Biology subjects

Ho, K. K. Y.

Publications and source records attributed to Ho, K. K. Y..

5 recordsLinked to original sources

bioRxiv2025

Substrate stiffness regulates triple-negative breast cancer signaling through CXCR4 receptor dynamics

Biophysical properties of the extracellular matrix (ECM), such as mechanical stiffness, directly regulate behaviors of cancer cells linked to cancer initiation and progression. Cells sense and respond to ECM stiffness in the context of dynamic changes in biochemical inputs, such as growth factors and chemokines. While commonly studied as isolated inputs, mechanisms by which combined effects of mechanical stiffness and biochemical factors affect functions of cancer cells remain poorly defined. Using a combination of elastically supportive surface (ESS) culture dishes with defined stiffnesses and single-cell imaging, we report here that culturing cells on a stiff (28 kPa) versus soft (1.5 kPa) substrate increases CXCR4 and EGFR expression and promotes greater ligand-dependent internalization of CXCR4. In addition to increased CXCR4 expression, a stiff ECM also increases basal activation of Akt and ERK as well as signaling through these kinases in response to CXCL12- and EGF and promotes migration of triple negative breast cancer (TNBC) cells. These data implicate receptor dynamics as a key mediator of Akt and ERK signaling as a mechanism for adverse effects of enhanced ECM stiffness on disease progression in TNBC.

cancer biology↗

bioRxiv2022

Cell-to-cell variability of dynamic CXCL12-CXCR4 signaling and morphological processes in chemotaxis

Chemotaxis drives critical processes in cancer metastasis. While commonly studied at the population scale, metastasis arises from small numbers of cells that successfully disseminate, underscoring the need to analyze chemotaxis at single-cell resolution. Here we focus on chemotaxis driven by the CXCL12-CXCR4 pathway, a signaling network that promotes metastasis in more than 20 different human cancers. CXCL12-CXCR4 activates ERK and Akt, kinases known to promote chemotaxis, but how cells couple signaling to chemotaxis remain poorly defined. To address this challenge, we implemented single-cell analysis of MDA-MB-231 breast cancer cells migrating in a chemotaxis device towards chemokine CXCL12. We integrated live, single-cell imaging with advanced computational analysis methods to discover processes defining subsets of cells that move efficiently toward a CXCL12 gradient. We identified dynamic oscillations in ERK and Akt signaling and associated morphological transitions as key determinants of successful chemotaxis. Cells with effective chemotaxis toward CXCL12 exhibit faster and more persistent movement than non-migrating cells, but both cell populations show similar random motion. Migrating cells exhibit higher amplitude fluctuations in ERK and Akt signaling and greater frequencies of generating lateral cell membrane protrusions. Interestingly, computational analysis reveals less correlated network coupling of signaling and morphological changes in migrating cells. These data reveal processing events that enable cells to convert a signaling input to chemotaxis and highlight how cells in a uniform environment produce heterogeneous responses.

cancer biology↗

bioRxiv2021

Biomechanics and Myofibrillar Alignment Enhance Contractile Development and Reproducibility in Stem Cell Derived Cardiac Muscle

Human pluripotent stem cell derived cardiomyocytes (hPSC-CMs) allow novel investigations of human cardiac disease, but disorganized mechanics and immaturity of hPSC-CMs on two-dimensional (2D) surfaces have been hurdles for efficient and reproducible study of these cells. Here, we developed a platform of micron-scale 2D cardiac tissues (M2DCTs) to precisely control biomechanics in arrays of thousands of purified, independently contracting cardiac muscle strips in 2D. By defining geometry and workload in M2DCTs in this reductionist platform that does not incorporate other cell types, we show that myofibrillar alignment and auxotonic contractions at physiologic workload critically drive maturation of cardiac contractile function, calcium handling, and electrophysiology. Additionally, the organized biomechanics in this system facilitates rapid and automated extraction of contractile kinetic parameters from brightfield microscopy images, increasing the reproducibility and throughput of pharmacologic testing. Finally, we show that M2DCTs enable precise and efficient dissection of contractile kinetics in cardiomyopathy disease models.

cell biology↗

bioRxiv2019

Compressive Stress Enhances Invasive Phenotype of Cancer Cells via Piezo1 Activation

Uncontrolled growth in solid tumor generates compressive stress that drives cancer cells into invasive phenotypes, but little is known about how such stress affects the invasion and matrix degradation of cancer cells and the underlying mechanisms. Here we show that compressive stress enhanced invasion, matrix degradation, and invadopodia formation of breast cancer cells. We further identified Piezo1 channels as the putative mechanosensitive cellular components that transmit the compression to induce calcium influx, which in turn triggers activation of RhoA, Src, FAK, and ERK signaling, as well as MMP-9 expression. Interestingly, for the first time we observed invadopodia with matrix degradation ability on the apical side of the cells, similar to those commonly observed at the cells ventral side. Furthermore, we demonstrate that Piezo1 and caveolae were both involved in mediating the compressive stress-induced cancer cell invasive phenotype as Piezo1 and caveolae were often colocalized, and reduction of Cav-1 expression or disruption of caveolae with methyl-{beta}-cyclodextrin led to not only reduced Piezo1 expression but also attenuation of the invasive phenotypes promoted by compressive stress. Taken together, our data indicate that mechanical compressive stress activates Piezo1 channels to mediate enhanced cancer cell invasion and matrix degradation that may be a critical mechanotransduction pathway during, and potentially a novel therapeutic target for, breast cancer metastasis

cell biology↗

bioRxiv2017

Loss Of PTEN Promotes Formation Of Signaling-Specific Clathrin-Coated Pits

Defective endocytosis and vesicular trafficking of signaling receptors has recently emerged as a multifaceted hallmark of malignant cells. Clathrin-coated pits (CCPs), the fundamental unit of clathrin-mediated endocytosis, display highly heterogeneous dynamics on the plasma membrane where they can take from 20 seconds to over a minute to form cytosolic coated-vesicles. Despite the large number of cargo molecules that traffic through CCPs, it is not well understood whether signaling receptors activated in cancer, such as epidermal growth factor receptor (EGFR), are regulated through a specific subset of CCPs. The signaling lipid phosphatidylinositol (3,4,5)-triphosphate (PI(3,4,5)P3), which is dephosphorylated by phosphatase tensin homolog (PTEN), is a potent tumorigenic signaling lipid that is present in excess in many types of cancers. Using total internal reflection fluorescence microscopy and automated tracking and detection of CCPs, we find PTEN and EGF bound EGFR are enriched in a distinct subset of short-lived CCPs that corresponded with clathrin-dependent EGF-induced signaling. By deleting PTEN using CRISPR-Cas9 and reconstituting PTEN, we demonstrate that PTEN plays a role in the regulation of CCP dynamics; this appears to recapitulate CCP dynamics in highly metastatic PTEN-deleted cancer cells where we find a larger proportion of short-lived CCPs and higher initiation density compared to the normal cells. Furthermore, increased PI(3,4,5)P3 results in higher proportion of short-lived CCPs, an effect that recapitulates PTEN deletion. Our findings provide strong evidence for the existence of short-lived signaling-capable CCPs. Altogether, these findings demonstrate the importance of PTEN and PI(3,4,5)P3 in regulating CCP dynamics and assign a new function to PTEN as a modulator of signaling-capable CCPs.

cell biology↗