Intracellular mechanics and TBX3 expression jointly dictate the spreading mode of melanoma cells in 3D environments

Background Cell stiffness and TBX3 expression have been identified as biomarkers of melanoma metastasis in 2D environments. This study aimed to determine how mechanical and biochemical properties of melanoma cells change during cluster formation and metastasis in 3D environments mimicking physiological conditions. Methods Vertical growth phase (VGP) and metastatic (MET) melanoma cells were embedded in 3D collagen matrices of different concentrations. Mitochondrial fluctuations, intracellular stiffness and TBX3 levels were quantified before and after cluster formation. Results In isolated cells, mitochondrial fluctuations decreased, and stiffness increased across disease stages and matrix rigidities. TBX3 was overexpressed in soft but diminished in stiff matrices. During cluster formation in soft matrices, the intracellular properties of VGP cells did not change during extensive cluster formation, whereas mitochondrial fluctuations increased and TBX3 expression decreased in MET cells during limited cluster formation. In stiff matrices, cluster formation was restricted, mitochondrial fluctuations and TBX3 expression increased in VGP and MET, and cell stiffness increased in VGP and decreased in MET. Conclusions Mitochondrial activity, cell stiffness, and cellular TBX3 expression jointly affected cluster formation and metastasis in melanoma with contributions that vary with changes in environmental properties. General significance This study highlights the importance of considering both the biophysical and biochemical properties of the malignant cells and the extracellular environment for the advancement of targeted melanoma therapies.