PI3K p85alpha gene silencing by RNA interference promotes 5-fluorouracil-induced apoptosis of colorectal cancer LoVo cells / 南方医科大学学报

<p><b>OBJECTIVE</b>To explore the effect of PI3K p85alpha gene silencing on the 5-fluorouracil (5-FU)-induced apoptosis of colorectal cancer cells.</p><p><b>METHODS</b>The PI3K p85alpha/RNAi transfected cells (PI3K p85alpha/RNAi-LoVo) were cultured in RPMI 1640 supplemented with 10% fetal calf serum and 500 microg/ml G418. The 50% inhibitory concentration (IC50) values of 5-FU (0.000625, 0.00125, 0.005, 0.01, 0.02, 0.04, 0.08, 0.16, 0.32 micromol/ml) were evaluated by MTT assay. Mitochondrial membrane potential was detected by JC-1 fluorescence, and Western blotting was used to analyze the expression of apoptotic proteins Bcl-6 and Bim.</p><p><b>RESULTS</b>Compared with the untransfected LoVo cells, PI3K p85alpha/RNAi-LoVo showed obviously decreased IC(50) of 5-FU (P=0.000). The mitochondrial membrane potential of PI3K p85alpha/RNAi-LoVo cells was significantly lower than that of LoVo cells, suggesting that silencing PI3K p85alpha expression increased the sensitivity of LoVo cells to 5-FU. The expression of apoptotic protein Bcl-6 and Bim were significantly higher in PI3K p85alpha/RNAi-LoVo cells treated with 5-FU than LoVo cells (P=0.000).</p><p><b>CONCLUSION</b>PI3Kp85alpha gene silencing can significantly promote 5-FU-induced apoptosis of colorectal LoVo cells.</p>

Effects of epigallocatechin-3-gallate on the proliferation of colonic cancer cell line SW620 and PAK1 gene expression / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the effects of epigallocatechin-3-gallate (EGCG) on the proliferation of SW620 cells and the expression of PAK1 gene.</p><p><b>METHODS</b>Human colonic cancer cell line SW620 was treated with EGCG at 40, 60 and 80 micromol/L and cultured in RPMI 1640 medium for 0, 24, 48 and 72 h. The proliferation of SW620 cells was observed by MTT assay before and after EGCG treatment, and the expression of PAK1 protein was observed by Western blotting.</p><p><b>RESULTS</b>SW620 cells treated with EGCG displayed a slowed growth in comparison with the control cells, and the growth rate decreased with the increase of EGCG concentration. PAK1 protein expression was lowered in SW620 cells after EGCG treatment for 48 h.</p><p><b>CONCLUSION</b>EGCG can inhibit the proliferation and partially reduce the expression of PAK1 protein in SW620 cells.</p>

Effect of p21-activated kinase-1 on the invasiveness of colorectal carcinoma cells in vitro / 南方医科大学学报

<p><b>OBJECTIVE</b>To observe the effect of p21-activated kinase-1 (PAK1) gene transfection on the invasiveness of human colorectal carcinoma SW480 cells in vitro.</p><p><b>METHODS</b>SW480 cells in routine culture were transfected with the recombinant plasmid EGFP-C1/PAK1 via Lipofectamine(TM) 2000. The expression of PAK1 protein in SW480 cells was detected using Western blotting, and the changes of the invasiveness of SW480 cells were evaluated using Boyden chamber invasion assay.</p><p><b>RESULTS</b>Forty-eight hours after transfection with pEGFP-C1/ PAK1, the PAK1 protein expression increased significantly in comparison with those in negative and vector control groups. The invasiveness of the SW480 cells was significantly enhanced after the transfection.</p><p><b>CONCLUSION</b>The PAK1 gene transfection can increase the expression of PAK1 in SW480 cells and enhance the invasiveness of the cells. PAK1 can be associated with the invasiveness and metastasis of colorectal carcinoma cells.</p>

PI3K p85alpha expression and its role in the progression of colorectal cancer / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the expression of PI3K p85alpha in normal colorectal tissue, colorectal adenoma and primary colorectal carcinoma and explore its significance in the progression of colorectal cancer.</p><p><b>METHODS</b>The expression of PI3K p85alpha was detected in 116 normal colorectal tissue, colorectal adenoma and primary colorectal carcinoma specimens using immunohistochemical staining, and the relationship between the expression of PI3K p85alpha protein and the clinicopathological factors was analyzed.</p><p><b>RESULTS</b>The positivity rates of the expression of PI3K p85alpha protein increased gradually in the progression of colorectal cancer and showed significant differences between the tissues (P<0.05). A significant difference was also noted in the positivity rates of the PI3K p85alpha expression in colorectal carcinoma tissues at different Dukes' stages (P<0.05). No obvious correlation was found between PI3K p85alpha expression and the degree of the tumor differentiation.</p><p><b>CONCLUSIONS</b>Abnormal PI3K p85alpha expression occurs in the progression of colorectal cancer in close relation to the clinical stage, and the PI3K/AKT pathway plays an important role in the progression of colorectal cancer.</p>

Short hairpin RNA-mediated survivin gene silencing inhibits invasion and metastasis of human colon carcinoma cell line SW480 in vitro / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the effect of short hairpin RNA (shRNA) targeting survivin on adhesion and invasion of human colon carcinoma cell line SW480 in vitro.</p><p><b>METHODS</b>According to the sequence of the coding region of survivin gene, two strings of 19 nucleotides of inverted sequence flanking the loop sequence of two complementary 9-base oligonucleotides were designed and synthesized to prepare the hairpin construct as the DNA templates for the target shRNA. The shRNA templates were cloned into shRNA expression vector pRNAT-U6.1/Neo, and the resulted vector pRNAT-U6.1/Neo-survivin was transfected into SW480 cells using Lipofectamine 2000. Western blotting was performed to evaluate survivin gene silencing induced by shRNA transfection at the protein level, and the biological behaviors of the SW480 cells were investigated by cell-matrix adhesion, invasion and gelatin-zymography assays.</p><p><b>RESULTS</b>Western blotting revealed significantly lowered survivin protein expression in transfected SW480 cells, and survivin gene silencing induced by shRNA significantly suppressed the metastatic potential of SW480 cells in association with suppressed MMPs activity.</p><p><b>CONCLUSIONS</b>Survivin may play an important role in modulating human colorectal carcinoma cell invasion and metastasis, and survivin gene silencing can inhibit human colorectal cancer cell invasion and the production of MMP-2 and MMP-9. Survivin may affect invasion and metastasis of human colorectal carcinoma cells via regulating the production of MMPs.</p>

Selective COX-2 inhibitor delays experimental gastric ulcer healing by stimulating gastric acid secretion in rats / 南方医科大学学报

<p><b>OBJECTIVE</b>To observe the effect of selective cyclooxygenase-2 (COX-2) inhibitor on the healing of experimental gastric ulcer in rats and explore its mechanisms in light of gastric acid secretion.</p><p><b>METHODS</b>Gastric ulcers were induced in rats by an application of acetic acid to the serosal surface of the anterior gastric body. The effects of selective COX-2 inhibitor, celecoxib, on the healing of gastric ulcer, the total acidity of gastric juice, the expressions of H+, K+-ATPase mRNA and protein, and the ultrastructure of the parietal cell were observed in comparison with the effects of normal saline.</p><p><b>RESULTS</b>Nine days after ulcer induction, the ulcer area was 11.9-/+3.1 mm square and 19.7-/+3.8 mm square in rats with normal saline and celecoxib treatments, respectively (P<0.01). The total acidity of gastric juice and the expressions of H+, K+-ATPase mRNA and protein in celecoxib group were significantly higher than that in normal saline group at both 6 and 9 days after ulcer induction, but no significant difference was found between the two groups in the amount of secretary canaliculus and microvillus.</p><p><b>CONCLUSION</b>Selective COX-2 inhibitor can significantly delay the healing of experimental gastric ulcer in rats, the mechanism of which might be associated with enhanced digestive action of gastric acid on the new granulation tissue at the ulcer base as a result of celecoxib-stimulated gastric acid secretion of the parietal cells.</p>

Clinical classification of Peutz-Jeghers syndrome / 南方医科大学学报

<p><b>OBJECTIVE</b>To propose the clinical classification of Peutz-Jeghers syndrome (PJS).</p><p><b>METHODS AND RESULTS</b>Retrospective analysis of 52 patients with PJS admitted in Nanfang Hospital from 1980 to 2003 was conducted. Twenty-four patients were found to have family history of PJS, who had a mean age of 19 years. In the PJS patients, the incidence of gastric polyps was 64.4%, colorectal polyps 76%, and small bowel polyps 95%. The number of polyps was above 50 in 19 of the 31 patients with gastric polyps, in 18 of the 38 patients with colorectal polyps, and in 8 of the 19 patients with small bowel polyps. The pathology of the majority of the polyps (63/108) was characterized by hamartomas, and the incidence of malignancy was 13.5% in the PJS patients.</p><p><b>CONCLUSIONS</b>PJS can be classified according to family history and location, pathology, and number of the polyps. As most patients with over 50 polyps require surgical intervention, 50 polyps is recommended as the criteria for PJS classification. Endoscopic surgery may suffice for management of patients with fewer polyps (<50), while in patients with more polyps or small bowel polyps, open surgery combined with intraoperative endoscopic surgery is recommended.</p>

Changes in cyclooxygenase gene expression during spontaneous recovery from stress ulcer in rats / 南方医科大学学报

<p><b>OBJECTIVE</b>To observe the changes in gene expression of cyclooxygenase (COX) during spontaneous recovery from stress ulcer in rats exposed to water immersion and restraint stress (WRS).</p><p><b>METHODS</b>A rat model of stress ulcer was established by means of WRS, in which the changes in COX expression were detected with immunohistochemistry and reverse transcription (RT)-PCR.</p><p><b>RESULTS</b>Very low levels of COX-2 expression were detected in the gastric mucosa of the control rats, and the expression increased significantly during the healing process of the stress ulcer (P<0.05). COX-1 expression in the gastric mucosa showed no significant difference between the control group and the stress ulcer groups during healing (P>0.05).</p><p><b>CONCLUSION</b>COX-1 and COX-2 expressions in rat gastric mucosa during the recovery from stress ulcer participate in the recovery of the damaged mucosa possibly by mediating prostaglandin secretion.</p>