Derepression of the USP22-FASN axis by p53 loss under oxidative stress drives lipogenesis and tumorigenesis.

Overproduction of reactive oxygen species (ROS) and aberrant lipid metabolism are established hallmarks of cancer; however, the role of ROS in lipid synthesis during tumorigenesis is almost unknown. Herein, we show that ROS regulates lipid synthesis and thus controls colorectal tumorigenesis through a p53-dependent mechanism. In p53 wild-type colorectal cancer (CRC) cells, hydrogen peroxide (H2O2)-induced p53 expression represses the transcription of deubiquitinase USP22, which otherwise deubiquitinates and stabilizes Fatty Acid Synthase (FASN), and thus inhibits fatty acid synthesis. Whereas, in p53-deficient CRC cells, ROS-mediated inhibition of USP22 is relieved, leading to FASN stabilization, which thus promotes lipid synthesis and tumor growth. In human CRC specimens, USP22 expression is positively correlated with FASN expression. Our study demonstrates that ROS critically regulates lipid synthesis and tumorigenesis through the USP22-FASN axis in a p53-dependent manner, and targeting the USP22-FASN axis may represent a potential strategy for the treatment of colorectal cancer.

[Syndecan-1 expression and its significance in colitis].

OBJECTIVE: To explore the effect of syndecan-1 (Sdc-1) in the pathogenesis of colitis. METHODS: Thirty BALB/c mice were forced to drink 4% dextran sodium sulphate (DSS) in distilled water as the sole source of drinking fluid for 7 days, distilled water for 10 days, and 4% DSS in distilled water for another 7 days so as to establish colitis models and then were randomly divided into 3 equal groups: model groups 1, 2, and 3 to be killed 8, 18, and 25 days after the DSS drinking respectively to take their colons. Another 10 mice were fed with distilled water as control group and were killed on Day 8. Microscopy was used to evaluate the histological score of the colon. RT-PCR was used to detect the expression of Sdc-1 mRNA and IL-1 mRNA in the colon mucosa. Immunohistochemistry was conducted to detect the Sdc-1 protein level. RESULTS: The histological scores of the 3 model groups were all significantly higher than that of the control group (F = 448.717, P < 0.01) and the score was the highest in the model group 1 and then gradually decreased. There was not significant differences in the Sdc-1 mRNA expression among different groups (F = 0.822, P > 0.05). The levels of Sdc-1 protein of the 3 model groups were all significantly lower than that of the control group (F = 865.586, P < 0.01), and the Sdc-1 protein level was the lowest level in the model group1, and then increased gradually. The expression of IL-1 mRNA of the 3 model groups were all significantly higher than that of the control group (F = 103.833, P < 0.01), and the IL-1 mRNA level was the highest in the model group1 and then decreased gradually. CONCLUSION: The severity of colitis is associated with the reduction of Sdc-1 protein level, but not with the Sdc-1 mRNA level in the colon mucosa. The reduction of Sdc-1 protein level may be associated to increase of IL-1 level.

[Short hairpin RNA-mediated survivin gene silencing inhibits invasion and metastasis of human colon carcinoma cell line SW480 in vitro].

OBJECTIVE: To investigate the effect of short hairpin RNA (shRNA) targeting survivin on adhesion and invasion of human colon carcinoma cell line SW480 in vitro. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

[Protective effect of epigallocatechin-3-gallate on inflammatory bowel disease: experiment with rat models of induced colitis].

OBJECTIVE: To explore the protective effect of epigallocatechin-3-gallate (EGCG) on ulcerative colitis (UC) and mechanism thereof. METHODS: Sixty SD rats underwent enema of trinitrobenzene sulfonic acid (TNBS) to cause UC and then randomly divided into 6 groups: model group, undergoing enema of normal saline (NS) once a day for 2 weeks; positive drug control group, undergoing enema of 5-aminosalicylic acid (ASA), an anti-UC drug; high-dose EGCG group, undergoing enema of 100 mg/kg EGCG; low-dose EGCG group, undergoing 5 enema of 50 mg/kg EGCG; and EGCG pretreatment group, undergoing enema of 100 mg/kg once a day 3 days before the model establishment and then once a day for 2 weeks after the model establishment. Another 12 rats were used as normal controls. Two weeks later the rats were killed. The histological score of the colonic mucosa was evaluated. The cyclooxygenase-2 protein expression in the colonic mucosa was detected by immunohistochemistry and the cyclooxygenase-2 mRNA expression was assessed by semiquantitative reverse-transcription polymerase chain reaction. RESULTS: The histological score of the model group was 6.4 +/- 2.7, significantly higher than that of the normal control group (1.0 +/- 0.7, P < 0.01). The histological scores of the 5-ASA, and 100 mg/kg and 50 mg/kg EGCG groups were 3.4 +/- 1.8, 2.6 +/- 1.5, and 4.0 +/- 2.0 respectively, all significantly lower than that of the model group (all P < 0.05). The histological scores of the EGCG pretreatment group was the lowest (1.2 +/- 0.8), especially compared with the model group (P < 0.01). Cyclooxygenase -2 mRNA was not expressed in the normal control group, was highly expressed in the model group, and the expression levels of the 5-ASA and EGCG groups were all significantly lower than that of the model group (chi(2) = 22.017, P < 0.05). CONCLUSION: Preventing and ameliorating colitis by inhibiting cyclooxygenase-2 activity, EGCG may be a potential medicine in treating inflammatory bowel disease.