Local production of TGF β1 inhibits cerebral edema, enhances TNF- α induced apoptosis and improves survival in a murine glioma model

Abstract

We have previously reported that local secretion of either TNF- α or TGF β1 by intracerebral SMA-560 malignant glioma tumor cells can reduce or eliminate tumor growth in mice. However, the use of TNF- α, while improving the overall survival of tumor bearing animals, was associated with early toxic deaths due to cerebral edema. In the present study, we demonstrate that TNF- α induces apoptosis of the SMA 560 cell line, as does TGF β1, and that these two cytokines act in an additive fashion to enhance apoptosis and thus, to inhibit SMA 560 cell growth in vitro. Next, we show that the production of TGF β1 when added to TNF- α production by central nervous system tumors in vivo abrogates any early deaths seen due to TNF- α toxicity and leads to a larger percentage of animals surviving CNS tumor challenge. Finally, we demonstrate that the production of TGF β1 by tumor cells is associated with the abolition of tumor-associated cerebral edema in both TNF- α and in non-TNF- α producing tumors. These results are important for the development of effective and less toxic therapies for brain tumors, as well as for examining the pathogenesis of tumor-related cerebral edema.