Heterogeneity and immunophenotypic plasticity of malignant cells in human liposarcomas

Liposarcomas are tumors arising in white adipose tissue (WAT) with avidity for local recurrence. Aggressive dedifferentiated liposarcomas (DDLS) may arise from well-differentiated subtypes (WDLS) upon disease progression, however, this key issue is unresolved due in large part to knowledge gaps about liposarcoma cellular composition. Here, we wished to improve insights into liposarcoma cellular hierarchy. Tumor section analysis indicated that the populations, distinguishable based on the expression of CD34 (a marker of adipocyte progenitors) and CD36 (a marker of adipocyte differentiation), occupy distinct intra-tumoral locations in both WDLS and DDLS. Taking advantage of these markers, we separated cells from a panel of fresh human surgical specimens by fluorescence-activated cell sorting (FACS). Based on chromosome analysis and the culture phenotypes of the composing populations, we demonstrate that malignant cells comprise four mesenchymal populations distinguished by the expression of CD34 and CD36, while vascular (CD31. +) and hematopoietic (CD45. +) components are non-neoplastic. Finally, we show that mouse xenografts are derivable from both CD36-negative and CD36-positive DDLS cells, and that each population recreates the heterogeneity of CD36 expression in vivo. Combined, our results show that malignant cells in WDLS and DDLS can be classified according to distinct stages of adipogenesis and indicate immunophenotypic plasticity of malignant liposarcoma cells.