DNp73-induced degradation of tyrosinase links depigmentation with EMT-driven melanoma progression.

Melanoma is an aggressive cancer with poor prognosis, requiring personalized management of advanced stages and establishment of molecular markers. Melanomas derive from melanocytes, which specifically express tyrosinase, the rate-limiting enzyme of melanin-synthesis. We demonstrate that melanomas with high levels of DNp73, a cancer-specific variant of the p53 family member p73 and driver of melanoma progression show, in contrast to their less-aggressive low-DNp73 counterparts, hypopigmentation in vivo. Mechanistically, reduced melanin-synthesis is mediated by a DNp73-activated IGF1R/PI3K/AKT axis leading to tyrosinase ER-arrest and proteasomal degradation. Tyrosinase loss triggers reactivation of the EMT signaling cascade, a mesenchymal-like cell phenotype and increased invasiveness. DNp73-induced depigmentation, Slug increase and changes in cell motility are recapitulated in neural crest-derived melanophores of Xenopus embryos, underscoring a previously unnoticed physiological role of tyrosinase as EMT inhibitor. This data provides a mechanism of hypopigmentation accompanying cancer progression, which can be exploited in precision diagnosis of patients with melanoma-associated hypopigmentation (MAH), currently seen as a favorable prognostic factor. The DNp73/IGF1R/Slug signature in colorless lesions might aid to clinically discriminate between patients with MAH-associated metastatic disease and those, where MAH is indeed a sign of regression.

Integrated Loss of miR-1/miR-101/miR-204 Discriminates Metastatic from Nonmetastatic Penile Carcinomas and Can Predict Patient Outcome.

PURPOSE: Penile squamous cell carcinoma is a rare but aggressive cancer. Little is known about pivotal events in tumor pathogenesis and metastasis. Lymph node metastasis is the prevailing prognostic factor while clinical detection in patients remains difficult. Our aim was to identify distinct miRNAs that are differentially expressed in metastatic vs nonmetastatic penile carcinoma, which may serve as diagnostic biomarkers for disease progression. MATERIALS AND METHODS: TaqMan® arrays and quantitative polymerase chain reaction were applied to analyze miRNA profiles in penile squamous cell carcinoma specimens and glans tissue from 24 patients. The prognostic value of deregulated miRNAs was analyzed using the Kaplan-Meier method. The Spearman test was applied to determine a potential linkage between distinctive miRNAs in individual patients. RESULTS: Loss of miR-1 (p = 0.0048), miR-101 (p = 0.0001) and miR-204 (p = 0.0004) in metastasizing tumors and associated metastases (p = 0.0151, 0.0019 and 0.0003, respectively) distinguished patients with metastatic and nonmetastatic penile squamous cell carcinoma. These 3 miRNAs showed a coherent expression pattern. Consistently, patients with low levels of all 3 miRNAs had worse survival (p = 0.03). We identified a coordinately regulated miRNA target hub that is over expressed in penile squamous cell carcinoma and associated with lymphovascular invasion. CONCLUSIONS: Our results provide evidence of a novel multiple miRNA based signature associated with lymph node metastasis and unfavorable prognosis of penile squamous cell carcinoma. The integrated loss of miR-1, miR-101 and miR-204 may predict the formation of metastases in penile cancer at an early stage.

Effect of 10 different polymorphisms on preoperative volumetric characteristics of glioblastoma multiforme.

There is a distinct diversity between the appearance of every glioblastoma multiforme (GBM) on pretreatment magnetic resonance imaging (MRI) with a potential impact on clinical outcome and survival of the patients. The object of this study was to determine the impact of 10 different single nucleotide polymorphisms (SNPs) on various volumetric parameters in patients harboring a GBM. We prospectively analyzed 20 steroid-naïve adult patients who had been treated for newly diagnosed GBM. The volumetry was performed using MRI with the help of a semiautomated quantitative software measuring contrast enhancing tumor volume including necrosis, central necrosis alone and peritumoral edema (PTE). We calculated ratios between the tumor volume and edema (ETR), respectively necrosis (NTR). SNP analysis was done using genomic DNA extracted from peripheral blood genotyped via PCR and sequencing. There was a strong correlation between tumor volume and PTE (p < 0.001), necrosis (p < 0.001) and NTR (p = 0.003). Age and sex had no influence on volumetric data. The Aquaporin 4-31G > A SNP had a significant influence on the ETR (p = 0.042) by decreasing the measured edema compared with the tumor volume. The Interleukin 8-251A > T SNP was significantly correlated with an increased tumor (p = 0.048), PTE (p = 0.033) and necrosis volume (p = 0.028). We found two SNPs with a distinct impact on pretreatment tumor characteristics, presenting a potential explanation for the individual diversity of GBM appearance on MRI and influence on survival.

E2F1 induces miR-224/452 expression to drive EMT through TXNIP downregulation.

Malignant melanoma is highly lethal due to its aggressive invasive properties and metastatic dissemination. The transcription factor E2F1 is crucial for melanoma progression through poorly understood mechanisms. Here, we show that the miR-224/miR-452 cluster is significantly increased in advanced melanoma and invasive/metastatic cell lines that express high levels of E2F1. miR-224/miR-452 expression is directly activated by E2F1 through transactivation of the GABRE gene. Ectopic expression of miR-224/miR-452 in less aggressive cells induces EMT and cytoskeletal rearrangements and enhances migration/invasion. Conversely, miR-224/miR-452 depletion in metastatic cells induces the reversal of EMT, inhibition of motility, loss of the invasive phenotype and an absence of lung metastases in mice. We identify the metastasis suppressor TXNIP as new target of miR-224/miR-452 that induces feedback inhibition of E2F1 and show that miR-224/452-mediated downregulation of TXNIP is essential for E2F1-induced EMT and invasion. The E2F1-miR-224/452-TXNIP axis constitutes a molecular signature that predicts patient survival and may help to set novel therapies.

DNp73 exerts function in metastasis initiation by disconnecting the inhibitory role of EPLIN on IGF1R-AKT/STAT3 signaling.

Dissemination of cancer cells from primary tumors is the key event in metastasis, but specific determinants are widely unknown. Here, we show that DNp73, an inhibitor of the p53 tumor suppressor family, drives migration and invasion of nonmetastatic melanoma cells. Knockdown of endogenous DNp73 reduces this behavior in highly metastatic cell lines. Tumor xenografts expressing DNp73 show a higher ability to invade and metastasize, while growth remains unaffected. DNp73 facilitates an EMT-like phenotype with loss of E-cadherin and Slug upregulation. We provide mechanistic insight toward regulation of LIMA1/EPLIN by p73/DNp73 and demonstrate a direct link between the DNp73-EPLIN axis and IGF1R-AKT/STAT3 activation. These findings establish initiation of the invasion-metastasis cascade via EPLIN-dependent IGF1R regulation as major activity of DNp73.

E2F1 promotes angiogenesis through the VEGF-C/VEGFR-3 axis in a feedback loop for cooperative induction of PDGF-B.

Angiogenesis is essential for primary tumor growth and metastatic dissemination. E2F1, frequently upregulated in advanced cancers, was recently shown to drive malignant progression. In an attempt to decipher the molecular events underlying this behavior, we demonstrate that the tumor cell-associated vascular endothelial growth factor-C/receptor-3 (VEGF-C/VEGFR-3) axis is controlled by E2F1. Activation or forced expression of E2F1 in cancer cells leads to the upregulation of VEGFR-3 and its ligand VEGF-C, whereas E2F1 depletion prevents their expression. E2F1-dependent receptor induction is crucial for tumor cells to enhance formation of capillary tubes and neovascularization in mice. We further provide evidence for a positive feedback loop between E2F1 and VEGFR-3 signaling to stimulate pro-angiogenic platelet-derived growth factor B (PDGF-B). E2F1 or VEGFR-3 knockdown results in reduced PDGF-B levels, while the coexpression synergistically upregulates promoter activity and endogenous protein expression of PDGF-B. Our findings delineate an as yet unrecognized function of E2F1 as enhancer of angiogenesis via regulation of VEGF-C/VEGFR-3 signaling in tumors to cooperatively activate PDGF-B expression. Targeting this pathway might be reasonable to complement standard anti-angiogenic treatment of cancers with deregulated E2F1.

Dissection of cell context-dependent interactions between HBx and p53 family members in regulation of apoptosis: a role for HBV-induced HCC.

Chronic hepatitis B virus (HBV) infection is the major risk for hepatocellular carcinomas (HCC). HBV X protein (HBx) and p53 tumor suppressor family interactions may be crucial for HCC induction. We compared p53 and p73 interactions with HBx in normal and HCC tumor cell lines differing in their p53 status. In the latter, HBx was pro-apoptotic but exhibited opposite effects in non-tumor cells. In these normal cells, p53 and p73 were retained in the cytoplasm. In hepatoma cells, however, HBx led to nuclear translocation of p53 and p73, followed by enhanced transactivation of p53-dependent promoters. The nuclear transfer of p53, but not of p73, was abrogated by protein kinase C inhibitor Gö6976. HBx overexpression in HCC cells led to strong p53 phosphorylation at Ser15, but not in non-tumor cells. Our results define ATM kinase as mediator for HBx-induced p53 phosphorylation. While HBx promotes cell death in p53/p73-positive hepatoma cells also in presence of increased levels of the oncogenic ΔTAp73 isoform, it significantly potentiates ΔTAp73-mediated proliferation and malignant transformation of fibroblasts. Our data suggest that prevention of apoptosis in normal cells by HBx through inhibition of pro-apoptotic p53 family members via direct interaction and coaction with anti-apoptotic ΔTAp73 seems to be the key element in the decision in favor of cell survival. The complex cell context-dependent interactions between p53 family members and HBx in the regulation of apoptosis may be essential in HBV-induced HCC and anticancer therapy.