Inhibition of human melanoma growth by a non-cardioselective β-blocker

Recently, retrospective studies provided conflicting results on the benefit of β-adrenoceptor-blockers (β-blockers) on melanoma progression. Most of these studies did not define the β-blocker used, making it difficult to understand the source of discrepancies between results. Therefore, we investigated the effect of non-cardioselective and cardioselective β-blockers on melanoma progression at the cellular, molecular, and tumor levels. Here we show that the non-cardioselective β-blocker propranolol hydrochloride (propranolol) inhibits proliferation and induces apoptosis in primary cell cultures derived from a primary and a metastasis of human melanoma and in melanoma cell lines. In contrast, the cardioselective β-blocker metoprolol tartrate hardly affects melanoma cell survival or proliferation. We further highlight that a daily treatment with propranolol slows down tumor development in immunodeficient mice transplanted with human melanoma cells. RNA microarrays, quantitative PCR, and histochemistry analyses showed that propranolol regulates the expression of different genes involved in tumor angiogenesis, cell death, or proliferation. Thus, our results suggest that non-cardioselective β-blockers affect melanoma progression, and bring first clues about the pathways involved in this antitumor effect.