The expression of renin-angiotensin-aldosterone axis components in infantile hemangioma tissue and the impact of propranolol treatment

Infantile Hemangiomas: An Update on Pathogenesis and Treatment

Infantile hemangiomas are the most common benign vascular tumors in infancy. This review includes an update on the current knowledge on pathogenesis, a discussion on indications for treatment, and a review of the mechanisms underlying the different treatment methods. Although most infantile hemangiomas require only active observation because of their natural course, which results in involution, about 10% present with complications that require immediate treatment. The basic treatment includes systemic and topical options. In cases of insufficient response or rebound growth, other forms of treatment should be considered. In some cases, combined therapy might be initiated.

Highlighting the Potential for Chronic Stress to Minimize Therapeutic Responses to Radiotherapy through Increased Immunosuppression and Radiation Resistance

Ionizing radiation has been used in the treatment of cancer for more than 100 years. While often very effective, there is still a great effort in place to improve the efficacy of radiation therapy for controlling the progression and recurrence of tumors. Recent research has revealed the close interaction between nerves and tumor progression, especially nerves of the autonomic nervous system that are activated by a variety of stressful stimuli including anxiety, pain, sleep loss or depression, each of which is likely to be increased in cancer patients. A growing literature now points to a negative effect of chronic stressful stimuli in tumor progression. In this review article, we present data on the potential for adrenergic stress to influence the efficacy of radiation and in particular, its potential to influence the anti-tumor immune response, and the frequency of an "abscopal effect" or the shrinkage of tumors which are outside an irradiated field. We conclude that chronic stress can be a major impediment to more effective radiation therapy through mechanisms involving immunosuppression and increased resistance to radiation-induced tumor cell death. Overall, these data highlight the potential value of stress reduction strategies to improve the outcome of radiation therapy. At the same time, objective biomarkers that can accurately and objectively reflect the degree of stress in patients over prolonged periods of time, and whether it is influencing immunosuppression and radiation resistance, are also critically needed.

NOTCH pathway activation in infantile hemangiomas

OBJECTIVE

The objective of this study was to characterize the role of NOTCH signaling cascade activation in the angiogenic drive of infantile hemangioma (IH) tissue.

METHODS

Both IH tissue and normal skin were collected from 55 surgical patients. Of these, 14 were proliferating hemangiomas, 14 were stationary, 14 were involuted, and 13 had been treated with propranolol. Protein and RNA were extracted from all tissues and subjected to Western blotting and reverse transcription-polymerase chain reaction, respectively, for components of the NOTCH signaling pathway.

RESULTS

Compared with normal skin from the same patients, proliferating IHs contained higher levels of messenger RNA and protein for the majority of NOTCH receptors and ligands as well as the downstream coactivator MAML1. Expression of NOTCH receptor ligand messenger RNA and protein was significantly lower in involuting and propranolol-treated IHs.

CONCLUSIONS

Perturbations in NOTCH signaling follow the natural course and treatment outcome of IHs, suggesting a critical role in their pathogenesis.

Efficacy and adverse effects of oral propranolol in infantile hemangioma: a meta-analysis of comparative studies

BACKGROUND

A number of clinical trials evaluated the efficacy and adverse effects of oral propranolol in the treatment of infantile hemangioma (IH), but the treatment has not yet been standardized. This meta-analysis aims to reevaluate the efficacy and adverse effects of oral propranolol in comparative studies and to provide a reliable basis for clinical administration in the therapy for IH.

METHODS

Data were obtained from PubMed, Embase, Cochrane Library, Web of Science, China National Knowledge Infrastructure and Wanfang database, from inception to December 1st, 2018. The pooled risk ratios (RR) with 95% confidence intervals (95% CI) were calculated and used to evaluate the effect size. The meta-analysis was performed using the random-effects model due to heterogeneity between the studies. The Cochrane Collaboration 6 aspects of bias, methodological index for non-randomized studies and the Newcastle-Ottawa Scale were used to assess the risk for bias. Sensitivity analysis, publication bias and subgroup analysis were performed.

RESULTS

Eighteen unique studies involving 2701 unique children were included in the analysis. The response rate was reported in 18 trials, which compared oral propranolol with other treatments. The heterogeneity was statistically significant (P < 0.00001, I² = 95%). The difference in the response rate was statistically significant (RR = 1.40, 95% CI 1.13-1.75) while compared with the controls. However, no significant difference in the adverse events rate (RR = 0.78, 95% CI 0.45-1.34) and relapse rate (RR = 1.45, 95% CI 0.66-3.16) were found. Otherwise, the subgroup analysis indicated that the RR was 1.64 (95% CI 0.24-11.36) for low-dose propranolol (1 mg/kg/day), 1.42 (95% CI 1.12-1.80) for medium dose (2 mg/kg/day) and 1.46 (95% CI 1.17-1.82) for high dose (3 mg/kg/day), but the high dose had higher adverse events rate than medium dose, with 3.60% and 86.22%, respectively. The effectiveness of propranolol therapy among cases of treatment duration less than 6 months (RR = 1.24, 95% CI 1.05-1.47) was inferior to that of treatment duration greater than or equal to 6 months (RR = 1.46, 95% CI 1.11-1.92).

CONCLUSIONS

This meta-analysis reveals that oral propranolol is superior to other treatments in improving response rate of IH and can be used as the first-line therapy for IH children. A dosage of 2 mg/kg/day propranolol orally may be a good choice for IH. However, further studies are essential.

Expression of (pro)renin receptor and its effect on endothelial cell proliferation in infantile hemangioma

BACKGROUND

Propranolol is the preferred treatment for problematic proliferating infantile hemangioma (IH) by targeting the renin-angiotensin system (RAS) expressed by IH endothelium. (Pro)renin receptor (PRR) is a major component of the RAS associated with the canonical wnt signaling pathway. We proposed that activation of PRR by renin causes proliferation of IH.

METHODS

The expression of PRR in IH tissue samples was investigated using immunohistochemical (IHC) staining and NanoString analysis. NanoString analysis was also used to confirm transcriptional expression of PRR in CD34-sorted proliferating IH-derived primary cell lines. MTT assay was utilized to determine the effect of exogenous renin on the number of viable IH cells. RT-qPCR was used to determine the effect of renin on the stem cell gene expression.

RESULTS

NanoString analysis and IHC staining confirmed transcriptional and translational expression of PRR, which was localized to the non-endothelial and the endothelial IH cell populations. MTT assay demonstrated an increased number of viable IH cells by administration of renin and the effect was negated by the wnt receptor blocker dickkopf-1.

CONCLUSION

Our results present a model for renin-induced increased proliferation of IH cells through PRR acting via the wnt signaling pathway, which may account for accumulation of cells in IH during the proliferative phase of the tumor.

Infantile hemangiomas: what have we learned from propranolol?

PURPOSE OF REVIEW

Infantile hemangiomas are the most common vascular tumor of infancy. Treatment of infantile hemangiomas was revolutionized when propranolol, a nonselective β-blocker, was reported to be effective therapy. In this review, we highlight the lessons learned using propranolol to treat infantile hemangiomas. We also describe the ongoing effort to understand the mechanism of action of propranolol.

RECENT FINDINGS

Although the pathogenesis of infantile hemangiomas is not fully understood, maternal hypoxic stress and embolization of placental tissue are suggested to be critical components in their development. The mechanism of action of propranolol remains unclear, however various molecular mechanisms are detailed in this review. Propranolol treatment remains a well tolerated therapy, with low risk of adverse events or long-term neurocognitive effects. Dosing recommendations and optimal treatment duration vary among studies, and should be altered in patients with certain medical conditions such as Posterior fossa anomalies, Hemangioma, Arterial lesions, Cardiac abnormalities/coarctation of the aorta, Eye anomalies (PHACE) syndrome.

SUMMARY

Propranolol is a well tolerated and effective treatment for infantile hemangiomas. The efficacy of propranolol for infantile hemangiomas is clear, however questions pertaining to mechanism of action, pretreatment risk stratification, and optimal dosing remain unanswered. The guidelines for managing infantile hemangiomas with propranolol will continue to adapt as research catches up to clinical experience.

Phosphorylated Forms of STAT1, STAT3 and STAT5 Are Expressed in Proliferating but Not Involuted Infantile Hemangioma

We have recently demonstrated the expression of embryonic stem cell markers on the endothelium of infantile hemangioma, a functional hemogenic endothelium with the capacity for primitive erythropoiesis in vitro. Despite recent work characterizing stem cells within proliferating infantile hemangioma, the expression of STAT proteins, well documented for their roles in stem cell signaling, has not been investigated. 3,3-Diaminobenzidine and immunofluorescence immunohistochemical staining revealed expression of pSTAT1, pSTAT3 and pSTAT5 in proliferating infantile hemangioma samples with the strongest expression of pSTAT3. There was reduced expression of these pSTAT proteins in the involuted infantile hemangioma samples. Western blotting confirmed the identification of all these three proteins in proliferating infantile hemangioma. It is therefore not surprising that the phosphorylated/activated forms of these proteins are relatively abundantly expressed in proliferating, in comparison to involuted infantile hemangioma samples. We speculate that the reduced STAT activation, as infantile hemangioma involutes, is a reflection of the depletion of the abundant stem cells within proliferating infantile hemangioma, as the lesion involutes.