Although human tumours are shaped by the genetic evolution of cancer cells, evidence also suggests that they display hierarchies related to developmental pathways and epigenetic programs in which cancer stem cells (CSCs) can drive tumour growth and give rise to differentiated progeny1. Yet, unbiased evidence for CSCs in solid human malignancies remains elusive. Here we profile 4,347 single cells from six IDH1 or IDH2 mutant human oligodendrogliomas by RNA sequencing (RNA-seq) and reconstruct their developmental programs from genome-wide expression signatures. We infer that most cancer cells are differentiated along two specialized glial programs, whereas a rare subpopulation of cells is undifferentiated and associated with a neural stem cell expression program. Cells with expression signatures for proliferation are highly enriched in this rare subpopulation, consistent with a model in which CSCs are primarily responsible for fuelling the growth of oligodendroglioma in humans. Analysis of copy number variation (CNV) shows that distinct CNV sub-clones within tumours display similar cellular hierarchies, suggesting that the architecture of oligodendroglioma is primarily dictated by developmental programs. Subclonal point mutation analysis supports a similar model, although a full phylogenetic tree would be required to definitively determine the effect of genetic evolution on the inferred hierarchies. Our single-cell analyses provide insight into the cellular architecture of oligodendrogliomas at single-cell resolution and support the cancer stem cell model, with substantial implications for disease management.

INTRODUCTION Tumor fitness, evolution, and resistance to therapy are governed by selection of malignant cells with specific genotypes, by expression programs related to cellular phenotypes, and by influences of the tumor microenvironment (TME). Although bulk tumor analysis can interrogate the genetic state of tumor cells with high precision, bulk expression profiles average the diverse cells within each tumor, thereby masking critical differences and providing limited insight into cancer cell programs and TME influences. Single-cell RNA sequencing (scRNA-seq) can help to address those challenges but incurs financial and logistic considerations, including the time required to accrue large cohorts of fresh tumor specimen for single-cell analysis. RATIONALE We reasoned that scRNA-seq of a limited number of representative tumors could be combined with bulk data from large cohorts to decipher differences between tumor subclasses. In this approach, bulk samples collected for large cohorts, such as from The Cancer Genome Atlas (TCGA), are first used to define the combined effects of differences in cancer cell genotypes, phenotypes, and the composition of the TME. Single-cell analysis of a limited set of representative tumors is then used to distinguish those effects. We applied this approach to understand the differences between two types of isocitrate dehydrogenase (IDH)-mutant gliomas: astrocytoma (IDH-A) and oligodendroglioma (IDH-O). IDH-A and IDH-O are distinguished by co-occurring signature genetic events and by histopathology and are thought to recapitulate distinct glial lineages. By combining 9879 scRNA-seq profiles from 10 IDH-A tumors, 4347 scRNA-seq profiles from six IDH-O tumors, and 165 TCGA bulk RNA profiles, we could decipher differences between these two tumor types at single-cell resolution. RESULTS We find that differences in bulk expression profiles between IDH-A and IDH-O are primarily explained by the impact of signature genetic events and TME composition, but not by distinct expression programs of glial lineages in the malignant cells. We infer that both IDH-A and IDH-O share the same developmental hierarchy, consisting in each case of three subpopulations of malignant cells: nonproliferating cells differentiated along the astrocytic and oligodendrocytic lineages, and proliferative undifferentiated cells that resemble neural stem/progenitor cells. By analyzing tumors of different clinical grades, we observe that higher-grade tumors present enhanced proliferation, larger pools of undifferentiated glioma cells, and an increase in macrophage over microglia programs in the TME. CONCLUSION Our approach provides a general framework to decipher differences between classes of human tumors by decoupling cancer cell genotypes, phenotypes, and the composition of the TME. The shared glial lineages and developmental hierarchies observed in IDH-A and IDH-O suggest a common progenitor for all IDH-mutant gliomas, shedding light on a longstanding debate in gliomagenesis. In contrast to the similarity in gl...

Circulating tumor cells (CTCs) in women with advanced estrogen receptor-positive/HER2-negative breast cancer acquire a HER2-positive subpopulation following multiple courses of therapy1,2. In contrast to HER2-amplified primary breast cancer, which is highly sensitive to HER2-targeted therapy, the clinical significance of acquired HER2 heterogeneity during the evolution of metastatic breast cancer is unknown. Here, we analyzed CTCs from 19 ER+/HER2− patients, 84% of whom had acquired CTCs expressing HER2. Cultured CTCs maintain discrete HER2+ and HER2− subpopulations: HER2+ CTCs are more proliferative but not addicted to HER2, consistent with activation of multiple signaling pathways. HER2− CTCs show activation of Notch and DNA damage pathways, exhibiting resistance to cytotoxic chemotherapy, but sensitivity to Notch inhibition. HER2+ and HER2− CTCs interconvert spontaneously, with cells of one phenotype producing daughters of the opposite within four cell doublings. While HER2+ and HER2− CTCs have comparable tumor initiating potential, differential proliferation favors the HER2+ state, while oxidative stress or cytotoxic chemotherapy enhances transition to the HER2− phenotype. Simultaneous treatment with paclitaxel and Notch inhibitors achieves sustained suppression of tumorigenesis in orthotopic CTC-derived tumor models. Together, these results point to distinct yet interconverting phenotypes within patient-derived CTCs, contributing to progression of breast cancer and acquisition of drug resistance.

Early proteinuric diabetic nephropathy increases renal expression of the p47phox component of NAD(P)H oxidase and eNOS with increased indices of systemic and renal oxidative/nitrosative stress. An ACEI or an ARB prevents these changes and prevents the development of proteinuria, independent of blood pressure or blood sugar. This finding indicates a pathogenic role for AT1 receptors in the development of oxidative damage in the kidneys during early DM.

Palm F, Onozato ML, Luo Z, Wilcox CS. Dimethylarginine dimethylaminohydrolase (DDAH): expression, regulation, and function in the cardiovascular and renal systems. Am J Physiol Heart Circ Physiol 293: H3227-H3245, 2007. First published October 12, 2007; doi:10.1152 doi:10. /ajpheart.00998.2007 )-dimethylarginine (ADMA) inhibits nitric oxide (NO) synthases (NOS). ADMA is a risk factor for endothelial dysfunction, cardiovascular mortality, and progression of chronic kidney disease. Two isoforms of dimethylarginine dimethylaminohydrolase (DDAH) metabolize ADMA. DDAH-1 is the predominant isoform in the proximal tubules of the kidney and in the liver. These organs extract ADMA from the circulation. DDAH-2 is the predominant isoform in the vasculature, where it is found in endothelial cells adjacent to the cell membrane and in intracellular vesicles and in vascular smooth muscle cells among the myofibrils and the nuclear envelope. In vivo gene silencing of DDAH-1 in the rat and DDAH ϩ/Ϫ mice both have increased circulating ADMA, whereas gene silencing of DDAH-2 reduces vascular NO generation and endothelium-derived relaxation factor responses. DDAH-2 also is expressed in the kidney in the macula densa and distal nephron. Angiotensin type 1 receptor activation in kidneys reduces the expression of DDAH-1 but increases the expression of DDAH-2. This rapidly evolving evidence of isoform-specific distribution and regulation of DDAH expression in the kidney and blood vessels provides potential mechanisms for nephron site-specific regulation of NO production. In this review, the recent advances in the regulation and function of DDAH enzymes, their roles in the regulation of NO generation, and their possible contribution to endothelial dysfunction in patients with cardiovascular and kidney diseases are discussed. nitric oxide synthase; hypertension; diabetes mellitus; chronic kidney disease; asymmetric dimethylarginineis an endogenous methylated amino acid that inhibits the constitutive endothelial (e) or type III and neuronal (n) or type I isoforms of nitric oxide (NO) synthase (NOS) (49,91,103,199). It is a less potent inhibitor of the inducible (i) or type II NOS isoform (41,191,213). Proteins are subject to methylation of arginine residues by protein arginine methyltransferase (PRMT). S-adenosylmethionine, which is synthesized from methionine and ATP, serves as the methyl donor and, in the process, is converted to S-adenosylhomocysteine, which itself can be hydrolyzed to homocysteine. Remethylation of homocysteine in the "remethylation pathway" regenerates methionine (14,179). ADMA is released by protein hydrolysis and exported from the cell and taken up by other cells via system y ϩ carriers of the cationic amino acid (CAT) family (14,196,212). ADMA is eliminated both by renal excretion and metabolic degradation. Its metabolism is facilitated by dimethylarginine dimethylaminohydrolases (DDAHs), which are expressed as type 1 and 2 isoforms. Recent studies have shown differential sites of expression of DDAH-1 and -2 in blo...

Abstract-Phagocytes generate superoxide anion (O 2Ϫ ) by a classic, 5-component NADPH oxidase. O 2 Ϫ contributes to hypertension in spontaneously hypertensive rats (SHR). Therefore, we tested the hypothesis that NADPH oxidase expression is enhanced in the SHR kidney. We also analyzed the localization of NADPH oxidase components in SHR kidney. Renal NADPH oxidase was quantified by reverse transcription-polymerase chain reaction and Western blotting and was localized in SHR and Wistar Kyoto rat (WKY) kidney by immunohistochemistry. The mRNA for 5 subunits of phagocyte NADPH oxidase, and also for MOX1 and RENOX (NOX4), was detected in adult rat kidney. Kidneys of adult (10 weeks old) SHR had a significantly (PϽ0.01) greater mRNA for p47phox (SHR 0.81Ϯ0.05 versus WKY 0.37Ϯ0.01, arbitrary unit), which was confirmed by Western blotting (SHR 0.58Ϯ0.04 versus WKY 0.42Ϯ0.04, arbitrary unit; PϽ0.05) and by immunohistochemistry. This higher p47phox protein expression was also detected in young prehypertensive SHR (SHR 0.61Ϯ0.05 versus WKY 0.39Ϯ0.04, arbitrary unit; PϽ0.01). The 10-week-old SHR contained more modest but significantly (PϽ0.05) greater protein for p67phox (SHR 0.54Ϯ0.02 versus WKY 0.46Ϯ0.02). Immunostaining localized p47phox, p67phox, and p22phox in vasculature, macula densa, distal convoluted tubule, cortical collecting duct, and outer and inner medullary collecting ducts. The kidney of SHR expresses genes for all the main components of phagocyte NADPH oxidase, RENOX, and MOX1. There is a prominent increase in the SHR kidney of the mRNA, and protein expression of p47phox in the vasculature, macula densa, and distal nephron, which precedes development of hypertension. Key Words: oxygen Ⅲ oxidative stress Ⅲ nitric oxide Ⅲ macula densa A erobic organisms generate reactive oxygen species (ROS) during respiration and as a byproduct of specific oxidases. Principal among ROS are superoxide anion (O 2 Ϫ ), hydrogen peroxide (H 2 O 2 ), and hydroxyl radical (OH Ϫ ). The balance between ROS production and the antioxidant defense system determines the degree of oxidative stress. Recent studies implicate the redox state as a determinant of many cellular decisions. 1 Overproduction of ROS contributes to the pathophysiology of hypertension, endothelial dysfunction, renal and vascular injury, diabetes, and atherosclerosis. [2][3][4] Cytosolic enzyme systems contributing to oxidative stress include the extended family of NADPH oxidases. The robust oxidative burst of stimulated phagocytes utilizes the complete NADPH oxidase pathway. The phagocyte NADPH oxidase is a multimolecular enzyme. This is composed of a membrane-associated 22-kDa ␣-subunit (p22phox) and a 91-kDa ␤-subunit (gp91phox), with cytosolic components composed of p47phox, p67phox, and p40phox 5 . Assembly of these units also incorporates a small ATPase, Rac1/Rac2. 5 In rat VSMCs and colon, gp91phox is replaced by the 56% homologous MOX1 10 ; in mouse proximal tubules, by the 57% homologous RENOX. 13 The site of NADPH oxidase expression within the kidney should ...

Activation of NADPH oxidase with translocation of p47phox to the membrane underlies the oxidative stress and limited NO generation, despite enhanced eNOS expression in a model of diabetic nephropathy. Apocynin prevents these changes and the associated proteinuria.

Our data suggest that mucinous adenocarcinoma is typified by (1) frequent KRAS mutations and a growing list of gene fusions, but rare TP53 mutations, (2) a low mutation burden overall, and (3) a recurrence-free survival similar to stage-matched nonmucinous tumors, with recurrences limited to the lungs.