Mechanism of METCAM/MUC18-promoted progression of human breast cancer cells: METCAM/MUC18 promoted tumorigenesis of human breast cancer SK-BR-3 cells in a dosage specific manner

• Main Authors: Chang-Yu Huang, 黃昶諭
• Other Authors: Guang-Jer Wu
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/d9rh66

碩士 === 中原大學 === 生物科技研究所 === 102 === Breast cancer is still the most prevalent and deadly cancer in women worldwide. The death reason of recurrent breast cancer is due to distant metastasis even after treatment. After many years of extensive studies, the mechanism and biology of breast cancer tumor formation and metastasis is still poorly understood. METCAM/MUC18, an Ig-like cell adhesion molecule, plays an important role in promoting angiogenesis, tumorigenesis and metastasis in several epithelial tumors. Over-expression of METCAM/MUC18, an Ig-like cell adhesion molecule, promotes tumorigenesis and progression of human breast cancer cells. We also observed an intriguing phenomenon that a high-expressing SK-BR-3 clone manifested a transient tumor suppression effect in vivo, but not another clone. The purpose of this study is to understand if this is due to the effect of clonal variation, dosage, or simply an artifact. Several G418-resistant clones of SK-BR-3, expressing different levels of METCAM/MUC18, were obtained for testing effects of METCAM/MUC18 on their in vitro behaviors and in vivo tumorigenesis in female athymic nude mice. Tumor sections were made for histology and immunohistochemistry (IHC) analyses and tumor lysates for Western blot analysis to determine effects of METCAM/MUC18 expression on levels of various downstream effectors. We observed that over-expression of METCAM/MUC18 promoted in vitro motility and invasiveness. The extent of in vitro tumorigenesis of SK-BR-3 cells was directly proportional to the dosage of the protein. Over-expression of METCAM/MUC18 promoted tumorigenesis of SK-BR-3 cells even when one tenth of cell number (0.5 x 106) was injected. Furthermore, the extent of in vivo tumorigenesis of SK-BR-3 cells was directly proportional to the dosage of the protein. Previously observed transient tumor suppression effect from the same clone was no longer observed. Thus we concluded that the transient suppression effect from the clone was not due to clonal variation or dosage effect, but rather due to an artifact created by injecting a high cell number (5 x 106). Downstream effectors, such as phospho-AKT/AKT ratios, VEGF and VEGF-R2, were elevated in the tumors. Thus, METCAM/MUC18 positively promotes tumorigenesis of SK-BR-3 cells via similar mechanism by increasing proliferation via augmenting survival pathway and angiogenesis.