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Cancer stem cells (CSCs) have been proposed as the driving force of tumorigenesis and the seeds of metastases. However, their existence and role remain a topic of intense debate. Recently, the identification of CSCs in endogenously developing mouse tumours has provided further support for this concept. Here I discuss the challenges in identifying CSCs, their dependency on a supportive niche and their role in metastasis, and propose that stemness is a flexible — rather than fixed — quality of tumour cells that can be lost and gained.
α-catenin exists as part of the cadherin–catenin adhesion complex as well as in a cytoplasmic pool. However, which of these pools is responsible for its biological impact remains controversial. A structure-function analysis in Drosophila melanogaster illuminates how the molecular properties of α-catenin translate into functional outcomes in an intact organism.
Centrosomes play an important role in Drosophila melanogaster stem cells, where the different size and activity of the two centrosomes help these cells divide asymmetrically. The molecular basis of the centrosome asymmetry has remained unclear, but new work highlights the centrosomal protein Centrobin as a key player in this process.
MicroRNAs regulate cancer metastasis by modulating both the intrinsic properties of tumour cells and their interactions with the tumour stroma. Both strands of the miR-126/miR-126* duplex are now shown to simultaneously target the Sdf-1α cytokine to reduce the recruitment of mesenchymal stem cells and inflammatory monocytes to primary tumours, thereby inhibiting lung metastasis.
Endocytosis has proved to be a versatile mechanism regulating diverse cellular processes, ranging from nutrient uptake to intracellular signal transduction. New work reinforces the importance of endocytosis for VEGF receptor signalling and angiogenesis in the developing eye, and describes a mechanism for its differential regulation in angiogenic versus quiescent endothelial cells.
The endoplasmic reticulum (ER) is a heterogeneous organelle with distinct morphologies of sheets and an interconnected network of tubules sharing a common lumen. An ER domain marked by the Rab10 GTPase and several lipid-synthesizing enzymes is implicated in dynamic ER tubule formation and fusion events in cells.
Tumour cells are influenced by their microenvironment, which can promote uncontrolled growth, invasion and metastasis. The GATA3 transcription factor is now shown to regulate the tumour microenvironment by inducing the expression of miR-29b in cancer cells. This microRNA in turn inhibits the expression of genes involved in angiogenesis and extracellular matrix signalling and remodelling to suppress metastasis.
Most organs are composed of tubes of differing cellular architectures, including intracellular 'seamless' tubes. Two studies examining the morphogenesis of the seamless tubes formed by the excretory canal cell in Caenorhabditis elegans reveal a previously unappreciated role for osmoregulation of tubulogenesis: hyperosmotic shock recruits canalicular vesicles to the lumenal membrane to promote seamless tube growth.
Cédric Blanpain discusses the progress achieved in identifying and characterizing the cellular origins of different solid tumours in mouse models of skin, brain, breast, gut and lung cancer, using genetic lineage tracing approaches.
Muller and Vousden discuss the functional outcomes of mutant p53 in cancer and outline the mechanisms through which gain-of-function mutant p53 forms exert their oncogenic effects.
