The X-linked tumor suppressor TSPX downregulates cancer-drivers/oncogenes in prostate cancer in a C-terminal acidic domain dependent manner
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Tatsuo Kido1,2, Yunmin Li1,2, Yuichiro Tanaka3, Rajvir Dahiya3 and Yun-Fai Chris Lau1,2
1Division of Cell and Developmental Genetics, Department of Medicine, Veterans Affairs Medical Center, San Francisco, California, USA
2Institute for Human Genetics, University of California, San Francisco, California, USA
3Department of Urology, Veterans Affairs Medical Center, San Francisco and University of California San Francisco, San Francisco, California, USA
Yun-Fai Chris Lau, email: Chris.Lau@UCSF.edu
Keywords: prostate cancer; tumor suppressor; oncogene; transcriptome analyses; TCGA
Received: January 01, 2019 Accepted: January 31, 2019 Published: February 19, 2019
TSPX is a tumor suppressor gene located at Xp11.22, a prostate cancer susceptibility locus. It is ubiquitously expressed in most tissues but frequently downregulated in various cancers, including lung, brain, liver and prostate cancers. The C-terminal acidic domain (CAD) of TSPX is crucial for the tumor suppressor functions, such as inhibition of cyclin B/CDK1 phosphorylation and androgen receptor transactivation. Currently, the exact role of the TSPX CAD in transcriptional regulation of downstream genes is still uncertain. Using different variants of TSPX, we showed that overexpression of either TSPX, that harbors a CAD, or a CAD-truncated variant (TSPX[ΔC]) drastically retarded cell proliferation in a prostate cancer cell line LNCaP, but cell death was induced only by overexpression of TSPX. Transcriptome analyses showed that TSPX or TSPX[ΔC] overexpression downregulated multiple cancer-drivers/oncogenes, including MYC and MYB, in a CAD-dependent manner and upregulated various tumor suppressors in a CAD-independent manner. Datamining of transcriptomes of prostate cancer specimens in the Cancer Genome Atlas (TCGA) dataset confirmed the negative correlation between the expression level of TSPX and those of MYC and MYB in clinical prostate cancer, thereby supporting the hypothesis that the CAD of TSPX plays an important role in suppression of cancer-drivers/oncogenes in prostatic oncogenesis.
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