In the present study we found that LPCs survived long-term TGF-β treatment and underwent neoplastic transformation and exhibited T-IC characteristics. It has been well established that TGF-β levels are notably increased in cirrhotic liver and compensatory proliferation of LPCs during cirrhosis preceding HCC is secondary to sustained liver injury. Our results presented here suggest the chronic and progressively enhanced transforming effect of TGF-β on LPCs in the context of sustained liver damage. Maintenance and proliferation of stem/progenitor cells are tightly regulated by comprehensive

check details signaling network involving JAK/STAT3, NOTCH, PTEN, Akt/FOXO3a, etc.46 Dysregulation of these pathways may lead to aberrant proliferation or neoplastic transition of stem/progenitor cells. With this report, we unveiled that long-term TGF-β exposure down-regulated PTEN expression and up-regulated Akt phosphorylation in LPCs, which subsequently led to the nuclear exportation learn more of FOXO3a and neoplastic transformation of LPCs. FOXO transcription factors participate in a variety of cellular events including the maintenance of cell differentiation.47 The FOXO family

consists of four members: FOXO1, FOXO3a, FOXO4, and FOXO6, and functions in the nucleus of the cell. FOXO3a has been considered the key mediator for the maintenance of hematopoietic stem cells and the nuclear exportation of FOXO3a by phosphorylated Akt was proved to be a critical event during the transformation of stem/progenitor cells.28, 48 In the current study, our data indicate that Akt is responsible for FOXO3a inactivation and T-ICs generation in LPCs exposed to TGF-β. Akt phosphorylation is usually enhanced as a consequence of PI3-K activation or PTEN suppression.49 In the present study, PTEN suppression but not PI3-K activation was observed in LPCs upon long-term TGF-β treatment. Dysfunction of PTEN has been widely detected in various cancers and accumulating studies have implicated the pivotal role of PTEN in the maintenance of stem cells.50, 51 Impaired PTEN function could induce the transformation of stem cells into

MCE cancer stem cells, sequentially initiating tumorigenesis. Fu et al.52 reported that PTEN deficiency in mice and zebrafish induced myelodysplasia with aberrant infiltration of myeloid progenitor cells. Enhancement of PTEN signaling not only depleted leukemia-initiating cells but also restored normal HSC function, which indicates the regulatory mechanistic difference between normal stem cells and cancer stem cells, and suggests that PTEN might be pharmaceutically targeted to deplete cancer stem cells without damaging normal stem cells.53 Herein, our data also indicate that PTEN is an indispensable moderator for LPC maintenance and is significantly reduced in hepatic T-ICs. Therefore, molecular therapy targeting PTEN might be a promising approach for HCC therapy.