A cohort of genes associated with embryonic stem (ES) cell behaviour, including NANOG, are expressed in a number of human cancers. They form an ES-like signature we first described in glioblastoma multiforme (GBM), a highly invasive and incurable brain tumour. We have also shown that HEDGEHOG-GLI (HH-GLI) signalling is required for GBM growth, stem cell expansion and the expression of this (ES)-like stemness signature. Here, we address the function of NANOG in human GBMs and its relationship with HH-GLI activity. We find that NANOG modulates gliomasphere clonogenicity, CD133 þ stem cell cell behavior and proliferation, and is regulated by HH-GLI signalling. However, GLI1 also requires NANOG activity forming a positive loop, which is negatively controlled by p53 and vice versa. NANOG is essential for GBM tumourigenicity in orthotopic xenografts and it is epistatic to HH-GLI activity. Our data establish NANOG as a novel HH-GLI mediator essential for GBMs. We propose that this function is conserved and that tumour growth and stem cell behaviour rely on the status of a functional GLI1-NANOG-p53 network.

Constitutive activation of canonical WNT-TCF signaling is implicated in multiple diseases, including intestine and lung cancers, but there are no WNT-TCF antagonists in clinical use. We have performed a repositioning screen for WNT-TCF response blockers aiming to recapitulate the genetic blockade afforded by dominant-negative TCF. We report that Ivermectin inhibits the expression of WNT-TCF targets, mimicking dnTCF, and that its low concentration effects are rescued by direct activation by TCFVP16. Ivermectin inhibits the proliferation and increases apoptosis of various human cancer types. It represses the levels of C-terminal β-CATENIN phosphoforms and of CYCLIN D1 in an okadaic acid-sensitive manner, indicating its action involves protein phosphatases.In vivo, Ivermectin selectively inhibits TCF-dependent, but not TCF-independent, xenograft growth without obvious side effects. Analysis of single semi-synthetic derivatives highlights Selamectin, urging its clinical testing and the exploration of the macrocyclic lactone chemical space. Given that Ivermectin is a safe anti-parasitic agent used by > 200 million people against river blindness, our results suggest its additional use as a therapeutic WNT-TCF pathway response blocker to treat WNT-TCF-dependent diseases including multiple cancers.

The WNT-TCF signaling pathway participates in adult tissue homeostasis and repair, and is hyperactive in a number of human diseases including cancers of the colon. Whereas to date there are no antagonists approved for patient use, a potential problem for their sustained use is the blockade of WNT signaling in healthy tissues, thus provoking potentially serious co-lateral damage. Here we have screened a library of plant and microorganism small molecules for novel WNT signaling antagonists and describe withanolide F as a potent WNT-TCF response blocker. This steroidal lactone inhibits TCF-dependent colon cancer xenograft growth and mimics the effects of genetic blockade of TCF and of ivermectin, a previously reported WNT-TCF blocker. However, withanolide F is unique in that it imposes a long-lasting repression of tumor growth, WNT-TCF targets and cancer stem cell clonogenicity after drug treatment. These findings are paralleled by its modulation of chromatin regulators and its alteration of overall H3K4me1 levels. Our results open up the possibility to permanently repress essential signaling responses in cancer cells through limited treatments with small molecules.

Targeting stemness promises new therapeutic strategies against highly invasive tumors. While a number of approaches are being tested, inhibiting the core transcription regulatory network of cancer stem cells is an attractive yet challenging possibility. Here we have aimed to provide the proof of principle for a strategy, previously used in developmental studies, to directly repress the targets of a salient stemness and pluripotency factor: NANOG. In doing so we expected to inhibit the expression of so far unknown mediators of pro-tumorigenic NANOG function. We chose NANOG since previous work showed the essential requirement for NANOG activity for human glioblastoma (GBM) growth in orthotopic xenografts, and it is apparently absent from many adult human tissues thus likely minimizing unwanted effects on normal cells. NANOG repressor chimeras, which we name NANEPs, bear the DNA-binding specificity of NANOG through its homeodomain (HD), and this is linked to transposable human repressor domains. We show that in vitro and in vivo , NANEP5, our most active NANEP with a HES1 repressor domain, mimics knock-down (kd) of NANOG function in GBM cells. Competition orthotopic xenografts also reveal the effectiveness of NANEP5 in a brain tumor context, as well as the specificity of NANEP activity through the abrogation of its function via the introduction of specific mutations in the HD. The transcriptomes of cells expressing NANEP5 reveal multiple potential mediators of pro-tumorigenic NANEP/NANOG action including intercellular signaling components. The present results encourage further studies on the regulation of context-dependent NANEP abundance and function, and the development of NANEP-based anti-cancer therapies.

Gastrointestinal stromal tumors (GISTs) are a type of mesenchymal tumors. They are rare in rectum. This location is a surgical challenge due to the high morbidity after aggressive surgeries. We present the case of an 81-year-old female with a high-grade GIST treated with transvaginal excision and adjunctive therapy with imatinib. The postoperative period was uneventful without anal dysfunction. Within the types of surgical treatment available, transvaginal excision is an acceptable procedure in lesions located in the rectovaginal region.