Project description:Lymphatic drainage generates force that induces prostate cancer cell motility via activation of Yes-associated protein (YAP), but whether this response to fluid force is conserved across cancer types is unclear. Here, we show that shear stress corresponding to fluid flow in the initial lymphatics modifies taxis in breast cancer. Whereas some cell lines employ rapid amoeboid migration behavior in response to fluid flow, a separate subset decrease movement. Positive responders displayed transcriptional profiles typical of an amoeboid cell state. Regulation of the HIPPO tumor suppressor pathway and YAP activity also differed between breast subsets and prostate cancer. Although subcellular localization of YAP to the nucleus positively correlated with overall velocity of locomotion, YAP gain- and loss-of-function demonstrates that YAP inhibits breast cancer motility but is outcompeted by other pro-taxis mediators in the context of flow. Specifically, we show that RhoA dictates response to flow. GTPase activity of RhoA, but not Rac1 or Cdc42 Rho family GTPases, is elevated in cells that positively respond to flow and is unchanged in cells that decelerate under flow. Disruption of RhoA or the RhoA effector, Rho-associated kinase (ROCK), blocked shear stress-induced motility. Collectively, these findings demonstrate stratification of breast cancer subsets by flow-sensing mechanotransduction pathways and point to a role for biophysical force in regulation of an amoeboid cell state.
Project description:Biophysical features of the microenvironment such as stiffness of extracellular matrix (ECM), nanotopography, and biomechanical force are critical regulators of cellular potential and behavior, yet the effects of extrinsic mechanical cues on tumor cells remain poorly understood. Here we demonstrate that frictional force, or wall shear stress (WSS), caused by fluid flow supports invasive behavior in cancer cells through activation of negative effectors of the Hippo tumor suppressor pathway, YAP and TAZ. In biomimetic models of lymphatic vasculature, WSS stimulated motility. These effects were accompanied by YAP dephosphorylation at ser-127, YAP and TAZ nuclear localization, and transactivation of YAP/TAZ downstream targets, including CTGF, AMOTL2, and ANKRD1. YAP, but not TAZ, was strictly required for WSS-enhanced motility, as knockdown of YAP or blockade of YAP-TEAD interactions by a small molecule inhibitor, verteporfin, reduced cellular velocity to levels observed in static controls. YAP-mediated effects on motility were dependent upon Rho-associated kinase (ROCK) and LIM-domain kinase (LIMK), as pharmacological inhibition of their activity led to activation of the actin-severing protein cofilin and blocked YAP dephosphorylation by WSS, thereby impairing migration. These data provide a signaling mechanism whereby biomechanical forces may influence cancer cell metastasis and implicate YAP as a core component of mechanosensitive machinery that modulates cancer progression.
Project description:Uncontrolled Transforming growth factor-beta (TGFβ) signaling promotes aggressive metastatic properties in late-stage breast cancers. However, how TGFβ-mediated cues are directed to induce late-stage tumorigenic events is poorly understood, particularly given that TGFβ has clear tumor suppressing activity in other contexts. Here we demonstrate that the transcriptional regulators TAZ and YAP (TAZ/YAP), key effectors of the Hippo pathway, are necessary to promote and maintain TGFβ-induced tumorigenic phenotypes in breast cancer cells. Interactions between TAZ/YAP, TGFβ-activated SMAD2/3, and TEAD transcription factors reveal convergent roles for these factors in the nucleus. Genome-wide expression analyses indicate that TAZ/YAP, TEADs and TGFβ-induced signals coordinate a specific pro-tumorigenic transcriptional program. Importantly, genes cooperatively regulated by TAZ/YAP, TEAD, and TGFβ, such as the novel targets NEGR1 and UCA1, are necessary for maintaining tumorigenic activity in metastatic breast cancer cells. Nuclear TAZ/YAP also cooperate with TGFβ signaling to promote phenotypic and transcriptional changes in non-tumorigenic cells to overcome TGFβ repressive effects. Our work thus identifies crosstalk between nuclear TAZ/YAP and TGFβ signaling in breast cancer cells, revealing novel insight into late-stage disease-driving mechanisms. Expression profiling was conducted following the repression of the transcriptional regulators TAZ and YAP (TAZ/YAP), the TEAD family of transcription factors (TEAD1/2/3/4), or the TGFb signaling pathway (with SB-431542, an inhibitor of the TBRI recpeptor) in human MDA-MB-231-LM2 breast cancer cells treated with TGFβ1. Human MDA-MB-231-LM2-4 breast cancer cells were transfected with control siRNA, or siRNAs targeting TAZ/YAP or all four TEADs and were treated 24 hours later with 500pM TGFβ1 or 5mM SB-431542 for an additional 24 hours. Total RNA was isolated and twelve microarrays in total were performed, with each condition carried out three times on separate days. The Boston University Microarray Core generated the data using the Affymetrix Human Gene 1.0 St Array.
Project description:Endothelial cell is the major cell type that senses and transduces mechanosignal generated by shear stress. We have recently shown that Hippo/YAP pathway is a mechanosensitive pathway that is critical for maintaining endothelial cell homeostasis. However, the transcritpional targets and biological functions of YAP in endothelial cells remain largely unknown. To evaluate YAP-dependent gene expression in endothelial cells, we performed RNA-sequencing in YAP depleted (by transfection with by YAP siRNA) and overexpressed (by infection with YAP-S127A catalytically active adenovirus) human endothelial cells. We observed that YAP critically regulates endothelial function by modulating multiple atherosclerosis-related genes. Our study provides mechanistic insights into the question how YAP regulates endothelial function and atherosclerosis by modulating endothelial transcriptional profile.
Project description:Endothelial cells (ECs) are constantly exposed to mechanical forces in the form of fluid shear stress, extracellular stiffness, and cyclic strain. How mechanical forces are transduced to the nucleus to drive transcriptional reprogramming in ECs is poorly understood. The mechanoresponsive activity of Yes associated protein (YAP) and its role in vascular development are well described, however, whether changes to transcription or epigenetic regulation of YAP are involved in these processes remains unanswered. Our results reveal that mechanical forces sensed at cell-cell junctions by the YAP target gene, Angiomotin-like 2 (AmotL2), are directly intervened into changes in global chromatin accessibility and EZH2 activity leading to modulation of YAP-promotor activity. Functionally, shear stress induced proliferation of ECs in vivo were reliant on AmotL2 and YAP/TAZ endothelial expression. Mechanistically, uncoupling of the nuclear-cytoskeletal connection from junctions and focal adhesions led to altered nuclear morphology, chromatin accessibility and suppression of YAP-promotor activity. Our findings reveal a role for AmotL2 and nuclear-cytoskeletal force transmission in modulating the epigenetic and transcriptional regulation of YAP to maintain a mechanoenforced positive-feedback loop of vascular homeostasis.
Project description:We are interested in the role of NOTCH1 and Shear Stress in Aortic Valve Endothelium. Primary human aortic valve endothelium was subjected to 4 conditions in vitro. 1) Control siRNA, No shear stress. 2) NOTCH1 siRNA, No shear stress. 3) Control siRNA, 15 dynes/cm2 shear stress. 4) NOTCH1 siRNA, 15 dynes/cm2 shear stress. Triplicates of each condition were pooled for library perp and sequencing