T lymphocytes that infiltrate tumors and atherosclerotic plaques produce heparin-binding epidermal growth factor-like growth factor and basic fibroblast growth factor: a potential pathologic role

Lysophosphatidylcholine increases expression of heparin-binding epidermal growth factor-like growth factor in human T lymphocytes

Atherosclerotic lesions contain substantial numbers of activated T lymphocytes in addition to monocytes/macrophages. T cell-derived cytokines and growth factors may play a role in atherogenesis; however, stimuli responsible for T-cell activation in atherogenesis have not been fully elucidated. In this study, we provide evidence that lysophosphatidylcholine (lyso-PC), a polar phospholipid component increased in atherogenic lipoproteins and atherosclerotic lesions, can upregulate gene expression and secretion of heparin-binding epidermal growth factor-like growth factor (HB-EGF) in cultured T lymphocytes isolated from human peripheral blood. Effects of lyso-PC on T lymphocytes appear to be selective and specific, since lyso-PC also increases interleukin (IL)-2 receptor expression but does not affect mRNA levels for IL-2 or IL-4. Lyso-PC-induced upregulation of HB-EGF and IL-2 receptor mRNA in peripheral T cells is mostly dependent on exogenous IL-2 in conditioned medium. The effect of lyso-PC on HB-EGF induction was more potent in CD4+ cells than in CD8+ cells, although lyso-PC increases IL-2 receptor expression dramatically in both CD4+ cells and CD8+ cells. Lyso-PC similarly increased HB-EGF expression in Jurkat cells, a cell line for human CD4+ T lymphocytes. These results in vitro suggest that lyso-PC may be an important stimulus for T cells in atherogenesis in vivo to upregulate HB-EGF and that T cell-derived smooth muscle growth factors may modulate atherosclerotic progression.

Heparin-binding EGF-like growth factor is an autocrine growth factor for human urothelial cells and is synthesized by epithelial and smooth muscle cells in the human bladder

The epidermal growth factor receptor (HER1) has been implicated in regenerative growth and proliferative diseases of the human bladder epithelium (urothelium), however a cognate HER1 ligand that can act as a growth factor for normal human urothelial cells (HUC) has not been identified. Here we show that heparin-binding EGF-like growth factor (HB-EGF), an activating HER1 ligand, is an autocrine regulator of HUC growth. This conclusion is based on demonstration of HB-EGF synthesis and secretion by primary culture HUC, identification of HER1 as an activatable HB-EGF receptor on HUC surfaces, stimulation of HUC clonal growth by HB-EGF, inhibition of HB-EGF-stimulated growth by heparin and of log-phase growth by CRM 197, a specific inhibitor of HB-EGF/HER1 interaction, and identification of human urothelium as a site of HB-EGF precursor (proHB-EGF) synthesis in vivo. ProHB-EGF expression was also detected in the vascular and detrusor smooth muscle of the human bladder. These data suggest a physiologic role for HB-EGF in the regulation of urothelial proliferation and regeneration subsequent to mucosal injury. Expression of proHB-EGF is also a feature of differentiated vascular and detrusor smooth muscle in the bladder. Because proHB-EGF is known to be the high affinity diphtheria toxin (DT) receptor in human cells, synthesis of the HB-EGF precursor by human urothelium also suggests the possibility of using the DT-binding sites of proHB-EGF as an in vivo target for the intraluminal treatment of urothelial diseases.

Postnatal regulation of fibroblast growth factor ligand and receptor gene expression in rat thoracic aorta

Fibroblast growth factor (FGF)-1 and FGF-2 are potent angiogenic factors and vascular smooth muscle cell (SMC) mitogens in vivo. They function via binding to a family of structurally related cell surface receptors that possess intrinsic tyrosine kinase activity. Several studies have indicated that increased FGF and/or FGF receptor (FGFR) expression may correlate with adult SMC proliferation in vivo. In this study, we used Northern blot hybridization and reverse transcription-polymerase chain reaction assays to compare the FGF and FGFR mRNA levels in newborn rat aorta, where SMCs have a high replication index, to those in adult rat aorta, where SMCs are relatively quiescent. We found that FGF-2 and FGFR-2 mRNA expression was elevated 8.2- and 5.6-fold, respectively, in adult aorta. Increased FGF-2 protein expression in the adult aorta was confirmed by Western blot analysis. We also examined FGF and FGFR mRNA expression levels in SMC cultures derived from newborn or adult rat aorta. FGF-1 transcripts were more abundant in newborn SMCs whereas FGF-2 and FGFR-1 mRNA expression was higher in adult SMCs. Furthermore, FGF-1 and FGF-2 mRNA expression levels were altered by cell culture density and by serum treatment. We conclude that elevated FGF ligand and receptor expression does not always correlate with a high SMC proliferative index, that FGF-1 or FGF-2 may not be the primary mitogens responsible for newborn SMC growth in vivo, and that FGF-1 and FGF-2 may serve nonmitogenic functions within the mature, adult vessel wall.

Heparin-binding epidermal growth factor-like growth factor regulates fibroblast growth factor-2 expression in aortic smooth muscle cells

Heparin-binding epidermal growth factor-like growth factor (HB-EGF) is a vascular smooth muscle cell (SMC) mitogen and chemotactic factor that is expressed by endothelial cells, SMCs, monocytes/macrophages, and T lymphocytes. Both the membrane-anchored HB-EGF precursor and the secreted mature HB-EGF protein are biologically active; thus, HB-EGF may stimulate SMC growth via autocrine, paracrine, and juxtacrine mechanisms. In the present study, we report that HB-EGF treatment of serum-starved at aortic SMCs can induce fibroblast growth factor (FGF)-2 (basic FGF) gene expression but not FGF-1 (acidic FGF) gene expression. Increased FGF-2 mRNA expression is first detectable at 1 hour after HB-EGF addition, and maximal FGF-2 mRNA levels, corresponding to an approximately 46-fold level of induction, are present at 4 hours. The effect of HB-EGF on FGF-2 mRNA levels appears to be mediated primarily by a transcriptional mechanism and requires de novo synthesized proteins. HB-EGF induction of FGF-2 mRNA levels can be inhibited by treating cells with the anti-inflammatory glucocorticoid dexamethasone or the glycosaminoglycan heparin. Finally, Western blot analyses indicate that HB-EGF-treated SMCs also produce an increased amount of FGF-2 protein. These results indicate that HB-EGF expressed at sites of vascular injury or inflammation in vivo may upregulate FGF-2 production by SMCs.

Inclusion body myositis

Images

Loss of functional beta 2-microglobulin in metastatic melanomas from five patients receiving immunotherapy

BACKGROUND

In a subset of patients with metastatic melanoma, T lymphocytes bearing the cell-surface marker CD8 (CD8+ T cells) can cause the regression of even large tumors. These antitumor CD8+ T cells recognize peptide antigens presented on the surface of tumor cells by major histocompatibility complex (MHC) class I molecules. The MHC class I molecule is a heterodimer composed of an integral membrane glycoprotein designated the alpha chain and a noncovalently associated, soluble protein called beta2-microglobulin (beta 2m). Loss of beta 2m generally eliminates antigen recognition by antitumor CD8+ T cells.

PURPOSE

We studied the loss of beta 2m as a potential means of tumor escape from immune recognition in a cohort of patients receiving immunotherapy.

METHODS

We successfully grew 13 independent tumor cell cultures from tumor specimens obtained from 13 patients in a cohort of 40 consecutive patients undergoing immunotherapy for metastatic melanoma and for whom tumor specimens were available. These cell lines, as well as another melanoma cell line (called 1074mel) that had been derived from tumor obtained from a patient in a cytokine-gene therapy study, were characterized in vitro cytofluorometrically for MHC class I expression and by northern and western blot analyses for messenger RNA (mRNA) and protein expression, respectively, and ex vivo by immunohistochemistry.

RESULTS

After one melanoma cell line (1074mel) was found not to express functional beta 2m by cytofluorometric analysis, four (31%) of the 13 newly established melanoma cell lines were found to have an absolute lack of functional MHC class I expression. Northern blot analysis of RNA extracted from the five cell lines exhibiting no functional MHC class I expression showed that these cells contained normal levels of alpha-chain mRNA but variable levels of beta 2m mRNA. In addition, no immunoreactive beta 2m protein was detected by western blot analysis. When human beta 2m was transiently expressed with the use of a recombinant vaccinia virus, cell-surface MHC class I expression was reconstituted and the ability of these five cell lines to present endogenous antigens was restored. Immunohistochemical staining of tumor sections revealed a lack of immunoreactive MHC class I in vivo, supporting the notion that the in vitro observations were not artifactual. Furthermore, archival tumor sections obtained from patients prior to immunotherapy were available from three patients and were found to be beta 2m positive. This result was consistent with the hypothesis that loss of beta 2m resulted from immunotherapy.

CONCLUSIONS

These data suggest that the loss of beta 2m may be a mechanism whereby tumor cells can acquire immunoresistance. This study represents the first characterization of a molecular route of escape of tumors from immune recognition in a cohort of patients being treated with immunotherapy.