Chemical screening identifies the ß-Carboline alkaloid harmine to be synergistically lethal with doxorubicin.

Despite being an invaluable chemotherapeutic agent for several types of cancer, the clinical utility of doxorubicin is hampered by its age-related and dose-dependent cardiotoxicity. Co-administration of dexrazoxane as a cardioprotective agent has been proposed, however recent studies suggest that it attenuates doxorubicin-induced antitumor activity. Since compounds of natural origin present a rich territory for drug discovery, we set out to identify putative natural compounds with the view to mitigate or minimize doxorubicin cardiotoxicity. We identify the DYRK1A kinase inhibitor harmine, which phosphorylates Tau that is deregulated in Alzheimer's disease, as a potentiator of cell death induced by non-toxic doses of doxorubicin. These observations suggest that harmine or other compounds that target the DYRK1A kinase my offer a new therapeutic opportunity to suppress doxorubicin age-related and dose-dependent cardiotoxicity.

Chemotherapeutic agents for the treatment of hepatocellular carcinoma: efficacy and mode of action.

Hepatocellular carcinoma (HCC) is a dreaded malignancy that every year causes half a million deaths worldwide. Being an aggressive cancer, its incidence exceeds 700,000 new cases per year worldwide with a median survival of 6-8 months. Despite advances in prognosis and early detection, effective HCC chemoprevention or treatment strategies are still lacking, therefore its dismal survival rate remains largely unchanged. This review will characterize currently available chemotherapeutic drugs used in the treatment of HCC. The respective mode(s) of action, side effects and recommendations will be also described for each drug.

The streptavidin/biotinylated DNA/protein bound complex protocol for determining the association of c-JUN protein with NANOG promoter.

Chromatin immunoprecipitation (ChIP) is a widely used and pre-eminent technique for detecting the association of an individual protein or a particular protein complex with its specific DNA sequence(s) in vivo. Herein we introduce a novel and simple biotinylated-oligonucleotide-mediated ChIP method for testing specific binding of the c-JUN protein to the M1-DNA-regulatory element in the NANOG promoter. We prepared a 260-bp DNA PCR amplicon containing -300 bp to -59 bp, relative to the transcriptional start site of the human NANOG gene, which was transfected into mouse embryonic fibroblasts (MEF) containing wild-type (c-jun(+/+)) or knockout c-jun (c-jun(-/-)) alleles. Whole cells that were cross-linked using formaldehyde and protein-DNA interactions were immunoprecipitated using streptavidin-coupled Dynabeads. Protein-DNA cross-links were reversed during incubation at 95°C, and protein samples were visualized using SDS-PAGE electrophoresis and western blotting. This streptavidin/biotinylated DNA/protein-bound complex protocol can be used for detecting the interactions between multiple transcription factors and their DNA binding sites.

Embryonic NANOG activity defines colorectal cancer stem cells and modulates through AP1- and TCF-dependent mechanisms.

Embryonic NANOG (NANOG1) is considered as an important regulator of pluripotency while NANOGP8 (NANOG-pseudogene) plays a role in tumorigenesis. Herein, we show NANOG is expressed from both NANOG1 and NANOGP8 in human colorectal cancers (CRC). Enforced NANOG1-expression increases clonogenic potential and tumor formation in xenograft models, although it is expressed only in a small subpopulation of tumor cells and is colocalized with endogenous nuclear ß-catenin(High) . Moreover, single NANOG1-CRCs form spherical aggregates, similar to the embryoid body of embryonic stem cells (ESCs), and express higher levels of stem-like Wnt-associated target genes. Furthermore, we show that NANOG1-expression is positively regulated by c-JUN and ß-catenin/TCF4. Ectopic expression of c-Jun in murine Apc(Min/+) -ESCs results in the development of larger xenograft tumors with higher cell density compared to controls. Chromatin immunoprecipitation assays demonstrate that c-JUN binds to the NANOG1-promoter via the octamer M1 DNA element. Collectively, our data suggest that ß-Catenin/TCF4 and c-JUN together drive a subpopulation of CRC tumor cells that adopt a stem-like phenotype via the NANOG1-promoter.

FBXW7 influences murine intestinal homeostasis and cancer, targeting Notch, Jun, and DEK for degradation.

The Fbxw7 (F-box/WD repeat-containing protein 7; also called CDC4, Sel10, Ago, and Fbw7) component of the SCF (Skp1/Cullin/F-box protein) E3 ubiquitin ligase complex acts as a tumor suppressor in several tissues and targets multiple transcriptional activators and protooncogenes for ubiquitin-mediated degradation. To understand Fbxw7 function in the murine intestine, in this study, we specifically deleted Fbxw7 in the murine gut using Villin-Cre (Fbxw7(ΔG)). In wild-type mice, loss of Fbxw7 in the gut altered homeostasis of the intestinal epithelium, resulted in elevated Notch and c-Jun expression, and induced development of adenomas at 9-10 mo of age. In the context of APC (adenomatous polyposis coli) deficiency (Apc(Min/+) mice), loss of Fbxw7 accelerated intestinal tumorigenesis and death and promoted accumulation of ß-catenin in adenomas at late but not early time points. At early time points, Fbxw7 mutant tumors showed accumulation of the DEK protooncogene. DEK expression promoted cell division and altered splicing of tropomyosin (TPM) RNA, which may also influence cell proliferation. DEK accumulation and altered TPM RNA splicing were also detected in FBXW7 mutant human colorectal tumor tissues. Given their reduced lifespan and increased incidence of intestinal tumors, Apc(Min/+)Fbxw7(ΔG) mice may be used for testing carcinogenicity and drug screening.