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

The mechanobiology is providing novel perspectives in the study of cancer and is contributing to evaluate the cancer responses, from a biophysical point of view, to classical therapeutic approaches- radiotherapy and chemotherapy. Here we have explored the effects of two doses (4 and 8 Gy) of 6 MeV photons on spreading, focal adhesions, migration and mechanical properties of BALB/c 3T3 and their SV40 transformed equivalent, SVT2. Cell biophysical responses to 4 and 8 Gy were analysed and compared with those reported in previous published work when lower doses (1 and 2 Gy) were administered Panzetta et al. (Effects of high energy X-rays on cell morphology and functions. Proc. Book 2017;16:116). We observed that the range of sensitivity to ionising radiations profoundly changes depending on the patho-physiological state of cells. In particular, we found that X-rays induce morphological and functional variations in both cell lines (decreased motility, increased adhesion and increased cytoskeleton stiffness). These changes were slightly dependent on doses in the case of SVT2 cells and may indicate a possible mechanical normalisation in their phenotype. Nevertheless, the responses of BALB/c 3T3 were negligible only for the low dose of 1 Gy and increased significantly in a dose-dependent manner with higher doses. We believe that the characterisation of X-rays effects on the cell mechanobiology could shed new light in the design and customisation of radiotherapy treatments.

Wnt4 inhibits cell motility induced by oncogenic Ras.

Aberrant motility and invasive ability are relevant hallmarks of malignant tumor cells. Pathways regulating the movement of cancer cells from the site of primary tumor toward adjacent and/or distant tissues are not entirely defined. By using a model of malignant transformation induced by Ras, we identified Wnt4 as an early target of Ras oncogenic signaling. Here we show that Wnt4 is repressed by Ras and that forced Wnt4 expression inhibits Ras-induced cell motility. Accordingly, we found that Wnt4 is downregulated in human anaplastic thyroid carcinomas, the most malignant and metastatic thyroid cancer histotype. Wnt4 interferes with Ras-induced actin cytoskeleton reorganization through non-canonical pathways, by altering the balance between the activation of different Rho-family small guanosine triphosphatases (GTPases). Finally, we demonstrate that Wnt4 is post-transcriptionally repressed by miR-24, a Ras-induced micro RNA (miRNA) targeting the 3'-untranslated region (UTR) of Wnt4. Taken together our data highlight a novel Ras-regulated miRNA-dependent circuitry regulating the motile phenotype of cancer cells.

Upregulation of miR-21 by Ras in vivo and its role in tumor growth.

miR-21 is a microRNA (miRNA) frequently overexpressed in human cancers. Here we show that miR-21 is upregulated both in vitro and in vivo by oncogenic Ras, thus linking this miRNA to one of the most frequently activated oncogenes in human cancers. Ras regulation of miR-21 occurs with a delayed kinetic and requires at least two Ras downstream pathways. A screen of human thyroid cancers and non-small-cell lung cancers for the expression of miR-21 reveals that it is overexpressed mainly in anaplastic thyroid carcinomas, the most aggressive form of thyroid cancer, whereas in lung its overexpression appears to be inversely correlated with tumor progression. We also show that a LNA directed against miR-21 slows down tumor growth in mice. Consistently, a search for mRNAs downregulated by miR-21 shows an enrichment for mRNAs encoding cell cycle checkpoints regulators, suggesting an important role for miR-21 in oncogenic Ras-induced cell proliferation.