A BIOPHYSICAL ANALYSIS TO ASSESS X-RAY SENSITIVITY OF HEALTHY AND TUMOUR CELLS

Impact of ionizing radiation on cell-ECM mechanical crosstalk in breast cancer

The stiffness of the extracellular matrix plays a crucial role in cell motility and spreading, influencing cell morphology through cytoskeleton organization and transmembrane proteins' expression. In this context, mechanical characterization of both cells and the extracellular matrix gains prominence for enhanced diagnostics and clinical decision-making. Here, we investigate the combined effect of mechanotransduction and ionizing radiations on altering cells' mechanical properties, analysing mammary cell lines (MCF10A and MDA-MB-231) after X-ray radiotherapy (2 and 10 Gy). We found that ionizing radiations sensitively affect adenocarcinoma cells cultured on substrates mimicking cancerous tissue stiffness (15 kPa), inducing an increased structuration of paxillin-rich focal adhesions and cytoskeleton: this process translates in the augmentation of tension at the actin filaments level, causing cellular stiffness and consequently affecting cytoplasmatic/nuclear morphologies. Deeper exploration of the intricate interplay between mechanical factors and radiation should provide novel strategies to orient clinical outcomes.

Role of the mechanical microenvironment on CD-44 expression of breast adenocarcinoma in response to radiotherapy

The biological effects of ionizing radiation are exploited in the clinical practice of radiotherapy to destroy tumour cells while sparing the surrounding normal tissue. While most of the radiotherapy research focused on DNA damage and repair, recently a great attention is going to cells' interactions with the mechanical microenvironment of both malignant and healthy tissues after exposure. In fact, the stiffness of the extracellular matrix can modify cells' motility and spreading through the modulation of transmembrane proteins and surface receptors' expression, such as CD-44. CD-44 receptor has held much interest also in targeted-therapy due to its affinity with hyaluronic acid, which can be used to functionalize biodegradable nanoparticles loaded with chemotherapy drugs for targeted therapy. We evaluated changes in CD-44 expression in two mammary carcinoma cell lines (MCF10A and MDA-MB-231) after exposure to X-ray (2 or 10 Gy). To explore the role of the mechanical microenvironment, we mimicked tissues' stiffness with polyacrylamide's substrates producing two different elastic modulus values (0.5 and 15 kPa). We measured a dose dependent increase in CD-44 relative expression in tumour cells cultured in a stiffer microenvironment. These findings highlight a crucial connection between the mechanical properties of the cell's surroundings and the post-radiotherapy expression of surface receptors.

Cytoskeleton Response to Ionizing Radiation: A Brief Review on Adhesion and Migration Effects

The cytoskeleton is involved in several biological processes, including adhesion, motility, and intracellular transport. Alterations in the cytoskeletal components (actin filaments, intermediate filaments, and microtubules) are strictly correlated to several diseases, such as cancer. Furthermore, alterations in the cytoskeletal structure can lead to anomalies in cells’ properties and increase their invasiveness. This review aims to analyse several studies which have examined the alteration of the cell cytoskeleton induced by ionizing radiations. In particular, the radiation effects on the actin cytoskeleton, cell adhesion, and migration have been considered to gain a deeper knowledge of the biophysical properties of the cell. In fact, the results found in the analysed works can not only aid in developing new diagnostic tools but also improve the current cancer treatments.

Adhesion and Migration Response to Radiation Therapy of Mammary Epithelial and Adenocarcinoma Cells Interacting with Different Stiffness Substrates

The structural and mechanical properties of the microenvironmental context have a profound impact on cancer cell motility, tumor invasion, and metastasis formation. In fact, cells react to their mechanical environment modulating their adhesion, cytoskeleton organization, changes of shape, and, consequently, the dynamics of their motility. In order to elucidate the role of extracellular matrix stiffness as a driving force in cancer cell motility/invasion and the effects of ionizing radiations on these processes, we evaluated adhesion and migration as biophysical properties of two different mammary cell lines, over a range of pathophysiological stiffness (1-13 kPa) in a control condition and after the exposure to two different X-ray doses (2 and 10 Gy, photon beams). We concluded that the microenvironment mimicking the normal mechanics of healthy tissue has a radioprotective role on both cell lines, preventing cell motility and invasion. Supraphysiological extracellular matrix stiffness promoted tumor cell motility instead, but also had a normalizing effect on the response to radiation of tumor cells, lowering their migratory capability. This work lays the foundation for exploiting the extracellular matrix-mediated mechanism underlying the response of healthy and tumor cells to radiation treatments and opens new frontiers in the diagnostic and therapeutic use of radiotherapy.