Korean J Urol.  2015 Sep;56(9):656-665. 10.4111/kju.2015.56.9.656.

Effect of curcumin on the interaction between androgen receptor and Wnt/beta-catenin in LNCaP xenografts

• Hong JH
• Lee G
• Choi HY

• KMID: 2344105
• DOI: http://doi.org/10.4111/kju.2015.56.9.656

Abstract

PURPOSE
Curcumin is a nontoxic, chemopreventive agent possessing multifaceted functions. Our previous study showed that curcumin inhibits androgen receptor (AR) through modulation of Wnt/beta-catenin signaling in LNCaP cells. Therefore, we investigated the in vivo effects of curcumin by using LNCaP xenografts.
MATERIALS AND METHODS
LNCaP cells were subcutaneously inoculated in Balb/c nude mice. When the tumor volume reached greater than 100 mm3, either curcumin (500 mg/kg body weight) or vehicle was administered through oral gavage three times weekly for 4 weeks. The expression of AR and intermediate products of Wnt/beta-catenin were assessed.
RESULTS
Curcumin had an inhibitory effect on tumor growth during the early period, which was followed by a slow increase in growth over time. Tumor growth was delayed about 27% in the curcumin group. The mean prostate-specific antigen (PSA) doubling time in the curcumin group was approximately twice that in the untreated group. Curcumin significantly decreased AR expression at both the mRNA and protein level. The PSA levels tended to be reduced in the curcumin group. However, there were no significant changes in expression of Wnt/beta-catenin pathway intermediates.
CONCLUSIONS
This study revealed that curcumin initially interferes with prostate cancer growth by inhibiting AR activity and possibly by reducing PSA expression. Further research is needed to investigate the plausible mechanism of the antiandrogenic action of curcumin.

Keyword

Androgen receptors; Animal models; Curcumin; Prostate neoplasms

MeSH Terms

Adenocarcinoma/drug therapy/*metabolism
Animals
Antineoplastic Agents/*pharmacology
Curcumin/*pharmacology
Cyclin D1/genetics/metabolism
Heterografts
Humans
Male
Mice, Inbred BALB C
Prostate-Specific Antigen/blood/genetics
Prostatic Neoplasms/drug therapy/*metabolism
RNA, Messenger/*metabolism
Receptors, Androgen/genetics/*metabolism
Wnt Signaling Pathway/*drug effects
beta Catenin/genetics/metabolism
Antineoplastic Agents
beta Catenin
Curcumin
Cyclin D1
RNA, Messenger
Receptors, Androgen
Prostate-Specific Antigen

Figure

• 

  Fig. 1 The effect of curcumin on the tumor growth of LNCaP xenografts. (A) Each line represents the tumor growth over time for an individual mouse. (B) The curcumin-treated mice had a tendency to exhibit slow tumor growth during the initial treatment period. *p<0.05 compared with the tumor volume at week 7. Data are plotted as median±95% confidence interval. (C) The average tumor weights at the time of tumor harvest. Values are expressed as box and whisker plots. The solid line and cross mark inside the rectangle indicate the median and the mean of the sample distribution, respectively. (D) Established tumor growth in the LNCaP cell-derived xenograft model.

• 

  Fig. 2 Effect of curcumin on the expression of prostate-specific antigen (PSA). (A) PSA activity was determined by enzyme-linked immunosorbent assay. Values are shown as the mean±standard error of the mean for all samples in each group. (B) Calculation of PSA doubling time (DT). The solid line and cross mark inside the rectangle indicate the median and the mean of the sample distribution, respectively. The average PSA DT in the curcumin group was roughly twice that in the control group, although the difference was not statistically significant (p=0.150).

• 

  Fig. 3 Quantitative real-time polymerase chain reaction (qRT-PCR) for androgen receptor (AR), prostate-specific antigen (PSA), β-catenin, and cyclin D1. (A) The initial template quantities were plotted against the critical threshold values for the standards. A linear relationship was shown between the cycle threshold values and the corresponding cDNA levels of control plasmids. (B) Relative quantification data where the expression levels of treated samples are compared with a control sample after gene normalization. qRT-PCR results show that the mRNA expression of the AR was significantly decreased in the curcumin group. Results are shown as the mean±standard error of the mean for all samples in each group. *p<0.05 compared with the control group (p=0.011).

• 

  Fig. 4 Western blot analysis of androgen receptor (AR), β-catenin, and cyclin D1. The effect of curcumin on the expression of AR, β-catenin, and cyclin D1 proteins in the grown tumor tissues is shown. The curcumin group showed less AR expression than did the control group.

• 

  Fig. 5 Immunohistochemistry for androgen receptor (AR), prostate-specific antigen (PSA), β-catenin, and cyclin D1. (A) Tumor tissue sections were stained with antibodies against AR, PSA, β-catenin, and cyclin D1. Nuclei were counterstained (blue) with hematoxylin (×400 in each panel). (B) Positive immunohistochemical reactions are presented as the total staining intensity: no staining (0), low intensity (1), moderate intensity (2), and high intensity (3). Results are presented as the mean±standard error of the mean for all samples in each group.

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