ABSTRACT
Aquaporins (AQP) play important roles in water and glycerol transport. We examined whether AQP3 is expressed in primary squamous cell carcinoma (SCC) such as esophageal and oral cancer and lymph node metastasis, and whether AQP3 is a potential target for tumor therapy. A high level expression of AQP3 was observed in tumor areas of human primary SCC such as esophageal and lingual cancers, and lymph node metastasis, but was not observed in normal areas. Treatment with pan-AQP inhibitor caused apoptotic cell death on the SCC cell lines in a concentration-dependent manner. Small interfering RNA (siRNA) specific for AQP3 also inhibited cell adhesion and growth of SCC, but not those of adenocarcinoma cell lines and fibroblasts. Expression of integrin α5 and ß1, counter adhesion molecules for fibronectin, was inhibited by treatment with AQP3-siRNA. The phosphorylation of focal adhesion kinase (FAK) was decreased by treatment with AQP3-siRNA, which then caused decreases in phosphorylation of Erk and MAPK. These results indicate that the decreases in integrins and the inhibition of cell adhesion might cause inhibition of the FAK signaling pathways. Combination of AQP3-siRNA with cisplatin, a major anti-cancer drug, strongly inhibited the growth of SCC. Cell death caused by the inhibition of AQP3 was a result of direct interference with cell adhesion involving intracellular FAK-MAPK signaling pathways. These results imply a potentially important and novel role for the inhibition of AQP3 function via the use of specific siRNA in the treatment of SCC.
Subject(s)
Aquaporin 3/antagonists & inhibitors , Aquaporin 3/metabolism , Carcinoma, Squamous Cell/pathology , Esophageal Neoplasms/pathology , Tongue Neoplasms/pathology , Adenocarcinoma/metabolism , Adult , Aged , Aged, 80 and over , Antineoplastic Agents/pharmacology , Apoptosis , Aquaporin 3/biosynthesis , Aquaporin 3/genetics , Carcinoma, Squamous Cell/genetics , Carcinoma, Squamous Cell/metabolism , Cell Adhesion/drug effects , Cell Proliferation , Cisplatin/pharmacology , Esophageal Neoplasms/genetics , Esophageal Neoplasms/metabolism , Extracellular Signal-Regulated MAP Kinases/drug effects , Extracellular Signal-Regulated MAP Kinases/metabolism , Female , Focal Adhesion Protein-Tyrosine Kinases/metabolism , Humans , Integrin alpha5beta1/antagonists & inhibitors , Lymphatic Metastasis , Male , Middle Aged , Mitogen-Activated Protein Kinases/drug effects , Mitogen-Activated Protein Kinases/metabolism , Oligonucleotide Array Sequence Analysis , Phosphorylation/drug effects , RNA Interference , RNA, Small Interfering/genetics , RNA, Small Interfering/metabolism , RNA, Small Interfering/pharmacology , Tongue Neoplasms/genetics , Tongue Neoplasms/metabolism , Tumor Cells, CulturedABSTRACT
Myeloid cell leukemia-1 (Mcl-1), a member of the B-cell lymphoma-2 (Bcl-2) family, has been reported to be a critical survival factor in hematopoietic cells, yet little data exists for a role of Mcl-1 in human oral squamous cell carcinoma (SCC). A high level expression of Mcl-1 was observed in tumor cells of human primary SCC, lymph node metastasis tissues, and SCC cell lines. We manipulated expression of Mcl-1 protein in SCC cells by small interfering RNA (siRNA) for Mcl-1 and observed that Mcl-1 siRNA inhibited the growth of SCCs accompanied with apoptosis. Combination therapy of Mcl-1 siRNA and anti-tumor drug drastically inhibited the cell growth in comparison to that in each single treatment. In addition, phosphorylation of focal adhesion kinase (FAK) was decreased by treatment with Mcl-1 siRNA, resulting in decreases in phosphorylation of MEK1/2 and MAPK. The cell growth inhibition caused by knockdown of Mcl-1 was suggested to be mainly a result of suppression of proliferation via the inhibition of intracellular FAK/MAPK signaling pathways. These results imply a potentially important and novel role of the inhibition of Mcl-1 function by the use of specific siRNA in the treatment of SCC.
