chir-99021 and Breast-Neoplasms

Cancer stem cells (CSCs) are considered to be tumor‑initiating cells, responsible for tumor invasive growth and dissemination to distant organ sites. Typically, radiation treatment and chemotherapy should target CSCs. However, current research investigating CSCs is impeded by the difficulty of isolating pure CSCs and maintaining them in vitro. In the present study, the synergistic inhibition of glycogen synthase kinase 3 and mitogen‑activated protein kinase kinase using small molecules, CHIR99021 and PD184352, efficiently generated CSCs from immortalized human mammary epithelial cells (HMLEs) and resulted in the acquisition of mesenchymal traits and the expression of epithelial‑mesenchymal transition markers. The cell proliferation, invasion and migration of HMLE cells were significantly promoted by CHIR99021 and PD184352 (P<0.05). Furthermore, the cell cycle was shifted from the G0/G1 phase to the G2/M phase, and the apoptotic rate was suppressed in HMLE cells following treatment with CHIR99021 and PD184352. Compared with control group, the stimulated cells exhibited an increased ability to form mammospheres and regenerate a tumor. In addition to these properties, the induced cells also exhibited notable chemotherapy resistance. In vivo, the treatment of cells with CHIR99021 and PD184352 promoted the growth of HMLE‑engrafted tumor types. These results provide a practical strategy for the generation of CSCs using small molecules in vitro, which provides a cell resource that may be used for drug screening. Additionally, the present results additionally highlighted the synergistic functions of Wnt and mitogen‑activated protein kinase kinase signaling pathways in tumorigenesis.

Topics: Animals; Apoptosis; Benzamides; Biomarkers, Tumor; Breast; Breast Neoplasms; Cell Movement; Cell Proliferation; Epithelial-Mesenchymal Transition; Female; Gene Expression Regulation, Neoplastic; Glycogen Synthase Kinase 3; Humans; MAP Kinase Kinase 1; Mice; Mice, SCID; Neoplasm Invasiveness; Neoplastic Stem Cells; Pyridines; Pyrimidines; Tumor Cells, Cultured; Wnt Proteins; Xenograft Model Antitumor Assays

Psoriasin (S100A7) is expressed in several epithelial malignancies including breast cancer. Although S100A7 is associated with the worst prognosis in estrogen receptor α-negative (ERα(-)) invasive breast cancers, its role in ERα-positive (ERα(+)) breast cancers is relatively unknown. We investigated the significance of S100A7 in ERα(+) breast cancer cells and observed that S100A7 overexpression in ERα(+) breast cancer cells, MCF7 and T47D, exhibited decreased migration, proliferation, and wound healing. These results were confirmed in vivo in nude mouse model system. Mice injected with S100A7-overexpressing MCF7 cells showed significant reduction in tumor size compared with mice injected with vector control cells. Further mechanistic studies revealed that S100A7 mediates the tumor-suppressive effects via a coordinated regulation of the β-catenin/TCF4 pathway and an enhanced interaction of β-catenin and E-cadherin in S100A7-overexpressing ERα(+) breast cancer cells. We observed down-regulation of β-catenin, p-GSK3β, TCF4, cyclin D1, and c-myc in S100A7-overexpressing ERα(+) breast cancer cells. In addition, we observed increased expression of GSK3β. Treatment with GSK3β inhibitor CHIR 99021 increased the expression of β-catenin and its downstream target c-myc in S100A7-overexpressing cells. Tumors derived from mice injected with S100A7-overexpressing MCF7 cells also showed reduced activation of the β-catenin/TCF4 pathway. Therefore, our studies reveal for the first time that S100A7-overexpressing ERα(+) breast cancer cells exhibit tumor suppressor capabilities through down-modulation of the β-catenin/TCF4 pathway both in vitro and in vivo. Because S100A7 has been shown to enhance tumorigenicity in ERα(-) cells, our studies suggest that S100A7 may possess differential activities in ERα(+) compared with ERα(-) cells.

Topics: Animals; Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; beta Catenin; Breast Neoplasms; Cyclin D1; Down-Regulation; Estrogen Receptor alpha; Female; Gene Expression Regulation, Neoplastic; Glycogen Synthase Kinase 3; Glycogen Synthase Kinase 3 beta; Humans; Mice; Mice, Nude; Neoplasm Transplantation; Proto-Oncogene Proteins c-myc; Pyridines; Pyrimidines; S100 Calcium Binding Protein A7; S100 Proteins; Transcription Factor 4; Transcription Factors; Transplantation, Heterologous; Tumor Suppressor Proteins