Abstract LB-262: Mesenchymal stem cell-like characteristics of human phyllodes tumors
Authors: Lin Jin-Jin , Yu John , Huang Chiun-Sheng , Yeh Kun-Tu , Lien Huang-Chun , Chou Fen-Pi , Chang Wea-ying , Yu Alice L. 
Published: February 2011

Phyllodes tumor which contains heterologous stromal elements, can transform into rhabdomyosarcoma, liposarcoma and osteosarcoma. These versatile properties of phyllodes tumor are reminiscent of mesenchymal stem cells (MSCs). We hypothesized that malignant phyllodes tumor may possess MSC-like properties. Forty-four paraffin-embedded malignant phyllodes tumors and two fresh tumor specimens were examined. by immunohistochemical staining for six MSC markers including CD44, CD29, CD106, CD166, CD105, CD90 and one cancer stem cell marker, Aldehyde dehydrogenase activity (ALDH). All MSC markers, except CD105, were detected in phyllodes tumors, with the following frequencies: CD166 (ALCAM; 76.1%), CD90 (76.1%), CD44 (HCAM, 66.6%), CD106 (VCAM-1, 30.1%), and CD29 (23.9%). ALDH was detected in all tumors with varying extent of expression, ranging from 3% to &gt;90%. In addition, we successfully established 2 xenografts of primary human phyllodes tumors in NOD- SCID mice. Flow cytometric analysis of one of the xengrafted tumor revealed 12.6% of the cells to be highly positive for ALDEFLUOR. In vitro, the sorted ALDEFLUOR-high cells grew as spindle-shaped cells with spontaneous formation of colonies, which persisted upon serial passages. Immunofluorescent staining revealed that CD44-positive cells appeared to be distributed near the colony periphery; meanwhile CD10, CD29 and CD166 were localized at the center of the colonies. In vivo, freshly sorted ALDH-positive cells displayed greater engraftment capacity in mice than ALDH-negative cells. As few as 100 ALDH-positive cells were sufficient to form tumor, whereas a minimum of 2×104 ALDH-negative cells were needed for engraftment. It has been shown that neural ganglioside GD2 was expressed on MSC. ALDH/GD2 double positive cells (1.9%) sorted from tumor xenograft were readily engrafted into mice. Such tumor xenografts showed neuron-like histology in HE staining. Notably, only 50 ALDH/GD2 double positive cells were sufficient for engraftment. In vitro culture of ALDH / GD2 double positive cells sorted from the original tumor xenograft yielded rapidly growing spindle-shaped cells, forming numerous colonies. Between day 14 and 21, these cells could be induced by exogenous cAMP to differentiate into neural cells of various lineages, which expressed nestin (neuron stem/progenitors cell marker), ßIII-tubulin (immature neuronal progenitor cells) or GFAP(glial fibrillary acidic protein, marker for astrocytes) as shown by immunofluorescent staining. On the other hand, cultured ALDH-positive cells could be induced by isobutylmethylxanthine or beta-glycerophosphate to differentiate into adipocytes or osteocytes, utilizing Oil Red O and Alizarin Red staining, respectively. In conclusion, our findings revealed that malignant phyllodes tumor might possess many characteristics of MSC, as reflected by their phenotypic markers and ability to differentiate into various lineages of tissue/cell types.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr LB-262.