Purpose: Development of prostate cancer prevention strategies is an important priority to overcome high incidence, morbidity, and mortality. Recently, we showed that Nexrutine, an herbal extract, inhibits prostate cancer cell proliferation through modulation of Akt and cAMP-responsive element binding protein (CREB)–mediated signaling pathways. However, it is unknown if Nexrutine can be developed as a dietary supplement for the prevention of prostate cancer. In this study, we used the transgenic adenocarcinoma of mouse prostate (TRAMP) model to examine the ability of Nexrutine to protect TRAMP mice from developing prostate cancer. Experimental Design: Eight-week-old TRAMP mice were fed with pelleted diet containing 300 and 600 mg/kg Nexrutine for 20 weeks. Efficacy of Nexrutine was evaluated by magnetic resonance imaging at 18 and 28 weeks of progression and histologic analysis of prostate tumor or tissue at the termination of the experiment. Tumor tissue was analyzed for modulation of various signaling molecules. Results: We show that Nexrutine significantly suppressed palpable tumors and progression of cancer in the TRAMP model. Expression of total and phosphorylated Akt, CREB, and cyclin D1 was significantly reduced in prostate tissue from Nexrutine intervention group compared with tumors from control animals. Nexrutine also inhibited cyclin D1 transcriptional activity in androgen-independent PC-3 cells. Overexpression of kinase dead Akt mutant or phosphorylation-defective CREB inhibited cyclin D1 transcriptional activity. Conclusions: The current study shows that Nexrutine-mediated targeting of Akt/CREB–induced activation of cyclin D1 prevents the progression of prostate cancer. Expression of CREB and phosphorylated CREB increased in human prostate tumors compared with normal tissue, suggesting their potential use as prognostic markers.

Purpose: Near equal rates of incidence and mortality emphasize the need for novel targeted approaches for better management of patients with pancreatic cancer. Inflammatory molecules NF-κB and STAT3 are overexpressed in pancreatic tumors. Inhibition of one protein allows cancer cells to survive using the other. The goal of this study is to determine whether targeting STAT3/NF-κB crosstalk with a natural product Nexrutine can inhibit inflammatory signaling in pancreatic cancer. Experimental Design: HPNE, HPNE-Ras, BxPC3, Capan-2, MIA PaCa-2, and AsPC-1 cells were tested for growth, apoptosis, cyclooxygenase-2 (COX-2), NF-κB, and STAT3 level in response to Nexrutine treatment. Transient expression, gel shift, chromatin immunoprecipitation assay was used to examine transcriptional regulation of COX-2. STAT3 knockdown was used to decipher STAT3/NF-κB crosstalk. Histopathologic and immunoblotting evaluation was performed on BK5–COX-2 transgenic mice treated with Nexrutine. In vivo expression of prostaglandin receptor E-prostanoid 4 (EP4) was analyzed in a retrospective cohort of pancreatic tumors using a tissue microarray. Results: Nexrutine treatment inhibited growth of pancreatic cancer cells through induction of apoptosis. Reduced levels and activity of STAT3, NF-κB, and their crosstalk led to transcriptional suppression of COX-2 and subsequent decreased levels of prostaglandin E2 (PGE2) and PGF2. STAT3 knockdown studies suggest STAT3 as negative regulator of NF-κB activation. Nexrutine intervention reduced the levels of NF-κB, STAT3, and fibrosis in vivo. Expression of prostaglandin receptor EP4 that is known to play a role in fibrosis was significantly elevated in human pancreatic tumors. Conclusions: Dual inhibition of STAT3–NF-κB by Nexrutine may overcome problems associated with inhibition of either pathway. Clin Cancer Res; 20(5); 1259–73. ©2014 AACR.

SIRT1 (mammalian ortholog of the yeast silent information regulator 2) is a NAD-dependent histone deacetylase belonging to the multigene family of sirtuins. Anecdotal and epidemiologic observations provide evidence for beneficial effects of the calorie restriction mimetic resveratrol (RES), a SIRT1 activator in preventing cardiovascular diseases and cancer. Although SIRT1 possesses both tumorigenic and antitumorigenic potential, the molecular mechanisms underlying SIRT1-mediated tumor progression or inhibition are poorly understood. In this study, we investigated the role of SIRT1 in multiple human prostate cancer cell lines and prostate-specific PTEN knockout mouse model using resveratrol. Androgen-independent prostate cancer cell lines (C42B, PC3, and DU145) express higher levels of SIRT1 than androgen-responsive (LNCaP) and nontumorigenic prostate cells (RWPE-1). Resveratrol enhanced this expression without any significant effect on SIRT1 enzymatic activity. Inhibition of SIRT1 expression using shRNA enhanced cell proliferation and inhibited autophagy by repressing phosphorylation of S6K and 4E-BP1. These biologic correlates were reversed in the presence of resveratrol. Analysis of prostates from dietary intervention with resveratrol showed a significant reduction in prostate weight and reduction in the incidence of high-grade prostatic intraepithelial neoplastic (HGPIN) lesions by approximately 54% with no significant change in body weight. Consistent with the in vitro findings, resveratrol intervention in the PTEN knockout mouse model was associated with reduction in the prostatic levels of mTOR complex 1 (mTORC1) activity and increased expression of SIRT1. These data suggest that SIRT1/S6K-mediated inhibition of autophagy drives prostate tumorigenesis. Therefore, modulation of SIRT1/S6K signaling represents an effective strategy for prostate cancer prevention. Cancer Prev Res; 6(1); 27–39. ©2012 AACR.

Reciprocal interaction between pancreatic stellate cells (PSCs) and cancer cells (PCCs) in the tumor microenvironment (TME) promotes tumor cell survival and progression to lethal, therapeutically resistant pancreatic cancer. The goal of this study was to test the ability of Palmatine (PMT) to disrupt this reciprocal interaction in vitro and examine the underlying mechanism of interaction. We show that PSCs secrete glutamine into the extracellular environment under nutrient deprivation. PMT suppresses glutamine-mediated changes in GLI signaling in PCCs resulting in the inhibition of growth and migration while inducing apoptosis by inhibition of survivin. PMT-mediated inhibition of (glioma-associated oncogene 1) GLI activity in stellate cells leads to suppression (collagen type 1 alpha 1) COL1A1 activation. Remarkably, PMT potentiated gemcitabine's growth inhibitory activity in PSCs, PCCs and inherently gemcitabine-resistant pancreatic cancer cells. This is the first study that shows the ability of PMT to inhibit growth of PSCs and PCCs either alone or in combination with gemcitabine. These studies warrant additional investigations using preclinical models to develop PMT as an agent for clinical management of pancreatic cancer.

Evidence from epidemiological studies suggests that plant-based diets can reduce the risk of prostate cancer. However, very little information is available concerning the use of botanicals in preventing prostate cancer. As a first step toward developing botanicals as prostate cancer preventives, we examined the effect of Nexrutine on human prostate cancer cells. Nexrutine is a herbal extract developed from Phellodendron amurense. Phellodendron extracts have been used traditionally in Chinese medicine for hundreds of years as an antidiarrheal, astringent, and anti-inflammatory agent. The present study investigated its potential antitumor effect on human prostate cancer cells. Our results suggest that it inhibits tumor cell proliferation through apoptosis induction and inhibition of cell survival signaling. The results of the present study indicate that Nexrutine treatment 1) inhibits the proliferation of both androgen-responsive and androgen-independent human prostate cancer cells through induction of apoptosis; 2) reduces levels of pAkt, phosphorylated cAMP response-binding protein (pCREB) and CREB DNA-binding activity; and 3) induces apoptosis in prostate cancer cells stably overexpressing Bcl-2. Further, Akt kinase activity was reduced in cells treated with Nexrutine, and ectopic expression of myristoylated Akt protected from Nexrutine induced inhibition of proliferation, implicating a role for Akt signaling.