Acquisition of anoikis resistance promotes alterations in the Ras/ERK and PI3K/Akt signaling pathways and matrix remodeling in endothelial cells.

Anoikis is a programmed cell death induced upon cell detachment from extracellular matrix. Anoikis resistance is a critical mechanism in tumor metastasis. Cancer cells deregulate and adapt their metabolism to survive in the absence of adhesion, spreading metastases to distant organs. These adaptations include abnormal regulation of growth factor receptors activating prosurvival signaling pathways, such as the Ras/ERK and PI3K/Akt pathways, and extracellular matrix remodeling, leading to metastasis by an increase of invasiveness and inhibiting anoikis. This study investigates the possible involvement of ECM components and signaling pathways in the regulation of resistance to anoikis in endothelial cells (EC). Endothelial cells submitted to stressful conditions by blocking adhesion to substrate (anoikis resistance) display an up-regulation of Ras/ERK and PI3k/Akt pathways by high expression of Ras, ERK, PI3K (p110α) and Akt (Thr 308). After ERK and PI3K inhibiting, all EC-derived cell lines studied showed lower growth, a decrease in invasive potential and a higher rate of apoptosis. Furthermore, anoikis-resistant cell lines display a decrease in the expression of fibronectin, collagen IV and hyaluronic acid and an increase in the expression of laminin, perlecan, αv, ß3, α5 and ß1 integrins subunits, hyaluronidades 1, 2 and 3 and metalloproteinases 2 and 9. These results indicate that the acquisition of anoikis resistance induced remodeling of the extracellular matrix and overexpression of the PI3K/Akt and Ras/ERK pathway components. Acquisition of resistance to anoikis is a potentially crucial step in endothelial cell transformation.

Acquisition of anoikis resistance up-regulates syndecan-4 expression in endothelial cells.

Anoikis is a programmed cell death induced upon cell detachment from extracellular matrix, behaving as a critical mechanism in preventing adherent-independent cell growth and attachment to an inappropriate matrix, thus avoiding colonization of distant organs. Cell adhesion plays an important role in neoplastic transformation. Tumors produce several molecules that facilitate their proliferation, invasion and maintenance, especially proteoglycans. The syndecan-4, a heparan sulfate proteoglycan, can act as a co-receptor of growth factors and proteins of the extracellular matrix by increasing the affinity of adhesion molecules to their specific receptors. It participates together with integrins in cell adhesion at focal contacts connecting the extracellular matrix to the cytoskeleton. Changes in the expression of syndecan-4 have been observed in tumor cells, indicating its involvement in cancer. This study investigates the role of syndecan-4 in the process of anoikis and cell transformation. Endothelial cells were submitted to sequential cycles of forced anchorage impediment and distinct lineages were obtained. Anoikis-resistant endothelial cells display morphological alterations, high rate of proliferation, poor adhesion to fibronectin, laminin and collagen IV and deregulation of the cell cycle, becoming less serum-dependent. Furthermore, anoikis-resistant cell lines display a high invasive potential and a low rate of apoptosis. This is accompanied by an increase in the levels of heparan sulfate and chondroitin sulfate as well as by changes in the expression of syndecan-4 and heparanase. These results indicate that syndecan-4 plays a important role in acquisition of anoikis resistance and that the conferral of anoikis resistance may suffice to transform endothelial cells.

Surface chemistry and spectroscopy studies on 1,4-naphthoquinone in cell membrane models using Langmuir monolayers.

Investigating the role of drugs whose pharmaceutical activity is associated with cell membranes is fundamental to comprehending the biochemical processes that occur on membrane surfaces. In this work, we examined the action of 1,4-naphthoquinone in lipid Langmuir monolayers at the air-water interface, which served as a model for half of a membrane, and investigated the molecular interactions involved with tensiometry and vibrational spectroscopy. The surface pressure-area isotherms exhibited a noticeable shift to a lower area in relation to 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-dihexadecanoyl-sn-glycero-3-phospho-l-serine (DPPS) lipid monolayers, which indicated a disruption of the monolayer structure and solubilisation of the lipids towards the aqueous subphase. To better correlate to the action of this drug in biological membrane events, cell cultures that represented tumorigenic and non-tumorigenic cells were spread onto the air-water interface, and 1,4-naphthoquinone was then incorporated. While only slight changes were observed in the non-tumorigenic cells upon drug incorporation, significant changes were observed in the tumorigenic cells, on which the organisation of the Langmuir monolayers was disrupted as evidenced by tensiometry and vibrational spectroscopy. This work then shows that this drug interacts preferentially for specific surfaces. In simplified models, it has a higher effect for the negative charged DPPS rather than the zwitterionic DPPC; and for complex cell cultures, 1,4-naphthoquinone presents a more significant effect for that representing tumorigenic cells.