No abstract

Background Colon cancer is one of the three common malignant tumors, with lower 5 years survival rate. Akt is an important therapeutic target, while SC66 is a novel allosteric AKT inhibitor, which enhances the therapeutic effect in several types of cancer. However, the molecular mechanisms of targeting AKT by SC66 during colon cancer therapy are not well understood. Methods The biological role of GSK-3β in colon cancer growth suppression induced by SC66 was detected in vitro and in vivo. Hoechst 33342 and crystal violet staining were used to determine whether targeting AKT affected apoptosis and cell proliferation. The CCK8 assay was utilized to analyze cell viability. The expression levels of Akt, GSK-3β, Bax, Bcl-xL, p53 and PUMA were measured by immune blotting. Xenograft mouse model was established to study the antitumor effect of SC66 in vivo. Results Our results show that SC66 induced significantly colon cancer cell apoptosis, accompanied with Akt inactivation. After AKT inhibition, activated GSK-3β interacted with Bax directly, leading to Bax oligomerization and activation. Knocking down GSK-3β abrogated SC66-triggered Bax activation and apoptosis, which was enhanced by over-expressed GSK-3β. In addition, the expression level of Bcl-xL was down-regulated while p53 had no function during SC66-induced apoptosis. Furthermore, colon cancer growth was suppressed by SC66 therapy in vivo. Conclusion Taken together, these data indicated that the novel small molecule AKT inhibitor SC66 shows visible antitumor effects via the AKT/GSK-3β/Bax axis in vitro and in vivo. Our results provide a rational basis for the development of targeting-GSK-3β, which may serve as a potential biomarker and yield meaningful benefits for colon cancer patients in the future.

Considering possible tumorigenic activity of cyclooxygenase (COX) isozymes in myeloma, we examined expression levels of COX-1 and -2 in seven human myeloma cell lines (ARH-77, IM-9, RPMI-8226, HPC, HS-Sultan, TSPC-1, and U-266). As analyzed by reverse transcriptase-polymerase chain reaction (RT-PCR), all the cell lines constitutively expressed COX-1, while COX-2 levels markedly varied among different cell lines. Induction of COX-2 by phorbol ester was observed in RPMI-8226 and HPC cells. In contrast, COX-2 was constitutively expressed in ARH-77 and IM-9 cells. Moreover, the high expression level of COX-2 protein in ARH-77 cells was verified by Western blotting. Intact cells of ARH-77 converted 14C-labeled arachidonic acid to prostaglandin E2, F2alpha, and D2, and this activity was dose-dependently inhibited by selective COX-2 inhibitors (SC-58125 and NS-398), a non-selective COX inhibitor (indomethacin), and relatively high concentrations of a selective COX-1 inhibitor (SC-560). These COX inhibitors also suppressed the proliferation of ARH-77 cells, but significant suppression was seen only at 100 microM, a much higher concentration than those sufficient for the COX inhibition. Moreover, proliferation of the myeloma cells lacking COX-2 was also suppressed by 100 microM of SC-58125. These results suggested that the anti-proliferative effect of the COX inhibitors is independent of the inhibition of COX-2.

Here, we report that a loss or decrease of RUNX3 expression was found in 73 cases of HCCs as compared with that in normal liver tissues (p < 0.001). Various human HCC cell lines also exhibited loss or decrease of RUNX3 expression. The introduction of RUNX3 by an adenovirus vector into HCC cell lines which had decreased expressions of RUNX3 inhibited cell proliferation and cell cycle progression, decreased anchorage-independent growth, and inhibited tumorigenesis in nude mice. Exogenous expression of RUNX3 sensitized HCC cells to cytotoxic drugs and to apoptosis induced by chemotherapeutic drug adriamycin in vitro. Ectopic expression of RUNX3 in HCC cells enhanced caspase-8 and decreased Bcl-2 expression. Treatment of nude mice bearing subcutaneously established HCC tumors with a combination of an adenovirus expressing RUNX3 and adriamycin completely suppressed tumor growth. In conclusion, overexpression of RUNX3 might be a promising candidate as a treatment for HCC that would increase sensitivity to chemotherapeutic drugs.

Vascular endothelial cadherin (VE‑cadherin) was first found in vascular endothelial cells to maintain normal vascular structures and regulate endothelial cell permeability by homology adhesion. New evidence indicates that certain invasive tumor cells also express VE‑cadherin, which is involved in vasculogenic mimicry to provide a blood supply required for tumor growth and metastasis. EC1 and EC3 domains of VE‑cadherin were reported to be important for intercellular homology adhesion. In the present study, a monoclonal antibody specific to the outer-membrane immunoglobulin-like domains of VE‑cadherin was generated and the binding epitope was identified as peptide LDREVVPWYNLTVEA in the EC4 domain. This antibody inhibited proliferation and capillary-like structure formation of lung cancer Glc‑82 cells in 3D Matrigel culture in vitro. This effect was mediated by the inhibition of AKT phosphorylation. Our results suggested that the EC4 domain participates in VE‑cadherin clustering and the antibody targeting the EC4 domain of VE‑cadherin may be a promising anti‑vasculogenic mimicry agent for cancer treatment.