Caeiro, J. R. | bioRxiv Science

bioRxiv2024

Cx43 Enhances Response to BRAF/MEK Inhibitors by Reducing DNA Repair Capacity

BRAF and MEK inhibitors (BRAF/MEKi) have radically changed the treatment landscape of advanced BRAF mutation-positive tumours. However, limited efficacy and emergence of drug resistance are major handicaps for successful treatments. Here, by using relevant preclinical models, we found that Connexin43 (Cx43), a protein that plays a role in cell-to-cell communication, increases effectiveness of BRAF/MEKi by recruiting DNA repair complexes to lamin-associated domains and promoting persistent DNA damage and cellular senescence. The nuclear compartmentalization promoted by Cx43 contributes to genome instability and synthetic lethality caused by excessive DNA damage, which could lead to a novel therapeutic approach for these tumours to overcome drug resistance. Based on these findings, we designed an innovative drug combination using small extracellular vesicles (sEVs) to deliver the full-Cx43 in combination with the BRAF/MEKi. This study reveals Cx43 as a new player on DNA repair and BRAF/MEKi response, underlining the therapeutical potential that this approach could eventually have in the clinic to overcome the limitations of current therapies and improve treatment outcomes for patients with advanced BRAF mutant tumours.

cancer biology↗

bioRxiv2019

Senolytic activity of small molecular polyphenols from olive restores chondrocyte redifferentiation and cartilage regeneration in osteoarthritis

Osteoarthritis (OA) is the most prevalent disorder of articulating joints and a leading cause of disability in humans, affecting half of the worlds population aged 65 years or older. Articular cartilage and synovial tissue from OA patients show an overactivity of the membrane channel protein connexin43 (Cx43) and accumulation of senescent cells associated with disrupted tissue regeneration. We have recently demonstrated the use of the Cx43 as an appropriate therapeutic target to halt OA progression by decreasing the accumulation of senescent cells and by triggering redifferentiation of osteoarthritic chondrocytes (OACs) into a more differentiated state, restoring the fully mature phenotype and cartilage regeneration. In this study we have found that small molecular polyphenols derived by olive extracts target Cx43 and senescence in OACs, synovial and bone cells from patients and in human mesenchymal stem cells (hMSCs). Our results indicate that these small molecules including oleuropein regulate the promoter activity of Cx43 gene. The downregulation of Cx43 expression by oleuropein reduce gap junction intercellular communication, cellular senescence in chondrocytes and enhance the propensity of hMSCs to differentiate into chondrocytes and bone cells, reducing adipogenesis. In concordance with these results, these small molecules reduce Cx43 and decrease Twist-1 activity leading to redifferentiation of OACs, which restores the synthesis of cartilage ECM components (Col2A1 and proteoglycans) and reduces inflammatory and catabolic factors IL-1{beta}, IL-6, COX-2 and MMP-3 and cellular senescence orchestrated by p53/p21 together with the synthesis of SASP via NF-kB. Altogether, our results demonstrate the use of the olive-derived polyphenols such as oleuropein as potentially effective therapeutic agents to enhance the efficacy of hMSC therapy and to induce a pro-regenerative environment in OA patients by restoring cellular phenotype and clearing out senescent cells in joint tissues in order to stop or prevent the progression of the disease.

cell biology↗