Platelet-derived growth factor-D induces expression of cyclooxygenase-2 in rat mesangial cells through activation of PI3K/PKB and PKCs

PDGF-D promotes cell growth, aggressiveness, angiogenesis and EMT transformation of colorectal cancer by activation of Notch1/Twist1 pathway

Platelet-derived growth factor-D (PDGF-D) plays a crucial role in the progression of several cancers. However, its role in colorectal cancer (CRC) remains unclear. Our study showed that PDGF-D was highly expressed in CRC tissues and was positively associated with the clinicopathological features. Down-regulation of PDGF-D inhibited the tumor growth, migration and angiogenesis of SW480 cells in vitro and in vivo. Whereas up-regulation of PDGF-D promoted the malignant behaviors of HCT116 cells. Moreover, PDGF-D up-regulated the expression of Notch1 and Twist1 in CRC cells. In addition, PDGF-D expression promoted Epithelial to mesenchymal transition (EMT), which was accompanied with decreased E-cadherin and increased Vimentin expression. Consistently, PDGF-D, Notch1, and Twist1 are obviously up-regulated in transforming growth factor-beta 1 (TGF-β1) treated HCT116 cells. Since Notch1 and Twist1 play an important role in EMT and tumor progression, we examined whether there is a correlation between Notch1 and Twist1 in EMT status. Our results showed that up-regulation of Notch1 was able to rescue the effects of PDGF-D down-regulation on Twist1 expression in SW480 cells, whereas down-regulation of Notch1 reduced Twist1 expression in HCT116 cells. Furthermore, we found that Twist1 promoted EMT and aggressiveness of CRC cells. These results suggest that PDGF-D promotes tumor growth and aggressiveness of CRC, moreover, down-regulation of PDGF-D inactivates Notch1/Twist1 axis, which could reverse EMT and prevent CRC progression.

Functional regulation of adipose-derived stem cells by PDGF-D

Platelet-derived growth factor-D (PDGF-D) was recently identified, and acts as potent mitogen for mesenchymal cells. PDGF-D also induces cellular transformation and promotes tumor growth. However, the functional role of PDGF-D in adipose-derived stem cells (ASCs) has not been identified. Therefore, we primarily investigated the autocrine and paracrine roles of PDGF-D in this study. Furthermore, we identified the signaling pathways and the molecular mechanisms involved in PDGF-D-induced stimulation of ASCs. It is of interest that PDGF-B is not expressed, but PDGF-D and PDGF receptor-β are expressed in ASCs. PDGF-D showed the strongest mitogenic effect on ASCs, and PDGF-D regulates the proliferation and migration of ASCs through the PI3K/Akt pathways. PDGF-D also increases the proliferation and migration of ASCs through generation of mitochondrial reactive oxygen species (mtROS) and mitochondrial fission. mtROS generation and fission were mediated by p66Shc phosphorylation, and BCL2-related protein A1 and Serpine peptidase inhibitor, clade E, member 1 mediated the proliferation and migration of ASCs. In addition, PDGF-D upregulated the mRNA expression of diverse growth factors such as vascular endothelial growth factor A, fibroblast growth factor 1 (FGF1), FGF5, leukemia inhibitory factor, inhibin, beta A, interleukin 11, and heparin-binding EGF-like growth factor. Therefore, the preconditioning of PDGF-D enhanced the hair-regenerative potential of ASCs. PDGF-D-induced growth factor expression was attenuated by a pharmacological inhibitor of mitogen-activated protein kinase pathway. In summary, PDGF-D is highly expressed by ASCs, where it acts as a potent mitogenic factor. PDGF-D also upregulates growth factor expression in ASCs. Therefore, PDGF-D can be considered a novel ASC stimulator, and used as a preconditioning agent before ASC transplantation.