SLUG is a direct transcriptional repressor of PTEN tumor suppressor.
BACKGROUND
PTEN/AKT signaling plays a key role in prostate cancer development and maintenance of prostate cancer stem cells. How other oncogenes or tumor suppressors interact with this pathway remain to be elucidated. SLUG is an zinc finger transcription factor of the Snail superfamily, and it promotes cancer metastasis and determines the mammary stem cell state.


METHODS
SLUG was overexpressed in cells by retroviral vector and knockdown of SLUG and PTEN was mediated by shRNAs-expressing lentiviruses. Expression level of SLUG and PTEN was examined by Western blot, RT-PCR, and qPCR analyses. PTEN promoter activity was measured by luciferase reporter assay. ChIP assay was used to measure the binding between SLUG and the PTEN promoter in vivo.


RESULTS
We showed that overexpression of SLUG decreased expression of PTEN tumor repressor in prostate cancer cell lines 22RV1 and DU145; conversely, knockdown of SLUG expression elevated PTEN expresson at both protein and RNA level in these cells. We demonstrated that SLUG overexpression inhibits PTEN promoter activity through the proximal promoter region in prostate cancer cells. By ChIP assay, we confirmed that SLUG directly binds to the PTEN promoter region covering the E-box sites. We also showed that Slug deficiency leads to an increased expression of PTEN in mouse embryo fibroblasts and prostate tissues. Importantly, we found that overexpression of SLUG increases drug resistance of DU145 prostate cancer cell line and knockdown of SLUG by shRNA sensitizes DU145 cell line to chemotherapeutic drugs. We further demonstrated that PTEN knockdown converts drug sensitivity of DU145 cells expressing SLUG shRNA to anticancer drugs.


CONCLUSIONS
We provide compelling evidence showing that PTEN is a direct functional target of SLUG. Our findings offer new insight in the regulation of the PTEN/AKT pathway and provide a molecular basis for potential targeted therapies of prostate cancer Prostate 75:907-916, 2015. © 2015 Wiley Periodicals, Inc.
Center for Molecular Medicine, Maine Medical Center Research Institute, Scarborough, Maine; Program in Biochemistry and Molecular Biology, University of Maine, Orono, Maine; Section on Membrane Biology, Program of Physical Biology, Eunice Kennedy Shriver National, Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland.
Berna
B
Uygur
Katrina
K
Abramo
Evgenia
E
Leikina
Calvin
C
Vary
Lucy
L
Liaw
Wen-Shu
WS
Wu
D000818:Animals; D015153:Blotting, Western; D045744:Cell Line, Tumor; D015972:Gene Expression Regulation, Neoplastic; D055785:Gene Knockdown Techniques; D057809:HEK293 Cells; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D051059:PTEN Phosphohydrolase / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D011401:Promoter Regions, Genetic; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism*; D012334:RNA, Neoplasm / Q000737:chemistry / Q000235:genetics; D034741:RNA, Small Interfering / Q000008:administration & dosage / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors / Q000096:biosynthesis* / Q000235:genetics
D012334:RNA, Neoplasm; D034741:RNA, Small Interfering; C000604407:SNAI1 protein, human; C000604449:Snai2 protein, mouse; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human
PTEN; cell growth; prostate cancer; slug; tumor suppressor