Relation of H-2 expression on murine RCT(+) sarcoma cells to lung colonization and sensitivity to NK cells

Prospects for NK Cell Therapy of Sarcoma

Simple Summary

Sarcomas are a group of aggressive tumors originating from mesenchymal tissues. Patients with advanced disease have poor prognosis due to the ineffectiveness of current treatment protocols. A subset of lymphocytes called natural killer (NK) cells is capable of effective surveillance and clearance of sarcomas, constituting a promising tool for immunotherapeutic treatment. However, sarcomas can cause impairment in NK cell function, associated with enhanced tumor growth and dissemination. In this review, we discuss the molecular mechanisms of sarcoma-mediated suppression of NK cells and their implications for the design of novel NK cell-based immunotherapies against sarcoma.

Abstract

Natural killer (NK) cells are innate lymphoid cells with potent antitumor activity. One of the most NK cell cytotoxicity-sensitive tumor types is sarcoma, an aggressive mesenchyme-derived neoplasm. While a combination of radical surgery and radio- and chemotherapy can successfully control local disease, patients with advanced sarcomas remain refractory to current treatment regimens, calling for novel therapeutic strategies. There is accumulating evidence for NK cell-mediated immunosurveillance of sarcoma cells during all stages of the disease, highlighting the potential of using NK cells as a therapeutic tool. However, sarcomas display multiple immunoevasion mechanisms that can suppress NK cell function leading to an uncontrolled tumor outgrowth. Here, we review the current evidence for NK cells’ role in immune surveillance of sarcoma during disease initiation, promotion, progression, and metastasis, as well as the molecular mechanisms behind sarcoma-mediated NK cell suppression. Further, we apply this basic understanding of NK–sarcoma crosstalk in order to identify and summarize the most promising candidates for NK cell-based sarcoma immunotherapy.

Aging and lymphocyte subsets in the spleen and peripheral blood of the Sprague-Dawley rat

This study was undertaken to determine the effects of aging on lymphocyte subsets in the peripheral blood and spleens of Sprague-Dawley rats. Rats aged 3,13 and 26 months were used in the study. Analyses of dual labeled lymphocytes from the 26 month animals show decreases in the numbers of lymphocytes due to decreased cellularity (spleen) or reduced lymphocyte percentages within the total white blood cell population (peripheral blood). In the spleens and blood of the oldest rats, there were reduced numbers of Total T, T helper/amplifier (Th/a), virgin Th and natural killer (NK) cells. Other changes were observed in the spleen but not peripheral blood. The numbers of T cytotoxic/suppressor cells (Tc/s) B cells, "autoimmune" B cells and NK cells were reduced in the spleen but remained within normal limits in peripheral blood. The data show aging exerts different effects on the peripheral blood and splenic compartments of the immune system. These differences may have teleological significance in relation to immune responses to xenobiotics and neoplastic cells.

Class I-induced resistance to natural killing: identification of nonpermissive residues in HLA-A2

Structural characteristics of major histocompatibility complex class I antigens associated with natural killer (NK)-resistance phenomena were examined. Previous research has shown that transfection of class I genomic DNA clones into class I-deficient, NK-sensitive target cell lines results in transfectants exhibiting class I+, NK-resistant phenotypes. In contrast to the HLA-A3, -B7, -B27, and -Bw58 class I molecules, the HLA-A2 class I molecules were shown not to protect target cells from NK activity. Here we show that this nonprotective phenotype maps to the alpha 1 domain of the HLA-A2 molecule by examining the NK-protective capacity of the natural interdomain recombinant HLA-Aw69 molecule. HLA-Aw69, which consists of an alpha 1 domain exhibiting homology with HLA-Aw68, and alpha 2/alpha 3/transmembrane-cytoplasmic domains, exhibiting homologies with HLA-A2, mimics HLA-Aw68 and provides HLA-A,B null target cell (C1R) transfectants with increased resistance to NK. Further, the inability of transfected HLA-A2 to confer protection against NK activity can be completely attributed to the expression of a "nonpermissive" residue at position 74 in the alpha 1 domain. Site-directed mutation of the His-74 residue in HLA-A2 to the Asp-74 (HLA-A3, -Aw68, -Aw69, -B7) residue generates a mutant that provides C1R cell line transfectants an NK-resistant phenotype. As His-74 blocks access to a side pocket in the HLA-A2 antigen-binding cleft, these results support the critical involvement of residues within the peptide-binding groove of class I molecules in determining the NK susceptibility phenotype of class I+ target cells.

Augmentation of murine lymphokine-activated killer cell cytotoxicity by beta-cyclodextrin-benzaldehyde

We investigated the effect of beta-cyclodextrin-benzaldehyde (CDBA) on lymphokine-activated killer (LAK) cell activity of spleen cells from normal or RCT(+)H-2(+)-sarcoma-bearing C3H/He mice. CDBA augmented the induction of LAK cytotoxicity in vitro against RCT(+)H-2+ tumor cells by IL-2, whereas the culture with CDBA alone did not. In a LAK cytotoxicity assay in vitro, the augmentative effect of CDBA was strongly exerted against spleen cells originating from 2-week-tumor-bearing mice, rather than those from normal mice or mice that had born tumors for 5 weeks. Such an augmentative effect was not observed against other tumor cells (YAC-1, D-6, Colon-26 and EL-4 cells) non-specifically. When the intravenous adoptive transfer of LAK cells was carried out in the mice, LAK cells from tumor-bearing mice induced by combined culture with interleukin-2 (IL-2) and CDBA markedly inhibited the pulmonary metastases of RCT(+)H-2+ tumor, while neither LAK cells from the same tumor-bearing mice induced by only IL-2 nor those from normal mice inhibited the pulmonary metastasis. The majority of LAK cells induced either by IL-2 plus CDBA or by IL-2 alone were found to be Thy1.2+ and asialoGM1+ cells by flow-cytometric analysis, but no obvious phenotypical difference was observed between them. However, the most significant effect of CDBA might be the maintenance of the Lyt-2+ cell level in the spleen cells from tumor-bearing mice. These results suggested that the costimulation of spleen cells with IL-2 and CDBA might induce cytotoxic T cells specific for syngeneic tumor cells.

Alteration of the metastatic potential of line 1 lung carcinoma cells: opposite effects of class I antigen induction by interferons versus DMSO or gene transfection

Class I antigens are necessary for the recognition of tumor cells by cytotoxic T lymphocytes (CTL). The line 1 lung carcinoma is a spontaneous murine tumor deficient in class I antigen expression. Consistent with this, line 1 cells are highly metastatic in vivo. We investigated whether increasing class I antigen expression on line 1 cells could alter the metastatic potential of these tumor cells using an in vivo lung metastasis model. We used three methods to induce class I antigen expression on line 1 cells: gene transfection, treatment with dimethyl sulfoxide (DMSO), or treatment with interferon (IFN)-beta or -gamma. We found that line 1 cells expressing a transfected class I gene were significantly less metastatic than parental line 1 cells. DMSO-treated line 1 cells also formed significantly fewer metastases than parental line 1 cells. These results indicate that increased class I antigen expression decreases the metastatic potential of line 1 cells in vivo. However, we did not observe a significant decrease in the number of lung metastases in mice receiving line 1 cells treated with IFN-beta or -gamma, despite high levels of class I antigen expression. Thus, increasing class I antigen expression with IFN has an opposite effect on metastasis from class I antigen expression induced by transfection or DMSO. These results show that the method used to increase class I antigen expression is critical in terms of the in vivo effect observed. To investigate a possible mechanism for the differences observed in vivo between these class I expressing cells, we tested whether IFN alters or blocks susceptibility of line 1 cells to immune effector cells. We found IFN treatment increased the ability of line 1 cells to be recognized by CTL but concomitantly decreased the susceptibility of line 1 cells to NK cell lysis by a non-class I antigen-related mechanism. In contrast, transfected or DMSO-treated line 1 cells which were less metastatic in vivo were susceptible to both CTL and NK-mediated lysis. Taken together, these results suggest that immune intervention against metastasizing line 1 cells may involve NK cells and CTL.