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Inhibition of CDK-mediated phosphorylation of Smad3 results in decreased oncogenesis in triple negative breast cancer cells.

ABSTRACT: Breast cancer onset and disease progression have been linked to members of the TGF? superfamily and their downstream signaling components, the Smads. Alterations in Smad3 signaling are associated with the dichotomous role of TGF? in malignancy, mediating both tumor suppressant and pro-metastatic behaviors. Overexpression of cell cycle regulators, cyclins D and E, renders cyclin-dependent kinases (CDKs) 4/2 hyperactive. Noncanonical phosphorylation of Smad3 by CDK4/2 inhibits tumor suppressant actions of Smad3. We hypothesized that CDK inhibition (CDKi) would restore Smad3 action and help promote cancer cell regression. Treatment of triple-negative breast cancer (TNBC) cell lines (MDA-MB-231, MDA-MB-436, Hs578T) with CDK2i or CDK4i resulted in increased Smad3 activity and decreased cell migration. Transfection with a 5M Smad3 construct containing inhibitory mutations in 5 CDK phosphorylation sites also resulted in decreased TNBC cell migration and invasion. MDA-MB-231 cells treated with CDK2i or CDK4i resulted in decreased Smad3 protein phosphorylation at the CDK phosphorylation T179 site, decreased MMP2 and c-myc expression, and increased p15 and p21 expression. Using a novel transfected cell array, we found that CDK2i treatment decreased activity of the epithelial-to-mesenchymal transition related transcription factors Snail and Twist. In vivo studies in an MDA-MB-231 tumor model showed that individual and combination treatment with paclitaxel and CDK2i resulted in decreased tumor volume and Ki67 staining. Collectively, these data support further investigation of targeted CDK inhibitors as a promising therapeutic strategy for TNBC, a breast cancer subtype with limited treatment options.

SUBMITTER: Tarasewicz E

PROVIDER: S-EPMC4614520 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Inhibition of CDK-mediated phosphorylation of Smad3 results in decreased oncogenesis in triple negative breast cancer cells.

Tarasewicz Elizabeth E Rivas Lisbi L Hamdan Randala R Dokic Danijela D Parimi Vamsi V Bernabe Beatriz Penalver BP Thomas Alexandra A Shea Lonnie D LD Jeruss Jacqueline S JS

Cell cycle (Georgetown, Tex.) 20140101 20

Breast cancer onset and disease progression have been linked to members of the TGFβ superfamily and their downstream signaling components, the Smads. Alterations in Smad3 signaling are associated with the dichotomous role of TGFβ in malignancy, mediating both tumor suppressant and pro-metastatic behaviors. Overexpression of cell cycle regulators, cyclins D and E, renders cyclin-dependent kinases (CDKs) 4/2 hyperactive. Noncanonical phosphorylation of Smad3 by CDK4/2 inhibits tumor suppressant ac ...[more]

PMID: 25485498

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Project description:PurposeAnti-EGFR antibodies show limited response in breast cancer, partly due to activation of compensatory pathways. Furthermore, despite clinical success of CDK4/6 inhibitors in hormone receptor-positive tumors, aggressive triple-negative breast cancers (TNBCs) are largely resistant due to CDK2/cyclin E expression, while free CDK2 inhibitors display normal tissue toxicity, limiting their therapeutic application. A cetuximab-based antibody drug conjugate (ADC) carrying a CDK inhibitor selected based on oncogene dysregulation, alongside patient subgroup stratification, may provide EGFR-targeted delivery.Experimental designExpression of G1/S-phase cell cycle regulators were evaluated alongside EGFR in breast cancer. We conjugated cetuximab with CDK inhibitor SNS-032, for specific delivery to EGFR-expressing cells. We assessed ADC internalization, and its anti-tumor functions in vitro and in orthotopically-grown basal-like/TNBC xenografts.ResultsTranscriptomic (6173 primary, 27 baseline and matched post-chemotherapy residual tumors), scRNA-seq (150290 cells, 27 treatment-naïve tumors) and spatial transcriptomic (43 tumor sections, 22 TNBCs) analyses confirmed expression of CDK2 and its cyclin partners in basal-like/TNBCs, associated with EGFR. Spatiotemporal live-cell imaging and super-resolution confocal microscopy demonstrated ADC colocalization with late lysosomal clusters. The ADC inhibited cell cycle progression, induced cytotoxicity against high EGFR-expressing tumor cells and bystander killing of neighboring EGFR-low tumor cells, but minimal effects on immune cells. Despite carrying a small fraction of the drug, the ADC restricted EGFR-expressing spheroid and cell line/patient-derived xenograft tumor growth.ConclusionsExploiting EGFR overexpression, and dysregulated cell cycle in aggressive and treatment-refractory tumors, a cetuximab-CDK inhibitor ADC may provide selective and efficacious delivery of cell cycle-targeted agents to basal-like/TNBCs, including chemotherapy-resistant residual disease.

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Inhibition of CDK-mediated phosphorylation of Smad3 results in decreased oncogenesis in triple negative breast cancer cells.

Publications

Inhibition of CDK-mediated phosphorylation of Smad3 results in decreased oncogenesis in triple negative breast cancer cells.

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