived endothelial cells) cultured on type I collagen gel, we investigated the transendothelial migration activities of I1-2 activated killer (LAK) cells. Our results indicate that in comparison with unstimulated T cells, LAK cells exhibit strong transendothelial migration activity, as well as increased adhesiveness to HUVEC. Pretreatment of HUVEC for 24 h with rINF-gamma, rTNF-alpha and rIL-1 beta enhanced the LAK cell migration. The increase in the percentage of migration of LAK cells was greater than that of the percentage of adhesion but significantly less than the increase in the percentage of migration of resting T cells. The results of blocking studies using mAb strongly suggest that the enhanced migration of LAK cell was probably attributed to nonspecifically increased binding to HUVEC and markedly enhanced chemokinetic activity that was dependent primarily on the LFA-1 molecule. Among LAK cells, there were considerable differences in the migration activities of the various phenotypes. CD8+T-LAK migrated preferentially to CD4+T-LAK. CD16+ NK-LAK showed increased adhesion but somewhat decreased migration activities. However, rINF-gamma treatment of HUVEC for 24 h promoted vigorous migration of CD16+ NK-LAK, which suggests that endothelium regulate the migration of LAK cells. Based on these observations, we proposed that LAK cells, if transferred into tumor feeding vessels, can migrate into tumor tissue in considerable numbers and efficiently make contact with individual tumor cells to produce preferable clinical effects.