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RalA suppresses early stages of Ras-induced squamous cell carcinoma progression.

ABSTRACT: Ras proteins activate Raf and PI-3 kinases, as well as exchange factors for RalA and RalB GTPases. Many previous studies have reported that the Ral-signaling cascade contributes positively to Ras-mediated oncogenesis. Here, using a bioengineered tissue model of early steps in Ras-induced human squamous cell carcinoma of the skin, we found the opposite. Conversion of Ras-expressing keratinocytes from a premalignant to malignant state induced by decreasing E-cadherin function was associated with and required an approximately two to threefold decrease in RalA expression. Moreover, direct knockdown of RalA to a similar degree by shRNA expression in these cells reduced E-cadherin levels and also induced progression to a malignant phenotype. Knockdown of the Ral effector, Exo84, mimicked the effects of decreasing RalA levels in these engineered tissues. These phenomena can be explained by our finding that the stability of E-cadherin in Ras-expressing keratinocytes depends upon this RalA signaling cascade. These results imply that an important component of the early stages in squamous carcinoma progression may be a modest decrease in RalA gene expression that magnifies the effects of decreased E-cadherin expression by promoting its degradation.

SUBMITTER: Sowalsky AG

PROVIDER: S-EPMC2803332 | biostudies-literature | 2010 Jan

REPOSITORIES: biostudies-literature

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RalA suppresses early stages of Ras-induced squamous cell carcinoma progression.

Sowalsky A G AG Alt-Holland A A Shamis Y Y Garlick J A JA Feig L A LA

Oncogene 20091005 1

Ras proteins activate Raf and PI-3 kinases, as well as exchange factors for RalA and RalB GTPases. Many previous studies have reported that the Ral-signaling cascade contributes positively to Ras-mediated oncogenesis. Here, using a bioengineered tissue model of early steps in Ras-induced human squamous cell carcinoma of the skin, we found the opposite. Conversion of Ras-expressing keratinocytes from a premalignant to malignant state induced by decreasing E-cadherin function was associated with a ...[more]

PMID: 19802010

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Project description:BackgroundEsophageal cancer, especially esophageal squamous cell carcinoma (ESCC), is a common malignant tumor of the digestive tract. Bufalin is an effective anti-tumor compound. However, little is known about the regulatory mechanisms of Bufalin in ESCC. To investigate the effect and molecular mechanism of Bufalin on the proliferation, migration and invasion of ESCC cells will provide a more reliable basis for the application of Bufalin in clinical tumor therapy.MethodsFirst, the half-inhibitory concentration (IC50) of Bufalin was evaluated by Cell Counting Kit-8 (CCK-8) assays. In vitro, the effects of Bufalin on the proliferation of the ECA109 cells was measured using CCK-8 and 5-ethynyl-2'-deoxyuridine assays. Wound-healing and transwell assays were used to evaluate the effects of Bufalin on the migration and invasion of the ECA109 cells. Further, to determine the mechanisms underlying the Bufalin-mediated suppression of cell progression in ESCC, total RNA was extracted from negative control (NC) and Bufalin treated cells to perform RNA-sequencing (RNA-seq) to screen for abnormally expressed genes. In vivo, the ECA 109 cells were subcutaneously injected into BALB/c nude mice to determine the effects of Bufalin on tumor cell proliferation. The protein inhibitor of activated signal transducer and activator of transcription 3 (PIAS3), signal transducer and activator of transcription 3 (STAT3), and phosphorylated STAT3 (p-STAT3) protein expression levels in the ECA109 cells were detected by Western blot.ResultsThe CCK-8 assays showed that the IC50 of Bufalin was 200 nM. The proliferation, migration, and invasion ability of the ECA109 cells was significantly inhibited in the Bufalin group in a concentration-dependent manner. In vivo, the Xenograft tumor model showed that Bufalin decreased the tumor volume and weight of the subcutaneous tumors. The RNA-seq results showed that the expression of PIAS3 was upregulated in the Bufalin group. Additionally, down-regulation of PIAS3 decreased the inhibition of STAT3, thereby increasing p-STAT3 expression. Finally, PIAS3 knockdown reversed the inhibitory effects of Bufalin on the proliferation, migration, and invasion of the ECA109 cells.ConclusionsBufalin may inhibit the proliferation, migration, and invasion of the ECA109 cells through the PIAS3/STAT3 signaling pathway.

Project description:BackgroundGlucose metabolism in cancer associated fibroblasts (CAFs) within the tumor microenvironment is a material and energy source for tumorigenesis and tumor development. However, the characteristics and important regulatory mechanisms of glucose metabolism in fibroblasts associated with oral squamous cell carcinoma (OSCC) are still unknown.MethodsWe successfully isolated, cultured, purified and identified CAFs and normal fibroblasts (NFs). Cell culture, immunohistochemistry (IHC) and CCK8, flow cytometry, Seahorse XF Analyzer, MitoTracker assay, western blotting (WB), transmission electron microscope, Quantitative real-time PCR (qPCR), immunofluorescence (IF), and Label-free quantitative proteomics assay, animal xenograft model studies and statistical analysis were applied in this study.ResultsWe demonstrated that the proliferation activity of CAFs was significantly enhanced as compared to NFs, while the apoptosis rate was significantly decreased. CAFs in OSCC preferentially use oxidative phosphorylation (OXPHOS) rather than glycolysis. Moreover, CAFs showed stronger maximal respiration, a larger substantial mitochondrial spare respiratory capacity (SRC) and higher adenosine triphosphate (ATP) production capacity than NFs. The results of mitotracker green fluorescence staining showed that compared with NFs, CAFs exhibited stronger green fluorescence. The results of WB showed the expression level of Peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) obviously increased in CAFs compared to NFs. These results confirmed that CAFs have greater mitochondrial activity and function than NFs. Furthermore, Label-free quantitative proteomics assays showed that both ATP synthase subunit O (ATP5O) and tumor necrosis factor receptor-associated protein 1 (TRAP1) are important differentially expressed proteins in the mitochondria of CAFs/NFs. Overexpression of TRAP1 in CAFs increased basal oxygen consumption rate (OCR), maximal respiration, ATP production and SRC. In vivo, overexpression TRAP1 expression in CAFs suppress tumor growth.ConclusionTaken together, the results indicated that TRAP1 is an important regulatory molecule of CAFs glucose metabolism and promotes OSCC progression by regulating the OXPHOS of CAFs.

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RalA suppresses early stages of Ras-induced squamous cell carcinoma progression.

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RalA suppresses early stages of Ras-induced squamous cell carcinoma progression.

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