Self-renewal is a hallmark of stem cells and cancer, but existence of a shared stemness program remains controversial. Here, we construct a gene module map to systematically relate transcriptional programs in embryonic stem cells (ESCs), adult tissue stem cells, and human cancers. This map reveals two predominant gene modules that distinguish ESCs and adult tissue stem cells. The ESC-like transcriptional program is activated in diverse human epithelial cancers and strongly predicts metastasis and death. c-Myc, but not other oncogenes, is sufficient to reactivate the ESC-like program in normal and cancer cells. In primary human keratinocytes transformed by Ras and I kappa B alpha, c-Myc increases the fraction of tumor-initiating cells by 150-fold, enabling tumor formation and serial propagation with as few as 500 cells. c-Myc-enhanced tumor initiation is cell-autonomous and independent of genomic instability. Thus, activation of an ESC-like transcriptional program in differentiated adult cells may induce pathologic self-renewal characteristic of cancer stem cells.

The Monte Carlo (MC) method has been shown through many research studies to calculate accurate dose distributions for clinical radiotherapy, particularly in heterogeneous patient tissues where the effects of electron transport cannot be accurately handled with conventional, deterministic dose algorithms. Despite its proven accuracy and the potential for improved dose distributions to influence treatment outcomes, the long calculation times previously associated with MC simulation rendered this method impractical for routine clinical treatment planning. However, the development of faster codes optimized for radiotherapy calculations and improvements in computer processor technology have substantially reduced calculation times to, in some instances, within minutes on a single processor. These advances have motivated several major treatment planning system vendors to embark upon the path of MC techniques. Several commercial vendors have already released or are currently in the process of releasing MC algorithms for photon and/or electron beam treatment planning. Consequently, the accessibility and use of MC treatment planning algorithms may well become widespread in the radiotherapy community. With MC simulation, dose is computed stochastically using first principles; this method is therefore quite different from conventional dose algorithms. Issues such as statistical uncertainties, the use of variance reduction techniques, the ability to account for geometric details in the accelerator treatment head simulation, and other features, are all unique components of a MC treatment planning algorithm. Successful implementation by the clinical physicist of such a system will require an understanding of the basic principles of MC techniques. The purpose of this report, while providing education and review on the use of MC simulation in radiotherapy planning, is to set out, for both users and developers, the salient issues associated with clinical implementation and experimental verification of MC dose algorithms. As the MC method is an emerging technology, this report is not meant to be prescriptive. Rather, it is intended as a preliminary report to review the tenets of the MC method and to provide the framework upon which to build a comprehensive program for commissioning and routine quality assurance of MC-based treatment planning systems.

Reciprocal epithelial-mesenchymal interactions shape site-specific development of skin. Here we show that site-specific HOX expression in fibroblasts is cell-autonomous and epigenetically maintained. The distal-specific gene HOXA13 is continually required to maintain the distal-specific transcriptional program in adult fibroblasts, including expression of WNT5A, a morphogen required for distal development. The ability of distal fibroblasts to induce epidermal keratin 9, a distal-specific gene, is abrogated by depletion of HOXA13, but rescued by addition of WNT5A. Thus, maintenance of appropriate HOX transcriptional program in adult fibroblasts may serve as a source of positional memory to differentially pattern the epithelia during homeostasis and regeneration.Supplemental material is available at http://www.genesdev.org.Received August 29, 2007; revised version accepted December 3, 2007. Epithelial tissues such as skin demonstrate remarkable anatomic diversity in their structure and function. For instance, while long terminal hairs decorate the scalp, palmo-plantar skin lacks hairs but possesses thickened epidermal barriers for mechanical stress. These anatomic differences lead to many body site-specific manifestations of diseases and guide their appropriate treatments (Bolognia et al. 2003). Because the epidermis is continually turned over, the apparent stability of sitespecific features raises the fundamental question of how positional identity is acquired and maintained in the skin. Classic heterotypic recombination experiments in chick suggested that a primary dermal signal may dictate the positional identity of epithelial differentiation (Dhouailly 1984). We and others have used a genomic approach to examine the anatomic diversity of gene expression of cell types in the dermis and identified fibroblasts as a cell type that demonstrates consistent and large-scale differences of the expression of cell-cell signaling proteins in a site-specific manner (Chang et al. 2002;Chi et al. 2003;Rinn et al. 2006). Systematic comparison of the global transcriptional programs of fibroblasts from anatomic sites that finely map the body suggest that fibroblasts are differentiated based on their position along three anatomic divisions: anterior-posterior, proximal-distal, and dermal-nondermal (Rinn et al. 2006). Moreover, primary adult fibroblasts retained many features of the embryonic pattern of expression of HOX genes (Chang et al. 2002;Rinn et al. 2006), a family of homeodomain transcription factors that act to specify positional identity during development. These data support the idea, first proposed by Chuong (1993), that a "HOX code" may dictate the positional identity of skin and thus influence site-specific epidermal differentiation. However, fundamental elements of this hypothesis, such as the stability of HOX expression, gene regulatory function, and inductive activities governed by HOX genes in adult fibroblasts remain poorly understood. Here we show that expression of HOXA13 is required and the transcriptio...

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Gaucher disease (GD), the most common lysosomal storage disease, is caused by mutations in GBA1 encoding of β-glucocerebrosidase (GCase). Recently it was reported that progranulin (PGRN) insufficiency and deficiency associated with GD in human and mice, respectively. However the underlying mechanisms remain unknown. Here we report that PGRN binds directly to GCase and its deficiency results in aggregation of GCase and its receptor LIMP2. Mass spectrometry approaches identified HSP70 as a GCase/LIMP2 complex-associated protein upon stress, with PGRN as an indispensable adaptor. Additionally, 98 amino acids of C-terminal PGRN, referred to as Pcgin, are required and sufficient for the binding to GCase and HSP70. Pcgin effectively ameliorates the disease phenotype in GD patient fibroblasts and animal models. These findings not only demonstrate that PGRN is a co-chaperone of HSP70 and plays an important role in GCase lysosomal localization, but may also provide new therapeutic interventions for lysosomal storage diseases, in particular GD.