Tumors are stiff and data suggest that the extracellular matrix stiffening that correlates with experimental mammary malignancy drives tumor invasion and metastasis. Nevertheless, the relationship between tissue and extracellular matrix stiffness and human breast cancer progression and aggression remains unclear. We undertook a biophysical and biochemical assessment of stromal–epithelial interactions in noninvasive, invasive and normal adjacent human breast tissue and in breast cancers of increasingly aggressive subtype. Our analysis revealed that human breast cancer transformation is accompanied by an incremental increase in collagen deposition and a progressive linearization and thickening of interstitial collagen. The linearization of collagen was visualized as an overall increase in tissue birefringence and was most striking at the invasive front of the tumor where the stiffness of the stroma and cellular mechanosignaling were the highest. Amongst breast cancer subtypes we found that the stroma at the invasive region of the more aggressive Basal-like and Her2 tumor subtypes was the most heterogeneous and the stiffest when compared to the less aggressive luminal A and B subtypes. Intriguingly, we quantified the greatest number of infiltrating macrophages and the highest level of TGF beta signaling within the cells at the invasive front. We also established that stroma stiffness and the level of cellular TGF beta signaling positively correlated with each other and with the number of infiltrating tumor-activated macrophages, which was highest in the more aggressive tumor subtypes. These findings indicate that human breast cancer progression and aggression, collagen linearization and stromal stiffening are linked and implicate tissue inflammation and TGF beta.

/pdf/human-breast-cancer-invasion-and-aggression-correlates-with-34trfn6aqu.pdf

Human Breast Cancer Invasion and Aggression Correlates with ECM Stiffening and Immune Cell Infiltration

Atomic force microscopy (AFM) is a powerful, multifunctional imaging platform that allows biological samples, from single molecules to living cells, to be visualized and manipulated. Soon after the instrument was invented, it was recognized that in order to maximize the opportunities of AFM imaging in biology, various technological developments would be required to address certain limitations of the method. This has led to the creation of a range of new imaging modes, which continue to push the capabilities of the technique today. Here, we review the basic principles, advantages and limitations of the most common AFM bioimaging modes, including the popular contact and dynamic modes, as well as recently developed modes such as multiparametric, molecular recognition, multifrequency and high-speed imaging. For each of these modes, we discuss recent experiments that highlight their unique capabilities.

/pdf/imaging-modes-of-atomic-force-microscopy-for-application-in-3wyx0p8xt4.pdf

Imaging modes of atomic force microscopy for application in molecular and cell biology

Modes of cancer cell invasion and the role of the microenvironment

https://www.cell.com/cell/pdf/S0092-8674(14)00924-6.pdf

Probing the Stochastic, Motor-Driven Properties of the Cytoplasm Using Force Spectrum Microscopy

Mechanobiology emerges at the crossroads of medicine, biology, biophysics and engineering and describes how the responses of proteins, cells, tissues and organs to mechanical cues contribute to development, differentiation, physiology and disease. The grand challenge in mechanobiology is to quantify how biological systems sense, transduce, respond and apply mechanical signals. Over the past three decades, atomic force microscopy (AFM) has emerged as a key platform enabling the simultaneous morphological and mechanical characterization of living biological systems. In this Review, we survey the basic principles, advantages and limitations of the most common AFM modalities used to map the dynamic mechanical properties of complex biological samples to their morphology. We discuss how mechanical properties can be directly linked to function, which has remained a poorly addressed issue. We outline the potential of combining AFM with complementary techniques, including optical microscopy and spectroscopy of mechanosensitive fluorescent constructs, super-resolution microscopy, the patch clamp technique and the use of microstructured and fluidic devices to characterize the 3D distribution of mechanical responses within biological systems and to track their morphology and functional state. Mechanobiology describes how biological systems respond to mechanical stimuli. This Review surveys basic principles, advantages and limitations of applying and combining atomic force microscopy-based modalities with complementary techniques to characterize the morphology, mechanical properties and functional response of complex biological systems to mechanical cues.

/pdf/atomic-force-microscopy-based-mechanobiology-jk5sz42kpo.pdf

Atomic force microscopy-based mechanobiology

Cancer initiation and progression follow complex molecular and structural changes in the extracellular matrix and cellular architecture of living tissue. However, it remains poorly understood how the transformation from health to malignancy alters the mechanical properties of cells within the tumour microenvironment. Here, we show using an indentation-type atomic force microscope (IT-AFM) that unadulterated human breast biopsies display distinct stiffness profiles. Correlative stiffness maps obtained on normal and benign tissues show uniform stiffness profiles that are characterized by a single distinct peak. In contrast, malignant tissues have a broad distribution resulting from tissue heterogeneity, with a prominent low-stiffness peak representative of cancer cells. Similar findings are seen in specific stages of breast cancer in MMTV-PyMT transgenic mice. Further evidence obtained from the lungs of mice with late-stage tumours shows that migration and metastatic spreading is correlated to the low stiffness of hypoxia-associated cancer cells. Overall, nanomechanical profiling by IT-AFM provides quantitative indicators in the clinical diagnostics of breast cancer with translational significance.

https://www.cell.com/biophysj/pdf/S0006-3495(12)03025-1.pdf

The nanomechanical signature of breast cancer

Biointerfaces capable of biological recognition and specificity are sought after for conferring bioinspired functionality onto synthetic biomaterials systems. This is important for biosensing, bioseparations, and biomedical materials. Here, we demonstrate how intrinsic polymer–protein interactions between highly localized polyethylene glycol (PEG) brushes and PEG-binding antibodies can be used for sorting specific biomolecules from complex bulk biological fluids to synthetic nanoscale targets. A principal feature lies with the antifouling property of PEG that prevents unspecific binding. Exclusive access is provided by anti-PEG, which acts as a biohybrid molecular adaptor that sifts out and targets specific IgG “cargo” from solution to the PEG. The PEG can be reversibly washed and targeted in blood serum, which suggests potential benefits in technological applications. Moreover, anti-PEG binding triggers a stimuli-responsive conformational collapse in the PEG brush, thereby imparting an intrinsic “smart” ...

Synthetic Protein Targeting by the Intrinsic Biorecognition Functionality of Poly(ethylene glycol) Using PEG Antibodies as Biohybrid Molecular Adaptors

Contributions of the lower dimer to supramolecular actin patterning revealed by TIRF microscopy.

Atomic force microscopy (AFM) is a stylus-based technique that uses sub-nanonewton force sensitivity to image surfaces at sub-nanometer resolution. As a surface-sensitive tool, AFM is ideal for investigating the properties and local morphology of surface-grafted supramolecules and (bio)polymers, which play important roles in mediating interfacial processes ranging from tribology to colloidal stability and biology. Moreover, the versatility of AFM to operate in diverse environments (i.e., air, liquid, or vacuum) adds to its appeal in comparison to other surface methods. Given its capability for high-resolution imaging, force measurements, and nanomechanical manipulation, AFM is directly applicable to studies of stimuli-responsive polymers, biomaterials, and polymeric nanostructures.


Keywords:

atomic force microsope (AFM);
nanomechanics;
biomaterials;
stimuli-responsive polymers;
polymer brush;
nanostructure;
biointerfaces

Janne T. Hyotyla

Papers

The nanomechanical signature of breast cancer

Synthetic Protein Targeting by the Intrinsic Biorecognition Functionality of Poly(ethylene glycol) Using PEG Antibodies as Biohybrid Molecular Adaptors

Contributions of the lower dimer to supramolecular actin patterning revealed by TIRF microscopy.

Atomic Force Microscopy (AFM)