Survivin is a potential mediator of prostate cancer metastasis

Abstract

Purpose: We examined whether Survivin expression is associated with an increased risk of metastasis in prostate cancer.

Methods and materials: A total of 205 patients with T1 (23%) and T2 (77%) prostate cancer were treated with conventional external beam radiation therapy from 1991 to 1993 at the Massachusetts General Hospital. Of the patients, 62 had adequate and suitable-stained tumor material for Survivin analysis. Median follow-up was 102 months (range, 5-127 months). Distant failure was determined on the basis of clinical criteria. In preclinical studies, replication-deficient adenovirus encoding phosphorylation-defective Survivin Thr34→Ala dominant-negative mutant pAd-S(T34A) or short hairpin RNA (shRNA) was used to inhibit Survivin in prostate cancer models, and the cell motility, morphology, and metastasis were investigated.

Results: Our correlative data on men with early-stage (T1/T2) prostate cancers treated at Massachusetts General Hospital by definitive radiotherapy indicated that overexpression of Survivin (positive staining in ≥10% cells) was associated with a significantly increased risk for the subsequent development of distant metastasis (p = 0.016) in the univariate analysis. In the multivariate analysis, overexpression of Survivin remained an independent predictor of distant metastasis (p = 0.008). The inhibition of Survivin dramatically inhibited invasiveness of prostate cancer cells in the in vitro invasion assay and spontaneous metastasis in the Dunning prostate cancer in vivo model. Furthermore, attenuation of Survivin resulted in changes in the microtubule cytoskeleton, loss of cellular polarity, and loss of motility.

Conclusions: This study suggests that Survivin may be a potentially important prognostic marker and promising therapeutic target in metastatic prostate cancer.

Fig. 1

(a) Representative stained slides showing Survivin strong immunostaining (left) and Survivin weak immunostaining (right). (b) Kaplan-Meier curve demonstrating that higher level of Survivin expression (≥10%) was associated with an increased risk of distant metastasis in men with T1/T2 prostate cancers treated by definitive radiotherapy at Massachusetts General Hospital.

Fig. 2

Matrigel invasion assay on DU-145, LNCaP and PC-3 cells infected with adenoviruses encoding pAd-(Empty), pAd-S(WT), or pAd-S(T34A). The invasion of cells infected with pAd-(Empty) was set as 1.

Fig. 3

Spontaneous metastasis assay in the Dunning prostate cancer model with intratumoral injection of adenoviruses encoding pAd-(Empty), pAd-S(WT), and pAd-S(T34A). (a) Representative lungs from different treatment arms. (b) Quantification of the meta-static lesions on the lungs. The metastasis in pAd-(Empty) treated arm was set as 1.

Fig. 4

(a) Western blot showing Survivin levels in AT6.3 cells transfected with nontargeting shRNA (Lane 1) and different Survivin shRNA constructs (Lanes 2–5). Nontargeting ShRNA (Lane 1) and one of the Survivin shRNA constructs (Lane 4) were used in subsequent studies. (b) Wound healing assay on AT6.3 cells transfected with nontargeting shRNA or Survivin shRNA. (c) Immunofluorescent staining of α-tubulin in AT6.3 cells transfected with nontargeting shRNA (left) or Survivin shRNA (right). Arrows indicate MTOCs in these cells.