MARCH1 negatively regulates TBK1-mTOR signaling pathway by ubiquitinating TBK1.

BACKGROUND: TBK1 positively regulates the growth factor-mediated mTOR signaling pathway by phosphorylating mTOR. However, it remains unclear how the TBK1-mTOR signaling pathway is regulated. Considering that STING not only interacts with TBK1 but also with MARCH1, we speculated that MARCH1 might regulate the mTOR signaling pathway by targeting TBK1. The aim of this study was to determine whether MARCH1 regulates the mTOR signaling pathway by targeting TBK1. METHODS: The co-immunoprecipitation (Co-IP) assay was used to verify the interaction between MARCH1 with STING or TBK1. The ubiquitination of STING or TBK1 was analyzed using denatured co-immunoprecipitation. The level of proteins detected in the co-immunoprecipitation or denatured co-immunoprecipitation samples were determined by Western blotting. Stable knocked-down cells were constructed by infecting lentivirus bearing the related shRNA sequences. Scratch wound healing and clonogenic cell survival assays were used to detect the migration and proliferation of breast cancer cells. RESULTS: We showed that MARCH1 played an important role in growth factor-induced the TBK1- mTOR signaling pathway. MARCH1 overexpression attenuated the growth factor-induced activation of mTOR signaling pathway, whereas its deficiency resulted in the opposite effect. Mechanistically, MARCH1 interacted with and promoted the K63-linked ubiquitination of TBK1. This ubiquitination of TBK1 then attenuated its interaction with mTOR, thereby inhibiting the growth factor-induced mTOR signaling pathway. Importantly, faster proliferation induced by MARCH1 deficiency was weakened by mTOR, STING, or TBK1 inhibition. CONCLUSION: MARCH1 suppressed growth factors mediated the mTOR signaling pathway by targeting the STING-TBK1-mTOR axis.

MiR-107 down-regulates SIAH1 expression in human breast cancer cells and silencing of miR-107 inhibits tumor growth in a nude mouse model of triple-negative breast cancer.

We have reported that SIAH1 is down-regulated and associated with apoptosis and invasion in human breast cancer. However, the molecular mechanisms leading to SIAH1 down-regulation remain to be elucidated. Here, we demonstrated that miR-107 directly down-regulates SIAH1 expression in human breast cancer cells. Over- expression of miR-107 reduced SIAH1 expression, promoted human breast cancer cell proliferation, colony formation, migration and invasion, and inhibited apoptosis. On the contrary, silencing of miR-107 increased SIAH1 expression and inhibited the tumor growth of MDA-MB-231 cells, a kind of triple-negative breast cancer (TNBC) cells, in vitro and in vivo. Our results reveal that miR-107 is an upstream regulator for SIAH1 down-regulation in human breast cancer cells and miR-107 provides a potential effective target for the treatment of TNBC.

SPOP negatively regulates mTORC1 activity by ubiquitinating Sec13.

The mammalian target of rapamycin complex1 (mTORC1) can response to amino acid to regulate metabolism and cell growth. GATOR2 act as important role in amino acid mediated mTORC1 signaling pathway by repressing GTPase activity (GAP) of GATOR1. However, it is still unclear how GATOR2 regulates mTORC1 signaling pathway. Here, we found that K63-ubiquitination of Sce13, one component of GATOR2, suppresses the mTORC1 activity by lessening the inter-interaction of GATOR2. Mechanistically, the ubiquitination of Sec13 was mediated by SPOP. Subsequently, the ubiquitination of Sec13 attenuated its interaction with the other component of GATOR2, thus suppressing the activity of mTORC1. Importantly, the deficiency of SPOP promoted the faster proliferation and migration of breast cancer cells, which was attenuated by knocking down of Sec13. Therefore, SPOP can act as a tumor suppressor gene by negatively regulating mTORC1 signaling pathway.

Expression of Elf-1 and survivin in non-small cell lung cancer and their relationship to intratumoral microvessel density.

BACKGROUND AND OBJECTIVE: The expression of transcription factor Elf-1 and inhibitor of apoptosis survivin in non-small cell lung cancer (NSCLC) is correlated with the angiogenic factor vascular endothelial growth factor (VEGF), and are both factors affecting the cell cycle. This study investigated the expression of Elf-1, survivin, and intratumoral microvessel density (iMVD) assessed by monoclonal antibody CD105 in NSCLC, and explored their correlations with clinicopathologic features and angiogenesis of NSCLC. METHODS: PowerVision(TM)-9000 immunohistochemistry was used to evaluate the expression of Elf-1, survivin, and CD105 in tissue microarrays containing 60 specimens of NSCLC and 9 specimens of normal tissue. Western blot analysis was used to evaluate the protein levels of Elf-1 and survivin in 17 specimens of NSCLC and 5 specimens of normal tissue. RESULTS: Elf-1 and survivin were detected in 1 of the 9 normal tissues. The positive rates of Elf-1 and survivin in NSCLC were 70.0% and 65.0%, respectively. The expression levels of both Elf-1 and survivin were significantly related to tumor differentiation, lymphatic metastasis, clinical stage, and postoperative survival time (P < 0.05). Overexpression of both were related to poor prognosis: the survival rates were significantly lower in patients with positive expression than in those with negative expression (P < 0.01). Elf-1 expression was positively correlated with survivin expression (r = 0.769, P < 0.01). Elf-1 and survivin expressions were positively correlated with iMVD (r = 0.446, P < 0.01; r = 0.435, P < 0.01). CONCLUSIONS: The expression of Elf-1 and survivin in NSCLC is related to differentiation, lymphatic metastasis, clinical stage, and prognosis, and both are positively correlated with iMVD. Detection their combined expression can help to predict the malignant behavior of NSCLC. Blocking the activity of Elf-1 and survivin may be a new way to inhibit angiogenesis in NSCLC.

Expression of connective tissue growth factor in tumor tissues is an independent predictor of poor prognosis in patients with gastric cancer.

AIM: To examine the expression of connective tissue growth factor (CTGF), also known as CCN2, in gastric carcinoma (GC), and the correlation between the expression of CTGF, clinicopathologic features and clinical outcomes of patients with GC. METHODS: One hundred and twenty-two GC patients were included in the present study. All patients were followed up for at least 5 years. Proteins of CTGF were detected using the Powervision two-step immunostaining method. RESULTS: Of the specimens from 122 GC patients analyzed for CTGF expression, 58 (58/122, 47.5%) had a high CTGF expression in cytoplasm of gastric carcinoma cells and 64 (64/122, 52.5%) had a low CTGF expression. Patients with a high CTGF expression showed a higher incidence of lymph node metastasis than those with a low CTGF expression (P = 0.032). Patients with a high CTGF expression had significantly lower 5-year survival rate than those with a low CTGF expression (27.6% vs 46.9%, P = 0.0178), especially those staging I + II + III (35.7% vs 65.2%, P = 0.0027). CONCLUSION: GC patients with an elevated CTGF expression have more lymph node metastases and a shorter survival time. CTGF seems to be an independent prognostic factor for the successful differentiation of high-risk GC patients staging I + II + III. Over-expression of CTGF in human GC cells results in an increased aggressive ability.

Integrin ß3 and its ligand regulate the expression of uPA through p38 MAPK in breast cancer.

Interplay between integrins and extracellular matrix is suggested to play an important role in malignant progression and tumor differentiation. The aim of the study was to determine the combined expression of integrin ß3 and tenascin-c (TN-c) in breast cancer and examine whether integrin ß3 and TN-c can activate urokinase-type plasminogen activator (uPA) through p38 mitogen-activated protein kinase (p38 MAPK). We detected the expression of integrin ß3, TN-c, p-p38, and uPA in 80 cases of breast invasive ductal carcinoma by immunohistochemistry. In addition, we blocked integrin ß3 and TN-c in the MDA-MB-231 breast cancer cells and detected the expression of p-p38 and uPA by Western blot. Integrin ß3, TN-c, p-p38, and uPA showed high levels of expression in breast invasive ductal carcinoma. The expression of integrin ß3, TN-c, and uPA was correlated with lymph node metastasis and TNM stage in breast cancer. Furthermore, correlations were noted between any two of the three proteins. The expression of p-p38 and uPA decreased in MDA-MB-231 cells after the addition of integrin ß3 antibody and TN-c antibody. The expression of uPA decreased after addition of SB203580. Our results demonstrate that inhibition of the expression of integrin ß3 and TN-c could decrease the expression of uPA through p38 MAPK in breast cancer, suggesting that the interaction between integrin ß3 and TN-c serves an important role in breast cancer.

[Expression and significance of Elf-1 and vascular endothelial growth factor in non-small cell lung cancer].

BACKGROUND AND OBJECTIVE: The roles of vascular endothelial growth factor (VEGF) in tumor angiogenesis is related with Ets family. Elf-1, a member of Ets family, has seldom been studied. This study aimed to investigate the expression of Elf-1 and VEGF in non-small cell lung cancer (NSCLC), and explore their correlations to clinicopathologic features of NSCLC. METHODS: Tissue microarray containing 69 specimens of NSCLC and six specimens of normal lung tissues was constructed. The expression of Elf-1 and VEGF was detected by PowerVision-9000 immunohistochemistry. RESULTS: Elf-1 and VEGF were not detected in all normal tissues; the positive rates of Elf-1 and VEGF were 72.46% and 63.77% in NSCLC, respectively. The expression levels of both Elf-1 and VEGF were significantly related with tumor differentiation, lymphatic metastasis, clinical stage, and postoperative survival time (all P < 0.01). Overexpression of them was related with poor prognosis: the survival rates were significantly lower in positive patients than in negative patients (both P < 0.01). Elf-1 expression was positively correlated to VEGF expression (r = 0.702, P < 0.01). CONCLUSIONS: The expression of Elf-1 and VEGF in NSCLC is related to differentiation, lymphatic metastasis, clinical stage and prognosis. Detecting their expression in combination can help to predict the malignant behavior of NSCLC.

[Correlation of p38 mitogen-activated protein kinase signal transduction pathway to uPA expression in breast cancer].

BACKGROUND & OBJECTIVE: p38 mitogen-activated protein kinase (p38MAPK) signal transduction pathway regulates the expression of various metastasis-related genes. Urokinase-type plasminogen activator (uPA) plays an important role in cancer invasion and metastasis. This study was to explore the correlation of p38MAPK signal transduction pathway to uPA expression in breast cancer. METHODS: SP immunohistochemistry was used to test the expression of p-p38, p-Akt, p-Erk, and uPA in 60 specimens of breast cancer. Western blot was used to detect the protein levels of p-p38 and uPA in breast cancer MDA-MB-231 and MCF-7 cells and the protein level of uPA in MDA-MB-231 cells after blocking p38MAPK signal transduction pathway by SB203580, a specific inhibitor of p38MAPK. The correlations of p-p38, p-Akt, p-Erk, and uPA expression to the clinicopathologic characteristics of breast cancer, and the correlations of p-p38, p-Akt, and p-Erk expression to uPA expression were analyzed. The mechanism of p38MAPK signal transduction pathway regulating the protein expression of uPA in breast cancer cells was investigated. The correlation of p-p38 and uPA expression to prognosis of breast cancer was analyzed. RESULTS: The positive rates of p-p38, p-Akt, p-Erk, and uPA proteins in breast cancer tissues were 56.7%, 95.0%, 93.3%, and 60.0%, respectively. The expression of p-p38 was positively correlated to the expression of uPA (r=0.316, P<0.05), while the expression of p-Akt and p-Erk was not related to uPA expression. The expression of p-p38 and uPA was correlated to lymph node metastasis and TNM stage (P<0.05), but not to patients' age and tumor size (P>0.05). The expression of p-Akt and p-Erk were correlated to lymph node metastasis (P<0.05), but not to TNM stage, patients' age, and tumor size (P>0.05). The protein levels of p-p38 and uPA in MDA-MB-231 cells were higher than that in MCF-7 cells. SB203580 concentration-dependently inhibited p38MAPK pathway and induced uPA protein expression. The expression of p-p38 and uPA was negatively correlated to prognosis of breast cancer (log-rank=4.98, 5.40, P=0.026, 0.020). CONCLUSIONS: p38MAPK signal transduction pathway might improve breast cancer progression by up-regulating uPA expression, and might be an important route in invasion and metastasis of breast cancer. p-p38 and uPA might help to evaluate prognosis of breast cancer.