Presence and significance of NK cells in glioblastomas

The War Is on: The Immune System against Glioblastoma—How Can NK Cells Drive This Battle?

Natural killer (NK) cells are innate lymphocytes that play an important role in immunosurveillance, acting alongside other immune cells in the response against various types of malignant tumors and the prevention of metastasis. Since their discovery in the 1970s, they have been thoroughly studied for their capacity to kill neoplastic cells without the need for previous sensitization, executing rapid and robust cytotoxic activity, but also helper functions. In agreement with this, NK cells are being exploited in many ways to treat cancer. The broad arsenal of NK-based therapies includes adoptive transfer of in vitro expanded and activated cells, genetically engineered cells to contain chimeric antigen receptors (CAR-NKs), in vivo stimulation of NK cells (by cytokine therapy, checkpoint blockade therapies, etc.), and tumor-specific antibody-guided NK cells, among others. In this article, we review pivotal aspects of NK cells’ biology and their contribution to immune responses against tumors, as well as providing a wide perspective on the many antineoplastic strategies using NK cells. Finally, we also discuss those approaches that have the potential to control glioblastoma—a disease that, currently, causes inevitable death, usually in a short time after diagnosis.

NK cell infiltration is associated with improved overall survival in solid cancers: A systematic review and meta-analysis

The immune landscape of a tumor is highly connected to patient prognosis and response to treatment, but little is known about how natural killer (NK) cells predict overall survival (OS) among patients with solid tumors. We present the first meta-analysis on NK cell infiltration into solid tumors as a prognostic indicator for OS, considering cancer types independently, and together. Samples were collected from 1973 to 2016 with results published between 1989 and 2020. From 53 studies, we found that NK cell infiltration corresponds with decreased risk of death (HR=0.34, 95% CI: 0.26-0.46; p<0.0001). Among studies that investigated the prognostic potential of NK cells in specific regions of the tumor, intraepithelial infiltration was better predictive of OS than NK infiltration in the tumor-adjacent stroma. Generally, NK cell infiltration is lower in advanced-stage and lower-grade tumors; nevertheless, it remains prognostically beneficial. This meta-analysis highlights an important prognostic role of NK cells in solid tumors, but exposes that few studies have considered the contributions of NK cells. Toward NK cell-based immunotherapies, it will be important to understand the conditions under which NK cells can be effective agents of tumor control.

Prognostic role of tumour-infiltrating inflammatory cells in brain tumours: literature review

PURPOSE OF REVIEW

Both primary and metastatic brain tumours pose a significant and unmet clinical need. Immune cells infiltrating the tumour have been shown to affect the clinical course of various extracranial tumour types, but there is little knowledge on the role of tumour-infiltrating immune cells in brain tumours. Thus, the aim of this review was to recapitulate the reports on immune infiltrates in brain tumours and their prognostic significance.

RECENT FINDINGS

Immune infiltrates composed of various lymphocyte subsets and microglia/macrophages are frequently observed in brain tumours; however, their density and prognostic role seem to differ between tumour types. Central nervous system (CNS) metastases, particularly of melanoma, lung cancer and renal cell cancer, commonly show high amounts of tumour-infiltrating lymphocytes and tumour-infiltrating lymphocytes density strongly correlate with patient's overall survival times in patients with CNS metastases. In gliomas and primary CNS lymphomas, some studies also suggest a prognostic role of immune cell infiltration; however, methodological issues such as low sample size and retrospective study designs with heterogeneous patient populations preclude definite conclusions. Meningiomas typically harbour inflammatory infiltrates, but their correlation with the clinical course is unclear because of the lack of studies correlating immune cell infiltrates with outcome parameters.

SUMMARY

The available literature suggests a relevant role of immune infiltrates in the clinical course of some brain tumour types; however, further studies are required to better understand the interaction of the immune system and CNS neoplasms and to explore therapeutic opportunities with immunotherapies such as vaccines or immune checkpoint modulators.

Pediatric Primitive Neuroectodermal Tumors of the Central Nervous System Differentially Express Granzyme Inhibitors

BACKGROUND

Central nervous system (CNS) primitive neuroectodermal tumors (PNETs) are malignant primary brain tumors that occur in young infants. Using current standard therapy, up to 80% of the children still dies from recurrent disease. Cellular immunotherapy might be key to improve overall survival. To achieve efficient killing of tumor cells, however, immunotherapy has to overcome cancer-associated strategies to evade the cytotoxic immune response. Whether CNS-PNETs can evade the immune response remains unknown.

METHODS

We examined by immunohistochemistry the immune response and immune evasion strategies in pediatric CNS-PNETs.

RESULTS

Here, we show that CD4+, CD8+, γδ-T-cells, and Tregs can infiltrate pediatric CNS-PNETs, although the activation status of cytotoxic cells is variable. Pediatric CNS-PNETs evade immune recognition by downregulating cell surface MHC-I and CD1d expression. Intriguingly, expression of SERPINB9, SERPINB1, and SERPINB4 is acquired during tumorigenesis in 29%, 29%, and 57% of the tumors, respectively.

CONCLUSION

We show for the first time that brain tumors express direct granzyme inhibitors (serpins) as a potential mechanism to overcome cellular cytotoxicity, which may have consequences for cellular immunotherapy.

ErbB2/HER2-Specific NK Cells for Targeted Therapy of Glioblastoma

BACKGROUND

Glioblastoma (GBM) is the most common and malignant intracranial tumor in adults and currently incurable. To specifically target natural killer (NK) cell activity to GBM, we employed NK-92/5.28.z cells that are continuously expanding human NK cells expressing an ErbB2-specific chimeric antigen receptor (CAR).

METHODS

ErbB2 expression in 56 primary tumors, four primary cell cultures, and seven established cell lines was assessed by immunohistochemistry and flow cytometry. Cell killing activity of NK-92/5.28.z cells was analyzed in in vitro cytotoxicity assays. In vivo antitumor activity was evaluated in NOD-SCID IL2Rγ(null) (NSG) mice carrying orthotopic human GBM xenografts (6 to 11 mice per group) and C57BL/6 mice carrying subcutaneous and orthotopic ErbB2-expressing murine GBM tumors (5 to 8 mice per group). Statistical tests were two-sided.

RESULTS

We found elevated ErbB2 protein expression in 41% of primary GBM samples and in the majority of GBM cell lines investigated. In in vitro assays, NK-92/5.28.z in contrast to untargeted NK-92 cells lysed all ErbB2-positive established and primary GBM cells analyzed. Potent in vivo antitumor activity of NK-92/5.28.z was observed in orthotopic GBM xenograft models in NSG mice, leading to a marked extension of symptom-free survival upon repeated stereotactic injection of CAR NK cells into the tumor area (median survival of 200.5 days upon treatment with NK-92/5.28.z vs 73 days upon treatment with parental NK-92 cells, P < .001). In immunocompetent mice, local therapy with NK-92/5.28.z cells resulted in cures of transplanted syngeneic GBM in four of five mice carrying subcutaneous tumors and five of eight mice carrying intracranial tumors, induction of endogenous antitumor immunity, and long-term protection against tumor rechallenge at distant sites.

CONCLUSIONS

Our data demonstrate the potential of ErbB2-specific NK-92/5.28.z cells for adoptive immunotherapy of glioblastoma, justifying evaluation of this approach for the treatment of ErbB2-positive GBM in clinical studies.

Role of the systemic immune system in brain metastasis

Metastatic disease in the central nervous system (CNS) is a cause of increasing mortality amongst cancer patients. As with other types of cancer, cells of the systemic immune system play a range of important roles in the development of metastatic lesions in the CNS, both repressing and promoting tumour growth. Recent advances in immunotherapy have changed the emphasis in cancer treatment away from conventional chemotherapy and radiotherapy for certain tumour types. Despite this, our understanding of systemic immune system involvement in CNS metastases remains poor. The blood-brain barrier prevents the majority of diagnostic and therapeutic agents from crossing into the brain parenchyma until the late stages of metastatic disease. Thus, the development of immunotherapy for CNS pathologies is particularly desirable. This review draws together our current understanding in the relationships between CNS metastases and circulating systemic immune cells. We discuss the roles that circulating systemic immune cells may play in the homing of metastatic cells to the perivascular space, and the pro-metastatic and antagonistic roles that infiltrating systemic immune cells may play at sites of metastasis. This article is part of a Special Issue entitled 'Neuroinflammation in neurodegeneration and neurodysfunction'.

Immune genes are associated with human glioblastoma pathology and patient survival

Background

Glioblastoma (GBM) is the most common and lethal primary brain tumor in adults. Several recent transcriptomic studies in GBM have identified different signatures involving immune genes associated with GBM pathology, overall survival (OS) or response to treatment.

Methods

In order to clarify the immune signatures found in GBM, we performed a co-expression network analysis that grouped 791 immune-associated genes (IA genes) in large clusters using a combined dataset of 161 GBM specimens from published databases. We next studied IA genes associated with patient survival using 3 different statistical methods. We then developed a 6-IA gene risk predictor which stratified patients into two groups with statistically significantly different survivals. We validated this risk predictor on two other Affymetrix data series, on a local Agilent data series, and using RT-Q-PCR on a local series of GBM patients treated by standard chemo-radiation therapy.

Results

The co-expression network analysis of the immune genes disclosed 6 powerful modules identifying innate immune system and natural killer cells, myeloid cells and cytokine signatures. Two of these modules were significantly enriched in genes associated with OS. We also found 108 IA genes linked to the immune system significantly associated with OS in GBM patients. The 6-IA gene risk predictor successfully distinguished two groups of GBM patients with significantly different survival (OS low risk: 22.3 months versus high risk: 7.3 months; p < 0.001). Patients with significantly different OS could even be identified among those with known good prognosis (methylated MGMT promoter-bearing tumor) using Agilent (OS 25 versus 8.1 months; p < 0.01) and RT-PCR (OS 21.8 versus 13.9 months; p < 0.05) technologies. Interestingly, the 6-IA gene risk could also distinguish proneural GBM subtypes.

Conclusions

This study demonstrates the immune signatures found in previous GBM genomic analyses and suggests the involvement of immune cells in GBM biology. The robust 6-IA gene risk predictor should be helpful in establishing prognosis in GBM patients, in particular in those with a proneural GBM subtype, and even in the well-known good prognosis group of patients with methylated MGMT promoter-bearing tumors.

Characterization of Immune Cell Infiltration Into Canine Intracranial Meningiomas

Meningiomas are the most common intracranial tumors in dogs. A variety of inflammatory cells have been shown to invade these tumors in people, but little is known about interactions between the immune system and naturally occurring brain tumors in dogs. The purpose of this study was to investigate the presence of a variety of immune cell subsets within canine intracranial meningiomas. Twenty-three formalin-fixed, paraffin-embedded tumor samples were evaluated using immunohistochemistry with antibodies specific for CD3, CD79a, CD18, CD11d (αD), CD45RA, forkhead box P3, and Toll-like receptors 4 and 9. Immune cell infiltration was evident in all samples, with a predominance of CD3+ T cells. Large numbers of CD18+ microglia and macrophages were noted surrounding and infiltrating the tumors, and a subset of these cells within the tumor appeared to be CD11d+. Scattered macrophages at the tumor–brain interface were TLR4+ and TLR9+. Rare CD79a+ B cells were noted in only a small subset of tumors. Lesser numbers of lymphocytes that were CD11d+, CD45RA+, or FoxP3+ were noted in a number of the meningiomas. Although the function of these cells is not yet clear, work in other species suggests that evaluation of this immune cell infiltrate may provide important prognostic information and may be useful in the design of novel therapies.

Real-time profiling of NK cell killing of human astrocytes using xCELLigence technology

We have conducted the first profiling of human Natural Killer (NK) cell mediated killing of astrocytes using xCELLigence technology. The sensitivity and applicability of xCELLigence was compared to lactate dehydrogenase (LDH) release and time-lapsed microscopy to validate the killing events. The xCELLigence technology uses electrical impedance measurements from adherent cells and converts into Cell Index (CI). NK cells did not register any Cell Index signal directly, therefore all changes in Cell Index are a direct measure of astrocyte responses. Astrocytes are insensitive to basal NK cells (non-activated NKs). Whereas NK cells activated by IL-2 prior to culture with targets rapidly kill astrocytes. This observation was supported by all methods of analysis. Using the xCELLigence we were able to monitor the longer term killing profile. This demonstrated that at all NK ratios, death was achieved if given long enough. In addition, the development of the killing phenotype was investigated by inducing lymphokine activated killing with IL-2 in the presence of the target astrocytes. In this paradigm of killing, the xCELLigence was the only assay suitable due to the prolonged time-course required for killing, which required 4-5 days to achieve maximal killing (100%). This suggested that the astrocytes can directly suppress the killing activity of the NK cells. These data highlight the sensitivity, applicability and profiling power of the xCELLigence system and support its use for further investigation of NK-killing of healthy and/or tumourogenic astrocytic cells.

Gammadelta T cells as immune effectors against high-grade gliomas

Almost all individuals diagnosed with glioblastoma multiforme (GBM) will die of their disease as no effective therapies exist. Clearly, novel approaches to this problem are needed. Unlike the adaptive alphabeta T cell-mediated immune response, which requires antigen processing and MHC-restricted peptide display by antigen-presenting cells, gammadelta T cells can broadly recognize and immediately respond to a variety of MHC-like stress-induced self antigens, many of which are expressed on human GBM cells. Until now, there has been little progress toward clinical application, although several investigators have recently published clinically approvable methods for large-scale ex vivo expansion of functional gammadelta T cells for therapeutic purposes. This review discusses the biology of gammadelta T cells with respect to innate immunotherapy of cancer with a focus on GBM, and explores graft engineering techniques in development for the therapeutic use of gammadelta T cells.

Experimental appraisal of the lack of antitumor natural killer cell-mediated immunosurveillance in response to lymphomas growing in the mouse brain

OBJECT

Natural killer (NK) cell-mediated immunosurveillance in the brain is currently obscure, in contrast with the intracerebral immune reaction of cytotoxic T lymphocytes (CTLs) to tumor cells. The goal of this study, in which a controlled tumor model was used, was to investigate a relationship between NK cells and major histocompatibility complex (MHC) Class I gene expression in intracerebral tumor-bearing hosts.

METHODS

A matched set of two cloned tumor cell lines (lymphoma+ and lymphoma-), which differ only in MHC Class I gene expression, was established from the parental YAC-1 cell line (a target widely accepted as being sensitive to murine NK cells). An in vivo rapid elimination assay (REA) was performed using tumor cells labeled with [125I] 5-iodo-2-deoxyuridine to evaluate intracerebral NK cell-mediated defense immunity. There was no difference in the in vitro growth rate and c-myc gene expression between lymphoma+ and lymphoma- cells. An in vitro cytotoxicity assay showed that the lymphoma+ cell line was sensitive to MHC Class I-restricted CTL-mediated lysis, whereas the lymphoma- line was refractory to it. Both were susceptible to NK cell-mediated lysis, comparable to the level shown by YAC-1 cells. Flow cytometry revealed that lymphoma+ reacted positively for cell-surface MHC Class I molecules, whereas lymphoma- had no reaction. Four- to 72-hour REAs, performed using either cell line, disclosed no clearance of radiolabeled tumor cells from the brain in independent groups of untreated and T cell-depleted mice; this contrasted with eradication of radioactivity from the lungs. In NK cell-depleted mice, however, there was no elimination of radiolabeled tumor cells from the brain or lungs. The MHC Class I expression on lymphoma+ cells was enhanced after intracerebral inoculation, rendering them less sensitive to NK cells. By contrast, lymphoma- cells remained negative for cell-surface MHC expression, being sensitive to NK cells and refractory to CTLs after intracerebralinoculation. These results indicate the absence of NK cell-mediated lytic activity in the brain. This allows even NK cell-sensitive tumor cells to escape intracerebral immunosurveillance.

CONCLUSIONS

These experiments have refined the information that the brain may lack NK cell-mediated defense immunity against intracerebrally growing tumors, representing a characteristic aspect of this immunologically privileged organ.

Therapeutic activity of NK cells against tumors

While it is generally accepted that natural killer (NK) cells, by killing tumor cells in the circulation, represent a first line of defense against metastases, their therapeutic activity against established tumors has been limited. In this review, we describe studies to improve the therapeutic effectiveness of activated NK cells in both animal models and clinical trials to better understand the biological problems that limit their effectiveness.

The prognostic significance of intratumoral natural killer cells in patients with colorectal carcinoma

BACKGROUND

Natural killer (NK) cells have a spontaneous cytotoxic capacity-against tumor cells. These cells represent a small proportion of human colon carcinoma-infiltrating lymphocytes. Their prognostic significance in these tumors has yet to be determined.

METHODS

One hundred and fifty-seven patients who each had a colectomy for large bowel adenocarcinoma were studied. No patient received adjuvant therapy. Immunohistochemical stains were performed for NK cells using the monoclonal antibody CD57. The number of NK cells was counted using a MICRON image analyzer. The total area studied for each tumor was 1 cm2. In this area, 50 intratumoral fields of 0.173 mm2 were selected. The degree of NK infiltration was classified as little (< 50 NK cells), moderate (50-150 NK cells), and extensive (> 150 NK cells). The Kaplan-Meier method was used to obtain survival figures. Multivariate analyses were performed using the Cox regression model.

RESULTS

At 5 years, patients with little and moderate NK infiltration showed significantly shorter survival rates (overall and disease free survival) than those with extensive infiltration (P < 0.01). Three significant factors affecting survival were selected in a stepwise fashion in increasing order as follows: TNM stage, NK infiltration, and lymphocytic infiltration. Patients with TNM Stage III disease and extensive NK infiltration showed significantly longer survival rates than those with little or moderate infiltration (P < 0.001). In these patients, multivariate analysis using the Cox regression model identified two significant variables: number of involved lymph nodes and NK cells infiltration.

CONCLUSIONS

In patients with colorectal carcinoma, an extensive intratumoral infiltration of NK cells is associated with a favorable tumor outcome. Intratumoral infiltration of NK cells can be used as a variable with prognostic value, especially in patients with TNM Stage III disease.

T cell-mediated cytotoxicity of human gliomas: a tumor necrosis factor-independent mechanism

Cellular immune effector mechanisms are implicated as potential therapies for malignant gliomas. We have examined the potential for anti-CD3-activated human peripheral blood-derived CD4+ and CD8+ T cells to induce lysis of human glioma cell lines in vitro, the mechanism of action of these cells, and the capacity of the glioma to inhibit the effect. We found that activated CD4+ and CD8+ T cell preparations containing less than 5% natural killer cells could induce significant lysis of the glioma cell line U251, as measured by an 18-hour, but not 5-hour, chromium-51 or lactate dehydrogenase release assay. This effect was not reproduced using recombinant tumor necrosis factor or inhibited with antitumor necrosis factor antibody. Anti-lymphocyte functional antigen-1 and anti-intercellular adhesion molecule antibodies also did not inhibit the effect. Glioma-derived supernatant could inhibit the proliferation of the T cells but not the cytotoxic effect. Human fetal astrocytes were also susceptible to the cytotoxic effect of the activated T cells. These results indicate that activated T cells can induce glioma cytotoxicity via a mechanism independent of tumor necrosis factor. The therapeutic potential of this effector mechanism will depend on its capacity to deliver these cells or their specific effector molecules to the tumor site or to augment the activity of such cells, which accumulate naturally in gliomas.

Role of histocompatibility antigen gene and protooncogene expressions in intracerebral tumorigenicity of mouse neuroblastoma

The role of N-myc, c-src, and major histocompatibility complex (MHC, H-2 in the mouse) class I antigen gene expressions in dimethyl sulfoxide (DMSO)-induced differentiation and intracerebral tumorigenicity was examined using a mouse MNB85 neuroblastoma cell line. A fluorescence-activated cell sorter disclosed cell-surface MHC enhancement by DMSO, causing an increase in cytotoxic T-lymphocyte sensitivity. Southern blot analysis verified a single copy of the proto-oncogenes and MHC deoxyribonucleic acids in both untreated and DMSO-treated MNB85 cells. Northern blot analysis indicated that DMSO treatment induced a decrease in N-myc and an increase in c-src and MHC messenger ribonucleic acids. Nuclear run-off transcription assay revealed down-regulation of N-myc at a posttranscriptional level, contrasted with primary up-regulation of c-src at a transcriptional level. Immunoprecipitation after treatment with enzyme endo-beta-N-acetyl-glycoseamidase H proved that the terminal glycosylation of MHC heavy-chain gene products normally occurs in the Golgi apparatus of MNB85 cells. Intracerebral tumorigenicity assay showed that cells highly MHC-expressed by DMSO were less tumorigenic than untreated cells in association with DMSO-augmented cytotoxic T-lymphocyte susceptibility. These results suggest that proto-oncogenes may be linked to cellular differentiation, while cell-surface MHC gene expression influences intracerebral immunosurveillance.

A morphological and ultrastructural investigation of normal mouse brain tissue after intracerebral injection of tumor necrosis factor

Morphological and ultrastructural changes in normal mouse brain tissue were investigated after intracerebral stereotactic injections of tumor necrosis factor (specific activity: 2.0 x 10(6) U/mg protein) into the right frontal lobe. The mice received either a single infusion or multiple tumor necrosis factor infusions in three different dose groups (10, 100, or 500 U). Compared with sham-treated control mice that received adjusted intracerebral injections of purified albumin, the tumor necrosis factor-treated mice in all dose groups did not show any specific in vivo behavioral abnormalities during the 2 months of study following the infusions. Histological studies revealed hemorrhage attributable to the mechanics of the intracerebral infusions, a thickening of the arachnoid membranes, a reactive gliosis, and neutrophilic and/or mononuclear cell infiltration along the infusion pathway. A local neutrophilic response was prominent 1 day after tumor necrosis factor injection. An immunohistochemical analysis indicated that the mononuclear cell infiltration consisted of lymphocytes and macrophages. Except for the transient neutrophilic infiltration, these histological alterations did not differ from those seen in the sham-treated control groups, and most nonspecific reactive changes disappeared within 8 weeks after the injections. Furthermore, an ultrastructural study showed no apparent pathological changes in the cytoplasmic organelles of neuronal, glial, and endothelial cells in the tumor necrosis factor-injected mouse specimens. These results suggest that the tumor necrosis factor injections caused no specific toxicity and did not alter the parenchymal and stromal cells comprising normal mouse brain tissue.

Immunotherapy of glioblastoma with intratumoural administration of autologous lymphocytes and human lymphoblastoid interferon. A further clinical study

A clinical trial of an immunotherapy which consisted of intratumoural injections of autologous lymphocytes with human lymphoblastoid interferon was evaluated in 31 patients with intracranial glioblastoma. Immunotherapy was performed after stereotactic biopsy or surgical resection. The treatment was tolerated well by all patients. Three patients showed positive response to immunotherapy as documented by transient regression or stabilization of the tumour size on computed tomography. Nevertheless, there is no significant difference in the survival time of the patients treated with immunotherapy and those not treated. We conclude that this immunotherapeutic regimen is not beneficial in patients with glioblastoma when used as single treatment after tumoural biopsy or resection.

Gemistocytic astrocytomas: a reappraisal

Although gemistocytic astrocytomas are considered slow-growing astrocytomas, they often behave aggressively. To clarify the biological and clinical behavior of these rare tumors, the authors retrospectively identified 59 patients with gemistocytic astrocytoma whose tumors were diagnosed and treated between June, 1976, and July, 1989. Three patients who were lost to follow-up review were excluded, as were two whose original slides could not be obtained and three whose tumors were diagnosed at recurrence or at autopsy. The pathological material of the remaining 51 patients was reviewed using two sets of histological criteria. Thirteen patients (Group A) had "pure" gemistocytic astrocytoma, defined as a glial tumor with more than 60% gemistocytes/high-power field and a background of fibrillary astrocytes. Fifteen patients (Group B) had "mixed" gemistocytic astrocytoma, defined as a glial tumor with 20% to 60% gemistocytes/high-power field and a background of anaplastic astrocytes. Twenty-three tumors did not meet these criteria and were excluded from analysis. The median age of the patients was 48.5 years in Group A and 38.3 years in Group B (p less than 0.05). In both groups, the median Karnofsky Performance Scale score was greater than 90%. All patients underwent surgical procedures (four total and 19 partial resections, and five biopsies) and postoperative radiation therapy. The majority also had interstitial brachytherapy, chemotherapy, or both. Ten patients had one reoperation for tumor recurrence and one had two reoperations; other treatments for recurrence included brachytherapy, chemotherapy, and repeat irradiation. All four patients who originally underwent gross total resection are still alive; all five who had a biopsy have died. There was no significant difference in median survival times between groups: 136.5 weeks in Group A (range 10 to 310+ weeks) and 135.6 weeks in Group B (range 31 to 460+ weeks). Analysis of all 28 patients showed a better prognosis for patients less than 50 years of age (185 vs. 36 weeks survival time; p less than 0.001), patients with preoperative symptoms lasting for more than 6 months (228.1 vs. 110.2 weeks survival time; p less than 0.05), and patients with seizures as the first symptom (185.7 vs. 80 weeks survival time; p less than 0.01). Survival time did not correlate with the presence of perivascular lymphocytic infiltration. The authors conclude that the presence of at least 20% gemistocytes in a glial neoplasm is a poor prognostic sign, irrespective of the pathological background. It is proposed that gemistocytic astrocytomas be classified with anaplastic astrocytomas and treated accordingly.

Immunohistochemical study of natural killer cells in tumor-infiltrating lymphocytes of primary intracranial germinomas

A monoclonal antibody against the surface marker IOT-10 of natural killer (NK) cells was used to investigate the presence and distribution of these cells in a series of nine primary intracranial germinomas. In all of these tumors, IOT-10-positive NK cells were found in small numbers, mainly distributed among the tumor cells. The data obtained in the present study suggest that the presence of NK cells in primary intracranial germinomas can be influenced by factors other than the mere quantity of tumor-infiltrating lymphocytes.

Immunohistochemical study of IOT-10 natural killer cells in brain metastases

The presence of NK-cells in a series of 40 metastatic brain tumours has been studied by means of the monoclonal antibody IOT-10. There appeared IOT-10 NK-cells in all tumours studied, but in most cases these cells represented less than 10% of the tumour infiltrating lymphocytes (TIL). In the present series, the obtained data suggest that the number of NK-cells in brain metastases can be influenced by other factors than the mere quantity of TIL.