A combinatorial strategy using YAP and pan-RAF inhibitors for treating KRAS-mutant pancreatic cancer.

KRAS mutation is the most common genetic event in pancreatic cancer. Whereas KRAS itself has proven difficult to inhibit, agents that target key downstream signals of KRAS, such as RAF, are possibly effective for pancreatic cancer treatment. Because selective BRAF inhibitors paradoxically induce downstream signaling activation, a pan-RAF inhibitor, LY3009120 is a better alternate for KRAS-mutant tumor treatment. Here we explored a new combinational strategy using a YAP inhibitor and LY3009120 in pancreatic cancer treatment. We found that reduced YAP expression closely correlates with longer relapse-free and overall survival of patients. Stable knockdown of YAP significantly inhibited pancreatic cancer cell proliferation and tumor growth. In addition, LY3009120 exhibited a dramatically enhanced antitumor effect in combination with YAP knockdown. YAP depletion blocks the activation of a parallel AKT signal pathway after LY3009120 treatment. Finally, combination with a YAP inhibitor, verteporfin, significantly enhanced the antitumor efficacy of LY3009120. Collectively, our results demonstrate that genetic or pharmacological inhibition of YAP can increase sensitivity to LY3009120 in pancreatic cancer through blocking compensatory activation of a parallel AKT signal pathway, thereby validating a combinatorial approach for treating KRAS-mutant pancreatic cancer.