Mesenchymal stem cells (MSCs) play a critical role in promoting cancer progression. However, it is not clear whether MSCs are located in breast cancer tissues and correlated with tumor proliferation. The aim of this study was to investigate the presence of MSCs in breast cancer tissues and evaluate their interactions with cancer cells. We successfully isolated and identified MSCs from primary breast cancer tissues. Breast cancer-associated MSCs (BC-MSCs) showed homogenous immunophenotype, and possessed tri-lineage differentiation potential (osteoblast, adipocyte, and chondrocyte). When co-transplanted with cancer cells in a xenograft model in vivo, BC-MSCs significantly increased the volume and weight of tumors. We observed that BC-MSCs stimulated mammosphere formation in the transwell co-culture system in vitro. This effect was significantly suppressed by the EGF receptor inhibitor. We verified that BC-MSCs could secrete EGF and activate cancer cell's EGF receptors. Furthermore, our data showed that EGF derived from BC-MSCs could promote mammosphere formation via the PI3K/Akt signaling pathway. Our results confirmed the presence of MSC in primary breast cancer tissues, and they could provide a favorable microenvironment for tumor cell growth in vivo, partially enhance mammosphere formation via the EGF/EGFR/Akt pathway.
Endodermal stem/progenitor cells have diverse potential applications in research and regenerative medicine, so a readily available source could have widespread uses. Here we describe derivation of human induced endodermal progenitor cells (hiEndoPCs) from gastrointestinal epithelial cells using a cocktail of defined small molecules along with support from tissue-specific mesenchymal feeders. The hiEndoPCs show clonal expansion in culture and give rise to hepatocytes, pancreatic endocrine cells, and intestinal epithelial cells when treated with defined soluble molecules directing differentiation. The hiEndoPC-derived hepatocytes are able to rescue liver failure in FahRag2 mice after transplantation, and, unlike hESCs, transplanted hiEndoPCs do not give rise to teratomas. Since human gastric epithelial cells are readily available from donors of many ages, this conversion strategy can generate clonally expandable cell populations with a variety of potential applications, including personalized drug screening and therapeutic strategies for liver failure and diabetes.
Gap junction-mediated cell-cell interactions are highly conserved and play essential roles in cell survival, proliferation, differentiation and patterning. We report that Connexin 32 (Cx32)-mediated gap junctional intercellular communication (GJIC) is necessary for human embryonic stem cell-derived hepatocytes (hESC-Heps) during step-wise hepatic lineage restriction and maturation. Vitamin K2, previously shown to promote Cx32 expression in mature hepatocytes, up-regulated Cx32 expression and GJIC activation during hepatic differentiation and maturation, resulting in significant increases of hepatic markers expression and hepatocyte functions. In contrast, negative Cx32 regulator 2-aminoethoxydiphenyl borate blocked hESC-to-hepatocyte maturation and muted hepatocyte functions through disruption of GJIC activities. Dynamic gap junction organization and internalization are phosphorylation-dependent and the p38 mitogen-activated protein kinases pathway (MAPK) can negatively regulate Cxs through phosphorylation-dependent degradation of Cxs. We found that p38 MAPK inhibitor SB203580 improved maturation of hESC-Heps correlating with up-regulation of Cx32; by contrast, the p38 MAPK activator, anisomycin, blocked hESC-Heps maturation correlating with down-regulation of Cx32. These results suggested that Cx32 is essential for cell-cell interactions that facilitate driving hESCs through hepatic-lineage maturation. Regulators of both Cx32 and other members of its pathways maybe used as a promising approach on regulating hepatic lineage restriction of pluripotent stem cells and optimizing their functional maturation.
Cell-cell contacts and interactions between pancreatic β-cells and/or other cell populations within islets are essential for cell survival, insulin secretion, and functional synchronization. Three-dimensional (3D) culture systems supply the ideal microenvironment for islet-like cluster formation and functional maintenance. However, the underlying mechanisms remain unclear. In this study, mouse insulinoma 6 (MIN6) cells were cultured in a rotating 3D culture system to form islet-like aggregates. Glucose-stimulated insulin secretion (GSIS) and the RhoA/ROCK pathway were investigated. In the 3D-cultured MIN6 cells, more endocrine-specific genes were up-regulated, and GSIS was increased to a greater extent than in cells grown in monolayers. RhoA/ROCK inactivation led to F-actin remodeling in the MIN6 cell aggregates and greater insulin exocytosis. The gap junction protein, connexin 36 (Cx36), was up-regulated in MIN6 cell aggregates and RhoA/ROCK-inactivated monolayer cells. GSIS dramatically decreased when Cx36 was knocked down by short interfering RNA and could not be reversed by RhoA/ROCK inactivation. Thus, the RhoA/ROCK signaling pathway is involved in insulin release through the up-regulation of Cx36 expression in 3D-cultured MIN6 cells.
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