Inflammatory cells in solid murine neoplasms. II. Cell types found throughout the course of Moloney sarcoma regression or progression

Radiotherapy as a Backbone for Novel Concepts in Cancer Immunotherapy

Radiation-induced immunogenic cell death has been described to contribute to the efficacy of external beam radiotherapy in local treatment of solid tumors. It is well established that radiation therapy can induce immunogenic cell death in cancer cells under certain conditions. Initial clinical studies combining radiotherapy with immunotherapies suggest a synergistic potential of this approach. Improving our understanding of how radiation reconditions the tumor immune microenvironment should pave the way for designing rational and robust combinations with immunotherapeutic drugs that enhance both local and systemic anti-cancer immune effects. In this review, we summarize irradiation-induced types of immunogenic cell death and their effects on the tumor microenvironment. We discuss preclinical insights on mechanisms and benefits of combining radiotherapy with immunotherapy, focusing on immune checkpoint inhibitors. In addition, we elaborate how these observations were translated into clinical studies and which parameters may be optimized to achieve best results in future clinical trials.

Perspectives: Neutrophil-to-lymphocyte Ratio as a Potential Biomarker in Immune Checkpoint Inhibitor for Non-Small-Cell Lung Cancer

There is a rising need for optimal biomarkers to better tailor treatments for patients with cancer in the era of immunotherapy. In addition to programmed death-ligand 1 (PD-L1) and tumor mutation burden (TMB), neutrophil-to-lymphocyte (NLR) is regaining interest as a biomarker in immunotherapy for its availability, accessibility, and reproducibility. High NLR, according to different thresholds, is consistently reported to correlate with poor prognosis in different treatments in several cancers. Yet, most data come from retrospective analysis, and proof of mechanism and principle evaluations are limited. Prospective studies or adequately sized retrospective analyses of prospectively collected data are required to best assess its role in clinical practice. Moreover, effective myeloid or neutrophil modulators in tumor microenvironment can potentially contribute as a new therapeutic strategy. This perspective will summarize our current knowledge and will discuss where we stand now and propose future directions.

Neutrophil cathepsin G, but not elastase, induces aggregation of MCF-7 mammary carcinoma cells by a protease activity-dependent cell-oriented mechanism

We previously found that a neutrophil serine protease, cathepsin G, weakens adherence to culture substrates and induces E-cadherin-dependent aggregation of MCF-7 human breast cancer cells through its protease activity. In this study, we examined whether aggregation is caused by degradation of adhesion molecules on the culture substrates or through an unidentified mechanism. We compared the effect of treatment with cathepsin G and other proteases, including neutrophil elastase against fibronectin- (FN-) coated substrates. Cathepsin G and elastase potently degraded FN on the substrates and induced aggregation of MCF-7 cells that had been subsequently seeded onto the substrate. However, substrate-bound cathepsin G and elastase may have caused cell aggregation. After inhibiting the proteases on the culture substrates using the irreversible inhibitor phenylmethylsulfonyl fluoride (PMSF), we examined whether aggregation of MCF-7 cells was suppressed. PMSF attenuated cell aggregation on cathepsin G-treated substrates, but the effect was weak in cells pretreated with high concentrations of cathepsin G. In contrast, PMSF did not suppress cell aggregation on elastase-treated FN. Moreover, cathepsin G, but not elastase, induced aggregation on poly-L-lysine substrates which are not decomposed by these enzymes, and the action of cathepsin G was nearly completely attenuated by PMSF. These results suggest that cathepsin G induces MCF-7 aggregation through a cell-oriented mechanism.

Cathepsin G induces cell aggregation of human breast cancer MCF-7 cells via a 2-step mechanism: catalytic site-independent binding to the cell surface and enzymatic activity-dependent induction of the cell aggregation

Neutrophils often invade various tumor tissues and affect tumor progression and metastasis. Cathepsin G (CG) is a serine protease secreted from activated neutrophils. Previously, we have shown that CG induces the formation of E-cadherin-mediated multicellular spheroids of human breast cancer MCF-7 cells; however, the molecular mechanisms involved in this process are unknown. In this study, we investigated whether CG required its enzymatic activity to induce MCF-7 cell aggregation. The cell aggregation-inducing activity of CG was inhibited by pretreatment of CG with the serine protease inhibitors chymostatin and phenylmethylsulfonyl fluoride. In addition, an enzymatically inactive S195G (chymotrypsinogen numbering) CG did not induce cell aggregation. Furthermore, CG specifically bound to the cell surface of MCF-7 cells via a catalytic site-independent mechanism because the binding was not affected by pretreatment of CG with serine protease inhibitors, and cell surface binding was also detected with S195G CG. Therefore, we propose that the CG-induced aggregation of MCF-7 cells occurs via a 2-step process, in which CG binds to the cell surface, independently of its catalytic site, and then induces cell aggregation, which is dependent on its enzymatic activity.

Induction of multicellular 3-D spheroids of MCF-7 breast carcinoma cells by neutrophil-derived cathepsin G and elastase

In tumor metastasis, multicellular aggregates of tumor cells form and disseminate into the blood or lymph vessels from the tumor mass, following the formation of tumor cell emboli in distant vessels. However, the mechanism by which aggregates form in the tumor mass is unknown. Neutrophils often exist in tumors and are considered to affect tumor development. We observed that neutrophils had the capacity to induce the aggregation of MCF-7 human breast carcinoma cells adhering to culture substrates. When MCF-7 cells were cultured with rat inflammatory neutrophils, the soluble fraction of their lysate, and the conditioned medium of neutrophils stimulated with N-formyl-Met-Leu-Phe plus cytochalasin B, multicellular aggregates formed within 16 h, and tightly aggregated 3-D spheroids formed when the cultures were prolonged. The spheroid-inducing reaction was reversible and energy-dependent. The MCF-7 cells induced to aggregate by the neutrophil extract showed growth potential, although the growth rate of the cells was slightly reduced. The aggregation was dependent on E-cadherin, because the spheroids dispersed into isolated cells on incubation with EGTA or anti-E-cadherin antibody following pipetting. The aggregation-inducing activity in neutrophils was completely inhibited by soybean trypsin-chymotrypsin inhibitor. Moreover, the commercially available human neutrophil elastase and cathepsin G induced the aggregation of MCF-7 cells and formation of spheroids. The proteases secreted by infiltrated neutrophils in tumors are implicated in the dissemination of tumor aggregates from primary tumor sites.

Effects produced by Royal Jelly on haematopoiesis: relation with host resistance against Ehrlich ascites tumour challenge

Royal jelly (RJ) was shown to exhibit immunomodulatory properties, although its biological activity is still unclear. In order to elucidate the mechanism whereby RJ activates the immunological system, we examined the role of this substance on the haematopoietic response of Ehrlich ascites tumour (EAT)-bearing mice. Our results demonstrated that RJ prevented the myelosupression induced by the temporal evolution of the tumour and abrogated the splenic haematopoiesis observed in EAT-bearing mice. The stimulating effect of RJ was also observed in vitro on the multipotent bone marrow stem cells, evaluated by the long-term bone marrow cultures (LTBMCs). The study of survival clearly showed the antitumour activity of RJ. Treatment was given prophylactically for 20 days and therapeutically for 3, 8 and 13 days. Except for the treatment with the lower dose of 500 mg/kg, given for 23 days, all the other dose schedules were able to prolong survival. A more effective antitumoural response was observed with the more prolonged treatment regimen. In this regard, the administration of RJ for 33 days produced the highest protection reaching an extension of survival at about 38%, 71% and 85% for the doses of 500, 1000 and 1500 mg/kg, respectively, whereas with the 23 and 28 days treatment schedules, survival increased at a rate of 19% and 23%, respectively, and comparable results were found among the effective doses of RJ. Increased survival rate might be related to the decreased Prostaglandin E2 (PGE2) levels observed in EAT-bearing mice after RJ treatment. These results point to RJ as a promising modifier of biological response leading to myeloprotection and antitumour activity.

Studies on inflammatory response induced by Ehrlich tumor in mice peritoneal cavity

In the present study we investigated the inflammatory response induced by the inoculation of Ehrlich tumor cells (EAT) into the peritoneal cavity of mice. It was found that after inoculation of 10(3) EAT cells, the number of peritoneal leukocytes remained unchanged till the sixth day. Subsequently, the number of cells increased as a consequence of tumor growth. EAT cells did not induce influx of PMN leukocytes till six days after tumor implantation, but a significant influx was observed on the tenth day. Inoculation of the tumor cells did not induce production of H2O2 by peritoneal cells at any time examined and induced low levels of macrophage spreading only until the third day after tumor implantation but not later on. The levels of thromboxane in the peritoneal cavity were not affected by the presence of the tumor, whereas prostaglandin E2 levels were significantly increased at all times examined. The biological significance of these results on the evolution and escape of the tumor from host defense mechanisms is under investigation.

Inhibition of Ehrlich ascites tumor in vivo by PAF-antagonists

Several lines of evidence support that PAF modulates the inflammatory and immune responses, and that tumors may inhibit both these processes. In the present study we analysed the effect of PAF antagonists on the growth of Ehrlich Ascites Tumor (EAT) in vivo. Mice were inoculated intraperitoneally with 1 x 10(3) EAT cells and the tumor growth evaluated by counting the number of peritoneal cells, 1,6 and 10 days after tumor implantation. BN 52021 was administered intraperitoneally, intravenously or subcutaneously once or twice a day, at 1.0, 2.5, 5.0 and 20.0 mg/kg. Control animals received 0.1 ml of the vehicle in the same schedule. It was found that i.p. and i.v. administration of BN 52021 (5 mg/kg, twice a day) significantly inhibited EAT growth (80.8% and 56.0% respectively). Other routes and doses were less effective. Another PAF antagonist, SRI 63441 (5 mg/kg, i.p., twice a day) also inhibited EAT growth (80.4%). The BN 52021 added to EAT cells in culture, at concentration of 10(-3) and 10(-4) M, did not affect the viability and proliferation of tumors cells. In an attempt to understand the mechanism of this inhibition, we analyzed the peritoneal macrophages for spreading ability and H2O2 release. It was found that 24 h after tumor implantation there was an increase in the spreading ability of peritoneal macrophages (75%) and that, as the tumor grew, the spreading index fell to control levels ( less than 10%). (5 mg/kg/twice a day) the spreading remained elevated (50-60%) at all the times examined. Release of H2O2, measured by horseradish peroxidase-phenol red oxidation, was below detectable levels throughout tumor growth.(ABSTRACT TRUNCATED AT 250 WORDS)

Membranes from T and B lymphocytes have different patterns of tyrosine phosphorylation

Membrane fractions isolated from mouse and rat spleen expressed substantial tyrosine-specific protein kinase activity. Phosphotyrosine (P-Tyr) accumulation in endogenous membrane substrates was stimulated by vanadate or nonionic detergents. When in vitro phosphorylation was carried out at 0 degree C in the presence of 1 mM Mn2+ and Triton X-100, P-Tyr constituted up to 40-50% of the total phospho amino acid. Polyacrylamide gel electrophoresis showed that membranes from mixed lymphocyte populations have four major P-Tyr-containing proteins. Whereas nonionic detergents were potent stimuli for P-Tyr accumulation in all four substrates, tyrosine phosphorylation of two of these (p61 and p55) was markedly dependent on vanadate. These two substrates were present in membranes from surface Ig-bearing splenic lymphocytes purified by affinity chromatography and Raji, a human B-lymphoblastoid cell line. P-Tyr accumulation in the two other substrates observed in splenocyte membranes (p64 and p58) was much less dependent on vanadate. p64 and p58 were phosphorylated in membranes from mouse thymocytes and human and mouse T-lymphoma cell lines, while p61 and p55 were not. Thus it appears that in both murine and human lymphocytes, p64 and p58 served as T-cell-specific substrates, while p61 and p55 were specifically associated with B lymphocytes. Moreover, these distinct P-Tyr substrate patterns were conserved in some neoplastic cell lines derived from B and T cells.

Gamma interferon interferes with the negative regulation of macrophage activation by prostaglandin E2

Activation of mouse macrophages for tumor cell killing is negatively regulated by prostaglandin E2 (PGE2). The effect of this hormone is to shut off cytolytic activity that is expressed as a consequence of activation. A lymphokine in the culture supernates of concanavalin A stimulated spleen cells has been shown to change the sensitivity of activated macrophages to the negative regulatory effects of PGE2, thereby maintaining activation, as manifested by the continued expression of tumor cell killing by these cells. Using a highly specific polyclonal antiserum and gamma interferon produced either by a T-cell hybridoma or by recombinant DNA technology we show here that one lymphokine responsible for mediating the maintenance effect is gamma interferon.

Relationship of tumor leucocytic infiltration to host defense mechanisms and prognosis

The interface between the tumor and the host is often the site of leucocytic infiltration. We will examine the idea that the infiltrating leucocytes of human and experimental tumors are components of the host immunological defense against the tumor, and that the presence of the infiltrate is a marker of favorable prognosis. Leucocytes could infiltrate tumors because of an active immune response, either nonspecific or specifically directed to tumor-associated antigens. Leucocyte influx may also occur because of chemotactic factors secreted by the tumor cells. Some tumors release factors which enhance vascular permeability and permit improved access by leucocytes to the tumor focus. The consequences of leucocytic infiltration include tumor cell cytolysis, cytostasis, or stimulation of proliferation. The present state of our knowledge of the interactions between tumor cells and infiltrating leucocytes precludes broad generalization of mechanisms. Further study will probably reveal that the mechanisms are diverse, and that there are some systems in which immune interactions occur at this interface and others in which they do not.

Production of T-cell lines with inhibitory or stimulatory activity against syngeneic tumors in vivo. A preliminary report

We obtained Thy-I-positive cells directly from growing methylcholanthrene-induced (MCA-1510) sarcomas using fluorescence-activated cell sorting, then cultured these lymphocytes in medium containing Interleukin-2 and tested their activity in vivo against various MCA-sarcoma lines with the Winn assay. We found that cultured T cells from small MCA-1510 tumors (17 days after transplantation) significantly inhibited the growth of that particular sarcoma, but not of three other MCA-tumor lines tested, while cultured T cells from large MCA-1510 sarcomas (41 days after transplantation) significantly enhanced the growth of that tumor, but not of an unrelated tumor, MCA-1460. The former cells were primarily Lyt-1+, 2+ while the latter were primarily Lyt-1+, 2+.

Canine transmissible venereal sarcoma: distribution of T and B lymphocytes in blood, draining lymph nodes and tumours at different stages of growth

The levels of T, B and null lymphocytes in the peripheral blood, draining lymph nodes, and tumour masses at different growth stages in dogs transplanted with canine transmissible venereal sarcoma (CTVS) were determined by immunofluorescence techniques. The tumours were classified at excision into "progressor", "steady state", and "regressor" stages of growth. The percentage of B cells in the lymphocytes infiltrating into the progressively growing tumours (n = 10, 37.3 +/- 7.4%) was significantly higher (P less than 0.025) than that in regressing tumours (n = 21, 26.1 +/- 1.9%). In contrast, the percentage of T cells in the lymphocytes infiltrating into the regressing tumours (n = 21, 61.2 +/- 2.6%) was significantly higher (P less than 0.005) than that in the progressively growing tumours (n = 10, 34.0 +/- 5.1%). The tumours at the steady-state growth stage (n = 9) had 50.8 +/- 5.7% infiltrating T-cells, which was significantly higher (P less than 0.005) than the progressors and lower (P less than 0.005) than the regressors. The percentage of null cells of progressors (n = 10, 26.0 +/- 6.9%) was significantly (P less than 0.025) higher than in regressors (n = 21, 13.5 +/- 2.9%). The draining lymph nodes of progressor dogs (n = 5) had significantly fewer (P less than 0.025) B cells (8.2 +/- 2.3%) than in normal (n = 5, 16.1 +/- 3.1%), regressors (n = 12, 19.1 +/- 1.7%) and steady-state dogs (n = 5, 15.8 +/- 2.6%). Although there was slight lymphopenia and fluctuation of null cells, no significant differences in T- and B-lymphocyte levels were noted in the peripheral blood of the tumour dogs (n = 44) studied.

Tumour-cell susceptibility to cytotoxic or cytostatic effector cells in vitro and the regulation of tumour-cell growth in vivo

Tumour-cell growth in lung nodules after i.v. transfer to sublethally irradiated mice has been followed after adoptive transfer of different populations of lymphoid cells. Spleen cells deliberately immunized in vitro and in vivo against stimulator cells bearing embryo-associated antigens and which are cytostatic in vitro for targets bearing such antigens, can diminish the number of lung nodules found after i.v. transfer. In contrast, cytotoxic (in vitro) spleen cells, while capable of diminishing local (s.c.) growth of tumour cells, cannot control systemic tumour growth. Within a given solid tumour mass, the subpopulations resistant to cytostatic effector cells in vitro are the ones most likely to produce lung colonies after adoptive transfer in vivo, though they show no more local (s.c.) growth than to cytostatic-sensitive cells in vivo.

Inhibition of cell proliferation rather than of cell lysis as a measure of immune reactivity in embryo-antigen-challenged mice

An assay system is described in which effector cells added along with suitable target cells inhibit, in a quantitative fashion, the subsequent uptake of 3H-thymidine by those target cells. Effector cells active in this assay, using embryonic fibroblast cells as targets, develop spontaneously in cultures of mouse lymphoid cells, but are apparently different from those described earlier by investigators of activity in cytotoxic assays. Further evidence is presented to show the development of spleen-derived effector cells with cytostatic activity (for embryonic fibroblast target cells) in mice during the course of normal pregnancy, or growth of spontaneously appearing mammary adenocarcinomas. Indeed, such effector cells can also be found within the growing solid mass itself. Different populations of tumour cells isolated from a solid tumour apparently differ in their susceptibility to growth inhibition by tumour-bearer-derived cytostatic effector cells, a phenomenon which may be related to metastatic spread of tumour cells.

Characterization of lymphocyte subsets in spontaneous mouse mammary tumors and host lymphoid organs

The subsets of small lymphocytes (surface Igm-positive or B, Thy-I-positive or T and "double-negative" or null) appearing within spontaneous mammary tumors of C3H retired breeder female mice and in various lymphoid organs of the host at different stages of tumor development were characterized directly using a radioautographic method. Tumor-bearing mice showed early transient splenomegaly and progressive atrophy of the thymus. The proportion of T small lymphocytes increased with tumor age within the tumor and in the spleen, blood and thymus; then, except in the spleen, these proportions declined again by 8 weeks of tumor growth. The incidence of B small lymphocytes showed no change in the tumor or thymus; there was an increase in the blood after 3 weeks, and a small decrease in the spleen after 7 weeks. At all the sites examined, the proportion of null small lymphocytes declined from an initial high level observed in the elderly tumor-free control mice, and then recovered to control levels after 7 weeks. The absolute numbers of T and null cells in the spleen changed in parallel to their proportions, while splenic B-cell numbers increased at 1-3 weeks. In the thymus the absolute numbers of all subsets decreased, with a late recovery of null cell numbers. Age-matched control mice showed higher proportions of null cells in the spleen, blood and thymus, and lower proportions of T cells in the blood and spleen, than did young normal mice. This spontaneous tumor appears to be characterized by an increase in T cells, rather than in null cells, as observed for rapidly growing transplanted tumors. The null cell rise in the present case takes place before the clinical appearance of tumors. In both cases, however, tumor-infiltrating B cells exhibited low levels of surface Ig, possibly related to a low level of maturation. The functional significance of these findings remains to be determined.

Metrizamide gradient purification of mouse tumor cells

A one-step isopycnic density gradient centrifugation procedure is described for purification of highly viable and homogeneous tumor cells from a variety of solid mouse tumors. Mechanically suspended cells are layered onto preformed continuous gradients of medium 199-buffered 7--33% metrizamide (density range 1.05--1.20 g/cu. cm) isoosmotic with mouse plasma and centrifuged for 30 min. Large numbers of tumor cells, generally 85--95% viable and free from 80--95% of contaminating host lymphoid and phagocytic cells and erythrocytes, were consistently recovered from fractionated thymomas, melanomas, and fibrosarcomas. By a variety of criteria, cell surface and other biological properties of gradient-purified tumor cells were normal.

Cytocidal activity and proliferative ability of macrophages infiltrating the EMT6 tumor

The EMT6 mouse tumor was selected for use in the study of cytocidal activity and proliferative ability of infiltrating macrophages because of its high plating efficiency when explanted to culture. The plating efficiency for cells directly plated in culture from the tumor was 28 +/- 9.3%, irrespective of the size of the tumor. Of the adherent cells derived from the tumor, the fraction that was macrophages increased from 27% at 7 days to 47% at 28 days after initial injection. Time-lapse cinemicrography was used to directly observe adherent cells derived from the tumor, and macrophages were found to be cytocidal. When grown in the presence of L-cell conditioned medium no macrophage colonies were found when cultures were established from untreated mice even though most tumor cell colonies contained macrophages. When mice were first treated with 0.8 mg BCNU prior to establishment of the cultures, in order to reduce the frequency of colony-forming tumor cells, approximately half the colonies found contained only macrophages. These results show that macrophages in this tumor are cytocidal and capable of proliferation.

Response of tumour-related and normal lymphocytes to antigens on fibroblasts from embryos of varying age

The in vitro cytotoxic immune response of spleen lymphocytes from primiparous and tumour-related mice to embryonic cells from embryos of varying age and tumour cells has been investigated. The results indicate that lymphocytes from both primiparous and tumour-related (i.e., tumour-bearing or tumour-excised) animals give a response which is greater than that from cells from control mice ("virgin cells"). Moreover, in this putative anamnestic response the immune cells detect antigenic differences in the cell populations of embryos of varying age, which are not as readily demonstrable when cytotoxicity is derived from virgin cells. As a further indication of the in vivo priming to embryo-assoicated antigens, the data show that the precursors of cytotoxic cells apparently undergo a blastogenic response in the presence of embryo antigen, and revert to small quiescent cells when antigen is removed, in a way entirely analogous to that described for reactivity of mixed leucocyte cultures to antigens of the major histocompatibility complex. Finally, it seems that in animals immediately after removal of embryonic antigen (and to a lesser degree in virgin or late-embryo-immune mice) there exists a suppressor cell population which inhibits an anti-embryo cytotoxic response far more than an antiallograft response.

Development and persistence of cytolytic T lymphocytes in regressing or progressing Moloney sarcomas

Intratumoral T lymphocytes were recovered sequentially after induction of regressing or progressing Moloney sarcomas in BALB/c mice and were assayed quantitatively for their ability to kill specifically the tumor (MSC) cells used for induction. The cytolytic activities of the two lymphocyte populations described two distinct biphasic kinetic profiles that were similar in amplitude and duration but separated from each other by 4-6 days. In progressing neoplasm, there was a rapidly occuring accumulation of T lymphocytes highly cytolytic for MSC cells. This response, however, was not sustained and disappeared in association with the onset of unchecked tumor growth. In contrast, T lymphocyte cytolytic activity developed more slowly in regressing sarcomas and attained peak levels coincident with the beginning of tumor regression. Similar changes in cytolytic activity characterized T lymphocytes in lymph nodes draining tumors. When cultured in vitro for 4 days, non-cytotoxic T lymphocytes from regional lymph nodes draining progressing sarcomas regained very high levels of cytolytic activity. Such restitution was diminished, however, if MSC cell lysates, macrophages or macrophages fed MSC cell lysates were present during the culture period. These experiments provided presumptive evidence that T lymphocyte-mediated cytolytic activity was lost in progressively growing Moloney sarcomas as a consequence of suppression in vivo of the genesis and/or functional expression of cytolytic T lymphocytes, perhaps by macrophages and/or soluble tumor antigen.

Functional characterization of a stable, noncytolytic stage of macrophage activation in tumors

The state in which macrophages (Mphi) from regressing Moloney sarcomas could kill tumor target cells was a highly labile one which decayed rapidly in vitro. Thereafter, regressor Mphi were noncytolytic. Mphi from several different progressing sarcomas failed to kill, even when challenged with target cells immediately after explantation. Similarly, thioglycollate-induced peritoneal Mphi (TG-Mphi) did not kill. Noncytolygic Mphi derived either from progressing sarcomas or from long-term (up to 96 h) cultures of regressor Mphi were exquisitely sensitive to stimulation by bacterial lipopolysaccharide (LPS); picogram/milliliter amounts induced killing. Similar concentrations of LPS had no demonstrable effect on TG-Mphi. Thus, tumor Mphi generally appeared to have been primed in vivo, with those in regressing sarcomas having additionally acquired cytolytic activity. Inability of progressor Mphi to kill apparently stemmed from lack of, or failure to respond to, the signal needed in vivo to trigger cytolytic activity, rather than the total absence of activation.

Analysis of established human carcinoma cell lines for lymphoreticular-associated membrane receptors

Thirty-one different long-term established human carcinoma culture cell lines were examined for the presence or absence of receptors for the Fc portion of immunoglobulin G (IgG) ("Fc receptors"), the third component of complement (C3 receptors), sheep erythrocytes and mouse erythrocytes. Included in the catalogue of lines tested were adenocarcinoma of the adrenal cortex, colon, rectum, lung, liver, breast and kidney, and carcinomas of the uterine cervix, bladder and vulva. All lines were found to be consistently Fc receptor-negative, as assayed by rosette formation with sheep erythrocytes coated with subhemagglutinating amounts of anti-sheep erythrocyte antibodies, or bovine erythrocytes heavily coated with non-hemagglutinating anti-bovine erythrocyte antibodies. This is similar to results obtained with murine tumors: carcinomas are consistently Fc receptor-negative, while those lines which are Fc receptor-positive are invariably lymphoreticular in nature. The human carcinoma cell lines were also negative for complement (C3) receptors and spontaneous T and B rosette markers. It is proposed that, in most cases, rosette-forming cells found in primary human carcinomas are, as in the mouse or rat, representative of infiltrating non-malignant lymphoreticular cells.

Inflammatory cells in solid murine neoplasms. I. Tumor disaggregation and identification of constituent inflammatory cells

Mechanical and enzymatic methods of disaggregating tumors were studied with the goals of (1) minimizing cell losses while (2) maintaining functional and surface membrane markers needed to objectively identify inflammatory cells (IC)1 in resultant suspensions. Application of the principles and methods described makes accurate estimation of the percentage of each IC type present in neoplasms possible for the first time. Compared to purely mechanical means of disaggregating tumors, all enzyme mixtures tested markedly increased yields of viable cells/g neoplasm. Best results were obtained with a combination of collagenase and a protease of broader substrate range (alpha chymotrypsin, papain, pronase or trypsin). The combination of enzymes that gave the highest yields with the least effect on inflammatory cell markers was trypsin, collagenase and DNAse (TCD). Because mechanical injury appeared to be the greatest single cause of cell loss (the enzymes themselves had little direct effect), potential sources were identified and either eliminated or minimized. With TCD, depending on the tumor system, cell recovery (measured as DNA recovered in cell suspensions) was as high as 50% and yields were as much as 6.9 X 10(8) viable cells/g tumor. Complete disaggregation was not required to obtain representative IC populations from tumor fragments. Neutrophils, eosinophils and mast cells from disaggregated neoplasms were counted in Giemsa stained cytocentrifuge preparations based on their unique morphologic appearances. Macrophages were identified by their capacity to phagocytose zymosan, a function which proved highly resistant to the effect of enzymes. Flourescent microscopic identification of brain associated thymus antigen (BATA) allowed quantification of T lymphocytes, since this marker was virtually unchanged by enzyme exposure. Surface immunoglobulin (Ig) was stripped from B lymphocytes most rapidly by pronase and chymotrypsin, slowly by trypsin and papain, and not at all by collagenase. Ig positive cells therefore could be quantified in suspensions generated by collagenase or very short (20 min) exposure of fragments to trypsin.