Rhabdomyosarcoma (RMS) is a highly malignant soft-tissue tumor of childhood deriving from skeletal muscle cells. RMS can be classified in two major histologic subtypes: embryonal (ERMS) and alveolar (ARMS), the latter being characterized by the PAX3/7-FKHR translocation. Here we first investigated whether the Met receptor, a transcriptional target of PAX3 and PAX7, has a role in PAX3-FKHR-mediated transformation. Following PAX3-FKHR transduction, Met was up-regulated in mouse embryonal fibroblasts (MEF), NIH 3T3 and C2C12 cells, and they all acquired anchorage independence. This property was lost in low serum but addition of hepatocyte growth factor/ scatter factor (HGF/SF) rescued soft-agar growth. Genetic proof that Met is necessary for this PAX3-FKHR-mediated effect was obtained by transducing with PAX3-FKHR MEFs derived from Met mutant (Met D/D ) and wild-type (Met +/+ ) embryos. Only Met +/+ MEFs acquired anchorage-independent growth whereas PAX3-FKHR-transduced Met D/D cells were unable to form colonies in soft agar. To verify if Met had a role in RMS maintenance, we silenced the receptor by transducing ERMS and ARMS cell lines with an inducible lentivirus expressing an anti-Met short hairpin RNA (shRNA). Met down-regulation significantly affected RMS cells proliferation, survival, invasiveness, and anchorage-independent growth. Finally, induction of the Met-directed shRNA promoted a dramatic reduction of tumor mass in a xenograft model of RMS. Our data show that both ARMS-and ERMS-derived cell lines, in spite of the genetic drift which may have occurred in years of culture, seem to have retained an ''addiction'' to the Met oncogene and suggest that Met may represent a target of choice to develop novel therapeutic strategies for ARMS.

The nematode Caenorhabditis elegans possesses a unique (with various isoforms) FOXO transcription factor DAF-16, which is notorious for its role in aging and its regulation by the insulin-PI3K-AKT pathway. In humans, five genes (including a protein-coding pseudogene) encode for FOXO transcription factors that are targeted by the PI3K-AKT axis, such as in C. elegans. This common regulation and highly conserved DNA-binding domain are the pillars of this family. In this review, I will discuss the possible meaning of possessing a group of very similar proteins and how it can generate additional functionality to more complex organisms. I frame this discussion in relation to the much larger super family of Forkhead proteins to which they belong. FOXO members are very often co-expressed in the same cell type. The overlap of function and expression creates a certain redundancy that might be a safeguard against the accidental loss of FOXO function, which could otherwise lead to disease, particularly, cancer. This is one of the points that will be examined in this “family affair” report.

CHOP/GADD153 is both an activating and repressing transcription factor that is markedly induced in response to a variety of cellular stresses. The CHOP/ GADD153 gene was originally cloned because of its inducibility by ultraviolet light wavelength band C (UVC) and has since been found to be activated in response to many different cellular stresses. Some of the recent studies have questioned the UVC responsiveness of the CHOP gene. Contradiction in our own data led us to reexamine the UVC effects on CHOP expression. UVC is capable of strongly activating the mouse CHOP promoter in stably transfected NIH 3T3 cells but has only a modest and transient effect on the level of the CHOP messenger RNA. In addition to its positive effect on CHOP promoter activity, we show that UVC negatively affects CHOP mRNA and protein expression. Pretreatment of NIH 3T3 cells with UVC markedly attenuates the subsequent induction of CHOP mRNA by the cellular stress activators methylmethane sulfate, tunicamycin, glucose deprivation, and methionine deprivation for as long as at least 16 h. This inhibitory effect of UVC on CHOP expression in response to stress is independent of the presence or absence of p53 and does not involve mRNA degradation as opposed to the UVC effect that inhibits p21 expression seen only in the absence of p53. The target of the inhibitory effect of UVC on CHOP expression is located in the first exon of the gene, a 5-untranslated region that is unusually conserved between different species. These findings suggest that an unknown function encoded by the 5-untranslated region somehow modifies the response of CHOP gene transcription to UVC.

No abstract

PAX3-FOXO1 (PAX3-FKHR) is the fusion protein produced by the genomic translocation that characterizes the alveolar subtype of Rhabdomyosarcoma, a pediatric sarcoma with myogenic phenotype. PAX3-FOXO1 is an aberrant but functional transcription factor. It retains PAX3-DNA-binding activity and functionally overlaps PAX3 function while also disturbing it, in particular its role in myogenic differentiation. We herein show that PAX3-FOXO1 interferes with normal FOXO function. PAX3-FOXO1 affects FOXO-family member trans-activation capability and the FOXO-dependent TGF-β response. PAX3-FOXO1 may contribute to tumor formation by inhibiting the tumor suppressor activities which are characteristic of both FOXO family members and TGF-β pathways. The recognition of this mechanism raises new questions about how FOXO family members function.

No abstract

No abstract

No abstract