Quantitative phosphoproteomic analysis identifies novel functional pathways of tumor suppressor DLC1 in estrogen receptor positive breast cancer

Deleted in Liver Cancer-1 (DLC1), a member of the RhoGAP family of proteins, functions as a tumor suppressor in several cancers including breast cancer. However, its clinical relevance is unclear in breast cancer. In this study, expression of DLC1 was correlated with prognosis using publicly available breast cancer gene expression datasets and quantitative Reverse Transcription PCR in cohorts of Estrogen Receptor-positive (ER+) breast cancer. Low expression of DLC1 correlates with poor prognosis in patients with ER+ breast cancer with further decrease in metastatic lesions. The Cancer Genome Atlas (TCGA) data showed that down regulation of DLC1 is not due to methylation or mutations. To seek further insights in understanding the role of DLC1 in ER+ breast cancer, we stably overexpressed DLC1-full-length (DLC1-FL) in T-47D breast cancer cells; this inhibited cell colony formation significantly in vitro compared to its control counterpart. Label-free global proteomic and TiO2 phosphopeptide enrichment assays (ProteomeXchange identifier PXD008220) showed that 205 and 122 phosphopeptides were unique to DLC1-FL cells and T-47D-control cells, respectively, whereas 6,726 were quantified by phosphoproteomics analysis in both conditions. The top three significant clusters of differentially phosphopeptides identified by DAVID pathway analysis represent cell-cell adhesion, mRNA processing and splicing, and transcription regulation. Phosphoproteomics analysis documented an inverse relation between DLC1 expression and several phosphopeptides including epithelial cell transforming sequence 2 (ECT2). Decreased phosphorylation of ECT2 at the residue T359, critical for its active conformational change, was validated by western blot. In addition, the ECT2 T359-containing phosphopeptide was detected in both basal and luminal patient-derived breast cancers breast cancer phosphoproteomics data on the Clinical Proteomic Tumor Analysis Consortium (CPTAC) Assay portal. Together, for the first time, this implicates ECT2 phosphorylation in breast cancer, which has been proposed as a therapeutic target in lung cancer. In conclusion, this data suggests that low expression of DLC1 is associated with poor prognosis. Targeting ECT2 phosphopeptides could provide a promising mechanism for controlling poor prognosis seen in DLC1low ER+ breast cancer.

Medienart:

E-Artikel

Erscheinungsjahr:

2018

Erschienen:

2018

Enthalten in:

Zur Gesamtaufnahme - volume:13

Enthalten in:

PloS one - 13(2018), 10 vom: 02., Seite e0204658

Sprache:

Englisch

Beteiligte Personen:

Gökmen-Polar, Yesim [VerfasserIn]
True, Jason D [VerfasserIn]
Vieth, Edyta [VerfasserIn]
Gu, Yuan [VerfasserIn]
Gu, Xiaoping [VerfasserIn]
Qi, Guihong D [VerfasserIn]
Mosley, Amber L [VerfasserIn]
Badve, Sunil S [VerfasserIn]

Links:

Volltext

Themen:

DLC1 protein, human
GTPase-Activating Proteins
Journal Article
Proto-Oncogene Proteins
RNA, Messenger
Receptors, Estrogen
Research Support, Non-U.S. Gov't
Tumor Suppressor Proteins

Anmerkungen:

Date Completed 11.03.2019

Date Revised 11.03.2019

published: Electronic-eCollection

Citation Status MEDLINE

doi:

10.1371/journal.pone.0204658

funding:

Förderinstitution / Projekttitel:

PPN (Katalog-ID):

NLM289136512