[Show abstract][Hide abstract] ABSTRACT: p53 mutation is known to contribute to cancer progression. Fascin is an actin-bundling protein and has been recently identified to promote cancer cell migration and invasion through its role in formation of cellular protrusions such as filopodia and invadopodia. However, the relationship between p53 and Fascin is not understood. Here, we have found a new link between them. In colorectal adenocarcinomas, p53 mutation correlated with high NF-κB, Fascin and low E-cadherin expression. Moreover, this expression profile was shown to contribute to poor overall survival in patients with colorectal cancer. Wild-type p53 could inhibit NF-κB activity that repressed the expression of Fascin and cancer cell invasiveness. In contrast, in p53-deficient primary cultured cells, NF-κB activity was enhanced and then activation of NF-κB increased the expression of Fascin. In further analysis, we showed that NF-κB was a key determinant for p53 deletion-stimulated Fascin expression. Inhibition of NF-κB/p65 expression by pharmacological compound or p65 siRNA suppressed Fascin activity in p53-deficient cells. Moreover, restoration of p53 expression decreased the activation of Fascin through suppression of the NF-κB pathway. Taken together, these data suggest that a negative-feedback loop exists, whereby p53 can suppress colorectal cancer cell invasion by inhibiting the NF-κB-mediated activation of Fascin.
[Show abstract][Hide abstract] ABSTRACT: Apurinic/apyrimidinic endonuclease 1/redox factor-1 (Ape1/Ref-1, Ape1) is a multifunctional protein that is upregulated in human pancreatic cancer. Ape1 redox domain plays an essential role in regulating the effects of reactive oxygen species (ROS) generated during physiological metabolism and pathological stress. In the present study, we explored whether Ape1 and ROS affect WNT/β-catenin signaling. We used E3330, a small molecule inhibitor of the redox activity of Ape1, and a siRNA approach to knock down Ape1, in two human pancreatic cancer cell lines. Inhibition of Ape1 resulted in growth suppression of pancreatic cancer cells, increased ROS levels, upregulation of β-catenin and c-myc and downregulation of cyclin D1. Consistent with these data, overexpression of Ape1 in pancreatic cancer cells reduced ROS and c-myc levels and increased cyclin D1 levels. Moreover, treatment of pancreatic cancer cells with H2O2 to induce oxidative stress resulted in upregulated ROS levels, decreased Ape1 at both the mRNA and protein level, and alterations in WNT/β-catenin pathway components. Finally, treatment of pancreatic cancer cells with the WNT/β-catenin inhibitor IWR-1 resulted in growth inhibition, which was greatly enhanced when combined with E3330 treatment. In summary, our results demonstrate that ROS is an important intracellular messenger that can modulate WNT/β‑catenin signaling. The present study provides interesting new insight into crosstalk between the redox function of Ape1 and WNT/β-catenin signaling in cancer cells. Furthermore, our data show that the combination of Ape1 and WNT inhibitors enhanced the inhibition of pancreatic cell proliferation. These results provide a promising novel therapeutic strategy for treating pancreatic cancer in future.
No preview · Article · Jun 2015 · International Journal of Oncology
[Show abstract][Hide abstract] ABSTRACT: Fibulin-1, a multi-functional extracellular matrix protein, has been demonstrated to be involved in many kinds of cancer, while its function in colorectal cancer (CRC) is unclear. So here we investigated the expression and function of fibulin-1 in CRC. The expression of fibulin-1 mRNA variants named A, B, C and D in human colorectal cancer cells and colorectal cancer specimens were determined by RT-PCR. Fibulin-1 protein expression in colorectal cancer and normal colorectal mucosa tissue was evaluated by western blot, and was further validated by immunohistochemistry and enzyme-linked immunosorbent assay at serum level. The correlations between fibulin-1 expression and the clinicopathological features of colorectal cancers were evaluated by Chi-square test and Fisher's exact tests. The survival rates were calculated by the Kaplan-Meier method. Among fibulin-1 A-D variants, fibulin-1D is the predominant form expressed in colorectal cancer cell lines and colorectal cancer tissue, whereas only trace amounts of fibulin-1A-C were detectable. Fibulin-1 expressed higher in the CRC tissues and serum compared to normal control. So in the process of tumorigenesis of CRC, fibulin-1 is upregulated, however, high fibulin-1 expression showed longer survival time in colorectal cancer patients, especially in the patients with stage I/II. Low fibulin-1 expression was significantly associated with lymph node involvement, distant metastasis and Dukes' C and D stage (P < 0.05 for each). Fibulin-1 protein expression may be useful as a diagnosis and prognosis marker for colorectal cancer.
No preview · Article · Apr 2015 · American Journal of Translational Research
[Show abstract][Hide abstract] ABSTRACT: Targeting the ubiquitin-proteasome pathway is a promising approach for anticancer strategies. Recently, we found Bik accumulation in cancer cell lines after they were treated with bortezomib. However, recent evidence indicates that proteasome inhibitors may also induce the accumulation of anti-apoptotic Bcl-2 family members. The current study was designed to analyze the levels of several anti-apoptotic members of Bcl-2 family in different human cancer cell lines after they were treated with proteasome inhibitors.
Different human cancer cell lines were treated with proteasome inhibitors. Western blot were used to investigate the expression of Mcl-1 and activation of mitochondrial apoptotic signaling. Cell viability was investigated using SRB assay, and induction of apoptosis was measured using flow cytometry.
We found elevated Mcl-1 level in human colon cancer cell lines DLD1, LOVO, SW620, and HCT116; human ovarian cancer cell line SKOV3; and human lung cancer cell line H1299, but not in human breast cancer cell line MCF7 after they were treated with bortezomib. This dramatic Mcl-1 accumulation was also observed when cells were treated with other two proteasome inhibitors, MG132 and calpain inhibitor I (ALLN). Moreover, our results showed Mcl-1 accumulation was caused by stabilization of the protein against degradation. Reducing Mcl-1 accumulation by Mcl-1 siRNA reduced Mcl-1 accumulation and enhanced proteasome inhibitor-induced cell death and apoptosis, as evidenced by the increased cleavage of caspase-9, caspase-3, and poly (ADP-ribose) polymerase.
Our results showed that it was not only Bik but also Mcl-1 accumulation during the treatment of proteasome inhibitors, and combining proteasome inhibitors with Mcl-1 siRNA would enhance the ultimate anticancer effect suggesting this combination might be a more effective strategy for cancer therapy.