Non-Invasive Measurement of Elasticity in Glioblastoma Multiforme Validates Decreased TMZ Sensitivity in Astrocyte Co-Culture

<i>Goal:</i> In this research, we investigated the changes in elasticity of in vitro glioblastoma multiforme (GBM) spheroids when treated with the gold standard chemotherapy for GBM, Temozolomide (TMZ). Additionally, we aimed to use this alternative biomarker to assess how modifying the tumor microenvironment (TME) with the addition of human astrocytes (HA) would influence treatment efficacy. <i>Methods:</i> Spheroid stiffness was investigated using advanced non-invasive optical techniques, nanobomb optical coherence elastography (nb-OCE) and Brillouin microscopy to obtain new biomechanical insights by assessing local tumor progression or response to therapy using GBM cells (LN229). <i>Results:</i> The treated monocultured GBM groups showed a significant decrease in stiffness and increased sensitivity to treatment with TMZ. Treated HA groups across approaches remained relatively unchanged in stiffness. Treated co-culture groups demonstrated significant resistance to treatment with TMZ, where stiffness decreased less than that of the treated LN229 cells. <i>Conclusions:</i> These results confirm earlier findings using cell viability as a biomarker for treatment efficacy, making nb-OCE and Brillouin promising options to probe 3D tumor models in vitro non-invasively.