Non–beta blocker enantiomers of propranolol and atenolol inhibit vasculogenesis in infantile hemangioma

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Abstract

Propranolol and atenolol, current therapies for problematic infantile hemangioma (IH), are composed of R(+) and S(–) enantiomers: the R(+) enantiomer is largely devoid of beta blocker activity. We investigated the effect of R(+) enantiomers of propranolol and atenolol on the formation of IH-like blood vessels from hemangioma stem cells (HemSCs) in a murine xenograft model. Both R(+) enantiomers inhibited HemSC vessel formation in vivo. In vitro, similar to R(+) propranolol, both atenolol and its R(+) enantiomer inhibited HemSC to endothelial cell differentiation. As our previous work implicated the transcription factor sex-determining region Y (SRY) box transcription factor 18 (SOX18) in propranolol-mediated inhibition of HemSC to endothelial differentiation, we tested in parallel a known SOX18 small-molecule inhibitor (Sm4) and show that this compound inhibited HemSC vessel formation in vivo with efficacy similar to that seen with the R(+) enantiomers. We next examined how R(+) propranolol alters SOX18 transcriptional activity. Using a suite of biochemical, biophysical, and quantitative molecular imaging assays, we show that R(+) propranolol directly interfered with SOX18 target gene trans-activation, disrupted SOX18-chromatin binding dynamics, and reduced SOX18 dimer formation. We propose that the R(+) enantiomers of widely used beta blockers could be repurposed to increase the efficiency of current IH treatment and lower adverse associated side effects.

Authors

Caroline T. Seebauer, Matthew S. Graus, Lan Huang, Alex McCann, Jill Wylie-Sears, Frank Fontaine, Tara Karnezis, David Zurakowski, Steven J. Staffa, Frédéric Meunier, John B. Mulliken, Joyce Bischoff, Mathias Francois