A paracrine requirement for hedgehog signalling in cancer

The PRKCI and SOX2 oncogenes are coamplified and cooperate to activate Hedgehog signaling in lung squamous cell carcinoma

We report that two oncogenes coamplified on chromosome 3q26, PRKCI and SOX2, cooperate to drive a stem-like phenotype in lung squamous cell carcinoma (LSCC). Protein kinase Cι (PKCι) phosphorylates SOX2, a master transcriptional regulator of stemness, and recruits it to the promoter of Hedgehog (Hh) acyltransferase (HHAT) that catalyzes the rate-limiting step in Hh ligand production. PKCι-mediated SOX2 phosphorylation is required for HHAT promoter occupancy, HHAT expression, and maintenance of a stem-like phenotype. Primary LSCC tumors coordinately overexpress PKCι, SOX2, and HHAT and require PKCι-SOX2-HHAT signaling to maintain a stem-like phenotype. Thus, PKCι and SOX2 are genetically, biochemically, and functionally linked in LSCC, and together they drive tumorigenesis by establishing a cell-autonomous Hh signaling axis.

Novel hepatocellular carcinoma molecules with prognostic and therapeutic potentials

Hepatocellular carcinoma (HCC), the predominant form of primary liver cancer, is the sixth most common cancer worldwide and the third leading cause of cancer-related death. The difficulty to diagnose early cancer stages, the aggressive behaviors of HCC, and the poor effectiveness of therapeutic treatments, represent the reasons for the quite similar deaths per year and incidence number. Considering the fact that the diagnosis of HCC typically occurs in the advanced stages of the disease when the therapeutic options have only modest efficacy, the possibility to identify early diagnostic markers could be of significant benefit. So far, a large number of biomarkers have been associated to HCC progression and aggressiveness, but many of them turned out not to be of practical utility. This is the reason why active investigations are ongoing in this field. Given the huge amount of published works aimed at the identification of HCC biomarkers, in this review we mainly focused on the data published in the last year, with particular attention to the role of (1) molecular and biochemical cellular markers; (2) micro-interfering RNAs; (3) epigenetic variations; and (4) tumor stroma. It is worth mentioning that a significant number of the HCC markers described in the present review may be utilized also as targets for novel therapeutic approaches, indicating the tight relation between diagnosis and therapy. In conclusion, we believe that integrated researches among the different lines of investigation indicated above should represent the winning strategies to identify effective HCC markers and therapeutic targets.

A functional germline variant in GLI1 implicates hedgehog signaling in clinical outcome of stage II and III colon carcinoma patients

PURPOSE

Cumulating evidence indicates that germline variants in the Wnt, Notch, and Hedgehog pathways are involved in colon carcinoma progression and metastasis. We investigated germline polymorphisms in a comprehensive panel of Wnt, Notch, and Hedgehog pathway genes to predict time to recurrence (TTR) and overall survival in patients with stage II and III colon carcinoma.

EXPERIMENTAL DESIGN

A total of 742 consecutively collected patients with stage II and III colon carcinoma were included in this retrospective study. Genomic DNA was analyzed for 18 germline polymorphisms in Wnt, Notch, and Hedgehog pathway genes (SFRP, DKK 2 and 3, AXIN2, APC, MYC, TCF7L2, NOTCH2, and GLI1) by TaqMan 5'-exonuclease assays.

RESULTS

In univariate analysis, the homozygous mutant variant of GLI1 rs2228226 G>C was significantly associated with decreased TTR in a recessive genetic model after adjustment for multiple testing [HR = 2.35; confidence interval (95% CI), 1.48-3.74; P < 0.001] and remained significant in multivariate analysis including clinical stage, lymphovascular-, vascular-, and perineural-invasion (HR = 2.43; CI 95%, 1.52-3.87; P < 0.001). In subanalyses, the association was limited to patients with surgery alone (HR = 3.21; CI 95%, 1.59-6.49; P = 0.001), in contrast with patients with adjuvant chemotherapy (HR = 0.82; CI 95%, 0.35-1.95; P = 0.657). When the subgroup of patients with "high-risk" GLI1 rs2228226 C/C genotype was analyzed, no benefit of adjuvant 5-fluorouracil-based chemotherapy could be found.

CONCLUSION

This is the first study identifying GLI1 rs2228226 G>C as an independent prognostic marker in patients with stage II and III colon carcinoma. Prospective studies are warranted to validate our findings.

Kras as a key oncogene and therapeutic target in pancreatic cancer

Pancreatic cancer is one of the deadliest human malignancies and little progress has been achieved in its treatment over the past decades. Advances in our understanding of the biology of this disease provide new potential opportunities for treatment. Pancreatic cancer is preceded by precursor lesions, the most common of which are known as Pancreatic Intraepithelial Neoplasia (PanIN). PanIN lesions, which are the focus of this review, have a high incidence of Kras mutations, and Kras mutations are a hallmark of the late-stage disease. We now know from genetically engineered mouse models that oncogenic Kras is not only driving the formation of pancreatic cancer precursor lesions, but it is also required for their progression, and for the maintenance of invasive and metastatic disease. Thus, an enormous effort is being placed in generating Kras inhibitors for clinical use. Additionally, alternative approaches, including understanding the role of Kras effector pathways at different stages of the disease progression, are being devised to target Kras effector pathways therapeutically. In particular, efforts have focused on the MAPK pathway and the PI3K pathway, for which inhibitors are widely available. Finally, recent studies have highlighted the need for oncogenic Kras to establish feedback mechanisms that maintain its levels of activity; the latter might constitute alternative ways to target Kras in pancreatic cancer. Here, we will review recent basic research and discuss potential therapeutic applications.

Inhibition of hedgehog signaling by GANT58 induces apoptosis and shows synergistic antitumor activity with AKT inhibitor in acute T cell leukemia cells

The hedgehog (Hh) signaling pathways have a crucial role in cell proliferation and survival, and the de-regulation of these pathways can lead to tumorigenesis. Here we investigated the expression and function of these pathways in acute T lymphocytic leukemia cells (T-ALL). Profiling of Hh pathway members revealed common expression of key Hh signaling effectors in all T-ALL cells. We found that T-ALL cells were insensitive to specific Smoothened (SMO) inhibition following the use of low concentrations of the SMO antagonist cyclopamine. In contrast, treatment with the novel GLI antagonist GANT58 reduced expression of the target gene Patched 1 as well as GLI family zinc finger 1 (GLI1) and preferentially decreased the viability of T-ALL cells. We also found perifosine, a novel AKT inhibitor, down-regulated GLI1 protein by dephosphorylation of AKT and GSK3β dose-dependently and that pre-treatment with PD98059, a MEK/ERK pathway inhibitor, enhanced this down-regulation by 20%-30%. Then we questioned whether use of both GANT58 and AKT inhibitor together could confer a synergistic effect to decrease T-ALL cell viability. By applying the Chou-Talalay method, low concentration of GANT58 induced T-ALL cell death in a synergism fashion with perifosine or GSK690693 when used simultaneously. These findings indicate that the combined use of GANT58 and AKT inhibitor could help treat a broad range of malignant tumors in conjunction with existing cancer treatments.

Genetic progression of pancreatic cancer

The progression from normal cells to invasive pancreatic ductal adenocarcinoma (PDAC) requires the accumulation of multiple inherited or acquired mutations. Activating point mutations in the KRAS oncogene are prevalent in pancreatic cancer and result in the stimulation of several pathways including the RAF-mitogen-activated protein kinase pathway and the phosphoinositide 3-kinase pathway. Other genetic alterations, including telomere shortening and the inactivation of tumor suppressor genes such as CDKN2A, TP53, and SMAD4, which encode p16, p53, and SMAD4, respectively, also contribute to the progression of pancreatic cancer. These, and other genetic events, can present at different stages in the development of PDAC at histologically defined precursor lesions known as pancreatic intraepithelial neoplasia, intraductal papillary mucinous neoplasms, or mucinous cystic neoplasms. Each precursor lesion represents alternate routes to PDAC formation and has a unique presentation and somewhat distinct genetic events controlling its development. Despite the advances in the understanding of the genetics of PDAC, the prognosis for this cancer remains poor, and several important aspects of its pathogenesis must be clarified to improve therapeutics, including the timing and method of metastases, as well as the relationship of the tumor cells with the desmoplastic stroma, which is a characteristic feature of the cancer. This review discusses the principal genetic alterations in PDAC and its precursor lesions, including their effects on promoting carcinogenesis.

A concise review on the current understanding of pancreatic cancer stem cells

Several evidences suggest that a small population of cells known as cancer stem cells (CSCs) or tumor initiating stemlike cells within a tumor is capable of tumor initiation, maintenance and propagation. Recent publications have supported the existence of CSCs in pancreatic tumors. The pancreatic stem/progenitor cells, which express self-renewal markers, are identified to be present in the peribiliary gland. Based on the CSC hypothesis, mutations can lead to the transformation of stem/progenitor cells or differentiated cells into CSCs. The pancreatic CSCs express a wide array of markers such as CD44, CD24, ESA, CD133, c-MET, CXCR4, PD2/Paf1 and ALDH1. The CSCs are isolated based on surface markers or by other methods such as ALDEFLOUR assay or Hoechst 33342 dye exclusion assay. The isolated cells are further characterized by in vitro and in vivo tumorigenic assays. The most important characteristics of CSCs are its ability to self-renew and impart drug resistance towards chemotherapy. Moreover, these distinct cells display alteration of signaling pathways pertaining to CSCs such as Notch, Wnt and Shh to maintain the self-renewal process. Failure of cancer treatment could be attributed to the therapy resistance exhibited by the CSCs. Metastasis and drug resistance in pancreatic cancer is associated with epithelial to mesenchymal transition (EMT). Furthermore, mucins, the high molecular weight proteins are found to be associated with pancreatic CSCs and EMT. Understanding the underlying molecular pathways that aid in the metastatic and drug resistant nature of these distinct cells will aid in targeting these cells. Overall, this review focuses on the various aspects of pancreatic adult/stem progenitors, CSC hypothesis, its markers, pathways, niche, EMT and novel therapeutic drugs used for the elimination of pancreatic CSCs.

Vismodegib

Vismodegib (GDC-0449, Erivedge®) is a novel small molecule antagonist of the hedgehog (Hh) pathway that binds to smoothened (SMO) and leads to inhibition of an aberrant activation of the Hh pathway. Dysregulated Hh signaling results in uncontrolled proliferation in basal cell carcinoma (BCC) and has also been found present in medulloblastoma, and many other cancers such as those of gastrointestinal tract, brain, lung, breast, and prostate. In January 2012, vismodegib became the first agent to target the Hh pathway to receive approval by the United States Food and Drug Administration (FDA) and in July 2013 approval by the European Medicines Agency (EMA) followed for the treatment of adult patients with symptomatic metastatic BCC, or locally advanced BCC inappropriate for surgery or radiotherapy. At the moment, many trials are ongoing to further investigate the role of vismodegib in other malignancies than BCC.

Understanding the origin, activation and regulation of matrix-producing myofibroblasts for treatment of fibrotic disease

Fibrosis and scar formation results from chronic progressive injury in virtually every tissue and affects a growing number of people around the world. Myofibroblasts drive fibrosis, and recent work has demonstrated that mesenchymal cells, including pericytes and perivascular fibroblasts, are their main progenitors. Understanding the cellular mechanisms of pericyte/fibroblast-to-myofibroblast transition, myofibroblast proliferation and the key signalling pathways that regulate these processes is essential to develop novel targeted therapeutics for the growing patient population suffering from solid organ fibrosis. In this review, we summarize the current knowledge about different progenitor cells of myofibroblasts, discuss major pathways that regulate their transdifferentiation and discuss the current status of novel targeted anti-fibrotic therapeutics in development.

Presence of primary cilia in cancer cells correlates with prognosis of pancreatic ductal adenocarcinoma

Primary cilia are microtubule-based organelles that protrude from basal bodies and are involved in cell differentiation, sensory functions, and planar cell polarity. Although there are many studies examining the roles of primary cilia in the fields of embryology and physiology, few such studies have been carried out in the field of oncology, and the role of primary cilia in cancer cells is poorly understood. In this study, we identified primary cilia by immunofluorescence analysis in which primary cilia were visualized as green rods labeled with anti-acetylated α-tubulin adjacent to basal bodies detected as red dots labeled with anti-γ-tubulin. Primary cilia were found in human pancreatic cancer cell lines and in cancer cells in 25 of 100 pancreatic ductal carcinoma patients. In the clinical samples, most primary cilia in cancer tissue were observed in areas showing well-differentiated glandular structures. Patients whose cancers were primary cilia positive had a higher frequency of lymph node metastasis than those whose cancers were primary cilia negative (P = .016). Univariate analysis demonstrated that tumor size (P = .009), tumor grade (P = .001), lymph node metastasis (P = .008), and the presence of primary cilia (P = .002) correlated with overall survival. Multivariate analysis found that tumor grade (P < .001) and the presence of primary cilia (P = .001) were independent prognostic indicators. In conclusion, we showed that pancreatic cancer cells can form primary cilia and that the presence of primary cilia is significantly associated with the prognosis of pancreatic ductal adenocarcinoma.

The roles of FOXM1 in pancreatic stem cells and carcinogenesis

Pancreatic ductal adenocarcinoma (PDAC) has one of the poorest prognoses among all cancers. Over the past several decades, investigators have made great advances in the research of PDAC pathogenesis. Importantly, identification of pancreatic cancer stem cells (PCSCs) in pancreatic cancer cases has increased our understanding of PDAC biology and therapy. PCSCs are responsible for pancreatic tumorigenesis and tumor progression via a number of mechanisms, including extensive proliferation, self-renewal, high tumorigenic ability, high propensity for invasiveness and metastasis, and resistance to conventional treatment. Furthermore, emerging evidence suggests that PCSCs are involved in the malignant transformation of pancreatic intraepithelial neoplasia. The molecular mechanisms that control PCSCs are related to alterations of various signaling pathways, for instance, Hedgehog, Notch, Wnt, B-cell-specific Moloney murine leukemia virus insertion site 1, phosphoinositide 3-kinase/AKT, and Nodal/Activin. Also, authors have reported that the proliferation-specific transcriptional factor Forkhead box protein M1 is involved in PCSC self-renewal and proliferation. In this review, we describe the current knowledge about the signaling pathways related to PCSCs and the early stages of PDAC development, highlighting the pivotal roles of Forkhead box protein M1 in PCSCs and their impacts on the development and progression of pancreatic intraepithelial neoplasia.

Hedgehog signaling is active in human prostate cancer stroma and regulates proliferation and differentiation of adjacent epithelium

BACKGROUND

Contribution of stromal Hedgehog (Hh) signaling is evident in the prostate gland in mice, but needs translation to human tissues if Hh therapeutics are to be used effectively. Our goal was to determine if primary human prostate fibroblasts contain cilia, and respond to prostate Hh signaling.

METHODS

Primary human prostate cancer-associated (CAFs), and adjacent non-malignant (NPFs) fibroblasts isolated from human tissue specimens were analyzed using immunofluorescence, real-time PCR, and available array data. Cell culture and tissue recombination were used to determine responsiveness of human fibroblasts to Hh pathway manipulation and the paracrine effects of stromal Hh signaling, respectively.

RESULTS

Prostatic fibroblasts were capable of forming primary cilia, with the capacity for active Hh signaling as seen by Smo co-localization to the tip of the primary cilium. Expression of genes known to represent a signature of active Hh signaling in the prostate (especially Fgf5 and Igfbp6) were increased in CAFs compared to NPFs. The level of canonical Hh genes and prostate Hh signature genes were rarely synchronous; with lower doses of Purmorphamine/BMS-833923 regulating canonical transcription factors, and higher doses effecting prostate Hh signature genes. Grafts consisting of NPFs with constitutively active Hh signaling induced increased proliferation and dedifferentiation of adjacent non-malignant BPH-1 epithelial cells.

CONCLUSIONS

These data show that human prostatic fibroblasts have the capacity for Hh signaling and manipulation. Increased expression of a signature of prostatic Hh genes in the prostate tumor microenvironment suggests a role in the epithelial transformations driving prostate cancer (PCa).

[Recent update of molecular targeted therapy in pancreatic cancer]

Pancreatic ductal adenocarcinoma is one of the most dreaded malignancies and the 5th leading cause of cancer-related death in Korea. Late diagnosis and unfavorable response to both chemotherapy and radiotherapy result in exceptionally poor prognosis. Recently, the rapid advances of molecular biology allowed an in-depth understanding of pancreatic carcinogenesis, and there are many attempts to modulate signal pathway using specific targeted agent. However, the most of them have so far failed to improve survival significantly except erlotinib. The real challenge is now how these impressive advances of molecular biology could be successfully integrated into better clinical implications. Herein, we summarize the latest insights into the carcinogenesis, and their repercussions for novel targeted agents for pancreatic cancer, and provide a review of recent clinical trials using molecular targeted therapy.

Unraveling the therapeutic potential of the Hedgehog pathway in cancer

Major progress has been made in recent years in the development of Hedgehog (Hh) pathway inhibitors for the treatment of patients with cancer. Promising clinical trial results have been obtained in cancers that harbor activating mutations of the Hh pathway, such as basal cell carcinoma and medulloblastoma. However, for many cancers, in which Hh ligand overexpression is thought to drive tumor growth, results have been disappointing. Here we review the preclinical data that continue to shape our understanding of the Hh pathway in tumorigenesis and the emerging clinical experience with smoothened inhibitors.

Involvement and targeted intervention of dysregulated Hedgehog signaling in osteosarcoma

BACKGROUND

During development, the Hedgehog pathway plays important roles regulating the proliferation and differentiation of chondrocytes, providing a template for growing bone. In this study, the authors investigated the components of dysregulated Hedgehog signaling as potential therapeutic targets for osteosarcoma.

METHODS

Small-molecule agonists and antagonists that modulate the Hedgehog pathway at different levels were used to investigate the mechanisms of dysregulation and the efficacy of Hedgehog blockade in osteosarcoma cell lines. The inhibitory effect of a small-molecule Smoothened (SMO) antagonist, IPI-926 (saridegib), also was examined in patient-derived xenograft models.

RESULTS

An inverse correlation was identified in osteosarcoma cell lines between endogenous glioma-associated oncogene 2 (GLI2) levels and Hedgehog pathway induction levels. Cells with high levels of GLI2 were sensitive to GLI inhibition, but not SMO inhibition, suggesting that GLI2 overexpression may be a mechanism of ligand-independent activation. In contrast, cells that expressed high levels of the Hedgehog ligand gene Indian hedgehog (IHH) and the target genes patched 1 (PTCH1) and GLI1 were sensitive to modulation of both SMO and GLI, suggesting ligand-dependent activation. In 2 xenograft models, active autocrine and paracrine, ligand-dependent Hedgehog signaling was identified. IPI-926 inhibited the Hedgehog signaling interactions between the tumor and the stroma and demonstrated antitumor efficacy in 1 of 2 ligand-dependent models.

CONCLUSIONS

The current results indicate that both ligand-dependent and ligand-independent Hedgehog dysregulation may be involved in osteosarcoma. It is the first report to demonstrate Hedgehog signaling crosstalk between the tumor and the stroma in osteosarcoma. The inhibitory effect of IPI-926 warrants additional research and raises the possibility of using Hedgehog pathway inhibitors as targeted therapeutics to improve treatment for osteosarcoma.

Sox2(+) stem/progenitor cells in the adult mouse pituitary support organ homeostasis and have tumor-inducing potential

Sox2(+) adult mouse pituitary cells can self-renew and terminally differentiate in vitro, but their physiological role in vivo and possible contribution to oncogenesis remain largely unknown. Using genetic lineage tracing, we show here that the Sox2(+) cell compartment of both the embryonic and adult pituitary contains stem/progenitor cells that are able to differentiate into all hormone-producing lineages and contribute to organ homeostasis during postnatal life. In addition, we show that targeted expression of oncogenic β-catenin in Sox2(+) cells gives rise to pituitary tumors, but, unexpectedly, the tumor mass is not derived from the Sox2(+) mutation-sustaining cells, suggesting a paracrine role of Sox2(+) cells in pituitary oncogenesis. Our data therefore provide in vivo evidence of a role for Sox2(+) stem/progenitor cells in long-term physiological maintenance of the adult pituitary, and highlight an unexpected non-cell-autonomous role for these cells in the induction of pituitary tumors.

Carcinogenesis of pancreatic adenocarcinoma: precursor lesions

Pancreatic adenocarcinoma displays a variety of molecular changes that evolve exponentially with time and lead cancer cells not only to survive, but also to invade the surrounding tissues and metastasise to distant sites. These changes include: genetic alterations in oncogenes and cancer suppressor genes; changes in the cell cycle and pathways leading to apoptosis; and also changes in epithelial to mesenchymal transition. The most common alterations involve the epidermal growth factor receptor (EGFR) gene, the HER2 gene, and the K-ras gene. In particular, the loss of function of tumor-suppressor genes has been documented in this tumor, especially in CDKN2a, p53, DPC4 and BRCA2 genes. However, other molecular events involved in pancreatic adenocarcinoma pathogenesis contribute to its development and maintenance, specifically epigenetic events. In fact, key tumor suppressors that are well established to play a role in pancreatic adenocarcinoma may be altered through hypermethylation, and oncogenes can be upregulated secondary to permissive histone modifications. Indeed, factors involved in tumor invasiveness can be aberrantly expressed through dysregulated microRNAs. This review summarizes current knowledge of pancreatic carcinogenesis from its initiation within a normal cell until the time that it has disseminated to distant organs. In this scenario, highlighting these molecular alterations could provide new clinical tools for early diagnosis and new effective therapies for this malignancy.

Molecular analysis of the inhibitory effect of N-acetyl-L-cysteine on the proliferation and invasiveness of pancreatic cancer cells

Preliminary studies have suggested that the reactive oxygen species (ROS) scavenger N-acetyl-L-cysteine (NAC) may be effective in inhibiting the growth of pancreatic cancer cells. In-depth cellular and molecular analyses were carried out to determine NAC's mode of action in inhibiting the growth of a well-characterized pancreatic cancer cell line (AsPC-1). Standardized assays were used to monitor cellular growth, apoptosis, levels of ROS, cellular senescence, migration, and invasiveness. Cell stiffness was measured using atomic force microscopy. Gene expression was monitored by quantitative PCR. NAC significantly inhibits the growth and metastatic potential of AsPC-1 cells by inducing cell-cycle arrest in G1 and subsequent cellular senescence and decreased invasiveness. These anticancer properties are associated with an unexpected increase in the intracellular concentrations of ROS. NAC does not decrease the susceptibility of AsPC-1 cells to the anticancer drugs gemcitabine, mitomycin C, and doxorubicin. NAC-induced changes in gene expression are consistent with the onset of mesenchymal-to-epithelial transition. In conclusion, our findings indicate that NAC induces an integrated series of responses in AsPC-1 cells that make it a highly promising candidate for development as a pancreatic cancer therapeutic.

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.

Hedgehog signaling in human medullary thyroid carcinoma: a novel signaling pathway

BACKGROUND

Locally or widely metastatic medullary thyroid carcinoma (MTC) is difficult to treat, and therapeutic options are limited. Recently, kinase inhibitors have shown partial efficacy in this cancer, but there is a continued need for the development of novel therapeutics. Within this context, the Hedgehog (Hh) pathway has been implicated in several types of human tumors, and early clinical trials with Hh antagonists have validated Hh as a novel therapeutic target. For the first time, we evaluated Hh pathway activity in MTC, and examined the effect of Hh pathway perturbation in highly characterized MTC cell lines.

METHODS

We examined immunohistochemical expression of the Hh signaling mediators Sonic Hedgehog (Shh) and Glioblastoma (Gli)2 in paraffin-embedded normal versus histologically characterized human MTC tissue. We examined pharmacologic disruption of Hh signaling in vitro using two established MTC cell lines (TT and MZ-CRC-1). Hh signaling was either pharmacologically activated (SAG) or inhibited (GDC-0449) in MTC cell lines; Hh activity was assessed by quantitative real-time polymerase chain reaction, Western blot analysis, and quantification of cellular growth and apoptotic activity.

RESULTS

Our data showed increased expression of Hh signaling factors in human MTC compared to normal tissue. In vitro, activation of the Hh pathway resulted in increased expression of key Hh signaling components Smoothened (Smo) and Gli2. Conversely, inhibition of the Hh pathway decreased expression of these genes, leading to significantly reduced cellular growth and increased apoptosis.

CONCLUSIONS

Hedgehog signaling components are markedly upregulated in MTC. Hh pathway inhibitors have potential as novel therapeutic options in patients with metastatic and/or surgically unresectable MTC.

Deciphering the role of stroma in pancreatic cancer

PURPOSE OF REVIEW

This review intends to describe recent studies on pancreatic tumor-associated stroma and potential opportunities and limitations to its targeting.

RECENT FINDINGS

One of the defining features of pancreatic cancer is extensive desmoplasia, or an inflammatory, fibrotic reaction. Carcinoma cells live in this complex microenvironment which is comprised of extracellular matrix (ECM), diffusible growth factors, cytokines and a variety of nonepithelial cell types including endothelial cells, immune cells, fibroblasts, myofibroblasts and stellate cells. In addition to the heterogeneity noted in the nonneoplastic cells within the tumor microenvironment, it has also been recognized that neoplastic cancer cells themselves are heterogeneous, and include a subpopulation of stem-cell like cells within tumors termed cancer stem cells. Due to the failure of current therapeutics to improve outcomes in patients with pancreatic cancer, new therapeutic avenues targeting different components of the tumor microenvironment are being investigated. In this review article, we will focus on recent studies regarding the function of the tumor stroma in pancreatic cancer and therapeutic treatments that are being advanced to target the stroma as a critical part of tumor management.

SUMMARY

Recent studies have shed new light on the contribution of the pancreatic cancer fibroinflammatory stroma to pancreatic cancer biology. Additional studies are needed to better define its full contribution to tumor behavior and how to best understand the optimal ways to develop therapies that counteract its pro-neoplastic properties.

Matrix Producing Cells in Chronic Kidney Disease: Origin, Regulation, and Activation

Chronic injury to the kidney causes kidney fibrosis with irreversible loss of functional renal parenchyma and leads to the clinical syndromes of chronic kidney disease (CKD) and end-stage renal disease (ESRD). Regardless of the type of initial injury, kidney disease progression follows the same pathophysiologic processes characterized by interstitial fibrosis, capillary rarefaction and tubular atrophy. Myofibroblasts play a pivotal role in fibrosis by driving excessive extracellular matrix (ECM) deposition. Targeting these cells in order to prevent the progression of CKD is a promising therapeutic strategy, however, the cellular source of these cells is still controversial. In recent years, a growing amount of evidence points to resident mesenchymal cells such as pericytes and perivascular fibroblasts, which form extensive networks around the renal vasculature, as major contributors to the pool of myofibroblasts in renal fibrogenesis. Identifying the cellular origin of myofibroblasts and the key regulatory pathways that drive myofibroblast proliferation and transdifferentiation as well as capillary rarefaction is the first step to developing novel anti-fibrotic therapeutics to slow or even reverse CKD progression and ultimately reduce the prevalence of ESRD. This review will summarize recent findings concerning the cellular source of myofibroblasts and highlight recent discoveries concerning the key regulatory signaling pathways that drive their expansion and progression in CKD.

Role of the Hedgehog pathway in hepatocellular carcinoma (review)

The Hedgehog (Hh) pathway is an evolutionarily conserved signaling mechanism that controls many aspects of cell differentiation and the development of tissues and organs during embryogenesis. Early investigations have focused on the effects of Hh activity on the development of organs including skin, gut, the nervous system and bone. However, in addition to normal developmental processes, these investigations also found that Hh signaling is involved in aberrant proliferation and malignant transformation. Consequently, the role of Hh in cancer pathology, and its modulation by environmental factors is the subject of many investigations. Numerous environmental toxins, alcohol, and hepatitis viruses can cause hepatocellular carcinoma (HCC), which is the most common form of liver cancer. Significant hyperactivation of Hh signaling has been observed in liver injury and cirrhosis which often leads to the development of HCC lesions. Moreover, Hh activity plays an important role in the progression of HCC. Here, we review findings relevant to our understanding of the role of Hh signaling in HCC pathogenesis.

Assessment of the stromal contribution to Sonic Hedgehog-dependent pancreatic adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) remains one of the most lethal malignancies. It is typically detected at an advanced stage, at which the therapeutic options are very limited. One remarkable feature of PDAC that contributes to its resilience to treatment is the extreme stromal activation seen in these tumors. Often, the vast majority of tumor bulk consists of non-tumor cells that together provide a tumor-promoting environment. One of the signals that maintains and activates the stroma is the developmental protein Sonic Hedgehog (SHH). As the disease progresses, tumor cells produce increasing amounts of SHH, which activates the surrounding stroma to aid in tumor progression. To better understand this response and identify targets for inhibition, we aimed to elucidate the proteins that mediate the SHH-driven stromal response in PDAC. For this a novel mixed-species coculture model was set up in which the cancer cells are human, and the stroma is modeled by mouse fibroblasts. In conjunction with next-generation sequencing we were able to use the sequence difference between these species to genetically distinguish between the epithelial and stromal responses to SHH. The stromal SHH-dependent genes from this analysis were validated and their relevance for human disease was subsequently determined in two independent patient cohorts. In non-microdissected tissue from PDAC patients, in which a large amount of stroma is present, the targets were confirmed to associate with tumor stroma versus normal pancreatic tissue. Patient survival analysis and immunohistochemistry identified CDA, EDIL3, ITGB4, PLAUR and SPOCK1 as SHH-dependent stromal factors that are associated with poor prognosis in PDAC patients. Summarizing, the presented data provide insight into the role of the activated stroma in PDAC, and how SHH acts to mediate this response. In addition, the study has yielded several candidates that are interesting therapeutic targets for a disease for which treatment options are still inadequate.

Inflammation and cancer stem cells

Cancer stem cells are becoming recognised as being responsible for metastasis and treatment resistance. The complex cellular and molecular network that regulates cancer stem cells and the role that inflammation plays in cancer progression are slowly being elucidated. Cytokines, secreted by tumour associated immune cells, activate the necessary pathways required by cancer stem cells to facilitate cancer stem cells progressing through the epithelial-mesenchymal transition and migrating to distant sites. Once in situ, these cancer stem cells can secrete their own attractants, thus providing an environment whereby these cells can continue to propagate the tumour in a secondary niche.

Menin directly represses Gli1 expression independent of canonical Hedgehog signaling

Multiple endocrine neoplasia type 1 (MEN-1), is a familial tumor syndrome resulting from mutations in the tumor suppressor gene menin (MEN1). Menin plays an essential role in both repressing and activating gene expression. However, it is not well understood how menin represses expression of multiple genes. Upon MEN1 excision, the transcription factor Gli1 and its target genes, including Ptch1 and c-Myc, were shown to be elevated in the absence of an apparent Hedgehog) pathway-activating ligand or when Smoothened (SMO), a key component of the pathway, is inhibited. Menin binds to the GLI1 promoter and recruits PRMT5, a histone arginine methyltransferase associated with transcriptional repression. Both PRMT5 binding and histone H4 arginine 3 methylation (H4R3m2s) are decreased at the GLI1 promoter in MEN1-excised cells. Moreover, MEN1 ablation resulted in increased binding of transcriptionally active Gli1 at the GLI1 promoter in a manner not influenced by the canonical Hedgehog signaling pathway. Inhibition of Gli1 by the small-molecule inhibitor GANT-61 led to decreased expression of Gli1 and its target genes in MEN1-depeleted cells. Furthermore, GANT-61 potently suppressed proliferation of MEN1-excised cells as compared with control cells. These findings uncover a novel epigenetic link whereby menin directly represses Gli1 expression, independent of the canonical Hedgehog signaling pathway, via PRMT5 and its repressive H4R3m2s mark.

IMPLICATIONS

Inhibition of GLI1 suppresses neuroendocrine tumors harboring mutations in the MEN1 gene.

Monoclonal antibodies and other targeted therapies for pancreatic cancer

Pancreatic cancer continues to be a challenging disease to treat because of its aggressive nature, advanced stage at the time of diagnosis, and limited treatment options that are available. Traditional cytotoxic chemotherapy provides modest benefit to patients with pancreatic adenocarcinoma. Recently, a FOLFIRINOX regimen revealed improved response in overall and progression-free survival over single-agent gemcitabine in metastatic pancreatic cancer, but there is still much needed advancement in the systemic treatment of pancreatic cancer. There is a growing interest in the development of novel agents, while our understanding of molecular pathogenesis of pancreatic adenocarcinoma continues to expand. With identification of various molecular pathways in pancreatic cancer tumorigenesis, potential targets for drug development have been pursued with the use of monoclonal antibodies and small-molecule inhibitors. Although preclinical studies with multiple targeted therapies demonstrated encouraging results in pancreatic cancer, only erlotinib, an epidermal growth factor receptor inhibitor, showed a marginal survival benefit in a phase III clinical trial, when combined with gemcitabine. As further signaling pathways and their importance in pancreatic cancer tumorigenesis are better understood, further clinical trials will need to be designed to study these targeted agents as single agents, in combination with other novel agents or in combination with cytotoxic chemotherapy. In this review, we present the current knowledge on targeted therapy in pancreatic adenocarcinoma and its application in clinical practice.

Sonic Hedgehog promotes tumor cell survival by inhibiting CDON pro-apoptotic activity

The Hedgehog signaling is a determinant pathway for tumor progression. However, while inhibition of the Hedgehog canonical pathway-Patched-Smoothened-Gli-has proved efficient in human tumors with activating mutations in this pathway, recent clinical data have failed to show any benefit in other cancers, even though Sonic Hedgehog (SHH) expression is detected in these cancers. Cell-adhesion molecule-related/down-regulated by Oncogenes (CDON), a positive regulator of skeletal muscle development, was recently identified as a receptor for SHH. We show here that CDON behaves as a SHH dependence receptor: it actively triggers apoptosis in the absence of SHH. The pro-apoptotic activity of unbound CDON requires a proteolytic cleavage in its intracellular domain, allowing the recruitment and activation of caspase-9. We show that by inducing apoptosis in settings of SHH limitation, CDON expression constrains tumor progression, and as such, decreased CDON expression observed in a large fraction of human colorectal cancer is associated in mice with intestinal tumor progression. Reciprocally, we propose that the SHH expression, detected in human cancers and previously considered as a mechanism for activation of the canonical pathway in an autocrine or paracrine manner, actually provides a selective tumor growth advantage by blocking CDON-induced apoptosis. In support of this notion, we present the preclinical demonstration that interference with the SHH-CDON interaction triggers a CDON-dependent apoptosis in vitro and tumor growth inhibition in vivo. The latter observation qualifies CDON as a relevant alternative target for anticancer therapy in SHH-expressing tumors.

Profile of vismodegib and its potential in the treatment of advanced basal cell carcinoma

Basal cell carcinoma (BCC) is the most common human malignancy. Recent advances in our understanding of the critical biologic pathways implicated in the development and progression of BCC have led to the development of the first molecular targeted therapy for this disease. The hedgehog pathway is mutated in virtually all patients with BCC and recent trials with vismodegib, an inhibitor of this pathway, have shown significant responses. This review will discuss the importance of the hedgehog pathway in the pathogenesis of BCC and describe in detail the pharmacology of vismodegib in relation to its activity in advanced BCC.

Cell mates: paracrine and stromal targets for prostate cancer therapy

After many years of limited treatment options for patients with metastatic castration-resistant prostate cancer (mCRPC), multiple systemic therapies are now available, providing patients with significant improvements in survival, symptom control and bone health. Most of the recent advances in this area have been based on better understanding of mCRPC biology, particularly with respect to the key role of androgen receptor signalling. However, most therapies are targeted towards the malignant epithelial cell component of the cancer and it should not be forgotten that cancer cells exist in close and symbiotic relationships with other components of the tumour. Paracrine and stromal signals are often critical to the growth of the cancer and represent new potential therapeutic targets that are separate from the malignant epithelial cells. The stroma produces numerous growth factors, including vascular endothelial growth factor family members, platelet-derived growth factors and fibroblast growth factors, which are all critical for tumour growth. Targeting prostate-cancer-associated fibroblasts in order to destroy the physical and functional scaffold of a cancer is also a logical approach. The interaction between prostate cancer and the immune system remains an active topic of basic and clinical research, with cytokines, chemokines and growth factors being potential targets for therapy. The biology of epithelial-mesenchymal transition and of circulating tumour cells might also provide insight into new therapeutic targets.

Hypoxia and metastasis in an orthotopic cervix cancer xenograft model

BACKGROUND

Hypoxia can promote tumor metastasis by mechanisms that are believed to result from changes in gene expression. The current study examined the role of putative metastatic genes regulated by cyclic hypoxia in relation to metastasis formation in orthotopic models of cervix cancer.

METHODS

Orthotopic tumors derived from ME180 human cervix cancer cells or from early generation human cervix cancer xenografts were exposed to cyclic hypoxic conditions during growth in vivo and tumor growth and lymphnode metastases were monitored. Expression of the chemokine receptor CXCR4 and various genes in the Hedgehog (Hh) pathway were inhibited using genetic (inducible shRNA vs CXCR4) small molecule (AMD3100) or antibody (5E1) treatment (CXCR4 and Hh genes, respectively) during tumor growth.

RESULTS

As reported previously, exposure of tumor bearing mice to cyclic hypoxia caused a reduction of tumor growth but a large increase in metastasis. Inhibition of CXCR4 or Hh gene activity during tumor growth further reduced primary tumor size and reduced lymphatic metastasis to levels below those seen in control mice exposed to normoxic conditions.

CONCLUSION

Blocking CXCR4 or Hh gene expression are potential therapeutic pathways for improving cervix cancer treatment.

Hedgehog signaling pathway and ovarian cancer

Epithelial ovarian carcinoma (EOC) is the most common form of ovarian malignancies and the most lethal gynecologic malignancy in the United States. To date, in spite of treatment to it with the extensive surgical debulking and chemotherapy, the prognosis of EOC remains dismal. Recently, it has become increasingly clear that in many instances, the signaling and molecular players that control development are the same, and when inappropriately regulated, drive tumorigenesis and cancer development. Here, we discuss the possible involvement of Hedgehog (Hh) pathway in the cellular regulation and development of cancer in the ovaries. Using the in vitro and in vivo assays developed has facilitated the dissection of the mechanisms behind Hh-driven ovarian cancers formation and growth. Based on recent studies, we propose that the inhibition of Hh signaling may interfere with spheroid-like structures in ovarian cancers. The components of the Hh signaling may provide novel drug targets, which could be explored as crucial combinatorial strategies for the treatment of ovarian cancers.

Hedgehog signaling in prostate cancer and its therapeutic implication

Activation of Hedgehog (Hh) signaling is implicated in the development and progression of several tumor types, including prostate cancer, which is still the most common non-skin malignancy and the third leading cause of cancer-related mortality in men in industrialized countries worldwide. Several studies have indicated that the Hh pathway plays a crucial role in the development as well as in the progression of this disease to more aggressive and even therapy-resistant disease states. Moreover, preclinical data have shown that inhibition of Hh signaling has the potential to reduce prostate cancer invasiveness and metastatic potential. Clinical trials investigating the benefit of Hh inhibitors in patients with prostate cancer have recently been initiated. However, acquired drug resistance has already been observed in other tumor types after long-term Hh inhibition. Therefore, combining Hh inhibitors with ionizing radiation, chemotherapy or other molecular targeted agents could represent an alternative therapeutic strategy. In this review, we will highlight the role of Hh signaling in the development and progression of prostate cancer and summarize the different therapeutic applications of Hedgehog inhibition.

LKB1 inhibits breast cancer partially through repressing the Hedgehog signaling pathway

Constitutive activation of the Hedgehog (Hh) signaling pathway has been implicated in the development of many human malignancies. Hh targets, such as Patched (PTCH), smoothened (SMO), Sonic hedgehog (SHH) and glioma-associated oncogene homologue 1 (GLI1), are markers of Hh signaling activation and expressed in most Hh-associated tumors. The protein kinase LKB1 has been shown to slow proliferation and induce cell-cycle arrest in many cell lines. In this study, we observed that activated LKB1 decreased the expression of factors related to Hh reporter activity in MDA-MB-231 breast cancer cells, including of SMO, SHH and GLI1. In contrast, LKB1 siRNA increased the expression of these target genes. The same results were shown to inhibit the Hh factors Sufu and Hip. Furthermore, we also observed negative correlation between LKB1 and glioma-associated oncogene homologue 1 (GLI1) in three breast cancer cell lines. Meanwhile, LKB1 siRNA rescued the inhibition of cell growth by 3-Keto-N-(aminoethyl-N'-aminocaproyldihydrocinnamoyl) cyclopamine (KAAD-cyclopamine), an antagonist of the Hh element SMO, which suggests that LKB1 acts as the downstream of SMO. In vivo, LKB1 siRNA increased tumor growth in the mammary fat pad, and the expression levels of Hh displayed similar results in vitro. Overexpression of the LKB1 protein in human breast cancers is associated with the expression of Hh. We found that breast carcinomas with detectable Hh had weak or undetectable expression of LKB1, whereas tumors that expressed high levels of LKB1 had undetectable Hh signaling. In this study, we find that LKB1 are negatively correlated with the expression of Hh related transcription factors. These findings suggest that LKB1 may inhibit tumorigenesis by regulating Hh signaling in certain cancers.

Discovery of small-molecule modulators of the Sonic Hedgehog pathway

The Hedgehog signaling pathway is involved in the development of multicellular organisms and, when deregulated, can contribute to certain cancers, among other diseases. The molecular characterization of the pathway, which has been enabled by small-molecule probes targeting its components, remains incomplete. Here, we report the discovery of two potent, small-molecule inhibitors of the Sonic Hedgehog (Shh) pathway, BRD50837 and BRD9526. Both compounds exhibit stereochemistry-based structure–activity relationships, a feature suggestive of a specific and selective interaction of the compounds with as-yet-unknown cellular target(s) and made possible by the strategy used to synthesize them as members of a stereochemically and skeletally diverse screening collection. The mechanism-of-action of these compounds in some ways shares similarities to that of cyclopamine, a commonly used pathway inhibitor. Yet, in other ways their mechanism-of-action is strikingly distinct. We hope that these novel compounds will be useful probes of this complex signaling pathway.

Carcinoma-associated fibroblasts: non-neoplastic tumour-promoting mesenchymal cells

Cancerous stroma coevolves alongside tumour progression, thereby promoting the malignant conversion of epithelial carcinoma cells. To date, an abundance of data have supported crucial roles of the tumour microenvironment (TME) in providing cancer cells with proliferative, migratory, survival and invasive propensities favouring the processes of tumourigenesis. The cancerous reactive stroma is frequently populated by a large number of myofibroblasts (MFs), which are activated, non-transformed fibroblasts expressing α-smooth muscle actin (α-SMA). MFs together with non-MF cells present in the tumour-associated stroma are collectively referred to as carcinoma-associated fibroblasts (CAFs), one of the major stromal cell types recognised in various human carcinomas. Recruitment of fibroblasts and/or their progenitors to a tumour mass and their subsequent transdifferentiation into MFs, as well as ongoing maintenance of their activated state, are believed to be essential processes facilitating tumour progression. However, the complex networks of signalling pathways mediating the phenotypic conversion into CAFs, as well as those underlying their tumour-promoting interactions with other tumour-constituting cells, have yet to be fully explored. Histopathological confirmation of the presence of large numbers of CAF MFs within TME and their altered gene expression profiles are known to be associated with disease progression and to serve as independent negative prognostic factors for a wide range of tumour types. In this review, we examine the current evidence shedding light on the emerging roles of tumour-promoting CAFs, cells that are pivotal for epithelial cancer development and progression, and discuss the therapeutic potential of targeting these cells.

Specific requirement of Gli transcription factors in Hedgehog-mediated intestinal development

Hedgehog (Hh) signaling is involved in multiple aspects of embryonic gut development, including mesenchymal growth and smooth muscle differentiation. The Gli family transcription factors is thought to collectively mediate Hh signaling in mammals. However, the function of different Gli proteins in gut development remains uncharacterized. Here, we genetically dissect the contribution of Gli transcriptional activation and de-repression in intestinal growth and patterning. We find that removal of the Gli3 repressor is dispensable for intestinal development and does not play a major role in Hh-controlled gut development. However, Gli2 activation is able to fully rescue the Smoothened (Smo)-null intestinal phenotype, suggesting that the Gli2 transcription factor is the main effector for Hh signaling in the intestine. To understand further the molecular mechanism underlying Hh/Gli function in the developing gut, we identify a subset of small leucine-rich glycoproteins (SLRPs) that may function downstream of Hh signaling in the mesenchyme. We show that osteoglycin, a SLRP, inhibits Hh-induced differentiation toward the smooth muscle lineage in C3H10T1/2 pluripotent mesenchymal cells. Taken together, our study reveals, for the first time, the distinct roles of Gli proteins in intestine development and suggests SLRPs as novel regulators of smooth muscle cell differentiation.

Nonhematopoietic cells represent a more rational target of in vivo hedgehog signaling affecting normal or acute myeloid leukemia progenitors

Recent work has shown that leukemic stem cell self-renewal in chronic myeloid leukemia is dependent on cell-intrinsic hedgehog (Hh) signaling, and early clinical trials suggest that targeting this pathway is also therapeutic in patients with acute myeloid leukemia (AML). In this study, we aimed to better understand Hh signaling in normal hematopoiesis and AML by molecularly and functionally analyzing more than 200 primary human AML patient samples compared with nonleukemic controls. Gene expression analysis indicated that Hh pathway transcripts were similarly regulated in AML and nonleukemic controls, regardless of whether samples were purified based on primitive phenotypes. Consistent with these results, pharmacologic inhibition of Smoothened (SMO) did not preferentially reduce in vitro colony formation of AML versus normal progenitors. Using a unique analytic approach, messenger RNA expression of membrane receptor SMO was found to be unexpectedly rare within all hematopoietic samples analyzed, which is indicative of heterogeneity at the level of Hh signaling machinery. In contrast, abundant SMO expression could be readily detected in the nonhematopoietic fraction of human and murine bone marrow (BM) cells. Our predictions of increased SMO(+) cell frequencies within nonhematopoietic BM fractions were further supported by single-cell protein analyses. Although we did not find support for cell-autonomous sensitivity of AML cells to Hh pathway inhibition, we alternatively suggest that nonhematopoietic BM cells represent an indirect target through which primitive normal and leukemic cells can be modulated. These findings suggest current approaches to applying Hh inhibition should be carefully reevaluated to account for BM niche cell regulation that might be selectively Hh responsive.

Roles for KRAS in pancreatic tumor development and progression

The Kras gene is mutated to an oncogenic form in most pancreatic tumors. However, early attempts to use this molecule as a specific biomarker of the disease, or inhibit its activity as a cancer therapy, failed. This left a situation in which everyone was aware of the association between this important oncogene and pancreatic cancer, but no one knew what to do about it. Recent findings have changed this picture-many assumptions made about KRAS and its role in pancreatic cancer were found to be incorrect. Several factors have contributed to increased understanding of the activities of KRAS, including creation of genetically engineered mouse models, which have allowed for detailed analyses of pancreatic carcinogenesis in an intact animal with a competent immune system. Cancer genome sequencing projects have increased our understanding of the heterogeneity of individual tumors. We also have a better understanding of which oncogenes are important for tumor maintenance and are therefore called "drivers." We review the advances and limitations of our knowledge about the role of Kras in development of pancreatic cancers and the important areas for future research.

Stem cell signaling as a target for novel drug discovery: recent progress in the WNT and Hedgehog pathways

One of the most exciting fields in biomedical research over the past few years is stem cell biology, and therapeutic application of stem cells to replace the diseased or damaged tissues is also an active area in development. Although stem cell therapy has a number of technical challenges and regulatory hurdles to overcome, the use of stem cells as tools in drug discovery supported by mature technologies and established regulatory paths is expected to generate more immediate returns. In particular, the targeting of stem cell signaling pathways is opening up a new avenue for drug discovery. Aberrations in these pathways result in various diseases, including cancer, fibrosis and degenerative diseases. A number of drug targets in stem cell signaling pathways have been identified. Among them, WNT and Hedgehog are two most important signaling pathways, which are the focus of this review. A hedgehog pathway inhibitor, vismodegib (Erivedge), has recently been approved by the US FDA for the treatment of skin cancer, while several drug candidates for the WNT pathway are entering clinical trials. We have discovered that the stem cell signaling pathways respond to traditional Chinese medicines. Substances isolated from herbal medicine may act specifically on components of stem cell signaling pathways with high affinities. As many of these events can be explained through molecular interactions, these phenomena suggest that discovery of stem cell-targeting drugs from natural products may prove to be highly successful.

Murine basal cell carcinoma leads to tumor-mediated alterations in endocrine Igf1 signaling

The intrinsic properties underlying cancer development are extensively studied while the effect of a cancer on the host is often overlooked. Activation of the Hedgehog (Hh) signaling pathway underlies a number of types of common human cancers, yet little is known concerning endocrine signaling in such tumors. Here, we investigated endocrine signaling in a murine model of basal cell carcinoma (BCC) of the skin, the most common cancer. BCCs were generated by the activation of Hh signaling resulting from the specific deletion of the Ptch1 gene in the developing epidermis. Subsequently, a severe growth deficiency was observed in the murine BCC model, and we identified a deficiency of circulating IGF1 (Igf1). We demonstrate that Hh pathway activation in murine BCC induces IGF binding proteins, thereby regulating Igf1 sequestration into the skin and skewing Igf endocrine signaling. Significantly, these results show that Hh-induced tumors can have endocrine effects on normal tissues that in turn can greatly impact the host. This study not only identifies that Igf is important in Hh-associated skin tumors but also exemplifies the need to consider endocrine signaling when interpreting complex in vivo tumor models.

Targeting Gli transcription activation by small molecule suppresses tumor growth

Targeted inhibition of Hedgehog signaling at the cell membrane has been associated with anti-cancer activity in preclinical and early clinical studies. Hedgehog signaling involves activation of Gli transcription factors that can also be induced by alternative pathways. In this study we identified an interaction between Gli proteins and a transcription co-activator TAF9, and validated its functional relevance in regulating Gli transactivation. We also describe a novel, synthetic small molecule, FN1-8, that efficiently interferes with Gli/TAF9 interaction and down-regulate Gli/TAF9 dependent transcriptional activity. More importantly, FN1-8 suppresses cancer cell proliferation in vitro and inhibits tumor growth in vivo. Our results suggest that blocking Gli transactivation, a key control point of multiple oncogenic pathways, may be an effective anti-cancer strategy.

Targeted therapies with chemoradiation in esophageal cancer: development and future directions

Targeted therapies have been studied in combination with chemoradiation therapy for esophageal and gastroesophageal junction cancers. To date, the Human Epidermal Growth Factor Receptor 2 (HER2) HER2, epidermal growth factor receptor, and vascular endothelial growth factor pathways have been most extensively studied in esophagogastric cancers. However, despite strong preclinical rationale and evidence of activity in other diseases, the efficacy of these agents has been mixed when studied in the metastatic setting or in combination with chemoradiation. In this review, the history of the development of targeted therapies in esophagogastric cancers is reviewed, with a specific focus on the incorporation of these agents with chemoradiation. Additionally, more recently identified targets of interest in esophagogastric cancers, including c-MET, heat shock protein 90, and Sonic hedgehog, are discussed in the context of chemoradiation.