Combined silencing of K-ras and Akt2 oncogenes achieves synergistic effects in inhibiting pancreatic cancer cell growth in vitro and in vivo

Shi, Xuhua; Zeng, Liang; Ren, Xue; Liu, T H

doi:10.1038/cgt.2008.82

Cited by 37 publications

(31 citation statements)

References 35 publications

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“…This animal model is simple but powerful to get a rough evaluation of tumor growth capacity in an in vivo mammalian system, and had been successfully used by our laboratories (27,44). It is better to confirm our results in other animal models of pancreatic cancer such as carcinogen-induced cancer or genetically engineered animals.…”

Section: Discussionsupporting

confidence: 70%

Targeted Degradation of KRAS by an Engineered Ubiquitin Ligase Suppresses Pancreatic Cancer Cell Growth In Vitro and In Vivo

Zhou

et al. 2013

Molecular Cancer Therapeutics

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KRAS is an attractive pancreatic ductal adenocarcinoma (PDAC) therapeutic target. E3 ligase is thought to be the component of the ubiquitin conjugation system that is directly responsible for substrate recognition. In this study, an engineered E3 ubiquitin ligase (RC-U) was generated to target the KRAS oncoprotein for ubiquitination and degradation. The engineered E3 ubiquitin ligases (RC-U) were constructed (pRC-U and lentivirus-expressing RC-U). After transfecting the pRC-U plasmid into human pancreatic cancer cells, KRAS expression levels were determined. KRAS expression was also evaluated in cells transfected with pRC-U and treated with MG-132 or cycloheximide. Interactions between RC-U and KRAS as well as whether RC-U could ubiquitinate KRAS were investigated. Extracellular signal-regulated kinase 1/2 (ERK1/2) and phosphorylated ERK 1/2 (pERK1/2) levels were examined in pancreatic cancer cells transfected with pRC-U. The effects of RC-U on pancreatic cancer cell growth were assessed. RC-U decreased KRAS protein levels. After pRC-U transfection, KRAS stability was increased in the presence of MG-132. HEK 293T cells were transfected with a mutant KRAS construct together with pRC-U and incubated with cycloheximide to inhibit new protein synthesis. The exogenous mutant KRAS oncoproteinwasdegradedmorequickly. RC-Ucan bindKRASand KRAScan beubiquitinatedbyRC-U.pERK1/2 protein levels were decreased. RC-U resulted in reduced cell proliferation in vitro and in vivo. KRAS destruction by RC-U occurred through a ubiquitin-dependent, proteasome-mediated degradation pathway. RC-U inhibited pancreatic cancer cell growth in vitro and in vivo. Mol Cancer Ther; 12(3); 286-94. Ó2012 AACR.

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Section: Discussionsupporting

confidence: 70%

Targeted Degradation of KRAS by an Engineered Ubiquitin Ligase Suppresses Pancreatic Cancer Cell Growth In Vitro and In Vivo

Zhou

et al. 2013

Molecular Cancer Therapeutics

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“…While K-Ras dependency has been shown to correlate with elevated expression of K-Ras and E-cadherin, the contribution of two major K-Ras downstream signaling molecules, Akt and MAPK, to K-Ras dependency is unclear [17, 18]. Compared with in vitro culture conditions, however, K-Ras mutant cells are known to be more broadly dependent on K-Ras in vivo [19-21]. Cells change the strength of many signaling pathways in response to different culture conditions, suggesting that the importance of specific signaling pathways for survival or proliferation would change in response to distinct environmental changes [22-24].…”

Section: Introductionmentioning

confidence: 99%

Enhanced MET Translation and Signaling Sustains K-Ras–Driven Proliferation under Anchorage-Independent Growth Conditions

et al. 2015

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Oncogenic K-Ras mutation occurs frequently in several types of cancers including pancreatic and lung cancers. Tumors with K-Ras mutation are resistant to chemotherapeutic drugs as well as molecular targeting agents. Although numerous approaches are ongoing to find effective ways to treat these tumors, there are still no effective therapies for K-Ras mutant cancer patients. Here we report that K-Ras mutant cancers are more dependent on K-Ras in anchorage independent culture conditions than in monolayer culture conditions. In seeking to determine mechanisms that contribute to the K-Ras dependency in anchorage independent culture conditions, we discovered the involvement of Met in K-Ras-dependent, anchorage independent cell growth. The Met signaling pathway is enhanced and plays an indispensable role in anchorage independent growth even in cells in which Met is not amplified. Indeed, Met expression is elevated under anchorage-independent growth conditions and is regulated by K-Ras in a MAPK/ERK kinase (MEK)-dependent manner. Remarkably, in spite of a global down-regulation of mRNA translation during anchorage independent growth, we find that Met mRNA translation is specifically enhanced under these conditions. Importantly, ectopic expression of an active Met mutant rescues K-Ras ablation-derived growth suppression, indicating that K-Ras mediated Met expression drives “K-Ras addiction” in anchorage independent conditions. Our results indicate that enhanced Met expression and signaling is essential for anchorage independent growth of K-Ras mutant cancer cells and suggests that pharmacological inhibitors of Met could be effective for K-Ras mutant tumor patients.

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“…1–4 Among the 3 members of the Akt family, Akt2 has been implicated in several human malignancies, including ovarian, breast, and PaCas. 2,5–9 …”

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confidence: 99%

The Phosphatase PHLPP1 Regulates Akt2, Promotes Pancreatic Cancer Cell Death, and Inhibits Tumor Formation

et al. 2012

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BACKGROUND & AIMS The kinase Akt mediates resistance of pancreatic cancer (PaCa) cells to death and is constitutively active (phosphorylated) in cancer cells. Whereas the kinases that activate Akt are well characterized, less is known about phosphatases that dephosporylate and thereby inactivate it. We investigated regulation of Akt activity and cell death by the phosphatases PHLPP1 and PHLPP2 in PaCa cells, mouse models of PaCa, and human pancreatic ductal adenocarcinoma (PDAC). METHODS We measured the effects of PHLPP overexpression or knockdown with small interfering RNAs on Akt activation and cell death. We examined regulation of PHLPPs by growth factors and reactive oxygen species, as well as associations between PHLPPs and tumorigenesis. RESULTS PHLPP overexpression inactivated Akt, whereas PHLPP knockdown increased phosphorylation of Akt in PaCa cells. Levels of PHLPPs were greatly reduced in human PDAC and in mouse genetic and xenograft models of PaCa. PHLPP activities in PaCa cells were down-regulated by growth factors and Nox4 reduced nicotinamide adenine dinucleotide phosphate oxidase. PHLPP1 selectively dephosphorylated Akt2, whereas PHLPP2 selectively dephosphorylated Akt1. Akt2, but not Akt1, was up-regulated in PDAC, and Akt2 levels correlated with mortality. Consistent with these results, high levels of PHLPP1, which dephosphorylates Akt2 (but not PHLPP2, which dephosphorylates Akt1), correlated with longer survival times of patients with PDAC. In mice, xenograft tumors derived from PaCa cells that overexpress PHLPP1 (but not PHLPP2) had inactivated Akt, greater extent of apoptosis, and smaller size. CONCLUSIONS PHLPP1 has tumor suppressive activity and might represent a therapeutic or diagnostic tool for PDAC.

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Combined silencing of K-ras and Akt2 oncogenes achieves synergistic effects in inhibiting pancreatic cancer cell growth in vitro and in vivo

Cited by 37 publications

References 35 publications

Targeted Degradation of KRAS by an Engineered Ubiquitin Ligase Suppresses Pancreatic Cancer Cell Growth In Vitro and In Vivo

Targeted Degradation of KRAS by an Engineered Ubiquitin Ligase Suppresses Pancreatic Cancer Cell Growth In Vitro and In Vivo

Enhanced MET Translation and Signaling Sustains K-Ras–Driven Proliferation under Anchorage-Independent Growth Conditions

The Phosphatase PHLPP1 Regulates Akt2, Promotes Pancreatic Cancer Cell Death, and Inhibits Tumor Formation

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