Sp1 Plays a Key Role in Vasculogenic Mimicry of Human Prostate Cancer Cells

Sp1 transcription factor regulates genes involved in various phenomena of tumor progression. Vasculogenic mimicry (VM) is the alternative neovascularization by aggressive tumor cells. However, there is no evidence of the relationship between Sp1 and VM. This study investigated whether and how Sp1 plays a crucial role in the process of VM in human prostate cancer (PCa) cell lines, PC-3 and DU145. A cell viability assay and three-dimensional culture VM tube formation assay were performed. Protein and mRNA expression levels were detected by Western blot and reverse transcriptase-polymerase chain reaction, respectively. The nuclear twist expression was observed by immunofluorescence assay. A co-immunoprecipitation assay was performed. Mithramycin A (MiA) and Sp1 siRNA significantly decreased serum-induced VM, whereas Sp1 overexpression caused a significant induction of VM. Serum-upregulated vascular endothelial cadherin (VE-cadherin) protein and mRNA expression levels were decreased after MiA treatment or Sp1 silencing. The protein expression and the nuclear localization of twist were increased by serum, which was effectively inhibited after MiA treatment or Sp1 silencing. The interaction between Sp1 and twist was reduced by MiA. On the contrary, Sp1 overexpression enhanced VE-cadherin and twist expressions. Serum phosphorylated AKT and raised matrix metalloproteinase-2 (MMP-2) and laminin subunit 5 gamma-2 (LAMC2) expressions. MiA or Sp1 silencing impaired these effects. However, Sp1 overexpression upregulated phosphor-AKT, MMP-2 and LAMC2 expressions. Serum-upregulated Sp1 was significantly reduced by an AKT inhibitor, wortmannin. These results demonstrate that Sp1 mediates VM formation through interacting with the twist/VE-cadherin/AKT pathway in human PCa cells.

Anti-Angiogenic and Anti-Proliferative Graphene Oxide Nanosheets for Tumor Cell Therapy

Graphene oxide (GO) is a bidimensional novel material that exhibits high biocompatibility and angiogenic properties, mostly related to the intracellular formation of reactive oxygen species (ROS). In this work, we set up an experimental methodology for the fabrication of GO@peptide hybrids by the immobilization, via irreversible physical adsorption, of the Ac-(GHHPH)₄-NH₂ peptide sequence, known to mimic the anti-angiogenic domain of the histidine-proline-rich glycoprotein (HPRG). The anti-proliferative capability of the graphene-peptide hybrids were tested in vitro by viability assays on prostate cancer cells (PC-3 line), human neuroblastoma (SH-SY5Y), and human retinal endothelial cells (primary HREC). The anti-angiogenic response of the two cellular models of angiogenesis, namely endothelial and prostate cancer cells, was scrutinized by prostaglandin E2 (PGE₂) release and wound scratch assays, to correlate the activation of inflammatory response upon the cell treatments with the GO@peptide nanocomposites to the cell migration processes. Results showed that the GO@peptide nanoassemblies not only effectively induced toxicity in the prostate cancer cells, but also strongly blocked the cell migration and inhibited the prostaglandin-mediated inflammatory process both in PC-3 and in HRECs. Moreover, the cytotoxic mechanism and the internalization efficiency of the theranostic nanoplatforms, investigated by mitochondrial ROS production analyses and confocal microscopy imaging, unraveled a dose-dependent manifold mechanism of action performed by the hybrid nanoassemblies against the PC-3 cells, with the detection of the GO-characteristic cell wrapping and mitochondrial perturbation. The obtained results pointed out to the very promising potential of the synthetized graphene-based hybrids for cancer therapy.

Effect of Carvacrol on Ca²⁺ Movement and Viability in PC3 Human Prostate Cancer Cells

Carvacrol, a monoterpenic phenol compound, has been shown to possess various biological effects in different models. However, the effect of carvacrol on intracellular Ca²⁺ and its related physiology in human prostate cancer is unknown. This study explored the effect of carvacrol on cytosolic free Ca²⁺ levels ([Ca²⁺]i) and viability in PC3 human prostate cancer cells. Fura-2, a Ca²⁺- sensitive fluorescent dye, was used to assess [Ca²⁺]i. Cell viability was measured by the detecting reagent WST-1. Carvacrol at concentrations of 200-800 μM caused [Ca²⁺]i rises in a concentration-dependent manner. Removal of extracellular Ca²⁺ reduced carvacrol’s effect by approximately 60%. Carvacrol-induced Ca²⁺ entry was confirmed by Mn²⁺ entry-induced quench of fura-2 fluorescence, and was inhibited by approximately 30% by nifedipine, econazole, SKF96365, and the protein kinase C (PKC) inhibitor GF109203X. In Ca²⁺-free medium, treatment with the endoplasmic reticulum Ca²⁺ pump inhibitor thapsigargin (TG) abolished carvacrol-induced [Ca²⁺]i rises. Treatment with carvacrol also abolished TG-induced [Ca²⁺]i rises. Carvacrol-induced Ca²⁺ release from the endoplasmic reticulum was abolished by inhibition of phospholipase C (PLC). Carvacrol killed cells at concentrations of 200-600 μM in a concentration-dependent fashion. Chelating cytosolic Ca²⁺ with BAPTA/AM did not prevent carvacrol’s cytotoxicity. Together, in PC3 cells, carvacrol induced [Ca²⁺]i rises by inducing PLC-dependent Ca²⁺ release from the endoplasmic reticulum and Ca²⁺ entry via PKC-sensitive store-operated Ca²⁺ channels and other unknown channels. Carvacrol also induced Ca²⁺-dissociated cell death.

The investigation of minoxidil-induced [Ca2+]i rises and non-Ca2+-triggered cell death in PC3 human prostate cancer cells

Minoxidil is clinically used to prevent hair loss. However, its effect on Ca²⁺ homeostasis in prostate cancer cells is unclear. This study explored the effect of minoxidil on cytosolic-free Ca²⁺ levels ([Ca²⁺]_i) and cell viability in PC3 human prostate cancer cells. Minoxidil at concentrations between 200 and 800 μM evoked [Ca²⁺]_i rises in a concentration-dependent manner. This Ca²⁺ signal was inhibited by 60% by removal of extracellular Ca²⁺. Minoxidil-induced Ca²⁺ influx was confirmed by Mn²⁺-induced quench of fura-2 fluorescence. Pre-treatment with the protein kinase C (PKC) inhibitor GF109203X, PKC activator phorbol 12-myristate 13 acetate (PMA), nifedipine and SKF96365 inhibited minoxidil-induced Ca²⁺ signal in Ca²⁺ containing medium by 60%. Treatment with the endoplasmic reticulum Ca²⁺ pump inhibitor 2,5-ditert-butylhydroquinone (BHQ) in Ca²⁺-free medium abolished minoxidil-induced [Ca²⁺]_i rises. Conversely, treatment with minoxidil abolished BHQ-induced [Ca²⁺]_i rises. Inhibition of phospholipase C (PLC) with U73122 abolished minoxidil-evoked [Ca²⁺]_i rises. Overnight treatment with minoxidil killed cells at concentrations of 200-600 μM in a concentration-dependent fashion. Chelation of cytosolic Ca²⁺ with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid/AM (BAPTA/AM) did not prevent minoxidil's cytotoxicity. Together, in PC3 cells, minoxidil induced [Ca²⁺]_i rises that involved Ca²⁺ entry through PKC-regulated store-operated Ca²⁺ channels and PLC-dependent Ca²⁺ release from the endoplasmic reticulum. Minoxidil-induced cytotoxicity in a Ca²⁺-independent manner.

The mechanism of bifonazole-induced [Ca(2+)]i rises and non-Ca(2+)-triggered cell death in PC3 human prostate cancer cells

Bifonazole is an antifungal drug widely used for treating skin diseases. The effect of bifonazole on physiology of cancer cells is unclear. The effect of bifonazole on cytosolic free Ca(2+) concentrations ([Ca(2+)]i) and viability in PC3 human prostate cancer cells was explored. The Ca(2+)-sensitive fluorescent dye, fura-2, was applied to measure [Ca(2+)]i. Bifonazole at concentrations of 5-30 µM induced a [Ca(2+)]i rise in a concentration-dependent manner. The response was reduced by 50% by removing extracellular Ca(2+). Bifonazole-evoked [Ca(2+)]i rise was not altered by nifedipine, econazole, SK&F96365 and protein kinase C activator, but was inhibited by 75% by GF109203X, a protein kinase C inhibitor. In Ca(2+)-free medium, treatment with the endoplasmic reticulum Ca(2+) pump inhibitor 2,5-di-tert-butylhydroquinone (BHQ) nearly abolished bifonazole-evoked [Ca(2+)]i rise. Conversely, treatment with bifonazole abolished BHQ-evoked [Ca(2+)]i rise. Inhibition of phospholipase C with U73122 abolished bifonazole-induced [Ca(2+)]i rise. At 30-100 µM, bifonazole decreased cell viability concentration-dependently, which was not reversed by chelating cytosolic Ca(2+) with 1,2-bis(2-aminophenoxy)ethane-N,N,N″,N'-tetraacetic acid/acetoxy methyl. Annexin V/propidium iodide staining data suggest that bifonazole (30-100 µM) induced apoptosis concentration-dependently. Together, in PC3 human prostate cancer cells, bifonazole induced [Ca(2+)]i rises by inducing phospholipase C- and protein kinase C-dependent Ca(2+) release from the endoplasmic reticulum and Ca(2+) influx via non-store-operated pathways. Bifonazole induced cell death that might involve apoptosis.

The role of alpha(v)beta(3) in prostate cancer progression

Integrin alpha(v)beta(3) is involved in varied cell biological activities, including angiogenesis, cell adhesion, and migration on several extracellular matrix components. Although alpha(v)beta(3) is not typically expressed in epithelial cells, it is expressed in macrophages, activated leukocytes, cytokine-stimulated endothelial cells, osteoclasts, and certain invasive tumors. Interestingly, the adhesion and migration of breast cancer cells on bone matrix are mediated, in part, by alpha(v)beta(3). Similar to breast cancer cells, prostate cancer cells preferentially metastasize to the bone. The biological events that mediate this metastatic pattern of prostate cancer are not well defined. This review discusses the role alpha(v)beta(3) plays in prostate cancer progression, with specific emphasis on bone metastasis and on alpha(v)beta(3) signaling in prostate cancer cells. The data suggest that alpha(v)beta(3), in part, facilitates prostate cancer metastasis to bone by mediating prostate cancer cell adhesion to and migration on osteopontin and vitronectin, which are common proteins in the bone microenvironment. These biological events require the activation of focal adhesion kinase and the subsequent activation of PI-3 kinase/Akt signaling pathway.

The role of alpha(v)beta(3) in prostate cancer progression

Integrin alpha(v)beta(3) is involved in varied cell biological activities, including angiogenesis, cell adhesion, and migration on several extracellular matrix components. Although alpha(v)beta(3) is not typically expressed in epithelial cells, it is expressed in macrophages, activated leukocytes, cytokine-stimulated endothelial cells, osteoclasts, and certain invasive tumors. Interestingly, the adhesion and migration of breast cancer cells on bone matrix are mediated, in part, by alpha(v)beta(3). Similar to breast cancer cells, prostate cancer cells preferentially metastasize to the bone. The biological events that mediate this metastatic pattern of prostate cancer are not well defined. This review discusses the role alpha(v)beta(3) plays in prostate cancer progression, with specific emphasis on bone metastasis and on alpha(v)beta(3) signaling in prostate cancer cells. The data suggest that alpha(v)beta(3), in part, facilitates prostate cancer metastasis to bone by mediating prostate cancer cell adhesion to and migration on osteopontin and vitronectin, which are common proteins in the bone microenvironment. These biological events require the activation of focal adhesion kinase and the subsequent activation of PI-3 kinase/Akt signaling pathway.