Resveratrol and pterostilbene epigenetically restore PTEN expression by targeting oncomiRs of the miR-17 family in prostate cancer

Abstract

In recent years, not only has the role of miRNAs in cancer become increasingly clear but also their utilization as potential biomarkers and therapeutic targets has gained ground. Although the importance of dietary stilbenes such as resveratrol and pterostilbene as anti-cancer agents is well recognized, our understanding of their miRNA-targeting capabilities is still limited. In our previous study, we reported that resveratrol downregulates PTEN-targeting members of the oncogenic miR-17 family, which are overexpressed in prostate cancer. This study investigates the resveratrol and pterostilbene induced miRNA-mediated regulation of PTEN in prostate cancer. Here, we show that both compounds decrease the levels of endogenous as well as exogenously expressed miR-17, miR-20a and miR-106b thereby upregulating their target PTEN. Using functional luciferase reporter assays, we demonstrate that ectopically expressed miR-17, miR-20a and miR-106b directly target PTEN 3′UTR to reduce its expression, an effect rescued upon treatment with resveratrol and pterostilbene. Moreover, while stable lentiviral expression of miR-17/106a significantly decreased PTEN mRNA and protein levels and conferred survival advantage to the cells, resveratrol and more so pterostilbene was able to dramatically suppress these effects. Further, pterostilbene through downregulation of miR-17-5p and miR-106a-5p expression both in tumors and systemic circulation, rescued PTEN mRNA and protein levels leading to reduced tumor growth in vivo. Our findings implicate dietary stilbenes as an attractive miRNA-mediated chemopreventive and therapeutic strategy, and circulating miRNAs as potential chemopreventive and predictive biomarkers for clinical development in prostate cancer.

MTA1 drives malignant progression and bone metastasis in prostate cancer

“…Western blot analysis was carried out as described previously (Butt et al ., 2017; Dhar et al ., 2015a,b, 2016, 2017; Dias et al ., 2013a,b; Kai et al ., 2010, 2011; Li et al ., 2013). The antibodies used in this study are listed in Table S1.…”

“…qRT‐PCR was performed as described previously (Butt et al ., 2017; Dhar et al ., 2015a,b, 2016, 2017) on the LightCycler 480 II real‐time PCR instrument (Roche Diagnostics, Basel, Switzerland). All primers for qRT‐PCR are listed in Table S2.…”

“…For s.c. xenografts, mice were randomly divided into two groups ( n  = 5 per group), and PC3M‐Luc‐NS and PC3M‐Luc shMTA1 cells (0.5 × 10 6 ) in 100 μL of 50% Matrigel (Corning Life Sciences) were inoculated on the dorsal right flank of mice. Bioluminescent and caliper measurements were taken weekly as described previously (Dhar et al ., 2015a,b; Dias et al ., 2013a, b; Kai et al ., 2011; Li et al ., 2013). Calculation of tumor volume by digital vernier caliper measurements was made using formula as before (Dhar et al ., 2015b; Kai et al ., 2011).…”

“…Bioluminescent measurements were taken immediately and then weekly as described previously (Dhar et al ., 2015a,b; Dias et al ., 2013b; Kai et al ., 2011; Li et al ., 2013). The mice were sacrificed at day 34.…”

“…Immunohistochemical staining with Ki67, MTA1, CTSB, and E‐cad (antibodies are listed in Table S1) was performed as per the protocol described previously (Butt et al ., 2017; Dhar et al ., 2015a,b, 2016, 2017; Dias et al ., 2013a; Kai et al ., 2011; Li et al ., 2013). The Vectastain ABC Elite Kit and ImmPACT DAB Kit (Vector Laboratories, Burlingame, CA, USA) were used to visualize staining.…”