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Reactivation of suppressed RhoB is a critical step for the inhibition of anaplastic thyroid cancer growth.

ABSTRACT: Anaplastic thyroid carcinoma (ATC) is a highly aggressive form of the disease for which new therapeutic options are desperately needed. Previously, we showed that the high-affinity peroxisome proliferator-activated receptor gamma (PPARgamma) agonist, RS5444, inhibits cell proliferation of ATC cells via induction of the cyclin-dependent kinase inhibitor p21(WAF1/CIP1) (p21). We show here that up-regulation of RhoB is a critical step in PPARgamma-mediated activation of p21-induced cell stasis. Using multiple independently derived ATC cell lines, we found that treatment with RS5444 leads to the up-regulation of RhoB and subsequent activation of p21, and that silencing of RhoB by RNAi blocks the ability of RS5444 to induce p21 and to inhibit cell proliferation. Our results show that transcriptional regulation of RhoB by the nuclear transcription factor PPARgamma is responsible for the induction of p21 mRNA and protein. We further implicate RhoB as a key signaling effector for the growth inhibition of ATC, as treatment with a histone deacetylase inhibitor shown to increase RhoB expression in lung cancer cells caused the up-regulation of RhoB in ATC cells accompanied by increased expression of p21 and inhibition of cell proliferation; this effect occurred even in ATC cells that were unresponsive to RS5444 due to a lack of expression of PPARgamma. Our results implicate RhoB as a novel intermediate in critical signaling pathways and as an additional target for therapeutic intervention in ATC.

SUBMITTER: Marlow LA

PROVIDER: S-EPMC2644344 | biostudies-literature | 2009 Feb

REPOSITORIES: biostudies-literature

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Reactivation of suppressed RhoB is a critical step for the inhibition of anaplastic thyroid cancer growth.

Marlow Laura A LA Reynolds Lisa A LA Cleland Alan S AS Cooper Simon J SJ Gumz Michelle L ML Kurakata Shinichi S Fujiwara Kosaku K Zhang Ying Y Sebo Thomas T Grant Clive C McIver Bryan B Wadsworth J Trad JT Radisky Derek C DC Smallridge Robert C RC Copland John A JA

Cancer research 20090210 4

Anaplastic thyroid carcinoma (ATC) is a highly aggressive form of the disease for which new therapeutic options are desperately needed. Previously, we showed that the high-affinity peroxisome proliferator-activated receptor gamma (PPARgamma) agonist, RS5444, inhibits cell proliferation of ATC cells via induction of the cyclin-dependent kinase inhibitor p21(WAF1/CIP1) (p21). We show here that up-regulation of RhoB is a critical step in PPARgamma-mediated activation of p21-induced cell stasis. Usi ...[more]

PMID: 19208833

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Project description:BackgroundAnaplastic thyroid cancer (ATC) is rare, accounting for 1-2% of thyroid malignancies. Median survival is only 3-10 months, and the optimal therapeutic approach has not been established. This study aimed to evaluate outcomes in ATC based on treatment modality.MethodsRetrospective review was performed for patients treated at a single institution between 1990 and 2015. Demographic and clinical covariates were extracted from the medical record. Overall survival (OS) was modeled using Kaplan Meier curves for different treatment modalities. Univariate and multivariate analyses were conducted to assess the relationships between treatment and disease characteristics and OS.Results28 patients with ATC were identified (n = 16 female, n = 12 male; n = 22 Caucasian, n = 6 African-American; median age 70.9). Majority presented as Stage IVB (71.4%). Most patients received multimodality therapy. 19 patients underwent local surgical resection. 21 patients received locoregional external beam radiotherapy (EBRT) with a median cumulative dose of 3,000 cGy and median number of fractions of 16. 14 patients received systemic therapy (n = 11 concurrent with EBRT), most commonly doxorubicin (n = 9). 16 patients were never disease free, 11 patients had disease recurrence, and 1 patient had no evidence of disease progression. Median OS was 4 months with 1-year survival of 17.9%. Regression analysis showed that EBRT (HR: 0.174; 95% CI: 0.050-0.613; p=0.007) and surgical resection (HR: 0.198; 95% CI: 0.065-0.598; p=0.004) were associated with improved OS. Administration of chemotherapy was not associated with OS.ConclusionsAnaplastic thyroid cancer patients receiving EBRT to the thyroid area/neck and/or surgical resection had better OS than patients without these therapies, though selection bias likely contributed to improved outcomes since patients who can undergo these therapies tend to have better performance status. Prognosis remains poor overall, and new therapeutic approaches are needed to improve outcomes.

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Reactivation of suppressed RhoB is a critical step for the inhibition of anaplastic thyroid cancer growth.

Publications

Reactivation of suppressed RhoB is a critical step for the inhibition of anaplastic thyroid cancer growth.

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