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Pleiotropic modes of action in tumor cells of RNASET2, an evolutionary highly conserved extracellular RNase.

Lualdi M, Pedrini E, Rea K, Monti L, Scaldaferri D, Gariboldi M, Camporeale A, Ghia P, Monti E, Tomassetti A, Acquati F, Taramelli R - Oncotarget (2015)

Bottom Line: Indeed, RNASET2 expression levels were consistently found to increase following stress induction.Of note, a remarkable rearrangement of the actin cytoskeleton organization, together with changes in cell adhesion and motility, emerged as putative mechanisms by which such cell-autonomous role could occur.Altogether, these biological features allow to put forward the hypothesis that the RNASET2 protein can act as a molecular barrier for limiting the damages and tissue remodeling events occurring during the earlier step of cell transformation.

View Article: PubMed Central - PubMed

Affiliation: Department of Theoretical and Applied Sciences, Università degli Studi dell'Insubria, Varese, Italy.

ABSTRACT
As widely recognized, tumor growth entails a close and complex cross-talk among cancer cells and the surrounding tumor microenvironment. We recently described the human RNASET2 gene as one key player of such microenvironmental cross-talk. Indeed, the protein encoded by this gene is an extracellular RNase which is able to control cancer growth in a non-cell autonomous mode by inducing a sustained recruitment of immune-competent cells belonging to the monocyte/macrophage lineage within a growing tumor mass. Here, we asked whether this oncosuppressor gene is sensitive to stress challenges and whether it can trigger cell-intrinsic processes as well. Indeed, RNASET2 expression levels were consistently found to increase following stress induction. Moreover, changes in RNASET2 expression levels turned out to affect several cancer-related parameters in vitro in an ovarian cancer cell line model. Of note, a remarkable rearrangement of the actin cytoskeleton organization, together with changes in cell adhesion and motility, emerged as putative mechanisms by which such cell-autonomous role could occur. Altogether, these biological features allow to put forward the hypothesis that the RNASET2 protein can act as a molecular barrier for limiting the damages and tissue remodeling events occurring during the earlier step of cell transformation.

No MeSH data available.


Related in: MedlinePlus

RNASET2 protein affects the structural organization of the actin cytoskeleton and is readily internalized by OVCAR3 cellsA) OVCAR3 cell clones were seeded on coverslips and stained with TRITC-conjugated Phalloidin. A complex network of actin filaments is evident in control OVCAR3 cells, while the actin cytoskeleton appears disrupted in RNASET2-silenced cells. After addition of recombinant RNASET2, RNASET2-silenced OVCAR3 cells restored the original cytoskeletal pattern. Scale bar: 10 μm. B, C) RNASET2-silenced OVCAR3 cells were seeded on coverslips, treated with recombinant RNASET2 protein and then processed for IIF. B) In unpermeabilized cells, RNASET2 localizes to the cell surface, while after cell permeabilization a cytoplasmic signal was detected, consistent with the internalization of the protein (white arrowheads). C) Co-staining RNASET2 protein with phalloidin-TRITC showed no evident colocalization signal between the F-actin and the internalized protein. Confocal microscopy images. Scale bar: 10 μm.
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Figure 5: RNASET2 protein affects the structural organization of the actin cytoskeleton and is readily internalized by OVCAR3 cellsA) OVCAR3 cell clones were seeded on coverslips and stained with TRITC-conjugated Phalloidin. A complex network of actin filaments is evident in control OVCAR3 cells, while the actin cytoskeleton appears disrupted in RNASET2-silenced cells. After addition of recombinant RNASET2, RNASET2-silenced OVCAR3 cells restored the original cytoskeletal pattern. Scale bar: 10 μm. B, C) RNASET2-silenced OVCAR3 cells were seeded on coverslips, treated with recombinant RNASET2 protein and then processed for IIF. B) In unpermeabilized cells, RNASET2 localizes to the cell surface, while after cell permeabilization a cytoplasmic signal was detected, consistent with the internalization of the protein (white arrowheads). C) Co-staining RNASET2 protein with phalloidin-TRITC showed no evident colocalization signal between the F-actin and the internalized protein. Confocal microscopy images. Scale bar: 10 μm.

Mentions: We thus investigated the cytoskeletal organization of phalloidin/TRITC-stained control OVCAR3 cells. As shown in Figure 5A, the pattern of actin staining was indicative of a complex network of actin filaments and stress fibers, with several long actin-filament bundles crossing the cell length. Strikingly, such pattern was significantly disrupted in RNASET2-silenced OVCAR3 cells, which showed a predominant pattern of peripheral actin filament bundles, indicating a significant rearrangement of actin stress fibers in the absence of RNASET2 (Figure 5A). Since endogenously expressed RNASET2 is effectively secreted by OVCAR3 cells, we wondered whether the observed re-organization of the cytoskeleton could be affected by a trans-acting mechanism mediated by extracellular RNASET2. Indeed, treatment of RNASET2-silenced OVCAR3 cells with recombinant RNASET2 readily restored the original cytoskeleton pattern detected in control cells (Figure 5A). By contrast, microtubule organization was not affected by RNASET2 silencing (Supplementary Figure 4), indicating a specific role for RNASET2 in the actin cytoskeleton.


Pleiotropic modes of action in tumor cells of RNASET2, an evolutionary highly conserved extracellular RNase.

Lualdi M, Pedrini E, Rea K, Monti L, Scaldaferri D, Gariboldi M, Camporeale A, Ghia P, Monti E, Tomassetti A, Acquati F, Taramelli R - Oncotarget (2015)

RNASET2 protein affects the structural organization of the actin cytoskeleton and is readily internalized by OVCAR3 cellsA) OVCAR3 cell clones were seeded on coverslips and stained with TRITC-conjugated Phalloidin. A complex network of actin filaments is evident in control OVCAR3 cells, while the actin cytoskeleton appears disrupted in RNASET2-silenced cells. After addition of recombinant RNASET2, RNASET2-silenced OVCAR3 cells restored the original cytoskeletal pattern. Scale bar: 10 μm. B, C) RNASET2-silenced OVCAR3 cells were seeded on coverslips, treated with recombinant RNASET2 protein and then processed for IIF. B) In unpermeabilized cells, RNASET2 localizes to the cell surface, while after cell permeabilization a cytoplasmic signal was detected, consistent with the internalization of the protein (white arrowheads). C) Co-staining RNASET2 protein with phalloidin-TRITC showed no evident colocalization signal between the F-actin and the internalized protein. Confocal microscopy images. Scale bar: 10 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4480721&req=5

Figure 5: RNASET2 protein affects the structural organization of the actin cytoskeleton and is readily internalized by OVCAR3 cellsA) OVCAR3 cell clones were seeded on coverslips and stained with TRITC-conjugated Phalloidin. A complex network of actin filaments is evident in control OVCAR3 cells, while the actin cytoskeleton appears disrupted in RNASET2-silenced cells. After addition of recombinant RNASET2, RNASET2-silenced OVCAR3 cells restored the original cytoskeletal pattern. Scale bar: 10 μm. B, C) RNASET2-silenced OVCAR3 cells were seeded on coverslips, treated with recombinant RNASET2 protein and then processed for IIF. B) In unpermeabilized cells, RNASET2 localizes to the cell surface, while after cell permeabilization a cytoplasmic signal was detected, consistent with the internalization of the protein (white arrowheads). C) Co-staining RNASET2 protein with phalloidin-TRITC showed no evident colocalization signal between the F-actin and the internalized protein. Confocal microscopy images. Scale bar: 10 μm.
Mentions: We thus investigated the cytoskeletal organization of phalloidin/TRITC-stained control OVCAR3 cells. As shown in Figure 5A, the pattern of actin staining was indicative of a complex network of actin filaments and stress fibers, with several long actin-filament bundles crossing the cell length. Strikingly, such pattern was significantly disrupted in RNASET2-silenced OVCAR3 cells, which showed a predominant pattern of peripheral actin filament bundles, indicating a significant rearrangement of actin stress fibers in the absence of RNASET2 (Figure 5A). Since endogenously expressed RNASET2 is effectively secreted by OVCAR3 cells, we wondered whether the observed re-organization of the cytoskeleton could be affected by a trans-acting mechanism mediated by extracellular RNASET2. Indeed, treatment of RNASET2-silenced OVCAR3 cells with recombinant RNASET2 readily restored the original cytoskeleton pattern detected in control cells (Figure 5A). By contrast, microtubule organization was not affected by RNASET2 silencing (Supplementary Figure 4), indicating a specific role for RNASET2 in the actin cytoskeleton.

Bottom Line: Indeed, RNASET2 expression levels were consistently found to increase following stress induction.Of note, a remarkable rearrangement of the actin cytoskeleton organization, together with changes in cell adhesion and motility, emerged as putative mechanisms by which such cell-autonomous role could occur.Altogether, these biological features allow to put forward the hypothesis that the RNASET2 protein can act as a molecular barrier for limiting the damages and tissue remodeling events occurring during the earlier step of cell transformation.

View Article: PubMed Central - PubMed

Affiliation: Department of Theoretical and Applied Sciences, Università degli Studi dell'Insubria, Varese, Italy.

ABSTRACT
As widely recognized, tumor growth entails a close and complex cross-talk among cancer cells and the surrounding tumor microenvironment. We recently described the human RNASET2 gene as one key player of such microenvironmental cross-talk. Indeed, the protein encoded by this gene is an extracellular RNase which is able to control cancer growth in a non-cell autonomous mode by inducing a sustained recruitment of immune-competent cells belonging to the monocyte/macrophage lineage within a growing tumor mass. Here, we asked whether this oncosuppressor gene is sensitive to stress challenges and whether it can trigger cell-intrinsic processes as well. Indeed, RNASET2 expression levels were consistently found to increase following stress induction. Moreover, changes in RNASET2 expression levels turned out to affect several cancer-related parameters in vitro in an ovarian cancer cell line model. Of note, a remarkable rearrangement of the actin cytoskeleton organization, together with changes in cell adhesion and motility, emerged as putative mechanisms by which such cell-autonomous role could occur. Altogether, these biological features allow to put forward the hypothesis that the RNASET2 protein can act as a molecular barrier for limiting the damages and tissue remodeling events occurring during the earlier step of cell transformation.

No MeSH data available.


Related in: MedlinePlus