Gamma (γ) tocopherol upregulates peroxisome proliferator activated receptor (PPAR) gamma (γ) expression in SW 480 human colon cancer cell lines

Background  

Tocopherols are lipid soluble antioxidants that exist as eight structurally different isoforms. The intake of γ-tocopherol is higher than α-tocopherol in the average US diet. The clinical results of the effects of vitamin E as a cancer preventive agent have been inconsistent. All published clinical trials with vitamin E have used α-tocopherol. Recent epidemiological, experimental and molecular studies suggest that γ-tocopherol may be a more potent chemopreventive form of vitamin E compared to the more-studied α-tocopherol. γ-Tocopherol exhibits differences in its ability to detoxify nitrogen dioxide, growth inhibitory effects on selected cancer cell lines, inhibition of neoplastic transformation in embryonic fibroblasts, and inhibition of cyclooxygenase-2 (COX-2) activity in macrophages and epithelial cells. Peroxisome proliferator activator receptor γ (PPARγ) is a promising molecular target for colon cancer prevention. Upregulation of PPARγ activity is anticarcinogenic through its effects on downstream genes that affect cellular proliferation and apoptosis. The thiazolidine class of drugs are powerful PPARγ ligands. Vitamin E has structural similarity to the thiazolidine, troglitazone. In this investigation, we tested the effects of both α and γ tocopherol on the expression of PPARγ mRNA and protein in SW 480 colon cancer cell lines. We also measured the intracellular concentrations of vitamin E in SW 480 colon cancer cell lines.     

Integrin α6Bβ4 inhibits colon cancer cell proliferation and c-Myc activity

Background  

Integrins are known to be important contributors to cancer progression. We have previously shown that the integrin β4 subunit is up-regulated in primary colon cancer. Its partner, the integrin α6 subunit, exists as two different mRNA splice variants, α6A and α6B, that differ in their cytoplasmic domains but evidence for distinct biological functions of these α6 splice variants is still lacking.     

USP35 activated by miR let-7a inhibits cell proliferation and NF-κB activation through stabilization of ABIN-2

Ubiquitin specific protease 35 (USP35) is a member of deubiquitylases (DUBs). It remains largely unknown about the biological role and the regulation mechanism of USP35. Here, we first identified miR let-7a as a positive regulator of USP35 expression and showed that USP35 expression positively correlates with miR let-7a expression in different cancer cell lines and tissues. Then, we showed that USP35 expression was decreased dramatically in the tumor tissues compared with the adjacent non-cancerous tissues. USP35 overexpression inhibited cell proliferation in vitro and inhibited xenograft tumor growth in vivo. Furthermore, we revealed that USP35 acts as a functional DUB and stabilizes TNFAIP3 interacting protein 2 (ABIN-2) by promoting its deubiquitination. Functionally, both ABIN-2 and USP35 could inhibit TNFα-induced NF-κB activation and overexpression of ABIN-2 alleviated USP35-loss induced activation of NF-κB. Collectively, our data indicated that miR let-7a-regulated USP35 can inhibit NF-κB activation by deubiquitination and stabilization of ABIN-2 protein and eventually inhibit cell proliferation. Overall, our study provides a novel rationale of targeting miR let-7a-USP35-ABIN-2 pathway for the therapy of cancer patients.     

Inhibition of COX-2 and activation of peroxisome proliferator-activated receptor γ synergistically inhibits proliferation and induces apoptosis of human pancreatic carcinoma cells

Although inhibition of cyclooxygenase-2 (COX-2) or activation of peroxisome proliferators-activated receptor γ (PPAR-γ) leads to growth inhibition in malignancies, the synergistic anti-tumor effects of combination of COX-2 inhibitor (NS-398) and PPAR-γ agonist (rosiglitazone) on the human pancreatic cancer cells remains unknown. Here, we evaluated the effects of NS-398 and/or rosiglitazone on the cell proliferation and apoptosis in a pancreatic cancer cell line, SW1990. NS-398 and rosiglitazone decreased cell proliferation in a dose- and time-dependent manner. Proliferating cell nuclear antigen (PCNA) labeling index significantly decreased in the cells treated with either NS-398 or rosiglitazone. Both NS-398 and rosiglitazone alone induced apoptotic cell death of SW1990. The combination of NS-398 and rosiglitazone exerted synergistic effects on proliferation inhibition, and apoptosis induction in SW1990 cells, with down-regulation of Bcl-2 and up-regulation of Bax expression. Our results indicate that simultaneous targeting of COX-2 and PPAR-γ inhibits pancreatic cancer development more effectively than targeting each molecule alone.     

CARMA3 overexpression accelerates cell proliferation and inhibits paclitaxel-induced apoptosis through NF-κB regulation in breast cancer cells

CARMA3 was recently reported to be overexpressed in several cancers and associated with malignant behavior of cancer cells. However, the expression pattern and biological roles of CARMA3 in breast cancer have not been reported. In the present study, we found that CARMA3 was overexpressed in 41.9 % of breast cancer specimens. Significant association was observed between CARMA3 overexpression and TNM stage (p?=?0.0223), tumor size (p?=?0.0227), and ErbB-2 status (p?=?0.0049). Furthermore, knockdown of CARMA3 expression in MDA-MB-435 cells with high endogenous expression decreased cell proliferation and sensitized cell to paclitaxel-induced apoptosis, while overexpression of CARMA3 in MDA-MB-231 cell line promoted cell proliferation and inhibited apoptosis. Further analysis showed that CARMA3 depletion downregulated, and its overexpression upregulated cyclin D1, Bcl-2, and p-IκB levels. In conclusion, our study demonstrated that CARMA3 is overexpressed in breast cancers. CARMA3 facilitates proliferation and inhibits apoptosis through nuclear factor-kappaB signaling.     

Pin1 promotes prostate cancer cell proliferation and migration through activation of Wnt/β-catenin signaling

Background

Recent evidence suggests that the peptidyl-prolyl isomerase Pin1 is an oncoprotein that acts as a novel therapeutic target in a variety of tumors. In this study, we investigated the clinical significance of Pin1 and its function in prostate cancer (PCa) tumor progression.

Methods

Immunohistochemical and quantitative RT-PCR analyses were performed to detect the expression of Pin1 in 86 PCa tissue samples. The functional role of Pin1 was evaluated by small interfering RNA-mediated depletion in PCa cells followed by analyses of cell proliferation and migration. Furthermore, the association between expression of Pin1 and levels of β-catenin and cyclin D1 was also evaluated.

Results

Our results showed that the high expression of Pin1 staining was 66 of 86 (76.74 %) PCa samples, and in 25 of 86 (29.07 %) BPH tissues, the difference was statistically significant (P < 0.001). Pin1 was significantly elevated in all PCa cell lines when compared to the normal RWPE-1 cells. We observed that proliferation and migration of LNCaP cells were inhibited by Pin1 knockdown. The levels of β-catenin and cyclin D1 in clinical PCa specimens were positively associated with Pin1 expression.

Conclusions

Our results suggest that Pin1 plays an important role in tumorigenesis of PCa, suggesting that targeting Pin1 pathway could represent a potential modality for treating PCa.

     

Targeting cytosolic phospholipase A2 α in colorectal cancer cells inhibits constitutively activated protein kinase B (AKT) and cell proliferation

A constitutive activation of protein kinase B (AKT) in a hyper-phosphorylated status at Ser⁴⁷³ is one of the hallmarks of anti-EGFR therapy-resistant colorectal cancer (CRC). The aim of this study was to examine the role of cytosolic phospholipase A₂α (cPLA₂α) on AKT phosphorylation at Ser⁴⁷³ and cell proliferation in CRC cells with mutation in phosphoinositide 3-kinase (PI3K). AKT phosphorylation at Ser⁴⁷³ was resistant to EGF stimulation in CRC cell lines of DLD-1 (PIK3CA^E545K mutation) and HT-29 (PIK3CA^P499T mutation). Over-expression of cPLA₂α by stable transfection increased basal and EGF-stimulated AKT phosphorylation and proliferation in DLD-1 cells. In contrast, silencing of cPLA₂α with siRNA or inhibition with Efipladib decreased basal and EGF-stimulated AKT phosphorylation and proliferation in HT-29. Treating animals transplanted with DLD-1 with Efipladib (10 mg/kg, i.p. daily) over 14 days reduced xenograft growth by >90% with a concomitant decrease in AKT phosphorylation. In human CRC tissue, cPLA₂α expression and phosphorylation were increased in 63% (77/120) compared with adjacent normal mucosa determined by immunohistochemistry. We conclude that cPLA₂α is required for sustaining AKT phosphorylation at Ser⁴⁷³ and cell proliferation in CRC cells with PI3K mutation, and may serve as a potential therapeutic target for treatment of CRC resistant to anti-EGFR therapy.     

Celastrol inhibits the growth of estrogen positive human breast cancer cells through modulation of estrogen receptor α

We studied the chemopreventive efficacy of indole-3-carbinol (I3C), a phytochemical found in cruciferous vegetables, to inhibit tobacco carcinogen-induced lung adenocarcinoma in A/J mice when given following post-initiation or progression protocol. Moreover, we assessed the potential mechanisms responsible for the anticancer effects of I3C. Post-initiation administration of I3C decreased the multiplicity of surface tumors as well as all forms of histopathological lesions, including adenocarcinoma, whereas administration of the compound during tumor progression failed to decrease the multiplicity of surface tumors and early forms of microscopic lesions but reduced the frequency of adenocarcinoma. Mechanistic studies in A549 lung adenocarcinoma cells indicated that the lung cancer preventive effects of I3C are mediated, at least in part, via modulation of the receptor tyrosine kinase/PI3K/Akt signaling pathway.     

PTHrP promotes colon cancer cell migration and invasion in an integrin α6β4-dependent manner through activation of Rac1

Parathyroid hormone-related protein (PTHrP) is expressed by human colon cancer tissue and cell lines. Rac1 GTPase enhances colon cancer cell migration and invasion. Here we report a positive correlation between PTHrP expression and Rac1 activity in LoVo (human colon cancer) cells. The positive effects of PTHrP on Rac1 activity and on cell migration and invasion are mediated via the guanine nucleotide exchange factor Tiam1. Knockdown of integrin α6β4, which is upregulated by PTHrP, negates the PTHrP-mediated increase in Rac1 activation. Integrin α6β4 signals synergistically with growth factor receptors to activate the phosphatidylinositol 3-kinase (PI3-K) pathway. Chemical inhibition of PI3-K negates the PTHrP-mediated effects on Tiam1 and Rac1 activity. Tumors from PTHrP-overexpressing LoVo cells also show increased expression of Tiam1. Taken together, these observations provide evidence of a link between PTHrP and Rac1 activity through integrin α6β4, resulting in enhanced cell migration and invasion. Targeting PTHrP production in colon cancer may thus prove therapeutically beneficial.     

Re-expression of estrogen receptor β inhibits the proliferation and migration of ovarian clear cell adenocarcinoma cells

Ovarian clear cell adenocarcinoma (OCCA) is an aggressive ovarian malignancy with a poor prognosis. The role of estrogen receptor β (ERβ) in the development of OCCA remains to be clarified. To investigate the action of ERβ in the proliferation and invasion of OCCA cells, the ES-2 cell line was stably transfected with full-length human ERβ cDNA, and clones were screened and identified using RT-PCR and western blot assay. ERβ stable transfectants, referred to as ESβ1 and ESβ2 cells, were compared with mock transfectant ESVE and parental ES-2 cells with respect to their growth, motility and ability to activate target genes. ESβ1 and ESβ2 cells expressed ERβ mRNA and protein, whereas ES-2 and ESVE cells were ERβ negative. ERβ transfectants exhibited distinct characteristics from ES-2 and ESVE cells including proliferative properties and the ability to express cyclin D1 in the presence of 17β-estradiol (E2). ERβ inhibited ES-2 cell proliferation, which was determined using the MTT assay, BrdU labeling method and by the down-regulation of cyclin D1 gene expression. Moreover, exogenous ERβ expression resulted in a significant inhibition of ES-2 cell motility in an in?vitro invasion assay. ERβ reduced the expression of MMP2 mRNA and the activity of MMP2 enzymatic activity in a ligand-dependent manner. In summary, ERβ may inhibit the proliferation and invasion of ES-2 cells and may be an important regulator in OCCA carcinogenesis.     

Interferon-β inhibits proliferation and progression through S phase of the cell cycle in five glioma cell lines

Summary The growth inhibitory effect of IFN- was evaluated in 5 human glioma cell lines (AO2V4, GJC, GJR, NN and NNR) and in normal astrocyte cultures (SC and TM). All 5 glioma cell lines showed an anti-proliferative response to IFN- whereas normal glial cells were non-responsive. IFN- at 10, 100 and 500 U/ml lead to a 30%,70% and 80% relative decrease in cell number after 12 days, respectively in AO2V4 cells. GJC and GJR cell lines also responded significantly to the lowest concentration of IFN- tested and at 500 U/ml the relative cell number decreased 55%. The NN and NNR cells were the least responsive to IFN- with maximum growth inhibition of 30% at 500 U IFN-/ml. Following treatment with IFN-, AO2V4, GJC, GJR and normal astrocytes all expressed mRNA encoding the anti-viral protein, 2-5A synthetase demonstrating that IFN- bound to receptors on all four cell lines and activated signal transduction pathways required for induction of an anti-viral protein. A determination of the relative number of viable cells showed that none of these cells exhibited a significant decrease in cell viability. Since the antiproliferative response to IFN- was not primarily due to cell death, the effect of IFN- on cell cycle progression was evaluated by flow cytometry. All treated glioma cell lines showed a relative increase in proportion of cells in S phase. AO2V4 cells had a 50%–80% increase in the percentage of cells in S phase, whereas GJC, GJR and NNR had percentage increases of 20%–40%. IFN- treatment of normal astrocytes did not significantly alter their cell cycle profile. These data suggest that IFN- exerts its antiproliferative effect on glioma cells by arresting the ordered progression through S phase or decreasing entry into G₂/M phase of the cell cycle.     

Investigation of the mechanisms of coagulation factor Ⅶa-induced colon cancer 8W620 cell proliferation and migration

Objective To investigate the mechanisms that coagulation factor Ⅶa promotes proliferation and migration of a colon cancer cell line (SW620 cells) in vitro. Methods The expression of interleukin 8 (IL-8), tissue factor (TF), caspase-7 and p-p38 MAPK in SW620 cells treated with factor Ⅶa or protease activated receptor 2 aganist (PAR2-AP) was measured by ELISA, Western-blotting and QT-PCR. Results Factor Ⅶa and PAR2-AP induced IL-8 expression at both mRNA and protein levels, up-regulated TF mRNA expression and TF activity, but down-regulated caspese-7 mRNA and p-p38 MAPK levels in SW620 cells. The effects of factor Ⅶa were not only blocked by anti-TF but also by anti-PAR2 antibodies. Conclusion Factor Ⅶa binds to TF on cell surface, forming a complex which activates PAR2, then provoking IL-8 and TF expression, and suppresses caepase-7 expression, thus promotes the tumor cell proliferation and migration, p38 MAPK may negatively regulate this process.