No abstract

Summary Activation of the PI3K-AKT pathway in tumors is modulated by negative feedback, including mTORC1-mediated inhibition of upstream signaling. We now show that AKT inhibition induces the expression and phosphorylation of multiple receptor tyrosine kinases (RTKs). In a wide spectrum of tumor types, inhibition of AKT induces a conserved set of RTKs including HER3, IGF-1R, and Insulin receptor. This is in part due to mTORC1 inhibition and in part secondary to a FOXO-dependent activation of receptor expression. PI3K-AKT inhibitors relieve this feedback and activate RTK signaling; this may attenuate their antitumor activity. Consistent with this model, we find that, in tumors in which AKT suppresses HER3 expression, combined inhibition of AKT and HER kinase activity is more effective than either alone.

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Nerves are a notable feature of the tumor microenvironment in some epithelial tumors, but their role in the malignant progression of pancreatic ductal adenocarcinoma (PDAC) is uncertain. Here we identify dense innervation in the microenvironment of precancerous pancreatic lesions, known as pancreatic intraepithelial neoplasms (PanIN), and describe a unique subpopulation of neuroendocrine PanIN cells that express the neuropeptide substance P (SP) receptor Neurokinin 1-R (NK1-R). Using organoid culture, we demonstrated that sensory neurons promoted the proliferation of PanIN organoids via SP-NK1-R signaling and Stat3 activation. Nerve-responsive neuroendocrine cells exerted trophic influences and potentiated global PanIN organoid growth. Sensory denervation of a genetically engineered mouse model of PDAC led to loss of Stat3 activation, a decrease in the neoplastic neuroendocrine cell population, and impaired PanIN progression to tumor. Overall, our data provide evidence that nerves of the PanIN microenvironment promote oncogenesis, likely via direct signaling to neoplastic neuroendocrine cells capable of trophic influences. These findings identify neuroepithelial crosstalk as a potential novel target in PDAC treatment.