Propranolol promotes accelerated and dysregulated adipogenesis in hemangioma stem cells

Potential Role of Pig UCP3 in Modulating Adipocyte Browning via the Beta-Adrenergic Receptor Signaling Pathway

Adipose tissue plays an important role in regulating body temperature and metabolism, with white adipocytes serving as storage units for energy. Recent research focused on the browning of white adipocytes (beige adipocytes), causing thermogenesis and lipolysis. The process of browning is linked to the activation of uncoupling protein (UCP) expression, which can be mediated by the β3 adrenergic receptor pathway. Transcriptional factors, such as peroxisome proliferator activated receptor γ (PPARγ) and PPARγ coactivator 1 alpha, play vital roles in cell fate determination for fat cells. Beige adipocytes have metabolic therapeutic potential to combat diseases such as obesity, diabetes mellitus, and dyslipidemia, owing to their significant impact on metabolic functions. However, the molecular mechanisms that cause the induction of browning are unclear. Therefore, research using animal models and primary culture is essential to provide an understanding of browning for further application in human metabolic studies. Pigs have physiological similarities to humans; hence, they are valuable models for research on adipose tissue. This study demonstrates the browning potential of pig white adipocytes through primary culture experiments. The results show that upregulation of UCP3 gene expression and fragmentation of lipid droplets into smaller particles occur due to isoproterenol stimulation, which activates beta-adrenergic receptor signaling. Furthermore, PPARγ and PGC-1α were found to activate the UCP3 promoter region, similar to that of UCP1. These findings suggest that pigs undergo metabolic changes that induce browning in white adipocytes, providing a promising approach for metabolic research with potential implications for human health. This study offers valuable insights into the mechanism of adipocyte browning using pig primary culture that can enhance our understanding of human metabolism, leading to cures for commonly occurring diseases.

Infantile hemangioma: the common and enigmatic vascular tumor

Infantile hemangioma (IH) is a benign vascular tumor that occurs in 5% of newborns. The tumor follows a life cycle of rapid proliferation in infancy, followed by slow involution in childhood. This unique life cycle has attracted the interest of basic and clinical scientists alike as a paradigm for vasculogenesis, angiogenesis, and vascular regression. Unanswered questions persist about the genetic and molecular drivers of the proliferating and involuting phases. The beta blocker propranolol usually accelerates regression of problematic IHs, yet its mechanism of action on vascular proliferation and differentiation is unclear. Some IHs fail to respond to beta blockers and regrow after discontinuation. Side effects occur and long-term sequelae of propranolol treatment are unknown. This poses clinical challenges and raises novel questions about the mechanisms of vascular overgrowth in IH.

Circulating Mesenchymal Stromal Cells in Patients with Infantile Hemangioma: Evaluation of Their Functional Capacity and Gene Expression Profile

We previously published that in patients with infantile hemangioma (IH) at the onset (T0) colony forming unit-fibroblasts (CFU-Fs) are present in in vitro cultures from PB. Herein, we characterize these CFU-Fs and investigate their potential role in IH pathogenesis, before and after propranolol therapy. The CFU-F phenotype (by flow cytometry), their differentiation capacity and ability to support angiogenesis (by in vitro cultures) and their gene expression (by RT-PCR) were evaluated. We found that CFU-Fs are actual circulating MSCs (cMSCs). In patients at T0, cMSCs had reduced adipogenic potential, supported the formation of tube-like structures in vitro and showed either inflammatory (IL1β and ESM1) or angiogenic (F3) gene expression higher than that of cMSCs from CTRLs. In patients receiving one-year propranolol therapy, the cMSC differentiation in adipocytes improved, while their support in in vitro tube-like formation was lost; no difference was found between patient and CTRL cMSC gene expressions. In conclusion, in patients with IH at T0 the cMSC reduced adipogenic potential, their support in angiogenic activity and the inflammatory/angiogenic gene expression may fuel the tumor growth. One-year propranolol therapy modifies this picture, suggesting cMSCs as one of the drug targets.

Global research trends of infantile hemangioma: A bibliometric and visualization analysis from 2000 to 2022

Background

Infantile hemangioma (IH) has received global attention, resulting in a significant volume of literature. However, there is a lack of bibliometric analyses specifically focusing on IH publications. This study aims to fill this gap by conducting a comprehensive analysis of IH publications, investigating their characteristics, contribution distribution, and developmental trends. By enhancing our understanding of IH and identifying potential research topics and collaborators, this study will contribute to the advancement of the field.

Methods

A total of 4333 articles and reviews on IH were collected from the Web of Science (WoS) database, spanning the years 2000-2022. The study encompassed a comprehensive analysis of IH publications, evaluating their quantity and quality. Additionally, we profiled publishing groups based on country, institution, author publication records, and collaboration networks. Lastly, we identified and summarized the prominent research topics.

Results

Annual publications on IH have increased over the past 20 years. The United States has the highest number of publications and the highest total number of citations. Pediatric Dermatology was the most influential journal in the IH field. The citation analysis indicated that the articles published by Léauté-Labrèze in 2008 had the highest number of citations. The articles published by North PE in 2000 and Boye E in 2001 laid a certain research foundation for this field. Concerning institutions, most of the cooperative relationships were established in the same country/region. The United States has the largest number of scientific research institutions and IH researchers, leading most of the cross-country collaboration. The University of California, San Francisco, Medical College of Wisconsin, Harvard University, and Shanghai Jiaotong University were the research centers that published the most IH-related research. Frieden IJ, Mulliken JB, and Drolet BA were the top three most influential authors. Frieden IJ, Garzon MC, and Mulliken JB were the top three authors with the most cited frequency. In addition, keywords and keyword co-occurrence networks prompted that the pathological mechanism of IH, clinical analysis, and other vascular anomalies are research hotspots. Analysis of trending topics suggests that research on IH has evolved from treatment-focused studies towards investigations of other vascular diseases and a series of clinical case studies. Currently, clinical case studies receive the most attention in the field.

Conclusions

This comprehensive bibliometric study provides a thorough analysis of post-2000 publications in the field of IH, offering insights into current research trends for the first time. The findings suggest that future investigations will continue to prioritize understanding IH mechanisms, treatment approaches, and treatment evaluation. Furthermore, the exploration of other vascular diseases and the inclusion of clinical case studies are expected to contribute to advancements in IH clinical practice. By identifying potential collaborators, partner institutions, and new research avenues, this study offers valuable guidance for future in-depth research on IH.

The Dual Role of C/EBPδ in Cancer

CCAAT/Enhancer-Binding Protein delta (C/EBPδ) is a transcription factor involved in differentiation and inflammation. While sparsely expressed in adult tissues, aberrant expression of C/EBPδ has been associated with different cancers. Initially, re-expression of C/EBPδ in cell cultures limited tumor cell proliferation, assigning it a tumor suppressor role. However, opposing observations were made in pre-clinical models and patients, suggesting that C/EBPδ not only mediates cell proliferation but dictates a broader spectrum of tumorigenesis-related effects. It is now widely accepted that C/EBPδ contributes to an inflammatory, tumor-promoting microenvironment, aids hypoxia adaption and contributes to the recruitment of blood vessels for improved nutrient supply to tumor cells and facilitated extravasation. This review summarizes the work published on this transcription factor in the field of cancer over the past decade. It points out areas in which a consensus on C/EBPδ's role appears to emerge and seek to explain seemingly contradictory results.

Does Oral Propranolol Improve the Final Outcome of All Involuted Infantile Hemangiomas? A Matched Retrospective Comparative Study

BACKGROUND

Oral propranolol can effectively activate and accelerate infantile hemangioma (IH) involution; however, could the final outcome of oral propranolol treatment for IHs commensurate that of spontaneous involution?

OBJECTIVE

This study aimed to investigate the long-term therapeutic effect of oral propranolol for IHs.

METHODS

We present an individual matching comparative study with (1) oral propranolol therapy for mixed and deep IHs on the lips, nose, and parotid and (2) lesion type- and lesion location-matched untreated IHs as controls. Patients' follow-up photographs were assessed by 3 surgeons blinded of their treatment. Outcome measures were the quantification of the degree of sequelae ranging from 1 to 4 and the age at which IH achieved involution arrest.

RESULTS

Ten groups of oral propranolol and untreated patients with matched lesions were assessed. Average age at which lesions stabilized and reached no change in appearance was 1.7 years old and 6.3 years old for propranolol group and untreated group (t = 5.663, P < 0.001). There was no significant difference in the quantified degree of sequelae for oral propranolol group and untreated group upon follow-up (1.60 vs 1.40, respectively; t = 1.259, P = 0.240).

CONCLUSIONS

Oral propranolol therapy accelerates IH involution but does not have a superior effect than spontaneous involution on the overall outcome of problematic IHs.

Celecoxib induces adipogenic differentiation of hemangioma‑derived mesenchymal stem cells through the PPAR‑γ pathway in vitro and in vivo

Infantile hemangioma (IH) is a benign tumor that produces a permanent scar or a mass of fibro-fatty tissue after involution in 40-80% of cases. Celecoxib is an inhibitor of cyclooxygenase-2 (COX-2), and can inhibit angiogenesis and fibrosis. The present study aimed to clarify whether celecoxib is able to induce tumor regression with minimal side effects. For that purpose, the regulation of celecoxib in the involution of IH was investigated in an IH model. Hemangioma-derived mesenchymal stem cells (Hem-MSCs) were isolated from proliferating specimens, and an IH model was established by injecting these cells into nude mice. Celecoxib was administered in vitro and in vivo. Oil Red O staining and reverse transcription-quantitative-PCR were used to detect the adipogenic differentiation of Hem-MSCs. Histologic analysis and immunohistochemical staining of the tumor xenografts were performed to investigate the pathological evolution of the tumor. The results showed that celecoxib inhibited the proliferation and induced the adipogenic differentiation of Hem-MSCs in vitro. In vivo, adipocytes were only present in the celecoxib group at week 4, while a larger number of fibroblasts and collagenous fibers could be observed in the basic fibroblast growth factor group. Therefore, celecoxib may be a potential agent used for IH treatment by inducing adipogenesis and inhibiting fibroblast formation.

Hemangioma Endothelial Cells and Hemangioma Stem Cells in Infantile Hemangioma

BACKGROUND

Hemangioma is one of the most common benign tumors in infants and young children. The 2 most important cells in the course of infantile hemangioma (IH) are hemangioma stem cells (HemSCs) and hemangioma endothelial cells (HemECs). Infantile hemangioma is characterized by massive proliferation of HemECs, but current studies indicate that HemSCs play an important role in pathogenesis of IH.

OBJECTIVE

This review aimed to identify molecules that influence HemSC differentiation and HemEC proliferation and apoptosis to help clarify the pathogenesis of IH and provide novel drug targets for the treatment of IH.

METHODS

Relevant basic science studies related to IH were identified by searching Google Scholar, Embase, PubMed, MEDLINE, and peer-reviewed journal articles.

RESULT

Hemangioma stem cells can differentiate into HemECs, pericytes, and adipocytes. In the proliferating phase of IH, HemSCs mainly differentiate into HemECs and pericytes to promote angiogenesis. In the regressive phase, they mainly differentiate into adipocytes. Therefore, increasing the proportion of HemSCs differentiating into adipocytes, inhibiting the proliferation of HemECs, and promoting the apoptosis of HemECs can facilitate the regression of IH.

Propranolol Therapy in Infantile Hemangioma: It Is Not Just About the Beta

BACKGROUND

Propranolol, a nonselective β-adrenergic receptor antagonist, is approved by the U.S. Food and Drug Administration to treat problematic infantile hemangiomas, but a subset of patients experience treatment complications. Parents wary of long-term use and side effects consult plastic surgeons on surgical options or as a second opinion. Understanding the mechanism(s) of action of propranolol will allow plastic surgeons to better inform parents.

METHODS

A systemic literature search was performed to query published translational and basic science studies on propranolol effects on infantile hemangiomas and cells derived from these lesions.

RESULTS

In experimental studies, propranolol was antiproliferative and cytotoxic against hemangioma endothelial and stem cells and affected infantile hemangioma perivascular cell contractility. Propranolol inhibited migration, network formation, vascular endothelial growth factor A production, and vascular endothelial growth factor receptor 2 activation and down-regulated PI3K/AKT and mitogen-activated protein kinase signaling in hemangioma endothelial cells, but it increased ERK1/2 activity in hemangioma stem cells. At effective clinical doses, measured propranolol plasma concentration is 100 times higher than necessary for complete β-adrenergic receptor blockade, yet was 10 to 100 times less than required to induce hemangioma stem cell death.

CONCLUSIONS

Propranolol targets multiple cell types in infantile hemangiomas by means of β-adrenergic receptor-dependent and -independent mechanisms. Plasma concentration played a significant role. At clinically relevant doses, incomplete infantile hemangioma suppression may explain the rebound phenomenon and worsening ulceration, and propranolol off target effects may lead to commonly reported adverse effects, such as sleep and gastrointestinal disturbances. Propranolol limitations and complications underscore the importance of surgical treatment options in cases of rebound and severe adverse effects. Surgical intervention remains an important treatment choice when parents are hesitant to use propranolol.

Propranolol vs. steroids in the treatment of infantile hemangiomas: A meta-analysis

Infantile hemangioma (IH) is a common disease, and drug therapy is the most common treatment method. Clinically, steroids have long been used as first-line drugs, but in recent years, some doctors have begun to use propranolol to treat infantile hemangiomas (IHs). The present study performed a meta-analysis to evaluate the clinical effects of propranolol in comparison with steroids in the treatment of infantile hemangiomas. A detailed review of the literature on PubMed, Cochrane Library, Embase and Web of Science was performed prior to March 31, 2020. All literatures were compared with the clinical effects of propranolol and steroids in the treatment of infantile hemangiomas. A total of two researchers independently screened the literature according to the selection criteria, extracted data and assessed the risk of bias for the included studies. Review Manager 5.3 was used to meta-analyze all the included studies. According to the selection criteria, nine articles were included in the present study. The meta-analysis revealed that the effective rate of propranolol was greater than that of steroids in treating infantile hemangiomas [odds ratio (OR), 3.96, 95% confidence interval (CI), 2.47-6.37; P<0.00001]. Additionally, propranolol had fewer complications than steroids (OR, 0.21; 95% CI, 0.12-0.36; P<0.00001). The recurrence rate of the two groups was not statistically different (OR, 1.83; 95% CI, 0.59-5.70; P=0.3) and the surgical resection rate of propranolol was lower than steroids (OR, 0.19; 95% CI, 0.08-0.46; P=0.0002). The present study demonstrated that propranolol is more effective than steroids for the treatment of IHs, and provides a theoretical basis for the clinical use of propranolol as an alternative to steroids.

Propranolol for infantile hemangioma: Evaluating efficacy and predictors of response and rebound growth

Propranolol emerged as the first-line therapy for infantile hemangioma (IH). Determinants of interindividual variation in drug response and predictors of rebound growth after drug discontinuation are yet to be firmly established. We aimed to evaluate the outcomes of a relatively large cohort of patients with IH treated by propranolol and to determine predictors of (a) an excellent response to treatment (≥90 improvement) and (b) of rebound growth after drug cessation. A retrospective cohort study was conducted to follow all patients with IH receiving systemic propranolol in a referral center-based specialized clinic. Multivariate logistic regression analysis was performed to identify predictors of excellent response and rebound growth. The study included 206 patients who completed oral propranolol treatment. The mean (SD) age in which the drug was initiated was 4.8 (3.1) months. The average improvement rate was estimated at 85.5 (13.8)%. Initiation of propranolol at the age of 0 to 3 (adjusted odds ratio [OR], 3.43; 95% confidence interval [CI], 1.25-9.40; P = .016) and 3 to 6 (adjusted OR, 3.71; 95% CI, 1.50-9.19; P = .005) months was associated with an increased likelihood of excellent response. Twenty-four (11.7%) patients developed rebound growth following cessation of propranolol. No significant predictors of rebound were identified in the multivariate analysis. Eleven (5.3%) patients experienced mild adverse events, which necessitated drug discontinuation in only two (1.0%) patients. Propranolol is highly effective and safe based on the real-life experience of a referral center for IH. The current study supports early initiation of propranolol.

The use of Hediste diversicolor in the study of emerging contaminants

The contamination of aquatic environments has been the focus of research to understand effects on ecosystems and its species. Benthic organisms are considered potential targets since sediments act as sources and sinks for environmental contaminants. This review presents information on the effects of three types of emerging contaminants: pharmaceuticals (tested concentrations between 0.1 ng/L - 250 mg/L and 0.01 ng/g - 2.5 μg/g), metal-based nanoparticles (<100 nm) (tested concentrations between 10 μg/L - 1 mg/L and 5 - 140 μg/g) and micro(nano)plastics (tested concentrations between 5 μg/L - 50 mg/L and 10 - 50 mg/kg), on the polychaete Hediste diversicolor, a key species in estuarine/coastal ecosystems. Data shows that these contaminants promote alterations in burrowing activity (lowest concentration inducing effects: 10 ng/L), neurotransmission and damage related parameters (lowest concentration inducing effects: 100 ng/L). The characteristics of this polychaete, such as regenerative capacity, make the use of this species in biomedical studies involving environmental contaminants valuable.

Recurrent Epithelioid Hemangioma of the Bony Pelvis Responding to Propranolol

Epithelioid hemangioma is an uncommon benign vascular neoplasm which can arise in bone. Resection is generally curative, but occasionally lesions recur and recurrence after surgery can be morbid and destructive. Recent case reports have described the effective use of oral propranolol to control recurrent epithelioid hemangioma of the orbit. We report the case of a 26 year old man with recurrent aggressive osseous epithelioid hemangioma in the pelvis of which has been controlled for over a year with outpatient propranolol monotherapy.

Insulin-like growth factor 2 promotes the adipogenesis of hemangioma-derived stem cells

Infantile hemangioma (IH), which is the most common tumor in infants, is characterized by rapid proliferation followed by spontaneous regression into fibro-fatty tissue in childhood. However, its specific mechanism has not been clarified. Our previous studies showed that insulin-like growth factor 2 (IGF-2) is increased in the proliferative phase of IH, which is deemed to form from hemangioma-derived stem cells (HemSC). However, it remains unclear whether IGF-2 can promote the adipogenic differentiation of HemSCs and the signaling mechanisms involved require further elucidation. In the present study, CCK-8 assay was used to detect the effect of different concentrations of IGF-2 on the proliferation of HemSCs. Immunohistochemistry was applied to observe the expression of IGF-2 and its receptors in cells. Oil red o-staining of adipogenesis was conducted after cells recevied no treatment or were induced with IGF-2 or IGF-2 plus OSI-906 for 10 days. Cells were cultured in EGM-2/FBS-10% alone or containing IGF-2, IGF-2 plus OSI-906 or IGF-2 plus LY294002 and the protein expression of C/EBPα, C/EBPβ, PPARγ, adiponectin, p-AKT and total AKT was determined using western blot analysis. In another experiment, cells were treated with 25, 50 or 100 μM propranolol, or vehicle. C/EBPα, C/EBPβ, PPARγ and IGF-2 were analyzed using western blot analysis or reverse transcription-quantitative polymerase chain reaction. Results indicated that IGF-2 significantly promoted the cell proliferation and lipid accumulation of HemSCs. The expression of phosphorylated AKT (p-AKT), C/EBPα, C/EBPβ, PPARγ and adiponectin was increased in IGF-2-treated HemSCs culture, whereas these changes were repressed by the inhibition of either the IGF-1 receptor (IGF-1R) or phosphoinositide 3-kinase (PI3K). Our previous research showed that propranolol accelerated adipogenesis in HemSCs and induced the upregulation of IGF-2. The results of the present study indicate that IGF-2 is able to accelerate adipogenesis, and the propranolol-induced promotion of dysregulated adipogenesis may be mediated by the IGF-2 via IGF-1R and PI3K pathways.

Modulation of LIN28B/Let-7 Signaling by Propranolol Contributes to Infantile Hemangioma Involution

OBJECTIVE

Infantile hemangiomas (IHs) are the most common benign vascular neoplasms of infancy, characterized by a rapid growth phase followed by a spontaneous involution, or triggered by propranolol treatment by poorly understood mechanisms. LIN28/let-7 axis plays a central role in the regulation of stem cell self-renewal and tumorigenesis. However, the role of LIN28B/let-7 signaling in IH pathogenesis has not yet been elucidated.

APPROACH AND RESULTS

LIN28B is highly expressed in proliferative IH and is less expressed in involuted and in propranolol-treated IH samples as measured by immunofluorescence staining and quantitative RT-PCR. Small RNA sequencing analysis of IH samples revealed a decrease in microRNAs that target LIN28B, including let-7, and an increase in microRNAs in the mir-498(46) cistron. Overexpression of LIN28B in HEK293 cells induced the expression of miR-516b in the mir-498(46) cistron. Propranolol treatment of induced pluripotent stem cells, which express mir-498(46) endogenously, reduced the expression of both LIN28B and mir-498(46) and increased the expression of let-7. Furthermore, propranolol treatment reduced the proliferation of induced pluripotent stem cells and induced epithelial-mesenchymal transition.

CONCLUSIONS

This work uncovers the role of the LIN28B/let-7 switch in IH pathogenesis and provides a novel mechanism by which propranolol induces IH involution. Furthermore, it provides therapeutic implications for cancers in which the LIN28/let-7 pathway is imbalanced.

Downregulation of miR-382 by propranolol inhibits the progression of infantile hemangioma via the PTEN-mediated AKT/mTOR pathway

Approximately 10% of infantile hemangiomas (IHs) are the most common vascular tumors affecting children and are characterized by rapid growth, and can have destructive, disfiguring and even life-threatening consequences. Currently, propranolol is considered to be a safe and effective treatment option for problematic proliferating IHs. Recent studies have also revealed that microRNAs (miRNAs or miRs) play important roles in the regulation of angiogenesis. In this study, XPTS‑1 cells were used as a hemangioma-derived endothelial cell line constructed in our laboratory. Through a series of experiments, we discovered that miR‑382 is a novel miRNA associated with IHs, which was overexpressed in XPTS‑1 cells and was conversely downregulated by treatment with propranolol. In addition, we found that miR‑382 contributes to the progression of IHs. Our results revealed that propranolol inhibited XPTS‑1 cell migration and proliferation, and promoted apoptosis, and these effects were reversed by the restoration of miR‑382 expression by transfection of the cells with an miR‑382 overexpression vector. Further experiments revealed that the above-mentioned effects were associated with the phosphatase and tensin homolog (PTEN)-mediated AKT/mammalian target of rapamycin (mTOR) signaling pathway. The expression of PTEN was upregulated, while that of p-AKT, p-mTOR and p-p70S6K was downregulated by propranolol; these effects were partly reversed by the overexpression of miR‑382. On the whole, our study identified that the downregulation of miR‑382 by propranolol inhibits the progression of IHs via the PTEN-mediated AKT/mTOR pathway.

Rebound Growth of Infantile Hemangiomas After Propranolol Therapy

BACKGROUND AND OBJECTIVES

Propranolol is first-line therapy for problematic infantile hemangiomas (IHs). Rebound growth after propranolol discontinuation is noted in 19% to 25% of patients. Predictive factors for rebound are not completely understood and may alter the management approach. The goal of the study was to describe a cohort of patients with IHs treated with propranolol and to identify predictors for rebound growth.

METHODS

A multicenter retrospective cohort study was conducted in patients with IHs treated with propranolol. Patient demographic characteristics, IH characteristics, and specifics of propranolol therapy were obtained. Episodes of rebound growth were recorded. Patients' responses to propranolol were evaluated through a visual analog scale.

RESULTS

A total of 997 patients were enrolled. The incidence of rebound growth was 231 of 912 patients (25.3%). Mean age at initial rebound was 17.1 months. The odds of rebound among those who discontinued therapy at <9 months was 2.4 (odds ratio [OR]: 2.4; 95% confidence interval [CI]: 1.3 to 4.5; P = .004) compared with those who discontinued therapy between 12 to 15 months of life. Female gender, location on head and neck, segmental pattern, and deep or mixed skin involvement were associated with rebound on univariate analysis. With multivariate analysis, only deep IHs (OR: 3.3; 95% CI: 1.9 to 6.0; P < .001) and female gender (OR: 1.7; 95% CI: 1.1 to 2.6; P = .03) were associated. Of those with rebound growth, 83% required therapeutic modification including 62% of patients with modifications in their propranolol therapy.

CONCLUSIONS

Rebound growth occurred in 25% of patients, requiring modification of systemic therapy in 15%. Predictive factors for rebound growth included age of discontinuation, deep IH component, and female gender. Patients with these predictive factors may require a prolonged course of therapy.

Propranolol Targets Hemangioma Stem Cells via cAMP and Mitogen-Activated Protein Kinase Regulation

Infantile hemangiomas (IHs) are the most common vascular tumor and arise from a hemangioma stem cell (HemSC). Propranolol has proved efficacious against IHs. A selective β2-adrenergic receptor (AR) antagonist mirrored propranolol’s effects on HemSCs. These results show that propranolol acts on HemSCs in IH to suppress proliferation and promote apoptosis in a dose-dependent fashion via β2AR perturbation.

Infantile hemangiomas (IHs) are the most common vascular tumor and arise from a hemangioma stem cell (HemSC). Propranolol has proved efficacious for problematic IHs. Propranolol is a nonselective β-adrenergic receptor (βAR) antagonist that can lower cAMP levels and activate the mitogen-activated protein kinase (MAPK) pathway downstream of βARs. We found that HemSCs express β1AR and β2AR in proliferating IHs and determined the role of these βARs and the downstream pathways in mediating propranolol’s effects. In isolated HemSCs, propranolol suppressed cAMP levels and activated extracellular signal-regulated kinase (ERK)1/2 in a dose-dependent fashion. Propranolol, used at doses of <10⁻⁴ M, reduced cAMP levels and decreased HemSC proliferation and viability. Propranolol at ≥10⁻⁵ M reduced cAMP levels and activated ERK1/2, and this correlated with HemSC apoptosis and cytotoxicity at ≥10⁻⁴ M. Stimulation with a βAR agonist, isoprenaline, promoted HemSC proliferation and rescued the antiproliferative effects of propranolol, suggesting that propranolol inhibits βAR signaling in HemSCs. Treatment with a cAMP analog or a MAPK inhibitor partially rescued the HemSC cell viability suppressed by propranolol. A selective β2AR antagonist mirrored propranolol’s effects on HemSCs in a dose-dependent fashion, and a selective β1AR antagonist had no effect, supporting a role for β2AR signaling in IH pathobiology. In a mouse model of IH, propranolol reduced the vessel caliber and blood flow assessed by ultrasound Doppler and increased activation of ERK1/2 in IH cells. We have thus demonstrated that propranolol acts on HemSCs in IH to suppress proliferation and promote apoptosis in a dose-dependent fashion via β2AR perturbation, resulting in reduced cAMP and MAPK activation.

Significance

The present study investigated the action of propranolol in infantile hemangiomas (IHs). IHs are the most common vascular tumor in children and have been proposed to arise from a hemangioma stem cell (HemSC). Propranolol, a nonselective β-adrenergic receptor (βAR) antagonist, has proven efficacy; however, understanding of its mechanism of action on HemSCs is limited. The presented data demonstrate that propranolol, via βAR perturbation, dose dependently suppresses cAMP levels and activated extracellular signal-regulated kinase 1/2. Furthermore, propranolol acts via perturbation of β2AR, and not β1AR, although both receptors are expressed in HemSCs. These results provide important insight into propranolol’s action in IHs and can be used to guide the development of more targeted therapy.

Diagnosis and Management of Infantile Hemangioma

Infantile hemangiomas (IHs) are the most common tumors of childhood. Unlike other tumors, they have the unique ability to involute after proliferation, often leading primary care providers to assume they will resolve without intervention or consequence. Unfortunately, a subset of IHs rapidly develop complications, resulting in pain, functional impairment, or permanent disfigurement. As a result, the primary clinician has the task of determining which lesions require early consultation with a specialist. Although several recent reviews have been published, this clinical report is the first based on input from individuals representing the many specialties involved in the treatment of IH. Its purpose is to update the pediatric community regarding recent discoveries in IH pathogenesis, treatment, and clinical associations and to provide a basis for clinical decision-making in the management of IH.

Propranolol reduces viability and induces apoptosis in hemangioblastoma cells from von Hippel-Lindau patients

BACKGROUND

Von Hippel-Lindau (VHL) disease is a rare oncological disease with an incidence of 1:36,000, and is characterized by the growth of different types of tumors: hemangioblastomas in the central nervous system (CNS) and retina, renal carcinoma, pheochromocytomas, pancreatic serous cystadenoma, and endolymphatic sac tumors. These tumors do not express VHL protein (pVHL). pVHL ubiquitinates hypoxia inducible factor (HIF) protein for degradation by the proteasome; in the absence of VHL, HIF translocates to the nucleus to activate the expression of its target genes. Targeting VHL-derived tumors with drugs that have reduced side effects is urgent to avoid repeat CNS surgeries. Recent reports have shown that propranolol, a β-blocker used for the treatment of hypertension and other cardiac and neurological diseases, is the best option for infantile hemangioma (IH). Propranolol could be an efficient treatment to control hemangioblastoma growth in VHL disease because of its antiangiogenic effects demonstrated in IH and the hypothetical impact on HIF levels.

METHODS

HeLa 9X (HRE) hypoxia responsive element cell line and primary hemangioblastoma-derived cells were subjected to propranolol treatment and cell viability and apoptosis were evaluated. HIF1-α and Hif-2α expression after propranolol treatment was analyzed by western blotting. Quantitative PCR was performed to study the mRNA expression of HIF target genes. Vascular endothelial growth factor (VEGF) was measured in culture supernatants by immunoassay.

RESULTS

Propranolol downregulated HIF-dependent transcription in HeLa 9XHRE cells. Under hypoxic conditions, propranolol decreased the expression of HIF target genes in hemangioblastoma cells, which stopped proliferating and died following long-term treatment. These results suggests that propranolol treatment promoted reduced HIF protein expression and corresponding downregulation of HIF target genes, and inhibited cell proliferation in parallel with induction of cell death by apoptosis.

CONCLUSIONS

Our results suggest that propranolol could reduce the growth of HIF-dependent tumors and may thus be a promising treatment to delay surgery in VHL patients.

Beta-blockers for childhood vascular tumors

PURPOSE OF REVIEW

Since 2008, beta-blockers have become first-line treatment for infantile hemangiomas, the most common tumor of infancy. Their role is also being explored in the treatment of other childhood vascular tumors.

RECENT FINDINGS

Recent research has demonstrated that propranolol is a more effective and safer treatment for infantile hemangiomas than previous therapeutic options. It is most effective when initiated during the tumor's proliferative phase. Other oral beta-blockers such as atenolol and nadolol are less studied, but may offer similar efficacy. Topical beta-blockers such as timolol appear to be effective in treating small, superficial infantile hemangiomas. Beta-blockers have shown variable results for the treatment of other vascular tumors of childhood, such as pyogenic granulomas, kaposiform hemangioendotheliomas, and tufted angiomas.

SUMMARY

Propranolol has revolutionized the treatment of infantile hemangiomas, and other beta-blockers provide promising alternatives. Unanswered questions remain about the optimal choice of agent, delivery mechanism, dosage, need for pretreatment evaluation or ongoing monitoring, and duration of therapy. The role of beta-blockers in treating other types of vascular tumors requires further study.