Targeted inhibition of metastatic melanoma through interference with Pin1-FOXM1 signaling.

Melanoma is the most lethal form of skin cancer and successful treatment of metastatic melanoma remains challenging. BRAF/MEK inhibitors only show a temporary benefit due to rapid occurrence of resistance, whereas immunotherapy is mainly effective in selected subsets of patients. Thus, there is a need to identify new targets to improve treatment of metastatic melanoma. To this extent, we searched for markers that are elevated in melanoma and are under regulation of potentially druggable enzymes. Here, we show that the pro-proliferative transcription factor FOXM1 is elevated and activated in malignant melanoma. FOXM1 activity correlated with expression of the enzyme Pin1, which we found to be indicative of a poor prognosis. In functional experiments, Pin1 proved to be a main regulator of FOXM1 activity through MEK-dependent physical regulation during the cell cycle. The Pin1-FOXM1 interaction was enhanced by BRAF(V600E), the driver oncogene in the majority of melanomas, and in extrapolation of the correlation data, interference with\ Pin1 in BRAF(V600E)-driven metastatic melanoma cells impaired both FOXM1 activity and cell survival. Importantly, cell-permeable Pin1-FOXM1-blocking peptides repressed the proliferation of melanoma cells in freshly isolated human metastatic melanoma ex vivo and in three-dimensional-cultured patient-derived melanoids. When combined with the BRAF(V600E)-inhibitor PLX4032 a robust repression in melanoid viability was obtained, establishing preclinical value of patient-derived melanoids for prognostic use of drug sensitivity and further underscoring the beneficial effect of Pin1-FOXM1 inhibitory peptides as anti-melanoma drugs. These proof-of-concept results provide a starting point for development of therapeutic Pin1-FOXM1 inhibitors to target metastatic melanoma.

Loss of JUNB/AP-1 promotes invasive prostate cancer.

Prostate cancer is a frequent cause of male death in the Western world. Relatively few genetic alterations have been identified, likely owing to disease heterogeneity. Here, we show that the transcription factor JUNB/AP-1 limits prostate cancer progression. JUNB expression is increased in low-grade prostate cancer compared with normal human prostate, but downregulated in high-grade samples and further decreased in all metastatic samples. To model the hypothesis that this downregulation is functionally significant, we genetically inactivated Junb in the prostate epithelium of mice. When combined with Pten (phosphatase and tensin homologue) loss, double-mutant mice were prone to invasive cancer development. Importantly, invasive tumours also developed when Junb and Pten were inactivated in a small cell population of the adult anterior prostate by topical Cre recombinase delivery. The resulting tumours displayed strong histological similarity with human prostate cancer. Loss of JunB expression led to increased proliferation and decreased senescence, likely owing to decreased p16(Ink4a) and p21(CIP1) in epithelial cells. Furthermore, the tumour stroma was altered with increased osteopontin and S100 calcium-binding protein A8/9 expression, which correlated with poor prognoses in patients. These data demonstrate that JUNB/AP-1 cooperates with PTEN signalling as barriers to invasive prostate cancer, whose concomitant genetic or epigenetic suppression induce malignant progression.

Fra-1/AP-1 induces EMT in mammary epithelial cells by modulating Zeb1/2 and TGFß expression.

Epithelial-to-mesenchymal transition (EMT) is essential for embryonic morphogenesis and wound healing and critical for tumour cell invasion and dissemination. The AP-1 transcription factor Fra-1 has been implicated in tumorigenesis and in tumour-associated EMT in human breast cancer. We observed a significant inverse correlation between Fra-1 mRNA expression and distant-metastasis-free survival in a large cohort of breast cancer patients derived from multiple array data sets. This unique correlation among Fos genes prompted us to assess the evolutionary conservation between Fra-1 functions in EMT of human and mouse cells. Ectopic expression of Fra-1 in fully polarized, non-tumourigenic, mouse mammary epithelial EpH4 cells induced a mesenchymal phenotype, characterized by a loss of epithelial and gain of mesenchymal markers. Proliferation, motility and invasiveness were also increased in the resulting EpFra1 cells, and the cells were tumourigenic and efficiently colonized the lung upon transplantation. Molecular analyses revealed increased expression of Tgfß1 and the EMT-inducing transcription factors Zeb1, Zeb2 and Slug. Mechanistically, Fra-1 binds to the tgfb1 and zeb2 promoters and to an evolutionarily conserved region in the first intron of zeb1. Furthermore, increased activity of a zeb2 promoter reporter was detected in EpFra1 cells and shown to depend on AP-1-binding sites. Inhibiting TGFß signalling in EpFra1 cells moderately increased the expression of epithelial markers, whereas silencing of zeb1 or zeb2 restored the epithelial phenotype and decreased migration in vitro and tumorigenesis in vivo. Thus Fra-1 induces changes in the expression of genes encoding EMT-related transcription factors leading to the acquisition of mesenchymal, invasive and tumorigenic capacities by epithelial cells. This study defines a novel function of Fra-1/AP-1 in modulating tgfb1, zeb1 and zeb2 expression through direct binding to genomic regulatory regions, which establishes a basis for future in vivo genetic manipulations and preclinical studies using mouse models.

An unusual airplane crash--deadly life saver. Unintentional activation of an automated reserve opening device causing airplane accident.

A Pilatus PC 6 "Turbo-Porter" crashed after having dropped skydivers. The interdisciplinary investigation of the crash revealed that the automated reserve opening device "Student-CYPRES" which the passenger wore on his parachute system had been set off during the landing approach. The parachute pulled the passenger out of the airplane. Subsequently the parachute got caught at the horizontal tail, and its wearer was instantly killed by internal decapitation. The airplane crashed because of its damaged horizontal tail, and the pilot lost his life.