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Melanoma is usually driven by mutations in BRAF or NRAS, which trigger hyperactivation of MAPK signaling. However, MAPK-targeted therapies are not sustainably effective in most patients. Accordingly, characterizing mechanisms that co-operatively drive melanoma progression is key to improving patient outcomes. One possible mechanism is the Hippo signaling pathway, which regulates cancer progression via its central oncoproteins YAP and TAZ, although is thought to be only rarely affected by direct mutation. As YAP hyperactivation occurs in uveal melanoma, we investigated this oncogene in cutaneous melanoma. YAP protein expression was elevated in most benign nevi and primary cutaneous melanomas but present at only very low levels in normal melanocytes. In patient-derived xenografts and melanoma cell lines, we observed variable reliance of cell viability on Hippo pathway signaling that was independent of TAZ activity and also of classical melanoma driver mutations such as BRAF and NRAS. Finally, in genotyping studies of melanoma, we observed the first ever hyperactivating YAP mutations in a human cancer, manifest as seven distinct missense point mutations that caused serine to alanine transpositions. Strikingly, these mutate four serine residues known to be targeted by the Hippo pathway and we show that they lead to hyperactivation of YAP.Implications: Our studies highlight the YAP oncoprotein as a potential therapeutic target in select subgroups of melanoma patients, although successful treatment with anti-YAP therapies will depend on identification of biomarkers additional to YAP protein expression. Mutations and methylation changes in Hippo pathway genes in the TCGA melanoma cohort. A, Somatic coding mutations (top) and CN changes (bottom) affecting Hippo pathway genes identified in patients from the TCGA cohort (56), organized horizontally according to the BRAF-, NRAS-, NF1-, TP53-, RAC1-or PTEN-mutant melanoma subtype of each patient and vertically according the mutation frequency in each Hippo pathway gene. Mutations colored by type: amp, amplification; hemi, hemizygous; homo, homozygous; del, deletion. B, top: distributions of methylation values across 473 TCGA patients in 18 known/predicted oncogenes and 33 known/predicted tumor suppressor genes in the Hippo pathway. Bottom: Spearman coefficient values for correlations between methylation and mRNA expression for each gene. C, Methylation versus mRNA expression plots for YAP and TAZ. Each dot represents values for an individual patient. Blue dots, mutated gene; red dots, wild-type gene. r is the Spearman correlation coefficient; Ã , P < 0.001. YAP and Melanoma

Melanoma is a deadly form of skin cancer that accounts for a disproportionally large proportion of cancer-related deaths in younger people. Compared to most other skin cancers, a feature of melanoma is its high metastatic capacity, although molecular mechanisms that confer this are not well understood. The Hippo pathway is a key regulator of organ growth and cell fate that is deregulated in many cancers. To analyse the Hippo pathway in cutaneous melanoma, we generated a transcriptional signature of pathway activity in melanoma cells. Hippo-mediated transcriptional activity varied in melanoma cell lines but failed to cluster with known genetic drivers of melanomagenesis such as BRAF and NRAS mutation status. Instead, it correlated strongly with published gene expression profiles linked to melanoma cell invasiveness. Consistent with this, the central Hippo oncogene, YAP, was both necessary and sufficient for melanoma cell invasion in vitro. In in vivo murine studies, YAP promoted spontaneous melanoma metastasis, whilst the growth of YAP-expressing primary tumours was impeded. Finally, we identified the YAP target genes AXL, THBS1 and CYR61 as key mediators of YAP-induced melanoma cell invasion. These data suggest that the Hippo pathway is a critical regulator of melanoma metastasis.

Optic nerve hemangioblastoma is a very rare benign tumor with only 39 reported cases by now. It appears to be hyperintense on T2-weighted images with a significant enhancement on contrast scans, which are similar to glioma and meningioma. Due to the lack of specificity in MRI manifestations, optic nerve hemangioblastoma is often misdiagnosed. To provide new insights into differential diagnosis of optic nerve hemangioblastoma, we report for the first time an optic nerve hemangioblastoma case employing advanced magnetic resonance techniques including diffusion-weighted imaging (DWI), apparent diffusion coefficient (ADC) maps, and magnetic resonance angiography (MRA). In addition, we have collected all reported optic nerve hemangioblastoma cases and reviewed their neuroimaging findings by MRI and angiography. Our results show that solid-type tumor is the dominant form of optic nerve hemangioblastoma and extensive edema is widely observed. These findings are surprisingly contrary to manifestations of cerebellar hemangioblastoma. Besides the structural features, quantitative indexes including ADC and relative cerebral blood volume (rCBV) ratio, which are significantly elevated in cerebellar hemangioblastoma, may also shed a light on the preoperative diagnosis of hemangioblastoma of optic nerve. Finally, we discuss the critical neuroimaging features in the differential diagnosis between optic nerve hemangioblastoma from optic pathway glioma and optic nerve sheath meningioma.

Forkhead box (FOX) transcription factors regulate the development of several human cancers. However, the role and therapeutic potential of FOXA1 in gastric cancer is still largely unexplored. The results showed a significant (P < 0.05) upregulation of FOXA1 in gastric cancer tissues and cell lines. Silencing of FOXA1 in gastric cells significantly (P < 0.05) decreased their viability through induction of apoptosis. The induction of apoptosis was associated with upregulation of Bax and downregulation of Bcl-2. Additionally, FOXA1 silencing caused activation of caspase-3 and 9 with no apparent effects on the expression of caspase-8 suggestive of intrinsic apoptosis. The transwell cell invasion revealed significant (P < 0.05) decline of cell invasion of gastric cancer cells upon FOXA1 silencing. The FOXA1 knockdown further inhibited the in vivo tumor growth suggestive of its therapeutic potential. Taken together, the findings of the present revealed that FOXA1 regulates the proliferation and development of gastric cancer and may exhibit therapeutic implications in gastric cancer treatment.

Melanoma is usually driven by mutations in BRAF or NRAS that trigger hyperactivation of mitogen-activated protein kinase (MAPK) signaling. However, MAPK targeted therapies are not sustainably effective in most patients. Accordingly, characterizing mechanisms that cooperatively drive melanoma progression is key to improving patient outcomes. One possible mechanism is the Hippo signaling pathway, which regulates cancer progression via its central oncoproteins YAP and TAZ, although it is relatively rarely affected by direct mutation. As YAP hyperactivation occurs in uveal melanoma, we investigated this oncogene in cutaneous melanoma. YAP protein expression was elevated in most benign nevi and primary cutaneous melanomas but present at only very low levels in normal melanocytes. In patient-derived xenografts and melanoma cell lines, we observed variable reliance of cell viability on Hippo pathway signaling that was independent of classical melanoma driver mutations such as BRAF and NRAS. YAP activity was enriched in invasive melanoma cell lines and was necessary for their invasive properties in culture. In in vivo studies, we found that expression of hyperactive YAP induced spontaneous melanoma metastasis in mice. Finally, in genotyping studies of melanoma, we observed the first ever hyperactivating YAP mutations in a human cancer, manifest as seven distinct missense point mutations that caused serine to alanine transpositions. Strikingly, these mutate four of five known serine residues targeted by the Hippo pathway, and we show that they lead to hyperactivation of YAP function. Our studies highlight the YAP oncoprotein as a potential therapeutic target in select subgroups of melanoma patients, although successful treatment with anti-YAP therapies will depend on identification of biomarkers other than YAP protein expression. Citation Format: Xiaomeng Zhang, Lie Yang, Ismael Vergara, Pacman Szeto, Youfang Zhang, Anthony Papenfuss, Mark Shackleton, Kieran Harvey. The Hippo pathway in melanoma [abstract]. In: Proceedings of the AACR Special Conference on the Hippo Pathway: Signaling, Cancer, and Beyond; 2019 May 8-11; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(8_Suppl):Abstract nr IA03.