SMS 201-995 enhances S-phase block induced by 5-fluorouracil in a human colorectal cancer cell line

The State-of-the-Art Mechanisms and Antitumor Effects of Somatostatin in Colorectal Cancer: A Review

Somatostatin, a somatotropin release inhibiting factor (SST, SRIF), is a widely distributed multifunctional cyclic peptide and acts through a transmembrane G protein-coupled receptor (SST1-SST5). Over the past decades, research has begun to reveal the molecular mechanisms underlying the anticancer activity of this hormonal peptide. Among gastrointestinal tract (GIT) tumors, direct and indirect antitumor effects of SST have been documented best in gastroenteropancreatic neuroendocrine tumors (GEP-NETs) and less well in non-endocrine cancers, including sporadic colorectal cancer (CRC). In the latter, the signaling pathways involved in the antitumor function of SST are primarily MAPK/ERK/AKT and Wnt/β-catenin. Direct (involving the MAPK pathway) and indirect (VEGF production) antiangiogenic effects of SST in CRC have also been described. The anti-inflammatory role of SST in CRC is emphasized, but detailed molecular mechanisms are still being explored. The role of SST in tumor genome/tumor microenvironment (TME)/host's gut microbiome interactions is only partially known. The results of SST analogues (SSAs)' treatment of sporadic CRC in monotherapy in vivo are not spectacular. The current review aims to present the state-of-the-art mechanisms and antitumor activity of endogenous SST and its synthetic analogues in CRC, with particular emphasis on sporadic CRC.

The mechanisms of somatostatin induced enhanced chemosensitivity of gallbladder cancer cell line to doxorubicin: cell cycle modulation plus target enzyme up-regulation

BACKGROUND

Gallbladder carcinoma is known to be an aggressive malignancy and nonsensitive to routine chemotherapy. Its prognosis is quite poor. We have illustrated that somatostatin (SST) can enhance chemosensitivity of gallbladder cancer to Doxorubicin (DOX) in our precious studies. Here, we explored the possible mechanisms by which SST used to enhance the cytotoxicity of DOX on gallbladder carcinoma cell line.

METHODS

Human gallbladder cancer cells line (GBC-SD cell line) were divided into four groups: control group, SST group, DOX group, SST+DOX co-treated-group. Cell cycle was detected by flow cytometry (FCM). Cell apoptosis index was detected by using Annexin V/Propidium Iodide Binding on FCM. The expressions of certain key cell cycle-related factors, including retinoblastoma protein (Rb) and E2F-1 protein were investigated by western blotting. ICBP90 protein, which could be a new downstream effector of E2F-1, was also detected by western blotting. The expression of Topo IIα protein, target enzyme of DOX, was assessed in synchronized GBC-SD cells by western blotting.

RESULTS

After 24h treatment with SST alone, cell cycle was arrested at S phase in GBC-SD cells line, followed by indistinctive increment of apoptosis index. After 24h treatment with SST and DOX, apoptosis index significantly increased than that of DOX alone (P<0.05). Compared with control group, the expressions of Rb and E2F-1 protein were significantly up-regulated at 24h after treatment with SST. Similarly, the expressions of ICBP90 and Topo IIα protein were also enhanced at 24h after treatment with SST.

CONCLUSION

These results suggested that SST could induce cell cycle block in S phase in GBC-SD cells line, the most sensitive phase of the cell cycle for DOX, through up-regulating Rb, E2F-1 and ICBP90 protein expression. Furthermore, ICBP90 induced the enhanced expression of Topo IIα protein which is the target enzyme of DOX and enhanced its cytotoxic effect on GBC-SD cells. We concluded that the mechanisms of SST enhanced chemosensitivity of GBC-SD cell line to DOX might be cell cycle arrest plus up-regulated target enzyme.

Neuroendocrine tumors: a critical appraisal of management strategies

OBJECTIVES

This supplement represents the proceedings of a panel of investigators whose goal was to assess the quality of evidence pertaining to current therapeutic approaches in the management of neuroendocrine tumors (NETs). It will examine the differences in opinions between expert faculty and community physicians.

METHODS

The Neuroendocrine Tumors Summit convened in December 2009 to address 6 statements prepared by panel members that reflect important questions in the management of NETs.

RESULTS

Panel members were polled on their acceptance of each statement, and those results were compared with community-based oncologists, gastroenterologists, and endocrinologists.

CONCLUSIONS

More education regarding the treatment of NETs, including pertinent studies, is needed for physicians. Additional multicenter, prospective, placebo-controlled trials are necessary to demonstrate the benefits of somatostatin analogs, including their ability to control symptoms and affect tumor growth, and their synergistic effect with other therapies. New trials should be reported consistently and include time to tumor progression and progression-free survival as primary or secondary end points.