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

Two cases of pineal germinoma with granulomatous inflammation

We report two cases of pineal germinoma with remarkable chronic granulomatous inflammation. In the first case, the pineal mass was totally removed via an occipital transtentorial approach as symptoms were due to direct mass effect. In the second case, endoscopic third ventriculostomy and tissue biopsy was performed to alleviate worsening hydrocephalus. Pathological examination of specimens of both cases showed chronic granulomatous inflammation associated with a few germ cell tumor nests, which demonstrated positive staining for placental alkaline phosphatase. Both patients received post-operative craniospinal irradiation with no subsequent neurological deficits. Follow-up magnetic resonance imaging (MRI) of the second case showed an asymptomatic, shrunken residual tumor mass. MRI of the first case showed no residual or recurrent disease. Thus, a pineal mass with unusual features on MRI and chronic granulomatous inflammation on histopathology, should raise the suspicion of germinoma. In cases with symptomatic mass effect, open resection can be considered. In cases with lesser mass effect, conventional therapeutic modalities without resection can achieve a good outcome, as for other germinomas.

Renal cell carcinoma-infiltrating natural killer cells express differential repertoires of activating and inhibitory receptors and are inhibited by specific HLA class I allotypes

Among tumor-infiltrating lymphocytes (TILs) directly isolated from renal cell carcinomas (RCCs), we found substantial numbers of natural killer (NK) cells in most tumor tissues. They could be identified reliably in situ with an antibody directed against the activating receptor (AR) NKp46 that is exclusively expressed by all NK cells. NK-enriched TILs (NK-TILs) showed cytotoxicity against major histocompatibility complex (MHC) class I-negative cell lines. The ability to detect lysis of target cells was dependent on the percentage of NK cells within the TILs, and cytotoxicity was only observed after overnight activation with low-dose interleukin-2 (IL-2). Infiltrating NK cells were found to express various inhibitory receptors (IRs); among these the CD94/NKG2A receptor complex was overrepresented compared to the autologous peripheral blood mononuclear cell (PBMC) population. Other IRs were underrepresented, indicating that NK subpopulations vary in their tumor-infiltrating capacity. IRs expressed by NK-TILs are functional since receptor engagement with MHC class I ligands presented by human leukocyte antigen (HLA)-transfected target cell lines was able to inhibit NK-mediated cytotoxicity. NK-TILs were also able to lyse autologous or allogeneic tumor cell lines in vitro. This activity correlated with low HLA class I surface expression since lysis could be inhibited by interferon (IFN)-gamma-expressing RCC transductants that displayed a higher surface density of HLA class I molecules. Therefore, NK cells infiltrating tumor tissues have an inherent ability to recognize transformed cells, but they require cytokine activation and are sensitive to inhibition by IR ligands.

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.

The prognostic value of natural killer cell infiltration in resected pulmonary adenocarcinoma

OBJECTIVE

Natural cytotoxicity caused by mediated natural killer cells is believed to play an important role in host-cancer defense mechanisms. Immunohistochemically, we have detected natural killer cells in tissue specimens from patients with pulmonary adenocarcinoma and have assessed their clinical characteristics.

METHODS

Using the monoclonal antibody for CD57 specific marker for natural killer cells, we quantified natural killer cell infiltration in 150 patients with pulmonary adenocarcinoma who underwent curative tumor resection to investigate the relationship between natural killer cell counts and clinicopathologic factors and prognosis.

RESULTS

The natural killer cell count was significantly related to the regulation of tumor progression, involving T classification, N classification, and stage (P =.01 for T classification or stage; P =.02 for N classification). A significant difference in the rate of patient survival was detected between those patients whose tumors had either high or low natural killer cell counts in both the overall and stage I groups (P =.0002 for the overall group; P =.049 for the stage I group).

CONCLUSION

These data indicate that natural killer infiltration may contribute to the regulation of tumor progression and that the natural killer cell count can serve as a useful prognostic marker in overall and stage I pulmonary adenocarcinoma.

Immunohistochemical characterization of 'small, lymphoid-like cell populations' within germinomas: immunologic and molecular approaches to diagnosis

Little is known to date about the biological and molecular characteristics of 'small lymphoid cells' within intracranial germinomas. Frozen sections from three germinoma specimens were evaluated immunohistochemically in order to identify phenotypic markers expressed on human lymphoid cells as well as intercellular adhesion molecules. In addition, T-cell receptor (TCR) variable alpha- and beta-chain mRNA expression was analyzed by polymerase chain reaction (PCR). The small cells stained faintly with anti-CD5 in two specimens, but were negative for the T cell specific markers, CD2, CD3, CD7, and CD8. In addition, these cells were weakly positive for CD11b (Mac-1) and CD54 (ICAM-1), but were negative for lymphocyte-specific CD11a (LFA-1) and CD11c (p150,95). No TCR V alpha or V beta gene expression was detected by PCR within these germinoma specimens. The small cells of germinomas with the cytologic appearance of lymphocytes are not derived from T-cells or other lymphocytic lineages.