sirolimus and Hemangioma--Capillary

Infantile hemangiomas are the most common benign vascular tumors in childhood. Propranolol is the first-line treatment for infantile hemangiomas, but failures may occur. Sirolimus, an mTOR inhibitor, is a promising drug for the treatment of vascular malformations and vascular tumors. We present the case of a child with multiple infantile hemangiomasthat was successfully treated with sirolimus and propranolol after failure of combined propranolol and prednisolone treatment.

Topics: Adrenergic beta-Antagonists; Child; Hemangioma; Hemangioma, Capillary; Humans; Infant; Prednisolone; Propranolol; Sirolimus; Treatment Outcome

FABP4 is widely expressed in both normal and pathologic tissues. It promotes cell proliferation, survival and migration of endothelial cells, and therefore, angiogenesis. However, the role of FABP4 in hemangioma or hemangioma endothelial cells (HemECs) has not been explored. In this study, we investigated whether FABP4 directly regulates the proliferation of HemECs. The expression of cell cycle checkpoint genes was analyzed with the microarray data of human dermal microvascular endothelial cells (HDVECs) and infantile hemangioma endothelial cells. Real-time RT-PCR and western blotting were used to examine the expression of FABP4 in HemECs. Next, the FABP4 expression was inhibited in HemECs using siRNA or rapamycin and upregulated using retroviral transduction of HemECs to assess its influence on proliferation of HemECs. The microarray data showed that cell cycle checkpoint genes were upregulated in HemECs. Moreover, HemECs showed significantly higher proliferation rates than HDVECs. The expression of FABP4 and mTOR was increased in the HemECs. While FABP4 knockdown reduced the BrdU incorporation and cell number of HemECs as expected, cell proliferation was accelerated by FABP4 over-expression. Moreover, rapamycin (10nM) inhibited mTOR-FABP4 signaling and HemEC proliferation. Taken together, these results indicated that mTOR signaling pathway-activated FABP4 directly regulates the proliferation of endothelial cells in hemangioma. Rapamycin and inhibitors of FABP4 have therapeutic potential for treating infantile hemangiomas.

Topics: Antineoplastic Agents; Cell Cycle Proteins; Cell Proliferation; Endothelial Cells; Fatty Acid-Binding Proteins; Hemangioma, Capillary; Humans; Neoplastic Syndromes, Hereditary; Protein Kinase Inhibitors; RNA Interference; Signal Transduction; Sirolimus; Time Factors; TOR Serine-Threonine Kinases; Transfection; Tumor Cells, Cultured

Vascular tumors are endothelial cell neoplasms whose cellular and molecular mechanisms, leading to tumor formation, are poorly understood, and current therapies have limited efficacy with significant side effects. We have investigated mechanistic (mammalian) target of rapamycin (mTOR) signaling in benign and malignant vascular tumors, and the effects of mTOR kinase inhibitor as a potential therapy for these lesions. Human vascular tumors (infantile hemangioma and angiosarcoma) were analyzed by immunohistochemical stains and western blot for the phosphorylation of p70 S6-kinase (S6K) and S6 ribosomal protein (S6), which are activated downstream of mTOR complex-1 (mTORC1). To assess the function of S6K, tumor cells with genetic knockdown of S6K were analyzed for cell proliferation and migration. The effects of topical rapamycin, an mTOR inhibitor, on mTORC1 and mTOR complex-2 (mTORC2) activities, as well as on tumor growth and migration, were determined. Vascular tumors showed increased activation of S6K and S6. Genetic knockdown of S6K resulted in reduced tumor cell proliferation and migration. Rapamycin fully inhibited mTORC1 and partially inhibited mTORC2 activities, including the phosphorylation of Akt (serine 473) and PKCα, in vascular tumor cells. Rapamycin significantly reduced vascular tumor growth in vitro and in vivo. As a potential localized therapy for cutaneous vascular tumors, topically applied rapamycin effectively reduced tumor growth with limited systemic drug absorption. These findings reveal the importance of mTOR signaling pathways in benign and malignant vascular tumors. The mTOR pathway is an important therapeutic target in vascular tumors, and topical mTOR inhibitors may provide an alternative and well-tolerated therapy for the treatment of cutaneous vascular lesions.

Topics: Administration, Topical; Adolescent; Adult; Aged; Animals; Antibiotics, Antineoplastic; Cell Line, Tumor; Child; Female; Hemangioma, Capillary; Hemangiosarcoma; Humans; Infant; Male; Mechanistic Target of Rapamycin Complex 1; Mechanistic Target of Rapamycin Complex 2; Mice; Mice, Nude; Multiprotein Complexes; Neoplasm Proteins; Neoplastic Syndromes, Hereditary; Protein Kinase Inhibitors; Ribosomal Protein S6 Kinases, 70-kDa; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases; Tumor Cells, Cultured; Xenograft Model Antitumor Assays