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Cutaneous lesions are one of the hallmarks of tuberous sclerosis complex (TSC), a genetic disease in which mTOR is hyperactivated due to the lack of hamartin or tuberin. To date, novel pharmacological treatments for TSC cutaneous lesions that are benign but still have an impact on a patient's life are needed, because neither surgery nor rapamycin administration prevents their recurrence. Here, we demonstrated that primary TSC2

Senescence is a stress-response process characterized by the irreversible inhibition of cell proliferation, associated to the acquisition of a senescence-associated secretory phenotype (SASP), that may drive pathological conditions. Lymphangioleiomyomatosis (LAM) is a rare disease in which LAM cells, featuring the hyperactivation of the mammalian Target of Rapamycin Complex 1 (mTORC1) for the absence of tuberin expression, cause the disruption of the lung parenchyma. Considering that LAM cells secrete SASP factors and that mTOR is also a driver of senescence, we deepened the contribution of senescence in LAM cell phenotype. We firstly demonstrated that human primary tuberin-deficient LAM cells (LAM/TSC cells) have senescent features depending on mTOR hyperactivation, since their high positivity to SA-β galactosidase and to phospho-histone H2A.X are reduced by inducing tuberin expression and by inhibiting mTOR with rapamycin. Then, we demonstrated the capability of LAM/TSC cells to induce senescence. Indeed, primary lung fibroblasts (PLFs) grown in LAM/TSC conditioned medium increased the positivity to SA-β galactosidase and to phospho-histone H2A.X, as well as p21WAF1/CIP1 expression, and enhanced the mRNA expression and the secretion of the SASP component IL-8. Taken together, these data make senescence a novel field of study to understand LAM development and progression.

Melanoma progression is generally associated with increased transcriptional activity mediated by the Yes‐associated protein (YAP). Mechanical signals from the extracellular matrix are sensed by YAP, which then activates the expression of proliferative genes, promoting melanoma progression and drug resistance. Which extracellular signals induce mechanotransduction, and how this is mediated, is not completely understood. Here, using secretome analyses, we reveal the extracellular accumulation of amyloidogenic proteins, i.e. premelanosome protein (PMEL), in metastatic melanoma, together with proteins that assist amyloid maturation into fibrils. We also confirm the accumulation of amyloid‐like aggregates, similar to those detected in Alzheimer disease, in metastatic cell lines, as well as in human melanoma biopsies. Mechanistically, beta‐secretase 2 (BACE2) regulates the maturation of these aggregates, which in turn induce YAP activity. We also demonstrate that recombinant PMEL fibrils are sufficient to induce mechanotransduction, triggering YAP signaling. Finally, we demonstrate that BACE inhibition affects cell proliferation and increases drug sensitivity, highlighting the importance of amyloids for melanoma survival, and the use of beta‐secretase inhibitors as potential therapeutic approach for metastatic melanoma., The accumulation of PMEL fibrils in the metastatic melanoma microenvironment modulates YAP activity. Preventing aggregate formation reduces metastatic cell proliferation and chemosensitivity, suggesting beta‐secretase inhibition as treatment for metastatic melanoma.

Melanoma progression is generally associated to increased Yes-associated protein (YAP) mediated transcription. Actually, mechanical signals from the extracellular matrix are sensed by YAP, which activates proliferative genes expression, promoting melanoma progression and drug resistance. Which and how extracellular signals induce mechanotransduction is not completely understood.Herein, by secretome studies, we revealed an extracellular accumulation of amyloidogenic proteins, i.e. premelanosome protein (PMEL), together with proteins that assist amyloids maturation into fibrils. Indeed, we confirmed the presence of amyloid-like aggregates similar to those detected in Alzheimer disease. These aggregates were enriched in metastatic cell lines as well as in human melanoma biopsies, compared to their primitive counterpart. Mechanistically, we proved that beta-secretase (BACE) regulates the maturation of these aggregates and that its inhibition hampers YAP activity. Moreover, recombinant PMEL fibrils induce per se mechanotransduction promoting YAP activation. Finally, BACE inhibition affects cell proliferation and increases drug sensitivity. These results highlight the importance of amyloids for melanoma survival and the potential of beta-secretase inhibitors as new therapeutic approach to metastatic melanoma.