Novel targeted pro-apoptotic agents for the treatment of prostate cancer

ZWINT is the next potential target for lung cancer therapy

PURPOSE

We aimed to analyze the expression of ZWINT, NUSAP1, DLGAP5, and PRC1 in tumor tissues and adjacent tissues with public data.

METHODS

The expression patterns of four genes were detected in cancer tissues and adjacent tissues by qRT-PCR. The overall survival analysis was used to explore these genes in lung adenocarcinoma and squamous cell carcinoma patients. Knockdown assays were used to select the most suitable gene among these four genes. Cell function assays with the knockdown gene were conducted in A549 and NCL H226 cells. The role of the knockdown gene in lung cancer was dissected in a mice tumor model. Transcriptome sequencing analyses with the knockdown gene were analyzed.

RESULTS

Overexpression of these genes was significantly detected in cancer tissues (P < 0.01). Overall survival revealed that high expression of these genes is closely related with poor prognosis of lung adenocarcinoma patients (P < 0.05). Knockdown of ZWINT reduced proliferation in NCI H226 and A549 cells (P < 0.05). Knockdown also inhibited cell migration, invasion, apoptosis, and colony formation (P < 0.05). ZWINT knockdown reduced tumor volume (P < 0.05). Transcriptome sequencing of ZWINT knockdown-treated A549 and NCI H226 cells indicated that 100 and 426 differentially expressed genes were obtained, respectively. Gene ontology analysis suggested that binding, biological regulation, and multicellular organismal processes were the most enriched. KEGG analysis revealed that TNF, P53, and PI3K signal networks would be the most potential ZWINT-related pathways and were identified by Western blot analysis.

CONCLUSIONS

ZWINT may be a novel target for lung cancer therapy.

SOX2 regulates apoptosis through MAP4K4-survivin signaling pathway in human lung cancer cells

Previous studies have implicated cancer stem cells in tumor recurrence and revealed that the stem cell gene SOX2 plays an important role in the tumor cell resistance to apoptosis. Nonetheless, the mechanism by which SOX2 regulates apoptosis signals remained undefined. Here, we demonstrated the surprising finding that silencing of the SOX2 gene effectively induces apoptosis via the activation of death receptor and mitochondrial signaling pathways in human non-small cell lung cancer cells. Unexpectedly, reverse transcription-PCR analysis suggested that downregulation of SOX2 leads to activation of MAP4K4, previously implicated in cell survival. Evaluation of the apoptotic pathways revealed an increased expression of key inducers of apoptosis, including tumor necrosis factor-α and p53, with concurrent attenuation of Survivin. Although p53 appeared dispensable for this pathway, the loss of Survivin in SOX2-deficient cells appeared critical for the observed MAP4K4 induced cell death. Rescue experiments revealed that SOX2-silencing-mediated killing was blocked by ectopic expression of Survivin, or by reduction of MAP4K4 expression. Clinically, expressions of Survivin and SOX2 were highly correlated with each other. The results reveal a key target of SOX2 expression and highlight the unexpected context-dependent role for MAP4K4, a pluripotent activator of several mitogen-activated protein kinase pathways, in regulating tumor cell survival.

Correlation between mitochondrial TRAP-1 expression and lymph node metastasis in colorectal cancer

AIM: To evaluate the effect of mitochondrial tumor necrosis factor receptor-associated protein-1 (TRAP-1) on the lymph node metastasis (LNM) in Chinese colorectal cancer (CRC) patients, and develop potential LNM-associated biomarkers for CRC using quantitative real-time polymerase chain reaction (RT-PCR) analysis.

METHODS: Differences in mitochondrial TRAP-1 gene expression between primary CRC with LNM (LNM CRC) and without LNM (non-LNM CRC) were assessed in 96 Chinese colorectal carcinoma samples using quantitative RT-PCR analysis, Western blotting, and confirmed with immunohistochemical assay. The relationship between clinicopathological parameters and potential diagnostic biomarkers was also examined.

RESULTS: TRAP-1 was significantly upregulated in LNM CRC compared with non-LNM CRC, which was confirmed by RT-PCR, Western blotting and immunohistochemical assay. The expression of TRAP-1 in two different metastatic potential human colorectal cancer cell lines, LoVo and HT29, was analyzed with Western blotting. The expression level of TRAP-1 was dramatically higher in LoVo than in HT29. Overexpression of TRAP-1 was significantly associated with LNM (90.2% in LNM group vs 22% in non-LNM group, P < 0.001), the advanced tumor node metastasis stage (89.1% in LNM group vs 26.9% in non-LNM group, P < 0.001), the increased 5-year recurrence rate (82.7% in LNM group vs 22.6% in non-LNM group, P < 0.001) and the decreased 5-year overall survival rate (48.4% in LNM vs 83.2% in non-LNM group, P < 0.001). Univariate and multivariate analyses indicated that TRAP-1 expression was an independent prognostic factor for recurrence and survival of CRC patients (Hazard ratio of 2.445 in recurrence, P = 0.017; 2.867 in survival, P = 0.028).

CONCLUSION: Mitochondria TRAP-1 affects the lymph node metastasis in CRC, and may be a potential biomarker for LNM and a prognostic factor in CRC. Over-expression of TRAP-1 is a predictive factor for the poor outcome of colorectal cancer patients.

Cellular signal transduction can be induced by TRAIL conjugated to microcapsules

The extracellular agent tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) can induce apoptosis in tumor cells but spare normal cells. Ligation of TRAIL to a nanoparticle would serve to facilitate targeting to an extravascular site. Polymeric ultrasound contrast agents (UCA) (microencapsulated gas bubbles) can be tracked by ultrasound imaging, and fragmented into nanoparticles by focused ultrasound. This tumor-targeted delivery system has been shown to deliver more efficiently than solid nanoparticles. Additionally, small molecule inhibitors such as bortezomib, shown to sensitize TRAIL-resistant cells, could be co-administered within these UCA. In this pilot study, TRAIL was conjugated to UCA while preserving the agent's sensitivity to ultrasound. Human cancer cell lines, OVCAR-3 and A2058, were bathed with the TRAIL-UCA with and without the addition of bortezomib. Apoptosis was quantified using flow cytometry. OVCAR-3 treated with TRAIL-UCA exhibit significant (p < 0.05) apoptotosis compared to unmodified UCA, equal to positive controls, but no synergistic effect when combined with bortezomib. A2058 cells treated with TRAIL-UCA also exhibited significant apoptosis (p < 0.01) compared to unmodified UCA, similar to positive controls and bortezomib significantly increased apoptosis in combination with TRAIL-UCA. We conclude that TRAIL-ligated UCA show exciting potential as a new therapy.

Enhanced TRAIL-mediated apoptosis in prostate cancer cells by the bioactive compounds neobavaisoflavone and psoralidin isolated from Psoralea corylifolia

Numerous compounds detected in medical plants and dietary components or supplements possess chemopreventive, antitumor and immunomodulatory properties. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is an important endogenous anticancer factor that induces apoptosis selectively in cancer cells. However, some tumor cells are resistant to TRAIL-mediated apoptosis. Naturally occurring agents could sensitize TRAIL-resistant cancer cells and augment their apoptotic activity.We examined the cytotoxic and apoptotic effects of neobavaisoflavone and psoralidin in combination with TRAIL on LNCaP prostate cancer cells. The cytotoxicity was evaluated by MTT and LDH assays. The apoptosis was detected using Annexin V-FITC by flow cytometry and fluorescence microscopy. The LNCaP cells were shown to be resistant to TRAIL-induced apoptosis. Our study demonstrated that neobavaisoflavone and psoralidin sensitized TRAIL-resistant cells and markedly augmented TRAIL-mediated apoptosis and cytotoxicity in prostate cancer cells. Cotreatment of LNCaP cells with 100 ng/ml TRAIL and 50 μM neobavaisoflavone or 50 μM psoralidin increased the percentage of the apoptotic cells to 77.5±0.5% or 64.4±0.5%, respectively. The data indicate the potential role of the bioactive compounds isolated from the medicinal plant Psoralea corylifolia (neobavaisoflavone and psoralidin) in prostate cancer chemoprevention through enhancement of TRAIL-mediated apoptosis.

AT-101 (R-(-)-gossypol acetic acid) enhances the effectiveness of androgen deprivation therapy in the VCaP prostate cancer model

Prostate cancer remains a leading cause of cancer death in American men. Androgen deprivation therapy (ADT) is the most common treatment for advanced prostate cancer patients; however, ADT fails in nearly all cases resulting in castration resistant or androgen-insensitive (AI) disease. In many cases, this progression results from dysregulation of the pro-survival Bcl-2 family proteins. Inhibition of pro-survival Bcl-2 family proteins, therefore, may be an effective strategy to delay the onset of AI disease. Gossypol, a small molecule inhibitor of pro-survival Bcl-2 family proteins, has been demonstrated to inhibit AI prostate cancer growth. The apoptotic effect of gossypol, however, has been demonstrated to be attenuated by the presence of androgen in a prostate cancer xenograft mouse model (Vertebral Cancer of Prostate [VCaP]) treated with AT-101 (R-(-)-gossypol acetic acid). This study was undertaken to better understand the in vitro effects of androgen receptor (AR) on AT-101-induced apoptosis. VCaP cells treated with AT-101 demonstrated an increase in apoptosis and downregulation of Bcl-2 pro-survival proteins. Upon AR activation in combination with AT-101 treatment, apoptosis is reduced, cell survival increases, and caspase activation is attenuated. Akt and X inhibitor of apoptosis (XIAP) are downregulated in the presence of AT-101, and AR stimulation rescues protein expression. Combination treatment of bicalutamide and AT-101 increases apoptosis by reducing the expression of these pro-survival proteins. These data suggest that combination therapy of AT-101 and ADT may further delay the onset of AI disease, resulting in prolonged progression-free survival of prostate cancer patients.

Preclinical characterization of mitochondria-targeted small molecule hsp90 inhibitors, gamitrinibs, in advanced prostate cancer

PURPOSE

This study aimed to characterize the preclinical activity of the first class of combinatorial, mitochondria-targeted, small molecule heat shock protein-90 (Hsp90) inhibitors, gamitrinibs, in models of hormone-refractory, drug-resistant, localized, and bone metastatic prostate cancer in vivo.

EXPERIMENTAL DESIGN

Mitochondrial permeability transition, apoptosis, and changes in metabolic activity were examined by time-lapse videomicroscopy, multiparametric flow cytometry, MTT, and analysis of isolated mitochondria. Drug-resistant prostate cancer cells were generated by chronic exposure of hormone-refractory PC3 cells to the Hsp90 inhibitor 17-allylaminogeldanamycin (17-AAG). The effect of gamitrinibs on s.c. or intratibial prostate cancer growth was studied in xenograft models. Bone metastatic tumor growth and bone parameters were quantified by micro-computed tomography imaging.

RESULTS

In the NCI 60-cell line screening, gamitrinibs were active against all tumor cell types tested, and efficiently killed metastatic, hormone-refractory, and multidrug-resistant prostate cancer cells characterized by overexpression of the ATP binding cassette transporter P-glycoprotein. Mechanistically, gamitrinibs, but not 17-AAG, induced acute mitochondrial dysfunction in prostate cancer cells with loss of organelle membrane potential, release of cytochrome c, and caspase activity, independently of proapoptotic Bcl-2 proteins Bax and Bak. Systemic administration of gamitrinibs to mice was well tolerated, and inhibited s.c. or bone metastatic prostate cancer growth in vivo.

CONCLUSIONS

Gamitrinibs have preclinical activity and favorable safety in models of drug-resistant and bone metastatic prostate cancer in vivo.

Cytoprotective mitochondrial chaperone TRAP-1 as a novel molecular target in localized and metastatic prostate cancer

Molecular chaperones of the heat shock protein-90 (Hsp90) family promote cell survival, but the molecular requirements of this pathway in tumor progression are not understood. Here, we show that a mitochondria-localized Hsp90 chaperone, tumor necrosis factor receptor-associated protein-1 (TRAP-1), is abundantly and ubiquitously expressed in human high-grade prostatic intraepithelial neoplasia, Gleason grades 3 through 5 prostatic adenocarcinomas, and metastatic prostate cancer, but largely undetectable in normal prostate or benign prostatic hyperplasia in vivo. Prostate lesions formed in genetic models of the disease, including the transgenic adenocarcinoma of the mouse prostate and mice carrying prostate-specific deletion of the phosphatase tensin homolog tumor suppressor (Pten(pc-/-)), also exhibit high levels of TRAP-1. Expression of TRAP-1 in nontransformed prostatic epithelial BPH-1 cells inhibited cell death, whereas silencing of TRAP-1 in androgen-independent PC3 or DU145 prostate cancer cells by small interfering RNA enhanced apoptosis. Targeting TRAP-1 with a novel class of mitochondria-directed Hsp90 inhibitors, ie, Gamitrinibs, caused rapid and complete killing of androgen-dependent or -independent prostate cancer, but not BPH-1 cells, whereas reintroduction of TRAP-1 in BPH-1 cells conferred sensitivity to Gamitrinib-induced cell death. These data identify TRAP-1 as a novel mitochondrial survival factor differentially expressed in localized and metastatic prostate cancer compared with normal prostate. Targeting this pathway with Gamitrinibs could be explored as novel molecular therapy in patients with advanced prostate cancer.

Emerging drugs for prostate cancer

Prostate cancer mortality usually occurs as a result of castrate resistant disease. Many approaches are currently being evaluated to improve the treatment of this condition. These include drugs that induce androgen deprivation, that is, LHRH antagonists; more active or less toxic chemotherapy agents; immunologic approaches, including passive and active immunization; drugs that target the androgen receptor and/or androgen synthesis; drugs that target specific pathways, including tyrosine kinase inhibitors, angiogenesis inhibitors, endothelin antagonists and matrix metalloproteinase inhibitors; and antioxidants and cell cycle inhibitors. Many of these agents seem promising. The rationale, biologic activity and therapeutic results of these emerging drugs are reviewed.

Fatty acid synthase: a metabolic enzyme and candidate oncogene in prostate cancer

BACKGROUND

Overexpression of the fatty acid synthase (FASN) gene has been implicated in prostate carcinogenesis. We sought to directly assess the oncogenic potential of FASN.

METHODS

We used immortalized human prostate epithelial cells (iPrECs), androgen receptor-overexpressing iPrECs (AR-iPrEC), and human prostate adenocarcinoma LNCaP cells that stably overexpressed FASN for cell proliferation assays, soft agar assays, and tests of tumor formation in immunodeficient mice. Transgenic mice expressing FASN in the prostate were generated to assess the effects of FASN on prostate histology. Apoptosis was evaluated by Hoechst 33342 staining and by fluorescence-activated cell sorting in iPrEC-FASN cells treated with stimulators of the intrinsic and extrinsic pathways of apoptosis (ie, camptothecin and anti-Fas antibody, respectively) or with a small interfering RNA (siRNA) targeting FASN. FASN expression was compared with the apoptotic index assessed by the terminal deoxynucleotidyltransferase-mediated UTP end-labeling method in 745 human prostate cancer samples by using the least squares means procedure. All statistical tests were two-sided.

RESULTS

Forced expression of FASN in iPrECs, AR-iPrECs, and LNCaP cells increased cell proliferation and soft agar growth. iPrECs that expressed both FASN and androgen receptor (AR) formed invasive adenocarcinomas in immunodeficient mice (12 of 14 mice injected formed tumors vs 0 of 14 mice injected with AR-iPrEC expressing empty vector (P < .001, Fisher exact test); however, iPrECs that expressed only FASN did not. Transgenic expression of FASN in mice resulted in prostate intraepithelial neoplasia, the incidence of which increased from 10% in 8- to 16-week-old mice to 44% in mice aged 7 months or more (P = .0028, Fisher exact test), but not in invasive tumors. In LNCaP cells, siRNA-mediated silencing of FASN resulted in apoptosis. FASN overexpression protected iPrECs from apoptosis induced by camptothecin but did not protect iPrECs from Fas receptor-induced apoptosis. In human prostate cancer specimens, FASN expression was inversely associated with the apoptotic rate (mean percentage of apoptotic cells, lowest vs highest quartile of FASN expression: 2.76 vs 1.34, difference = 1.41, 95% confidence interval = 0.45 to 2.39, Ptrend = .0046).

CONCLUSIONS

These observations suggest that FASN can act as a prostate cancer oncogene in the presence of AR and that FASN exerts its oncogenic effect by inhibiting the intrinsic pathway of apoptosis.

Sulforaphane inhibited expression of hypoxia-inducible factor-1alpha in human tongue squamous cancer cells and prostate cancer cells

Previous studies show that a number of natural compounds from our diet have anticancer effects. Sulforaphane is the most characterized isothiocyanates (ITCs), which are identified in cruciferous vegetables. Sulforaphane is viewed as a conceptually promising agent in cancer prevention. Because of its ability to induce cancer cell apoptosis, it inhibits progression of benign tumors to malignant tumors and interrupts metastasis. However, the effect of sulforaphane on tongue cancer cell proliferation has not yet been reported, and the mechanisms that sulforaphane inhibits cancer development are still unclear. Hypoxia-inducible factor 1 (HIF-1) expression is associated with tumorigenesis and angiogenesis. It regulates the expression of many genes including vascular endothelial growth factor (VEGF), inducible nitric oxide synthase, and lactate dehydrogenase A. In our study, we investigated the effects of sulforaphane on expression of hypoxia-inducible factor-1alpha (HIF-1alpha), which was overexpressed in many human malignant tumors, human tongue squamous cell carcinoma and prostate cancer DU145 cells. Sulforaphane inhibited hypoxia induced expression of HIF-1alpha via inhibiting synthesis of HIF-1alpha. Sulforaphane was also found to inhibit hypoxia induced HIF-1alpha expression through activating JNK and ERK signaling pathways, but not AKT pathway. Inhibition of HIF-1alpha by sulforaphane resulted in decreasing expression of VEGF. Taken together, these results suggest that sulforaphane is an effective chemopreventive compound against tongue cancers and prostate cell angiogenesis in vitro, and that the HIF-1alpha target provides a new sight into the mechanisms of sulforaphane's inhibition against tumor cell proliferation.