Plasma-Derived Exosomal Survivin, a Plausible Biomarker for Early Detection of Prostate Cancer

<div><h3>Background</h3><p>Survivin is expressed in prostate cancer (PCa), and its downregulation sensitizes PCa cells to chemotherapeutic agents <em>in vitro</em> and <em>in vivo</em>. Small membrane-bound vesicles called exosomes, secreted from the endosomal membrane compartment, contain RNA and protein that they readily transport via exosome internalization into recipient cells. Recent progress has shown that tumor-derived exosomes play multiple roles in tumor growth and metastasis and may produce these functions via immune escape, tumor invasion and angiogenesis. Furthermore, exosome analysis may provide novel biomarkers to diagnose or monitor PCa treatment.</p> <h3>Methods</h3><p>Exosomes were purified from the plasma and serum from 39 PCa patients, 20 BPH patients, 8 prostate cancer recurrent and 16 healthy controls using ultracentrifugation and their quantities and qualities were quantified and visualized from both the plasma and the purified exosomes using ELISA and Western blotting, respectively.</p> <h3>Results</h3><p>Survivin was significantly increased in the tumor-derived samples, compared to those from BPH and controls with virtually no difference in the quantity of Survivin detected in exosomes collected from newly diagnosed patients exhibiting low (six) or high (nine) Gleason scores. Exosome Survivin levels were also higher in patients that had relapsed on chemotherapy compared to controls.</p> <h3>Conclusions</h3><p>These studies demonstrate that Survivin exists in plasma exosomes from both normal, BPH and PCa subjects. The relative amounts of exosomal Survivin in PCa plasma was significantly higher than in those with pre-inflammatory BPH and control plasma. This differential expression of exosomal Survivin was seen with both newly diagnosed and advanced PCa subjects with high or low-grade cancers. Analysis of plasma exosomal Survivin levels may offer a convenient tool for diagnosing or monitoring PCa and may, as it is elevated in low as well as high Gleason scored samples, be used for early detection.</p> </div

Western Blot Analysis of exosomal Survivin in normal control, BPH and untreated PCa serum samples.

<p><b>A</b>. Antibodies for Survivin and Lamp1 were used for Western blotting of patient-purified exosomal protein. <b>B</b>. Proportion analysis of Survivin density to Lamp1 density were shown in both BPH and PCa with normal healthy controls (**, p<0.05, ***, p<0.001; statistically significant) with no significance recorded between normal controls and BPH.</p

Survivin ELISA and PSA levels of Sera from Prostate Cancer patients.

*<p>Clinical PSA Values.</p

Survivin ELISA and PSA levels of plasma from controls with no diagnosis of cancer.

<p>Survivin ELISA and PSA levels of plasma from controls with no diagnosis of cancer.</p

Quantification of Survivin levels in PCa plasma (A) and serum (B) samples by ELISA.

<p><b>A</b>. Survivin levels were measured in plasma derived from Gleason 6 (n = 10), Gleason 9 (n = 10), and Taxotere-resistant subjects (n = 8). <b>B</b>. Survivin levels were measured in serum derived from BPH (n = 20), and PCa (n = 19). Comparisons were accomplished using MANOVA with normal healthy controls (n = 10 and 6 respectively). (**, p<0.05, ***, p<0.001; statistically significant).</p

Survivin ELISA and PSA levels of Sera from BPH patients are shown.

<p>Survivin ELISA and PSA levels of Sera from BPH patients are shown.</p

Exosomal contents in PCa patients plasma (A) and serum (B) samples by using the acetylcholinesterase activity assay.

<p><b>A</b>. Exosome levels were measured in plasma derived from Gleason 6 (n = 10), Gleason 9 (n = 10), and Taxotere-resistant subjects (n = 8). <b>B</b>. Exosome levels were measured in serum derived from BPH (n = 20), and PCa (n = 19). Comparisons were accomplished using MANOVA with normal healthy controls (n = 10 and 6 respectively). (**, p<0.05, ***, p<0.001; statistically significant).</p

Western Blot Analysis of exosomal Survivin and Lamp1 in Taxotere-resistant PCa patients.

<p><b>A</b>. Survivin and Lamp1 antibodies were shown positive. <b>B</b>. Densitometric analysis of Survivin/Lamp1 expression in a healthy control (normal) and chemoresistance (CR) cases (**, p<0.05, statistically significant).</p

Survivin ELISA and PSA levels of plasma from Chemo-resistance, Gleason 6, and Gleason 9 patients are shown.

<p> <b>N/A: Not available.</b></p>*<p> <b>Clinical PSA values.</b></p