Production and characterisation of a monoclonal antibody specific for apoptotic bodies derived from several tumour cell lines.

We have recently shown that apoptotic bodies (apobodies) derived from rat colon carcinoma cell lines (PROb) after sodium butyrate (NaB) treatment were able to cure rats with induced peritoneal carcinomatosis ( [BOISTEAU] ). A specific immune response was assumed to be involved since the serum of cured rats contained antibodies specific for apobodies. In the present study, a mAb (clone 6E8) produced by immunisation of rats with apobodies strongly recognized apobodies but had little reactivity with parental tumour cell lines, as demonstrated by enzyme-linked immunosorbent assay (ELISA), immunostaining and flow cytometry. Immunoelectron microscopy showed that 6E8 mAb mainly stained the hyaloplasm or cytosol of apobodies. A protein was detected at 67 kDa by immunoprecipitation of apobodies with mAb, followed by immunoblotting, using serum of rats immunised with apobodies. The 6E8 mAb recognized apobodies derived from several rat or human colon cancer cell lines and a rat glioma cell line, regardless of the apoptosis stimulus used (NaB, staurosporine or UV). Our results clearly show that 6E8 mAb defines an epitope specifically generated during apoptosis, which suggests that the protein recognized may be involved in the molecular cascade of apoptotic cell death.

[Modulation of integrin alpha-v-beta-1 expression on human tumor cells by leukemia inhibitory factor (LIF) and oncostatin M (OSM)]. / Modulation de l'expression de l'intégrine alpha-v-beta-1 à la surface des cellules cancéreuses humaines par le leukemia inhibitory factor (LIF) et l'oncostatine M (OSM).

Integrins belong to a large family of heterodimeric membrane glycoproteins which mediate cell-cell or cell-extracellular matrix interactions. These interactions could play a major role during the migration of tumor cells across the extracellular matrix and vascular endothelium and would thus appear to be a requisite for the metastatic process. Treatment of the Foss human melanoma cell line with LIF or OSM, two cytokines involved in acute-phase response, increased the expression of membrane alpha v beta 1 by 1.5-2 fold. The same phenomenon was observed on the SK-N-SH human neuroblastoma cell line. This modulation, which was inhibited by specific monoclonal antibodies against alpha v or beta 1 integrin subunits, was concomitant with improved tumor cell attachment to the fibronectin matrix. Similar results were obtained after TNF-alpha treatment. Our findings demonstrate the ability of LIF and OSM to modulate tumor cell capacity to adhere to the matrix component, suggesting a potential role for these cytokines in modulation of tumoral progression.

Upmodulation of alpha v beta 1 integrin expression on human tumor cells by human interleukin for DA cells/leukemia inhibitory factor and oncostatin M: correlation with increased cell adhesion on fibronectin.

Integrins belong to a large family of heterodimeric membrane glycoproteins which mediate cell-cell or cell-extracellular matrix interactions. These interactions could play a major role during the migration of tumor cells across the extracellular matrix and vascular endothelium and would thus appear to be requisite for the metastatic process. Pretreatment of the Foss human melanoma cell line with HILDA/LIF or OSM, two cytokines involved in acute-phase response, increased the expression of membrane alpha v beta 1 1.5-2-fold. The same phenomenon was observed on the SK-N-SH human neuroblastoma cell line. alpha v beta 1 upmodulation was concomitant with improved tumor cells attachment to the fibronectin matrix. This greater adhesion of tumor cells to fibronectin was inhibited by specific monoclonal antibodies against alpha v or beta 1 integrin subunits. Similar results were obtained after TNF-alpha treatment. Our findings demonstrate the ability of HILDA/LIF and OSM to modulate tumor cell capacity to adhere to the matrix component, suggesting a potential role for these cytokines in modulation of tumoral progression.

Human interleukin for DA cells/leukemia inhibitory factor and oncostatin M enhance membrane expression of intercellular adhesion molecule-1 on melanoma cells but not the shedding of its soluble form.

ICAM-1-mediated cell-cell adhesion is essential for different immunologic functions including non-MHC-restricted cytotoxicity. The shedding of a soluble form of ICAM-1 from melanoma impairs immune recognition and leads to tumour escape. Pretreatment of the Foss human melanoma cell line with HILDA/LIF or OSM, two cytokines involved in acute-phase response, increased the expression of membrane ICAM-1 twofold without inducing sICAM-1 shedding. Conversely, TNF-alpha, in the same conditions, strongly stimulated membrane ICAM-1 expression and the shedding of the soluble form. The same phenomenon was observed on the A375 human melanoma cell line. ICAM-1 upregulation was concomitant with an increase in the non-MHC-restricted cytotoxicity of tumour cells mediated by LAK cell.s This higher sensitivity to LAK lysis was abolished by RR1/1, a specific monoclonal antibody against ICAM-1. Our results demonstrate for the first time the ability of HILDA/LIF and OSM to upregulate ICAM-1 expression on the melanoma cell surface, suggesting a potential role for these cytokines in human immune surveillance during tumour progression.