Exploring vismodegib: A non-surgical breakthrough in the management of advanced periocular basal cell carcinoma

The management of periocular basal cell carcinoma (BCC) is challenging due to its proximity to the eyeball. Vismodegib, a Hedgehog pathway inhibitor, has emerged as a therapeutic option for locally advanced and metastatic BCC. To critically appraise the relevant evidence, we conducted a systematic review of observational and experimental studies assessing the efficacy and safety of vismodegib for periocular BCC. Thirty-seven trials, including 435 patients, were eligible. No randomized trials were retrieved. Complete and overall clinical response rates were 20-88 % and 68-100 %, respectively. Disease progression was observed at a maximum rate of 14 %. Recurrence rates varied between 0 % and 31 %. The most common side effects were muscle cramps, dysgeusia, weight loss and alopecia. Treatment with vismodegib improved health-related quality of life. In conclusion, vismodegib represents an important novel treatment for advanced periocular BCC, with good response rates and acceptable tolerability profile. Nevertheless, its full potential needs clarification through randomized controlled trials.

Affinity-based protein profiling identifies vitamin D3 as a heat shock protein 70 antagonist that regulates hedgehog transduction in murine basal cell carcinoma

Vitamin D3 (VD3) is a seco-steroid that inhibits the Hedgehog (Hh) signaling pathway. Initial studies suggested its anti-Hh activity results from direct inhibition of Smoothened, a seven-transmembrane cell surface receptor that is a key regulator of the Hh signaling cascade. More recently, a role for the Vitamin D Receptor in mediating inhibition of Hh-signaling by seco-steroid has been suggested. Herein, an affinity-based protein profiling study was carried out to better understand the cellular proteins that govern VD3-mediated anti-Hh activity. We synthesized a novel biotinylated VD3 analogue (8) for use as a chemical probe to explore cellular binding targets of the seco-steroidal scaffold. Through a series of pull-down experiments and follow up mass spectrum analyses, heat shock protein 70 (Hsp70) was identified as a primary binding protein of VD3. Hsp70 was validated as a binding target of VD3 through a series of biochemical and cellular assays. VD3 bound with micromolar affinity to Hsp70. In addition, both selective knockdown of Hsp70 expression and pharmacological inhibition of its activity with known Hsp70 inhibitors suppressed Hh-signaling transduction in murine basal cell carcinoma cells, suggesting that Hsp70 regulates proper Hh-signaling. Additional cellular assays suggest that VD3 and its seco-steroidal metabolites inhibit Hh-signaling through different mechanisms.

Assessment of various efficacy outcomes using ERIVANCE-like criteria in patients with locally advanced basal cell carcinoma receiving sonidegib: results from a preplanned sensitivity analysis

Background

The BOLT study for sonidegib, a Hedgehog pathway inhibitor (HHI) approved for patients with locally advanced basal cell carcinoma (laBCC) not amenable to curative surgery or radiotherapy, used modified Response Evaluation Criteria in Solid Tumors (mRECIST) for laBCC tumor evaluation. The ERIVANCE study for vismodegib, another HHI, used a composite RECIST endpoint of ≥30% reduction in externally visible tumor or radiographic dimension, or complete ulceration resolution. This preplanned sensitivity BOLT analysis evaluated efficacy outcomes using ERIVANCE-like criteria in patients with laBCC who received sonidegib 200 mg once daily.

Methods

This phase 2, double-blind study randomized patients 1:2 to sonidegib 200:800 mg daily, respectively. Key endpoints included objective response rate (ORR), duration of response (DOR), complete response (CR), partial response (PR), stable disease (SD), and progressive disease (PD). laBCC tumors were assessed by both mRECIST and ERIVANCE-like criteria. Per mRECIST, an overall response of CR was based on negative histology; photographic assessment of CR, PR (scar/fibrosis only), SD (scar/fibrosis only), or not available (NA); and a magnetic resonance imaging response of CR or NA. An overall response of CR was primarily based on negative histology using ERIVANCE-like criteria.

Results

Per mRECIST criteria, ORR (95% confidence interval [CI]) by central and investigator review for patients with laBCC (n = 66) was 56.1% (43.3–68.3%) and 71.2% (58.7–81.7%), respectively. CR per central review was achieved in 3 (4.5%) patients and PR, SD, and PD occurred in 34 (51.5%), 23 (34.8%), and 1 (1.5%) patient, respectively. Median (95% CI) DOR was 26.1 months (not estimable [NE]).

Using ERIVANCE-like criteria, efficacy outcomes per central and investigator review were higher, with an ORR (95% CI) of 60.6% (47.8–72.4%) and 74.2% (62.0–84.2%), respectively. CR per central review was reached in 14 (21.2%) patients and PR, SD, and PD occurred in 26 (39.4%), 20 (30.3%), and 1 (1.5%) patient, respectively. DOR was unchanged with a median (95% CI) of 26.1 months (NE).

Conclusions

Overall, applying ERIVANCE-like criteria to patients with laBCC receiving sonidegib 200 mg daily yielded higher response rates vs mRECIST criteria.

Trial registration

BOLT registration: ClinicalTrials.gov (NCT01327053) on March 30, 2011.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08968-1.

Effects of Sonidegib Following Dose Reduction and Treatment Interruption in Patients with Advanced Basal Cell Carcinoma During 42-Month BOLT Trial

Introduction

Sonidegib is a Hedgehog pathway inhibitor approved to treat locally advanced basal cell carcinoma and, depending on regulatory approval, metastatic basal cell carcinoma. Results from the BOLT study demonstrated robust efficacy and continued tolerability through 42 months. This analysis evaluated the impact of sonidegib dose reductions and interruptions in patients with advanced basal cell carcinoma through 42 months.

Methods

BOLT was a randomized, double-blind, multicenter, phase 2 study. Adults with no previous Hedgehog pathway inhibitor therapy were randomized 1:2 to sonidegib 200 or 800 mg once daily. Primary endpoint was objective response rate. Dose modifications were permitted in patients unable to tolerate the dosing schedule or if a treatment-related adverse event was suspected.

Results

The incidence of dose interruptions was similar between the 200- and 800-mg groups (68.4% vs 65.3%, respectively). Dose reductions occurred more frequently in patients receiving sonidegib 800 mg (36.7%) than 200 mg (16.5%). Overall response rate for all patients receiving sonidegib 200 mg daily was 48.1% and was similar to those of patients without dose reduction or interruption (48.5%) and patients with at least one dose reduction or interruption (46.2%).

Conclusion

Dose reductions and interruptions were practical and did not impact the efficacy of sonidegib. In patients with advanced basal cell carcinoma who necessitate long-term treatment, dose interruptions may be beneficial for continued treatment and disease control.

Trial registration: ClinicalTrials.gov identifier, NCT01327053.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13555-021-00619-4.

Switching Hedgehog inhibitors and other strategies to address resistance when treating advanced basal cell carcinoma

Although basal cell carcinoma (BCC) is often managed successfully with surgery, patients with locally advanced BCC (laBCC) or metastatic BCC (mBCC) who are not candidates for surgery or radiotherapy have limited treatment options. Most BCCs result from aberrant Hedgehog pathway activation in keratinocyte tumor cells, caused by sporadic or inherited mutations. Mutations in the patched homologue 1 gene that remove its inhibitory regulation of Smoothened homologue (SMO) or mutations in SMO that make it constitutively active, lead to Hedgehog pathway dysregulation and downstream activation of GLI1/2 transcription factors, promoting cell differentiation and proliferation. Hedgehog inhibitors (HHIs) block overactive signaling of this pathway by inhibiting SMO and are currently the only approved treatments for advanced BCC. Two small-molecule SMO inhibitors, vismodegib and sonidegib, have shown efficacy and safety in clinical trials of advanced BCC patients. Although these agents are effective and tolerable for many patients, HHI resistance occurs in some patients. Mechanisms of resistance include mutations in SMO, noncanonical cell identity switching leading to tumor cell resistance, and non-canonical pathway crosstalk causing Hedgehog pathway activation. Approaches to managing HHI resistance include switching HHIs, HHI and radiotherapy combination therapy, photodynamic therapy, and targeting Hedgehog pathway downstream effectors. Increasing understanding of the control of downstream effectors has identified new therapy targets and potential agents for evaluation in BCC. Identification of biomarkers of resistance or response is needed to optimize HHI use in patients with advanced BCC. This review examines HHI resistance, its underlying mechanisms, and methods of management for patients with advanced BCC.

The Role of Actin in Muscle Spasms in a Case Series of Patients with Advanced Basal Cell Carcinoma Treated with a Hedgehog Pathway Inhibitor

Basal cell carcinoma (BCC) is the most common cancer globally, with the incidence increasing worldwide by approximately 1% annually. While most cases of BCC can be treated surgically, advanced BCC often poses treatment challenges for patients unsuitable for, or refractory to, radiotherapy and surgery. Since the majority of cases of BCC demonstrate Hedgehog signaling hyperactivation, Hedgehog pathway inhibitors provide durable treatment options and improved clinical outcomes for patients with advanced BCC. One of the most common adverse events seen in patients taking Hedgehog inhibitors includes muscle spasms, which are hypothesized to occur because of calcium influx into the muscle cells. Here we present a case series of patients with muscle spasms during treatment with sonidegib and propose an alternate etiology related to increased actin expression.

Expression of Glioma-associated oncogene homolog 1 as biomarker with sonidegib in advanced basal cell carcinoma

The pivotal BOLT (Basal cell carcinoma Outcomes with LDE225 [sonidegib] Treatment) study established the durable efficacy and manageable toxicity of sonidegib 200 mg once daily (QD) through 42 months in patients with advanced basal cell carcinoma (BCC). This secondary analysis used expression of Glioma-associated oncogene homolog 1 (GLI1) as a biomarker to assess the extent of Hedgehog pathway inhibition by sonidegib in patients with locally advanced BCC (laBCC) and metastatic BCC (mBCC). The study enrolled 230 patients, 79 and 151 receiving sonidegib 200 and 800 mg QD, respectively. At week 17, GLI1 expression was reduced from baseline by a median percentage (95% confidence interval) of 88.7% (54.6%-93.0%) and 97.0% (77.5%-98.9%) for aggressive laBCC, 97.5% (80.3%-98.8%) and 95.0% (80.7%-97.5%) for nonaggressive laBCC, and 99.1% (96.4%-99.6%) and 99.3% (95.9%-99.9%) for mBCC in the 200 and 800 mg groups, respectively. Substantial repression of GLI1 was observed in patient subgroups stratified by age, sex, BCC cytological subtype, Eastern Cooperative Oncology Group performance status, lesion site, baseline number of BCCs, and prior radiotherapy. Results support further studies on the inhibition of Hedgehog pathway genes by sonidegib in patients with laBCC and mBCC.

Treatment of periocular basal cell carcinoma with neoadjuvant vismodegib

Purpose

To report a case of a locally advanced periocular basal cell carcinoma treated with neoadjuvant Vismodegib therapy prior to surgery.

Observations

A 63-year-old female presented to the oculoplastics clinic with biopsy-proven basal cell carcinoma of the right periorbital region causing significant cicatricial ectropion of the right lower eyelid. The medial canthal lesion involved nearly the entire right lower eyelid with extension onto the cheek, the medial half of the right upper eyelid, the palpebral and bulbar conjunctiva, as well as the right lacrimal system. CT imaging was suggestive of involvement of the extraocular muscles and other post-septal tissues. Fortunately, the patient had no metastatic disease. The extent of the tumor would have necessitated aggressive resection to achieve surgical cure. However, the patient preferred to attempt globe-sparing therapy with a goal of preserving cosmesis as much as possible. Various treatment options were discussed with the patient, including the use of Vismodegib, and the patient elected to pursue this treatment strategy. The goal of Vismodegib treatment was to reduce the tumor size enough to permit surgical resection of all tumor without significantly affecting cosmesis. After 11 months of treatment with Vismodegib, the tumor size had reduced significantly to the point where surgical intervention with minimal disfigurement could be offered. The patient underwent multidisciplinary approach with Mohs micrographic excision of the tumor paired with oculoplastic reconstructive surgery resulting in negative margins and satisfactory cosmetic results.

Conclusions and importance

Although addition study is required regarding Vismodegib as a primary or adjuvant therapeutic approach to periorbital basal cell carcinoma, this case illustrates the potential usefulness of this drug as an option in this context. This case provides information that may help the comprehensive ophthalmologist or oculoplastic specialist in counseling patients with locally advanced periorbital basal cell carcinoma.

Medulloblastoma: Molecular understanding, treatment evolution, and new developments

Medulloblastoma (MB) is the most common childhood malignant brain tumor, accounting for approximately 20% of all pediatric central nervous system tumors. Current standard treatments involving surgical interventions followed by craniospinal irradiation and adjuvant chemotherapy have severe motor and cognitive defects. Therefore, individualized treatment regimens with reduced toxicity designed according to the presence of specific oncogenic 'driver' genes are urgently demanded. To this end, recent genetic and epigenetic findings have advanced the classification of MB into the international consensus of four distinct MB molecular subgroups (WNT, SHH, Group 3, and Group 4) based on their respective molecular and histopathological characteristics. More recent studies have indicated that up to seven molecular subgroups exist in childhood MB. Moreover, studies on the inter- and intra-tumoral features of the four subgroups revealed that each subgroup contains variant subtypes. These results have greatly helped risk stratification of MB patients at diagnosis and significantly improved clinical treatment options. Herein, we highlight the recent advances and challenges associated with MB classification, and the development of therapeutic treatments targeting novel subgroup-specific molecular and epigenetic factors, especially those in the SHH-driven MB tumors.

Efficacy, rate of tumor response, and safety of a short course (12-24 weeks) of oral vismodegib in various histologic subtypes (infiltrative, nodular, and superficial) of high-risk or locally advanced basal cell carcinoma, in an open-label, prospective case series clinical trial

BACKGROUND

Vismodegib demonstrated 60% response rates in the ERIVANCE trial. Basal cell carcinoma has various histopathologies. Their effect on response is unclear.

OBJECTIVE

The purpose of this study was to determine whether basal cell carcinoma histopathology affected vismodegib response.

METHODS

This phase 2b, single-center, prospective case series study compared the efficacy of vismodegib in infiltrative, nodular, and superficial basal cell carcinomas treated for 12 or 24 weeks in 27 patients. Patients had 1 target lesion and up to 3 nontarget lesions.

RESULTS

Twenty-seven patients were enrolled, with 65 tumors (27 target lesions/38 nontarget lesions). At 24 weeks, most basal cell carcinomas achieved histologic clearance, with positive biopsy results in 10.5% of target lesions, 30.4% of nontarget lesions, and 21.4% overall. No statistical differences were observed between histopathologic subtypes. One hundred percent of patients experienced an adverse event, 94% grade 1 or 2. The most common adverse events were dysgeusia/loss of taste (86%), muscle spasms (82%), and alopecia (71%). Clinically progressive disease during treatment was low (1.5%). Two patients had recurrence within 1 year of treatment.

LIMITATIONS

Limitations included sample size of basal cell carcinoma histopathologic subtypes, sampling punch biopsies, and short follow-up.

CONCLUSIONS

Basal cell histopathologic subtype did not significantly affect response to vismodegib. Each subtype was observed to completely respond at 12 weeks of therapy, 24 weeks, or both.

Assessment of quality of life using Skindex-16 in patients with advanced basal cell carcinoma treated with vismodegib in the STEVIE study

Health-related quality of life (HRQoL) data are limited in patients with advanced basal cell carcinoma. To report HRQoL outcomes based on STEVIE (NCT01367665), a phase 2 study of vismodegib safety in patients with metastatic BCC or locally advanced BCC that is unsuitable for surgery or radiotherapy. Skindex-16 and MD Anderson Symptom Inventory (MDASI) questionnaires were completed at baseline and at three subsequent visits. Clinically meaningful improvement was defined as a ≥10-point decrease from baseline (Skindex-16) or improvement of at least 3 points from baseline (MDASI). HRQoL-evaluable patients with locally advanced BCC (n = 730) had ≥10-point improvements in Skindex-16 emotion domain scores at all time points. Changes in symptom and function scores in these patients or in any domain scores at any time point in patients with metastatic BCC (n = 10) were not clinically meaningful. Of 10 patients with symptomatic metastatic BCC at baseline, six had ≥3-point improvements in MDASI symptom severity. Skindex-16 and MDASI showed improvement in HRQoL in vismodegib-treated patients with locally advanced or metastatic BCC or BCC.

A phase Ib study to assess the efficacy and safety of vismodegib in combination with ruxolitinib in patients with intermediate- or high-risk myelofibrosis

BACKGROUND

The JAK inhibitor (JAKi) ruxolitinib is standard treatment for myelofibrosis (MF), but some patients are unresponsive. Pre-clinical and clinical data suggest that addition of a Hedgehog pathway inhibitor (HPI) to ruxolitinib might improve response. Vismodegib is an HPI approved for treatment of locally advanced and metastatic basal cell carcinoma. The MYLIE study assessed the safety and efficacy of combining ruxolitinib with vismodegib in ruxolitinib-naive patients with MF and characterized the pharmacokinetics (PK) of vismodegib in this setting.

METHODS

In this phase Ib study, ten patients with intermediate- or high-risk primary or secondary MF received open-label vismodegib (150 mg/day orally) and ruxolitinib (15 or 20 mg orally twice daily, depending on baseline platelet count) for up to 48 weeks, or until withdrawal or discontinuation. PK samples were collected throughout the study for comparison with other patient populations. Efficacy outcomes at week 24 included spleen response (≥ 35% reduction in volume by imaging) and improvement in bone marrow fibrosis by central and investigator assessment, symptom response (≥ 50% reduction in Myeloproliferative Neoplasm Symptom Assessment Form Total Symptom score), and anemia response (per International Working Group for Myeloproliferative Neoplasms Research and Treatment revised response criteria).

RESULTS

As of November 17, 2017, eight patients had completed 48 weeks of treatment with vismodegib and ruxolitinib; two discontinued treatment early. At week 24 (± 1 week), three patients experienced a spleen response by central review and no patients showed a 1-grade improvement in bone marrow fibrosis by central review. Five patients experienced symptom response at week 24, and no patients experienced an anemia response. The most common adverse events were muscle spasm (100% of patients), alopecia (70%), dysgeusia (50%), thrombocytopenia (50%), and nausea (40%); these events were predominantly grade 1/2. Three patients experienced a total of six serious adverse events.

CONCLUSIONS

The combination of vismodegib and ruxolitinib was tolerable and no new safety signals were seen, but there was no evidence that the addition of vismodegib to ruxolitinib improved any of the efficacy outcome measures assessed. Further evaluation of this combination will not be pursued.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT02593760 . Registered November 2, 2015.

Safety and efficacy of vismodegib in patients aged ≥65 years with advanced basal cell carcinoma

Because many patients with unresectable basal cell carcinoma (BCC) are aged ≥65 years, this study explores the efficacy and safety of vismodegib in these patients with locally advanced (la) or metastatic (m) basal cell carcinoma (BCC) in the ERIVANCE BCC trial and the expanded access study (EAS).We compared patients aged ≥65 years to patients aged <65 years taking vismodegib 150 mg/day, using descriptive statistics for response and safety. Patients aged ≥65 years (laBCC/mBCC) were enrolled in ERIVANCE BCC (33/14) and EAS (27/26). Investigator-assessed best overall response rate in patients ≥65 and <65 years was 46.7%/35.7% and 72.7%/52.6% (laBCC/mBCC), respectively, in ERIVANCE BCC and 45.8%/33.3% and 46.9%/28.6%, respectively, in EAS. These differences were not clinically meaningful. Safety was similar in both groups, although those aged ≥65 years had a higher percentage of grade 3-5 adverse events than those aged <65 years. Vismodegib demonstrated similar clinical activity and adverse events regardless of age.

Vismodegib in patients with advanced basal cell carcinoma: Primary analysis of STEVIE, an international, open-label trial

BACKGROUND

The SafeTy Events in VIsmodEgib study (STEVIE, ClinicalTrials.gov, NCT01367665), assessed safety and efficacy of vismodegib-a first-in-class Hedgehog pathway inhibitor demonstrating clinical benefit in advanced basal cell carcinoma (BCC)-in a patient population representative of clinical practice. Primary analysis data are presented.

PATIENTS AND METHODS

Patients with locally advanced or metastatic BCC received oral vismodegib 150 mg/d until progressive disease, unacceptable toxicity, or withdrawal. Primary objective was safety. Efficacy variables were assessed as secondary end-points.

RESULTS

Evaluable adult patients (N = 1215, 1119 locally advanced; 96 metastatic BCC) from 36 countries were treated; 147 patients (12%) remained on study at time of reporting. Median (range) treatment duration was 8.6 (0-44) months. Most patients (98%) had ≥1 treatment-emergent adverse event (TEAE). The incidence of the most common TEAEs was consistent with reports in previous analyses. No association between creatine phosphokinase (CPK) abnormalities and muscle spasm was observed. Serious TEAEs occurred in 289 patients (23.8%). Exposure ≥12 months did not lead to increased incidence or severity of new TEAEs. The majority of the most common TEAEs ongoing at time of treatment discontinuation resolved by 12 months afterwards, regardless of Gorlin syndrome status. Response rates (investigator-assessed) in patients with histologically confirmed measurable baseline disease were 68.5% (95% confidence interval (CI) 65.7-71.3) in patients with locally advanced BCC and 36.9% (95% CI 26.6-48.1) in patients with metastatic BCC.

CONCLUSIONS

The primary analysis of STEVIE demonstrates that vismodegib is tolerable in typical patients in clinical practice; safety profile is consistent with that in previous reports. Long-term exposure was not associated with worsening severity/frequency of TEAEs. Investigator-assessed response rates showed high rate of tumour control. CLINICALTRIALS.GOV: NCT01367665.

Hedgehog pathway inhibition in advanced basal cell carcinoma: latest evidence and clinical usefulness

Treatment of locally advanced basal cell carcinomas (laBCCs) with large, aggressive, destructive, and disfiguring tumors, or metastatic disease is challenging. Dysregulation of the Hedgehog (Hh) signaling pathway has been identified in the vast majority of basal cell carcinomas (BCCs). There are two United States Food and Drug Administration (US FDA)-approved Hh pathway inhibitors (HPIs) that exhibit antitumor activity in advanced BCC with an acceptable safety profile. Common adverse effects include muscle spasms, dysgeusia, alopecia, fatigue, nausea and weight loss.

Discovery and preclinical development of vismodegib

INTRODUCTION

Vismodegib is the first Hedgehog (Hh) pathway inhibitor approved in the US for the treatment of adults with metastatic or locally advanced basal cell carcinoma (BCC). It was approved by the US FDA on 30 January 2012, and by the European Commission on 12 July 2013, for the treatment of adult patients with symptomatic metastatic BCC, or locally advanced BCC inappropriate for surgery or radiotherapy. Vismodegib selectively inhibits the Hh signaling pathway, binding to and inhibiting a critical signal-transducing component of the pathway, Smoothened (SMO). Vismodegib was discovered by Genentech, Inc., under a collaboration agreement with Curis, Inc.

AREAS COVERED

This article reviews the development of vismodegib from its discovery, preclinical pharmacology and validation to the clinical pharmacokinetics and validation in Phase I and II clinical investigations. We also provide a survey of other Hh pathway inhibitors in clinical development.

EXPERT OPINION

The authors' experience in target-based drug discovery suggests that vismodegib's path to the clinic deserves some reflection to identify key steps that have contributed to its success. Targeting the Hh pathway with vismodegib blocks the abberant signaling caused by mutational inactivation of the negative regulator PTCH1 or mutational activation of SMO. Vismodegib gives physicians a treatment option for patients with locally advanced or metastatic BCC for whom surgery or radiation is not recommended.

Targeting of the Hedgehog signal transduction pathway suppresses survival of malignant pleural mesothelioma cells in vitro

OBJECTIVE

The present study sought to determine whether the Hedgehog (Hh) pathway is active and regulates the cell growth of cultured malignant pleural mesothelioma (MPM) cells and to evaluate the efficacy of pathway blockade using smoothened (SMO) antagonists (SMO inhibitor GDC-0449 or the antifungal drug itraconazole [ITRA]) or Gli inhibitors (GANT61 or the antileukemia drug arsenic trioxide [ATO]) in suppressing MPM viability.

METHODS

Selective knockdown of SMO to inhibit Hh signaling was achieved by small interfering RNA in 3 representative MPM cells. The growth inhibitory effect of GDC-0449, ITRA, GANT61, and ATO was evaluated in 8 MPM lines, with cell viability quantified using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Cell death was determined by annexinV/propidium iodide staining and flow cytometry.

RESULTS

SMO small interfering RNA mediated a two- to more than fivefold reduction of SMO and Gli1 gene expression as determined by real-time quantitative reverse-transcriptase polymerase chain reaction, indicating significant Hh pathway blockade. This was associated with significantly reduced cell viability (34% ± 7% to 61% ± 14% of nontarget small interfering RNA controls; P = .0024 to P = .043). Treating MPM cells with Hh inhibitors resulted in a 1.5- to 4-fold reduction of Gli1 expression. These 4 Hh antagonists strongly suppressed MPM cell viability. More importantly, ITRA, ATO, GANT61 induced significant apoptosis in the representative MPM cells.

CONCLUSIONS

Hh signaling is active in MPM and regulates cell viability. ATO and ITRA were as effective as the prototypic SMO inhibitor GDC-0449 and the Gli inhibitor GANT61 in suppressing Hh signaling in MPM cells. Pharmaceutical agents Food and Drug Administration-approved for other indications but recently found to have anti-Hh activity, such as ATO or ITRA, could be repurposed to treat MPM.