Ovarian Cancer Spheroids Use Myosin-Generated Force to Clear the Mesothelium

Department of Cell Biology, Harvard Medical School, Boston, 02115 MA, USA.
Cancer Discovery (Impact Factor: 19.45). 07/2011; 1(2):144-57. DOI: 10.1158/2159-8274.CD-11-0010
Source: PubMed


Dissemination of ovarian tumors involves the implantation of cancer spheroids into the mesothelial monolayer on the walls of peritoneal and pleural cavity organs. Biopsies of tumors attached to peritoneal organs show that mesothelial cells are not present under tumor masses. We have developed a live, image-based in vitro model in which interactions between tumor spheroids and mesothelial cells can be monitored in real time to provide spatial and temporal understanding of mesothelial clearance. Here we provide evidence that ovarian cancer spheroids utilize integrin- and talin- dependent activation of myosin and traction force to promote mesothelial cells displacement from underneath a tumor cell spheroid. These results suggest that ovarian tumor cell clusters gain access to the sub-mesothelial environment by exerting force on the mesothelial cells lining target organs, driving migration and clearance of the mesothelial cells.

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Available from: Taru Muranen, Oct 04, 2015
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    • "Intriguingly, the histopathological examination of the excised tumors (Fig. 4) revealed that in the case of xenografts generated upon injection of A2780, OVCAR- 3, and SKOV-3 cells, peritoneal mesothelial cells (identified according to the presence of the Wt1 antigen) were still present under the tumor mass, questioning to some extent the paradigm by Iwanicki et al. about the lack of mesothelium under cancerous tissue [3]. The presence of mesothelial cells, staying in agreement with the results of Steinkamp et al. [23], may imply that their involvement in peritoneal ovarian cancer metastasis not only encompasses the very early steps of cancer cell dissemination (until their " clearance " [3] [15]), but may also last continuously, probably amplifying their harmful Fig. 4. Microscopic evaluation of tumors excised from the mouse peritoneal cavity after i.p. injection of ovarian cancer cells. Results of the tumor examination using h+e staining (left panel). "
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    ABSTRACT: The role of mesothelial cells in the intraperitoneal spread of ovarian cancer is still elusive. In particular, it is unclear whether these cells constitute a passive barrier preventing cancer cell progression or perhaps act as an active promoter of this process. In this report we show that omental human peritoneal mesothelial cells (HPMCs) stimulate adhesion and proliferation of ovarian cancer cells (A2780, OVCAR-3, SKOV-3). The latter was associated with the paracrine activity of GRO-1, IL-6, and IL-8 released to the environment by HPMCs. Furthermore, the growth dynamics of ovarian cancer xenografts produced in response to i.p. injection of ovarian cancer cells together with HPMCs was remarkably greater than for implantation of cancer cells alone. A layer of peritoneal mesothelium was consistently present in close proximity to the tumor mass in every xenograft model. In conclusion, our results indicate that HPMCs play a supporting role in the intraperitoneal invasiveness of ovarian malignancy, whose effect may be attributed to their ability to stimulate adhesion and proliferation of cancer cells.
    Cancer Letters 10/2014; 355(2). DOI:10.1016/j.canlet.2014.09.041 · 5.62 Impact Factor
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    • "There are three proposed methods of cancer cell migration through the endothelium: (a) cancer cells may migrate through the EC body [10], (b) cancer cells may induce EC apoptosis [10], [13] and (c) cancer cells may migrate through endothelial cell-cell junctions without permanently destroying the EC layer [11]. In recent years, research has also shown that cancer cells also exert forces on ECs that push them deeper into the extracellular matrix during transmigration [15], [16], and that the endothelium enhances cancer cell migration [17]. These findings suggest that cancer migration through the endothelium is a complex process that requires further investigation to elucidate its mechanistic course. "
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    ABSTRACT: Metastasis is accountable for 90% of cancer deaths. During metastasis, tumor cells break away from the primary tumor, enter the blood and the lymph vessels, and use them as highways to travel to distant sites in the body to form secondary tumors. Cancer cell migration through the endothelium and into the basement membrane represents a critical step in the metastatic cascade, yet it is not well understood. This process is well characterized for immune cells that routinely transmigrate through the endothelium to sites of infection, inflammation, or injury. Previous studies with leukocytes have demonstrated that this step depends heavily on the activation status of the endothelium and subendothelial substrate stiffness. Here, we used a previously established in vitro model of the endothelium and live cell imaging, in order to observe cancer cell transmigration and compare this process to leukocytes. Interestingly, cancer cell transmigration includes an additional step, which we term 'incorporation', into the endothelial cell (EC) monolayer. During this phase, cancer cells physically displace ECs, leading to the dislocation of EC VE-cadherin away from EC junctions bordering cancer cells, and spread into the monolayer. In some cases, ECs completely detach from the matrix. Furthermore, cancer cell incorporation occurs independently of the activation status and the subendothelial substrate stiffness for breast cancer and melanoma cells, a notable difference from the process by which leukocytes transmigrate. Meanwhile, pancreatic cancer cell incorporation was dependent on the activation status of the endothelium and changed on very stiff subendothelial substrates. Collectively, our results provide mechanistic insights into tumor cell extravasation and demonstrate that incorporation is one of the earliest steps.
    PLoS ONE 10/2014; 9(10):e109748. DOI:10.1371/journal.pone.0109748 · 3.23 Impact Factor
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    • "The altered expression of myosins in a number of cancers [93]–[96] has been correlated with higher motility and metastasis. One myosin, myosin-9 (MYH9), stood out as having very high expression in all the BC cells tested, except for MCF-7 cells, which interestingly expressed a low level of this protein (Table 8). "
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    ABSTRACT: The use of broad spectrum chemotherapeutic agents to treat breast cancer results in substantial and debilitating side effects, necessitating the development of targeted therapies to limit tumor proliferation and prevent metastasis. In recent years, the list of approved targeted therapies has expanded, and it includes both monoclonal antibodies and small molecule inhibitors that interfere with key proteins involved in the uncontrolled growth and migration of cancer cells. The targeting of plasma membrane proteins has been most successful to date, and this is reflected in the large representation of these proteins as targets of newer therapies. In view of these facts, experiments were designed to investigate the plasma membrane proteome of a variety of human breast cancer cell lines representing hormone-responsive, ErbB2 over-expressing and triple negative cell types, as well as a benign control. Plasma membranes were isolated by using an aqueous two-phase system, and the resulting proteins were subjected to mass spectrometry analysis. Overall, each of the cell lines expressed some unique proteins, and a number of proteins were expressed in multiple cell lines, but in patterns that did not always follow traditional clinical definitions of breast cancer type. From our data, it can be deduced that most cancer cells possess multiple strategies to promote uncontrolled growth, reflected in aberrant expression of tyrosine kinases, cellular adhesion molecules, and structural proteins. Our data set provides a very rich and complex picture of plasma membrane proteins present on breast cancer cells, and the sorting and categorizing of this data provides interesting insights into the biology, classification, and potential treatment of this prevalent and debilitating disease.
    PLoS ONE 07/2014; 9(7):e102341. DOI:10.1371/journal.pone.0102341 · 3.23 Impact Factor
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