Abstract 3110: ICAM-1(CD54) mediated bi-lineage differentiation in osteosarcoma

Introduction: Osteosarcoma (OS) is the most common primary bone tumor in children and adolescents. The cell of origin in OS is still not known, however, OS cells maintain the capacity for tri-lineage differentiation with the ability to differentiate into osteoblasts (OBs), adipocytes and chondroblasts. The impact of surface antigens on OS differentiation capacity has not well studied. ICAM-1 (CD54) is a transmembrane protein that is involved in intercellular adhesion. We previously reported that ICAM-1 is differentially expressed in mesenchymal stem cells (MSCs) compared with mature osteoblasts. The effect of ICAM-1 on MSC and OS differentiation capacity has not been previously assessed. Methods: ICAM-1 RNA expression was measured in MSCs and OS cells lines and protein expression was assessed using western blot and flow cytometry. Human MSCs and OS cells (M1, M17, M31, M33, M36, M39R, M42, M43, M56, and M60) were placed in osteoblastic and adipogenic differentiation media for 21 and 14 days, respectively. Bi-lineage differentiation capacity was assessed by staining the cells with alizarin red and oil red, to determine the extent of OB and adipose differentiation, respectively at 4 times points (day 0, 7, 14, 21) and 3 time points (day 0, 5, 10, 15). Miscrocopic analysis and spectrophotometric assays were utilized to image and quantify the level of differentiation. Results: Flow cytometric analyses identified 3 cell lines with high surface CD54 expression (CD54high =M17, M33, and M39R) and 3 cell lines with low surface CD54 expression (CD54low=M36, M56, and M60). ICAM-1 expression increased significantly throughout osteoblastic differentiation of MSCs. However, when placed in adipogenic media, MSCs expressed decreasing expression of I-CAM-1. CD54high OS cells demonstrated earlier and more robust osteoblastic differentiation compared with CD54low OS cells. CD54low cells demonstrated earlier and more robust adipogenic differentiation. Conclusion and Future Directions: The CD54high expressing OS cells might retain intermittent osteoblast differentiation capacity. OS cells have a higher adipogenic capacity. Current studies are aimed on the validation of inhibitory effects of ICAM-1 towards OS cell proliferation in vitro and local tumor growth and the development of metastatic disease in preclinical patient derived xenograft in vivo models. We believe that further exploration of the role of surface markers in normal and aberrant osteogenic differentiation may lead to the identification of common tumor progenitor cells and new cell surface based therapeutic targets for the treatment of osteosarcoma. Citation Format: Sankaranarayanan Kannan, Yidan Zhang, Yifei Wang, Sylvester Jusu, Zhongting Zhang, Zhang Wendong, Zhaohui Xu, Michaeal Roth, Gill Jonathan Benjamin, Richard Gorlick. ICAM-1(CD54) mediated bi-lineage differentiation in osteosarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 3110.