Inhibition of the phosphatidylinositol 3'-kinase pathway promotes autocrine Fas-induced death of phosphatase and tensin homologue-deficient prostate cancer cells

MicroRNA-3651 promotes the growth and invasion of hepatocellular carcinoma cells by targeting PTEN

Background

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors in human worldwide. Evidence indicated that upregulation of microRNA-3651 (miR-3651) was observed in human HCC tissues. In this study, we explored the mechanisms by which miR-3651 regulated the proliferation, apoptosis and invasion of HCC.

Methods

The levels of miR-3651 in human HCC tissues were detected using qRT-PCR assay. In addition, transwell invasion and Western blot assay were conducted to detect cell invasion and apoptosis, respectively. Meanwhile, the dual-luciferase reporter assay was used to explore the interaction of miR-3651 and phosphate and tension homology deleted on chromsome ten (PTEN) in HCC.

Results

The levels of miR-3651 were upregulated in HCC tissues in comparison with the matched normal tissues. Overexpression of miR-3651 significantly promoted the proliferation and invasion of Huh-7 cells. In contrast, inhibition of miR-3651 markedly inhibited the proliferation and invasion of Huh-7 cells via promoting apoptosis. Moreover, downregulation of miR-3651 markedly inhibited tumor growth in vivo. Furthermore, bioinformatics analysis and luciferase reporter assay identified that PTEN was the directly binding target of miR-3651 in Huh-7 cells. Meanwhile, overexpression of miR-3651 obviously decreased the level of PTEN, and increased the expressions of p-p85 and p-Akt in Huh-7 cells.

Conclusion

These results indicated that miR-3651 might act as a potential oncogene in HCC by targeting PTEN. Therefore, miR-3651 might be a novel therapeutic target for the treatment of HCC.

MicroRNA-20b promotes proliferation of H22 hepatocellular carcinoma cells by targeting PTEN

MicroRNAs (miRNAs/miRs) are small, noncoding RNA molecules that are closely associated with the occurrence and development of tumors. miR-20b is overexpressed in hepatocellular carcinoma cell lines and tissues. However, it is not clear whether miR-20b can promote the proliferation of hepatocellular carcinoma cells. In the present study, the proliferation of H22 mouse hepatocellular carcinoma cells was detected using the Cell Counting Kit-8 assay. MiRanda software was used to predict the binding sites of miR-20b to the 3'-untranslated region (3'-UTR) of phosphatase and tensin homolog (PTEN). The 3'-UTR sequence of the PTEN gene was amplified using the polymerase chain reaction in H22 cells. The recombinant plasmid or empty plasmid was co-transfected with miR-20b mimics or miR-20b scramble into HeLa cells, and luciferase activity was assessed by Dual-Luciferase^® Reporter Assay System 24 h post-transfection. In the present study, miR-20b knockdown significantly inhibited the proliferation of H22 mouse hepatocellular carcinoma cells. In addition, miR-20b inhibition upregulated the expression of PTEN, and it was revealed that miR-20b may directly target the 3'-untranslated region of the PTEN gene. Downregulation of PTEN partially reversed the anti-proliferative effect of miR-20b on H22 cells. In conclusion, miR-20b may promote H22 cell proliferation by targeting PTEN, providing a rationale for further study investigating novel therapeutic strategies for liver cancer.

Over-Expression of ATPase II Alleviates Ethanol-Induced Hepatocyte Injury in HL-7702 Cells

Background

Excessive alcohol consumption can cause hepatocellular injury. ATPase II (ATP8A1) can display an ATP-dependent phospholipid translocase activity. However, the function of ATP8A1 in hepatocyte injury is still unclear. In the present study we explored the effect of ATP8A1 on ethanol-induced hepatocyte injury.

Material/Method

A human hepatocyte strain, HL-7702, was pretreated by ethanol with gradient concentration for 2, 4, 8, and 12 h, and were then divided into 6 groups after the cells were transfected. We detected cell viability by use of the Cell Counting Kit-8 (CCK-8) assay. Reactive oxygen species (ROS), apoptosis rate, and mitochondrial membrane potential (MMP) were measured using flow cytometry. We used quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and Western blot to measure the mRNA and protein expression, respectively.

Results

Ethanol inhibited the viability of HL-7702 cells and suppressed the expression of ATP8A1 in dose- and time-dependent manners. Furthermore, over-expression of ATP8A1 reduced the level of ROS and the apoptosis rate and recovered the MMP. Additionally, over-expressed ATP8A1 regulated the protein and mRNA levels of apoptosis-related molecules. Moreover, over-expression of ATP8A1 enhanced the phosphorylation of phosphatidylinositol 3-kinase (PI3K) and protein kinase B (Akt).

Conclusions

Over-expression of ATP8A1 alleviated ethanol-induced hepatocyte injury. Moreover, the PI3K/Akt signaling pathway appears to participate in inhibition of ethanol-induced hepatocyte apoptosis and may provide a candidate target for the treatment of alcoholic liver diseases (ALD).

Hepatitis B Spliced Protein (HBSP) Suppresses Fas-Mediated Hepatocyte Apoptosis via Activation of PI3K/Akt Signaling

Hepatitis B spliced protein (HBSP) is known to associate with viral persistence and pathogenesis; however, its biological and clinical significance remains poorly defined. Acquired resistance to Fas-mediated apoptosis is thought to be one of the major promotors for hepatitis B virus (HBV) chronicity and malignancy. The purpose of this study was to investigate whether HBSP could protect hepatocytes against Fas-initiated apoptosis. We showed here that HBSP mediated resistance of hepatoma cells or primary human hepatocytes (PHH) to agonistic anti-Fas antibody (CH11)- or FasL-induced apoptosis. Under Fas signaling stimulation, expression of HBSP inhibited Fas aggregation and prevented recruitment of the adaptor molecule Fas-associated death domain (FADD) and procaspase-8 (or FADD-like interleukin-1β-converting enzyme [FLICE]) into the death-inducing signaling complex (DISC) while increasing recruitment of cellular FLICE-inhibitory protein L (FLIP_L) into the DISC. Those effects may be mediated through activation of the phosphoinositide 3-kinase (PI3K)/Akt pathway as evidenced by increased cellular phosphatidylinositol (3,4,5)-trisphosphate (PIP3) content and PI3K activity and enhanced phosphorylation of mTORC2 and PDPK1 as well as Akt itself. Confirmedly, inhibition of PI3K by LY294002 reversed the effect of HBSP on Fas aggregation, FLIP_L expression, and cellular apoptosis. These results indicate that HBSP functions to prevent hepatocytes from Fas-induced apoptosis by enhancing PI3K/Akt activity, which may contribute to the survival and persistence of infected hepatocytes during chronic infection.IMPORTANCE Our study revealed a previously unappreciated role of HBSP in Fas-mediated apoptosis. The antiapoptotic activity of HBSP is important for understanding hepatitis B virus pathogenesis. In particular, HBV variants associated with hepatoma carcinoma may downregulate apoptosis of hepatocytes through enhanced HBSP expression. Our study also found that Akt is centrally involved in Fas-induced hepatocyte apoptosis and revealed that interventions directed at inhibiting the activation or functional activity of Akt may be of therapeutic value in this process.

Association of cytosolic sialidase Neu2 with plasma membrane enhances Fas-mediated apoptosis by impairing PI3K-Akt/mTOR-mediated pathway in pancreatic cancer cells

Modulation of sialylation by sialyltransferases and sialidases plays essential role in carcinogenesis. There are few reports on sialyltransferase, however, the contribution of cytosolic sialidase (Neu2) remains unexplored in pancreatic ductal adenocarcinoma (PDAC). We observed lower expression of Neu2 in different PDAC cells, patient tissues, and a significant strong association with clinicopathological characteristics. Neu2 overexpression guided drug-resistant MIAPaCa2 and AsPC1 cells toward apoptosis as evidenced by decreased Bcl2/Bax ratio, activation of caspase-3/caspase-6/caspase-8, PARP reduction, reduced CDK2/CDK4/CDK6, and cyclin-B1/cyclin-E with unaffected caspase-9. Neu2-overexpressed cells exhibited higher expression of Fas/CD95-death receptor, FasL, FADD, and Bid cleavage confirming extrinsic pathway-mediated apoptosis. α2,6-linked sialylation of Fas helps cancer cells to survive, which is a substrate for Neu2. Therefore, their removal should enhance Fas-mediated apoptosis. Neu2-overexpressed cells indeed showed increased enzyme activity even on membrane. Interestingly, this membrane-bound Neu2 exhibited enhanced association with Fas causing its desialylation and activation as corroborated by decreased association of Fas with α2,6-sialic acid-binding lectin. Additionally, enhanced cytosolic Neu2 inhibited the expression of several growth factor-mediated signaling molecules involved in PI3K/Akt–mTOR pathway probably through desialylation which in turn also causes Fas activation. Furthermore, Neu2-overexpressed cells exhibited reduced cell migration, invasion with decreased VEGF, VEGFR, and MMP9 levels. To the best of our knowledge, this is the first report of cytosolic Neu2 on membrane, its association with Fas, enhanced desialylation, activation, and Fas-mediated apoptosis. Taken together, our study ascertains a novel concept by which the function of Fas/CD95 could be modulated indicating a critical role of upstream Neu2 as a promising target for inducing apoptosis in pancreatic cancer.

Effect of silencing the T‑Box transcription factor TBX2 in prostate cancer PC3 and LNCaP cells

T‑Box (TBX)‑2 is a member of the T‑box gene family, which is aberrantly expressed in numerous types of malignant tumors, and has previously been demonstrated to be conducive to tumor progression by acting as a transcription factor. However, specific information regarding the expression and function of TBX2 in prostate cancer cells remains to be elucidated. The present study demonstrated that silencing of TBX2 by TBX2 small interfering RNA inhibited cell proliferation and promoted cell senescence. It was demonstrated that knockdown of TBX2 inhibited cell metastatic abilities by upregulating E‑cadherin and downregulating N‑cadherin, Vimentin and fibronectin. In addition, the expression of TBX2 in prostate cancer tissues and tumor adjacent tissues was detected by immunohistochemistry. The results indicated that the expression rates of TBX2 were significantly increased in the cancerous tissues, compared with the healthy tumor adjacent tissue, and TBX2 increased staining was associated with the clinical stage and pathological grade. The findings of the present study therefore suggest that TBX2 expression is markedly increased in prostate cancer and TBX2 may act as a potential beneficial therapeutic target for the future treatment of prostate cancer.

MicroRNA-20b (miR-20b) Promotes the Proliferation, Migration, Invasion, and Tumorigenicity in Esophageal Cancer Cells via the Regulation of Phosphatase and Tensin Homologue Expression

Increasing evidence has indicated that many microRNAs participate in the development and progression of esophageal cancer and gene expression regulation. MicroRNA-20b (miR-20b) has been reported to be aberrantly expressed in various cancers, but its exact role in esophageal cancer cells remains unclear so far. Therefore, we detected the levels of miR-20b in esophageal tumor tissues and their adjacent normal tissues, and various esophageal cancer cell lines by qRT-PCR. We also explored the effects of miR-20b on cell proliferation, migration, invasion and tumorigenicity of esophageal carcinoma cells through transfection with miR-20b mimics or inhibitor to upregulate or downregulate miR-20b expression in the esophageal cancer cells Eca-109 and KYSE-150, respectively. Additionally, the 3'-untranslated region (3'-UTR) of phosphatase and tensin homologue (PTEN) binding with miR-20b was analyzed by dual-luciferase reporter assays. The results indicated that miR-20b expression level in esophageal tumor tissues was significantly increased compared with their neighboring normal tissues, but its expression was inverse with PTEN protein expression. Luciferase assays confirmed that the 3'-UTR of PTEN was a target of miR-20b in esophageal cancer cells. MiR-20b upregulation promoted cell proliferation, migration, invasiveness, and tumor growth, and decreased apoptosis, and reduced PTEN protein level but not mRNA expression in Eca-109 cells. Conversely, downregulation of miR-20b suppressed these processes in KYSE-150 cells, and enhanced PTEN protein expression. These data indicate that miR-20b plays important roles in tumorigenesis of esophageal cancer possibly via regulation of PTEN expression, and it may be a potential therapeutic target for esophageal cancer treatment.

Tumstatin induces apoptosis and stimulates phosphorylation of p65NF-κB in human osteoblastic osteosarcoma Saos-2 cells

The present study was aimed to investigate the effect of tumstatin on inhibition of proliferation and induction of apoptosis in Saos-2 human osteosarcoma cells and to understand the mechanism involved. Inhibition of cell proliferation was analyzed by MTT assay and induction of apoptosis through nuclear fragmentation assay. Viability of Saos-2 cells was reduced to 19% on treatment with 25 µM concentration of tumstatin after 48 h. Presence of characteristic apoptotic nuclei, rounded cell shape and shrunken size were caused by tumstatin treatment at 25 µM concentration. The level of mRNA corresponding to PTEN, FasR and FasL was increased significantly in tumstatin treated Saos-2 cells compared to untreated control. Investigation of the mechanism revealed NF-κB activation by phosphorylation on serine 536. The activated NF-κB was translocated into the nucleus from the cytoplasm on treatment with tumstatin. Degradation of the IκBα by tumstatin was found to be much slower compared to that induced by treatment with TNF-α. Thus, tumstatin inhibits proliferation and induces apoptosis in Saos-2 cells through activation of NF-κB and its translocation to the nucleus. Therefore, tumstatin can play an important role in the treatment of osteosarcoma.

Bcl-2 family inhibition sensitizes human prostate cancer cells to docetaxel and promotes unexpected apoptosis under caspase-9 inhibition

Docetaxel (DTX) is a useful chemotherapeutic drug for the treatment of hormone-refractory prostate cancer. However, emergence of DTX resistance has been a therapeutic hurdle. In this study, we investigated the effect of combining DTX with Bcl-2 family inhibitors using human prostate cancer cell lines (PC3, LNCaP, and DU145 cells). PC3 cells were less sensitive to DTX than were the other two cell lines. In contrast to ABT-199, which inhibits Bcl-2 and Bcl-w, both ABT-263 and ABT-737, which inhibit Bcl-2, Bcl-xL, and Bcl-w, significantly augmented the antitumor effect of DTX on PC3 cells. ABT-263 also enhanced the antitumor effect of DTX on a DTX-resistant PC3 variant cell line. The antitumor effect of ABT-263 was due mainly to its inhibitory effect on Bcl-xL. In a xenograft mouse model, DTX and ABT-737 combination therapy significantly inhibited PC3 tumor growth. Interestingly, although ABT-263 activated caspase-9 in PC3 cells, inhibition of caspase-9 unexpectedly promoted ABT-263-induced apoptosis in a caspase- 8-dependent manner. This augmented apoptosis was also observed in LNCaP cells. These findings indicate that Bcl-xL inhibition can sensitize DTX-resistant prostate cancer cells to DTX, and they reveal a unique apoptotic pathway in which antagonism of Bcl-2 family members in caspase-9-inhibited prostate cancer cells triggers caspase-8-dependent apoptosis.

Mitoxantrone, More than Just Another Topoisomerase II Poison

Mitoxantrone is a synthetic anthracenedione originally developed to improve the therapeutic profile of the anthracyclines and is commonly applied in the treatment of breast and prostate cancers, lymphomas, and leukemias. A comprehensive overview of the drug's molecular, biochemical, and cellular pharmacology is presented here, beginning with the cardiotoxic nature of its predecessor doxorubicin and how these properties shaped the pharmacology of mitoxantrone itself. Although mitoxantrone is firmly established as a DNA topoisomerase II poison within mammalian cells, it is now clear that the drug interacts with a much broader range of biological macromolecules both covalently and noncovalently. Here, we consider each of these interactions in the context of their wider biological relevance to cancer therapy and highlight how they may be exploited to further enhance the therapeutic value of mitoxantrone. In doing so, it is now clear that mitoxantrone is more than just another topoisomerase II poison.

A precisely substituted benzopyran targets androgen refractory prostate cancer cells through selective modulation of estrogen receptors

Dietary consumption of phytoestrogens like genistein has been linked with lower incidence of prostate cancer. The estradiol-like benzopyran core of genistein confers estrogen receptor-β (ER-β) selectivity that imparts weak anti-proliferative activity against prostate cancer cells. DL-2-[4-(2-piperidinoethoxy)phenyl]-3-phenyl-2H-1-benzopyran (BP), a SERM designed with benzopyran core, targeted androgen independent prostate cancer (PC-3) cells 14-times more potently than genistein, ~25% more efficiently than tamoxifen and 6.5-times more actively than ICI-182780, without forfeiting significant specificity in comparison to genistein. BP increased apoptosis (annexin-V and TUNEL labeling), arrested cell cycle, and significantly increased caspase-3 activity along with mRNA expressions of estrogen receptor (ER)-β and FasL (qPCR) in PC-3 cells. In classical ERE-luc reporter assay BP behaved as a potent ER-α antagonist and ER-β agonist. Accordingly, it decreased expression of ER-α target PS2 (P<0.01) and increased expression of ER-β target TNF-α (P<0.05) genes in PC-3. ER-β deficient PC-3 (siRNA-transfected) was resistant to apoptotic and anti-proliferative actions of SERMs, including stimulation of FasL expression by BP. BP significantly inhibited phosphorylation of Akt and ERK-1/2, JNK and p38 in PC-3 (immunoblotting), and thus adopted a multi-pathway mechanism to exert a more potent anti-proliferative activity against prostate cancer cells than natural and synthetic SERMs. Its precise ER-subtype specific activity presents a unique lead structure for further optimization.

Differential expression of microRNAs in dorsal root ganglia after sciatic nerve injury

This study investigated the possible involvement of microRNAs in the regulation of genes that participate in peripheral neural regeneration. A microRNA microarray analysis was conducted and 23 microRNAs were identified whose expression was significantly changed in rat dorsal root ganglia after sciatic nerve transection. The expression of one of the downregulated microRNAs, microRNA-214, was validated using quantitative reverse transcriptase-PCR. MicroRNA-214 was predicted to target the 3'-untranslated region of Slit-Robo GTPase-activating protein 3. In situ hybridization verified that microRNA-214 was located in the cytoplasm of dorsal root ganglia primary neurons and was downregulated following sciatic nerve transection. Moreover, a combination of in situ hybridization and immunohistochemistry revealed that microRNA-214 and Slit-Robo GTPase-activating protein 3 were co-localized in dorsal root ganglion primary neurons. Western blot analysis suggested that Slit-Robo GTPase-activating protein 3 was upregulated in dorsal root ganglion neurons after sciatic nerve transection. These data demonstrate that microRNA-214 is located and differentially expressed in dorsal root ganglion primary neurons and may participate in regulating the gene expression of Slit-Robo GTPase-activating protein 3 after sciatic nerve transection.

Sulfuretin from heartwood of Rhus verniciflua triggers apoptosis through activation of Fas, Caspase-8, and the mitochondrial death pathway in HL-60 human leukemia cells

Sulfuretin, a flavonoid isolated from heartwood of Rhus verniciflua, has been reported to have anti-cancer activities but the underlying molecular mechanism was not clear. In this study, sulfuretin induced apoptosis by activating caspases-8, -9, and -3 as well as cleavage of poly(ADP-ribose) polymerase. Furthermore, treatment with sulfuretin caused mitochondrial dysfunctions, including the loss of mitochondrial membrane potential (ΔΨ(m)), the release of cytochrome c to the cytosol, and the translocations of Bax and tBid. Sulfuretin also activated the extrinsic apoptosis pathway, that is, it increased the expressions of Fas and FasL, the activation of caspase-8, and the cleavage of Bid. Furthermore, blocking the FasL-Fas interaction with NOK-1 monoclonal antibody prevented the sulfuretin-induced apoptosis. The therapeutical effect of sulfuretin in leukemia is due to its potent apoptotic activity through the extrinsic pathway driven by a Fas-mediated caspase-8-dependent pathway.

Roles of the PI3K/Akt pathway and autophagy in TLR3 signaling-induced apoptosis and growth arrest of human prostate cancer cells

Toll-like receptors (TLRs) are widely expressed in immune cells and play a crucial role in many aspects of the immune response. Although some types of TLRs are also expressed in cancer cells, the effects and mechanisms of TLR signaling in cancer cells have not yet been fully elucidated. In the present study, we analyzed the effects of polyinosinic-polycytidylic acid [poly(I:C)], a TLR3 ligand, on three TLR3-expressing human prostate cancer cell lines (LNCaP, PC3, and DU145). We then further characterized the underlying mechanisms, focusing on the poly(I:C)-sensitive LNCaP cell line. Poly(I:C) significantly reduced the viability of LNCaP cells TLR3 and endosome dependently. One mechanism for the antitumor effect was caspase-dependent apoptosis, and another mechanism was poly(I:C)-induced growth arrest. Cell survival and proliferation of LNCaP cells depended on the PI3K/Akt pathway, and PI3K/Akt inhibitors induced apoptosis and growth arrest similar to poly(I:C) treatment. Additionally, poly(I:C) treatment caused dephosphorylation of Akt in LNCaP cells, but transduction of the constitutively active form of Akt rendered LNCaP cells resistant to poly(I:C). Immunoblot analysis of proliferation- and apoptosis-related molecules in poly(I:C)-treated LNCaP cells revealed participation of cyclinD1, c-Myc, p53, and NOXA. Interestingly, poly(I:C) treatment of LNCaP cells was accompanied by autophagy, which was cytoprotective toward poly(I:C)-induced apoptosis. Together, these findings indicate that TLR3 signaling triggers apoptosis and growth arrest of LNCaP cells partially through inactivation of the PI3K/Akt pathway and that treatment-associated autophagy plays a cytoprotective role.

Matrix-dependent regulation of AKT in Hepsin-overexpressing PC3 prostate cancer cells

The serine-protease hepsin is one of the most prominently overexpressed genes in human prostate carcinoma. Forced expression of the enzyme in mice prostates is associated with matrix degradation, invasive growth, and prostate cancer progression. Conversely, hepsin overexpression in metastatic prostate cancer cell lines was reported to induce cell cycle arrest and reduction of invasive growth in vitro. We used a system for doxycycline (dox)-inducible target gene expression in metastasis-derived PC3 cells to analyze the effects of hepsin in a quantitative manner. Loss of viability and adhesion correlated with hepsin expression levels during anchorage-dependent but not anchorage-independent growth. Full expression of hepsin led to cell death and detachment and was specifically associated with reduced phosphorylation of AKT at Ser(473), which was restored by growth on matrix derived from RWPE1 normal prostatic epithelial cells. In the chorioallantoic membrane xenograft model, hepsin overexpression in PC3 cells reduced the viability of tumors but did not suppress invasive growth. The data presented here provide evidence that elevated levels of hepsin interfere with cell adhesion and viability in the background of prostate cancer as well as other tissue types, the details of which depend on the microenvironment provided. Our findings suggest that overexpression of the enzyme in prostate carcinogenesis must be spatially and temporally restricted for the efficient development of tumors and metastases.

Human prostate cancer xenografts in lit/lit mice exhibit reduced growth and androgen-independent progression

BACKGROUND

The growth hormone/insulin-like growth factor I (GH/IGF-I) axis has been linked to prostate cancer (PCa) risk. Although previous studies indicate that human breast cancers and a murine PCa model develop more slowly in murine hosts homozygous for a missense mutation in the GH-releasing hormone receptor (lit/lit) whose "little" dwarfed phenotype is caused by suppressed GH and IGF-I production, the role of these two hormones remains controversial.

METHODS

To assess how the GH/IGF-I axis influences androgen-responsive, castration-resistant (CR), and androgen-independent (AI) growth of human PCa, we compared xenograft growth of the androgen-responsive human PCa cells, LNCaP, and AI human PCa cells, PC3, in intact and castrate Nod/SCID lit/lit and lit/+ mice, and in vitro growth of these cell lines in lit/lit and lit/+ serum-containing media supplemented with GH or IGF-I.

RESULTS

Tumor growth and PSA accumulation rates were suppressed in LNCaP tumor-bearing lit/lit mice pre- and post-castration. Growth of PC3 xenografts in lit/lit mice was also suppressed. In vitro proliferation of LNCaP and PC3 cells cultured in media containing lit/lit mouse serum was decreased as compared to growth in media containing lit/+ serum. Suppressed growth in lit/lit serum could be restored by the addition of IGF-I, and to a lesser extent, GH. Differences in growth correlated with differences in steady-state AKT and ERK1/2 activation.

CONCLUSIONS

This study demonstrates that circulating GH and IGF-I can promote androgen-responsive growth, CR progression, and AI expansion of PTEN-deficient human PCa cell xenografts and indicates that IGF-I can promote PCa growth in a suppressed GH environment.

The role of PI 3-kinase p110beta in AKT signally, cell survival, and proliferation in human prostate cancer cells

BACKGROUND

Class IA PI 3-kinases produce phosphatidylinositol (3,4,5)-trisphosphate (PIP3). PIP3 is bound by AKT which facilities its activation by PDK1. Activated AKT promotes cell survival and stimulates cell proliferation. Class IA PI 3-kinases are heterodimers consisting of a regulatory subunit p85 and a catalytic subunit p110. The p110alpha isoform has been shown to be mutated in a number of tumor types. A number of recent studies suggest that the p110beta isoform may be functionally relevant in prostate cancer. In this study we extend this work to include the examination of the expression and functional properties of p110alpha and p110beta in three different prostate cancer cell lines, DU145, LNCaP, PC3, as well as the non-tumorigenic but immortalized RWPE1 prostate epithelial cell line.

METHODS

Western blot analysis was used to measure protein expression and quantitative real-time PCR was used to measure mRNA levels. After targeted knockdown using isoform-specific siRNAs to reduce PI 3-kinase p110alpha or p110beta isoform expression, we measured downstream signally events such as phosphorylation of AKT, ERK 1/2, PDK, and FOXO, as well as biological consequences such as changes in apoptosis, and alterations in cell cycle progression.

RESULTS

In all three prostate cancer cell lines examined, targeted knockdown of p110beta, and not p110alpha, resulted in significantly reduced AKT, PDK, and FOXO phosphorylation. While knockdown of either p110 isoform resulted in an increase in apoptosis and a cell cycle arrest in G1 in the remaining non-apoptotic cells, these effects were much more pronounced with knockdown of p110beta.

CONCLUSIONS

Our results support the concept that p110beta appears to be the predominant functional class I PI 3-kinase isoform in prostate cancer cells.

Ursolic acid induces PC-3 cell apoptosis via activation of JNK and inhibition of Akt pathways in vitro

Ursolic acid (UA), a pentacyclic triterpenoid compound, has been demonstrated to have an antiproliferative effect in various tumors. We investigated the cell killing effects of UA in the human hormone refractory prostate cancer cell line, PC-3 cells. Also, the molecular mechanisms underlying its antigrowth effect were explored. We found that UA treatment in vitro can effectively inhibit PC-3 cell viability in a dose-dependent manner by inducing apoptosis, demonstrated by annexin V-FITC/propidium iodide staining. Both extrinsic and intrinsic apoptotic pathways appear to be triggered by UA treatment, because inhibiting activation of both caspase-8 and -9 could prevent UA-induced apoptosis in PC-3 cells. The c-Jun N-terminal kinase (JNK) was found to be activated, followed by Bcl-2 phosphorylation and activation of caspase-9. On the other hand, UA inhibited the Akt pathway, subsequently upregulating the expression of Fas ligand (FasL), which initiates death receptor-mediated apoptosis in PC-3 cells. Importantly, experimentally lowering FasL expression by siRNA significantly inhibited UA-induced caspase-8 activation and at least partly attenuated the consequent apoptosis, suggesting an involvement of FasL and its regulating pathway in the cell killing effect of UA. UA also inhibited cell invasion by downregulating matrix metalloproteinase-9 via inhibition of Akt in PC-3 cells. Although further evaluation of the UA effects in vivo is needed, the present results suggest the potential utility of UA as a novel therapeutic agent in advanced prostate cancer.

E-cadherin-mediated survival of androgen-receptor-expressing secretory prostate epithelial cells derived from a stratified in vitro differentiation model

The androgen receptor (AR) is expressed in differentiated secretory prostate epithelial cells in vivo. However, in the human prostate, it is unclear whether androgens directly promote the survival of secretory cells, or whether secretory cells survive through androgen-dependent signals from the prostate stroma. Biochemical and mechanistic studies have been hampered by inadequate cell-culture models. In particular, large-scale differentiation of prostate epithelial cells in culture has been difficult to achieve. Here, we describe the development of a differentiation system that is amenable to functional and biochemical analysis and its application to deciphering the survival pathways in differentiated AR-expressing epithelial cells. Confluent prostate epithelial cell cultures were treated with keratinocyte growth factor (KGF) and dihydrotestosterone. After 2 weeks, a suprabasal cell layer was formed in which cells no longer expressed alpha2, alpha3, alpha6, alphav, beta1 or beta4 integrins or p63, K5, K14, EGFR, FGFR2IIIb or Bcl-2, but instead expressed AR and androgen-induced differentiation markers, including K18, K19, TMPRSS2, Nkx3.1, PMSA, KLK2 and secreted prostate-specific antigen (PSA). Differentiated prostate cell survival depended on E-cadherin and PI3K, but not KGF, androgen, AR or MAPK. Thus survival of differentiated prostate epithelial cells is mediated by cell-cell adhesion, and not through androgen activity or prostate stroma-derived KGF.

Antisense oligonucleotide targeting of insulin-like growth factor-1 receptor (IGF-1R) in prostate cancer

OBJECTIVE

Altered expression of insulin-like growth factor receptor (IGF-1R) is associated with castrate-resistant prostate cancer (CRPC) progression. We hypothesize that increased expression and/or responsiveness of IGF-IR may promote disease progression. This study assesses ATL1101, a 2'-MOE-modified antisense oligonucleotide (ASO) targeting human IGF-IR, with regard to potency and anti-cancer activity in androgen-responsive (LNCaP) and -independent (PC3) prostate cancer cells in vitro and in vivo.

METHODS

IGF-IR mRNA and protein expression was assessed in ATL1101- and control oligonucleotides (ODN)-treated prostate cancer cells by QT-PCR and immunoblotting. The effect of IGF-1R ASO on cell growth and apoptosis in vitro was examined by crystal violet assay, flow cytometry, and expression and activation state of downstream signaling targets was examined by immunoblotting. In vivo growth of subcutaneous xenografts was performed in nude mice treated with intraperitoneally administered ATL1101 or control ODN by measuring tumor volume of PC3 xenografts in intact mice, and tumor volume and serum prostate-specific antigen levels in castrated mice harboring LNCaP xenografts.

RESULTS

We observed dose- and sequence-specific suppression of IGF-IR mRNA and protein expression in ATL1101-treated cells in vitro. Suppressed IGF-IR expression correlated with decreased proliferation and increased apoptosis of PC3 cells under standard culture conditions and of LNCaP cells under androgen-deprived culture conditions. ATL1101 suppressed PC3 tumor growth as a monotherapy and delayed CRPC progression of LNCaP xenografts.

CONCLUSIONS

This study reports the first preclinical proof-of-principle data that this novel IGF-IR ASO selectively suppresses IGF-1R expression, suppresses growth of CRPC tumors, and delays CRPC progression in vitro and in vivo.

Disruption of occludin function in polarized epithelial cells activates the extrinsic pathway of apoptosis leading to cell extrusion without loss of transepithelial resistance

Background

Occludin is a tetraspanin protein normally localized to tight junctions. The protein interacts with a variety of pathogens including viruses and bacteria, an interaction that sometimes leads to its extrajunctional localization.

Results

Here we report that treatment of mammary epithelial monolayers with a circularized peptide containing a four amino acid sequence found in the second extracellular loop of occludin, LHYH, leads to the appearance of extrajunctional occludin and activation of the extrinsic apoptotic pathway. At early times after peptide treatment endogenous occludin and the LYHY peptide were co-localized in extrajunctional patches, which were also shown to contain components of the death inducing signaling complex (DISC), caspases 8 and 3, the death receptor FAS and the adaptor molecule FADD. After this treatment occludin could be immunoprecipitated with FADD, confirming its interaction with the DISC. Extrusion after LYHY treatment was accomplished with no loss of epithelial resistance.

Conclusion

These observations provide strong evidence that, following disruption, occludin forms a complex with the extrinsic death receptor leading to extrusion of apoptotic cells from the epithelial monolayer. They suggest that occludin has a protective as well as a barrier forming role in epithelia; pathogenic agents which utilize this protein as an entry point into the cell might set off an apoptotic reaction allowing extrusion of the infected cell before the pathogen can gain entry to the interstitial space.

PTEN loss promotes mitochondrially dependent type II Fas-induced apoptosis via PEA-15

Two distinct biochemical signals are delivered by the CD95/Fas death receptor. The molecular basis for the differential mitochondrially independent (type I) and mitochondrially dependent (type II) Fas apoptosis pathways is unknown. By analyzing 24 Fas-sensitive tumor lines, we now demonstrate that expression/activity of the PTEN tumor suppressor strongly correlates with the distinct Fas signals. PTEN loss-of-function and gain-of-function studies demonstrate the ability to interconvert between type I and type II Fas pathways. Importantly, from analyses of Bcl-2 transgenic Pten(+/-) mice, Pten haploinsufficiency converts Fas-induced apoptosis from a Bcl-2-independent to a Bcl-2-sensitive response in primary thymocytes and activated T lymphocytes. We further show that PTEN influences Fas signaling, at least in part, by regulating PEA-15 phosphorylation and activity that, in turn, regulate the ability of Bcl-2 to suppress Fas-induced apoptosis. Thus, PTEN is a key molecular rheostat that determines whether a cell dies by a mitochondrially independent type I versus a mitochondrially dependent type II apoptotic pathway upon Fas stimulation.

Combination of PTEN and gamma-ionizing radiation enhances cell death and G(2)/M arrest through regulation of AKT activity and p21 induction in non-small-cell lung cancer cells

PURPOSE

To identify the role of phosphatase and tensin homolog deleted on chromosome 10 (PTEN) during gamma-ionizing radiation (gamma-IR) treatment for non-small-cell lung cancer cells.

METHODS AND MATERIALS

Wild-type PTEN or mutant forms of PTEN plasmids were transfected to construct stable transfectants of the NCI-H1299 non-small-cell lung cancer cell line. Combined effects of PTEN expression and IR treatment were tested using immunoblot, clonogenic, and cell-counting assays. Related signaling pathways were studied with immunoblot and kinase assays.

RESULTS

At steady state, stable transfectants showed almost the same proliferation rate but had different AKT phosphorylation patterns. When treated with gamma-IR, wild-type PTEN transfectants showed higher levels of cell death compared with mock vector or mutant transfectants, and showed increased G(2)/M cell-cycle arrest accompanied by p21 induction and CDK1 inactivation. NCI-H1299 cells were treated with phosphosinositide-3 kinase (PI3K)/AKT pathway inhibitor (LY29002), resulting in reduced AKT phosphorylation levels. Treatment of NCI-H1299 cells with LY29002 and gamma-IR resulted in increased cell-cycle arrest and p21 induction. Endogenous wild-type PTEN-containing NCI-H460 cells were treated with PTEN-specific siRNA and then irradiated with gamma-IR: however reduced PTEN levels did not induce cell-cycle arrest or p21 expression.

CONCLUSIONS

Taken together, these findings indicate that PTEN may modulate cell death or the cell cycle via AKT inactivation by PTEN and gamma-IR treatment. We also propose that a PTEN-PI3K/AKT-p21-CDK1 pathway could regulate cell death and the cell cycle by gamma-IR treatment.

Extracellular zinc and zinc-citrate, acting through a putative zinc-sensing receptor, regulate growth and survival of prostate cancer cells

Prostate Zn(2+) concentrations are among the highest in the body, and a marked decrease in the level of this ion is observed in prostate cancer. Extracellular Zn(2+) is known to regulate cell survival and proliferation in numerous tissues. In spite of this, a signaling role for extracellular Zn(2+) in prostate cancer has not been established. In the present study, we demonstrate that prostate metastatic cells are impermeable to Zn(2+), but extracellular Zn(2+) triggers a metabotropic Ca(2+) rise that is also apparent in the presence of citrate. Employing fluorescent imaging, we measured this activity in androgen-insensitive metastatic human cell lines, PC-3 and DU-145, and in mouse prostate tumor TRAMP-1 cells but not in androgen-sensitive LNCaP cells. The Ca(2+) response was inhibited by Galphaq and phospholipase C (PLC) inhibitors as well as by intracellular Ca(2+) store depletion, indicating that it is mediated by a Gq-coupled receptor that activates the inositol phosphate (IP(3)) pathway consistent with the previously identified zinc-sensing receptor (ZnR). Zn(2+)-dependent extracellular signal-regulated kinase and AKT activation, as well as enhanced Zn(2+)-dependent cell growth and survival, were observed in PC-3 cells that exhibit ZnR activity, but not in a ZnR activity-deficient PC-3 subline. Interestingly, application of Zn(2+)-citrate (Zn(2+)Cit), at physiological concentrations, was followed by a profound functional desensitization of extracellular Zn(2+)-dependent signaling and attenuation of Zn(2+)-dependent cell growth. Our results indicate that extracellular Zn(2+) and Zn(2+)Cit, by triggering or desensitizing ZnR activity, distinctly regulate prostate cancer cell growth. Thus, therapeutic strategies based either on Zn(2+) chelation or administration of Zn(2+)Cit may be effective in attenuating prostate tumor growth.

Small-molecule agonists of SHIP1 inhibit the phosphoinositide 3-kinase pathway in hematopoietic cells

Because phosphoinositide 3-kinase (PI3K) plays a central role in cellular activation, proliferation, and survival, pharmacologic inhibitors targeting components of the PI3K pathway are actively being developed as therapeutics for the treatment of inflammatory disorders and cancer. These targeted drugs inhibit the activity of either PI3K itself or downstream protein kinases. However, a previously unexplored, alternate strategy is to activate the negative regulatory phosphatases in this pathway. The SH2-containing inositol-5′-phosphatase SHIP1 is a normal physiologic counter-regulator of PI3K in immune/hematopoietic cells that hydrolyzes the PI3K product phosphatidylinositiol-3,4,5-trisphosphate (PIP3). We now describe the identification and characterization of potent and specific small-molecule activators of SHIP1. These compounds represent the first small-molecule activators of a phosphatase, and are able to activate recombinant SHIP1 enzyme in vitro and stimulate SHIP1 activity in intact macrophage and mast cells. Mechanism of activation studies with these compounds suggest that they bind a previously undescribed, allosteric activation domain within SHIP1. Furthermore, in vivo administration of these compounds was protective in mouse models of endotoxemia and acute cutaneous anaphylaxis, suggesting that SHIP1 agonists could be used therapeutically to inhibit the PI3K pathway.

Standard mutation nomenclature in molecular diagnostics: practical and educational challenges

To translate basic research findings into clinical practice, it is essential that information about mutations and variations in the human genome are communicated easily and unequivocally. Unfortunately, there has been much confusion regarding the description of genetic sequence variants. This is largely because research articles that first report novel sequence variants do not often use standard nomenclature, and the final genomic sequence is compiled over many separate entries. In this article, we discuss issues crucial to clear communication, using examples of genes that are commonly assayed in clinical laboratories. Although molecular diagnostics is a dynamic field, this should not inhibit the need for and movement toward consensus nomenclature for accurate reporting among laboratories. Our aim is to alert laboratory scientists and other health care professionals to the important issues and provide a foundation for further discussions that will ultimately lead to solutions.