ROCK2 Inhibition Underlying the Anticancer Effects of Dobutamine: A Novel Proposed Mechanism

Dobutamine, a well-established β₁-adrenergic agonist, has demonstrated anti-proliferative effects against several cancer cell types. However, the molecular mechanism underlying this activity has remained elusive. Collective evidence from the literature indicates that dobutamine-sensitive cancers-including osteosarcoma, gastric adenocarcinoma, and multiple myeloma-frequently overexpress Rho-associated protein kinase 2 (ROCK2). To evaluate the hypothesis that dobutamine can act as a ROCK2 inhibitor.

A comprehensive approach was employed, including enzymatic assays, cell-based proliferation studies in cell lines with differential ROCK2 expression, and computational molecular docking analyses.

Enzyme assays demonstrated that dobutamine inhibits ROCK2 with a half-maximal inhibitory concentration (IC₅₀) of 7.1 µM. In cellular assays, dobutamine induced a ROCK2 expression-dependent anti-proliferative effect, showing approximately fourfold greater potency against the high-ROCK2-expressing HepG2 cell line compared to the low-ROCK2-expressing T-47D cell line. Furthermore, molecular docking studies revealed a plausible ATP-competitive binding mode of dobutamine within the ROCK2 kinase domain, stabilized by key hydrogen bonding, hydrophobic interactions, and π-cation interactions.

Our findings provide the first direct evidence that dobutamine inhibits ROCK2 enzymatic activity, as demonstrated by both enzyme-based and cell-based assays. Moreover, our results validate dobutamine's chemical scaffold as a promising starting point for the structure-based design of more potent and selective ROCK2-targeted anticancer agents. Notably, we identified two major thermodynamic limitations contributing to its suboptimal binding affinity: a high entropic penalty and an enthalpic penalty associated with desolvation. Accordingly, clear medicinal chemistry optimization strategies can be employed to overcome these issues.

This study establishes a novel mechanistic link between dobutamine and ROCK2 inhibition, providing a strong rationale for its therapeutic repurposing.