Abstract 3660: Bone mechanics influence cancer stem cell formation in osteosarcoma

Abstract

Osteosarcoma (OS) is the most common primary tumor of bone and is characterized by rapid bone remodeling accompanied by structural and mechanical heterogeneity across the tumor. Chemoresistance and recurrence of OS can be attributed to a subpopulation of OS cells known as cancer stem-like cells (OS-CSCs). It can be hypothesized that tumor niches possessing distinct structural and mechanical properties could be harboring different OS cell populations, and certain niches might be more conducive for OS-CSCs formation and maintenance. To evaluate the presence of OS-CSCs, mineralized collagen scaffolds mimicking heterogenous bone niches with distinct structural and mechanical properties were fabricated by changing collagen content and pore alignment and were cultured with the highly metastatic human OS cell line 143B. Scaffolds with 47% collagen by weight but different pore alignment were chosen for further analysis because they possessed different stiffness and topographical properties. Cytoskeletal changes, epigenetic changes, chemoresistance and chemoresistance-related pathways, and the levels of stemness genes were assessed in the 3D scaffold cultures. A consistent trend of OS-CSC phenotype was observed in the cell population grown in the softer bone niches (12 kPa) with aligned pores as compared to stiffer niche (31 kPa) with non-aligned pores. The cell population growing in softer, aligned scaffolds had a significantly higher expression of stemness genes (OCT4, NANOG, SOX2, ALDH1A1) and drug efflux gene ABCB1 and increased chemoresistance to doxorubicin and cisplatin. Epigenetic changes associated with cisplatin resistance in OS such as a decrease in methyl transferase EZH2 accompanied by the upregulation of LIF/Notch and PRKCA pathways was observed in cells grown in softer, aligned niches. Fluorescent imaging of actin organization showed rounder cells in the aligned niche indicative of the CSC phenotype, and stretched, elongated cells in the non-aligned niche indicative of a differentiated phenotype. Our study showed that the mechanical and structural properties of bone niches influence the formation of distinct OS cell populations. A softer niche with an aligned structure is more conducive for maintaining OS-CSCs. Citation Format: Zunaira Shoaib, Aleczandria S. Tiffany, Brendan Harley, Joseph Irudayaraj, Timothy M. Fan. Bone mechanics influence cancer stem cell formation in osteosarcoma. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3660.