Overexpression of high affinity Type I adenosine receptors promotes the growth of uterine leiomyomas

Leiomyomas are benign proliferations of uterine smooth muscle found in 60% of women. A spatial redistribution of ecto-5'-nucleotidase (CD73, NT5E) that results in reduced extracellular concentrations of adenosine has recently been described in leiomyomas. However, the mechanisms by which altered extracellular adenosine levels contribute to leiomyoma growth remain poorly understood. To address this deficiency, a series of tissue specimens and primary cultures generated from matched specimens of myometrium and leiomyoma were used. Overexpression of Type 1 adenosine receptors (ADORA1) was observed when matched specimens and primary cultures were interrogated by RT-qPCR and western blot. By immunohistochemistry, ADORA1 expression was diffusely observed in myocytes in the leiomyoma complex, with only limited expression in vascular and other structures. Overexpression of ADORA1 was also observed in fibroblasts and multiple smooth muscle subtypes in the leiomyoma complex when single-cell transcriptomics data were interrogated. Incubation with N6-cyclopentyladenosine (CPA), a selective ADORA1 agonist, resulted in decreased proliferation of primary leiomyoma cultures, accompanied by decreased intracellular cAMP and enhanced cyclin D1 and phospho-AKT1 expression. To confirm the specificity of this observation, ADORA1 expression was directly targeted by siRNA, resulting in decreased proliferation, increased intracellular cAMP, and lower levels of cyclin D1 and phospho-AKT1. Collectively, these data indicate that overexpression of the ADORA1 receptor is a robust feature of uterine leiomyomas, where its activation by residual levels of extracellular adenosine potentially contributes to tumor growth by regulating AKT1-mediated signaling.