Peripheral neuroectodermal tumors (
PNET) have an unsatisfactory outcome when treated with standard approaches. Among novel treatments, the use of
biological response modifiers has rarely been reported in this group of
malignancies. We have previously demonstrated that both
all-trans retinoic acid (ATRA) and
interferon á (IFNá) can inhibit proliferation of human
PNET cells and that ATRA can up-regulate IFNá receptor expression in vitro. In this study we evaluated the anti-
tumor effects of ATRA and IFNá in
PNET cells in vitro and in a human
PNET xenograft model, using CHP100 cells. A synergistic inhibitory effect of ATRA and IFNá was observed on CHP100 cells in vitro. On the contrary, a significant inhibition of
tumor growth was observed in mice treated with ATRA alone, whereas neither IFNá nor the combination of ATRA and IFNá, reached a statistically significant anti-
tumor effect. Histologic examination of
tumors revealed the presence of
necrosis upon treatment with IFNá, whereas almost no
necrosis, but a more differentiated morphology, confirmed by electron microscopy analysis, was associated with the ATRA containing treatments. Taken together these data show an in vitro and in vivo anti-
tumor activity of ATRA in human
PNET cells, although no synergism of ATRA and IFNá was observed in our xenograft model.