Hierarchy of TGFβ/SMAD, Hippo/YAP/TAZ, and Wnt/β-catenin signaling in melanoma phenotype switching

In melanoma, a switch from a proliferative melanocytic to an invasive mesenchymal phenotype is based on dramatic transcriptional reprogramming which involves complex interactions between a variety of signaling pathways and their downstream transcriptional regulators. TGFβ/SMAD, Hippo/YAP/TAZ, and Wnt/β-catenin signaling pathways are major inducers of transcriptional reprogramming and converge at several levels. Here, we report that TGFβ/SMAD, YAP/TAZ, and β-catenin are all required for a proliferative-to-invasive phenotype switch. Loss and gain of function experimentation, global gene expression analysis, and computational nested effects models revealed the hierarchy between these signaling pathways and identified shared target genes. SMAD-mediated transcription at the top of the hierarchy leads to the activation of YAP/TAZ and of β-catenin, with YAP/TAZ governing an essential subprogram of TGFβ-induced phenotype switching. Wnt/β-catenin signaling is situated further downstream and exerts a dual role: it promotes the proliferative, differentiated melanoma cell phenotype and it is essential but not sufficient for SMAD or YAP/TAZ–induced phenotype switching. The results identify epistatic interactions among the signaling pathways underlying melanoma phenotype switching and highlight the priorities in targets for melanoma therapy.

TAMI-30. THERAPY INDUCED REPROGRAMMING DRIVES GLIOMA VASCULAR TRANSDIFFERENTIATION AND TUMOR RECURRENCE

Therapy-resistant glioma cells elicit phenotypic plasticity leading to aggressive tumor recurrence. Here, we employed single-cell and whole transcriptomic analyses to uncover that a standard glioma treatment, radiation induces a dynamic shift in functional states of glioma cells allowing for acquisition of mesenchymal-like and vascular-like phenotypes. The predominant phenotype switch induced by radiation in surviving tumor cells is transdifferentiation to endothelial-like and pericyte-like cells. The transdifferentiated cells in turn promote proliferation of radiated tumor cells, and their selective depletion results in reduced tumor growth and recurrence post-treatment. The acquisition of vascular-like phenotype is driven by increased chromatin accessibility in vascular genes, and blocking P300-mediated histone acetyltransferase activity prior to radiation treatment inhibits vascular transdifferentiation and tumor growth. Our findings indicate that radiation therapy reprograms tumor cells driving vascular transdifferentiation, and highlights HAT inhibitors as potential therapeutic target for preventing GBM relapse

NLRP3 Inflammasome Mediates Immune-Stromal Interactions in Vasculitis

Rationale: NLRP3 (NLR family pyrin domain containing 3) activation and IL-1β (interleukin-1β) production are implicated in Kawasaki disease (KD) pathogenesis; however, a detailed and complete characterization of the molecular networks and cellular subsets involved in the development of cardiovascular lesions is still lacking. Objective: Here, in a murine model of KD vasculitis, we used single-cell RNA sequencing and spatial transcriptomics to determine the cellular landscape of inflamed vascular tissues. Methods and Results: We observe infiltrations of innate and adaptive immune cells in murine KD cardiovascular lesions, associated with increased expression of Nlrp3 and Il1b . Monocytes, macrophages, and dendritic cells were the main sources of IL-1β, whereas fibroblasts and vascular smooth muscle cells (VSMCs) expressed high levels of IL-1 receptor. VSMCs type 1 surrounding the inflamed coronary artery undergo a phenotype switch to become VSMCs type 2, which are characterized by gene expression changes associated with decreased contraction and enhanced migration and proliferation. Genetic inhibition of IL-1β signaling on VSMCs efficiently attenuated the VSMCs type 2 phenotypic switch and the development of cardiovascular lesions during murine KD vasculitis. In addition, pharmacological inhibition of NLRP3 prevented the development of cardiovascular inflammation. Conclusions: Our studies unravel the cellular diversity involved in IL-1β production and signaling in murine KD cardiovascular lesions and provide the rationale for therapeutic strategies targeting NLRP3 to inhibit cardiovascular lesions associated with KD.

Circ_TGFBR2 Inhibits Vascular Smooth Muscle Cells Phenotypic Switch and Suppresses Aortic Dissection Progression by Sponging miR-29a

Background: Aortic dissection (AD) is a threatening and catastrophic vascular disease with high mortality rate and limited therapeutic strategies. There is emerging evidence showing that circular RNAs play crucial role in regulating various cardiovascular diseases. However, the biological functions and molecular mechanisms of circRNAs in AD still remains elusive. The purpose of this study was to illustrate the potential functional roles and mechanisms of hsa_circ_0064654(circ_TGFBR2) in vitro and in vivo.Methods:The vascular smooth muscle cells (VSMCs) and AD-VSMCs were isolated from normal aorta and AD tissues. The expression of circ_TGFBR2, miR-29a and KLF4 were detected by Realtime Polymerase Chain Reaction (RT-PCR) and Fluorescence in situ hybridization (FISH). Cell proliferation was assessed by CCK-8 assay, colony formation and EDU assay. Cell migration was evaluated through transwell assay. Dual-luciferase reporter assay and RNA pulldown were performed to identify the interaction among circ_TGFBR2, miR-29a and KLF4. Western Blot measured the expression of phenotype switch-related proteins. AD rat model induced by (β-Aminopropionitrile monofumarate) BAPN was used to verify the role and mechanism of circ_TGFBR2.Results: Circ_TGFBR2 inhibited cell proliferation and migration of AD-VSMCs cells. Overexpression of circ_TGFBR2 promoted the expression of contractile markers(α-SMA，SM22α) and inhibited the expression of synthetic markers (MGP,OPN) in AD-VSMCs cells. Circ_TGFBR2 served as a sponge for miR-29a targeting KLF4. MiR-29a mimics rescue biological roles induced by circ_TGFBR2 overexpression. The results of in vivo experiments were consistent with in vitro experiments.Conclusion:Our study revealed that circ_TGFBR2 regulated VSMCs phenotype switch and suppressed the progression of AD.

Epigenetic control of melanoma cell invasiveness by the stem cell factor SALL4

Melanoma cells rely on developmental programs during tumor initiation and progression. Here we show that the embryonic stem cell (ESC) factor Sall4 is re-expressed in the Tyr::NrasQ61K; Cdkn2a−/− melanoma model and that its expression is necessary for primary melanoma formation. Surprisingly, while Sall4 loss prevents tumor formation, it promotes micrometastases to distant organs in this melanoma-prone mouse model. Transcriptional profiling and in vitro assays using human melanoma cells demonstrate that SALL4 loss induces a phenotype switch and the acquisition of an invasive phenotype. We show that SALL4 negatively regulates invasiveness through interaction with the histone deacetylase (HDAC) 2 and direct co-binding to a set of invasiveness genes. Consequently, SALL4 knock down, as well as HDAC inhibition, promote the expression of an invasive signature, while inhibition of histone acetylation partially reverts the invasiveness program induced by SALL4 loss. Thus, SALL4 appears to regulate phenotype switching in melanoma through an HDAC2-mediated mechanism.

An Association of Vitamins A and E with Hyaluronic and Lactobionic Acids may Prevent Molecular Changes Associated with Keratocyte to Myofibroblast Transition

Inflammatory events in the corneal stroma may activate keratocytes and trigger their transition towards myofibroblasts, which now produce different extracellular matrix (ECM) proteins thus causing corneal opacification.Corneal haze is a frequent side effect after photorefractive keratectomy (PRK) to correct high myopia.Currently, a preventive treatment with mitomycin-c can be used to limit the occurrence of this phenomenon. However, mitomycin-c is a toxic drug, not devoid of side effects, which may occasionally involve the corneal endothelium. Therefore, we have searched for a less risky, natural way, to prevent keratocytes transition. To this purpose, we have used as markers of the phenotype switch the proteins lumican (highly expressed by keratocytes and much less by myofibroblasts) and smooth muscle actin (αSMA) (highly expressed by myofibroblasts and poorly found in keratocytes), beside Fibronectin (Fn), the expression of which is also increased by transforming growth factor-beta (TGFβ treatment. Treatment of human keratocytes with TGFβ was used to induce the protein shift. Among different possible candidates, we have found that vitamins A and E, hyaluronic and lactobionic acids may prevent, either alone, or much better in association, the shift in the ratio between lumican and αSMA and the increased Fn expression. In conclusion, it could be speculated that topic treatment of the ocular surface with an association of these four compounds could be able to prevent or at least limit the occurrence of post-PRK corneal haze, with the additional advantage of lubrication, hydration and antioxidant defense exerted by these molecules.

Digital twinning of Cellular Capsule Technology: Emerging outcomes from the perspective of porous media mechanics

Spheroids encapsulated within alginate capsules are emerging as suitable in vitro tools to investigate the impact of mechanical forces on tumor growth since the internal tumor pressure can be retrieved from the deformation of the capsule. Here we focus on the particular case of Cellular Capsule Technology (CCT). We show in this contribution that a modeling approach accounting for the triphasic nature of the spheroid (extracellular matrix, tumor cells and interstitial fluid) offers a new perspective of analysis revealing that the pressure retrieved experimentally cannot be interpreted as a direct picture of the pressure sustained by the tumor cells and, as such, cannot therefore be used to quantify the critical pressure which induces stress-induced phenotype switch in tumor cells. The proposed multiphase reactive poro-mechanical model was cross-validated. Parameter sensitivity analyses on the digital twin revealed that the main parameters determining the encapsulated growth configuration are different from those driving growth in free condition, confirming that radically different phenomena are at play. Results reported in this contribution support the idea that multiphase reactive poro-mechanics is an exceptional theoretical framework to attain an in-depth understanding of CCT experiments, to confirm their hypotheses and to further improve their design.

OMRT-5. Therapy-induced reprogramming drives glioma vascular transdifferentiation and recurrence

Therapy-resistant glioma cells elicit remarkable phenotypic plasticity leading to aggressive tumor recurrence. Here, we used single-cell and whole transcriptomic sequencing to uncover that radiation treatment induces a dynamic shift in functional states of glioma cells allowing for acquisition of either stem-like, mesenchymal-like or vascular-like phenotypes. The predominant phenotype switch induced by radiation in surviving tumor cells is the vascular-like cell state, resulting in transdifferentiation to endothelial-like and pericyte-like cells in distinct cell clusters. The transdifferentiated endothelial-like and pericyte-like cells secrete trophic factors to support proliferation of tumor cells, and their selective ablation results in reduced tumor growth and recurrence post-treatment. Mechanistically, the acquisition of vascular-like phenotype is driven by increased acetylation and chromatin accessibility in vascular genes and in regions for binding of vascular specification transcription factors. Blocking histone acetylation using a small molecule inhibitor targeting P300 histone acetyltransferase activity prior to radiation treatment inhibits the vascular-like transdifferentiation of glioma cells and tumor growth. Our findings indicate that radiation therapy-induces rewiring of glioma cells that promotes vascular cell-like transdifferentiation, tumor growth and recurrence.