Expression of Concern: Conjugation of substituted naphthalimides to polyamines as cytotoxic agents targeting the Akt/mTOR signal pathway.

Expression of Concern for 'Conjugation of substituted naphthalimides to polyamines as cytotoxic agents targeting the Akt/mTOR signal pathway' by Zhi-Yong Tian et al., Org. Biomol. Chem., 2009, 7, 4651-4660, https://doi.org/10.1039/B912685F.

Elevation of spermine remodels immunosuppressive microenvironment through driving the modification of PD-L1 in hepatocellular carcinoma.

BACKGROUND: Spermine is frequently elevated in tumor tissues and body fluids of cancer patients and is critical for cancer cell proliferation, migration and invasion. However, the immune functions of spermine in hepatocellular carcinoma progression remains unknown. In the present study, we aimed to elucidate immunosuppressive role of spermine in hepatocellular carcinoma and to explore the underlying mechanism. METHODS: Whole-blood spermine concentration was measured using HPLC. Human primary HCC tissues were collected to examine the expression of CaSR, p-Akt, ß-catenin, STT3A, PD-L1, and CD8. Mouse model of tumorigenesis and lung metastasis were established to evaluate the effects of spermine on hepatocellular carcinoma. Western blotting, immunofluorescence, real time PCR, digital Ca2+ imaging, and chromatin immunoprecipitation assay were used to investigate the underlying mechanisms by which spermine regulates PD-L1 expression and glycosylation in hepatocellular carcinoma cells. RESULTS: Blood spermine concentration in the HCC patient group was significantly higher than that in the normal population group. Spermine could facilitate tumor progression through inducing PD-L1 expression and decreasing the CD8+ T cell infiltration in HCC. Mechanistically, spermine activates calcium-sensing receptor (CaSR) to trigger Ca2+ entry and thereby promote Akt-dependent ß-catenin stabilization and nuclear translocation. Nuclear ß-catenin induced by spermine then activates transcriptional expression of PD-L1 and N-glycosyltransferase STT3A, while STT3A in turn increases the stability of PD-L1 through inducing PD-L1 protein N-glycosylation in HCC cells. CONCLUSIONS: This study reveals the crucial function of spermine in establishing immune privilege by increasing the expression and N-glycosylation of PD-L1, providing a potential strategy for the treatment of hepatocellular carcinoma. Video Abstract.

P300-dependent acetylation of histone H3 is required for epidermal growth factor receptor-mediated high-mobility group protein A2 transcription in hepatocellular carcinoma.

High-mobility group protein A2 (HMGA2) is highly expressed in hepatocellular carcinoma (HCC) cells and contributes to tumor metastasis and poor patient survival. However, the molecular mechanism through which HMGA2 is transcriptionally regulated in HCC cells remains largely unclear. Here, we showed that the expression HMGA2 was upregulated in HCC, and that elevated HMGA2 could promote tumor metastasis. Incubation of HCC cells with epidermal growth factor (EGF) could promote the expression of HMGA2 mRNA and protein. Mechanistic studies suggested that EGF can phosphorylate p300 at Ser1834 residue through the PI3K/Akt signaling pathway in HCC cells. Knockdown of p300 can reverse EGF-induced HMGA2 expression and histone H3-K9 acetylation, whereas a phosphorylation-mimic p300 S1834D mutant can stimulate HMGA2 expression as well as H3-K9 acetylation in HCC cells. Furthermore, we identified that p300-mediated H3-K9 acetylation participates in EGF-induced HMGA2 expression in HCC. In addition, the levels of H3-K9 acetylation positively correlated with the expression levels of HMGA2 in a chemically induced HCC model in rats and human HCC specimens.

DKK1 inhibits breast cancer cell migration and invasion through suppression of ß-catenin/MMP7 signaling pathway.

BACKGROUND: DKK1 has been reported to act as a tumor suppressor in breast cancer. However, the mechanism of DKK1 inhibits breast cancer migration and invasion was still unclear. METHODS: Western blot and real time PCR was used to detect the expression of DKK1, ß-catenin and MMP7 in breast cancer cells. Wound scratch assay and transwell assay was employed to examine migration and invasion of breast cancer cell. RESULTS: DKK1 overexpression dramatically inhibits breast cancer cell migration and invasion. Knockdown of DKK1 promotes migration and invasion of breast cancer cells. DKK1 suppressed breast cancer cell migration and invasion through suppression of ß-catenin and MMP7 expression. XAV-939, an inhibitor of ß-catenin accumulation could reverse DKK1 silencing-induced MMP7 expression in breast cancer cells. Meanwhile, XAV-939 also could reverse the increase in the cell number invaded through Matrigel when DKK1 was knockdown. Furthermore, depletion of MMP7 also could reverse DKK1 knockdown-induced increase in the cell number invaded through Matrigel. CONCLUSIONS: DKK1 inhibits migration and invasion of breast cancer cell through suppression of ß-catenin/MMP7 pathway, our findings offered a potential alternative for breast cancer prevention and treatment.

Suppression of epidermal growth factor receptor-mediated ß-catenin nuclear accumulation enhances the anti-tumor activity of phosphoinositide 3-kinase inhibitor in breast cancer.

Phosphoinositide 3-kinase (PI3K) signaling is frequently deregulated in breast cancer and plays a critical role in tumor progression. However, resistance to PI3K inhibitors in breast cancer has emerged, which is due to the enhanced ß-catenin nuclear accumulation. Until now, the mechanisms underlying PI3K inhibition-induced ß-catenin nuclear accumulation remains largely unknown. In the present study, we found inhibition of PI3K with LY294002 promoted ß-catenin nuclear accumulation in MCF-7 and MDA-MB-231 breast cancer cells. Combining PI3K inhibitor LY294002 with XAV-939, an inhibitor against ß-catenin nuclear accumulation, produced an additive anti-proliferation effect against breast cancer cells. Subsequent experiments suggested ß-catenin nuclear accumulation induced by PI3K inhibition depended on the feedback activation of epidermal growth factor receptor (EGFR) signaling pathway in breast cancer cells. Inhibition of EGFR phosphorylation with Gefitinib enhanced anti-proliferation effect of PI3K inhibitor LY294002 in MCF-7 and MDA-MB-231 cells. Taken together, our findings may elucidate a possible mechanism explaining the poor outcome of PI3K inhibitors in breast cancer treatment.

Akt1 inhibition promotes breast cancer metastasis through EGFR-mediated ß-catenin nuclear accumulation.

BACKGROUND: Knockdown of Akt1 promotes Epithelial-to-Mesenchymal Transition in breast cancer cells. However, the mechanisms are not completely understood. METHODS: Western blotting, immunofluorescence, luciferase assay, real time PCR, ELISA and Matrigel invasion assay were used to investigate how Akt1 inhibition promotes breast cancer cell invasion in vitro. Mouse model of lung metastasis was used to measure in vivo efficacy of Akt inhibitor MK2206 and its combination with Gefitinib. RESULTS: Knockdown of Akt1 stimulated ß-catenin nuclear accumulation, resulting in breast cancer cell invasion. ß-catenin nuclear accumulation induced by Akt1 inhibition depended on the prolonged activation of EGFR signaling pathway in breast cancer cells. Mechanistic experiments documented that knockdown of Akt1 inactivates PIKfyve via dephosphorylating of PIKfyve at Ser318 site, resulting in a decreased degradation of EGFR signaling pathway. Inhibition of Akt1 using MK2206 could induce an increase in the expression of EGFR and ß-catenin in breast cancer cells. In addition, MK2206 at a low dosage enhance breast cancer metastasis in a mouse model of lung metastasis, while an inhibitor of EGFR tyrosine kinase Gefitinib could potentially suppress breast cancer metastasis induced by Akt1 inhibition. CONCLUSION: EGFR-mediated ß-catenin nuclear accumulation is critical for Akt1 inhibition-induced breast cancer metastasis.

Design, synthesis and evaluation of novel 7-aminoalkyl-substituted flavonoid derivatives with improved cholinesterase inhibitory activities.

A novel series of 7-aminoalkyl-substituted flavonoid derivatives 5a-5r were designed, synthesized and evaluated as potential cholinesterase inhibitors. The results showed that most of the synthesized compounds exhibited potent acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activities at the micromolar range. Compound 2-(naphthalen-1-yl)-7-(8-(pyrrolidin-1-yl)octyloxy)-4H-chromen-4-one (5q) showed the best inhibitory activity (IC50, 0.64µM for AChE and 0.42µM for BChE) which were better than our previously reported compounds and the commercially available cholinergic agent Rivastigmine. The results from a Lineweaver-Burk plot indicated a mixed-type inhibition for compound 5q with AChE and BChE. Furthermore, molecular modeling study showed that 5q targeted both the catalytic active site (CAS) and the peripheral anionic site (PAS) of AChE. Besides, these compounds (5a-5r) did not affect PC12 and HepG2 cell viability at the concentration of 10µM. Consequently, these flavonoid derivatives should be further investigated as multipotent agents for the treatment of Alzheimer's disease.

DKK1 promotes hepatocellular carcinoma cell migration and invasion through ß-catenin/MMP7 signaling pathway.

BACKGROUND: Recently several reports have indicated that elevated expression of DKK1 is tightly associated with the progression of hepatocellular carcinoma (HCC). However, the biological function of DKK1 in HCC has not yet been well documented. METHODS: In this study, the role of DKK1 in tumor cell proliferation, migration and invasion was investigated using MTT, colony formation, wound scratch, transwell assays, and also human HCC samples. RESULTS: Both gain- and loss-of-function studies showed that DKK1 did not influence the tumor cell proliferation and colony formation, while dramatically promoted HCC cell migration and invasion. Subsequent investigations revealed that ß-catenin was an important target of DKK1. The blocking of ß-catenin by pharmacological inhibitor antagonized the function of DKK1, whereas introduction of ß-catenin by transfection with plasmids or treatment with GSK3ß inhibitor phenocopied the pro-migration and pro-invasion effects of DKK1. We further disclosed that DKK1 exerted its pro-invasion function, at least in part, by promoting ß-catenin expression, in turn, upregulating the expression of matrix metalloproteinase 7 (MMP7), which was independent of the canonical Wnt signaling pathway. Moreover, introduction of MMP7 significantly enhanced the ability of HCC cells to invade extracellular matrix gel in vitro. Consistently, in human HCC tissues, DKK1 level was positively correlated with ß-catenin expression, as well as tumor metastasis. CONCLUSION: Taken together, these results demonstrated that DKK1 is overexpressed in HCC; moreover, ectopic expression DKK1 promotes HCC cell migration and invasion at least partly through ß-catenin/MMP7 signaling axis, suggesting that DKK1 may be a promising target for HCC therapy.

Antitumor effects and preliminary systemic toxicity of ANISpm in vivo and in vitro.

Polyamines as a vector to ferry toxic agents have attracted attention, and naphthalimide-polyamine conjugates show potent activity and tumor cell selectivity. The present study was carried out to evaluate the antitumor effects and preliminary systemic toxicity of ANISpm, a novel 3-amino-naphthalimide-spermine conjugate. The polyamine transport system recognition of ANISpm, supported by α-difluoromethylornithine (DFMO)/spermidine (Spd) experiments, is in accordance with its potent cell selectivity between human hepatoma HepG2 cells and normal QSG7701 hepatocyte. The antiproliferative effect is because of ANISpm-induced cell apoptosis, a common characteristic of both naphthalimide and polyamine analogs. Various apoptotic assessment assays have shown that ANISpm can induce apoptosis through the PI3K/Akt signal pathway. The apoptotic signaling cascade involves Akt inactivation, which results in a series of cellular events. The downstream pathway includes Bad dephosphorylation, dissociation of 14-3-3 and Bad, and binding to Bcl-xL, which triggers the disruption of the mitochondrial membrane, release of cytochrome c, and caspases' cascade activation. Furthermore, the Akt/mTOR signal pathway is also involved in ANISpm-mediated cell-cycle arrest. Additive DFMO or Spd, which only enhances or attenuates ANISpm-mediated cell apoptosis, respectively, does not alter the signal pathway. In addition, preliminary toxicology evaluation showed that ANISpm had no obvious system toxicity at a dose of 2.5 mg/kg, which exerted potent antitumor activity in vivo, especially hematotoxicity. Thus, ANISpm merits further investigation as a potential chemotherapeutic agent against hepatocellular carcinoma.

Synthesis, crystal structure and biological evaluation of a main group seven-coordinated bismuth(III) complex with 2-acetylpyridine N4-phenylthiosemicarbazone.

Up to now, bismuth(III) complexes with thiosemicarbazones have been comparatively rare. Here, a main group seven-coordinated bismuth(III) complex [Bi(L)(NO3)2(CH3CH2OH)] (1) (HL = 2-acetylpyridine N(4)-phenylthiosemicarbazone) has been synthesized and characterized by elemental analysis, IR, (1)H NMR and single-crystal X-ray diffraction studies. The cytotoxicity data suggest that 1 exhibits higher in vitro antiproliferative activity in four human cancer cells tested. Its possible apoptotic mechanism has been evaluated in HepG2 cells. Compound 1 promotes a dose-dependent apoptosis in HepG2 cells and the apoptosis is associated with an increase in intracellular reactive oxygen species (ROS) production and reduction of mitochondrial membrane potential (MMP).

Essential role of autophagy in fucoxanthin-induced cytotoxicity to human epithelial cervical cancer HeLa cells.

AIM: To investigate the effects and the molecular mechanisms of fucoxanthin, a major carotenoid found in edible seaweed, on HeLa cells. METHODS: The cytotoxicity of fucoxanthin was evaluated using MTT assay. Cell cycle and apoptosis were evaluated using flow cytometric analysis. Autophagy was detected with acridine orange staining and transient transfection of the GFP-LC3 plasmid into the cells. Protein expression was detected with Western blotting. RESULTS: Treatment of HeLa cells with fucoxanthin (10-80 µmol/L) for 48 h caused dose-dependent cytotoxicity with an IC50 value of 55.1±7.6 µmol/L. Fucoxanthin (10, 20, and 40 µmol/L) dose-dependently induced G0/G1 arrest, but did not change the apoptosis of HeLa cells. The same concentrations of fucoxanthin dose-dependently increased the protein expression of LC3 II (the autophagosome marker) and Beclin 1 (the initiation factor for autophagosome formation) in HeLa cells. Moreover, fucoxanthin dose-dependently decreased the levels of phosphorylated Akt and its downstream proteins p53, p70S6K, and mTOR, and increases the expression of PTEN in HeLa cells. Pretreatment of HeLa cells with 3-methyladenine (5 mmol/L) blocked the cytotoxic effect of fucoxanthin as well as fucoxanthin-induced autophagy. CONCLUSION: Fucoxanthin exerts autophagy-dependent cytotoxic effect in HeLa cells via inhibition of Akt/mTOR signaling pathway.

[Synergistic antitumor effects of tanshinone II A in combination with cisplatin via apoptosis in the prostate cancer cells].

Treatment with the combination of Chinese herbs and cytotoxic chemotherapies showed a higher survival rate in clinical trials. In this report, the results demonstrated that the tanshinone II A, a key component of Salvia miltiorrhiza bunge, when it is combined with the cytotoxic drug cisplatin showed synergistic antitumor effects on human prostate cancer PC3 cells and LNCaP cells in vitro. Antiproliferative effects were detected with MTT assay. Cell cycle distribution and apoptosis were detected by flow cytometer. Protein expression was detected by Western blotting. The intracellular concentration of cisplatin was detected by high performance liquid chromatography. The results demonstrated that tanshinone II A significantly enhanced the antiproliferative effects of cisplatin on human prostate cancer PC3 cells and LNCaP cells with the increase of the intracellular concentration of cisplatin. These effects were correlated with cell cycle arrested at S phase and cell apoptosis. The apoptosis might be achieved through death receptor pathway and mitochondrial pathway. Furthermore, the Bcl-2 family members were also involved in this apoptotic process. Collectively, these results indicated that the combination of tanshinone II A and cisplatin had a better treatment effect in vitro not only on androgen-dependent LNCaP cells but also on androgen-independent PC3 cells.

[Molecular mechanism of ophiopogonin B induced cellular autophagy of human cervical cancer HeLa cells].

This study is to investigate the antitumor activity of ophiopogonin B (OP-B). MTT assay, flow cytometric analysis, acridine orange staining, Lyso-Tracker Red staining and HeLa-GFP-LC3 transfect cells assay were used to detect the proliferation activity, apoptosis and autophagy of HeLa cells. The results showed that OP-B exerted potent antiproliferative activity on HeLa cells, the cell growth inhibition effect of OP-B was not due to apoptosis and OP-B could induce autophagy of HeLa cells. OP-B also induced the protein expression up-regulation of Beclin-1 and promoted LC3 I transformation LC3 II, which were representative proteins of autophagy. Furthermore, 3-MA, an inhibitor of autophagy, not only inhibited OP-B-mediated autophagy but also almost completely reversed the antiproliferative effect of OP-B, suggesting that the growth inhibition effect of OP-B was autophagy dependent. Western blotting demonstrated that OP-B inhibited the phosphorylation of Akt and its' downstream vital protein, such as mTOR and p70S6K. In addition, OP-B also induced the protein expression up-regulation of PTEN, which is a negative regulation protein for Akt/mTOR signaling pathway. However, OP-B did not affect the protein expression of total Akt. Collectively, the antitumor effects of OP-B were autophagy-dependent via repression Akt/mTOR signaling pathway. Therefore, OP-B is a prospective inhibitor of Akt/mTOR and may be used as an alternative compound to treat cervical carcinoma.

Dickkopf-1 drives tumor immune evasion by inducing PD-L1 expression in hepatocellular carcinoma.

Understanding the mechanisms regulating PD-L1 expression in hepatocellular carcinoma (HCC) is important to improve the response rate to PD-1/PD-L1 blockade therapy. Here, we show that DKK1 expression is positively associated with PD-L1 expression and inversely correlated with CD8+ T cell infiltration in human HCC tumor specimens. In a subcutaneous xenograft tumor model, overexpression of DKK1 significantly promotes tumor growth, tumoral PD-L1 expression, but reduces tumoral CD8+ T cell infiltration; whereas knockdown of DKK1 has opposite effects. Moreover, enforced expression of DKK1 dramatically promotes PD-L1 expression, Akt activation, ß-catenin phosphorylation and total protein expression in HCC cells. By contrast, knockdown of DKK1 inhibits all, relative to controls. In addition, CKAP4 depletion, Akt inhibition, or ß-catenin depletion remarkably abrogates DKK1 overexpression-induced transcriptional expression of PD-L1 in HCC cells. Reconstituted expression of the active Akt1 largely increased PD-L1 transcriptional expression in HCC cells. Similarly, expression of WT ß-catenin, but not the phosphorylation-defective ß-catenin S552A mutant, significantly promotes PD-L1 expression. Correlation analysis of human HCC tumor specimens further revealed that DKK1 and PD-L1 expression were positively correlated with p-ß-catenin expression. Together, our findings revealed that DKK1 promotes PD-L1 expression through the activation of Akt/ß-catenin signaling, providing a potential strategy to enhance the clinical efficacy of PD-1/PD-L1 blockade therapy in HCC patients.

Aucubin enhances the antitumor activity of cisplatin through the inhibition of PD-L1 expression in hepatocellular carcinoma.

BACKGROUND: Hepatocellular carcinoma (HCC) is a leading cause of cancer-associated mortality in the world. However, the anticancer effects of aucubin against HCC have yet to be reported. Cisplatin often decreased CD8+ tumor-infiltrating lymphocytes in the tumor microenvironment through increasing programmed death-ligand 1 (PD-L1) expression, which seriously affected the prognostic effect of cisplatin in the treatment of patients with HCC. Therefore, it is necessary to identify a novel therapeutic avenue to increase the sensitivity of cisplatin against HCC. PURPOSE: This study aims to evaluate the anti-tumor effect of aucubin on HCC, and also to reveal the synergistic effects and mechanism of aucubin and cisplatin against HCC. STUDY DESIGN AND METHODS: An H22 xenograft mouse model was established for the in vivo experiments. Cancer cell proliferation was detected by MTT assay. RT-qPCR was performed to analyze CD274 mRNA expression in vitro. Western blotting was employed to determine the expression levels of the PD-L1, p-Akt, Akt, p-ß-catenin, and ß-catenin in vitro. Immunofluorescence was carried out to examine ß-catenin nuclear accumulation in HCC cells. Immunohistochemistry was used to detect tumoral PD-L1 and CD8α expression in xenograft mouse model. RESULTS: Aucubin inhibits tumor growth in a xenograft HCC mouse model, but did not affect HCC cell viability in vitro. Aucubin treatment significantly inhibited PD-L1 expression through inactivating Akt/ß-catenin signaling pathway in HCC cells. Overexpression of PD-L1 dramatically reversed aucubin-mediated tumoral CD8+ T cell infiltration and alleviated the antitumor activity of aucubin in xenograft mouse model. Moreover, Cisplatin could induce the expression of PD-L1 through the activation of the Akt/ß-catenin signaling pathway in HCC cells, which can be blocked by aucubin in vitro. In xenograft mouse model, cisplatin treatment induced PD-L1 expression and alleviated the infiltration of CD8+ T lymphocytes in the tumor microenvironment. Aucubin not only abrogated cisplatin-induced PD-L1 expression but also enhanced the antitumor efficacy of cisplatin in a mouse xenograft model of HCC. CONCLUSION: Aucubin exerts antitumor activity against HCC and also enhances the antitumor activity of cisplatin by suppressing the Akt/ß-catenin/PD-L1 axis.

3-Nitro-naphthalimide and nitrogen mustard conjugate NNM-25 induces hepatocellular carcinoma apoptosis via PARP-1/p53 pathway.

Hepatocellular carcinoma (HCC) is one of the main causes of death in cancer. Some naphthalimide derivatives exert high anti-proliferative effects on HCC. In this study, it is confirmed that 3-nitro-naphthalimide and nitrogen mustard conjugate (NNM-25), a novel compound conjugated by NNM-25, displayed more potent therapeutic action on HCC, both in vivo and in vitro, than amonafide, a naphthalimide drug in clinical trials. More importantly, preliminary toxicological evaluation also supported that NNM-25 exhibited less systemic toxicity than amonafide at the therapeutic dose. The antitumor mechanism of conjugates of naphthalimides with nitrogen mustard remains poorly understood up to now. Here, we first reported that apoptosis might be the terminal fate of cancer cells treated with NNM-25. Inhibition of p53 by siRNA resulted in a significant decrease of NNM-25-induced apoptosis, which corroborated that p53 played a vital role in the cell apoptosis triggered by NNM-25. NNM-25 inhibited the PARP-1 activity, AKT phosphorylation, up-regulated the protein expression of p53, Bad, and mTOR as well as down-regulating the protein expression of Bcl-2 and decreasing mitochondrial membrane potential. It also facilitated cytochrome c release from mitochondria to cytoplasm, activated caspase 8, caspase 9, and caspase 3 in HepG2 cells in vitro, as also authenticated in H22 tumor-bearing mice in vivo. Collectively, the conjugation of naphthalimides with nitrogen mustard provides favorable biological activity and thus is a valuable strategy for future drug design in HCC therapy.

A nine-coordinated bismuth(III) complex derived from pentadentate 2,6-diacetylpyridine bis((4)N-methylthiosemicarbazone): crystal structure and both in vitro and in vivo biological evaluation.

Up to now, bismuth(III) complexes with thiosemicarbazones have been comparatively rare. Few in vivo biological studies have been carried out in comparison to the plentiful in vitro data. Here, an interesting nine-coordinated bismuth(III) complex, [Bi(H2L)(NO3)2]NO3 [1; H2L = 2,6-diacetylpyridine bis((4)N-methylthiosemicarbazone)], has been synthesized and structurally characterized. The analytical data reveal the formation of 1:1 (metal/ligand) stoichiometry. In vitro biological studies have indicated that the bismuth complex 1 has shown much higher antibacterial and anticancer activities than its parent ligand, especially with MIC = 10.66 µM against Bacillus cereus and Salmonella typhimurium and IC50 = 26.8 µM against K562 leukemia cells, respectively. More importantly, it also evidently inhibits H22 xenograft tumor growth on tumor-bearing mice (10 mg/kg; inhibitory rate = 61.6%). These results indicate that coordination to bismuth(III) might be an interesting strategy in the discovery of new anticancer drug candidates.

COX-2-independent induction of apoptosis by celecoxib and polyamine naphthalimide conjugate mediated by polyamine depression in colorectal cancer cell lines.

BACKGROUND: Polyamine metabolism is an intriguing tumor therapeutic target. The present study was designed to assess the synergistic antitumor effects of NPC-16, a novel polyamine naphthalimide conjugate, with celecoxib and to elucidate the mechanism of these effects on human colorectal cancer cells. METHODS: Cell proliferation was assessed by the MTT assay. Cell apoptosis and mitochondria membrane potential were evaluated by high content screening analysis. Intracellular polyamine content was detected by HPLC. Protein expression was detected by western blot analysis. RESULTS: The co-treatment with celecoxib enhanced NPC-16-induced apoptosis in HCT116 (COX-2 no expression), HT29 (COX-2 higher expression) and Caco-2 (COX-2 higher expression) colorectal cancer cells, which was mediated by the elevated NPC-16 uptake via the effect of celecoxib on polyamine metabolism, including the up-regulated spermidine/spermine N(1)-acetyltransferase (SSAT) activity and reduced intracellular polyamine levels. The presence of celecoxib does not result in obviously different effect on the NPC-16-triggered apoptosis in diverse COX-2 expressed colorectal cell lines, suggesting that COX-2 was not one vital factor in the apoptotic mechanism. Furthermore, this synergistic apoptosis was involved in the PKB/AKT signal pathway, Bcl-2 and caspase family members. Z-VAD-FMK, a cell permeable pan caspase inhibitor, almost completely inhibited celecoxib and NPC-16 co-induced apoptosis, indicating that this apoptosis was caspase dependent. CONCLUSIONS: Co-treatment of celecoxib and NPC-16 could induce colorectal cancer cell apoptosis via COX-2-independent and caspase-dependent mechanisms. The combination therapy with these agents might provide a novel therapeutic model for colorectal cancer.

[NNIspm, a polyamine derivative, induces cellular senescence of human hepatoma HepG2 cells and its molecular mechanism].

This study is to examine the effects of NNIspm-mediated cellular senescence of HepG2 cells and elucidate its potential molecular mechanism. Cellular senescence was detected with senescence-associated beta-galactosidase staining. Cell cycle distribution, intracellular fluorescence intensity and accumulation of intracellular reactive oxygen species (ROS) were detected by high content screening (HCS). Protein expression was detected by Western blotting. Polyamines content was analyzed by high performance liquid chromatography (HPLC). The results demonstrated that NNIspm significantly induced HepG2 cells senescence. This effect was due to the decrease of intracellular polyamines, the arrest at G0/G1 phase and an increase of ROS level. The molecular senescence marker p21 increased significantly after NNIspm treatment. In contrast, the protein expressions of Cyclin E and CDK2 were obvious down-regulation. The results indicated that cellular senescence induced by NNIspm was one of its antitumor mechanisms.