Expression levels of heat shock protein 27 and cellular FLICE-like inhibitory protein in prostate cancer correlate with Gleason score sum and pathologic stage

Purpose

Heat shock protein (HSP) 27 protects the cell by controlling apoptosis and immune reactions, and c-FLIP (cellular-FLICE inhibitory protein) inhibits apoptosis by inhibiting caspase-8 activity. We investigated the relationship of HSP27 and c-FLIP expression to prostate-specific antigen, Gleason score sum (GSS), and pathologic stage.

Materials and Methods

Samples from 163 patients between May 2004 and April 2010 were analyzed: 83 from patients that had underwent a radical prostatectomy, and 80 from those that underwent transurethral resection of the prostate to alleviate urinary symptoms from benign prostate hyperplasia. c-FLIP and HSP27 expression were observed by immunohistochemistry staining. Samples with less than 5% expression-positive cells were scored as 1, with 5%-50% were scored as 2, and with more than 50% were scored as 3. Local reactions were identified as 0.5 and evaluated.

Results

Both the presence of HSP27 within the tumor and the number of cancer cells positive for HSP27 were significantly correlated to GSS and pathologic stage (p<0.001, p=0.001, p<0.001, p<0.001). The same was true for c-FLIP expression (p<0.001). GSS was more highly correlated to HSP27 expression than to c-FLIP expression (r=0.814 for HSP27, r=0.776 for c-FLIP), as was pathologic stage (r=0.592 for HSP27, r=0.554 for c-FLIP).

Conclusions

In prostate cancer, higher GSS and a more advanced pathologic stage were associated with a higher likelihood of having a HSP27-positive tumor and more HSP27-positive tumor cells. HSP27 expression was correlated with GSS and prostate cancer stage. A more advanced pathologic stage corresponded to a higher likelihood of having a c-FLIP-positive tumor and more c-FLIP-positive tumor cells. HSP27 expression had a higher correlation with prostate cancer stage and GSS than c-FLIP expression did.

Dual silencing of Hsp27 and c-FLIP enhances doxazosin-induced apoptosis in PC-3 prostate cancer cells

We evaluated effect of dual gene silencing of Hsp27 and c-FLIP in doxazosin-induced apoptosis of PC-3 cell. After transfection using Hsp27 and c-FLIP siRNA mixture (dual silencing), doxazosin treatment was done at the concentrations of 1, 10, and 25 μM. We checked apoptosis of PC-3 cells with and TUNEL staining. We also checked interaction between Hsp27 and C-FLIP in the process of apoptosis inhibition. Spontaneous apoptotic index was 5% under single gene silencing of Hsp27 and c-FLIP and 7% under dual silencing of Hsp27 and c-FLIP. When doxazosin treatment was added, apoptotic indices increased in a dose-dependent manner (1, 10, and 25 μM): nonsilencing 10, 27, and 52%; Hsp27-silencing: 14, 35, and 68%; c-FLIP silencing: 21, 46, and 78%; dual silencing: 38, 76, and 92%. While c-FLIP gene expression decreased in Hsp27- silenced cells, Hsp27 gene expression showed markedly decreased pattern in the cells of c-FLIP silencing. The knockout of c-FLIP and Hsp27 genes together enhances apoptosis even under 1 μM, rather than low concentration, of doxazosin in PC-3 cells. This finding suggests a new strategy of multiple knockout of antiapoptotic and survival factors in the treatment of late-stage prostate cancer refractory to conventional therapy.

Inhibition of androgen receptor expression with small interfering RNA enhances cancer cell apoptosis by suppressing survival factors in androgen insensitive, late stage LNCaP cells

Introduction.The aim was to evaluate the changes of androgen receptor (AR) expression quantitatively and to identify influence of AR on cancer related survival markers in LNCap cell line. Materials and Methods. We compared expressions of AR, heat shock protein 27 (HSP27), clusterin (CLU), glucose-related protein 78 (GRP78), and cellular FLICE-like inhibitory protein (c-FLIP) and their genes between es-LNCaP (less than 33 times subcultured, L-33), ls-LNCaP (over 81 times subcultured, H-81), and si-LNCaP (AR siRNA transfected ls-LNCaP) by Western blotting and RT-PCR. Results. The expressions of AR, HSP27, CLU, GRP78, and c-FLIP were increased in ls-LNCaP compared with es-LNCaP (AR, 157%; HSP27, 132%; CLU, 146%; GRP78, 138%; c-FLIP, 152%). However, in si-LNCaP cell line, protein expressions were reversed to the level of es-LNCaP cell lines (25, 102, 109, 98, and 101%), and gene expressions on real-time PCR were also reversed to the expression level of es-LNCaP (ls-LNCaP: 179, 156, 133, 123, and 167%; si-LNCaP: 22, 93, 103, 112, and 107%). Conclusions. This finding suggests that androgen receptor can be related to the increased expression of cancer related survival markers such as HSP27, GRP78, CLU, and c-FLIP in late stage prostate cancer, and also inhibition of AR gene can be a therapeutic target in this stage of cancer.