Inhibition of the hedgehog pathway targets the tumor-associated stroma in pancreatic cancer

Purpose: The Hedgehog (Hh) pathway has emerged as an important pathway in multiple tumor types and is thought to be dependent on a paracrine signaling mechanism. The purpose of this study was to determine the role of pancreatic cancer-associated fibroblasts (human pancreatic stellate cells, HPSCs) in Hh signaling. In addition, we evaluated the efficacy of a novel Hh antagonist, AZD8542, on tumor progression with an emphasis on the role of the stroma compartment. Experimental Design: Expression of Hh pathway members and activation of the Hh pathway were analyzed in both HPSCs and pancreatic cancer cells. We tested the effects of Smoothened (SMO) inhibition with AZD8542 on tumor growth in vivo using an orthotopic model of pancreatic cancer containing varying amounts of stroma. Results: HPSCs expressed high levels of SMO receptor and low levels of Hh ligands, whereas cancer cells showed the converse expression pattern. HPSC proliferation was stimulated by Sonic Hedgehog with upregulation of downstream GLI1 mRNA. These effects were abrogated by AZD8542 treatment. In an orthotopic model of pancreatic cancer, AZD8542 inhibited tumor growth only when HPSCs were present, implicating a paracrine signaling mechanism dependent on stroma. Further evidence of paracrine signaling of the Hh pathway in prostate and colon cancer models is provided, demonstrating the broader applicability of our findings. Conclusion: Based on the use of our novel human-derived pancreatic cancer stellate cells, our results suggest that Hh-targeted therapies primarily affect the tumor-associated stroma, rather than the epithelial compartment. Mol Cancer Res; 10(9); 1147-57. ?2012 AACR.     

Targeting the Hedgehog Pathway to Mitigate Treatment Resistance

‘Hedgehog’ (HH) molecules are secretory signaling proteins that were first discovered in Drosophila. Three HH homologues have been identified in humans including Sonic hedgehog (SHH), Indian hedgehog (IHH) and Desert hedgehog (DHH). During embryonic development, the Hedgehog (HH) signaling pathway is critical, and it regulates both proliferation and differentiation of various types of stem cells.1This article provides a brief overview of HH signaling, summarizes the correlation between HH signaling and treatment resistance of cancer cells, and discusses the recent advances in targeting this signaling cascade to overcome treatment resistance with supporting experimental results.     

Hedgehog信号通路的作用机制及研究进展

HH(Hedgehog)信号通路参与多种生物学过程,包括细胞分化、细胞增殖、细胞衰老、肿瘤的发生、肿瘤恶性转化以及肿瘤耐药,HH信号通路相关基因的异常表达或突变会在生物发生发展的不同阶段引起各种疾病的发生.而HH信号通路通过复杂的机制调控诸多信号通路,进一步影响生物体的功能.所以深入了解HH信号通路在各种遗传疾病、肿瘤...     

RIO kinase 3 acts as a SUFU-dependent positive regulator of Hedgehog signaling

Suppressor of fused (SUFU) is an essential negative regulator of the mammalian Hedgehog (HH) signaling pathway and its loss is associated with cancer development. On a cellular level, endogenous SUFU can mainly be detected in the cytoplasm and the nucleus. However, immunostaining of pancreatic cancer specimen revealed the existence of cell types showing selective enrichment of endogenous SUFU in the nucleus. Following up on this observation, we found that a SUFU construct which was experimentally tethered exclusively to the nucleus was unable to antagonize endogenous HH signaling, in contrast to control SUFU. These data suggest that alterations in the normal subcellular distribution of SUFU might interfere with its established negative role on the HH pathway. Performing a multi-well kinase screen in human cells identified RIO kinase 3 (RIOK3) as a novel modulator of SUFU subcellular distribution. Functionally, RIOK3 acts as a SUFU-dependent positive regulator of HH signaling. Taken together, we propose that factors modulating the nucleo-cytoplasmic distribution of SUFU impact on the normal function of this tumor suppressing protein.     

Pancreatic stellate cells form a niche for cancer stem cells and promote their self-renewal and invasiveness

Chronic pancreatitis and pancreatic ductal adenocarcinoma (PDAC) are characterized by extensive fibrosis. Importantly, in PDAC, this results in poor vascularization and impaired drug delivery to the cancer cells. Therefore, the combined targeting of pancreatic tumor stroma and chemotherapy should enhance response rates, but the negative outcome of a recent phase III clinical trial for the combination of chemotherapy and hedgehog pathway inhibition suggests that other means also need to be considered. Emerging data indicate that elimination of cancer stem cells as the root of the cancer is of pivotal importance for efficient treatment of pancreatic cancer. Recently, we demonstrated in a highly relevant preclinical mouse model for primary pancreatic cancers that the combination of cancer stem cell-targeting strategies in combination with a stroma-targeting agent, such as a hedgehog pathway inhibitor and chemotherapy, results in significantly enhanced long-term and progression-free survival. In the present study, we demonstrate mechanistically that Nodal-expressing pancreatic stellate cells are an important component of the tumor stroma for creating a paracrine niche for pancreatic cancer stem cells. Secretion of the embryonic morphogens Nodal/Activin by pancreatic stellate cells promoted in vitro sphere formation and invasiveness of pancreatic cancer stem cells in an Alk4-dependent manner. These data imply that the pancreatic cancer stem cell phenotype is promoted by paracrine Nodal/Activin signaling at the tumor-stroma interface. Therefore, targeting the tumor microenvironment is not only able to improve drug delivery but, even more importantly, destroys the cancer stem cell niche and, therefore, should be an integral part of cancer stem cell-based treatment strategies.     

Common activation of canonical Wnt signaling in pancreatic adenocarcinoma

Pancreatic ductal adenocarcinoma (PDA) is an extremely aggressive malignancy, which carries a dismal prognosis. Activating mutations of the Kras gene are common to the vast majority of human PDA. In addition, recent studies have demonstrated that embryonic signaling pathway such as Hedgehog and Notch are inappropriately upregulated in this disease. The role of another embryonic signaling pathway, namely the canonical Wnt cascade, is still controversial. Here, we use gene array analysis as a platform to demonstrate general activation of the canonical arm of the Wnt pathway in human PDA. Furthermore, we provide evidence for Wnt activation in mouse models of pancreatic cancer. Our results also indicate that Wnt signaling might be activated downstream of Hedgehog signaling, which is an early event in PDA evolution. Wnt inhibition blocked proliferation and induced apoptosis of cultured adenocarcinoma cells, thereby providing evidence to support the development of novel therapeutical strategies for Wnt inhibition in pancreatic adenocarcinoma.     

Development and cancer: lessons learned in the pancreas

Cancer progression and organ development are similar phenomena. Both involve rapid bursts of proliferation, angiogenesis, tissue remodeling, and cell migration. Therefore, it is not surprising that both processes utilize similar signaling machinery. In fact, many recent studies have suggested that cancer is a disease triggered by the erroneous re-activation of signaling pathways that are typically downregulated after the completion of embryonic development. This link between embryonic development and cancer is particularly exciting because it suggests that we might be able to exploit the knowledge gained in studies of Developmental Biology to obtain novel insights into tumor biology. Our evolving understanding of pancreatic adenocarcinoma is an excellent example of this relationship between development and cancer. Here we discuss recent studies have indicated important roles for two major developmental signaling pathways in pancreatic cancer: Notch and Hedgehog (Hh).     

Development and Cancer: Lessons Learned in the Pancreas

Cancer progression and organ development are similar phenomena. Both involve rapid bursts of proliferation, angiogenesis, tissue remodeling, and cell migration. Therefore, it is not surprising that both processes utilize similar signaling machinery. In fact, many recent studies have suggested that cancer is a disease triggered by the erroneous re-activation of signaling pathways that are typically down-regulated after the completion of embryonic development. This link between embryonic development and cancer is particularly exciting because it suggests that we might be able to exploit the knowledge gained in studies of Developmental Biology to obtain novel insights into tumor biology. Our evolving understanding of pancreatic adenocarcinoma is an excellent example of this relationship between development and cancer. Here we discuss recent studies have indicated important roles for two major developmental signaling pathways in pancreatic cancer: Notch and Hedgehog (Hh).     

Nodal/Activin signaling: a novel target for pancreatic cancer stem cell therapy

Targeting of cancer stem cells (CSCs) has the potential to address the recalcitrance of pancreatic cancer to chemotherapy. In this issue of Cell Stem Cell, Lonardo et al. (2011) demonstrate that Nodal/Activin signaling is crucial for the maintenance and tumor-initiating capacity of pancreatic CSCs.     

The Matricellular Protein CCN1/Cyr61 Is a Critical Regulator of Sonic Hedgehog in Pancreatic Carcinogenesis

CCN1 is a matricellular protein and a member of the CCN family of growth factors. CCN1 is associated with the development of various cancers including pancreatic ductal adenocarcinoma (PDAC). Our recent studies found that CCN1 plays a critical role in pancreatic carcinogenesis through the induction of EMT and stemness. CCN1 mRNA and protein were detected in the early precursor lesions, and their expression intensified with disease progression. However, biochemical activity and the molecular targets of CCN1 in pancreatic cancer cells are unknown. Here we show that CCN1 regulates the Sonic Hedgehog (SHh) signaling pathway, which is associated with the PDAC progression and poor prognosis. SHh regulation by CCN1 in pancreatic cancer cells is mediated through the active Notch-1. Notably, active Notch-1is recruited by CCN1 in these cells via the inhibition of proteasomal degradation results in stabilization of the receptor. We find that CCN1-induced activation of SHh signaling might be necessary for CCN1-dependent in vitro pancreatic cancer cell migration and tumorigenicity of the side population of pancreatic cancer cells (cancer stem cells) in a xenograft in nude mice. Moreover, the functional role of CCN1 could be mediated through the interaction with the αvβ3 integrin receptor. These extensive studies propose that targeting CCN1 can provide a new treatment option for patients with pancreatic cancer since blocking CCN1 simultaneously blocks two critical pathways (i.e. SHh and Notch1) associated with the development of the disease as well as drug resistance.     

Fact or fiction - identifying the elusive multiple myeloma stem cell

Multiple Myeloma (MM) is a debilitating disease of proliferating and malignant plasma cells that is currently incurable. The ability of monoclonal recurrence of disease suggests it might arise from a stem cell-like population capable of self-renewal. The difficulty to isolate the cancer stem-like cell in MM has introduced confusion toward this hypothesis. However, recent evidence has suggested that MM originates from the B cell lineage with memory-B cell like features, allowing for self-renewal of the progenitor-like status and differentiation to a monoclonal plasma cell population. Furthermore, this tumor-initiating cell uses signaling pathways and microenvironment similar to the hematopoietic stem cell, though hijacking these mechanisms to create and favor a more tumorigenic environment. The bone marrow niche allows for pertinent evasion, either through avoiding immunosurveillance or through direct interaction with the stroma, inducing quiescence and thus drug resistance. Understanding the interaction of the MM stem cell to the microenvironment and the mechanisms utilized by various stem cell-like populations to allow persistence and therapy-resistance can enable for better targeting of this cell population and potential eradication of the disease.     

Discontinuous organization and specification of the lateral floor plate in zebrafish

The floor plate is a signaling center in the ventral neural tube of vertebrates with important functions during neural patterning and axon guidance. It is composed of a centrally located medial floor plate (MFP) and a bilaterally positioned lateral floor plate (LFP). While the role of the MFP as source of signaling molecules like, e.g., Sonic Hedgehog (Shh) is well understood, the exact organization and function of the LFP are currently unclear. Based on expression analyses, the one cell wide LFP in zebrafish has been postulated to be a homogenous structure. We instead show that the zebrafish trunk LFP is discontinuously arranged. Single LFP cells alternate with p3 neuronal precursor cells, which develop V3 interneurons along the anteroposterior (AP) axis. Our mutant analyses indicate that both, formation of LFP and p3 cells require Delta-Notch signaling. Importantly, however, the two cell types are differentially regulated by Hedgehog (HH) and Nkx2.2 activities. This implicates a novel mechanism of neural tube patterning, in which distinct cell populations within one domain of the ventral neural tube are differently specified along the AP axis. We conclude that different levels of HH and Nkx2.2 activities are responsible for the alternating appearance of LFP and p3 neuronal progenitor cells in the zebrafish ventral neural tube.     

Hedgehog signaling plays roles in epithelial cell proliferation in neonatal mouse uterus and vagina

Both the uterus and vagina develop from the Müllerian duct but are quite distinct in morphology and function. To investigate factors controlling epithelial differentiation and cell proliferation in neonatal uterus and vagina, we focused on Hedgehog (HH) signaling. In neonatal mice, Sonic hh (Shh) was localized in the vaginal epithelium and Indian hh (Ihh) was slightly expressed in the uterus and vagina, whereas all Glioma-associated oncogene homolog (Gli) genes were mainly expressed in the stroma. The expression of target genes of HH signaling was high in the neonatal vagina and in the uterus, it increased with growth. Thus, in neonatal mice, Shh in the vaginal epithelium and Ihh in the uterus and vagina activated HH signaling in the stroma. Tissue recombinants showed that vaginal Shh expression was inhibited by the vaginal stroma and uterine Ihh expression was stimulated by the uterine stroma. Addition of a HH signaling inhibitor decreased epithelial cell proliferation in organ-cultured uterus and vagina and increased stromal cell proliferation in organ-cultured uterus. However, it did not affect epithelial differentiation or the expression of growth factors in organ-cultured uterus and vagina. Thus, activated HH signaling stimulates epithelial cell proliferation in neonatal uterus and vagina but inhibits stromal cell proliferation in neonatal uterus.     

Hedgehog信号通路靶基因与肿瘤的关系之研究进展

Hedgehog（HH）蛋白属于分泌蛋白家族,广泛表达于哺乳动物,非哺乳动物等多个物种,参与调控多种肿瘤形成,器官成熟、血管生成,干细胞分化,免疫细胞以及胚胎发育。文章主要就近几年来国内外对hedgehog信号通道下游靶基因在肿瘤干细胞,肿瘤细胞的转移,增殖,凋亡及胚胎发育等方面的研究进展进行综述,重点阐述hedgehog信号通路下游靶基因与肿瘤及发育的关系,以期能为与hedgehog信号通道参与调控的相关疾病提供一些靶向性临床诊疗的新思路。     

Hedgehog signaling: networking to nurture a promalignant tumor microenvironment

In addition to its role in embryonic development, the Hedgehog pathway has been shown to be an active participant in cancer development, progression, and metastasis. Although this pathway is activated by autocrine signaling by Hedgehog ligands, it can also initiate paracrine signaling with cells in the microenvironment. This creates a network of Hedgehog signaling that determines the malignant behavior of the tumor cells. As a result of paracrine signal transmission, the effects of Hedgehog signaling most profoundly influence the stromal cells that constitute the tumor microenvironment. The stromal cells in turn produce factors that nurture the tumor. Thus, such a resonating cross-talk can amplify Hedgehog signaling, resulting in molecular chatter that overall promotes tumor progression. Inhibitors of Hedgehog signaling have been the subject of intense research. Several of these inhibitors are currently being evaluated in clinical trials. Here, we review the role of the Hedgehog pathway in the signature characteristics of cancer cells that determine tumor development, progression, and metastasis. This review condenses the latest findings on the signaling pathways that are activated and/or regulated by molecules generated from Hedgehog signaling in cancer and cites promising clinical interventions. Finally, we discuss future directions for identifying the appropriate patients for therapy, developing reliable markers of efficacy of treatment, and combating resistance to Hedgehog pathway inhibitors.     

Crosstalk between TGF-β and hedgehog signaling in cancer

Hedgehog (HH) and TGF-β signals control various aspects of embryonic development and cancer progression. While their canonical signal transduction cascades have been well characterized, there is increasing evidence that these pathways are able to exert overlapping activities that challenge efficient therapeutic targeting. We herein review the current knowledge on HH signaling and summarize the recent findings on the crosstalks between the HH and TGF-β pathways in cancer.