Sonic Hedgehog Mediates the Proliferation and Recruitment of Transformed Mesenchymal Stem Cells to the Stomach

Abstract

Studies using Helicobacter-infected mice show that bone marrow-derived mesenchymal stem cells (MSCs) can repopulate the gastric epithelium and promote gastric cancer progression. Within the tumor microenvironment of the stomach, pro-inflammatory cytokine interferon-gamma (IFNγ) and Sonic hedgehog (Shh) are elevated. IFNγ is implicated in tumor proliferation via activation of the Shh signaling pathway in various tissues but whether a similar mechanism exists in the stomach is unknown. We tested the hypothesis that IFNγ drives MSC proliferation and recruitment, a response mediated by Shh signaling. The current study uses transplantation of an in vitro transformed mesenchymal stem cell line (stMSCvect), that over-expresses hedgehog signaling, in comparison to non-transformed wild-type MSCs (wtMSCs), wtMSCs transfected to over-express Shh (wtMSCShh), and stMSCs transduced with lentiviral constructs containing shRNA targeting the Shh gene (stMSCShhKO). The effect of IFNγ on MSC proliferation was assessed by cell cycle analysis in vitro using cells treated with recombinant IFNγ (rmIFNγ) alone, or in combination with anti-Shh 5E1 antibody, and in vivo using mice transplanted with MSCs treated with PBS or rmIFNγ. In vitro, IFNγ significantly increased MSC proliferation, a response mediated by Shh that was blocked by 5E1 antibody. The MSC population collected from bone marrow of PBS- or IFNγ-treated mice showed that IFNγ significantly increased the percentage of all MSC cell lines in S phase, with the exception of the stMSCsShhKO cells. While the MSC cell lines with intact Shh expression were recruited to the gastric mucosa in response to IFNγ, stMSCsShhKO were not. Hedgehog signaling is required for MSC proliferation and recruitment to the stomach in response to IFNγ.

Sonic Hedgehog Ligand: A Role in Formation of a Mesenchymal Niche in Human Pancreatic Ductal Adenocarcinoma

“…Our results taken together suggest a new interpretation of the role of the Hh pathway in pancreatic cancer, not just as a pathway reactivated in the cancer epithelium but as an autocrine signal in the tumour microenvironment, as recently observed and demonstrated in gastric cancer [46]. Moreover, we suggest that the expression of Shh observed in this study in the advanced stages of human pancreatic primary tissue could potentially be a marker of the presence of an αSMA − /αSMA + mixed population which expresses molecules associated with the cancer stem cell niche and with driving metastatic potential [16] in the pancreatic tumour microenvironment.…”

“…Upregulation of Shh in pancreatic cancer compared with normal tissue has been previously described [30,41], and the Shh pathway is known to have a key role in pancreatic tumour development, progression, and metastasis [23,42,43,44]. However, our observation of Shh expression at the stromal level has only been previously observed in haematological malignancies [20,45], and in a small number of studies in mouse model solid tumours [12,36,46,47]. Recent studies suggest a paracrine model for Hh signalling in certain cancers in contrast with the previous finding of tumour epithelial cells responding to Hh ligand overexpression in an autocrine manner [19,41,43,48,49].…”

“…Our results open the possibility that the Shh ligand is a new important target in the stromal context and suggests a potential mechanism underlying the encouraging results obtained when Hh inhibitors are combined with standard-of-care. Targeting Shh could, in fact, affect the equilibrium of the stroma tumour microenvironment that makes an important contribution to tumour growth and survival [12,46].…”

Methylation Microarray Studies Highlight PDGFA Expression as a Factor in Biliary Atresia

“…Our studies indicate that PDGF expression can be influenced by both increased Hedgehog activity and decreased methylation in BA. A similar dual regulation is possible for other pathways in BA, as there are reports of Hedgehog signaling being linked to IFNγ [ 43 , 44 ], Hedgehog and Jagged/Notch working together [ 45 ], Jagged/Notch working with TGFβ and SMADs [ 46 ], and GLI2 working in the TGFβ pathway [ 47 , 48 ].…”

Hedgehog signaling in the stomach

“…While MSC cell lines with intact Shh expression were recruited to the gastric mucosa in response to IFNγ, MSCs lacking expression of Shh were not. Thus, our data suggests that Hedgehog signaling is important in MSC proliferation and recruitment to the stomach in response to IFNγ [44]. Further studies from our laboratory using these ‘transformed’ MSCs secreted Shh responsible for providing a proliferative stimulation of the gastric epithelium which is associated with tumor development [45] (Figure 2).…”