Dottorato in SCIENZE DELLA VITA

Titolo della tesi: 1/2 HDACs inhibition impacts mesenchymal-like mesothelial cells/ovary cancer adhesive interactions inhibiting α5β1 Integrin activation.

Peritoneal metastasis accounts for 85% of all epithelial ovarian carcinoma (EOC) metastases and is a main route from other primary tumors emerging in the peritoneal cavity, such as gastrointestinal cancers. Peritoneal metastasis is a multistep process requiring firstly the establishment of adhesive interactions between cancer cells and the peritoneal membrane. Although it has been demonstrated that the acquisition of EMT-like features by peritoneum mesothelial cells (MCs), a process known as mesothelial to mesenchymal transition (MMT), facilitates the metastatic process, this process of ‘peritoneal education’ by cancer cells has been incompletely studied. Here, we analyzed the epigenetic regulation of MC-EOC adesion, focusing on the plasticity of the MC monolayer. Published evidence demonstrates the ability of HDAC inhibition in promoting the reversal towards an epithelial-like phenotype in MCs. Here, we found that treatment of fibrotic MCs and platinum-resistant EOC lines with MS-275, an HDAC1-3 pharmacological inhibitor, significantly limits MCs/EOC adhesion. This process was reproduced by HDAC1 genetic silencing. When analyzing molecular mechanisms underlying, we focused on the expression of ECM molecules and in the analysis of Integrin subunits responsible for MCs/EOC adhesion. Proteomic analysis revealed a number of molecular pathways altered upon treatment of MCs with MS-275, including ECM molecules, adhesion receptors and actin cytoskeleton regulators. Experiments of genetic silencing, use of specific pharmacological inhibitors and inhibitory antibodies led us to draw two possibly integrating mechanisms: i. downregulated metalloproteinase (MMP) expression leading to abnormal Fibronectin (FN-1) fiber formation and provoking defective adhesion; ii. alteration of actin cytoskeleton polymerization due to downregulation of actin regulator TALIN-1 leading to defective α5β1 Integrin activation. These studies focusing on the epigenetic regulation of MCs plasticity, provide a new mechanism of action of HDAC-1 inhibition and open to a new perspective for EOC therapeutic intervention.