Nestin Expression in Ewing Sarcoma Family Tumors
S Galli, G Li, M Tsokos. NCI/NIH, Bethesda, MD
Background: Nestin is an intermediate filament protein, which is expressed in pluripotent embryonic stem cells. It has been detected in several tumors, especially in those of neuroectodermal and mesenchymal origin. ESFT are characterized by specific translocations, the most common of which is EWS/FLI1. Recent data have pointed to a mesenchymal stem cell phenotype of ESFT cells with silenced EWS/FLI1. Because nestin is a marker of progenitor/stem cells, we addressed whether EWS/FLI1 downregulation induces nestin expression in ESFT cells in vitro and explored the extent of nestin expression in ESFT tissues and cell lines.
Design: We examined the expression of nestin by immunohistochemistry in 55 formalin-fixed paraffin-embedded tumor tissue samples from 38 patients treated in our institution. In 8 patients, several tissue samples (2 to 4 per patient) obtained over a period of 2 to 17 years were available for review. We also analyzed nestin protein expression by Western blot in 14 ESFT cell lines, and in 2 cell clones of the TC-71 ESFT cell line that had been stably transfected with EWS/FLI1 short hairpin (sh) RNA plasmid to silence EWS/FLI1. The presence of EWS/FLI1 was evaluated by RT-PCR in all cell lines.
Results: From the 38 patients, only 2 had nestin-positive tumor samples at diagnosis with 1% to 5% positive cells correspondingly. One of these patients developed a higher percentage (20% and 40%) of nestin-positive cells in two subsequent biopsies. Another patient whose original tumor was negative for nestin showed expression in subsequent biopsies (40%). ESFT cell lines were more frequently positive for nestin (9/14 positive). Highest expression was found in one cell line with a variant EWS/FLI1 fusion transcript and in the 2 clones with silenced EWS/FLI1.
Conclusions: Our data show that: 1) nestin is minimally expressed in ESFT tissue at diagnosis, but can be induced in some patients 2) increased nestin expression correlates with EWS/FLI1 downregulation or presence of EWS/FLI1 variant. Because relapses in ESFT have been attributed to stem cells with undetectable EWS/FLI1 (dormant cells), nestin may be a used as a marker to detect stem cells in ESFT and may play a role in the biology of the tumor.
Monday, March 22, 2010 1:00 PM
Poster Session II # 198, Monday Afternoon