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Loss of RASSF2 Enhances Tumorigencity of Lung Cancer Cells and Confers Resistance to Chemotherapy.

Clark J, Freeman J, Donninger H - Mol Biol Int (2012)

Bottom Line: RASSF2 is a novel pro-apoptotic effector of K-Ras that is frequently inactivated in a variety of primary tumors by promoter methylation.In this study, we confirm that RASSF2 and K-Ras form an endogenous complex, validating that RASSF2 is a bona fide K-Ras effector.Loss of RASSF2 expression resulted in a more aggressive phenotype that was characterized by enhanced cell proliferation and invasion, decreased cell adhesion, the ability to grow in an anchorage-independent manner and cell morphological changes.

View Article: PubMed Central - PubMed

Affiliation: Molecular Targets Program, Department of Medicine, James Graham Brown Cancer Center, University of Louisville, 505 S. Hancock Street, Louisville, KY 40202, USA.

ABSTRACT
RASSF2 is a novel pro-apoptotic effector of K-Ras that is frequently inactivated in a variety of primary tumors by promoter methylation. Inactivation of RASSF2 enhances K-Ras-mediated transformation and overexpression of RASSF2 suppresses tumor cell growth. In this study, we confirm that RASSF2 and K-Ras form an endogenous complex, validating that RASSF2 is a bona fide K-Ras effector. We adopted an RNAi approach to determine the effects of inactivation of RASSF2 on the transformed phenotype of lung cancer cells containing an oncogenic K-Ras. Loss of RASSF2 expression resulted in a more aggressive phenotype that was characterized by enhanced cell proliferation and invasion, decreased cell adhesion, the ability to grow in an anchorage-independent manner and cell morphological changes. This enhanced transformed phenotype of the cells correlated with increased levels of activated AKT, indicating that RASSF2 can modulate Ras signaling pathways. Loss of RASSF2 expression also confers resistance to taxol and cisplatin, two frontline therapeutics for the treatment of lung cancer. Thus we have shown that inactivation of RASSF2, a process that occurs frequently in primary tumors, enhances the transforming potential of activated K-Ras and our data suggests that RASSF2 may be a novel candidate for epigenetic-based therapy in lung cancer.

No MeSH data available.


Related in: MedlinePlus

Loss of RASSF2 enhances Ras-mediated signaling pathways. Lysates from the control H441 cells and those stably transfected with the RASSF2 shRNA constructs were prepared, fractionated on SDS gels, and immunoblotted with antibodies against phosphorylated or total AKT. Loss of RASSF2 expression increased the levels of phosphorylated AKT.
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fig5: Loss of RASSF2 enhances Ras-mediated signaling pathways. Lysates from the control H441 cells and those stably transfected with the RASSF2 shRNA constructs were prepared, fractionated on SDS gels, and immunoblotted with antibodies against phosphorylated or total AKT. Loss of RASSF2 expression increased the levels of phosphorylated AKT.

Mentions: Since loss of RASSF2 expression resulted in enhanced growth and transformation, we reasoned that inactivation of RASSF2 activated growth promoting pathways. In an effort to determine which prosurvival pathways were activated in the H441 cells knocked down for RASSF2, we analyzed the phosphorylation status of AKT in these cells. Western Blot analysis showed that levels of phosphorylated AKT increased in the cells stably expressing the RASSF2 shRNA constructs relative to control cells (Figure 5). Previous studies have found an association between the methylation status of RASSF2 and the levels of activated AKT. Oral squamous cell carcinomas in which RASSF2 is methylated showed higher levels of activated AKT [18]. Taken together, our results and those from previous reports suggest that loss of RASSF2 expression results in activation of growth promoting pathways.


Loss of RASSF2 Enhances Tumorigencity of Lung Cancer Cells and Confers Resistance to Chemotherapy.

Clark J, Freeman J, Donninger H - Mol Biol Int (2012)

Loss of RASSF2 enhances Ras-mediated signaling pathways. Lysates from the control H441 cells and those stably transfected with the RASSF2 shRNA constructs were prepared, fractionated on SDS gels, and immunoblotted with antibodies against phosphorylated or total AKT. Loss of RASSF2 expression increased the levels of phosphorylated AKT.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3368207&req=5

fig5: Loss of RASSF2 enhances Ras-mediated signaling pathways. Lysates from the control H441 cells and those stably transfected with the RASSF2 shRNA constructs were prepared, fractionated on SDS gels, and immunoblotted with antibodies against phosphorylated or total AKT. Loss of RASSF2 expression increased the levels of phosphorylated AKT.
Mentions: Since loss of RASSF2 expression resulted in enhanced growth and transformation, we reasoned that inactivation of RASSF2 activated growth promoting pathways. In an effort to determine which prosurvival pathways were activated in the H441 cells knocked down for RASSF2, we analyzed the phosphorylation status of AKT in these cells. Western Blot analysis showed that levels of phosphorylated AKT increased in the cells stably expressing the RASSF2 shRNA constructs relative to control cells (Figure 5). Previous studies have found an association between the methylation status of RASSF2 and the levels of activated AKT. Oral squamous cell carcinomas in which RASSF2 is methylated showed higher levels of activated AKT [18]. Taken together, our results and those from previous reports suggest that loss of RASSF2 expression results in activation of growth promoting pathways.

Bottom Line: RASSF2 is a novel pro-apoptotic effector of K-Ras that is frequently inactivated in a variety of primary tumors by promoter methylation.In this study, we confirm that RASSF2 and K-Ras form an endogenous complex, validating that RASSF2 is a bona fide K-Ras effector.Loss of RASSF2 expression resulted in a more aggressive phenotype that was characterized by enhanced cell proliferation and invasion, decreased cell adhesion, the ability to grow in an anchorage-independent manner and cell morphological changes.

View Article: PubMed Central - PubMed

Affiliation: Molecular Targets Program, Department of Medicine, James Graham Brown Cancer Center, University of Louisville, 505 S. Hancock Street, Louisville, KY 40202, USA.

ABSTRACT
RASSF2 is a novel pro-apoptotic effector of K-Ras that is frequently inactivated in a variety of primary tumors by promoter methylation. Inactivation of RASSF2 enhances K-Ras-mediated transformation and overexpression of RASSF2 suppresses tumor cell growth. In this study, we confirm that RASSF2 and K-Ras form an endogenous complex, validating that RASSF2 is a bona fide K-Ras effector. We adopted an RNAi approach to determine the effects of inactivation of RASSF2 on the transformed phenotype of lung cancer cells containing an oncogenic K-Ras. Loss of RASSF2 expression resulted in a more aggressive phenotype that was characterized by enhanced cell proliferation and invasion, decreased cell adhesion, the ability to grow in an anchorage-independent manner and cell morphological changes. This enhanced transformed phenotype of the cells correlated with increased levels of activated AKT, indicating that RASSF2 can modulate Ras signaling pathways. Loss of RASSF2 expression also confers resistance to taxol and cisplatin, two frontline therapeutics for the treatment of lung cancer. Thus we have shown that inactivation of RASSF2, a process that occurs frequently in primary tumors, enhances the transforming potential of activated K-Ras and our data suggests that RASSF2 may be a novel candidate for epigenetic-based therapy in lung cancer.

No MeSH data available.


Related in: MedlinePlus