MSI2 promotes translation of multiple IRES-containing oncogenes and virus to induce self-renewal of tumor initiating stem-like cells.

RNA-binding protein Musashi 2 (MSI2) is elevated in several cancers and is linked to poor prognosis. Here, we tested if MSI2 promotes MYC and viral mRNA translation to induce self-renewal via an internal ribosome entry sequence (IRES). We performed RIP-seq using anti-MSI2 antibody in tumor-initiating stem-like cells (TICs).

HMCES Functions in the Alternative End-Joining Pathway of the DNA DSB Repair during Class Switch Recombination in B Cells.

HMCES (5hmC binding, embryonic stem cell-specific-protein), originally identified as a protein capable of binding 5-hydroxymethylcytosine (5hmC), an epigenetic modification generated by TET proteins, was previously reported to covalently crosslink to DNA at abasic sites via a conserved cysteine. We show here that Hmces-deficient mice display normal hematopoiesis without global alterations in 5hmC. HMCES specifically enables DNA double-strand break repair through the microhomology-mediated alternative-end-joining (Alt-EJ) pathway during class switch recombination (CSR) in B cells, and HMCES deficiency leads to a significant defect in CSR.

An Adversarial DNA N-Methyladenine-Sensor Network Preserves Polycomb Silencing.

Adenine N6 methylation in DNA (6mA) is widespread among bacteria and phage and is detected in mammalian genomes, where its function is largely unexplored. Here we show that 6mA deposition and removal are catalyzed by the Mettl4 methyltransferase and Alkbh4 dioxygenase, respectively, and that 6mA accumulation in genic elements corresponds with transcriptional silencing. Inactivation of murine Mettl4 depletes 6mA and causes sublethality and craniofacial dysmorphism in incross progeny.

Erasure of Tet-Oxidized 5-Methylcytosine by a SRAP Nuclease.

Enzymatic oxidation of 5-methylcytosine (5mC) in DNA by the Tet dioxygenases reprograms genome function in embryogenesis and postnatal development. Tet-oxidized derivatives of 5mC such as 5-hydroxymethylcytosine (5hmC) act as transient intermediates in DNA demethylation or persist as durable marks, yet how these alternative fates are specified at individual CpGs is not understood. Here, we report that the SOS response-associated peptidase (SRAP) domain protein Srap1, the mammalian ortholog of an ancient protein superfamily associated with DNA damage response operons in bacteria, binds to Tet-oxidized forms of 5mC in DNA and catalyzes turnover of these bases to unmodified cytosine by an autopeptidase-coupled nuclease.

TLR4 Signaling via NANOG Cooperates With STAT3 to Activate Twist1 and Promote Formation of Tumor-Initiating Stem-Like Cells in Livers of Mice.

Background & Aims: Obesity and alcohol consumption contribute to steatohepatitis, which increases the risk for hepatitis C virus (HCV)-associated hepatocellular carcinomas (HCCs). Mouse hepatocytes that express HCV-NS5A in liver up-regulate the expression of Toll-like receptor 4 (TLR4), and develop liver tumors containing tumor-initiating stem-like cells (TICs) that express NANOG. We investigated whether the TLR4 signals to NANOG to promote the development of TICs and tumorigenesis in mice placed on a Western diet high in cholesterol and saturated fat (HCFD).

NUMB phosphorylation destabilizes p53 and promotes self-renewal of tumor-initiating cells by a NANOG-dependent mechanism in liver cancer.

Unlabelled: Stem cell populations are maintained through self-renewing divisions in which one daughter cell commits to a particular fate whereas the other retains the multipotent characteristics of its parent. The NUMB, a tumor suppressor, in conjunction with another tumor-suppressor protein, p53, preserves this property and acts as a barrier against deregulated expansion of tumor-associated stem cells. In this context, NUMB-p53 interaction plays a crucial role to maintain the proper homeostasis of both stem cells, as well as differentiated cells.

TLR4-dependent tumor-initiating stem cell-like cells (TICs) in alcohol-associated hepatocellular carcinogenesis.

Alcohol abuse predisposes individuals to the development of hepatocellular carcinoma (HCC) and synergistically heightens the HCC risk in patients infected with hepatitis C virus (HCV). The mechanisms of this synergism have been elusive until our recent demonstration of the obligatory role of ectopically expressed TLR4 in liver tumorigenesis in alcohol-fed HCV Ns5a or Core transgenic mice. CD133+/CD49f+ tumor-initiating stem cell-like cells (TICs) isolated from these models are tumorigenic in a manner dependent on TLR4 and NANOG.

Reciprocal regulation by TLR4 and TGF-β in tumor-initiating stem-like cells.

Tumor-initiating stem-like cells (TICs) are resistant to chemotherapy and associated with hepatocellular carcinoma (HCC) caused by HCV and/or alcohol-related chronic liver injury. Using HCV Tg mouse models and patients with HCC, we isolated CD133(+) TICs and identified the pluripotency marker NANOG as a direct target of TLR4, which drives the tumor-initiating activity of TICs. These TLR4/NANOG-dependent TICs were defective in the TGF-β tumor suppressor pathway.

The TBC1D15 oncoprotein controls stem cell self-renewal through destabilization of the Numb-p53 complex.

Stem cell populations are maintained through self-renewing divisions in which one daughter cell commits to a specific fate while the other retains the multipotent characteristics of its parent. The p53 tumor suppressor, in conjunction with its interacting partner protein Numb, preserves this asymmetry and functions as a vital barrier against the unchecked expansion of tumor stem cell pools; however, little is known about the biological control of the Numb-p53 interaction. We show here that Numb and p53 are the constituents of a high molecular mass complex, which is disintegrated upon activation of aPKCζ, a Numb kinase.

Cancer stem cells generated by alcohol, diabetes, and hepatitis C virus.

Cancer stem cells (tumor-initiating stem-like cells: TISCs) are resistant to chemotherapy and are associated with metastatic hepatocellular carcinoma (HCC), which is commonly observed in hepatitis C virus (HCV)-infected patients with obesity or alcohol abuse. However, it is unknown whether the TLR4-NANOG pathway serves as a universal oncogenic signaling in the genesis of TISCs and HCC. We aimed to determine whether Tlr4 is a putative proto-oncogene for TISCs in liver oncogenesis due to different etiologies and how Tlr4 is regulated at the transcriptional and epigenetic levels.

Pluripotency factor-mediated expression of the leptin receptor (OB-R) links obesity to oncogenesis through tumor-initiating stem cells.

Misregulation of a pluripotency-associated transcription factor network in adult tissues is associated with the expansion of rare, highly malignant tumor-initiating stem cells (TISCs) through poorly understood mechanisms. We demonstrate that robust and selective expression of the receptor for the adipocyte-derived peptide hormone leptin (OB-R) is a characteristic feature of TISCs and of a broad array of embryonic and induced pluripotent stem cells and is mediated directly by the core pluripotency-associated transcription factors OCT4 and SOX2. TISCs exhibit sensitized responses to leptin, including the phosphorylation and activation of the pluripotency-associated oncogene STAT3 and induction of Oct4 and Sox2, thereby establishing a self-reinforcing signaling module.

Hypoxia and the unfolded protein response.

Tumor hypoxia refers to the development of regions within solid tumors in which the oxygen concentration is lower (0-3%) compared to that in most normal tissues (4-9%) (Vaupel and Hockel, 2000). Considerable experimental and clinical evidence exists supporting the notion that hypoxia fundamentally alters the physiology of the tumor towards a more aggressive phenotype (Hockel and Vaupel, 2001). Therefore, delineating the mechanisms by which hypoxia affects tumor physiology at the cellular and molecular levels will be crucial for a better understanding of tumor development and metastasis and for designing better antitumor modalities.

Sex preparation and diaphragm acceptability in sex work in Nairobi, Kenya.

Background: Women in sex work stand to benefit if the contraceptive diaphragm alone or combined with a microbicide proves to be an effective barrier method against HIV and sexually transmissible infection (STI). Currently, contraceptive diaphragm users are advised to leave the diaphragm in situ without concomitant use of other intravaginal substances for at least 6 h after intercourse.

Methods: We conducted in-depth interviews on sexual behaviour including post-coital intravaginal practices with 36 women in sex work and 26 of their clients and held two focus-group discussions, each with 10 women.

Identification of mitogen-activated protein kinase signaling pathways that confer resistance to endoplasmic reticulum stress in Saccharomyces cerevisiae.

Hypoxia activates all components of the unfolded protein response (UPR), a stress response initiated by the accumulation of unfolded proteins within the endoplasmic reticulum (ER). Our group and others have shown previously that the UPR, a hypoxia-inducible factor-independent signaling pathway, mediates cell survival during hypoxia and is required for tumor growth. Identifying new genes and pathways that are important for survival during ER stress may lead to the discovery of new targets in cancer therapy.

The unfolded protein response: a novel component of the hypoxic stress response in tumors.

Hypoxia is a physiologically important endoplasmic reticulum (ER) stress that is present in all solid tumors. Numerous clinical studies have shown that tumor hypoxia predicts for decreased local control, increased distant metastases, and decreased overall survival in a variety of human tumors. Hypoxia selects for tumors with an increased malignant phenotype and increases the metastatic potential of tumor cells.

A Sexual Barrier Intervention for HIV+/- Zambian Women: Acceptability and Use of Vaginal Chemical Barriers.

OBJECTIVES: The purposes of this study were to (a) assess the efficacy of a culturally tailored behavioral intervention to increase use and acceptability of sexual barrier products among HIV+ and HIV- Zambian women, (b) compare group versus individual interventions to increase barrier use and acceptability, and (c) validate the role of cultural factors as facilitators or impediments to sexual risk reduction. METHODS: A sample of 150 HIV+ and HIV- Zambian women was recruited from the University Teaching Hospital HIV Voluntary Counseling and Testing Centre, randomized into one of three conditions, and assessed at baseline and 6 months. Group and individual intervention participants attended a 3-session intervention plus pre- and post-HIV test counseling; control participants received pre- and post-test counseling only.

Tumorigenic mutations in VHL disrupt folding in vivo by interfering with chaperonin binding.

The eukaryotic chaperonin TRiC/CCT mediates folding of an essential subset of newly synthesized proteins, including the tumor suppressor VHL. Here we show that chaperonin binding is specified by two short hydrophobic beta strands in VHL that, upon folding, become buried within the native structure. These TRiC binding determinants are disrupted by tumor-causing point mutations that interfere with chaperonin association and lead to misfolding.