Treatment of medulloblastoma with hedgehog pathway inhibitor GDC-0449

Protein kinase A activation inhibits oncogenic Sonic hedgehog signalling and suppresses basal cell carcinoma of the skin

Basal cell carcinoma of the skin (BCC) is caused by constitutive activation of the Sonic hedgehog (Shh) pathway, mainly through mutations either in the Shh receptor Patched (PTCH) or in its co-receptor Smoothened (Smo). Inhibitors of this pathway that are currently in clinical trials inhibit Smo. However, mutations in Smo can result in resistance to these inhibitors. To target most BCCs and avoid acquired resistance because of Smo mutations, inhibiting the Shh-pathway downstream of Smo is critical. Attractive downstream targets would be at the level of Gli proteins, the transcriptional activators of this pathway in BCCs. Previously it has been shown that Gli1 and Gli2, when phosphorylated by protein kinase A (PKA), are targeted for proteosomal degradation. Here we show that PKA activation via the cAMP agonist forskolin is sufficient to completely abolish oncogenic Smo activity in vitro. In an inducible BCC mouse model due to a Smo mutation that confers resistance to current Smo inhibitors, topical forskolin treatment significantly reduced Gli1 mRNA levels and resulted in strongly suppressed BCC tumor growth. Our data show that forskolin inhibits the growth of even those BCCs that are resistant to Smo inhibitors and provide a proof-of-principle framework for the development of topically applied human skin-permeable novel pharmacologic inhibitors of oncogenic Shh-signaling through PKA activation.

The pre-clinical absorption, distribution, metabolism and excretion properties of IPI-926, an orally bioavailable antagonist of the hedgehog signal transduction pathway

1. IPI-926 is a novel semisynthetic cyclopamine derivative that is a potent and selective Smoothened inhibitor that blocks the hedgehog signal transduction pathway. 2. The in vivo clearance of IPI-926 is low in mouse and dog and moderate in monkey. The volume of distribution is high across species. Oral bioavailability ranges from moderate in monkey to high in mouse and dog. Predicted human clearance using simple allometry is low (24 L h(-1)), predicted volume of distribution is high (469 L) and predicted half-life is long (20 h). 3. IPI-926 is highly bound to plasma proteins and has minimal interaction with human α-1-acid glycoprotein. 4. In vitro metabolic stability ranges from stable to moderately stable. Twelve oxidative metabolites were detected in mouse, rat, dog, monkey and human liver microsome incubations and none were unique to human. 5. IPI-926 is not a potent reversible inhibitor of CYP1A2, 2C8, 2C9 or 3A4 (testosterone). IPI-926 is a moderate inhibitor of CYP2C19, 2D6 and 3A4 (midazolam) with KI values of 19, 16 and 4.5 µM, respectively. IPI-926 is both a substrate and inhibitor (IC50 = 1.9 µM) of P-glycoprotein. 6. In summary, IPI-926 has desirable pre-clinical absorption, distribution, metabolism and excretion properties.

Single and multiple dose intravenous and oral pharmacokinetics of the hedgehog pathway inhibitor vismodegib in healthy female subjects

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

While recent publications have suggested the pharmacokinetics (PK) of vismodegib appear to be non-linear, there has not been a report describing the mechanisms of non-linearity.

WHAT THIS STUDY ADDS

This study provides evidence that two separate processes, namely, solubility-limited absorption and concentration-dependent plasma protein binding, can explain the non-linear PK of vismodegib. This study provides quantitative results which can account for the lower than expected accumulation of vismodegib with continuous daily dosing.

AIM

Vismodegib has demonstrated clinical activity in patients with advanced basal cell carcinoma. The pharmacokinetics (PK) of vismodegib are non-linear. The objective of this study was to determine whether vismodegib PK change following repeated dosing by administering a tracer intravenous (i.v.) dose of (14) C-vismodegib with single and multiple oral doses.

METHODS

Healthy post menopausal female subjects (n= 6/group) received either a single or daily 150 mg vismodegib oral dose with a (14) C-labelled 10 µg i.v. bolus dose administered 2 h after the single or last oral dose (day 7). Plasma samples were assayed for vismodegib by LC-MS/MS and for (14) C-vismodegib by accelerator mass spectrometry.

RESULTS

Following a single i.v. dose, mean clearance, volume of distribution and absolute bioavailability were 43.4 ml h(-1) , 16.4 l and 31.8%, respectively. Parallel concentration-time profiles following single oral and i.v. administration of vismodegib indicated elimination rate limited PK. Following i.v. administration at steady-state, mean clearance and volume of distribution were 78.5 ml h(-1) and 26.8 l, respectively. Comparison of i.v. PK parameters after single and multiple oral dosing showed similar half-life, increased clearance and volume of distribution (81% and 63% higher, respectively) and decreased bioavailability (77% lower) after repeated dosing. Relative to single dose, the unbound fraction of vismodegib increased 2.4-fold with continuous daily dosing.

CONCLUSION

Vismodegib exhibited a long terminal half-life after oral and i.v. administration, moderate absolute bioavailability and non-linear PK after repeated dosing. Results from this study suggest that the non-linear PK of vismodegib result from two separate, non-linear processes, namely solubility limited absorption and high affinity, saturable plasma protein binding.

Aberrant patterns of H3K4 and H3K27 histone lysine methylation occur across subgroups in medulloblastoma

Recent sequencing efforts have described the mutational landscape of the pediatric brain tumor medulloblastoma. Although MLL2 is among the most frequent somatic single nucleotide variants (SNV), the clinical and biological significance of these mutations remains uncharacterized. Through targeted re-sequencing, we identified mutations of MLL2 in 8 % (14/175) of MBs, the majority of which were loss of function. Notably, we also report mutations affecting the MLL2-binding partner KDM6A, in 4 % (7/175) of tumors. While MLL2 mutations were independent of age, gender, histological subtype, M-stage or molecular subgroup, KDM6A mutations were most commonly identified in Group 4 MBs, and were mutually exclusive with MLL2 mutations. Immunohistochemical staining for H3K4me3 and H3K27me3, the chromatin effectors of MLL2 and KDM6A activity, respectively, demonstrated alterations of the histone code in 24 % (53/220) of MBs across all subgroups. Correlating these MLL2- and KDM6A-driven histone marks with prognosis, we identified populations of MB with improved (K4+/K27-) and dismal (K4-/K27-) outcomes, observed primarily within Group 3 and 4 MBs. Group 3 and 4 MBs demonstrate somatic copy number aberrations, and transcriptional profiles that converge on modifiers of H3K27-methylation (EZH2, KDM6A, KDM6B), leading to silencing of PRC2-target genes. As PRC2-mediated aberrant methylation of H3K27 has recently been targeted for therapy in other diseases, it represents an actionable target for a substantial percentage of medulloblastoma patients with aggressive forms of the disease.

Protein-bound polysaccharide decreases invasiveness and proliferation in pancreatic cancer by inhibition of hedgehog signaling and HIF-1α pathways under hypoxia

To develop an effective therapeutic approach to pancreatic ductal adenocarcinoma (PDAC), we focused on the antitumor mechanism of protein-bound polysaccharide (PSK) under hypoxia. PSK decreased proliferation in PDAC cells under hypoxia but not normoxia. PSK also showed anti-tumor effects in vivo, inhibited invasiveness of PDAC cells, and decreased the expression of HIF-1α and hedgehog (Hh) signaling-related molecules under hypoxia. Inhibition of HIF-1α and Hh signaling reduced proliferation and invasiveness in PDAC cells under hypoxia. In conclusion, we found new PSK-related pathways in invasiveness and proliferation in PDAC under hypoxia. PSK may be a promising therapeutic drug to treat refractory PDAC.

New drugs for children and adolescents with cancer: the need for novel development pathways

Despite major progress in the past 40 years, 20% of children with cancer die from the disease, and 40% of survivors have late adverse effects. Innovative, safe, and effective medicines are needed. Although regulatory initiatives in the past 15 years in the USA and Europe have been introduced, new drug development for children with cancer is insufficient. Children and families face major inequity between countries in terms of access to innovative drugs in development. Hurdles and bottlenecks are well known-eg, small numbers of patients, the complexity of developing targeted agents and their biomarkers for selected patients, limitations of US and EU regulations for paediatric medicines, insufficient return on investment, and the global economic crisis facing drug companies. New drug development pathways could efficiently address the challenges with innovative methods and trial designs, investment in biology and preclinical research, new models of partnership and funding including public-private partnerships and precompetitive research consortia, improved regulatory requirements, initiatives and incentives that better address these needs, and increased collaboration between paediatric oncology cooperative groups worldwide. Increased cooperation between all stakeholders-academia, parents' organisations and advocacy groups, regulatory bodies, pharmaceutical companies, philanthropic organisations, and government-will be essential.

How can attrition rates be reduced in cancer drug discovery?

Attrition is a major issue in anticancer drug development with up to 95% of drugs tested in Phase I trials not reaching a marketing authorisation making the drug development process enormously costly and inefficient. It is essential that this problem is addressed throughout the whole drug development process to improve efficiency which will ultimately result in increased patient benefit with more profitable drugs. The approach to reduce cancer drug attrition rates must be based on three pillars. The first of these is that there is a need for new pre-clinical models which can act as better predictors of success in clinical trials. Furthermore, clinical trials driven by tumour biology with the incorporation of predictive and pharmacodynamic biomarkers would be beneficial in drug development. Finally, there is a need for increased collaboration to combine the unique strengths between industry, academia and regulators to ensure that the needs of all stakeholders are met.

Biological and clinical implications of cancer stem cells in primary brain tumors

Despite therapeutic advances, glioblastoma multiforme (GBM) remains a lethal disease. The infiltrative nature of this disease and the presence of a cellular population resistant to current medical treatments account for the poor prognosis of these patients. Growing evidence indicates the existence of a fraction of cancer cells sharing the functional properties of adult stem cells, including self-renewal and a greater ability to escape chemo-radiotherapy-induced death stimuli. Therefore, these cells are commonly defined as cancer stem cells (GBM-SCs). The initial GBM-SC concept has been challenged, and refined according to the emerging molecular taxonomy of GBM. This allowed to postulate the existence of multiple CSC types, each one driving a given molecular entity. Furthermore, it is becoming increasingly clear that GBM-SCs thrive through a dynamic and bidirectional interaction with the surrounding microenvironment. In this article, we discuss recent advances in GBM-SC biology, mechanisms through which these cells adapt to hostile conditions, pharmacological strategies for selectively killing GBM-SCs, and how novel CSC-associated endpoints have been investigated in the clinical setting.

Mutations in the hedgehog pathway genes SMO and PTCH1 in human gastric tumors

The causal role of the hedgehog pathway in cancer has been best documented in basal cell carcinoma of the skin. To assess potential DNA alterations of the hedgehog pathway in gastric cancer, we sequenced SMO and PTCH1 genes in a set of 39 gastric tumors. Tumors were classified by histology based on the Lauren classification and Sanger sequencing was performed to obtain full length coding sequences. Genomic instability was evident in these tumors as a number of silent or missense mutations were found. In addition to those that are potential germline polymorphisms, we found three SMO missense mutations, and one PTCH1 frameshift mutation that are novel and have not been documented in basal cell carcinoma. Mutations were found in both intestinal and diffuse type gastric tumors as well as in tumors that exhibit both intestinal and diffuse features. mRNA expression of hedgehog pathway genes was also examined and their levels do not indicate unequivocal higher pathway activity in tumors with mutations than those without. In summary, SMO and/or PTCH1 mutations are present at low frequency in different histologic subtypes of gastric tumors and these do not appear to be driver mutations.

Combination of ponatinib with Hedgehog antagonist vismodegib for therapy-resistant BCR-ABL1-positive leukemia

PURPOSE

The Hedgehog signaling pathway is a key regulator of cell growth and differentiation during development. Whereas the Hedgehog pathway is inactive in most normal adult tissues, Hedgehog pathway reactivation has been implicated in the pathogenesis of several neoplasms including BCR-ABL1-positive leukemia. The clear link between the Hedgehog pathway and BCR-ABL1-positive leukemia led to an effort to identify small molecules to block the pathway.

EXPERIMENTAL DESIGN

We investigated the combined effects of vismodegib and ponatinib, a pan-ABL1 kinase inhibitor, in nonobese diabetic/severe-combined immunodeficiency (NOD/SCID) repopulating T315I BCR-ABL1-positive cells in vitro and in vivo.

RESULTS

We observed that combination with vismodegib and ponatinib helps to eliminate therapy-resistant NOD/SCID repopulating T315I BCR-ABL1-positive cells. The percentage of CD19-positive leukemia cells in peripheral blood was significantly lower in vismodegib + ponatinib-treated mice than that of the vehicle or ponatinib alone (P < 0.001). Spleen weights were also lower in vismodegib + ponatinib-treated mice than in ponatinib alone (P < 0.05). Overall tumor burden, as assessed by BCR-ABL mRNA from bone marrow cells, was significantly lower in vismodegib + ponatinib-treated mice than in ponatinib alone (P < 0.005). We also found that vismodegib significantly reduced BCR-ABL1-positive leukemia cell self-renewal in vitro as well as during serial transplantation in vivo.

CONCLUSIONS

The combination with a Smo inhibitor and ABL1 tyrosine kinase inhibitors may help eliminate therapy-resistant T315I BCR-ABL1-positive leukemia cells. Our preclinical results indicate that vismodegib has potential as an important option for controlling minimal residual cells in BCR-ABL1-positive leukemia.

Itraconazole and arsenic trioxide inhibit Hedgehog pathway activation and tumor growth associated with acquired resistance to smoothened antagonists

Recognition of the multiple roles of Hedgehog signaling in cancer has prompted intensive efforts to develop targeted pathway inhibitors. Leading inhibitors in clinical development act by binding to a common site within Smoothened, a critical pathway component. Acquired Smoothened mutations, including SMO(D477G), confer resistance to these inhibitors. Here, we report that itraconazole and arsenic trioxide, two agents in clinical use that inhibit Hedgehog signaling by mechanisms distinct from that of current Smoothened antagonists, retain inhibitory activity in vitro in the context of all reported resistance-conferring Smoothened mutants and GLI2 overexpression. Itraconazole and arsenic trioxide, alone or in combination, inhibit the growth of medulloblastoma and basal cell carcinoma in vivo, and prolong survival of mice with intracranial drug-resistant SMO(D477G) medulloblastoma.

Smoothing out drug resistance

Smoothened inhibitors have emerged as successful treatment alternatives for Hedgehog pathway-dependent tumors, but they are linked with the appearance of drug resistance. In this issue of Cancer Cell, Kim and colleagues overcome such resistance by combining approved drugs itraconazole and arsenic trioxide, thus opening a path toward new treatment options.

Multidisciplinary care of patients with brain tumors

Patients with brain tumors are some of the most complex patients in the medical system, necessitating treatment teams of multiple subspecialists for optimal care. This article examines the roles of these subspecialists, with the goal of summarizing standard-of-care practices, recent therapeutic advances, and ongoing clinical investigations within each subspecialty.

Hedgehog signaling pathway in ovarian cancer

Despite advances in surgical and chemotherapeutic treatment options, less than 50% of patients with advanced-stage ovarian cancer survive five years after initial diagnosis. In this regard, novel treatment approaches are warranted utilizing molecularly targeted therapies directed against particular components of specific signaling pathways which are required for tumor development and progression. One molecular pathway of interest is the hedgehog (Hh) signaling pathway. Activation of the Hh pathway has been observed in several cancer types, including ovarian cancer. This review highlights the crucial role of Hh signaling in the development and progression of ovarian cancer and might lead to a better understanding of the Hh signaling in ovarian tumorigenesis, thus encouraging the investigation of novel targeted therapies.

Hedgehog signalling pathway: carcinogenesis and targeted therapy

Hedgehog signalling pathway has not only a critical role in cell proliferation,differentiation and tissue polarity at embryonic period but also has a vital role in stem cell proliferation, tissue healing and carcinogenesis. Recent research has increased our understanding of this pathway and its relation to other signalling pathways. In addition, a large number of studies confirmed the alteration of Hh signalling pathway in various types of human malignancies including basal cell carcinomas, medulloblastomas, lung, gastrointestinal, ovarian, breast, prostate cancers and leukemia. More than 50 small biomolecules have been introduced which have inhibitory effects on Hh signalling pathway. Although, in many tumors some acceptable results have been showed in phase I clinical trial, closer studies are required to improve drug bioavailability, to decrease the side effects and to find the right small molecules for specific types of cancers, considering patients overall benefits as well.

Toward the goal of personalized therapy in pancreatic cancer by targeting the molecular phenotype

The purpose of this article is to provide a critical review of the molecular alterations in pancreatic cancer that are clinically investigated as therapeutic targets and their potential impact on clinical outcomes. Adenocarcinoma of exocrine pancreas is generally associated with poor prognosis and the conventional therapies are marginally effective. Advances in understanding the genetic regulation of normal and neoplastic development of pancreas have led to development and clinical evaluation of new therapeutic strategies that target the signaling pathways and molecular alterations in pancreatic cancer. Applications have begun to utilize the genetic targets as biomarkers for prediction of therapeutic responses and selection of treatment options. The goal of accomplishing personalized tumor-specific therapy with tolerable side effects for patients with pancreatic cancer is hopefully within reach in the foreseeable future.

Vismodegib: a promising drug in the treatment of basal cell carcinomas

Hedgehog pathway signaling is important for embryonic development; however, inappropriate reactivation of this pathway in adults has been linked to several forms of cancer. Vismodegib (Erivedge™), a first-in-class hedgehog pathway inhibitor, blocks the pathway by inhibiting the activity of the signaling protein SMO. Preclinical studies have provided promising indications of potential tumor-reducing activity in several cancers. Thus far, clinical pharmacology and Phase I studies have demonstrated the unique pharmacokinetic profile of vismodegib, its efficacy in certain types of tumors and a generally tolerable adverse-event profile. A pivotal Phase II clinical trial confirmed the favorable benefit:risk profile of vismodegib in advanced basal cell carcinoma.

Mechanisms of acquired resistance to targeted cancer therapies

Drugs that target genomically defined vulnerabilities in human tumors have now been clinically validated as effective cancer therapies. However, the relatively rapid acquisition of resistance to such treatments that is observed in virtually all cases significantly limits their utility and remains a substantial challenge to the clinical management of advanced cancers. As molecular mechanisms of resistance have begun to be elucidated, new strategies to overcome or prevent the development of resistance have begun to emerge. In some cases, specific mutational mechanisms contribute directly to acquired drug resistance, and in other cases it appears that nonmutational and possibly epigenetic mechanisms play a significant role. This article discusses the various genetic and nongenetic mechanisms of acquired drug resistance that have been reported in the context of 'rationally targeted' drug therapies.

Hedgehog signaling pathway and its targets for treatment in basal cell carcinoma

Basal cell carcinoma (BCC) of the skin is the most common type of cancer and accounts for up to 40% of all cancers in the US, with a growing incidence rate over recent decades in all developed countries. Surgery is curative for most patients, although it leaves unaesthetic scars, but those that develop locally advanced or metastatic BCC require different therapeutic approaches. Furthermore, patients with BCC present a high risk of developing additional tumors. The increasing economic burden and the morbidity of BCC render primary interest in the development of targeted treatments for this disease. Among the molecular signals involved in the development of BCC, the critical role of the morphogenetic Hedgehog (Hh) pathway has become evident. This pathway is found altered and activated in almost all BCCs, both sporadic and inherited. Given the centrality of the Hh pathway in the pathophysiology of BCC, the primary efforts to identify molecular targets for the topical or systemic treatment of this cancer have focused on the Hh components. Several Hh inhibitors have been so far identified - from the first identified natural cyclopamine to the recently Food and Drug Administration-approved synthetic vismodegib - most of which target the Hh receptor Smoothened (either its function or its translocation to the primary cilium). Other molecules await further characterization (bisamide compounds), while drugs currently approved for other diseases such as itraconazole (an antimicotic agent) and vitamin D3 have been tested on BCC with encouraging results. The outcomes of the numerous ongoing clinical trials are expected to expand the field in the very near future. Further research is needed to obtain drugs targeting downstream components of the Hh pathway (eg, Gli) or to exploit combinatorial therapies (eg, with phosphatidylinositol 3-kinase inhibitors or retinoids) in order to overcome potential drug resistance.

Molecular subgroups of medulloblastoma

Recent efforts at stratifying medulloblastomas based on their molecular features have revolutionized our understanding of this morbidity. Collective efforts by multiple independent groups have subdivided medulloblastoma from a single disease into four distinct molecular subgroups characterized by disparate transcriptional signatures, mutational spectra, copy number profiles and, most importantly, clinical features. We present a summary of recent studies that have contributed to our understanding of the core medulloblastoma subgroups, focusing largely on clinically relevant discoveries that have already, and will continue to, shape research.

Vismodegib: in locally advanced or metastatic basal cell carcinoma

Vismodegib is the first Hedgehog pathway inhibitor to be approved in the US, where it is indicated for the treatment of adults with metastatic basal cell carcinoma (BCC), or with locally advanced BCC that has recurred following surgery or who are not candidates for surgery, and who are not candidates for radiation. Vismodegib selectively and potently inhibits the Hedgehog signalling pathway by binding to Smoothened, thereby inhibiting the activation of Hedgehog target genes. Oral vismodegib was effective in the treatment of patients with locally advanced (n = 63) or metastatic (n = 33) BCC, according to the results of an ongoing, noncomparative, multinational, pivotal, phase II trial (ERIVANCE BCC). In this trial (using a clinical cutoff date of 26 November 2010), the independent review facility overall response rate was 42.9% in patients with locally advanced BCC and 30.3% in patients with metastatic BCC. In both patients with locally advanced BCC and those with metastatic BCC, the median duration of response was 7.6 months and median progression-free survival was 9.5 months. Oral vismodegib had an acceptable tolerability profile in patients with advanced BCC.

Medulloblastomics: the end of the beginning

The division of medulloblastoma into different subgroups by microarray expression profiling has dramatically changed our perspective of this malignant childhood brain tumour. Now, the availability of next-generation sequencing and complementary high-density genomic technologies has unmasked novel driver mutations in each medulloblastoma subgroup. The implications of these findings for the management of patients are readily apparent, pinpointing previously unappreciated diagnostic and therapeutic targets. In this Review, we summarize the 'explosion' of data emerging from the application of modern genomics to medulloblastoma, and in particular the recurrent targets of mutation in medulloblastoma subgroups. These data are currently making their way into clinical trials as we seek to integrate conventional and molecularly targeted therapies.

Vismodegib (erivedge) for advanced Basal cell carcinoma

Vismodegib (Erivedge) for advanced basal cell carcinoma.

It's about time: lessons for solid tumors from chronic myelogenous leukemia therapy

The use of imatinib in chronic myelogenous leukemia (CML) transformed the disease, rapidly changing the median survival from 4 years to at least 20 years. In this review, we outline the causes of this revolution, including the identification of a critical driving molecular aberration, BCR-ABL, and the development of a potent and specific inhibitor, imatinib. Equally important was the timing of the targeted therapy, specifically its administration to patients with newly diagnosed disease. In solid tumors, targeted therapies are often both developed and used in metastatic malignancies after conventional approaches have failed. We postulate that this strategy is similar to using imatinib in blast-crisis CML, in which response rates are less than 15%, all patients relapse, and median survival remains only about 1 year. We hypothesize that the imatinib-led revolution in CML, including the critically important factor of timing, may be applicable to other cancers as well. Therefore, it will be important to use promising targeted therapies in the earliest phases of biomarker-defined solid tumors, before metastatic progression, to determine if outcomes can be significantly improved and, thus, establish if the success of imatinib in CML is an anomaly or a paradigm.

Hedgehog pathway inhibition radiosensitizes non-small cell lung cancers

PURPOSE

Despite improvements in chemoradiation, local control remains a major clinical problem in locally advanced non-small cell lung cancer. The Hedgehog pathway has been implicated in tumor recurrence by promoting survival of tumorigenic precursors and through effects on tumor-associated stroma. Whether Hedgehog inhibition can affect radiation efficacy in vivo has not been reported.

METHODS AND MATERIALS

We evaluated the effects of a targeted Hedgehog inhibitor (HhAntag) and radiation on clonogenic survival of human non-small cell lung cancer lines in vitro. Using an A549 cell line xenograft model, we examined tumor growth, proliferation, apoptosis, and gene expression changes after concomitant HhAntag and radiation. In a transgenic mouse model of Kras(G12D)-induced and Twist1-induced lung adenocarcinoma, we assessed tumor response to radiation and HhAntag by serial micro-computed tomography (CT) scanning.

RESULTS

In 4 human lung cancer lines in vitro, HhAntag showed little or no effect on radiosensitivity. By contrast, in both the human tumor xenograft and murine inducible transgenic models, HhAntag enhanced radiation efficacy and delayed tumor growth. By use of the human xenograft model to differentiate tumor and stromal effects, mouse stromal cells, but not human tumor cells, showed significant and consistent downregulation of Hedgehog pathway gene expression. This was associated with increased tumor cell apoptosis.

CONCLUSIONS

Targeted Hedgehog pathway inhibition can increase in vivo radiation efficacy in lung cancer preclinical models. This effect is associated with pathway suppression in tumor-associated stroma. These data support clinical testing of Hedgehog inhibitors as a component of multimodality therapy for locally advanced non-small cell lung cancer.

Control of stem cells and cancer stem cells by Hedgehog signaling: pharmacologic clues from pathway dissection

Hedgehog is a key morphogen regulating embryonic development and tissue repair. Remarkably, when misregulated, it leads to tumorigenesis. Hedgehog signaling is triggered by binding of ligands with transmembrane receptor Ptch and is subsequently mediated by transcriptional effectors belonging to the Gli family, whose functions is tuned by a number of molecular interactions and post-synthetic modifications. The complex of these regulatory circuitries provides a tight control of developmental processes, mainly involving the modulation of genes determining the fate of stem cells. Similarly, Hedgehog regulates cancer stem cells fostering tumorigenesis. To this regard, these processes represent promising targets for novel therapeutic strategies aiming at the control of stemness reactivation and maintenance in cancer.

Hedgehog signaling inhibition by the small molecule smoothened inhibitor GDC-0449 in the bone forming prostate cancer xenograft MDA PCa 118b

BACKGROUND

Hedgehog signaling is a stromal-mesenchymal pathway central to the development and homeostasis of both the prostate and the bone. Aberrant Hedgehog signaling activation has been associated with prostate cancer aggressiveness. We hypothesize that Hedgehog pathway is a candidate therapeutic target in advanced prostate cancer. We confirm increased Hedgehog signaling in advanced and bone metastatic castrate resistant prostate cancer and examine the pharmacodynamic effect of Smoothened inhibition by the novel reagent GDC-0449 in an experimental prostate cancer model.

METHODS

Hedgehog signaling component expression was assessed in tissue microarrays of high grade locally advanced and bone metastatic disease. Male SCID mice subcutaneously injected with the bone forming xenograft MDA PCa 118b were treated with GDC-0449. Hedgehog signaling in the tumor microenvironment was assessed by proteomic and species specific RNA expression and compared between GDC-0449 treated and untreated animals.

RESULTS

We observe Hedgehog signaling in high grade locally advanced and bone marrow infiltrating disease. Evidence of paracrine activation of Hedgehog signaling in the tumor xenograft, was provided by increased Sonic Hedgehog expression in human tumor epithelial cells, coupled with increased Gli1 and Patched1 expression in the murine stromal compartment, while normal murine stroma did not exhibit Hh signaling expression. GDC-0449 treatment attenuated Hh signaling as evidenced by reduced expression of Gli1 and Ptch1. Reduction in proliferation (Ki67) was observed with no change in tumor volume.

CONCLUSIONS

GDC-0449 treatment is pharmacodynamically effective as evidenced by paracrine Hedgehog signaling inhibition and results in tumor cell proliferation reduction. Understanding these observations will inform the clinical development of therapy based on Hedgehog signaling inhibition.

Targeting the hedgehog pathway: role in cancer and clinical implications of its inhibition

The Hedgehog (Hh) pathway is a signaling cascade that is evolutionally highly conserved and plays an important role in embryonic pattern formation and stem cell response to tissue damage. Given the pivotal role the Hh pathway plays in embryonic development in terms of proliferation and differentiation, it is not surprising that it has also been implicated in tumorigenesis and tumor growth acceleration in a vast variety of malignancies. This article summarizes the mechanism of Hh pathway signal transduction, discusses the models of pathway activation, reviews the clinical data using Hh inhibitors, and discusses challenges to the development of pathway inhibitors.

A randomized phase II trial of vismodegib versus placebo with FOLFOX or FOLFIRI and bevacizumab in patients with previously untreated metastatic colorectal cancer

PURPOSE

Vismodegib, a Hedgehog pathway inhibitor, has preclinical activity in colorectal cancer (CRC) models. This trial assessed the efficacy, safety, and pharmacokinetics of adding vismodegib to first-line treatment for metastatic CRC (mCRC).

EXPERIMENTAL DESIGN

Patients were randomized to receive vismodegib (150 mg/day orally) or placebo, in combination with FOLFOX or FOLFIRI chemotherapy plus bevacizumab (5 mg/kg) every 2 weeks until disease progression or intolerable toxicity. The primary endpoint was progression-free survival (PFS). Key secondary objectives included evaluation of predictive biomarkers and pharmacokinetic drug interactions.

RESULTS

A total of 199 patients with mCRC were treated on protocol (124 FOLFOX, 75 FOLFIRI). The median PFS hazard ratio (HR) for vismodegib treatment compared with placebo was 1.25 (90% CI: 0.89-1.76; P = 0.28). The overall response rates for placebo-treated and vismodegib-treated patients were 51% (90% CI: 43-60) and 46% (90% CI: 37-55), respectively. No vismodegib-associated benefit was observed in combination with either FOLFOX or FOLFIRI. Increased tumor tissue Hedgehog expression did not predict clinical benefit. Grade 3 to 5 adverse events reported for more than 5% of patients that occurred more frequently in the vismodegib-treated group were fatigue, nausea, asthenia, mucositis, peripheral sensory neuropathy, weight loss, decreased appetite, and dehydration. Vismodegib did not alter the pharmacokinetics of FOLFOX, FOLFIRI, or bevacizumab.

CONCLUSIONS

Vismodegib does not add to the efficacy of standard therapy for mCRC. Compared with placebo, treatment intensity was lower for all regimen components in vismodegib-treated patients, suggesting that combined toxicity may have contributed to lack of efficacy.

Molecular diagnostic strategies: a role in the practice of dermatology

Molecular diagnostic strategies are gaining wider acceptance and use in dermatology and dermatopathology as more practitioners in this field develop an understanding of the principles and applications of genomic technologies. Molecular testing is facilitating more accurate diagnosis, staging, and prognostication, in addition to guiding the selection of appropriate treatment, monitoring of therapy, and identification of novel therapeutic targets, for a wide variety of skin diseases.

Macrocyclic Hedgehog Pathway Inhibitors: Optimization of Cellular Activity and Mode of Action Studies

Macrocyclic Hedgehog (Hh) pathway inhibitors have been discovered with improved potency and maximal inhibition relative to the previously reported macrocycle robotnikinin. Analogues were prepared using a modular and efficient build-couple-pair (BCP) approach, with a ring-closing metathesis step to form the macrocyclic ring. Varying the position of the macrocycle nitrogen and oxygen atoms provided inhibitors with improved activity in cellular assays; the most potent analogue was 29 (BRD-6851), with an IC₅₀ of 0.4 μM against C3H10T1/2 cells undergoing Hh-induced activation, as measured by Gli1 transcription and alkaline phosphatase induction. Studies with Patched knockout (Ptch^–/–) cells and competition studies with the Smoothened (Smo) agonists SAG and purmorphamine demonstrate that in contrast to robotnikinin, select analogues are Smo antagonists.

Distinct roles for fibroblast growth factor signaling in cerebellar development and medulloblastoma

Cerebellar granule neurons are the most abundant neurons in the brain, and a critical element of the circuitry that controls motor coordination and learning. In addition, granule neuron precursors (GNPs) are thought to represent cells of origin for medulloblastoma, the most common malignant brain tumor in children. Thus, understanding the signals that control the growth and differentiation of these cells has important implications for neurobiology and neurooncology. Our previous studies have shown that proliferation of GNPs is regulated by Sonic hedgehog (Shh), and that aberrant activation of the Shh pathway can lead to medulloblastoma. Moreover, we have demonstrated that Shh-dependent proliferation of GNPs and medulloblastoma cells can be blocked by basic fibroblast growth factor (bFGF). But while the mitogenic effects of Shh signaling have been confirmed in vivo, the inhibitory effects of bFGF have primarily been studied in culture. Here, we demonstrate that mice lacking FGF signaling in GNPs exhibit no discernable changes in GNP proliferation or differentiation. In contrast, activation of FGF signaling has a potent effect on tumor growth: treatment of medulloblastoma cells with bFGF prevents them from forming tumors following transplantation, and inoculation of tumor-bearing mice with bFGF markedly inhibits tumor growth in vivo. These results suggest that activators of FGF signaling may be useful for targeting medulloblastoma and other Shh-dependent tumors.

Inhibition of hedgehog signaling for the treatment of murine sclerodermatous chronic graft-versus-host disease

Chronic graft-versus-host disease (cGVHD) is a prognosis limiting complication of allogeneic stem cell transplantation. The molecular mechanisms underlying cGVHD are incompletely understood, and targeted therapies are not yet established for clinical use. Here we examined the role of the hedgehog pathway in sclerodermatous cGVHD. Hedgehog signaling was activated in human and murine cGVHD with increased expression of sonic hedgehog and accumulation of the transcription factors Gli-1 and Gli-2. Treatment with LDE223, a highly selective small-molecule antagonist of the hedgehog coreceptor Smoothened (Smo), abrogated the activation of hedgehog signaling and protected against experimental cGVHD. Preventive therapy with LDE223 almost completely impeded the development of clinical and histologic features of sclerodermatous cGVHD. Treatment with LDE223 was also effective, when initiated after the onset of clinical manifestations of cGVHD. Hedgehog signaling stimulated the release of collagen from cultured fibroblasts but did not affect leukocyte influx in murine cGVHD, suggesting direct, leukocyte-independent stimulatory effects on fibroblasts as the pathomechanism of hedgehog signaling in cGVHD. Considering the high morbidity of cGVHD, the current lack of efficient molecular therapies for clinical use, and the availability of well-tolerated inhibitors of Smo, targeting hedgehog signaling might be a novel strategy for clinical trials in cGVHD.

A phase II, randomized, placebo-controlled study of vismodegib as maintenance therapy in patients with ovarian cancer in second or third complete remission

PURPOSE

Hedgehog pathway inhibition has been suggested as a potential maintenance treatment approach in ovarian cancer through disruption of tumor-stromal interactions. Vismodegib is an orally available Hedgehog pathway inhibitor with clinical activity in advanced basal cell carcinoma and medulloblastoma. This phase II, randomized, double-blind, placebo-controlled trial was designed to provide a preliminary estimate of efficacy in patients with ovarian cancer in second or third complete remission (CR).

EXPERIMENTAL DESIGN

Patients with recurrent epithelial ovarian, fallopian tube, or primary peritoneal cancer in second or third CR were randomized 1:1 to vismodegib (GDC-0449; 150 mg daily) or placebo three to 14 weeks after completing chemotherapy. Treatment continued until radiographic progression or toxicity. The primary endpoint was investigator-assessed progression-free survival (PFS).

RESULTS

One hundred four patients were randomized to vismodegib (n = 52) or placebo (n = 52); median PFS was 7.5 months and 5.8 months, respectively [HR 0.79; 95% confidence interval (CI), 0.46-1.35]. The HR was 0.66 (95% CI, 0.36-1.20) for second CR patients (n = 84) and 1.79 (95% CI, 0.50-6.48) for third CR patients (n = 20). The most common adverse events in the vismodegib arm were dysgeusia/ageusia, muscle spasms, and alopecia. Grade 3/4 adverse events occurred in 12 patients (23.1%) with vismodegib and six (11.5%) with placebo. Hedgehog expression was detected in 13.5% of archival tissues.

CONCLUSIONS

In this study, the sought magnitude of increase in PFS was not achieved for vismodegib maintenance versus placebo in patients with ovarian cancer in second or third CR. The frequency of Hedgehog ligand expression was lower than expected.

Cancer stem cells: in the line of fire

Most tumours appear to contain a sub-population(s) of self-renewing and expanding stem cells known as cancer stem cells (CSCs). The CSC model proposes that CSCs are at the apex of a hierarchically organized cell population, somewhat akin to normal tissue organization. Selection pressures may also facilitate the stochastic clonal expansion of sub-sets of cancer cells that may co-exist with CSCs and their progeny, moreover the trait of stemness may be more fluid than hitherto expected, and cells may switch between the stem and non-stem cell state. A large body of evidence points to the fact that CSCs are particularly resistant to radiotherapy and chemotherapy. In this review we discuss the basis of such resistance that highlights the roles of ABC transporters, aldehyde dehydrogenase (ALDH) activity, intracellular signalling pathways, the DNA damage response, hypoxia and proliferative quiescence as being significant determinants. In the light of such observations, we outline strategies for the successful eradication of CSCs, including targeting the self-renewal controlling pathways (Wnt, Notch and Hedgehog), ALDH activity and ABC transporters, blocking epithelial mesenchymal transition (EMT), differentiation therapy and niche targeting.

Childhood medulloblastoma: the paradigm shift in molecular stratification and treatment profile

Medulloblastoma is the most common malignant brain tumor of childhood, accounting for nearly 25% to 30% of primary central nervous system tumors in children younger than 18 years of age. Risk stratification into low and high risk categories has been based on age of clinical presentation, extent of postsurgical residual tumor, and disease dissemination. The World Health Organization (WHO) in 2007 recognized 5 histological subtypes as classic, anaplastic, large cell, desmoplastic/nodular, and medulloblastoma with extensive nodularity. Recent work with gene expression profiling along with histological classification has generated a novel combined histopathological and molecular stratification scheme into 4 subgroups (Wnt, Shh, group 3, and group 4). This could now help to identify patients who might benefit from dose escalation and de-escalation of therapy. Restratification brings optimism in treating these patients as scholars now have the ability to profile a more targeted therapy approach. This review discusses the literature regarding this new research endeavor.

Targeting the inhibitor of apoptosis proteins as a novel therapeutic strategy in medulloblastoma

Medulloblastoma is the most common malignant brain tumor of childhood. Novel therapeutic strategies are urgently needed to overcome cytotoxic resistance. We hypothesized that antiapoptotic signals contribute to resistance and that treatment with proapoptotic agents could increase the efficacy of conventional therapies. A PCR array was used to assess the status of the apoptotic signaling pathway in medulloblastoma cells after treatment with cytotoxic chemotherapy. Treatment with cisplatin led to the upregulation of antiapoptotic signals, including inhibitor of apoptosis proteins (IAP), in medulloblastoma cells. We subsequently investigated the synergistic effect of a small-molecule IAP inhibitor, LBW242, in combination with cisplatin and/or radiotherapy in three human medulloblastoma cell lines and 5 short term primary patient medulloblastoma cultures. The addition of LBW242 to chemotherapy resulted in significantly increased antitumor activity with a similar effect observed in combination with radiotherapy. Measurement of caspase-8 and -9 activity indicated that the synergy resulted from induction of both the intrinsic and extrinsic apoptotic pathways. Apoptosis was confirmed by Annexin V staining and activation of caspases 3/7. Xenograft models were used to evaluate the mechanism of action and efficacy in vivo. The combination therapy significantly reduced the tumor burden in a medulloblastoma xenograft model and TUNEL analysis in a medulloblastoma orthograft confirmed in vivo induction of apoptosis. These findings support the strategy of targeting IAPs in combination with cytotoxic therapy as a novel treatment strategy for patients with medulloblastoma.

Identification of a novel Smoothened antagonist that potently suppresses Hedgehog signaling

The Hedgehog signaling pathway plays an essential role in embryo development and adult tissue homeostasis, in regulating stem cells and is abnormally activated in many cancers. Given the importance of this signaling pathway, we developed a novel and versatile high-throughput, cell-based screening platform using confocal imaging, based on the role of β-arrestin in Hedgehog signal transduction, that can identify agonists or antagonist of the pathway by a simple change to the screening protocol. Here we report the use of this assay in the antagonist mode to identify novel antagonists of Smoothened, including a compound (A8) with low nanomolar activity against wild-type Smo also capable of binding the Smo point mutant D473H associated with clinical resistance in medulloblastoma. Our data validate this novel screening approach in the further development of A8 and related congeners to treat Hedgehog related diseases, including the treatment of basal cell carcinoma and medulloblastoma.

Attenuation of early liver fibrosis by pharmacological inhibition of smoothened receptor signaling

Hedgehog (Hh) signaling is involved in the pathogenesis of liver fibrosis. It has been previously shown that Hh-inhibitor cyclopamine (CYA) can reduce liver fibrosis in rats. However, CYA is not stable in vivo, which limits its clinical application. This study compares the antifibrotic potential of two known Hh antagonists, vismodegib (GDC-0449, abbreviated to GDC) and CYA. GDC is a synthetic molecule presently in clinical cancer trials and has been reported to be safe and efficacious. These drugs attenuated early liver fibrosis in common bile duct ligated rats, improved liver function, and prevented hepatic stellate cell (HSC) activation, thereby suppressing epithelial to mesenchymal transition (EMT). While both CYA and GDC increased the number of proliferating cell nuclear antigen positive liver cells in vivo, only CYA increased Caspase-3 expression in HSCs in rat livers, suggesting that while GDC and CYA effectively attenuate early liver fibrosis, their hepatoprotective effects may be mediated through different modes of action. Thus, GDC has the potential to serve as a new therapeutic agent for treating early liver fibrosis.

Subgroup-specific structural variation across 1,000 medulloblastoma genomes

Medulloblastoma, the most common malignant paediatric brain tumour, is currently treated with nonspecific cytotoxic therapies including surgery, whole-brain radiation, and aggressive chemotherapy. As medulloblastoma exhibits marked intertumoural heterogeneity, with at least four distinct molecular variants, previous attempts to identify targets for therapy have been underpowered because of small samples sizes. Here we report somatic copy number aberrations (SCNAs) in 1,087 unique medulloblastomas. SCNAs are common in medulloblastoma, and are predominantly subgroup-enriched. The most common region of focal copy number gain is a tandem duplication of SNCAIP, a gene associated with Parkinson's disease, which is exquisitely restricted to Group 4α. Recurrent translocations of PVT1, including PVT1-MYC and PVT1-NDRG1, that arise through chromothripsis are restricted to Group 3. Numerous targetable SCNAs, including recurrent events targeting TGF-β signalling in Group 3, and NF-κB signalling in Group 4, suggest future avenues for rational, targeted therapy.

Small molecule inhibitors of the hedgehog signaling pathway for the treatment of cancer

Over the past decade, the Hedgehog signaling pathway has attracted considerable interest because the pathway plays important roles in the tumorigenesis of several types of cancer as well as developmental processes. It has also been observed that Hedgehog signaling regulates the proliferation and self-renewal of cancer stem cells. A great number of Hedgehog pathway inhibitors have been discovered through small molecule screens and subsequent medicinal chemistry efforts. Among the inhibitors, several Smo antagonists have reached the clinical trial phase. It has been proved that the inhibition of Hedgehog signaling with Smo antagonists is beneficial to cancer patients with basal cell carcinoma and medulloblastoma. In this review, we provide an overview of Hedgehog pathway inhibitors with focusing on the preclinical and/or clinical efficacy and molecular mechanisms of these inhibitors.

Response to inhibition of smoothened in diverse epithelial cancer cells that lack smoothened or patched 1 mutations

Hedgehog (HH) pathway Smoothened (Smo) inhibitors are active against Gorlin syndrome-associated basal cell carcinoma (BCC) and medulloblastoma where Patched (Ptch) mutations occur. We interrogated 705 epithelial cancer cell lines for growth response to the Smo inhibitor cyclopamine and for expressed HH pathway-regulated species in a linked genetic database. Ptch and Smo mutations that respectively conferred Smo inhibitor response or resistance were undetected. Previous studies revealed HH pathway activation in lung cancers. Therefore, findings were validated using lung cancer cell lines, transgenic and transplantable murine lung cancer models, and human normal-malignant lung tissue arrays in addition to testing other Smo inhibitors. Cyclopamine sensitivity most significantly correlated with high cyclin E (P=0.000009) and low insulin-like growth factor binding protein 6 (IGFBP6) (P=0.000004) levels. Gli family members were associated with response. Cyclopamine resistance occurred with high GILZ (P=0.002) expression. Newer Smo inhibitors exhibited a pattern of sensitivity similar to cyclopamine. Gain of cyclin E or loss of IGFBP6 in lung cancer cells significantly increased Smo inhibitor response. Cyclin E-driven transgenic lung cancers expressed a gene profile implicating HH pathway activation. Cyclopamine treatment significantly reduced proliferation of murine and human lung cancers. Smo inhibition reduced lung cancer formation in a syngeneic mouse model. In human normal-malignant lung tissue arrays cyclin E, IGFBP6, Gli1 and GILZ were each differentially expressed. Together, these findings indicate that Smo inhibitors should be considered in cancers beyond those with activating HH pathway mutations. This includes tumors that express genes indicating basal HH pathway activation.