Dataset Information

Metastasis of tumor cells is enhanced by downregulation of Bit1.

ABSTRACT: Resistance to anoikis, which is defined as apoptosis induced by loss of integrin-mediated cell attachment to the extracellular matrix, is a determinant of tumor progression and metastasis. We have previously identified the mitochondrial Bit1 (Bcl-2 inhibitor of transcription) protein as a novel anoikis effector whose apoptotic function is independent from caspases and is uniquely controlled by integrins. In this report, we examined the possibility that Bit1 is suppressed during tumor progression and that Bit1 downregulation may play a role in tumor metastasis.Using a human breast tumor tissue array, we found that Bit1 expression is suppressed in a significant fraction of advanced stages of breast cancer. Targeted disruption of Bit1 via shRNA technology in lowly aggressive MCF7 cells conferred enhanced anoikis resistance, adhesive and migratory potential, which correlated with an increase in active Extracellular kinase regulated (Erk) levels and a decrease in Erk-directed phosphatase activity. These pro-metastasis phenotypes were also observed following downregulation of endogenous Bit1 in Hela and B16F1 cancer cell lines. The enhanced migratory and adhesive potential of Bit1 knockdown cells is in part dependent on their high level of Erk activation since down-regulating Erk in these cells attenuated their enhanced motility and adhesive properties. The Bit1 knockdown pools also showed a statistically highly significant increase in experimental lung metastasis, with no differences in tumor growth relative to control clones in vivo using a BALB/c nude mouse model system. Importantly, the pulmonary metastases of Bit1 knockdown cells exhibited increased phospho-Erk staining.These findings indicate that downregulation of Bit1 conferred cancer cells with enhanced anoikis resistance, adhesive and migratory properties in vitro and specifically potentiated tumor metastasis in vivo. These results underscore the therapeutic importance of restoring Bit1 expression in cancer cells to circumvent metastasis at least in part through inhibition of the Erk pathway.

SUBMITTER: Karmali PP

PROVIDER: S-EPMC3160313 | biostudies-literature | 2011

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Metastasis of tumor cells is enhanced by downregulation of Bit1.

Karmali Priya Prakash PP Brunquell Chris C Tram Hau H Ireland Shubha Kale SK Ruoslahti Erkki E Biliran Hector H

PloS one 20110823 8

<h4>Background</h4>Resistance to anoikis, which is defined as apoptosis induced by loss of integrin-mediated cell attachment to the extracellular matrix, is a determinant of tumor progression and metastasis. We have previously identified the mitochondrial Bit1 (Bcl-2 inhibitor of transcription) protein as a novel anoikis effector whose apoptotic function is independent from caspases and is uniquely controlled by integrins. In this report, we examined the possibility that Bit1 is suppressed durin ...[more]

PMID: 21886829

Similar Datasets

Project description:Anoikis is a type of apoptosis induced by cell detachment from the extracellular matrix (ECM), which removes mislocalized cells. Acquisition of anoikis resistance is critical for cancer cells to survive during circulation and, thus, metastasize at a secondary site. Although the sensitization of cancer cells to anoikis is a potential strategy to prevent metastasis, the mechanism underlying anoikis resistance is not well defined. Although family with sequence similarity 188 member B (FAM188B) is predicted as a new deubiquitinase (DUB) member, its biological function has not been fully studied. In this study, we demonstrated that FAM188B knockdown sensitized anoikis of lung cancer cell lines expressing WT-EGFR (A549 and H1299) or TKI-resistant EGFR mutant T790M/L858R (H1975). FAM188B knockdown using si-FAM188B inhibited the growth of all three human lung cancer cell lines cultured in both attachment and suspension conditions. FAM188B knockdown resulted in EGFR downregulation and thus decreased its activity. FAM188B knockdown decreased the activities of several oncogenic proteins downstream of EGFR that are involved in anoikis resistance, including pAkt, pSrc, and pSTAT3, with little changes to their protein levels. Intriguingly, si-FAM188B treatment increased EGFR mRNA levels but decreased its protein levels, which was reversed by treatment with the proteasomal inhibitor MG132, indicating that FAM188B regulates EGFR levels via the proteasomal pathway. In addition, cells transfected with si-FAM188B had decreased expression of FOXM1, an oncogenic transcription factor involved in cell growth and survival. Moreover, FAM188B downregulation reduced metastatic characteristics, such as cell adhesion, invasion, and migration, as well as growth in 3D culture conditions. Finally, tail vein injection of si-FAM188B-treated A549 cells resulted in a decrease in lung metastasis and an increase in mice survival in vivo. Taken together, these findings indicate that FAM188B plays an important role in anoikis resistance and metastatic characteristics by maintaining the levels of various oncogenic proteins and/or their activity, leading to tumor malignancy. Our study suggests FAM188B as a potential target for controlling tumor malignancy.

Dataset Information

Metastasis of tumor cells is enhanced by downregulation of Bit1.

Publications

Metastasis of tumor cells is enhanced by downregulation of Bit1.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets