STK38/L promote tissue growth and cancer by inhibiting the Hippo pathway

The Hippo pathway is a key regulator of development, regeneration, tissue homeostasis, and organ size, and its dysregulation promotes tumorigenesis. However, the precise mechanisms of its regulation in both normal physiology and cancer remain incompletely understood. Here, we identify STK38 and STK38L (also known as NDR1 and NDR2), previously proposed as redundant kinases of LATS, as negative regulators of the Hippo pathway. STK38/L inhibit LATS by competitively binding to MOB1 and disrupting the LATS-MOB1 complex, a process independent of their kinase activity. This inhibitory mechanism is evolutionarily conserved, as the Drosophila ortholog Tricornered similarly impairs Warts-Mats complex formation, resulting in enlarged fly wing size. Pathologically, STK38L is highly expressed in ovarian cancer and required for ovarian tumor growth, and its amplification correlates with YAP activation and increased tumor sensitivity to TEAD inhibitors. Taken together, our study reveals a conserved role of STK38/L in Hippo pathway regulation, providing new insights into Hippo-dependent growth control and cancer development.