CD9 negatively regulates growth signaling of the gastrointestinal cancer cells

522 Background: New targeted agents against tyrosine kinases expand the standard therapy in oncology. However, tumor resistance is still a challenge, particularly induced by mutations in growth-related signalling cascades. 20% and 10% of patients with human colon and gastric cancer carry PI3K mutations and do not react to receptor blocking therapies. Recently, selective tyrosine kinase inhibitors have been generated which block PI3K signalling pathways in tumor cells. Their therapeutically role has not yet been clarified. Methods: To define inhibitory and pro-apoptotic effects of the 2 PI3K inhibitors BEZ235 and BKM120 3 human colon cancer (HT-29, HCT-116, DLD-1) and 3 gastric cancer cell lines (NCI-n87, AGS, MKN-45) with different PIK3CA mutation status were used. First, viability, apoptosis and caspase assays were performed during incubation with inhibitors alone or combined with cytotoxic agents. Second, molecular consequences for cell cycle and the signalling pathways were analysed by defining the protein levels by FACS and Western blot. Results: Both PI3K inhibitors BEZ235 and BKM120 induced concentration dependently a significant reduction in viability and an increase in apoptotic death, while mutated cells reacted more sensitive to treatment. BKM120 had a higher efficiency than the dual PI3K/mTOR inhibitor BEZ235. BEZ235 alone caused a G1 arrest in tumor cells. In contrast, BKM120 induced a G2 shift in all gastrointestinal cancer cells. There was a clear downregulation in AKT signalling, and for BEZ235 an additional inhibition of mTOR pathway. Furthermore, BEZ235 caused synergistic induction of apoptosis combined with irinotecan in colon cancer. Combinations with 5-fluoruracil and the 2 substances induced additive apoptotic effects. Human gastric cancer cells were less sensitive to BEZ235 and BKM120. Conclusions: In general, we found higher pro-apoptotic effects for all cell lines and in special cases a better response of resistant mutant cells. Our data support the clinical development of these PI3K inhibitors BEZ235 and BKM120 as potential targeting agents for patients with different wild-type or mutated gastrointestinal cancer cells.

Download Full-text

Depletion of MUC5B mucin in gastrointestinal cancer cells alters their tumorigenic properties: implication of the Wnt/β-catenin pathway

Biochemical Journal ◽

10.1042/bcj20170348 ◽

2017 ◽

Vol 474 (22) ◽

pp. 3733-3746 ◽

Cited By ~ 11

Author(s):

Fatima Lahdaoui ◽

Mathieu Messager ◽

Audrey Vincent ◽

Flora Hec ◽

Anne Gandon ◽

...

Keyword(s):

Cancer Cells ◽

Cell Line ◽

Cancer Cell ◽

Gastrointestinal Cancer ◽

Tumour Growth ◽

Cancer Cell Line ◽

Migration And Invasion ◽

Down Regulation

Secreted mucins are large O-glycosylated proteins that participate in the protection/defence of underlying mucosae in normal adults. Alteration of their expression is a hallmark of numerous epithelial cancers and has often been correlated to bad prognosis of the tumour. The secreted mucin MUC5B is overexpressed in certain subtypes of gastric and intestinal cancers, but the consequences of this altered expression on the cancer cell behaviour are not known. To investigate the role of MUC5B in carcinogenesis, its expression was knocked-down in the human gastric cancer cell line KATO-III and in the colonic cancer cell line LS174T by using transient and stable approaches. Consequences of MUC5B knocking-down on cancer cells were studied with respect to in vitro proliferation, migration and invasion, and in vivo on tumour growth using a mouse subcutaneous xenograft model. Western blotting, luciferase assay and qRT–PCR were used to identify proteins and signalling pathways involved. In vitro MUC5B down-regulation leads to a decrease in proliferation, migration and invasion properties in both cell lines. Molecular mechanisms involved the alteration of β-catenin expression, localization and activity and decreased expression of several of its target genes. In vivo xenografts of MUC5B-deficient cells induced a decrease in tumour growth when compared with MUC5B-expressing Mock cells. Altogether, the present study shows that down-regulation of MUC5B profoundly alters proliferation, migration and invasion of human gastrointestinal cancer cells and that these alterations may be, in part, mediated by the Wnt/β-catenin pathway emphasizing the potential of MUC5B as an actor of gastrointestinal carcinogenesis.

Download Full-text