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In the present study, we focused on the expression and biological functions of TMEM45B in pancreatic cancer tissues and cell lines. Real-time PCR and Western blotting were used to examine the expression levels of TMEM45B in pancreatic cancer tissues and cell lines. The functions of TMEM45B were evaluated using CCK-8, flow cytometry and transwell analysis. Our results showed that TMEM45B exhibited high expression in pancreatic cancer tissues and cell lines compared with the normal pancreatic tissues and cells. Using gene set enrichment analysis (GSEA), we found that TMEM45B may regulate multiple genes involved in the cell cycle and metastasis pathways. Downregulation of TMEM45B by RNA interference significantly reduced proliferation, invasion and migration of SW1990 and PANC-1 cells, accompanied by the induction of cell cycle arrest and apoptosis, whereas overexpression of TMEM45B promoted proliferation, invasion and migration of CFPAC-1 cells as well as apoptosis inhibition. Taken together, our study provides evidence that TMEM45B is an oncogene involved in the tumorigenesis of pancreatic cancer and may represent a new molecular target for pancreatic cancer treatment.

The ribosomal protein S27 (metallopanstimulin-1, MPS-1) has been reported to be a multifunctional protein, with increased expression in a number of cancers. We reported previously that MPS-1 was highly expressed in human gastric cancer. Knockdown of MPS-1 led to spontaneous apoptosis and repressed proliferation of human gastric cancer cells in vitro and in vivo. However, how does MPS-1 regulate these processes is unclear. Here we performed microarray and pathway analyses to investigate possible pathways involved in MPS-1 knockdown-induced apoptosis in gastric cancer cells. Our results showed that knockdown of MPS-1 inhibited NF-κB activity by reducing phosphorylation of p65 at Ser536 and IκBα at Ser32, inhibiting NF-κB nuclear translocation, and down-regulating its DNA binding activity. Furthermore, data-mining the Gene-Regulatory-Network revealed that growth arrest DNA damage inducible gene 45β (Gadd45β), a direct NF-κB target gene, played a critical role in MPS-1 knockdown-induced apoptosis. Over-expression of Gadd45β inhibited MPS-1 knockdown-induced apoptosis via inhibition of JNK phosphorylation. Taken together, these data revealed a novel pathway, the MPS-1/NF-κB/Gadd45β signal pathway, played an important role in MPS-1 knockdown-induced apoptosis of gastric cancer cells. This study sheds new light on the role of MPS-1/NF-κB in apoptosis and the possible use of MPS-1 targeting strategy in the treatment of gastric cancer., (Copyright © 2011 UICC.)

Objective: EGFR-mediated tumor proliferation plays an important role in the development of cancer, and is a key candidate for targeted therapy. The aim of this study is to evaluate the impact of EGFR monoclonal antibody Cetuximab (C225) on the growth, proliferation and apoptsis of gastric cancer xenograft in nude mice, and its possible mechanisms., Methods: A gastric cancer cell line SGC-7901 with high EGFR expression level was screened from 7 gastric cancer cell lines. Gastric cancer xenografts in nude mice were established, and randomly divided into C225 treatment group and PBS control group. Tumor growth curves were calculated, the impact of C225 on the tumor growth, proliferation and angiogenesis was evaluated by immunohistochemical (IHC) staining Ki67 and CD34, respectively. The effect of C225 on apoptosis in the gastric cancer cells was evaluated by TUNEL assay. The expression levels of EGFR and its transcription factor Sp1 were detected by IHC staining and Western blot., Results: After C225 treatment, the proliferation and growth of gastric cancer xenograft in nude mice were significantly decreased. In the contrast, the apopotic indexes in C225 treatment group and PBS control group were (16.4% +/- 0.3%) and (3.1% +/- 0.9%), respectively, with a significant difference (P < 0.001). There was no significant difference of the densities of CD34-positive microvessels between C225 treatment group and control group. Elevated expression of EGFR and Sp1 after C225 treatment was observed by IHC staining and Western blot assay., Conclusion: EGFR monoclonal antibody cetuximab (C225) can effectively inhibit the growth of gastric cancer xenografts in nude mice, and trigger its apoptosis. Yet, C225 treatment may upregulate the expression of EGFR and its transcription factor Sp1. A "block-transcription activation-compensation" mechanism may exist to explain the molecular mechanism of acquired resistance of a single target blockade treatment.

Objective: To observe the effect of inhibition of serine/threonine kinase15 (STK15) gene expression on apoptosis induction in gastric cancer cell line-MKN45 and discuss the role of STK15 in viability of gastric cancer cells., Methods: The STK15 expression was inhibited by chemically synthesized siRNA. The STK15 mRNA and protein level were respectively measured by real-time quantitative PCR and western blotting,the change of cell cycle distribution and apoptosis rate were detected by flow-cytometry, cell morphological change was observed by Hoechst staining,and pro-caspase 3 level was also detected by western blot., Results: After treatment by siRNA targeting STK15 after 48 h, STK15 mRNA and protein level decreased obviously. More MKN45 cells accumulated at G(2)/M phase (P< 0.05). The apoptosis rate of STK15 siRNA treated MKN45 cells was higher than that of control cells(P< 0.05) with the pro-caspase 3 level decreased., Conclusions: Inhibition of STK15 gene expression may induce apoptosis in MKN45 cells through the pathway of caspase3. STK15 gene play a key role in proliferation and viability of MKN45 cells.

Aim: Polo-like kinase 1 (PLK1) serine/threonine kinase plays a vital role in multiple phases of mitosis in gastric cancer cells. To investigate the effect of PLK1 depletion on mitosis and apoptosis of gastric cancer cells., Methods: PLK1 expression was blocked by small RNA interference(siRNA). The expression levels of PLK1, cdc2, cyclin B and caspase 3 were detected by Western blotting. Then, PLK1 depletion, cdc2 activity, cell proliferation, cell cycle phase distribution, mitotic spindle structure, and the rate of apoptosis of the PLK1 knockdown cells were observed., Results: PLK1 gene knockdown was associated with increased cyclin B expression, increased cdc2 activity (but not with the expression levels), accumulation of gastric cancer cells at G2/M, improper mitotic spindle formation, delayed chromosome separation and delayed or arrested cytokinesis. Moreover, PLK1 depletion in gastric cancer cells was associated with decreased proliferation, attenuated pro-caspase 3 levels and increased apoptosis., Conclusion: Blockage of PLK1 expression may lead to decreased mitosis or even apoptosis in gastric cancer cells, indicating that PLK1 may be a valuable therapeutic target for gastric cancer.

Objective: To observe the effect of inhibition of polo like kinase1 (plk1) gene expression on apoptosis induction in gastric cancer cell line-MKN45 and discuss the vital role of plk1 proliferation and viability of gastric cancer cells., Methods: The plk1 expression was inhibited by chemically synthesized siRNA. The plk1 mRNA and protein level were respectively measured by real-time quantitative PCR and Western blotting. The spindle morphological change was observed by immunofluorescence staining and confocal microscopy. The change of cell cycle distribution and apoptosis rate was detected by flow-cytometry. Pro caspase3 level was also detected by western blotting., Results: After treatment by siRNA targeting plk1, plk1 mRNA and protein level decreased obviously, the cell mitotic spindle became obscure and lost cohesiveness, more MKN45 cells accumulated at G(2)/M phase (P< 0.05), apoptosis rate of plk1 siRNA treated MKN45 cells was higher than that of control cells at 48 h and 72 h (P< 0.05) with pro-caspase3 level decreasing at 72 h., Conclusions: Inhibition of plk1 gene expression induces apoptosis in MKN45 cells through the pathway of caspase3. Plk1 gene play a key role in viability of MKN45 cells.

Background & Objective: Drug-resistance is a major factor of influencing treatment efficacy of advanced gastric cancer. This study was to evaluate in vitro antitumor effects of different chemotherapeutic drugs on fresh human gastric cancer cells, and explore their relationships with expressions of P-glycoprotein (P-gp), and glutathione S transferase -pi (GST-pi) in human gastric cancer tissue., Methods: A total of 39 specimens of highly purified gastric cancer cells were separately exposed to 5-fluorouracil (5-FU), cisplatin (DDP), mitomycin C (MMC), adriamycin (ADM), and hydroxycamptothecin (HCPT). Inhibitory rate of cells was detected by MTT assay. Metabolic activity of cells was detected by trypan blue exclusive assay. Cell apoptosis was detected by in situ terminal deoxynucleotidyl transferase assay (TdT assay). Expressions of GST-pi and P-gp in gastric cancer tissues were detected by immunohistochemistry., Results: After exposure to antitumor drugs, morphologic changes, decrease of metabolic activity, and apoptosis were appeared in gastric cancer cells. Inhibitory rates of cancer cells exposed to MMC, DDP, 5-FU were significantly higher than those of cells exposed to ADM, and HCPT [(38.6+/-7.7)%, (38.1+/-8.8)%, and (37.8+/-10.3)% vs. (31.9+/-10.4)%, and (29.7+/-10.2)%, P < 0.01]. Apoptosis rate of cancer cells exposed to CDDP, 5-FU, and MMC were significantly higher than those of cells exposed to HCPT, and ADM [(32.1+/-7.7)%, (31.1+/-8.8)%, and (29.8+/-6.3)% vs. (21.9+/-7.4)%, and (19.9+/- 7.4)%, P < 0.05]. Positive rate of GST-pi was 66.7%(26/39), that of P-gp was 59.0%(23/39). GST-pi positive cells showed resistance to DDP and MMC, P-gp positive cells showed resistance to ADM and HCPT., Conclusions: Overexpressions of P-gp and GST-pi might contribute to drug-resistance of tumor. Detection of GST-pi and P-gp, together with MTT chemosensitivity test, might be useful for selecting more effective chemotherapeutic drugs.

Objective: To observe whether there is constitutive activation of nuclear transcription factor kappaB (NF-kappaB) and its effect on proliferation and apoptosis of human gastric cancer cell lines., Methods: Nuclear/cytoplasmic protein expression of NF-kappaB was analyzed by Western blot in four different gastric cancer cell lines. Trans AM(TM) NF-kappaB p65 Kit was used for detecting the difference of p65 activity. The effect of PDTC (pyrrolidine dithiocarbamate), a specific inhibitor of NF-kappaB on the proliferation of gastric cancer cells, was measured by MTT (3-[4,5-dimethythiazol-2-yl]-2,5-diphenyltetrazolium bromide) method. The apoptotic rates of AGS and SGC-7901 gastric cancer cell lines were measured with flow cytometer (FCM) after treatment by PDTC., Results: The constitutive activations of NF-kappaB were identified in four gastric cancer cell lines. The expression of activated subunit of p50 was lower in AGS cell line, and higher in MKN28, MKN45 and SGC-7901 cell lines. The expression of activated subunit of p65 was lower in MKN28 and MKN45 cell lines, and higher in AGS and SGC-7901 cell lines. Both the activity of NF-kappaB and the cell proliferation were significantly inhibited in experimental group treated by PDTC, compared with control groups (p<0.01). An increased apoptotic rate and a decreased proliferating activity were observed after the gastric cancer cells were exposed to PDTC for 24 h., Conclusions: These results suggested that the constitutive activation and the protein expression of NF-kappaB are different in gastric cancer cell lines. PDTC can inhibit NF-kappaB activity and cell proliferation, which related to an increased cell apoptosis. The results disclosed that NF-kappaB could be a potential therapeutic target for solid tumor therapy., (Copyright (c) 2005 S. Karger AG, Basel.)