In vitro generation of cytotoxicity against autologous human tumour biopsy cells

Immunological responses against an autologous human hepatocellular carcinoma cell line

We performed a detailed analysis of immune responses in a hepatocellular carcinoma (HCC) cell line and effector cells obtained from a patient with HCC. We examined the cytotoxic activity of natural killer (NK) cells, lymphokine-activated killer (LAK) cells and cytotoxic T lymphocytes (CTL) against an autologous tumour cell line (SUHC-1) to investigate the immune mechanism of human lymphocytes against HCC cells. Cytotoxic T lymphocytes were induced by co-culturing of peripheral blood lymphocytes (PBL) and SUHC-1 cells, mixed lymphocyte and tumour cell culture (MLTC). The susceptibility of SUHC-1 to NK and LAK cells was similar to that of other allogeneic cell lines, such as K562, PLC/PRF/5 and Mahlavu. Effector cells induced in the primary MLTC had high cytotoxic activity but were not specific for SUHC-1. Cytotoxic T lymphocytes with specific activity against SUHC-1 were induced after PBL were stimulated five times at 7-10 day intervals with SUHC-1 and low-dose recombinant interleukin-2 (rIL-2), suggesting that as the culture progressed, broadly reactive effector cells disappeared and specific effector cells survived. The specific effector cells were identified as CD3+/CD4+ and CD3+/CD8+ T-lymphocyte subsets. The recognition mechanisms of CD3+/CD4+ CTL remain unresolved because the cytotoxicities were not inhibited by anti-CD4 and anti-major histocompatibility complex (MHC) class II monoclonal antibodies (MoAb). Treatment of cells with anti-CD3, anti-CD8 and anti-MHC class I MoAb partially inhibited lysis. These results demonstrated that the T-cell receptor (TCR)/CD3 complex appeared to be involved in SUHC-1 specific antigen recognition and antigen recognition of CD3+/CD8+ CTL was MHC class I restricted.

In vitro tumour cell growth inhibition: a comparative study between allosensitized cytotoxic T lymphocytes and lymphokine activated killer cells

There is general agreement that several distinct subpopulation of lymphocytes, including major histocompatibility complex (MHC)-restricted T lymphocytes and non-restricted natural killer, or lymphokine-activated killer (LAK), cells are active in lysing neoplastic cells. In this study experiments were designed to compare the inhibitory effects of LAK cells and allosensitized cytotoxic T lymphocytes (CTL) on in vitro growth of an Epstein-Barr virus-transformed B-cell line (BSM) and of a HTLV-I producer T-cell line (MT-2). It was found that allosensitized CTL are more efficient at inducing BSM, or MT-2, cell growth inhibition than LAK cells. These results are consistent with the hypothesis that MHC-restricted T effector cells could mediate higher tumour suppressive effects than non-MHC restricted LAK cells.

Factors determining the ability of cytokine-activated killer cells to lyse human ovarian carcinoma targets

Lysis of human ovarian carcinoma cells by natural killer (NK) cells, interferon-alpha activated NK cells (alpha-NK) and lymphokine-activated killers cells (LAK) was studied using both fresh tumor cells and a cell line (HEY) as targets. A clonogenic assay to measure cell kill was more sensitive than a 4-h 51Cr release assay. Both assays showed that single cells were more effectively lysed than were tumor clumps (spheroids). Freshly isolated tumor cells studied in the 51Cr release assay appeared equally susceptible to lysis by LAK cells whether in the form of clumps or single cells, but NK and alpha-NK effectors appeared much less effective in lysing susceptible target cells when they were in clumps. Tumor cells from some patients showed marked resistance to lysis by NK and alpha-NK cells in fractions enriched for clonogenic cells, even when tested in a single cell-suspension, whereas LAK cells were always cytolytic. These data suggest that intrinsic resistance of ovarian carcinoma to lysis by LAKs is unlikely to explain failure of LAK + IL-2 therapy to eradicate tumor in vivo.

Activation and in vitro expansion of tumor-reactive T lymphocytes from lymph nodes draining human primary breast cancers

The feasibility of in vitro activation of lymphocytes from the draining lymph nodes (DLN) of breast cancer patients was examined. Lymphocytes isolated from 48 DLN from 12 patients were examined for their proliferative responses to rIL-2, autologous tumor cells, or rIL-2 plus tumor cells. Three general patterns of cellular responses were observed. Cells from some DLN (17%) were unresponsive to any stimuli. Lymphocytes from 52% of the DLN responded moderately to rIL-2 alone. The combination of rIL-2 and tumor antigen had a synergistic effect on the proliferation of cells from 31% of the DLN assayed. Phorbol dibutyrate and ionomycin plus rIL-2 stimulated expansion of DLN lymphocytes by up to 850-fold after 35 days. These expanded cell populations, as well as those stimulated with antigen plus rIL-2, were predominantly CD3+ and CD16- cells, varying in proportions of CD4+ and CD8+ subsets. Both populations were cytotoxic against autologous tumor, MCF-7, and K562 target cells.

In vitro proliferative responses of spleen lymphocytes from rats bearing progressive or regressive tumors induced by cell variants of a syngeneic colon carcinoma

From one colonic carcinoma chemically induced in the rat, 2 sublines of tumor cells have been cloned, one (PROb) inducing progressive tumors, the other (REGb) generating tumors that regress a few weeks after s.c. injection into syngeneic hosts. Our study was aimed at comparing cellular immunity between animals bearing PROb or REGb tumors. Spleen cells were first tested for in vitro proliferation in response to mitomycin-treated PROb or REGb cells. Only spleen cells from rats injected with REGb cells proliferated significantly when mixed with PROb or REGb cells. The proliferative response induced by REGb cells was considerably higher than the response to PROb cells. When spleen cells from rats bearing REGb tumors were cultured with a mixture of REGb and PROb cells at various PROb/REGb cell ratios, PROb cells significantly suppressed the strong proliferative response generated by the same number of REGb cells alone. REGb-immune spleen cells, after in vitro stimulation by PROb or REGb cells, were not cytotoxic for either cell variant. REGb-immune spleen cells did not differ in their content of T lymphocytes expressing CD4 or CD8 markers when they were stimulated by PROb or REGb cells in vitro, but REGb cells induced a larger number of activated lymphocytes expressing the IL-2 receptor. Our results indicate that, compared to REGb cells, PROb cells are poorer stimulators of proliferation of tumor-immune spleen cells, and that they are able to suppress the proliferative response induced by REGb cells.

Activation of lymphocyte anti-tumour responses in man: effector heterogeneity and the search for immunomodulators

Data continues to accumulate on the immunological reaction against solid human cancers. The evidence at the present time supports the view that rather than being immunologically invisible, tumour cell antigens are recognised by at least three lymphocyte subsets. Helper T cells can be induced to proliferate upon exposure to cells of the autologous tumour and to secrete detectable levels of interleukin 2 (IL-2). Cultured T cell lines and clones can be shown to respond in primed lymphocyte tests not only to autologous tumour cells but also to allogeneic tumour cells of the same histology and anatomic location. Cytotoxic T cells manifest specific reactivity against cells of the autologous tumour which is distinguishable from natural killing (NK) on the basis of specificity and organ distribution. Natural killer cells can lyse freshly isolated autologous tumour cells after purification on Percoll gradients or when activated by IL-2. There is thus a demonstrable heterogeneity of response to human cancer in unseparated lymphocyte populations and at the clonal level. In limiting dilution assays lymphocytes at the tumour site respond more frequently to autologous tumour relative to NK targets. For at least some tumours there is evidence that the expression of auto-tumour reactivity but not NK correlates with the clinical course of the disease and is a favourable prognostic indicator. The finding of these auto-tumour reactivities has important implications for the search for immunomodulating drugs for cancer treatment. However, it must be recognised that the response is heterogeneous and that the immune system comprises multiple interactive elements that exhibit both positive and negative control. Any treatment modality must take this into account and seek to focus on specific activation of the tumour lytic populations or the inhibition of negative regulatory elements as opposed to seeking a more general augmentation of immune reactivity which may, by stimulating suppressor cells, have a counterproductive effect.

Interleukin 2-activated killer cells: generation in collaboration with interferon gamma and its suppression in cancer patients

The generation of lymphokine activated killer (LAK) cells by recombinant IL2 (rIL2) in collaboration with interferon gamma (IFN gamma) was examined in peripheral blood mononuclear cells (PBMC) from patients with malignant tumors of the digestive organs and breast cancer. LAK cytotoxicity could be induced by rIL2 at 10 units/ml in 10 of 12 patients and 20 of 37 using fresh autologous tumor cells and PK-1, an established solid tumor cell line as a target, respectively. Among 34 patients, in which titers of IFN gamma produced were assayed, 12 showed no IFN gamma production. All of these 12 patients had no or extremely low LAK activity, suggesting the correlation of LAK generation with the production of IFN gamma in response to rIL2. LAK induction by rIL2 in PBMC of cancer patients was almost completely inhibited by addition of anti-IFN gamma serum. Depressed LAK generation, which was accompanied by no or low levels of IFN gamma production, was partially restored by addition of exogenous recombinant IFN gamma. These results indicate that LAK induction by rIL2 in cancer patients involves the production of IFN gamma and its interaction with rIL2. The results also suggested the presence of a factor(s) suppressing LAK induction by rIL2 in the serum of cancer patients. Based on these results, the cancer patients could be divided into the following three groups. Group 1, in which the serum suppressor activity was undetectable, had the same level of LAK cytotoxicity in PBMC as healthy controls. Group 2 showed the serum suppressor factor and had the lower level of cytotoxicity in PBMC when cultivated in autologous serum (AS) compared to healthy controls. The depressed LAK induction in AS medium was restored to a normal level in culture with fetal calf serum (FCS) plus rIL2, or by addition of rIFN gamma, or high concentrations of rIL2 in AS medium. The last group (group 3), in which the serum suppressor factor was also found, had the lowest level of cytotoxicity compared to healthy controls. The LAK induction in these patients could not be restored to a normal level by culture in FCS medium, addition of exogenous rIFN gamma or high concentrations of rIL2, suggesting the possibility that the deficit of LAK generation in this group might involve the dysfunction or the lack of IL2 responder cells, in addition to the presence of a serum suppressor factor(s).

Harnessing T-lymphocytes for human cancer immunotherapy

After nearly a decade of controversy, the concept of adoptive immunotherapy in humans is gaining greater acceptance. More recently, investigators have made use immunotherapeutically of T-lymphocytes nonspecifically activated in vitro by a number of agents, including lymphokines, lectins, and autologous and allogeneic tumor cells. The limitations for the investigational use of these highly specialized and "educated" lymphocytes have been the inability to generate sufficient numbers of cells in vitro for adoptive transfer experiments and to sustain their growth over long periods of time. While marked success has been demonstrated over the years in tumor-bearing animal models, the feasibility of such work in humans has been greatly improved by the experimental expansion and maintenance of immune lymphocytes (those exposed to antigenic challenge) in vitro using either highly purified or recombinant, interleukin 2. As a result, large numbers of lymphocytes can successfully be infused into patients, and whole body scans can show migration of these labeled cells to the lung, liver, and spleen. The use of nontoxic, nonspecific activated "killer" lymphocytes is an innovative approach with enormous potential. This report presents discussion of these findings and addresses the issue of an alternative approach to cancer treatment therapy, the in vivo use of cloned cytotoxic T-lymphocytes sensitized to the autologous tumor.

Lymphokine-activated killer cell phenomenon. Lysis of natural killer-resistant fresh solid tumor cells by interleukin 2-activated autologous human peripheral blood lymphocytes

Activation in lectin-free interleukin 2 (IL-2) containing supernatants of peripheral blood mononuclear leukocytes (PBL) from cancer patients or normal individuals resulted in expression of cytotoxicity toward 20 of 21 natural killer (NK)-resistant fresh solid tumor cells tested. Fresh solid tumor cells were resistant to NK-mediated lysis in 10 autologous patients' PBL-tumor interactions, and from 17 normal individuals tested against 13 allogeneic fresh tumors. Culture of PBL in IL-2 for 2-3 d was required for the lymphokine activated killers (LAK) to be expressed, and lytic activity toward a variety of NK-resistant fresh and cultured tumor targets developed in parallel. Autologous IL-2 was functional in LAK activation, as well as interferon-depleted IL-2 preparations. Irradiation of responder PBL before culture in IL-2 prevented LAK development. Precursors of LAK were present in PBL depleted of adherent cells and in NK-void thoracic duct lymphocytes, suggesting that the precursor is neither a monocyte nor an NK cell. LAK effectors expressed the serologically defined T cell markers of OKT.3, Leu-1, and 4F2, but did not express the monocyte/NK marker OKM-1. Lysis of autologous fresh solid tumors by LAK from cancer patients' PBL was demonstrated in 85% of the patient-fresh tumor combinations. Our data present evidence that the LAK system is a phenomenon distinct from either NK or CTL systems that probably accounts for a large number of reported nonclassical cytotoxicities. The biological role of LAK cells is not yet known, although it is suggested that these cells may be functional in immune surveillance against human solid tumors.

Specificity of auto-tumor cytotoxicity exerted by fresh, activated and propagated human T lymphocytes

The specificity of auto-tumor cytotoxicity exerted by patients' T lymphocytes was investigated. Lymphocytes, both activated and non-activated, were used as effectors against freshly separated tumor cells. Activation was achieved by treatment with interferon (Hu-IFN-alphas), stimulation with PHA, co-cultivation with autologous tumor biopsy cells (ATS) and allogeneic lymphocytes (MLC). Of these activation systems, ATS was the most efficient in generating auto-tumor cytotoxicity. In some cases the lymphocytes activated in MLC or treated with PHA also damaged autologous tumor cells, but IFN-pretreatment of the lymphocytes had no such effect. When the ATS- or MLC-activated lymphocytes were propagated with conditioned medium known to contain Interleukin-2, their lytic potential against autologous tumors was maintained. In addition to autologous tumor biopsy cells, the effector populations were also confronted with other targets such as Con A blasts and allogeneic tumor biopsy cells. The latter were lysed by the lymphocytes activated in MLC, but not by the ATS cultures. Thus, on the population level, the ATS was specific for the autologous tumor cells. Cold target competition tests suggested that in the MLC-s the autologous tumor cells were killed by a distinct set of lymphocytes because allogeneic cells (tumor cells or the stimulator lymphocytes), even if killed by the same effector populations, did not compete. Thus, in these cultures the auto-tumor specificity of the lysis was on the level of the effector subset. Therefore, it is likely that, independently of the mode of activation, the auto-tumor lysis is the function of lymphocytes which recognize tumor- or organ-specific antigens on the target cells.

Specific cytotoxicity against autologous tumour and proliferative responses of human lymphocytes grown in interleukin 2

Peripheral blood lymphocytes of cancer patients were sensitized in vitro to autologous tumour cells in mixed lymphocyte-tumour culture (MLTC). Blast cells were isolated on discontinuous Percoll gradients from MLTC which showed significant stimulation of [3H]-thymidine incorporation. Cultured T cells (CTC) were derived from these blasts by growth in conditioned medium containing interleukin-2 (IL-2) and maintained for up to 51 days by repeated feeding with IL-2 and in some cases by addition of irradiated allogeneic blood mononuclear cells as "fillers". These cultures showed specific cytotoxic reactivity against autologous tumour and in only a few cases was natural killing (NK) of K562 cells apparent. Restimulation of CTC with tumour was measured in primed lymphocyte test (PLT). Increased uptake of [3H]-thymidine was found upon stimulation by autologous tumour and allogeneic tumour of the same site and histology but there was no response to non-related tumours or to a panel of allogeneic lymphocytes. No sensitization to autologous HLA-D/DR could be detected by restimulation or cytotoxicity against monocytes in the majority of cases. These data suggest that, by careful selection of sensitised blasts from MLTC, it is possible to obtain CTC with both helper (proliferative) and cytotoxic T cells and that such CTC have specific reactivity against tumour cells. These cellular reagents will be useful in defining the antigenicity of human neoplasms and possibly in therapy.

Cultured human T-cell lines kill autologous solid tumours

Lymphocytes from peripheral blood, lymph node, spleen and tumour of 7 patients with various carcinomas (2 lung, 3 colon, 1 gastric and 1 parotid tumour) were cultured for 15 days in conditioned media containing T-cell growth factor (TCGF; Interleukin 2) after which their cytotoxic activity against autologous tumour (and in some instances, autologous normal) cells and allogeneic tumour targets was evaluated in a short-term 51Cr-release assay. Significant cytotoxicity against autologous tumour targets was detected in at least one effector preparation from all of the patients, under conditions where, in some cases, other autologous cells (normal lung, PHA-transformed lymphocytes) were resistant. This cytotoxicity also generally extended to allogeneic tumour targets, but lysis of K562, a cell line sensitive to natural killing, occurred in only 3 of 19 effector cell preparations. The data are consistent with a polyclonal expansion of cytotoxic T-cells of tumour-bearing patients which includes the amplification of a population recognitive of antigens expressed on autologous neoplastic cells.

Human tumor-lymphocyte interaction in vitro. VII. Blastogenesis and generation of cytotoxicity against autologous tumor biopsy cells are inhibited by interferon

In a high proportion of cases blood lymphocytes from cancer patients cultured with autologous tumor biopsy cells undergo blastogenesis. In addition, cytotoxicity against autologous tumor cells is generated. These autoactivated lymphocytes also kill the highly NK-sensitive K-562 and Molt-4 cells. Addition of interferon (IF) at the initiation of the cultures inhibited blastogenesis and the generation of autologous cytotoxicity. On the other hand, lymphocytes already activated for autologous killing in the mixed cultures were not affected by short-term IF treatment prior to the cytotoxic assay. Lymphocytes cultured alone lose their cycotoxicity against K-562. However, when IF was present in these cultures the lymphocytes were cytotoxic for K-562. In addition, lymphocytes cultured for 6 days under conditions which did not result in activation killing of Molt-4 cells could be induced by short-term incubation of the effectors with IF.

The undefined relationship between tumor antigens and histocompatibility antigens on cancer cells

The data pertaining to the possible relationship between histocompatibility antigens (HA) and tumor-specific transplantation or tumor surface antigen (TSTA or TSA) are reviewed. The HA profiles of certain experimental and human neoplasms have been found to be altered either from the quantitative (increased expression of some antigenic specificities and decreased expression or even lack of other HA) or qualitative point of view (appearance of alien, genetically inappropriate HA). The authors entertain the possibility that the persence of TSTA or TSA on cancer cells may be linked to alterations of the HA profile. Evidence in favour of the idea that tumor antigens may actually to alien MHC products, alien minor HA or modified HA, is reviewed. Findings on structural relationships between TSA and beta2-microglobulin are also summarized. In the authors' opinion, no definitive conclusions can be reached at the present time on the relationship between TSTA or TSA and HA of cancer cells.

Cytotoxicity in vitro of blood lymphocytes from bladder cancer patients and controls to allogeneic or autologous tumor cells derived from established cell lines or short-term cultures

Blood lymphocytes from small groups of patients with transitional-cell carcinoma of the urinary bladder (TCC), clinical controls (CC) or healthy donors (HD) were tested for cytotoxicity in vitro by a 51Cr-release assay. The target cells were either from TCC or control tissue (long-term cultures) or were from short-term TCC cultures, kept in vitro for 10-20 transfer generations. When tested with allogeneic target cells from long-term cultures, TCC patients' lymphocytes tended to be more cytotoxic to TCC targets than to control targets. For the control lymphocytes this was not seen. A large proportion but not all of the cytotoxicity to these target cells was due to immunoglobulin-dependent cellular reactions, probably mediated by natural and disease-related antibodies of the lymphocyte donors, since it was significantly inhibited by Fab-fragments of rabbit antibodies to human immunoglobulin. Moreover, it was, to a large extent, mediated by lymphocytes with Fc-receptors for IgG. For seven of the TCC target cell cultures (two long-term and five short-term) autologous lymphocytes were also available for testing. While two patients were non-reactive to their own tumor cells, five reacted strongly in the autologous combinations. These autologous reactions were immunoglobulin-independent and were mediated by Fc-receptor-negative effector cells. In some instances, autologous cytotoxicity was accompanied by similar reactions to some of the allogeneic TCC targets but not to the allogeneic non-TCC control targets. On the basis of available information on HLA antigens in this material, the pattern of cross-reactions suggests that the cytotoxicity encountered in the autologous and in some of the allogeneic TCC-combinations may be the expression of antibody-independnet but specific CTL-mediated reactions, regulated by HLA. However, at the present stage of the investigation, other mechanisms must also be considered since the target cells from short-term TCC cultures were sometimes lysed by control lymphocytes in immunoglobulin-independent reactions. Whatever the explanation, the results show that the cytotoxicity observed in the in vitro systems is usually the net result of several different types of reaction. Which effector cell types and which mechanism of recognition will predominate in a given lymphocyte/target cell combination is greatly influenced by the nature and origin of the target cells used.

In vitro induction of cytotoxic effector cells against human neoplasms. I. Sensitization conditions and effect of cryopreservation on the induction and expression of cytotoxic responses to allogeneic leukemia cells

Peripheral blood lymphocytes (PBL) from normal human donors were sensitized in vitro against allogeneic human acute myelocytic leukemia (AML) cells by means of an unidirectional mixed lymphocyte-tumor cell culture (MLTC) technique. The cytotoxic responsiveness of the sensitized lymphocytes, as determined in vitro by the 51Cr-release assay, varied among individual lymphocyte donors and was greatly dependent on the sensitization culture conditions. Induction of cytotoxic effector cells was augmented appreciably by adding to the cultures minute amounts of the immunopotentiating agent MER-BCG. Responding lymphocytes and stimulating leukemia cells cryopreserved for several weeks in liquid nitrogen were as effective as fresh cells in generating effector lymphocytes; the cytotoxic capacity of already sensitized lymphocytes was fully retained by cryopreservation. The implications of these findings for possible clinical employment of in vitro sensitized lymphocytes in adoptive immunotherapy of cancer are discussed.