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Knockdown of EphB1 receptor decreases medulloblastoma cell growth and migration and increases cellular radiosensitization.

Bhatia S, Baig NA, Timofeeva O, Pasquale EB, Hirsch K, MacDonald TJ, Dritschilo A, Lee YC, Henkemeyer M, Rood B, Jung M, Wang XJ, Kool M, Rodriguez O, Albanese C, Karam SD - Oncotarget (2015)

Bottom Line: EphB1 downregulation reduced cell growth and viability, decreased the expression of important cell cycle regulators, and increased the percentage of cells in G1 phase of the cell cycle.In addition, EphB1 knockdown in DAOY cells resulted in significant decrease in migration, which correlated with decreased β1-integrin expression and levels of phosphorylated Src.Using genetically engineered mouse models, we established that genetic loss of EphB1 resulted in a significant delay in tumor recurrence following irradiation compared to EphB1-expressing control tumors.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiation Oncology, University of Colorado Denver, Anschutz Medical Campus, Aurora, CO, USA.

ABSTRACT
The expression of members of the Eph family of receptor tyrosine kinases and their ephrin ligands is frequently dysregulated in medulloblastomas. We assessed the expression and functional role of EphB1 in medulloblastoma cell lines and engineered mouse models. mRNA and protein expression profiling showed expression of EphB1 receptor in the human medulloblastoma cell lines DAOY and UW228. EphB1 downregulation reduced cell growth and viability, decreased the expression of important cell cycle regulators, and increased the percentage of cells in G1 phase of the cell cycle. It also modulated the expression of proliferation, and cell survival markers. In addition, EphB1 knockdown in DAOY cells resulted in significant decrease in migration, which correlated with decreased β1-integrin expression and levels of phosphorylated Src. Furthermore, EphB1 knockdown enhanced cellular radiosensitization of medulloblastoma cells in culture and in a genetically engineered mouse medulloblastoma model. Using genetically engineered mouse models, we established that genetic loss of EphB1 resulted in a significant delay in tumor recurrence following irradiation compared to EphB1-expressing control tumors. Taken together, our findings establish that EphB1 plays a key role in medulloblastoma cell growth, viability, migration, and radiation sensitivity, making EphB1 a promising therapeutic target.

No MeSH data available.


Related in: MedlinePlus

Proposed hypothetical modelEphB1 receptor knockdown radiosensitizes medulloblastoma cells and decreases cell growth, and enhances the percentage of cells in G1 phase of cell cycle. Additionally, siRNA-mediated EphB1 knockdown reduces cell migration.
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Figure 9: Proposed hypothetical modelEphB1 receptor knockdown radiosensitizes medulloblastoma cells and decreases cell growth, and enhances the percentage of cells in G1 phase of cell cycle. Additionally, siRNA-mediated EphB1 knockdown reduces cell migration.

Mentions: The Eph/ephrin system has been reported to play a key role in cancer cell growth and proliferation. Previous studies report anti-proliferative effects of Eph receptors, mediated primarily by suppression of the ERK/MAPK pathway [29, 38–41]. In contrast, recent findings indicate that some Eph receptors promote cell proliferation, for example in colorectal cancer and in the developing nervous system [30, 42–44]. During development, lack of EphB1 in a mouse model has been reported to significantly reduce the number of neural progenitors in the hippocampus, as well as disrupt the proper migration and organization of neural progenitors [42]. Consistent with these findings, we report that EphB1 knockdown decreases medulloblastoma cell growth and viability. Furthermore, our data provide mechanistic insights into how EphB1 downregulation affects medulloblastoma cell growth and survival (Figure 9). The reduction in the growth and viability of EphB1 knockdown DAOY cells could be explained in part by the decreased expression of cyclin E, a master regulator of cell cycle progression, which in turn results in decreased levels of phosphorylated Rb and E2F1 proteins and also affects the activation of a checkpoint kinase, Chk2, resulting in cell cycle arrest. In addition to playing a regulatory role, overexpression of cyclin E has been linked to tumorigenesis in different cancers [45]. In view of this, inhibition of cyclin E following EphB1 knockdown likely plays a role in the observed inhibition of medulloblastoma tumor growth. Importantly, the decreased ability of DAOY cells to progress from G1 to S phase following EphB1 knockdown, could ultimately be responsible for inhibiting their growth, proliferation, and survival as indicated by reduced expression of PCNA and decreased levels of phosphorylated Akt, and total AKT. Thus, our data clearly underscore the relevance of EphB1 knockdown in inhibiting medulloblastoma cell growth by affecting cell cycle, proliferation, and cell survival pathways. Cross-talk between Eph receptors and other receptor tyrosine kinases has been reported to contribute to malignant cell behavior [24, 31, 46]. The role of EGFR signaling in tumorigenesis is well established [47]. Our results show an appreciable decrease in the levels of phosphorylated EGFR and total EGFR following EphB1-specific siRNA treatment in DAOY cells, suggesting that the EphB1 receptor might be contributing to the metastatic behavior of medulloblastoma cells by functionally interacting with EGFR. This could be relevant in view of the fact that many human cancers have elevated expression of EGFR along with Eph receptors. Thus, targeted therapeutics developed against Eph receptors could potentially be a viable and effective treatment option against EGFR-positive cancers as well.


Knockdown of EphB1 receptor decreases medulloblastoma cell growth and migration and increases cellular radiosensitization.

Bhatia S, Baig NA, Timofeeva O, Pasquale EB, Hirsch K, MacDonald TJ, Dritschilo A, Lee YC, Henkemeyer M, Rood B, Jung M, Wang XJ, Kool M, Rodriguez O, Albanese C, Karam SD - Oncotarget (2015)

Proposed hypothetical modelEphB1 receptor knockdown radiosensitizes medulloblastoma cells and decreases cell growth, and enhances the percentage of cells in G1 phase of cell cycle. Additionally, siRNA-mediated EphB1 knockdown reduces cell migration.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4496193&req=5

Figure 9: Proposed hypothetical modelEphB1 receptor knockdown radiosensitizes medulloblastoma cells and decreases cell growth, and enhances the percentage of cells in G1 phase of cell cycle. Additionally, siRNA-mediated EphB1 knockdown reduces cell migration.
Mentions: The Eph/ephrin system has been reported to play a key role in cancer cell growth and proliferation. Previous studies report anti-proliferative effects of Eph receptors, mediated primarily by suppression of the ERK/MAPK pathway [29, 38–41]. In contrast, recent findings indicate that some Eph receptors promote cell proliferation, for example in colorectal cancer and in the developing nervous system [30, 42–44]. During development, lack of EphB1 in a mouse model has been reported to significantly reduce the number of neural progenitors in the hippocampus, as well as disrupt the proper migration and organization of neural progenitors [42]. Consistent with these findings, we report that EphB1 knockdown decreases medulloblastoma cell growth and viability. Furthermore, our data provide mechanistic insights into how EphB1 downregulation affects medulloblastoma cell growth and survival (Figure 9). The reduction in the growth and viability of EphB1 knockdown DAOY cells could be explained in part by the decreased expression of cyclin E, a master regulator of cell cycle progression, which in turn results in decreased levels of phosphorylated Rb and E2F1 proteins and also affects the activation of a checkpoint kinase, Chk2, resulting in cell cycle arrest. In addition to playing a regulatory role, overexpression of cyclin E has been linked to tumorigenesis in different cancers [45]. In view of this, inhibition of cyclin E following EphB1 knockdown likely plays a role in the observed inhibition of medulloblastoma tumor growth. Importantly, the decreased ability of DAOY cells to progress from G1 to S phase following EphB1 knockdown, could ultimately be responsible for inhibiting their growth, proliferation, and survival as indicated by reduced expression of PCNA and decreased levels of phosphorylated Akt, and total AKT. Thus, our data clearly underscore the relevance of EphB1 knockdown in inhibiting medulloblastoma cell growth by affecting cell cycle, proliferation, and cell survival pathways. Cross-talk between Eph receptors and other receptor tyrosine kinases has been reported to contribute to malignant cell behavior [24, 31, 46]. The role of EGFR signaling in tumorigenesis is well established [47]. Our results show an appreciable decrease in the levels of phosphorylated EGFR and total EGFR following EphB1-specific siRNA treatment in DAOY cells, suggesting that the EphB1 receptor might be contributing to the metastatic behavior of medulloblastoma cells by functionally interacting with EGFR. This could be relevant in view of the fact that many human cancers have elevated expression of EGFR along with Eph receptors. Thus, targeted therapeutics developed against Eph receptors could potentially be a viable and effective treatment option against EGFR-positive cancers as well.

Bottom Line: EphB1 downregulation reduced cell growth and viability, decreased the expression of important cell cycle regulators, and increased the percentage of cells in G1 phase of the cell cycle.In addition, EphB1 knockdown in DAOY cells resulted in significant decrease in migration, which correlated with decreased β1-integrin expression and levels of phosphorylated Src.Using genetically engineered mouse models, we established that genetic loss of EphB1 resulted in a significant delay in tumor recurrence following irradiation compared to EphB1-expressing control tumors.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiation Oncology, University of Colorado Denver, Anschutz Medical Campus, Aurora, CO, USA.

ABSTRACT
The expression of members of the Eph family of receptor tyrosine kinases and their ephrin ligands is frequently dysregulated in medulloblastomas. We assessed the expression and functional role of EphB1 in medulloblastoma cell lines and engineered mouse models. mRNA and protein expression profiling showed expression of EphB1 receptor in the human medulloblastoma cell lines DAOY and UW228. EphB1 downregulation reduced cell growth and viability, decreased the expression of important cell cycle regulators, and increased the percentage of cells in G1 phase of the cell cycle. It also modulated the expression of proliferation, and cell survival markers. In addition, EphB1 knockdown in DAOY cells resulted in significant decrease in migration, which correlated with decreased β1-integrin expression and levels of phosphorylated Src. Furthermore, EphB1 knockdown enhanced cellular radiosensitization of medulloblastoma cells in culture and in a genetically engineered mouse medulloblastoma model. Using genetically engineered mouse models, we established that genetic loss of EphB1 resulted in a significant delay in tumor recurrence following irradiation compared to EphB1-expressing control tumors. Taken together, our findings establish that EphB1 plays a key role in medulloblastoma cell growth, viability, migration, and radiation sensitivity, making EphB1 a promising therapeutic target.

No MeSH data available.


Related in: MedlinePlus