Dichotomy Effects of Akt Signal on Breast Epithelia by Inhibiting Epithelial-Mesenchymal Transition, Motility, and Stem Cell, but Sustaining Survival
Rulong Shen, Zhengang Peng, Wenchao Zhou, James R Scott, Jennifer R Chao, Kun-Yu Teng, Michael WY Chan, Huey-Jen L Lin. The Ohio State University, Columbus, OH; University of Arizona, Phoenix, AZ; National Chung Cheng University, Min-Hsiung, Chia-Yi, Taiwan
Background: The oncogenic roles of Akt remain controversial, but are indicated to be modulated by an interplay and net balance between various isoforms.
Design: To decipher effects of different Akt isoforms on epithelial-mesenchymal transition (EMT), MCF10A and human mammary epithelial cells (HMECs) were transduced with constitutively active Akt isoforms via retroviruses, followed by RT-qPCR analysis for a panel of known EMT-associated transcripts. In addition, same experiments were performed in MCF10A cells undergoing EMT either by TGFβ treatment or overexpressing IGF-1R. Effect of activated Akt on cell migration was appraised by transwell migration and wound-healing assays. Likewise, effect of Akt on the formation of stem/progenitor cells was evaluated by the formation of mammospheres along with by the % of ALDEFLUOR-positive cells. To determine if such effects of Akt will change with malignancy states, a series of isogenic cell lines displaying progressively increasing metastatic features (namely MI, MII and MIII) were subjected to the aforementioned assays. Finally, effect of Akt signaling on cell death rendered by chemotherapeutic agents, was assessed by MTT assay.
Results: We demonstrated that overly activated Akt signaling resulted in inhibitory effects on EMT, cell motility and stem/progenitor cell expansion, in both nonmalignant MCF10A and HMEC cells. Importantly, this action mode is largely redundant and independent of isoform types. Interestingly enough, the aforementioned “neoplasm-unfavorable” effects can be partly rescued in epithelial cells gaining advanced malignancy. In contrast to the unfavorable oncogenic behavior, activated Akt signaling in MCF10A cells remarkably rescued cell viability loss caused by cytotoxic agents, which is regarded as tumor-promoting.
Conclusions: Despite sustaining cell survival, Akt signaling plays an inhibitory effect on EMT, motility and stem cell expansion of breast epithelia, which is partly impaired by increased malignancy.
Wednesday, March 21, 2012 9:30 AM
Poster Session V # 57, Wednesday Morning