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Presence of intratumoral platelets is associated with tumor vessel structure and metastasis.

Li R, Ren M, Chen N, Luo M, Deng X, Xia J, Yu G, Liu J, He B, Zhang X, Zhang Z, Zhang X, Ran B, Wu J - BMC Cancer (2014)

Bottom Line: Vascular permeability was evaluated by determination of intratumoral Evans blue and Miles vascular permeability assay.Furthermore, microdialysis was used to examining the intratumoral extracellular angiogenic growth factors (VEGF, TGF-β) by ELISA.Platelet depletion led to reduced tumor hypoxia and Met receptor activation and was associated with a decreased release of MMP-2, 9, PAI-1, VEGF, and TGF-β.

View Article: PubMed Central - HTML - PubMed

Affiliation: Drug Discovery Research Center, Luzhou Medical College, Luzhou, Sichuan, People's Republic of China. wuji@missouri.edu.

ABSTRACT

Background: Platelets play a fundamental role in maintaining hemostasis and have been shown to participate in hematogenous dissemination of tumor cells. Abundant platelets were detected in the tumor microenvironment outside of the blood vessel, thus, platelet -tumor cell interaction outside of the bloodstream may play a role in regulating primary tumor growth and metastasis initiation. However, it is unclear that platelet depletion affects tumor vessel structure and dynamics.

Methods: Using thrombocytopenia induction in two different tumor-bearing mouse models, tumor tissues were performed by Westernblotting and immunohistochemical staining. Vascular permeability was evaluated by determination of intratumoral Evans blue and Miles vascular permeability assay. Furthermore, microdialysis was used to examining the intratumoral extracellular angiogenic growth factors (VEGF, TGF-β) by ELISA.

Results: Platelet depletion showed no change in tumor growth and reduced lung metastasis. Platelet depletion led to reduced tumor hypoxia and Met receptor activation and was associated with a decreased release of MMP-2, 9, PAI-1, VEGF, and TGF-β. Tumor vessels in platelet-depleted mice showed impaired vessel density and maturation.

Conclusions: Our findings demonstrate that platelets within the primary tumor microenvironment play a critical role in the induction of vascular permeability and initiation of tumor metastasis.

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Related in: MedlinePlus

Platelets changed levels of TGF-β1, MMP-2,9, and PAI-1. TGF-β1 levels were measured by ELISA in plasma (A), microdialysates (B), and tumor hemogenates (C) as described in Materials and Methods. (D). Gel zymography analysis of MMP-2, 9 from microdialysates in tumors from PLT-depleted, control mice. (E). Western blot analysis of PAI-1 expression in tumors from PLT-depleted, control mice (normalized to β-actin). The results are expressed as the mean ± SEM. * p < 0.05.
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Figure 6: Platelets changed levels of TGF-β1, MMP-2,9, and PAI-1. TGF-β1 levels were measured by ELISA in plasma (A), microdialysates (B), and tumor hemogenates (C) as described in Materials and Methods. (D). Gel zymography analysis of MMP-2, 9 from microdialysates in tumors from PLT-depleted, control mice. (E). Western blot analysis of PAI-1 expression in tumors from PLT-depleted, control mice (normalized to β-actin). The results are expressed as the mean ± SEM. * p < 0.05.

Mentions: Considering that platelet-derived TGF-β1 plays a key role in regulating circulating cancer cell dissemination [3], we measured the influence of platelets on systemic and local TGF-β1 levels. Blood, extracellular microdialysate, and tumor samples were obtained from platelet-depleted, control, and co-implantation of B16/F10 mice. A significant increase in plasma TGF-β1 from co-implantation of B16/F10 group compared with B16/F10 alone (523 ± 49.75 pg/mL Vs. 329 ± 36.27 pg/mL, p < 0.05). The plasma TGF-β1 level of platelet-depleted mice was significantly lower than in control mice (252 ± 25.83 pg/mL Vs. 329 ± 36.27 pg/mL, p < 0.05) (Figure 6A). In comparison, an similar findings were found in microdialysates and tumor samples in which the TGF-β1 level of PLT-depletion was significantly lower than in control and co-implantation mice (Figure 6B and C).To better investigate the molecular mechanisms by which platelet depletion reduces metastasis in the tumor microenvironment, we further evaluated the expression of proteins that are involved in regulating the basal membrane and barrier cancer cell intravasion. Zymographic analysis of microdialysates revealed that the intensity of MMP-9 and MMP-2 bands in PLT-depletion were lower than in control groups (Figure 6D). Furthermore, MMP-9 and MMP-2 bands in the co-implantation group were more intense than in the control group. Plasminogen activator inhibitor-1 (PAI-1) protein level was reduced in platelet-depleted tumors compared with control and co-implantation tumors (Figure 6E), suggesting a lower capacity to cross through surrounding microenvironment by degrading several components of the extracellular matrix (ECM).


Presence of intratumoral platelets is associated with tumor vessel structure and metastasis.

Li R, Ren M, Chen N, Luo M, Deng X, Xia J, Yu G, Liu J, He B, Zhang X, Zhang Z, Zhang X, Ran B, Wu J - BMC Cancer (2014)

Platelets changed levels of TGF-β1, MMP-2,9, and PAI-1. TGF-β1 levels were measured by ELISA in plasma (A), microdialysates (B), and tumor hemogenates (C) as described in Materials and Methods. (D). Gel zymography analysis of MMP-2, 9 from microdialysates in tumors from PLT-depleted, control mice. (E). Western blot analysis of PAI-1 expression in tumors from PLT-depleted, control mice (normalized to β-actin). The results are expressed as the mean ± SEM. * p < 0.05.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4016490&req=5

Figure 6: Platelets changed levels of TGF-β1, MMP-2,9, and PAI-1. TGF-β1 levels were measured by ELISA in plasma (A), microdialysates (B), and tumor hemogenates (C) as described in Materials and Methods. (D). Gel zymography analysis of MMP-2, 9 from microdialysates in tumors from PLT-depleted, control mice. (E). Western blot analysis of PAI-1 expression in tumors from PLT-depleted, control mice (normalized to β-actin). The results are expressed as the mean ± SEM. * p < 0.05.
Mentions: Considering that platelet-derived TGF-β1 plays a key role in regulating circulating cancer cell dissemination [3], we measured the influence of platelets on systemic and local TGF-β1 levels. Blood, extracellular microdialysate, and tumor samples were obtained from platelet-depleted, control, and co-implantation of B16/F10 mice. A significant increase in plasma TGF-β1 from co-implantation of B16/F10 group compared with B16/F10 alone (523 ± 49.75 pg/mL Vs. 329 ± 36.27 pg/mL, p < 0.05). The plasma TGF-β1 level of platelet-depleted mice was significantly lower than in control mice (252 ± 25.83 pg/mL Vs. 329 ± 36.27 pg/mL, p < 0.05) (Figure 6A). In comparison, an similar findings were found in microdialysates and tumor samples in which the TGF-β1 level of PLT-depletion was significantly lower than in control and co-implantation mice (Figure 6B and C).To better investigate the molecular mechanisms by which platelet depletion reduces metastasis in the tumor microenvironment, we further evaluated the expression of proteins that are involved in regulating the basal membrane and barrier cancer cell intravasion. Zymographic analysis of microdialysates revealed that the intensity of MMP-9 and MMP-2 bands in PLT-depletion were lower than in control groups (Figure 6D). Furthermore, MMP-9 and MMP-2 bands in the co-implantation group were more intense than in the control group. Plasminogen activator inhibitor-1 (PAI-1) protein level was reduced in platelet-depleted tumors compared with control and co-implantation tumors (Figure 6E), suggesting a lower capacity to cross through surrounding microenvironment by degrading several components of the extracellular matrix (ECM).

Bottom Line: Vascular permeability was evaluated by determination of intratumoral Evans blue and Miles vascular permeability assay.Furthermore, microdialysis was used to examining the intratumoral extracellular angiogenic growth factors (VEGF, TGF-β) by ELISA.Platelet depletion led to reduced tumor hypoxia and Met receptor activation and was associated with a decreased release of MMP-2, 9, PAI-1, VEGF, and TGF-β.

View Article: PubMed Central - HTML - PubMed

Affiliation: Drug Discovery Research Center, Luzhou Medical College, Luzhou, Sichuan, People's Republic of China. wuji@missouri.edu.

ABSTRACT

Background: Platelets play a fundamental role in maintaining hemostasis and have been shown to participate in hematogenous dissemination of tumor cells. Abundant platelets were detected in the tumor microenvironment outside of the blood vessel, thus, platelet -tumor cell interaction outside of the bloodstream may play a role in regulating primary tumor growth and metastasis initiation. However, it is unclear that platelet depletion affects tumor vessel structure and dynamics.

Methods: Using thrombocytopenia induction in two different tumor-bearing mouse models, tumor tissues were performed by Westernblotting and immunohistochemical staining. Vascular permeability was evaluated by determination of intratumoral Evans blue and Miles vascular permeability assay. Furthermore, microdialysis was used to examining the intratumoral extracellular angiogenic growth factors (VEGF, TGF-β) by ELISA.

Results: Platelet depletion showed no change in tumor growth and reduced lung metastasis. Platelet depletion led to reduced tumor hypoxia and Met receptor activation and was associated with a decreased release of MMP-2, 9, PAI-1, VEGF, and TGF-β. Tumor vessels in platelet-depleted mice showed impaired vessel density and maturation.

Conclusions: Our findings demonstrate that platelets within the primary tumor microenvironment play a critical role in the induction of vascular permeability and initiation of tumor metastasis.

Show MeSH
Related in: MedlinePlus