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Gamma-glutamyltransferase activity in exosomes as a potential marker for prostate cancer

Overview of attention for article published in BMC Cancer, May 2017
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Title
Gamma-glutamyltransferase activity in exosomes as a potential marker for prostate cancer
Published in
BMC Cancer, May 2017
DOI 10.1186/s12885-017-3301-x
Pubmed ID
Authors

Kyojiro Kawakami, Yasunori Fujita, Yoko Matsuda, Tomio Arai, Kengo Horie, Koji Kameyama, Taku Kato, Koichi Masunaga, Yutaka Kasuya, Masashi Tanaka, Kosuke Mizutani, Takashi Deguchi, Masafumi Ito

Abstract

Exosomes or extracellular vesicles have the potential as a diagnostic marker for various diseases including cancer. In order to identify novel exosomal markers for prostate cancer (PC), we performed proteomic analysis of exosomes isolated from PC cell lines and examined the usefulness of the marker in patients. Exosomes isolated by differential centrifugation from the culture medium of androgen-dependent LNCaP prostate cancer cell line and its sublines of partially androgen-independent C4, androgen-independent C4-2 and bone metastatic C4-2B were subjected to iTRAQ-based proteomic analysis. Exosomes were also isolated by immunocapture and separated by size exclusion chromatography and density gradient centrifugation. Protein expression was determined by Western blot analysis. GGT activity was measured using a fluorescent probe, γ-glutamyl hydroxymethyl rhodamine green (gGlu-HMRG). Immunohistochemical analysis of tissues was performed using anti-GGT1 antibody. Among proteins upregulated in C4-2 and C4-2B cells than in LNCaP cells, we focused on gamma-glutamyltransferase 1 (GGT1), a cell-surface enzyme that regulates the catabolism of extracellular glutathione. The levels of both GGT1 large and small subunits were elevated in exosomes isolated from C4-2 and C4-2B cells by differential centrifugation and by immunocapture with anti-CD9 or -prostate-specific membrane antigen (PSMA) antibody. In cell lysates and exosomes, GGT1 expression correlated with GGT activity. Size exclusion chromatography of human serum demonstrated the presence of GGT activity and GGT1 subunits in fractions positive for CD9. Density gradient centrifugation revealed the co-presence of GGT1 subunits with CD9 in exosomes isolated by differential centrifugation from human serum. Since GGT activity correlated with GGT1 expression in serum exosomes isolated by differential centrifugation, we measured serum exosomal GGT activity in patients. Unexpectedly, we found that serum exosomal GGT activity was significantly higher in PC patients than in benign prostatic hyperplasia (BPH) patients. In support of this finding, immunohistochemical analysis showed increased GGT1 expression in PC tissues compared with BPH tissues. Our results suggest that serum exosomal GGT activity could be a useful biomarker for PC.

Mendeley readers

Mendeley readers

The data shown below were compiled from readership statistics for 88 Mendeley readers of this research output. Click here to see the associated Mendeley record.

Geographical breakdown

Country Count As %
United States 1 1%
Unknown 87 99%

Demographic breakdown

Readers by professional status Count As %
Student > Ph. D. Student 21 24%
Researcher 8 9%
Student > Master 8 9%
Student > Bachelor 7 8%
Student > Doctoral Student 6 7%
Other 16 18%
Unknown 22 25%
Readers by discipline Count As %
Biochemistry, Genetics and Molecular Biology 21 24%
Medicine and Dentistry 16 18%
Agricultural and Biological Sciences 7 8%
Chemistry 5 6%
Immunology and Microbiology 2 2%
Other 12 14%
Unknown 25 28%
Attention Score in Context

Attention Score in Context

This research output has an Altmetric Attention Score of 1. This is our high-level measure of the quality and quantity of online attention that it has received. This Attention Score, as well as the ranking and number of research outputs shown below, was calculated when the research output was last mentioned on 10 May 2017.
All research outputs
#20,420,242
of 22,971,207 outputs
Outputs from BMC Cancer
#6,523
of 8,345 outputs
Outputs of similar age
#270,440
of 310,732 outputs
Outputs of similar age from BMC Cancer
#109
of 138 outputs
Altmetric has tracked 22,971,207 research outputs across all sources so far. This one is in the 1st percentile – i.e., 1% of other outputs scored the same or lower than it.
So far Altmetric has tracked 8,345 research outputs from this source. They receive a mean Attention Score of 4.3. This one is in the 1st percentile – i.e., 1% of its peers scored the same or lower than it.
Older research outputs will score higher simply because they've had more time to accumulate mentions. To account for age we can compare this Altmetric Attention Score to the 310,732 tracked outputs that were published within six weeks on either side of this one in any source. This one is in the 1st percentile – i.e., 1% of its contemporaries scored the same or lower than it.
We're also able to compare this research output to 138 others from the same source and published within six weeks on either side of this one. This one is in the 1st percentile – i.e., 1% of its contemporaries scored the same or lower than it.