A reduction in Pten tumor suppressor activity promotes ErbB-2-induced mouse prostate adenocarcinoma formation through the activation of signaling cascades downstream of PDK1

Muscadine grape skin extract inhibits prostate cancer cells by inducing cell-cycle arrest, and decreasing migration through heat shock protein 40

Previously we demonstrated that muscadine grape skin extract (MSKE), a natural product, significantly inhibited androgen-responsive prostate cancer cell growth by inducing apoptosis through the targeting of survival pathways. However, the therapeutic effect of MSKE on more aggressive androgen-independent prostate cancer remains unknown. This study examined the effects of MSKE treatment in metastatic prostate cancer using complementary PC-3 cells and xenograft model. MSKE significantly inhibited PC-3 human prostate cancer cell tumor growth in vitro and in vivo. The growth-inhibitory effect of MSKE appeared to be through the induction of cell-cycle arrest. This induction was accompanied by a reduction in the protein expression of Hsp40 and cell-cycle regulation proteins, cyclin D1 and NF-kBp65. In addition, MSKE induced p21 expression independent of wild-type p53 induced protein expression. Moreover, we demonstrate that MSKE significantly inhibited cell migration in PC-3 prostate cancer cells. Overall, these results demonstrate that MSKE inhibits prostate tumor growth and migration, and induces cell-cycle arrest by targeting Hsp40 and proteins involved in cell-cycle regulation and proliferation. This suggests that MSKE may also be explored either as a neo-adjuvant or therapeutic for castration resistant prostate cancer.

Serine/Threonine Kinase 3-Phosphoinositide-Dependent Protein Kinase-1 (PDK1) as a Key Regulator of Cell Migration and Cancer Dissemination

Dissecting the cellular signaling that governs the motility of eukaryotic cells is one of the fundamental tasks of modern cell biology, not only because of the large number of physiological processes in which cell migration is crucial, but even more so because of the pathological ones, in particular tumor invasion and metastasis. Cell migration requires the coordination of at least four major processes: polarization of intracellular signaling, regulation of the actin cytoskeleton and membrane extension, focal adhesion and integrin signaling and contractile forces generation and rear retraction. Among the molecular components involved in the regulation of locomotion, the phosphatidylinositol-3-kinase (PI3K) pathway has been shown to exert fundamental role. A pivotal node of such pathway is represented by the serine/threonine kinase 3-phosphoinositide-dependent protein kinase-1 (PDPK1 or PDK1). PDK1, and the majority of its substrates, belong to the AGC family of kinases (related to cAMP-dependent protein kinase 1, cyclic Guanosine monophosphate-dependent protein kinase and protein kinase C), and control a plethora of cellular processes, downstream either to PI3K or to other pathways, such as RAS GTPase-MAPK (mitogen-activated protein kinase). Interestingly, PDK1 has been demonstrated to be crucial for the regulation of each step of cell migration, by activating several proteins such as protein kinase B/Akt (PKB/Akt), myotonic dystrophy-related CDC42-binding kinases alpha (MRCKα), Rho associated coiled-coil containing protein kinase 1 (ROCK1), phospholipase C gamma 1 (PLCγ1) and β3 integrin. Moreover, PDK1 regulates cancer cell invasion as well, thus representing a possible target to prevent cancer metastasis in human patients. The aim of this review is to summarize the various mechanisms by which PDK1 controls the cell migration process, from cell polarization to actin cytoskeleton and focal adhesion regulation, and finally, to discuss the evidence supporting a role for PDK1 in cancer cell invasion and dissemination.

miRNA-mRNA crosstalk in esophageal cancer: From diagnosis to therapy

The asymptomatic nature of esophageal cancer (EC) at early stages results in late clinical presentation leading to poor prognosis and limited success of therapeutic modalities. Efforts to identify diagnostic/prognostic markers have proven to be unsuccessful for translation into clinics. Hence, there is a pressing need for establishment of novel non-invasive biomarker for early diagnosis/better prognosis of EC. Recently, alteration in microRNA (miRNA) expression has emerged as an important hallmark of cancer. This review summarizes the differential expression of miRNAs in EC and addresses how their aberrant expression influences crucial biological processes such as apoptosis, cell proliferation, invasion and metastasis. Additionally, this review highlights the current status of circulating miRNA based diagnostic/prognostic markers. An effort has been made to find a connection between different miRNAs involved in EC and a detailed analysis has been done to screen out micoRNAs involved in prognosis and multidrug resistance. Further, investigation of these miRNAs would not only provide a gene therapy based strategy to prevent/treat cancer but also to reverse multidrug resistance leading to decreased requirement of harmful chemotherapeutic drugs.

Expression of 3-phosphoinositide-dependent protein kinase 1 in colorectal cancer as a potential therapeutic target

3-Phosphoinositide-dependent protein kinase 1 (PDK1) is centrally involved in cancer progression, including proliferation, apoptosis and invasion. However, its expression pattern and possible cellular functions in human colorectal cancer remain unclear. In the present study, we show that PDK1 expression is up-regulated at both mRNA and protein levels in colorectal cancer clinical specimens and cell lines. Transient knockdown of PDK1 suppresses cellular growth, induces cellular apoptosis and causes abnormal cell cycle distribution. Meanwhile, decreased PDK1 level is closely associated with reduced Akt/cyclin D1 activity. Activating AKT activity and reintroducing cyclin D1 expression significantly compromised the oncogenic activity induced by PDK1. Together, our findings elucidate a key role for PDK1 in colorectal cellular functions trigged by the Akt/cyclin D1 pathway, thus providing a novel insight of PDK1 in colorectal carcinogenesis.

Dysregulation of PTEN in cardiopulmonary vascular remodeling induced by pulmonary hypertension

Pulmonary hypertension (PH) is a disorder of lung vasculature characterized by arterial narrowing. Phosphatase-and-tensin homolog on chromosome 10 (PTEN), associated in the progression of multiple cancers, is implicated in arterial remodeling. However, the involvement of PTEN in PH remains unclear. The objective of the present study was to determine the role of PTEN in pulmonary vascular remodeling using established models of PH. The study used rat models of PH, induced by monocrotaline (MCT) administration (60 mg/kg) or continuous hypoxic exposure (10% oxygen) for 3 weeks. Pulmonary artery smooth muscle cells (SMCs) were used for in vitro confirmation. Development of PH was verified by hemodynamic, morphological and histopathology analyses. PTEN and key downstream proteins in pulmonary and cardiac tissues were analyzed by western blotting and RT-PCR. PTEN was significantly decreased (MCT, 53%; Hypoxia, 40%), pAkt was significantly increased (MCT, 42%; Hypoxia, 55%) in tissues of rats with PH. Similar results were observed in SMCs exposed to hypoxia (1% oxygen) for 48 h. Ubiquitination assay showed that PTEN degradation occurs via proteasomal degradation pathway. Western blotting demonstrated a significant downregulation of cell-cycle regulatory proteins p53 and p27, and upregulation of cyclin-D1 in the lungs of both models. The results showed that PTEN-mediated modulation of PI3K pathway was independent of the focal adhesion kinase and fatty acid synthase. The study, for the first time, established that PTEN plays a key role in the progression of pulmonary hypertension. The findings may have potential for the treatment of pulmonary hypertension using PTEN as a target.

The PDK1 master kinase is over-expressed in acute myeloid leukemia and promotes PKC-mediated survival of leukemic blasts

PDK1 is a master kinase that activates at least six protein kinase groups including AKT, PKC and S6K and is a potential target in the treatment of a range of malignancies. Here we show overexpression of PDK1 in over 40% of myelomonocytic acute leukemia patients. Overexpression of PDK1 occurred uniformly throughout the leukemic population, including putative leukemia-initiating cells. Clinical outcome analysis revealed PDK1 overexpression was associated with poorer treatment outcome. Primary acute myeloid leukemia blasts over-expressing PDK1 showed improved in vitro survival and ectopic expression of PDK1 promoted the survival of myeloid cell lines. Analysis of PDK1 target kinases revealed that PDK1 overexpression was most closely associated with increased phosphorylation of PKC isoenzymes and inhibition of PKC strongly inhibited the survival advantage of PDK1 over-expressing cells. Membrane localization studies implicated PKCα as a major target for PDK1 in this disease. PDK1 over-expressing blasts showed differential sensitivity to PDK1 inhibition (in the low micromolar range) suggesting oncogene addiction, whilst normal bone marrow progenitors were refractory to PDK1 inhibition at effective inhibitor concentrations. PDK1 inhibition also targeted subpopulations of leukemic blasts with a putative leukemia-initiating cell phenotype. Together these data show that overexpression of PDK1 is common in acute myelomonocytic leukemia and is associated with poorer treatment outcome, probably arising from the cytoprotective function of PDK1. We also show that therapeutic targeting of PDK1 has the potential to be both an effective and selective treatment for these patients, and is also compatible with current treatment regimes.

Multispectral Imaging

The field of anatomic pathology has changed significantly over the last decades and, as a result of the technological developments in molecular pathology and genetics, has had increasing pressures put on it to become quantitative and to provide more information about protein expression on a cellular level in tissue sections. Multispectral imaging (MSI) has a long history as an advanced imaging modality and has been used for over a decade now in pathology to improve quantitative accuracy, enable the analysis of multicolor immunohistochemistry, and drastically reduce the impact of contrast-robbing tissue autofluorescence common in formalin-fixed, paraffin-embedded tissues. When combined with advanced software for the automated segmentation of different tissue morphologies (eg, tumor vs stroma) and cellular and subcellular segmentation, MSI can enable the per-cell quantitation of many markers simultaneously. This article covers the role that MSI has played in anatomic pathology in the analysis of formalin-fixed, paraffin-embedded tissue sections, discusses the technological aspects of why MSI has been adopted, and provides a review of the literature of the application of MSI in anatomic pathology.

Vaccination with embryonic stem cells generates effective antitumor immunity against ovarian cancer

To date, only a few studies have suggested that human embryonic stem cells (hESCs) might effectively immunize against colon and lung cancer. The purpose of this study was to investigate the therapeutic potential of hESCs as a vaccine to induce widespread antitumor effects in different animal models and various types of cancer. C57BL/6 mice with ID8 ovarian cancer cell and Fischer 344 rats with NuTu-19 ovarian cancer cell models were used. Fifty-four mice were divided into six groups with nine mice in each group. Each mouse was immunized with pre-inactivated hESCs (H9) or mouse embryonic stem cells (mESCs; IVP-ES1) or ID8 or phosphate-buffered saline (PBS). Twenty-four rats were divided into four groups with six rats in each group, each rat immunized with pre-inactivated hESCs (H9) or NuTu-19 or PBS. After the vaccination, each mouse was challenged with live ID8 cells subcutaneously, and each rat was challenged with live NuTu-19 cells intraperitoneally. We discovered that vaccination of mice with the hESC line H9 and the mESC line IVP-ES1 generated consistent cellular and humoral immune responses against ID8 ovarian cancer. H9 and IVP-ES1 vaccinated mice obtained antitumor immune protection, and H9 vaccinated rats had the longest survival time and least distant metastases. No evidence of side-effects was observed. We also compared the immunogenicity against ovarian cancer between the hESC line, H9, and the mESC line, IVP-ES1, that derived from the inner cell mass in different species. We found that there were no significant differences between them. Furthermore, immunohistochemical staining revealed that several oncogenes and tumor suppressor genes, such as HER-2, C-myc, p53, and nm23, were expressed in H9, many of which were also shared by ovarian cancer. hESC vaccines can induce antitumor effects in two animal models and in ovarian cancer, indicating that the activity of the vaccine is universal, and, more importantly, it is safe.

Quantifying the CDK inhibitor VMY-1-103's activity and tissue levels in an in vivo tumor model by LC-MS/MS and by MRI

The development of new small molecule-based therapeutic drugs requires accurate quantification of drug bioavailability, biological activity and treatment efficacy. Rapidly measuring these endpoints is often hampered by the lack of efficient assay platforms with high sensitivity and specificity. Using an in vivo model system, we report a simple and sensitive liquid chromatography-tandem mass spectrometry assay to quantify the bioavailability of a recently developed novel cyclin-dependent kinase inhibitor VMY-1-103, a purvalanol B-based analog whose biological activity is enhanced via dansylation. We developed a rapid organic phase extraction technique and validated wide and functional VMY-1-103 distribution in various mouse tissues, consistent with its enhanced potency previously observed in a variety of human cancer cell lines. More importantly, in vivo MRI and single voxel proton MR-Spectroscopy further established that VMY-1-103 inhibited disease progression and affected key metabolites in a mouse model of hedgehog-driven medulloblastoma.

Epigenetic silencing of microRNA-375 regulates PDK1 expression in esophageal cancer

BACKGROUND

MicroRNAs (miRNAs) are a class of small (19-25 nucleotides) noncoding RNAs that regulate the expressions of a wide variety of genes, including some involved in cancer development. Some recent studies show that DNA methylation contributes to down-regulation of microRNA-375 (miR-375) during tumorigenesis. Whether or not down-regulation of miR-375 also exists in esophageal cancer is unknown.

AIM

Our aim was to test the hypothesis that down-regulation of miR-375 also exists in esophageal cancer.

METHODS

Expression of levels of miR-375 were examined using real-time PCR on paired esophageal cancer and adjacent non-cancerous tissues. The methylation status is detected by methylation specific-PCR (MSP).

RESULTS

The results show that miR-375 is downregulated by hypermethylation of the promoter in esophageal cancer tissues. Epigenetic silencing of miR-375 induced an up-regulation of its targets, 3-phosphoinositide-dependent protein kinase-1 (PDK1). Restoration of the miR-375 expression in esophageal cancer cell lines downregulated the PDK1 expression. Furthermore, the miR-375 expression was found to be inversely correlated with PDK1 expression in esophageal cancer.

CONCLUSION

Thus, miR-375 is frequently down-regulated in esophageal cancer and is a negative regulator of PDK1.

Animal models relevant to human prostate carcinogenesis underlining the critical implication of prostatic stem/progenitor cells

Recent development of animal models relevant to human prostate cancer (PC) etiopathogenesis has provided important information on the specific functions provided by key gene products altered during disease initiation and progression to locally invasive, metastatic and hormone-refractory stages. Especially, the characterization of transgenic mouse models has indicated that the inactivation of distinct tumor suppressor proteins such as phosphatase tensin homolog deleted on chromosome 10 (PTEN), Nkx3.1, p27(KIP1), p53 and retinoblastoma (pRb) may cooperate for the malignant transformation of prostatic stem/progenitor cells into PC stem/progenitor cells and tumor development and metastases. Moreover, the sustained activation of diverse oncogenic signaling elements, including epidermal growth factor receptor (EGFR), sonic hedgehog, Wnt/β-catenin, c-Myc, Akt and nuclear factor-kappaB (NF-κB) also may contribute to the acquisition of more aggressive and hormone-refractory phenotypes by PC stem/progenitor cells and their progenies during disease progression. Importantly, it has also been shown that an enrichment of PC stem/progenitor cells expressing stem cell-like markers may occur after androgen deprivation therapy and docetaxel treatment in the transgenic mouse models of PC suggesting the critical implication of these immature PC cells in treatment resistance, tumor re-growth and disease recurrence. Of clinical interest, the molecular targeting of distinct gene products altered in PC cells by using different dietary compounds has also been shown to counteract PC initiation and progression in animal models supporting their potential use as chemopreventive or chemotherapeutic agents for eradicating the total tumor cell mass, improving current anti-hormonal and chemotherapies and preventing disease relapse.

From man to mouse and back again: advances in defining tumor AKTivities in vivo

AKT hyperactivation is a common event in human cancers, and inhibition of oncogenic AKT activation is a major goal of drug discovery programs. Mouse tumor models that replicate AKT activation typical of human cancers provide a powerful means by which to investigate mechanisms of oncogenic signaling, identify potential therapeutic targets and determine treatment regimes with maximal therapeutic efficacy. This Perspective highlights recent advances using in vivo studies that reveal how AKT signaling supports tumor formation, cooperates with other mutations to promote tumor progression and facilitates tumor-cell dissemination, focusing on well-characterized prostate carcinoma mouse models that are highly sensitive to AKT activation. The implications of these findings on the therapeutic targeting of AKT and potential new drug targets are also explored.

PTEN loss accelerates KrasG12D-induced pancreatic cancer development

KRAS mutations are found in ∼90% of human pancreatic ductal adenocarcinomas (PDAC). However, mice genetically engineered to express Kras(G12D) from its endogenous locus develop PDACs only after a prolonged latency, indicating that other genetic events or pathway alterations are necessary for PDAC progression. The PTEN-controlled phosphatidylinositol 3-kinase (PI3K)/AKT signaling axis is dysregulated in later stages of PDAC. To better elucidate the role of PTEN/PI3K/AKT signaling in Kras(G12D)-induced PDAC development, we crossed Pten conditional knockout mice (Pten(lox/lox)) to mice with conditional activation of Kras(G12D). The resulting compound heterozygous mutant mice showed significantly accelerated development of acinar-to-ductal metaplasia (ADM), malignant pancreatic intraepithelial neoplasia (mPanIN), and PDAC within a year. Moreover, all mice with Kras(G12D) activation and Pten homozygous deletion succumbed to cancer by 3 weeks of age. Our data support a dosage-dependent role for PTEN, and the resulting dysregulation of the PI3K/AKT signaling axis, in both PDAC initiation and progression, and shed additional light on the signaling mechanisms that lead to the development of ADM and subsequent mPanIN and pancreatic cancer.

VMY-1-103, a dansylated analog of purvalanol B, induces caspase-3-dependent apoptosis in LNCaP prostate cancer cells

The 2,6,9-trisubstituted purine group of cyclin dependent kinase inhibitors have the potential to be clinically relevant inhibitors of cancer cell proliferation. We have recently designed and synthesized a novel dansylated analog of purvalanol B, termed VMY-1-103, that inhibited cell cycle progression in breast cancer cell lines more effectively than did purvalanol B and allowed for uptake analyses by fluorescence microscopy. ErbB-2 plays an important role in the regulation of signal transduction cascades in a number of epithelial tumors, including prostate cancer (PCa). Our previous studies demonstrated that transgenic expression of activated ErbB-2 in the mouse prostate initiated PCa and either the overexpression of ErbB-2 or the addition of the ErbB-2/ErbB-3 ligand, heregulin (HRG), induced cell cycle progression in the androgen-responsive prostate cancer cell line, LNCaP. In the present study, we tested the efficacy of VMY-1-103 in inhibiting HRG-induced cell proliferation in LNCaP prostate cancer cells. At concentrations as low as 1 μM, VMY-1-103 increased both the proportion of cells in G(1) and p21(CIP1) protein levels. At higher concentrations (5 μM or 10 μM), VMY-1-103 induced apoptosis via decreased mitochondrial membrane polarity and induction of p53 phosphorylation, caspase-3 activity and PARP cleavage. Treatment with 10 μM Purvalanol B failed to either influence proliferation or induce apoptosis. Our results demonstrate that VMY-1-103 was more effective in inducing apoptosis in PCa cells than its parent compound, purvalanol B, and support the testing of VMY-1-103 as a potential small molecule inhibitor of prostate cancer in vivo.

Dietary n-3 polyunsaturated fatty acids fail to reduce prostate tumorigenesis in the PB-ErbB-2 x Pten(+/-) preclinical mouse model

Diet and obesity, and their associated metabolic alterations, are some of the fastest-growing causes of disease and death in America. Findings from epidemiological studies correlating obesity, the sources of dietary fat and prostate cancer (PCa) are conflicting. We have previously shown that 15% of PB-ErbB-2 x pten(+/-) mice developed PCa and exhibited increased phosphorylated 4E-BP1, but not the key PI3-kinase intermediary phospho-protein, mTOR, when maintained on unrefined mouse chow. We report herein that 100% of animals fed refined, westernized AIN-93-based diets containing corn oil developed PCa by 12 months of age. Increases in visceral fat and mTO R activation in the tumors were also observed. Furthermore, nuclear cyclin E levels were significantly induced by the AIN-93-corn oil-based diets versus chow. Replacing 50% of the corn oil with menhaden oil, with 21% of its triglycerides being n-3 PUFA's, had no effect on tumorigenesis, fat deposition, cyclin E or mTOR. Phosphorylated BAD levels were similar in the tumors of mice in all three diets. Our data demonstrated that in the context of our preclinical model, components of crude chow, but not dietary n-3 PUFAs, protect against PCa progression. In addition, these data establish phosphorylated mTOR, nuclear cyclin E and visceral fat deposits as possible biomarkers of increased dietary risk for PCa.