Neuroblastoma and hepatocyte coculture conditioned media alter apoptosis

Background. Neuroblastoma is a childhood tumor that often displays unusual biological behavior. The tumor may present with widespread metastases that are unresponsive to aggressive treatment. At other times, both the metastas es and the primary tumor may spontaneously regress without treatment. Apopt osis, or programmed cell death, is thought to play a role in the dichotomou s behavior of neuroblastoma, We hypothesize that neuroblastoma cells will i nteract with host tissues to release mediators that affect apoptosis, Materials and methods. Human neuroblastoma cells and human Chang hepatocyte s are grown in a noncontact, coculture system. After incubation for 4 days, the medium from the coculture system is collected. Neuroblastoma cells and Chang hepatocytes are then plated separately with the conditioned medium a nd their own standard growth medium as controls. After 4 days, these cells are harvested and cytospins made for immunostaining, Tumor necrosis factor alpha (TNF-alpha), Fas ligand, and Bcl-2, are measured with immunohistochem istry, Apoptosis is detected with the TUNEL method. Immunostaining data are interpreted with computer image analysis and reported as stain index. TUNE L data are reported as percentage apoptotic cells. All data are reported as means +/- SEM, Statistical analysis is performed and P < 0.05 considered s ignificant. Results. Chang hepatocytes grown in the coculture conditioned media have an increase in TNF-alpha and Fas ligand, The neuroblastoma cells have a signi ficant decrease in Fas ligand, There is a significant increase in the numbe r of apoptotic hepatocytes when they are cultured in the conditioned media. In contrast, the neuroblastoma cells grown in the coculture conditioned me dia show no increase in apoptosis. Finally, Bcl-2 is significantly increase d in the neuroblastoma cells cultured in the conditioned media. Conclusions. Neuroblastoma cells grown in coculture conditioned media show increased expression of Bcl-2 and decreased Fas ligand levels. These change s should diminish apoptosis activity in the tumor cells. In contrast, the c onditioned media induce elevated levels of proapoptotic mediators in the Ch ang hepatocytes, A tumor's ability to successfully metastasize may be depen dent on mediators generated in the tumor-host interaction, and may not be j ust an independent characteristic of the tumor itself, (C) 2000 Academic Pr ess.