Amoeboid chemotaxis: future challenges and opportunities

The Effect of Local Anesthetics on Neutrophils in the Context of Different Isolation Techniques

Various functions of polymorphonuclear neutrophils (PMNs) are related to diseases and postoperative plasma changes. The influence of some local anesthetics (LAs) on PMNs obtained by conventional isolation methods and their functions has already been demonstrated. This study investigates the effect of selected LAs on PMNs, comparing a new isolation method with conventional ones. To obtain the PMNs, we performed either gelafundin sedimentation, hypotonic lysis or density gradient centrifugation. Subsequently, PMNs were mixed with different concentrations of bupivacaine, levobupivacaine, lidocaine or ropivacaine. Live cell imaging and flow cytometry were performed to quantify the migration, ROS production, NETosis and antigen expression of PMNs. We found the inhibition of chemotaxis and ROS production by LAs. PMNs showed a strong reduction in time to half maximal NETosis in response to bupivacaine and lidocaine, but not to levobupivacaine and ropivacaine. We also found distinct differences in survival time and migration duration between the isolation methods. This suggests that the careful selection of LAs has a short-term impact on in vitro PMNs.

Microfluidics-based devices: New tools for studying cancer and cancer stem cell migration

Cell movement is highly sensitive to stimuli from the extracellular matrix and media. Receptors on the plasma membrane in cells can activate signal transduction pathways that change the mechanical behavior of a cell by reorganizing motion-related organelles. Cancer cells change their migration mechanisms in response to different environments more robustly than noncancer cells. Therefore, therapeutic approaches to immobilize cancer cells via inhibition of the related signal transduction pathways rely on a better understanding of cell migration mechanisms. In recent years, engineers have been working with biologists to apply microfluidics technology to study cell migration. As opposed to conventional cultures on dishes, microfluidics deals with the manipulation of fluids that are geometrically constrained to a submillimeter scale. Such small scales offer a number of advantages including cost effectiveness, low consumption of reagents, high sensitivity, high spatiotemporal resolution, and laminar flow. Therefore, microfluidics has a potential as a new platform to study cell migration. In this review, we summarized recent progress on the application of microfluidics in cancer and other cell migration researches. These studies have enhanced our understanding of cell migration and cancer invasion as well as their responses to subtle variations in their microenvironment. We hope that this review will serve as an interdisciplinary guidance for both biologists and engineers as they further develop the microfluidic toolbox toward applications in cancer research.

Chemotaxis: insights from the extending pseudopod

Chemotaxis is one of the most fascinating processes in cell biology. Shallow gradients of chemoattractant direct the movement of cells, and an intricate network of signalling pathways somehow instructs the movement apparatus to induce pseudopods in the direction of these gradients. Exciting new experiments have approached chemotaxis from the perspective of the extending pseudopod. These recent studies have revealed that, in the absence of external cues, cells use endogenous signals for the highly ordered extension of pseudopods, which appear mainly as alternating right and left splits. In addition, chemoattractants activate other signalling molecules that induce a positional bias of this basal system, such that the extending pseudopods are oriented towards the gradient. In this Commentary, I review the findings of these recent experiments, which together provide a new view of cell movement and chemotaxis.

Cross-talk between MAP kinase pathways is involved in IGF-independent, IGFBP-6-induced Rh30 rhabdomyosarcoma cell migration

Insulin-like growth factor binding protein-6 (IGFBP-6) inhibits the tumorigenic properties of IGF-II-dependent cancer cells by directly inhibiting IGF-II actions. However, in some cases, IGFBP-6 is associated with increased cancer cell tumorigenicity, which is unlikely to be due to IGF-II inhibition. The mechanisms underlying the contradictory actions of IGFBP-6 remain unclear. We recently generated an IGFBP-6 mutant that does not bind IGFs (mIGFBP-6) to address this issue. Although RD rhabdomyosarcoma cells express IGF-II, we previously showed that mIGFBP-6 promoted migration through an IGF-independent, p38-dependent pathway. We further studied the role of MAP kinases in IGFBP-6-induced migration of Rh30 rhabdomyosarcoma cells, which also express IGF-II. In these cells, mIGFBP-6 induced chemotaxis rather than chemokinesis. Both wild-type (wt) and mIGFBP-6 transiently induced phosphorylation of ERK1/2 and JNK1, but not p38. Inhibition of ERK1/2 phosphorylation completely prevented mIGFBP-6-induced ERK1/2 activation and cell migration, whereas a JNK inhibitor partially prevented migration. Interestingly, p38 pathway inhibition completely prevented mIGFBP-6-induced ERK1/2 and JNK1 activation and migration despite mIGFBP-6 not activating p38. Furthermore, blocking the ERK1/2 pathway also inhibited mIGFBP-6-induced JNK1 activation. In contrast, IGFBP-6 had no effect on Akt phosphorylation and an Akt inhibitor had no effect on migration. These results indicate that IGFBP-6 promotes Rh30 rhabdomyosarcoma chemotaxis in an IGF-independent manner, and that MAPK signaling pathways and their cross-talk play an important role in this process. Therefore, besides decreasing Rh30 cell proliferation by inhibiting IGF-II, IGFBP-6 promotes their migration via a distinct pathway. Understanding these disparate actions of IGFBP-6 may lead to the development of novel cancer therapeutics.

In vivo assay for tumor cell invasion

We describe an in vivo invasion assay that enables the collection of invasive cells from the primary tumor. In addition to determination of the endogenous, unstimulated invasive properties of cells in vivo, the assay can take advantage of the chemotactic properties of cancer cells. Microneedles are filled with a mixture of extracellular matrix components such as Matrigel with or without a chemoattractant such as EGF, and then introduced into the primary tumor of a rat or mouse that is generated either by orthotopic injection of carcinoma cell lines or by a transgene such as polyoma Middle T. Over the course of 4 h the invasive cell population enters the needles while the animal is kept under anesthesia. At the end of the collection time, the invasive cells are extruded from the microneedles and can be analyzed in terms of the number and type of cells that invade in response to defined stimuli. By including pharmacological inhibitors in the needle, signaling pathways contributing to in vivo invasion can also be identified. This assay leads to a better understanding of the cell types and signaling involved in the tumor microenvironment, and has the potential to be applied to a variety of in vivo models.