Detection of interferon inhibitors or antagonists in gastrointestinal malignancies.

BACKGROUND/AIMS: The aim of this study was to investigate the IFN-inhibiting activity in sera from patients with gastrointestinal malignancies, exerted in a variety of cellular types, as well as to elucidate the determinants of cellular sensitivity to such IFN-inhibitors. METHODOLOGY: Sera from 16 patients with gastric cancer and 18 with colon cancer were tested, while sera from 37 healthy blood donors were used as controls. All serum samples, collected before any kind of treatment, were tested for IFN-blocking and endogenous IFN-like activity. These activities were determined by assaying the inhibition of the vesicular stomatitis virus specific cytopathic effect in three cell lines: A549 cells, intestine 407 and Chang liver cells. RESULTS: There was no endogenous IFN in any of the serum samples of patients or controls. Concerning the IFN blocking activity of serum, there was no significant difference between gastric and colon cancer, while a marked variability was prominent depending on the cell line used. 76.4% of serum samples exerted IFN-blocking activity in the A549 cells, 47.05% in the Int-407 cell line and 32.3% in the Chang Liver cells. No control sample had IFN-blocking activity in any of the cell lines tested. CONCLUSIONS: The results support a cytokine and cytokine inhibitors network, mediating pathophysiological events at the cellular level as well as the whole organism. The limited responsiveness of many neoplasias, including digestive system cancer, to IFN treatment might be due to the presence of IFN inhibitors in the patient's serum.

The effect of eicosanoids on the expression of MHC genes in cultured human colon cancer cells and mouse colonocytes in vivo.

Eicosanoids have been implicated in the pathogenesis of cancer and are known to regulate the expression of antigens of the major histocompatibility complex (MHC). In human colon cancer, we have recently observed that: (a) the expression of MHC class I and II antigens are markedly reduced; and (b) the levels of PGE2, but not of PGF2 alpha and LTB4, are elevated compared to histologically normal mucosa. Therefore, we investigated the effect of PGE2, PGF2 alpha and LTB4 on the regulation of MHC class I antigens in two human colon adenocarcinoma cell lines and in a murine model of colon cancer. None of these eicosanoids had any significant effect on the expression of MHC class I antigens in the human colonocytes or the transcription rate of class I genes, with the exception of LTB4 which only modestly suppressed the transcription rate. Similarly, 16, 16-dimethyl-PGE2 had no effect on the expression of MHC class I genes in the colonocytes of BALB/c mice treated with the carcinogen dimethylhydrazine. We conclude that PGE2, PGF2 alpha and LTB4 did not affect the expression of MHC class I antigens in cultured human colon adenocarcinoma cells, and 16, 16-dimethyl PGE2 did not affect their expression in mice, even when mice were treated with a colon carcinogen. Thus, these eicosanoids are an unlikely regulator of the observed underexpression of MHC class I antigens in human colon cancer.

Prostaglandin E2 down-regulates the expression of HLA-DR antigen in human colon adenocarcinoma cell lines.

Prostaglandins (PG) have been implicated in the pathogenesis of cancer and play an important role in immune regulation. Colon cancer is associated with elevated levels of PGE2, while aspirin, the prototypical inhibitor of PG synthesis, appears to reduce the incidence of colon cancer by 50%. We have observed that in human colon cancer the expression of HLA class I and II antigens is reduced or lost; loss of HLA antigens is suspected to be a mechanism by which the malignant cell escapes the immune surveillance. We investigated the effect of these eicosanoids on the expression of HLA antigens in human colon adenocarcinoma cell lines. PGE2 down-regulated the expression of the class II antigen HLA-DR in SW1116 cells (65% reduction at 2.8 x 10(-8) M). This effect was dose- and time-dependent, reversible, and specific (PGF2 alpha and LTB4 had no effect; the expression of carcinoembryonic antigen and class I genes were not affected). Aspirin induced the expression of HLA-DR in HT29 cells, a cell line not expressing constitutively HLA-DR. The reduction of HLA-DR by PGE2 was accompanied by reduced messenger RNA (mRNA) levels of HLA-DR alpha and reduced transcription of the corresponding gene. In contrast to HLA-DR, none of these three eicosanoids affected the expression of HLA class I genes, as assessed via determination of protein expression by fluorescence flow cytometric analysis and evaluation of the corresponding class I mRNA levels. We conclude that PGE2 specifically down-regulates the expression of HLA-DR, while it does not affect the expression of class I antigens.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of ethanol on the expression of HLA class I genes in human colon adenocarcinoma cell lines.

The loss of HLA antigens by neoplastic cells may allow tumors to escape immune surveillance. We observed reduced expression of HLA antigens during human colon carcinogenesis. Since ethanol, which is associated with human colonic carcinogenesis, modulates the expression of HLA genes, we examined whether it affects the expression of HLA class I genes in human colon adenocarcinoma cell lines. Ethanol (1.7 x 10(-10) M to 1.7 x 10(-1) M), had no effect on the expression of HLA class I antigens on these colonocytes, the corresponding mRNA levels, or the expression of HLA constructs. Our findings do not support the hypothesis that ethanol may modulate the expression of HLA class I genes in human colon cancer cells.

Lithocholic acid inhibits the expression of HLA class I genes in colon adenocarcinoma cells. Differential effect on HLA-A, -B and -C loci.

Loss of HLA antigen expression is considered to be one of the mechanisms whereby tumor cells escape immune surveillance. We recently observed reduced or lost expression of HLA antigens during human colon carcinogenesis. We studied the effect of bile acids (BAs), long implicated in the pathogenesis of colon cancer, on the expression of HLA class I antigens in human colon adenocarcinoma cells. Lithocholic acid (LCA) decreased by 42% the expression of HLA class I antigens on the surface of these cells. This dose-dependent reduction was specific for both the target genes and the chemical structure of LCA, and was not evident in cultured liver cells. None of the other BAs that were tested manifested this effect. LCA, and to a lesser extent deoxycholic acid (DCA), decreased steady-state HLA class I mRNA levels. LCA decreased the rate of transcription of HLA-B (64%) and HLA-C (87%) but not HLA-A; DCA had a similar but less pronounced effect. In transient gene expression (CAT assays) experiments, we evaluated the role of a 0.6-0.7 kb EcoRI/XbaI sequence from the 5' flanking region of HLA-A2, -B7 and -Cw7 genes in the regulation of class I gene expression by LCA. LCA down-regulated by 70% the expression of the reporter gene for all three genes. We interpret these results as indicating a differential regulation of the three HLA loci by LCA. Our findings, demonstrating a profound effect of LCA on HLA class I gene regulation, raise the possibility that such a mechanism may be operative in vivo.

Expression of HLA class I antigens in sporadic adenomas and histologically normal mucosa of the colon.

The loss of HLA antigens by neoplastic cells is considered important for tumor growth and metastasis, inasmuch as it may allow tumors to escape immune surveillance. We have observed reduced expression of HLA antigens in sporadic colon cancer and adenomas from familial adenomatous polyposis patients. We now studied the expression of HLA class I antigens in patients with sporadic adenomas, which are precursors of colorectal cancer. Expression of HLA class I antigens was studied by immunohistochemistry in (a) sporadic colon adenomas, (b) histologically normal mucosa distant from the adenomas, (c) histologically normal colonic mucosa from patients with history of sporadic colon adenomas, and (d) colonic mucosa from normal subjects. HLA class I antigen expression was moderately reduced in 56% and severely reduced in 44% of the adenomas; this reduction was significant when compared to controls (P < 0.0001). The reduction of HLA class I expression in adenomas was related to the grade of dysplasia of the adenomas. HLA class I expression of normal appearing mucosa was decreased in 76% of patients with adenoma (P < 0.0001) and in 54% of patients with history of adenoma (P < 0.005) compared to normal controls. These changes were antigen specific, inasmuch as the expression of carcinoembryonic antigen, a surface antigen, was not affected. Our findings suggest that reduced HLA class I expression is an early event in the cell transformation process from normal to neoplastic state, preceding in many cases the onset of histological changes. HLA class I could be potentially used as a premalignant marker in the colon.