Roble Bedolla

Phosphorylation of Akt (Ser473) is an Excellent Predictor of Poor Clinical Outcome in Prostate Cancer

We previously showed, by immunohistochemistry with phospho-specific antibodies, increased phosphorylation (activation) of Akt (Ser473) [phosphorylated Akt (pAkt)] in high-Gleason grade prostate cancer (Malik SN, et al., Clin Cancer Res 2002;8:1168–71). Elevation of pAkt was accompanied by decreased phosphorylation of extracellular signal-regulated kinase (ERK) 1/2 (Thr202/Tyr204) [phosphorylated ERK (pERK)], indicative of inactivation. In this report, we determined whether increased pAkt and decreased pERK predicted clinical outcome. Prostate-specific antigen (PSA) failure (detectable and rising PSA) versus PSA non-failure (undetectable PSA 5 years after prostatectomy) was used as a surrogate for clinical outcome. Prostate tumors from cases of PSA failure versus non-failure were stained for pAkt and pERK. A significant increase in mean pAkt staining (P < 0.001) in the PSA failures versus non-failures was seen based on the Wilcoxon signed ranks test [222.18 ± 33.9 (n = 37) versus 108.79 ± 104.57 (n = 16)]. Using the best-fitting multiple logistic regression equation, a 100-point increase in pAkt staining resulted in a 160% increase in the odds of being a PSA failure. There was decreased staining for pERK in PSA failures versus non-failures: a 100-point decrease resulted in an 80% increase in the odds of being a PSA failure. Each of these effects assumed the other biomarker was held constant. The area under the receiver-operating characteristic curve for these two biomarkers predicting PSA failure was 0.84, indicating excellent discrimination between PSA failure and non-failure cases. These data indicate that increased pAkt, alone or together with decreased pERK, is an important predictor of probability of PSA failure. However, pERK alone was not a significant predictor of PSA failure.

Determining Risk of Biochemical Recurrence in Prostate Cancer by Immunohistochemical Detection of PTEN Expression and Akt Activation

Purpose: A considerable fraction of patients who undergo radical prostatectomy as treatment for primary prostate cancer experience biochemical recurrence detected by elevated serum levels of prostate-specific antigen. In this study, we investigate whether loss of expression of the tumor suppressor phosphatase and tensin homologue deleted on chromosome 10 (PTEN) and the phosphorylated form of the cell survival protein Akt (pAkt) predicts biochemical recurrence. Experimental Design: Expression of PTEN and pAkt was detected by immunohistochemistry in paraffin-embedded prostate cancer tissue obtained from men undergoing radical prostatectomy. Outcome was determined by 60-month follow-up determining serum prostate-specific antigen levels. Results: By itself, PTEN was not a good predictor of biochemical recurrence; however, in combination with pAkt, it was a better predictor of the risk of biochemical recurrence compared with pAkt alone. Ninety percent of all cases with high pAkt and negative PTEN were recurrent whereas 88.2% of those with low pAkt and positive PTEN were nonrecurrent. In addition, high Gleason scores resulted in reduced protection from decreased pAkt and increased PTEN. By univariate logistic regression, pAkt alone gives an area under the receiver-operator characteristic curve of 0.82 whereas the area under the receiver-operator characteristic curve for the combination of PTEN, pAkt, and Gleason based on a stepwise selection model is 0.89, indicating excellent discrimination. Conclusions: Our results indicate that loss of PTEN expression, together with increased Akt phosphorylation and Gleason score, is of significant predictive value for determining, at the time of prostatectomy, the risk of biochemical recurrence.

Reactive oxygen species hydrogen peroxide mediates Kaposi's sarcoma-associated herpesvirus reactivation from latency.

Kaposis sarcoma-associated herpesvirus (KSHV) establishes a latent infection in the host following an acute infection. Reactivation from latency contributes to the development of KSHV-induced malignancies, which include Kaposis sarcoma (KS), the most common cancer in untreated AIDS patients, primary effusion lymphoma and multicentric Castlemans disease. However, the physiological cues that trigger KSHV reactivation remain unclear. Here, we show that the reactive oxygen species (ROS) hydrogen peroxide (H2O2) induces KSHV reactivation from latency through both autocrine and paracrine signaling. Furthermore, KSHV spontaneous lytic replication, and KSHV reactivation from latency induced by oxidative stress, hypoxia, and proinflammatory and proangiogenic cytokines are mediated by H2O2. Mechanistically, H2O2 induction of KSHV reactivation depends on the activation of mitogen-activated protein kinase ERK1/2, JNK, and p38 pathways. Significantly, H2O2 scavengers N-acetyl-L-cysteine (NAC), catalase and glutathione inhibit KSHV lytic replication in culture. In a mouse model of KSHV-induced lymphoma, NAC effectively inhibits KSHV lytic replication and significantly prolongs the lifespan of the mice. These results directly relate KSHV reactivation to oxidative stress and inflammation, which are physiological hallmarks of KS patients. The discovery of this novel mechanism of KSHV reactivation indicates that antioxidants and anti-inflammation drugs could be promising preventive and therapeutic agents for effectively targeting KSHV replication and KSHV-related malignancies.

Nuclear versus cytoplasmic localization of filamin A in prostate cancer: immunohistochemical correlation with metastases.

Purpose: We previously showed that nuclear localization of the actin-binding protein, filamin A (FlnA), corresponded to hormone-dependence in prostate cancer. Intact FlnA (280 kDa, cytoplasmic) cleaved to a 90 kDa fragment which translocated to the nucleus in hormone-naïve cells, whereas in hormone-refractory cells, FlnA was phosphorylated, preventing its cleavage and nuclear translocation. We have examined whether FlnA localization determines a propensity to metastasis in advanced androgen-independent prostate cancer. Experimental Design: We examined, by immunohistochemistry, FlnA localization in paraffin-embedded human prostate tissue representing different stages of progression. Results were correlated with in vitro studies in a cell model of prostate cancer. Results: Nuclear FlnA was significantly higher in benign prostate (0.6612 ± 0.5888), prostatic intraepithelial neoplasia (PIN; 0.6024 ± 0.4620), and clinically localized cancers (0.69134 ± 0.5686) compared with metastatic prostate cancers (0.3719 ± 0.4992, P = 0.0007). Cytoplasmic FlnA increased from benign prostate (0.0833 ± 0.2677), PIN (0.1409 ± 0.2293), localized cancers (0.3008 ± 0.3762, P = 0.0150), to metastases (0.7632 ± 0.4414, P < 0.00001). Logistic regression of metastatic versus nonmetastatic tissue yielded the area under the receiver operating curve as 0.67 for nuclear-FlnA, 0.79 for cytoplasmic-FlnA, and 0.82 for both, indicating that metastasis correlates with cytoplasmic to nuclear translocation. In vitro studies showed that cytoplasmic localization of FlnA induced cell invasion whereas nuclear translocation of the protein inhibited it. FlnA dephosphorylation with the protein kinase A inhibitor H-89 facilitated FlnA nuclear translocation, resulting in decreased invasiveness and AR transcriptional activity, and induced sensitivity to androgen withdrawal in hormone-refractory cells. Conclusions: The data presented in this study indicate that in prostate cancer, metastasis correlates with cytoplasmic localization of FlnA and may be prevented by cleavage and subsequent nuclear translocation of this protein.

Akt in Prostate Cancer: Possible Role in Androgen-Independence

Akt, a downstream effector of phosphatidylinositol 3-kinase (PI3K), has often been implicated in prostate cancer. Studies in prostate tumor cell lines revealed that Akt activation is probably important for the progression of prostate cancer to an androgen-independent state. Investigations of human prostate cancer tissues show that although there is neither Akt gene amplification nor enhanced protein expression in prostate cancer compared to normal tissue, poorly differentiated tumors exhibit increased expression of a phosphorylated (activated) form of Akt compared to normal tissue, prostatic intraepithelial neoplasia (PIN) or well-differentiated prostate cancer. Akt phosphorylation is accompanied by the inactivation of ERK, a member of the mitogen activated protein kinase (MAPK) family. In this article, we postulate that Akt promotes androgen-independent survival of prostate tumor cells by modulating the expression and activation of the androgen receptor (AR).

KSHV MicroRNAs Mediate Cellular Transformation and Tumorigenesis by Redundantly Targeting Cell Growth and Survival Pathways

Kaposis sarcoma-associated herpesvirus (KSHV) is causally linked to several human cancers, including Kaposis sarcoma, primary effusion lymphoma and multicentric Castlemans disease, malignancies commonly found in HIV-infected patients. While KSHV encodes diverse functional products, its mechanism of oncogenesis remains unknown. In this study, we determined the roles KSHV microRNAs (miRs) in cellular transformation and tumorigenesis using a recently developed KSHV-induced cellular transformation system of primary rat mesenchymal precursor cells. A mutant with a cluster of 10 precursor miRs (pre-miRs) deleted failed to transform primary cells, and instead, caused cell cycle arrest and apoptosis. Remarkably, the oncogenicity of the mutant virus was fully restored by genetic complementation with the miR cluster or several individual pre-miRs, which rescued cell cycle progression and inhibited apoptosis in part by redundantly targeting IκBα and the NF-κB pathway. Genomic analysis identified common targets of KSHV miRs in diverse pathways with several cancer-related pathways preferentially targeted. These works define for the first time an essential viral determinant for KSHV-induced oncogenesis and identify NF-κB as a critical pathway targeted by the viral miRs. Our results illustrate a common theme of shared functions with hierarchical order among the KSHV miRs.

Direct and efficient cellular transformation of primary rat mesenchymal precursor cells by KSHV

Infections by viruses are associated with approximately 12% of human cancer. Kaposis sarcoma-associated herpesvirus (KSHV) is causally linked to several malignancies commonly found in AIDS patients. The mechanism of KSHV-induced oncogenesis remains elusive, due in part to the lack of an adequate experimental system for cellular transformation of primary cells. Here, we report efficient infection and cellular transformation of primary rat embryonic metanephric mesenchymal precursor cells (MM cells) by KSHV. Cellular transformation occurred at as early as day 4 after infection and in nearly all infected cells. Transformed cells expressed hallmark vascular endothelial, lymphatic endothelial, and mesenchymal markers and efficiently induced tumors in nude mice. KSHV established latent infection in MM cells, and lytic induction resulted in low levels of detectable infectious virions despite robust expression of lytic genes. Most KSHV-induced tumor cells were in a latent state, although a few showed heterogeneous expression of lytic genes. This efficient system for KSHV cellular transformation of primary cells might facilitate the study of growth deregulation mechanisms resulting from KSHV infections.

Dietary Resveratrol prevents development of high-grade prostatic intraepithelial neoplastic lesions: Involvement of SIRT1/S6K axis

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.

Combined Targeting of STAT3/NF-κB/COX-2/EP4 for Effective Management of Pancreatic Cancer

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.

Nrdp1-mediated regulation of ErbB3 expression by the androgen receptor in androgen-dependent but not castrate-resistant prostate cancer cells.

Patients with advanced prostate cancer (PCa) are initially susceptible to androgen withdrawal (AW), but ultimately develop resistance to this therapy (castration-resistant PCa, CRPC). Here, we show that AW can promote CRPC development by increasing the levels of the receptor tyrosine kinase ErbB3 in androgen-dependent PCa, resulting in AW-resistant cell cycle progression and increased androgen receptor (AR) transcriptional activity. CRPC cell lines and human PCa tissue overexpressed ErbB3, whereas downregulation of ErbB3 prevented CRPC cell growth. Investigation of the mechanism by which AW augments ErbB3, using normal prostate-derived pRNS-1-1 cells, and androgen-dependent PCa lines LNCaP, PC346C, and CWR22 mouse xenografts, revealed that the AR suppresses ErbB3 protein levels, whereas AW relieves this suppression, showing for the first time the negative regulation of ErbB3 by AR. We show that AR activation promotes ErbB3 degradation in androgen-dependent cells, and that this effect is mediated by AR-dependent transcriptional upregulation of neuregulin receptor degradation protein-1 (Nrdp1), an E3 ubiquitin ligase that targets ErbB3 for degradation but whose role in PCa has not been previously examined. Therefore, AW decreases Nrdp1 expression, promoting ErbB3 protein accumulation, and leading to AR-independent proliferation. However, in CRPC sublines of LNCaP and CWR22, which strongly overexpress the AR, ErbB3 levels remain elevated due to constitutive suppression of Nrdp1, which prevents AR regulation of Nrdp1. Our observations point to a model of CRPC development in which progression of PCa to castration resistance is associated with the inability of AR to transcriptionally regulate Nrdp1, and predict that inhibition of ErbB3 during AW may impair CRPC development.