Development of the model demonstrated here was supported by DOD grant W81XWH-12-1-0163, NIH grants R21 CA179981 and R21 CA196202, and the Sato Metastasis Research Fund.

1. Cell preparation
<ol>
	<li>Release cells from tissue culture dish when 70-90% confluent by following the recommended guidelines for the cell line in use.
	<ol>
		<li>For example, aspirate the growth medium for PC-3 cells, and wash the 10 cm dish of cells with 5 mL of calcium- and magnesium-free phosphate-buffered saline (PBS).</li>
		<li>Aspirate the PBS before adding 1 mL of 0.25% trypsin using manufacturer&#39;s protocol.</li>
		<li>After observing the detachment of the cells under an inverted microscope, add 5 mL...

<ol>
	<li>Dillek&#229;s, H., Rogers, M. S., Straume, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Are+90%+of+deaths+from+cancer+caused+by+metastases.">Are 90% of deaths from cancer caused by metastases.</a> Cancer medicine. 8 (12), 5574-5576 (2019).</li><li>Hanahan, D., Weinberg, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hallmarks+of+cancer:+the+next+generation.">Hallmarks of cancer: the next generation.</a> Cell. 144 (5), 646-674 (2011).</li><li>Strilic, B., Offermanns, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intravascular+survival+and+extravasation+of+tumor+cells.">Intravascular survival and extravasation of tumor cells.</a> Cancer Cell. 32 (3), 282-293 (2017).</li><li>Labelle, M., Hynes, R. O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+initial+hours+of+metastasis:+the+importance+of+cooperative+host-tumor+cell+interactions+during+hematogenous+dissemination.">The initial hours of metastasis: the importance of cooperative host-tumor cell interactions during hematogenous dissemination.</a> Cancer Discovery. 2 (12), 1091-1099 (2012).</li><li>Krog, B. L., Henry, M. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biomechanics+of+the+circulating+tumor+cell+microenvironment.">Biomechanics of the circulating tumor cell microenvironment.</a> Advances in Experimental Medicine and Biology. 1092, 209-233 (2018).</li><li>Weiss, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Metastatic+inefficiency.">Metastatic inefficiency.</a> Advances in Cancer Research. 54, 159-211 (1990).</li><li>Zeidman, I., Mc, C. M., Coman, D. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Factors+affecting+the+number+of+tumor+metastases;+experiments+with+a+transplantable+mouse+tumor.">Factors affecting the number of tumor metastases; experiments with a transplantable mouse tumor.</a> Cancer Research. 10 (6), 357-359 (1950).</li><li>Fidler, I. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Metastasis:+quantitative+analysis+of+distribution+and+fate+of+tumor+embolilabeled+with+125+I-5-iodo-2'-deoxyuridine.">Metastasis: quantitative analysis of distribution and fate of tumor embolilabeled with 125 I-5-iodo-2'-deoxyuridine.</a> Journal of the National Cancer Institute. 45 (4), 773-782 (1970).</li><li>Cameron, M. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Temporal+progression+of+metastasis+in+lung:+cell+survival,+dormancy,+and+location+dependence+of+metastatic+inefficiency.">Temporal progression of metastasis in lung: cell survival, dormancy, and location dependence of metastatic inefficiency.</a> Cancer Research. 60 (9), 2541-2546 (2000).</li><li>Luzzi, K. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multistep+nature+of+metastatic+inefficiency:+dormancy+of+solitary+cells+after+successful+extravasation+and+limited+survival+of+early+micrometastases.">Multistep nature of metastatic inefficiency: dormancy of solitary cells after successful extravasation and limited survival of early micrometastases.</a> American Journal of Pathology. 153 (3), 865-873 (1998).</li><li>Kienast, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Real-time+imaging+reveals+the+single+steps+of+brain+metastasis+formation.">Real-time imaging reveals the single steps of brain metastasis formation.</a> Nature Medicine. 16 (1), 116-122 (2010).</li><li>Takagi, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+the+circulating+tumor+cell+capture+ability+of+a+slit+filter-based+method+in+comparison+to+a+selection-free+method+in+multiple+cancer+types.">Analysis of the circulating tumor cell capture ability of a slit filter-based method in comparison to a selection-free method in multiple cancer types.</a> International journal of molecular sciences. 21 (23), 9031 (2020).</li><li>Scott, J., Kuhn, P., Anderson, A. 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D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Resistance+to+fluid+shear+stress+is+a+conserved+biophysical+property+of+malignant+cells.">Resistance to fluid shear stress is a conserved biophysical property of malignant cells.</a> PLoS One. 7 (12), 50973 (2012).</li><li>Malek, A. M., Alper, S. L., Izumo, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hemodynamic+shear+stress+and+its+role+in+atherosclerosis.">Hemodynamic shear stress and its role in atherosclerosis.</a> JAMA. 282 (21), 2035-2042 (1999).</li><li>Brass, L. F., Diamond, S. 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N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Turbulent+blood+flow+in+the+ascending+aorta+of+humans+with+normal+and+diseased+aortic+valves.">Turbulent blood flow in the ascending aorta of humans with normal and diseased aortic valves.</a> Circulation Research. 39 (1), 58-65 (1976).</li><li>Strony, J., Beaudoin, A., Brands, D., Adelman, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+shear+stress+and+hemodynamic+factors+in+a+model+of+coronary+artery+stenosis+and+thrombosis.">Analysis of shear stress and hemodynamic factors in a model of coronary artery stenosis and thrombosis.</a> The American Journal of Physiology. 265 (5), 1787-1796 (1993).</li><li>Chalmers, J. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mixing,+aeration+and+cell+damage,+30++years+later:+what+we+learned,+how+it+affected+the+cell+culture+industry+and+what+we+would+like+to+know+more+about.">Mixing, aeration and cell damage, 30+ years later: what we learned, how it affected the cell culture industry and what we would like to know more about.</a> Current Opinion in Chemical Engineering. 10, 94-102 (2015).</li><li>Vennin, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Trsient+tissue+priming+via+ROCK+inhibition+uncouples+pancreatic+cancer+progression,+sensitivity+to+chemotherapy,+and+metastasis.">Trsient tissue priming via ROCK inhibition uncouples pancreatic cancer progression, sensitivity to chemotherapy, and metastasis.</a> Science Translational Medicine. 9 (384), 126 (2017).</li><li>Mitchell, M. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lamin+A/C+deficiency+reduces+circulating+tumor+cell+resistance+to+fluid+shear+stress.">Lamin A/C deficiency reduces circulating tumor cell resistance to fluid shear stress.</a> American Journal of Physiology: Cell Physiology. 309 (11), 736-746 (2015).</li><li>Ortiz-Otero, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cancer+associated+fibroblasts+confer+shear+resistance+to+circulating+tumor+cells+during+prostate+cancer+metastatic+progression.">Cancer associated fibroblasts confer shear resistance to circulating tumor cells during prostate cancer metastatic progression.</a> Oncotarget. 11 (12), 1037-1050 (2020).</li><li>Moose, D. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cancer+cells+resist+mechanical+destruction+in+circulation+via+RhoA/actomyosin-dependent+mechano-adaptation.">Cancer cells resist mechanical destruction in circulation via RhoA/actomyosin-dependent mechano-adaptation.</a> Cell Reports. 30 (11), 3864-3874 (2020).</li><li>Miller, B. E., Miller, F. R., Wilburn, D. J., Heppner, G. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+tumour+cell+composition+in+tumours+composed+of+paired+mixtures+of+mammary+tumour+cell+lines.">Analysis of tumour cell composition in tumours composed of paired mixtures of mammary tumour cell lines.</a> British Journal of Cancer. 56 (5), 561-569 (1987).</li><li>Aslakson, C. J., Miller, F. 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MDH is a co-founder, President and shareholder of SynderBio, Inc. DLM is a consultant for SynderBio, Inc.

This paper demonstrates the application of FSS to cancer cells in suspension using a syringe and needle. Using this model, cancer cells have been shown to be more resistant to brief pulses of high-level FSS relative to non-transformed epithelial cells15,22,24. Furthermore, exposure to FSS using this model results in a rapid increase in cell stiffness, activation of RhoA, and increased cortical F-actin and myosin II-based contrac...

Metastasis, or the spread of cancer beyond the initial tumor site, is a major factor underlying cancer mortality1. During metastasis, cancer cells utilize the circulatory system as a highway to disseminate to distant sites throughout the body2,3. While en route to these sites, circulating tumor cells (CTCs) exist within a dynamic fluid microenvironment unlike that of their original primary tumor3,4,5. It has been proposed that this fluid microenvironment is one of many barriers to metastasis4. There is wide agreement in the concept of metastatic inefficiency, i.e., that most CTCs entering the circulation either perish or do not form productive metastatic colonies6,7,8. However, why metastasis is inefficient from the perspective of an individual CTC is less certain and remains an active area of investigation. CTCs are detached from extracellular matrix, deprived of soluble growth and survival factors that may be present in the primary tumor, and exposed to the immune system and hemodynamic forces in a much different manner than in the primary tumor4. Each of these factors may contribute to the poor survival of CTCs, but their relative contributions are unclear. This paper addresses the question of how hemodynamic forces affect CTCs.
Studying the effects of hemodynamic forces on CTCs is quite challenging. Currently, there are no engineered in vitro systems that can replicate the entire spatiotemporal dynamics (heart to capillaries) and rheological properties of the human vascular system. Moreover, how CTCs experience the circulatory system is not entirely clear. Experimental evidence indicates that most cancer cells do not circulate continuously like blood cells. Rather, due to their relatively large size (10-20 &#181;m in diameter), most CTCs become entrapped in capillary beds (6-8 &#181;m in diameter) for variable lengths of time (s to days) where they may die, extravasate, or be displaced to the next capillary bed8,9,10,11. However, there is some evidence that CTC size may be more heterogeneous in vivo, and that smaller CTCs are detectable12. Therefore, based on distance and blood flow velocity, CTCs may only circulate freely for a matter of seconds between these periods of entrapment, although a quantitative description of this behavior is lacking13.
Furthermore, depending on where CTCs enter the circulation, they may pass through multiple capillary beds in the lung and other peripheral sites and through both the right and left heart prior to reaching their final destination. Along the way, CTCs are exposed to various hemodynamic stresses including fluid shear stress (FSS), compressive forces during their entrapment in the microcirculation, and potentially, traction forces under circumstances where they might exhibit leukocyte-like rolling along blood vessel walls14. Thus, both the ability to model the circulation and the understanding of the CTC behavior to be modeled is limited. Because of this uncertainty, any findings from in vitro model systems should be validated in an experimental vertebrate organism and ultimately, in cancer patients.
With the aforementioned caveats, this paper demonstrates a relatively simple model to apply FSS to cells in suspension to probe the effects of FSS on CTCs first described in 201215. FSS results from friction of blood flow against the vessel wall, which produces a parabolic velocity gradient under conditions of laminar flow in larger vessels. Cells experience higher levels of FSS near vessel walls and lower levels near the center of the blood vessel. Fluid viscosity, flow rate, and dimensions of the conduit through which the flow occurs influence FSS, as described by the Hagen-Poiseuille equation. This applies to blood flows behaving as Newtonian fluids, but does not hold for the microcirculation. Physiological FSS ranges over several orders of magnitude with the lowest levels in the lymphatics (&#60;1 dyn/cm2) and the highest at regions around heart valves and atherosclerotic plaques (&#62;500 dyn/cm2)5. Mean wall shear stress in arteries is 10-70 dyn/cm2 and 1-6 dyn/cm2 in veins16,17.
In the heart, cells may be exposed to turbulent flows around valve leaflets where very high-level, but very short-duration FSS may be experienced18,19. Although the bioprocessing field has long studied the effects of FSS on mammalian cells in suspension, this information may be of limited value for understanding the effects of FSS on CTCs as it generally focuses on much lower levels of FSS applied over a long duration20. As described below, using a syringe and needle, one can apply relatively high (tens to thousands dyn/cm2) FSS for a relatively short (milliseconds) duration to a cell suspension. Since the initial description of this model15, others have employed it to study the effects of FSS on cancer cells21,22,23. Multiple &#34;pulses&#34; of FSS can be applied to cell suspensions in a short period of time to facilitate downstream experimental analyses. For example, this model can be used to measure the ability of cells to resist mechanical destruction by FSS by measuring cell viability as a function of the number of pulses applied. Alternatively, the effects of FSS exposure on the biology of cancer cells can be explored by collecting cells for a variety of downstream analyses. Importantly, part of the cell suspension is reserved as a static control to compare the effects of FSS from those that might be associated with cell detachment and time held in suspension.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>0.25% Trypsin</td>
			<td>Gibco</td>
			<td>25200-056</td>
			<td></td>
		</tr>
		<tr>
			<td>14 mL round bottom tubes</td>
			<td>Falcon - Corning</td>
			<td>352059</td>
			<td></td>
		</tr>
		<tr>
			<td>30 G 1/2&#34; Needle</td>
			<td>BD</td>
			<td>305106</td>
			<td></td>
		</tr>
		<tr>
			<td>5 mL syringe</td>
			<td>BD</td>
			<td>309646</td>
			<td></td>
		</tr>
		<tr>
			<td>96-well black bottom plate</td>
			<td>Costar - Corning</td>
			<td>3915</td>
			<td></td>
		</tr>
		<tr>
			<td>Bioluminescence detector</td>
			<td>AMI</td>
			<td>AMI HTX</td>
			<td></td>
		</tr>
		<tr>
			<td>BSA, Fraction V</td>
			<td>Sigma</td>
			<td>10735086001</td>
			<td></td>
		</tr>
		<tr>
			<td>Cell Titer Blue</td>
			<td>Promega</td>
			<td>G8081</td>
			<td></td>
		</tr>
		<tr>
			<td>crystal violet</td>
			<td>Sigma</td>
			<td>C0775</td>
			<td></td>
		</tr>
		<tr>
			<td>D-luciferin</td>
			<td>GoldBio</td>
			<td>D-LUCK</td>
			<td></td>
		</tr>
		<tr>
			<td>DMEM</td>
			<td>Gibco</td>
			<td>11965-092</td>
			<td></td>
		</tr>
		<tr>
			<td>FBS</td>
			<td>Atlanta Biologicals</td>
			<td>S11150</td>
			<td></td>
		</tr>
		<tr>
			<td>PBS</td>
			<td>Gibco</td>
			<td>10010023</td>
			<td></td>
		</tr>
		<tr>
			<td>Plate Reader</td>
			<td>BioTek</td>
			<td>Synergy HT</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium Azide (NaN3)</td>
			<td>Sigma</td>
			<td>S2002</td>
			<td></td>
		</tr>
		<tr>
			<td>Syringe Pump</td>
			<td>Harvard Apparatus</td>
			<td>70-3005</td>
			<td></td>
		</tr>
	</tbody>
</table>

modeling the effects of hemodynamic stress on circulating tumor cells using a syringe and needle

During metastasis, cancer cells from solid tissues, including epithelia, gain access to the lymphatic and hematogenous circulation where they are exposed to mechanical stress due to hemodynamic flow. One of these stresses that circulating tumor cells (CTCs) experience is fluid shear stress (FSS). While cancer cells may experience low levels of FSS within the tumor due to interstitial flow, CTCs are exposed, without extracellular matrix attachment, to much greater levels of FSS. Physiologically, FSS ranges over 3-4 orders of magnitude, with low levels present in lymphatics (&#60;1 dyne/cm2) and the highest levels present briefly as cells pass through the heart and around heart valves (&#62;500 dynes/cm2). There are a few in vitro models designed to model different ranges of physiological shear stress over various time frames. This paper describes a model to investigate the consequences of brief (millisecond) pulses of high-level FSS on cancer cell biology using a simple syringe and needle system.

Elevated resistance to FSS-induced mechanical destruction has been previously shown to be a conserved phenotype across multiple cancer cell lines and cancer cells freshly isolated from tumors relative to non-transformed epithelial cell comparators15,24. Here, additional cancer cell lines from a variety of tissue origins (Table 2) were tested to demonstrate that the majority of these cells display viability &#8805; 20% after 10 pulses of FSS at 25...

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Modeling the Effects of Hemodynamic Stress on Circulating Tumor Cells using a Syringe and Needle

Here we demonstrate a method to apply fluid shear stress to cancer cells in suspension to model the effects of hemodynamic stress on circulating tumor cells.

During metastasis, cancer cells from solid tissues, including epithelia, gain access to the lymphatic and hematogenous circulation where they are exposed ...

This protocol exposes cancer cells in a suspension to brief pulses of fluid shear stress to mimic certain aspects of how metastatic cancer cells are exposed to hemodynamic forces while they're in the circulatory system. It is a relatively simple technique to apply brief pulses of high level fluid shear stress. When attempting this protocol, be careful on uncapped needles and do not bend them as this will change applied force shear stress.This procedure may produce aerosols, so use appropriate safety measures. To begin, release 70 to 90%confluent PC3 cells from the tissue culture dish by aspirating the growth medium and washing the 10 centimeter dish with five milliliters of calcium and magnesium-free PBS. Then, aspirate the PBS and add one milliliter of 0.25%trypsin.Post-trypsinization, observe the detachment of the cells under an inverted microscope. To inhibit the trypsin, add five milliliters of DMEM/F12 medium containing 10%FBS. Next, place the cell suspension into a conical tube and determine the cell concentration and total cell number.Centrifuge the cell suspension at 300 x g for three minutes, then aspirate the supernatant and resuspend the pellet in a serum-free tissue culture medium. Cut around bottom of 14 milliliter polystyrene tube at the seven milliliter line and place the mixed cell suspension into the cut tube. Separately collect static control samples of cells before fluid shear stress exposure to use for performing assays.To expose the remaining cell suspension sample to fluid shear stress, draw the cell suspension into a five milliliter syringe and attach a 30 gauge half inch needle. Place and secure the syringe with an uncapped needle onto a syringe pump and set the flow rate to achieve the desired level of fluid shear stress. Run the syringe pump and collect the sheared sample in the cut tube at an approximately 45 degree angle to reduce foaming.Carefully remove the syringe from the syringe pump and use pliers to remove the needle, taking care not to touch it. Repeat the procedure until the cell suspension has been exposed to the desired number of pulses of fluid shear stress. Perform viability assays with the static samples before exposing the cells to fluid shear stress.For enzymatic assays, transfer 100 microliter aliquots from the static samples in duplicate into a 96-well plate. Then, collect 100 microliters of samples after fluid shear stress exposure and place them in a 96-well plate. Add 20 microliters of a 0.15 milligram per milliliter resazurin solution to each sample well and to wells containing 100 microliters of medium alone.Incubate the well plates in the 37 degrees Celsius tissue culture incubator for two hours, then measure the fluorescence and absorbance using a plate reader and obtain the percentage of viable cells by comparing the average signal from each of the fluid shear stress exposed samples to the average to static control sample. Similarly, collect aliquots from static samples to perform flow cytometry and clonogenic assays as described in the text manuscript. In the representative analysis, the viability of syngeneic biopsy mammary epithelial cancer cells was assessed using resazurin conversion after exposing cells to a number of fluid shear stress pulses.Even though each cell line displayed different resistance profiles, there was no significant difference in viability after 10 pulses of fluid shear stress exposure. Additional cancer cell lines from a variety of tissue origins demonstrated the viability of more than 20%after 10 pulses of fluid shear stress, except for MIA PaCa-2 cells, which showed a viability of less than 10%due to sensitivity towards mechanical destruction from fluid shear stress. When collecting the static sample prior to applying fluids shear stress, ensure that the cell suspension is a homogeneously mixed.Carefully remove the needle with pliers and do not bend or touch the needle. In addition to measuring cell viability, one can evaluate changes in gene expression, cell signaling, proliferation, and migration. Using this as a model of exposure to fluid shear stress, one can study both how cancer cells resist destruction by fluid shear stress and evaluate the effects of fluid shear stress on the biology of cancer cells.This technique has been used by our laboratory and others to explore the effects of fluid shear stress on circulating tumor cells. These studies have shown that fluid shear stress rapidly alters the mechanical properties of cancer cells and that this contributes to the ability of cancer cells to resist destruction by fluid shear stress.

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Cancer Research

2.4K ビュー.  University of Iowa. このプロトコルは、流体せん断ストレスの短いパルスに懸濁中の癌細胞を公開し、循環系にいる間に転移性癌細胞が血行力にさらされる方法の特定の側面を模倣する。これは、高レベル流体せん断応力の短いパルスを適用する比較的簡単な技術です。このプロトコルを試みるとき、制限されていない針に注意し、これは適用された力せん断応力を変更するので、それら?...