This project investigates effects of flow and CXC chemokine ligand-12, CXCL12 stimuli on prostate cancer PC3 cell adhesion and migration by using microfluidics. Prostate carcinoma (PCa) is the most frequently diagnosed cancer in men and the second leading cause of cancer death in American males. Bone metastasis, known to be exacerbated by CXC chemokine receptor 4 (CXCR4) signaling pathways, is a major cause of high morbidity and mortality rates. Although inhibition of CXCR4 is known to modulate cancer metastasis in vivo, the detailed mechanisms are still ambiguous. In vitro studies are useful but lack many physiological features and may not reveal the full range of cancer cell behaviors. For example, the temporal patterns of CXCR4 stimulation by CXCL12 in vivo may be pulsatile rather than continuous as is the case in many in vitro studies. The pulsatile exposure to CXCL12 is expected due to pulsatile release, active degradation by proteases, scavenging by CXCR7 expressing cells, binding to extracellular matrix, and by presence of interstitial flows. Active scavenging by CXCR7 has been shown to be critical for cell directed sensing and polarizing toward CXCL12 stimuli in vivo further reinforcing the potentially important role of temporal patterns of stimulation. Pulsatile stimulation makes mechanistic sense also since CXCR4 is a G-protein coupled receptor (GPCR) and continuous stimulation would simply lead to receptor desensitization. Experiments by microfluidics demonstrate that pulses of CXCL12 rather than continuous stimulation induce significantly enhanced directed migration of PC3 cells. And as expected, CXCR4 knockdown PC3 cells migrated with significantly lower speed and directionality under CXCL12 stimulation compared with normal PC3 cells. During the course of studying the effect of temporal patterns of CXCL12 stimulation it was unexpectedly discovered that PC3 cells showed significantly better adhesion and migration behavior under pulsatile flow than under steady flow even in the absence of chemical stimulation. The technology helps clarify some of the biophysical effect of CXCR4 that may be important for physiological function of malignant prostate cancer cells
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