Myosin-independent stiffness sensing by fibroblasts is regulated by the viscoelasticity of flowing actin.

The stiffness of the extracellular matrix induces differential tension within integrin-based adhesions, triggering differential mechanoresponses. However, it has been unclear if the stiffness-dependent differential tension is induced solely by myosin activity. Here, we report that in the absence of myosin contractility, 3T3 fibroblasts still transmit stiffness-dependent differential levels of traction. This myosin-independent differential traction is regulated by polymerizing actin assisted by actin nucleators Arp2/3 and formin where formin has a stronger contribution than Arp2/3 to both traction and actin flow. Intriguingly, despite only slight changes in F-actin flow speed observed in cells with the combined inhibition of Arp2/3 and myosin compared to cells with sole myosin inhibition, they show a 4-times reduction in traction than cells with myosin-only inhibition. Our analyses indicate that traditional models based on rigid F-actin are inadequate for capturing such dramatic force reduction with similar actin flow. Instead, incorporating the F-actin network's viscoelastic properties is crucial. Our new model including the F-actin viscoelasticity reveals that Arp2/3 and formin enhance stiffness sensitivity by mechanically reinforcing the F-actin network, thereby facilitating more effective transmission of flow-induced forces. This model is validated by cell stiffness measurement with atomic force microscopy and experimental observation of model-predicted stiffness-dependent actin flow fluctuation.

Clinical Implications of Exosomes: Targeted Drug Delivery for Cancer Treatment.

Exosomes are nanoscale vesicles generated by cells for intercellular communication. Due to their composition, significant research has been conducted to transform these particles into specific delivery systems for various disease states. In this review, we discuss the common isolation and loading methods of exosomes, some of the major roles of exosomes in the tumor microenvironment, as well as discuss recent applications of exosomes as drug delivery vessels and the resulting clinical implications.

Biophysical changes caused by altered MUC13 expression in pancreatic cancer cells.

BACKGROUND: Pancreatic cancer is one of the most lethal cancers in the United States. This is partly due to the difficulty in early detection of this disease as well as poor therapeutic responses to currently available regimens. Our previous reports suggest that mucin 13 (MUC13, a transmembrane mucin common to gastrointestinal cells) is aberrantly expressed in this disease state, and has been implicated with a worsened prognosis and an enhanced metastatic potential in PanCa. However, virtually no information currently exists to describe the biophysical ramifications of this protein. METHODS: To demonstrate the biophysical effect of MUC13 in PanCa, we generated overexpressing and knockdown model cell lines for PanCa and subsequently subjected them to various biophysical experiments using atomic force microscopy (AFM) and cellular aggregation studies. RESULTS: AFM-based nanoindentation data showed significant biophysical effects with MUC13 modulation in PanCa cells. The overexpression of MUC13 in Panc-1 cells led to an expected decrease in modulus, and a corresponding decrease in adhesion. With MUC13 knockdown, HPAF-II cells exhibited an increased modulus and adhesion. These results were confirmed with altered cell-cell adhesion as seen with aggregation assays. CONCLUSIONS: MUC13 led to significant biophysical changes in PanCa cells and which exhibited characteristic phenotypic changes in cells demonstrated in previous work from our lab. This work gives insight into the use of biophysical measurements that could be used to help diagnose or monitor cancers as well as determine the effects of genetic alterations at a mechanical level.

Next-generation paclitaxel-nanoparticle formulation for pancreatic cancer treatment.

Pancreatic cancer (PanCa) is a major cause of cancer-related death due to limited therapeutic options. As pancreatic tumors are highly desmoplastic, they prevent appropriate uptake of therapeutic payloads. Thus, our objective is to develop a next-generation nanoparticle system for treating PanCa. We generated a multi-layered Pluronic F127 and polyvinyl alcohol stabilized and poly-L-lysine coated paclitaxel loaded poly(lactic-co-glycolic acid) nanoparticle formulation (PPNPs). This formulation exhibited optimal size (~160 nm) and negative Zeta potential (-6.02 mV), efficient lipid raft mediated internalization, pronounced inhibition in growth and metastasis in vitro, and in chemo-naïve and chemo-exposed orthotopic xenograft mouse models. Additionally, PPNPs altered nanomechanical properties of PanCa cells as suggested by the increased elastic modulus in nanoindentation analyses. Immunohistochemistry of orthotopic tumors demonstrated decreased expression of tumorigenic and metastasis associated proteins (ki67, vimentin and slug) in PPNPs treated mice. These results suggest that PPNPs represent a viable and robust platform for (PanCa).

Dietary fatty acids fine-tune Piezo1 mechanical response.

Mechanosensitive ion channels rely on membrane composition to transduce physical stimuli into electrical signals. The Piezo1 channel mediates mechanoelectrical transduction and regulates crucial physiological processes, including vascular architecture and remodeling, cell migration, and erythrocyte volume. The identity of the membrane components that modulate Piezo1 function remain largely unknown. Using lipid profiling analyses, we here identify dietary fatty acids that tune Piezo1 mechanical response. We find that margaric acid, a saturated fatty acid present in dairy products and fish, inhibits Piezo1 activation and polyunsaturated fatty acids (PUFAs), present in fish oils, modulate channel inactivation. Force measurements reveal that margaric acid increases membrane bending stiffness, whereas PUFAs decrease it. We use fatty acid supplementation to abrogate the phenotype of gain-of-function Piezo1 mutations causing human dehydrated hereditary stomatocytosis. Beyond Piezo1, our findings demonstrate that cell-intrinsic lipid profile and changes in the fatty acid metabolism can dictate the cell's response to mechanical cues.

Ormeloxifene Suppresses Prostate Tumor Growth and Metastatic Phenotypes via Inhibition of Oncogenic ß-catenin Signaling and EMT Progression.

Ormeloxifene is a clinically approved selective estrogen receptor modulator, which has also shown excellent anticancer activity, thus it can be an ideal repurposing pharmacophore. Herein, we report therapeutic effects of ormeloxifene on prostate cancer and elucidate a novel molecular mechanism of its anticancer activity. Ormeloxifene treatment inhibited epithelial-to-mesenchymal transition (EMT) process as evident by repression of N-cadherin, Slug, Snail, vimentin, MMPs (MMP2 and MMP3), ß-catenin/TCF-4 transcriptional activity, and induced the expression of pGSK3ß. In molecular docking analysis, ormeloxifene showed proficient docking with ß-catenin and GSK3ß. In addition, ormeloxifene induced apoptosis, inhibited growth and metastatic potential of prostate cancer cells and arrested cell cycle in G0-G1 phase via modulation of cell-cycle regulatory proteins (inhibition of Mcl-1, cyclin D1, and CDK4 and induction of p21 and p27). In functional assays, ormeloxifene remarkably reduced tumorigenic, migratory, and invasive potential of prostate cancer cells. In addition, ormeloxifene treatment significantly (P < 0.01) regressed the prostate tumor growth in the xenograft mouse model while administered through intraperitoneal route (250 µg/mouse, three times a week). These molecular effects of ormeloxifene were also observed in excised tumor tissues as shown by immunohistochemistry analysis. Our results, for the first time, demonstrate repurposing potential of ormeloxifene as an anticancer drug for the treatment of advanced stage metastatic prostate cancer through a novel molecular mechanism involving ß-catenin and EMT pathway. Mol Cancer Ther; 16(10); 2267-80. ©2017 AACR.