ULK1 (unc-51 like autophagy activating kinase 1), the key mediator of MTORC1 signaling to autophagy, regulates early stages of autophagosome formation in response to starvation or MTORC1 inhibition. How ULK1 regulates the autophagy induction process remains elusive. Here, we identify that ATG13, a binding partner of ULK1, mediates interaction of ULK1 with the ATG14-containing PIK3C3/VPS34 complex, the key machinery for initiation of autophagosome formation. The interaction enables ULK1 to phosphorylate ATG14 in a manner dependent upon autophagy inducing conditions, such as nutrient starvation or MTORC1 inhibition. The ATG14 phosphorylation mimics nutrient deprivation through stimulating the kinase activity of the class III phosphatidylinositol 3-kinase (PtdIns3K) complex and facilitates phagophore and autophagosome formation. By monitoring the ATG14 phosphorylation, we determined that the ULK1 activity requires BECN1/Beclin 1 but not the phosphatidylethanolamine (PE)-conjugation machinery and the PIK3C3 kinase activity. Monitoring the phosphorylation also allowed us to identify that ATG9A is required to suppress the ULK1 activity under nutrient-enriched conditions. Furthermore, we determined that ATG14 phosphorylation depends on ULK1 and dietary conditions in vivo. These results define a key molecular event for the starvation-induced activation of the ATG14-containing PtdIns3K complex by ULK1, and demonstrate hierarchical relations between the ULK1 activation and other autophagy proteins involved in phagophore formation.

Summary MAPK and AKT pathways are frequently co-activated in melanoma through overexpression of receptor tyrosine kinases, mutations in their signaling surrogates, such as RAS and BRAF, or loss of negative regulators such as PTEN. Since RAS can be a positive upstream regulator of PI3-K, it has been proposed that the loss of PTEN and the activation of RAS are redundant events in melanoma pathogenesis (Tsao et al., 2000). Here, in genetically engineered mouse models of cutaneous melanomas, we sought to better understand the genetic interactions between HRAS activation and PTEN inactivation in melanoma genesis and progression in vivo. We showed that HRAS activation cooperates with Pten+/- and Ink4a/Arf-/- to increase melanoma penetrance and promote metastasis. Correspondingly, gain- and loss-of-function studies established that Pten loss increases invasion and migration of melanoma cells and non-transformed melanocytes, and that such biological activity correlates with a shift to phosphorylation of AKT2 isoform and E-cadherin down-regulation. Thus, Pten inactivation can drive the genesis and promote the metastatic progression of RAS activated Ink4a/Arf deficient melanomas.

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We have reported that a 10-herbal traditional formula containing Korean Angelica gigas Nakai (AGN) exerts potent anti-cancer efficacy and identified decursin and decursinol angelate (DA) from AGN as novel anti-androgens. Here, we determined whether AGN would exert in vivo anti-cancer activity and whether decursin or DA could account for its efficacy. The AGN ethanol extract was tested against the growth of mouse Lewis lung cancer (LLC) allograft in syngenic mice or human PC-3 and DU145 prostate cancer xenograft in immunodeficient mice. The pharmacokinetics of decursin and DA were determined. The AGN extract significantly inhibited LLC allograft growth (30 mg/kg) and PC-3 and DU145 xenograft growth (100 mg/kg) without affecting the body weight of the host mice. Biomarker analyses revealed decreased cell proliferation (Ki67, PCNA), decreased angiogenesis (VEGF, microvessel density) and increased apoptosis (TUNEL, cPARP) in treated tumors. Decursin and DA injected intraperitoneally were rapidly hydrolyzed to decursinol. Decursinol and decursin at 50 mg/kg inhibited LLC allograft growth to the same extent, comparable to 30 mg AGN/kg. Therefore the AGN extract possessed significant in vivo anti-cancer activity, but decursin and DA only contributed moderately to that activity, most likely through decursinol.