Mapping Mechanical Properties of the Tumor Microenvironment by Laser Speckle Rheological Microscopy

Area of Science:

• Biomedical Engineering
• Oncology
• Materials Science

Background:

• Altered tumor matrix mechanics are implicated in breast cancer development and progression.
• Tumor stiffness is a known indicator of malignancy, but its association with clinical aggressiveness is poorly understood.
• Existing tools lack the resolution and field of view to map mechanical properties in clinical tumor specimens.

Purpose of the Study:

• To introduce a novel tool, laser speckle rheological microscopy (SHEAR), for high-resolution mapping of viscoelastic properties in excised breast tumors.
• To investigate the correlation between tumor viscoelasticity and clinical hallmarks of breast cancer aggressiveness.
• To assess the prognostic value of mechanical properties derived from SHEAR measurements.

Main Methods:

• Development and application of laser Speckle rHEologicAl micRoscopy (SHEAR) to measure the magnitude viscoelastic or shear modulus (|G*(x,y,ω)|) across a range of frequencies.
• Analysis of 251 breast cancer specimens from 148 patients.
• Assessment of spatial variations in shear modulus and its gradient, particularly at the tumor invasive front.

Main Results:

• SHEAR successfully mapped |G*(x,y,ω)| in excised tumors with high spatial resolution (~50 μm) over large fields of view (cm²).
• Measured viscoelastic properties (|G*|) correlated with tumor histological features.
• Elevated spatial gradients of shear modulus (|∇|G*|) were observed at the tumor invasive front.
• Multivariate analyses indicated that |G*| and |∇|G*| are associated with patient prognosis.

Conclusions:

• Laser speckle rheological microscopy (SHEAR) provides unprecedented insights into the mechanical microenvironment of breast tumors.
• Tumor viscoelasticity is linked to histopathological subtype, grade, receptor status, and lymph node involvement.
• SHEAR-derived mechanical metrics hold prognostic value and may identify new therapeutic targets in breast cancer.