The effect of tyrosine kinase inhibitors, tyrphostins: AG1024 and SU1498, on autocrine growth of prostate cancer cells (DU145)

Reactivation of nucleases with peroxidation damages induced by a menadione: ascorbate combination devastates human prostate carcinomas: ultrastructural aspects

INTRODUCTION

Xenografts of androgen-independent human DU145 prostate metastatic carcinomas implanted in nu/nu male mice have revealed a significant survival after a prooxidant anticancer treatment consisting of a combination of menadione bisulfite and sodium ascorbate (VK3:VC).

METHODS

Implanted samples of diaphragm carcinomas from longest survived mice from either oral, intraperitoneal (IP), or both oral and IP treatment groups were assessed with light, scanning, and transmission electron microscopy to analyze morphologic damages.

RESULTS

Compared with previous fine structure data of in vitro untreated carcinomas, the changes induced by oral, IP, and oral with IP VK3:VC treatment dismantled those xenografts with autoschizis, and necrotic atrophy was accomplished by cell's oxidative stress whose injuries were consequent to reactivated deoxyribonucleases and ribonucleases. Tumor destructions resulted from irreversible damages of nucleus components, endoplasmic reticulum, and mitochondria there. Other alterations included those of the cytoskeleton that resulted in characteristic self-excisions named " autoschizis." All these injuries lead resilient cancer cells to necrotic cell death.

CONCLUSION

The fine structure damages caused by VK3:VC prooxidant combination in the human DU145 prostate xenografts confirmed those shown in vitro and of other cell lines with histochemistry and biomolecular investigations. These devastations incurred without damage to normal tissues; thus, our data brought support for the above combination to assist in the treatment of prostate cancers and other cancers.

Xenografts on nude mouse diaphragm of human DU145 prostate carcinoma cells: mesothelium removal by outgrowths and angiogenesis

Human prostate carcinoma DU145 cells, androgen-independent malignant cells, implanted in the athymic nu/nu male mouse, developed numerous tumors on peritoneal and retro-peritoneal organs whose growth aspects and vascular supply have yet to be investigated with fine structure techniques. A series of necropsies from moribund implanted mice diaphragms were examined with light, scanning, and transmission electron microscopy. DU145 xenografts installations, far away from the implanted site, were described as the smallest installation to large diaphragm outgrowths in moribund mice. Carcinomas did not show extracellular matrix and, reaching more than 0.15 mm in thickness, they revealed new structures in these outgrowths. Voids to be gland-like structures with mediocre secretion and, unexpectedly, intercellular spaces connected with fascicles of elongated DU145 cells that merged with a vascular supply originated from either the tumor cells and/or some perimysium vessels. In the largest carcinomas, most important vascular invasions coincidently accompanied the mouse lethality, similarly to human cancers. This androgen-independent model would be useful to study tumor outgrowth's changes related to testing anticancer strategy, including anti-angiogenic therapies involving toxicity, simultaneously with those of other vital organs with combined biomolecular and fine structure techniques.

SKLB1002, a potent inhibitor of VEGF receptor 2 signaling, inhibits endothelial angiogenic function in vitro and ocular angiogenesis in vivo

Ocular angiogenesis is a major cause of severe vision loss, which can affect several parts of the eye, including the retina, choroid and cornea. Vascular endothelial growth factor receptor 2 (VEGFR2) inhibitors have demonstrated great potential for treating ocular angiogenesis and SKLB1002 is a potent inhibitor of VEGF receptor 2 signaling. The present study investigated the effects of SKLB1002 administration on ocular angiogenesis. SKLB1002 administration did not show obvious cytotoxicity and tissue toxicity at the tested concentrations. In an alkali-burn corneal model, SKLB1002 administration significantly decreased the mean length and number of new corneal blood vessels. SKLB1002 administration significantly reduced endothelial cell proliferation, migration and tube formation in vitro. Mechanistically, SKLB1002 inhibited endothelial angiogenic functions by blocking the phosphorylation of ERK1/2, JNK and p38. Thus, selective inhibition of VEGFR-2 through SKLB1002 administration is a promising therapy for ocular angiogenesis.

Meteorin-like facilitates skeletal muscle repair through a Stat3/IGF-1 mechanism

The immune system plays a multifunctional role throughout the regenerative process, regulating both pro-/anti-inflammatory phases and progenitor cell function. In the present study, we identify the myokine/cytokine Meteorin-like (Metrnl) as a critical regulator of muscle regeneration. Mice genetically lacking Metrnl have impaired muscle regeneration associated with a reduction in immune cell infiltration and an inability to transition towards an anti-inflammatory phenotype. Isochronic parabiosis, joining wild-type and whole-body Metrnl knock-out (KO) mice, returns Metrnl expression in the injured muscle and improves muscle repair, providing supportive evidence for Metrnl secretion from infiltrating immune cells. Macrophage-specific Metrnl KO mice are also deficient in muscle repair. During muscle regeneration, Metrnl works, in part, through Stat3 activation in macrophages, resulting in differentiation to an anti-inflammatory phenotype. With regard to myogenesis, Metrnl induces macrophage-dependent insulin-like growth factor 1 production, which has a direct effect on primary muscle satellite cell proliferation. Perturbations in this pathway inhibit efficacy of Metrnl in the regenerative process. Together, these studies identify Metrnl as an important regulator of muscle regeneration and a potential therapeutic target to enhance tissue repair.

Genistein and AG1024 synergistically increase the radiosensitivity of prostate cancer cells

Radiosensitivity of prostate cancer (PCa) cells promotes the curative treatment for PCa. The present study was designed to investigate the synergistic effect of genistein and AG1024 on the radiosensitivity of PCa cells. The optimal X-irradiation dose (4 Gy) and genistein concentration (30 µM) were selected by using the CCK-8 assay. Before X-irradiation (4 Gy), PC3 and DU145 cells were treated with genistein (30 µM), AG1024 (10 µM) and their combination. All treatments significantly reduced cell proliferation and enhanced cell apoptosis. Using flow cytometric analysis, we found that genistein arrested the cell cycle at S phase and AG1024 arrested the cell cycle at G2/M phase. Genistein treatment suppressed the homologous recombination (HRR) and the non-homologous end joining (NHEJ) pathways by inhibiting the expression of Rad51 and Ku70, and AG1024 treatment only inhibited the NHEJ pathway via the inactivation of Ku70 as detected by western blot analysis. Moreover, the combination treatment with genistein and AG1024 more effectively radiosensitized PCa cells than single treatments by suppressing cell proliferation, enhancing cell apoptosis and inactivating the HRR and NHEJ pathways. In vivo experiments demonstrated that animals receiving the combination treatment with genistein and AG1024 displayed obviously decreased tumor volume compared with animals treated with single treatment with either genistein or AG1024. We conclude that the combination of genistein (30 µM) and AG1024 (10 µM) exhibited a synergistic effect on the radiosensitivity of PCa cells by suppressing the HRR and NHEJ pathways.

P18 peptide, a functional fragment of pigment epithelial-derived factor, inhibits angiogenesis in hepatocellular carcinoma via modulating VEGF/VEGFR2 signalling pathway

The P18 peptide is a functional fragment of pigment epithelial-derived factor (PEDF), which is an endogenic angiogenesis inhibitor. This study sought to determine the anti-angiogenic bioactivity of the P18 peptide in hepato-cellular carcinoma (HCC) and to elucidate the underlying mechanism. Xenograft tumour growth assays demonstrated the P18 peptide suppressed angiogenesis of HCC in vivo. Wound healing, Transwell and Matrigel-culture assays indicated that the P18 peptide inhibited the cell migration and tube formation of endothelial cells (ECs) in vitro. Cell viability and apoptosis assessed by Cell Counting Kit-8 (CCK-8) and flow cytometry assays suggested that the P18 peptide inhibited angiogenesis by inducing apoptosis of ECs. Angiogenesis- and signal transduction-associated molecules analysed by western blot demonstrated that the P18 peptide targets vascular endothelial cell growth factor receptor 2 (VEGFR2) on ECs. In conclusion, by inhibiting the phosphorylation of VEGFR2, the P18 peptide modulates signalling transduction between VEGF/VEGFR2 and suppresses activation of the PI3K/Akt cascades, leading to an increase in mitochondrial-mediated apoptosis and anti-angiogenic activity. This bioactivity of the P18 peptide may represent a novel therapeutic strategy for the treatment of HCC.

Effect of VEGFR, PDGFR and PI3K/mTOR Targeting in Glioblastoma

Resistance to targeted therapy is a well known obstacle in cancer therapy. The cross-talk between several growth factor receptors generates redundancy in their intracellular pathways that usually mediates resistance to receptor targeted therapy. Simultaneous inactivation of two or more growth factor receptors has been suggested to prevent the cross-talk between their signaling pathways and to better eliminate malignant cells. Here we found that targeted therapy against these receptors induced moderate cell death in glioblastoma cells. More important, dual PDGFR and VEGFR inactivation induced more pronounceable cell death compared to inactivation of each receptor alone but failed to induce synergistic cell death in glioblastoma. PI3K/mTOR dual targeting has been identified as an efficient therapeutic approach in several malignant diseases, including glioblastoma. Therefore, we also investigated the PI3K/mTOR pathways inhibition effect in glioblastoma cells. Our results showed that inactivation of PI3K/mTOR pathways were more efficient than PDGFR or VEGFR single targeting or their dual inhibition.

Induced apoptosis in human prostate cancer cells by blocking of vascular endothelial growth factor by siRNA

INTRODUCTION

Vascular endothelial growth factor (VEGF) regulates several cell functions including; proliferation, differentiation, permeability, vascular tone, and the production of vasoactive molecules. The purpose of this study was to evaluate the potency of specific short-interfering RNA (siRNA) to suppress human VEGF expression by siRNA and investigate the effects of VEGF down-regulation on the cell proliferation and apoptosis of the human prostate cancer cell lines DU-145.

METHODS

Transfection was performed using X-tremeGENE siRNA transfection reagent. At different time intervals, transfected cells were harvested and total RNA was extracted for RT-PCR. The VEGF content in supernatants were measured by ELISA. Inhibition of cell growth by hVEGF-siRNA was measured by using cell proliferation ELISA BrdU assay. Apoptotic cells were evaluated by using annexin-V-FITC apoptotic detection method.

RESULTS

Transfection of hVEGF-siRNA resulted in statistically significant inhibition of hVEGF-mRNA that in turn caused a marked reduction in the expression of hVEGF. The cell growth was assessed every 24 h for 4 days after siRNA treatment resulted in a marked inhibition of cell proliferation as compared to scramble siRNA. The results of apoptosis showed that approximately 15 % of the cells treated with control-siRNA manifested evident apoptotic changes after 24 hpt, whereas DU-145 cells treated with hVEGF-siRNA significantly were positive, that is to say, 53 % at 72 hpt 23.9 ± 2.78 % (P < 0.001) and 13 ± 1.57 % at 96 hpt.

CONCLUSION

Our findings indicate that siRNA are effective in eliciting the RNAi pathway in cancerous cells and that specific siRNA efficiently down-regulate VEGF expression. They could decrease VEGF production and induce apoptosis, which may also be linked to the inhibition of cancerous cell proliferation. Therefore, it can be concluded that siRNA-mediated suppression of VEGF represents a powerful tool against prostate cancer cell proliferation. VEGF down-regulation exerts a direct anti-apoptotic function in the DU-145 cell lines and promises the development of drugs for cancer therapy.

Valproic acid synergistically enhances the cytotoxicity of gossypol in DU145 prostate cancer cells: an iTRTAQ-based quantitative proteomic analysis

Gossypol (GOS), a BH3 mimetic, has been investigated as a sensitizing co-therapy to radiation and chemotherapy in treatment of metastatic prostate cancer. In this study, we found that valproic acid (VPA), a histone deacetylase inhibitor (HDACI), counteracted the suppressive effect of GOS on histone H3 acetylation and enhanced the cytotoxicity of GOS to DU145 prostate cancer cells. Significant synergistic effects were observed in combined GOS and VPA treatment, culminating in more DNA damage and cell death. The iTRAQ-based quantitative proteomic analysis revealed differential proteomic profiles in cells treated with VPA, GOS or their combination. In GOS-treated cells, oxidative phosphorylation-related proteins were depressed and endoplasmic reticulum stress markers were upregulated. In the presence of VPA, the GOS-induced mitochondrial stress was further enhanced since glycolysis- and hypoxia-associated proteins were upregulated, suggesting a disruption of energy metabolism in these cells. Furthermore, the DNA damage repair ability of cells co-treated with GOS and VPA was also decreased, as evidenced by the downregulation of DNA damage repair proteins and the enhancement of DNA fragmentation and cell death. These findings suggest that GOS in combination with an HDACI has the potential to increase its clinical efficacy in the treatment of prostate cancer.

TRAIL-induced apoptosis and expression of death receptor TRAIL-R1 and TRAIL-R2 in bladder cancer cells

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL/Apo2L) is a member of TNF superfamily able to induce programmed death in cancer cells with no toxicity against normal tissues. TRAIL mediate apoptosis follows binding to the two death receptors, TRAIL-R1 (DR4) and/or TRAIL-R2 (DR5). In this study we investigated the cytotoxic and apoptotic effect of TRAIL on bladder cancer cells and the expression of death receptor TRAIL-R1 and TRAIL-R2 on the surface of these cancer cells. Three human bladder transitional cancer cell (TCC) lines - SW780, 647V and T24 were tested for TRAIL sensitivity. The bladder cancer cells were incubated with human soluble recombinant TRAIL. Cytotoxicity was measured by MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-dimethyltetrazolium bromide) and LDH (lactate dyhydrogenase) assays. Apoptosis was detected by flow cytometry with annexin V-FITC/propidium iodide and by fluorescence microscopy with Hoechst 33342/annexin V-FITC/Ethidium Homodimer. The cell surface expression of TRAIL death receptors on bladder cancer were determined using flow cytometry with phycoerythrin-conjugated monoclonal anti-human TRAIL-R1 and TRAIL-R2. Our investigations confirmed that SW780 cells were sensitive to TRAIL, and two other bladder cancer cell lines, 647V and T24, were resistant to TRAIL induced apoptosis. We therefore examined the expression of TRAIL death receptors on bladder cancer cell surfaces. We showed decreased expression of TRAIL-R2 receptor in TRAIL-resistant bladder cancer cells and increased expression of this death receptor in TRAIL-sensitive SW780 cells. The expression of TRAILR1 receptor was similar in all bladder cancer cell lines. TRAIL is one of the promising candidates for cancer therapeutics. However, some cancer cells are resistant to TRAIL-mediated apoptosis. It is therefore important to overcome this resistance for the clinical use of TRAIL in cancer therapy. TRAIL death receptors are attractive therapeutic targets in cancer treatment. The cytotoxic agents capable of up-regulating the expression of TRAIL-R1 and TRAIL-R2 can sensitize cancer cells to TRAIL induced apoptosis.

Mammalian target of rapamycin regulates vascular endothelial growth factor-dependent liver cyst growth in polycystin-2-defective mice

Polycystic liver disease may complicate autosomal dominant polycystic kidney disease (ADPKD), a disease caused by mutations in polycystins, which are proteins that regulate signaling, morphogenesis, and differentiation in epithelial cells. The cystic biliary epithelium [liver cystic epithelium (LCE)] secretes vascular endothelial growth factor (VEGF), which promotes liver cyst growth via autocrine and paracrine mechanisms. The expression of insulin-like growth factor 1 (IGF1), insulin-like growth factor 1 receptor (IGF1R), and phosphorylated mammalian target of rapamycin (p-mTOR) and the protein kinase A (PKA)-dependent phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) are also up-regulated in LCE. We have hypothesized that mammalian target of rapamycin (mTOR) represents a common pathway for the regulation of hypoxia-inducible factor 1 alpha (HIF1alpha)-dependent VEGF secretion by IGF1 and ERK1/2. Conditional polycystin-2-knockout (Pkd2KO) mice were used for in vivo studies and to isolate cystic cholangiocytes [liver cystic epithelial cells (LCECs)]. The expression of p-mTOR, VEGF, cleaved caspase 3 (CC3), proliferating cell nuclear antigen (PCNA), IGF1, IGF1R, phosphorylated extracellular signal-regulated kinase, p-P70S6K, HIF1alpha, and VEGF in LCE, LCECs, and wild-type cholangiocytes was studied with immunohistochemistry, western blotting, or enzyme-linked immunosorbent assays. The cystic area was measured by computer-assisted morphometry of pancytokeratin-stained sections. Cell proliferation in vitro was studied with 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium and bromodeoxyuridine assays. The treatment of Pkd2KO mice with the mTOR inhibitor rapamycin significantly reduced the liver cyst area, liver/body weight ratio, pericystic microvascular density, and PCNA expression while increasing expression of CC3. Rapamycin inhibited IGF1-stimulated HIF1alpha accumulation and VEGF secretion in LCECs. IGF1-stimulated LCEC proliferation was inhibited by rapamycin and SU5416 (a vascular endothelial growth factor receptor 2 inhibitor). Phosphorylation of the mTOR-dependent kinase P70S6K was significantly reduced by PKA inhibitor 14-22 amide and by the mitogen signal-regulated kinase inhibitor U1026.

CONCLUSION

These data demonstrate that PKA-dependent up-regulation of mTOR has a central role in the proliferative, antiapoptotic, and pro-angiogenic effects of IGF1 and VEGF in polycystin-2-defective mice. This study also highlights a mechanistic link between PKA, ERK, mTOR, and HIF1alpha-mediated VEGF secretion and provides a proof of concept for the potential use of mTOR inhibitors in ADPKD and conditions with aberrant cholangiocyte proliferation.

Cytoprotective effect of lithium against spontaneous and induced apoptosis of lymphoid cell line MOLT-4

Lithium (Li) is still useful in the treatment of bipolar disorder. Cellular mechanisms of Li action are not fully understood and include some cytoprotective properties. Data concerning Li effect on the apoptotic mechanisms in cells other than neurons are fragmentary and contradictory. We have investigated anti-apoptotic activity of Li in a lymphoid derived MOLT-4 cell line. Spontaneous and camptothecin-induced apoptosis was analyzed in cells treated with 0-20 mM Li carbonate. Early apoptosis was identified as significant mitochondrial depolarization (JC-1 staining). Later stages of apoptosis were estimated with annexin V binding and by the proportion of cells containing sub-G1 amounts of DNA (PI staining). We have observed a biphasic effect of Li on the proportion of spontaneously apoptotic cells;namely, low (therapeutic) concentrations of Li had a significant effect stabilizing the mitochondrial membrane polarization, while 10 and 20mM Li increased apoptosis. The latter could be seen both as mitochondrial depolarization as well as an increased proportion of sub-G1 cells, accompanied by reduced proportion of S phase cells. Li at concentrations above 2 mM had a significant, dose-dependent, anti-apoptotic effect on the cells undergoing camptothecin induced apoptosis. In conclusion, demonstrated cytoprotective effect of Li is at least partially related to stabilization of mitochondrial membrane potential and to the reduction of DNA damaging effects in proliferating cells; both may form part of the mechanism through which Li is useful in therapy of bipolar disorder, but may have more general consequences.