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growth factor receptor-2 (VEGFR-2), whichinhibits angiogenesis. The p53-null lineresponded more poorly to treatment thandid the wild-type line, and the frequency ofapoptotic cells in hypoxic areas of theexperimental tumors was lower in p53-nulltumors than in wild-type tumors. Similarresults were obtained using antibody toVEGFR-2 alone. The authors concludedthat hypoxia-induced tumor cell apoptosismay vary in response to antiangiogenicagents, based on tumor cell p53 status.

These preliminary reports argue that thegoal of antiangiogenic therapy may requirecomplex approaches. An attractive notionwas that we could treat the normalendothelial cell and not have to deal withthe genomic flux and resultant instability ofthe tumor cell. These studies show that thetumor cell response to hypoxia, a presumedconsequence of antiangiogenic therapy,may indeed depend on that flux.

Tumor cell resistance to antiangiogenictherapy through sustained viability or

increased invasion may represent a previ-ously unrecognized challenge. The pres-ence and extent of hypoxia in tumorsshould therefore become an importantmolecular correlate in preclinical and clin-ical trials. Indirect imaging methods beingdeveloped for both animals and humansshould facilitate this. Doppler ultrasoundand blood oxygen level–dependent mag-netic resonance imaging have been used toimage alterations in blood oxygen levelsafter HGF administration in mice8.Another group9 has suggested a scheme toidentify normoxic and hypoxic areas of atumor using functional imaging, followedby their molecular characterization by laser capture microdissection andmicroarray analysis. The development ofcombination therapies to simultaneouslyhalt angiogenesis and tumor cell invasionmay represent an attractive potential solu-tion.

1. Pennacchietti, S. et al. Hypoxia promotes invasivegrowth by transcriptional activation of the met pro-

tooncogene. Cancer Cell 3, 347–361 (2003).2. Trusolino, L. & Comoglio, P. Scatter-factor and

semaphorin receptors: cell signalling for invasivegrowth. Nat. Med. 2, 289–300 (2002).

3. Rofstad, E. et al. Hypoxia promotes lymph nodemetastasis in human melanoma xenografts by up-regulating the urokinase-type plasminogen activator receptor. Cancer Res. 62, 1847–1853(2002).

4. Niizeki, H. et al. Hypoxia enhances the expressionof autocrine motility factor and the motility ofhuman pancreatic cancer cells. Br. J. Cancer 86,1914–1919 (2002).

5. DeJaeger, K., Kavanagh, M.-C. & Hill, R.Relationship of hypoxia to metastatic ability inrodent tumours. Br. J. Cancer 84, 1280–1285(2001).

6. Rofstad, E. & Halsor, E. Hypoxia-associated spon-taneous pulmonary metastasis in human melanomaxenografts: involvement of microvascular hot spotsinduced in hypoxic foci by interleukin 8. Br. J.Cancer 86, 301–308 (2002).

7. Yu, J., Rak, J., Coomber, B., Hicklin, D. & Kerbel,R. Effect of p53 status on tumor response toantiangiogenic therapy. Science 295, 1526–1528(2002).

8. Shaharabany, M. et al. In vivo molecular imaging ofmet tyrosine kinase growth factor receptor activityin normal organs and breast tumors. Cancer Res.61, 4873–4878 (2001).

9. Costouros, N., Diehn, F. & LIbutti, S. Molecularimaging of tumor angiogenesis. J. Cell. Biochem.Suppl. 39, 72–78 (2002).

Figure 1 Oxygen-deprived and dangerous. (a) 1,000–2,000 cells form a spheroid at the start of a collagen invasion assay. (b) Branched tubules arise inresponse to hypoxia. (c) Under normoxic conditions, HGF stimulates branching. (d) Under hypoxic conditions, branching morphogenesis is dramaticallyamplified with addition of HGF.

Letting antibodies get to your headRobert S Fujinami & Thayne L Sweeten

Autoantibodies to group A streptococcocal sugar moieties are now implicated in Sydenham chorea, aneuropsychiatric complication of rheumatic fever. These antibodies appear to disturb neuronal cell functionby binding to glycolipids (pages 914–920).

A simple throat infection with group Astreptococcus can have devastating conse-

quences for certain susceptible individuals,who develop a transient autoimmune dis-ease known as acute rheumatic fever(ARF). Molecular mimicry of antibodiesthat cross-react with epitopes on the bacte-ria and heart instigate the cardiac inflam-mation associated with ARF. There isevidence that similar mechanisms may

have a role in the neuronal aspects of ARF,Sydenham chorea1. The behavioral mani-festations of Sydenham chorea includeabrupt spontaneous movements of the faceand extremities, and sometimes obsessive-compulsive disorder and other maladaptiveneuropsychological behaviors2.

In this issue, Kirvan et al.3 identify in a

The authors are in the Department of Neurology,

University of Utah, 30 North 1900 East, 3R330

SOM, Salt Lake City, Utah 84131-2305, USA.

e-mail: Robert.Fujinami@hsc.utah.edu

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Sydenham chorea patient cross-reactiveautoantibodies that bind to brain ganglio-sides. These autoantibodies alter cellularfunction by activating calcium/calmod-ulin-dependent protein kinase II. Theinvestigators also implicate autoantibodylevels in disease activity in humans. Thestudy provides a long-sought pathologicalmechanism for Sydenham chorea, whichhas been on the rise in the United States—although is still rare in developed nations.The findings could also have relevance forother neuropsychiatric disorders.

There is precedence for modulation ofcellular function by autoantibodies, partic-ularly in myasthenia gravis and Graves dis-ease. In myasthenia gravis, autoantibodiesto the acetylcholine receptor can blockneuromuscular transmission, leading tomuscle weakness and fatigue. In Gravesdisease, autoantibodies against thyroid-stimulating hormone receptor instigate aseries of events eventually leading tohyperthyroidism. In the above two exam-ples, the autoantibodies are directedagainst protein antigens. The autoantibod-ies in the current study instead recognizelipid moieties, which are not convention-ally acknowledged as autoantigens.

To identify target antigens, Kirvan et al.derived human hybridoma lines from aSydenham chorea patient. Each of threecell lines yielded monoclonal antibodiesrecognizing N-acetyl-β-D-glucosamine, themajor immunological epitope of the groupA streptococcal surface carbohydrate.These antibodies cross-reacted with lyso-

ganglioside, a central nervous system gan-glioside known to influence neuronal sig-nal transduction.

The authors found that these cross-reac-tive antibodies were selectively elevated insera and cerebrospinal fluid during acuteSydenham chorea episodes. In additionantibodies to N-acetyl-β-D-glucosaminebound to tissue sections derived fromhuman basal ganglia. Further investigationshowed that binding of this cross-reactiveantibody to lysoganglioside activated cal-cium/calmodulin dependent proteinkinase II, which may regulate neuronalfunctions such as neurotransmitter synthe-sis and release (Fig. 1). Preliminary resultssuggested that binding of the autoantibodyto lysoganglioside increased dopaminerelease in a neuronal cell line.

At least one of the cross-reactive mono-clonal antibodies, as well as active choreasera, induced intracellular signaling ofneuronal cells in vitro. The signaling activ-ity correlated with levels of cross-reactiveantibodies present in sera. The studiespoint out two important features of patho-genic potential: molecular mimicrybetween a carbohydrate epitope (a centralnervous system lysoganglioside) and a gly-colipid molecule (streptococcal N-acetyl-

β-D-glucosamine), and the activation of aprotein kinase involved in neuronal func-tion.

Involvement of neurons in the basal gan-glia is consistent with neuroimaging stud-ies showing enlargement of this region inpatients with Sydenham chorea4. The basalganglia are also well known for their role incoordination of movement. A heightenedsusceptibility of neurons within the basalganglia could explain the involuntarymovements in Sydenham chorea patientsand possibly some of the morbid psycho-logical manifestations.

This autoimmune mechanism hasattractive implications for how we thinkabout other neuropsychiatric diseases.Future studies in this area and extensionsto animal models will further elucidate themechanisms of neuronal dysfunction andwill be necessary to establish causationbetween disease activity and the presenceof autoantibodies. Nevertheless, other psy-chiatric disorders with poorly understoodetiology could have similar pathologicalmechanisms. For instance, growing evi-dence exists for the role of autoimmunemechanisms in disorders such as Tourettesyndrome, obsessive-compulsive disorder2

and autism5,6. The findings of Kirvan et al.

CAM kinase↑

↑ Neurotransmitter?

Movement disordersNeuropsychiatric effects

Gangliosideantibody

Group AStreptococcus Host

Infection

Cross-

reactive

antibodies

cho

Figure 1 Autoantibodies and Sydenham chorea. The pathology of this disease could result from anantibody against a streptococcal surface carbohydrate that cross-reacts with a glycolipid molecule onneurons in the basal ganglia. Autoantibody binding of the glycolipid activates calcium/calmodulin-dependent protein (CaM) kinase in neuronal cells, thus potentially affecting neurotransmitter releaseor other cell functions that could result in the aberrant behaviors seen in Sydenham chorea.

Figure 2 Ganglioside look-alike.

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Polyglutamine neurodegeneration: minding your Ps and QsHenry Paulson

Expanded glutamine repeats cause brain degeneration associated with protein misfolding and aggregation. Twostudies now look beyond the repeat, implicating the phosphatidylinositol-3-kinase (PI-3K)/Akt signaling pathwayand 14-3-3 proteins in polyglutamine toxicity.

Most neurodegenerative disorders that afflicthumans are caused, in part, by abnormalprotein accumulation and aggregation1.Among these disorders, the polyglutaminediseases are particularly intriguing: at leastnine inherited diseases result from CAGrepeat mutations that encode abnormallylong polyglutamine domains in otherwiseunrelated disease proteins. A unifying diseasefeature is the accumulation of mutant polyg-lutamine protein in inclusion bodies withinneurons, often in the nucleus. It is generallyagreed that expanded polyglutamine itselftriggers the disease process, as isolated polyg-lutamine forms aggregates and is toxic toneurons.

But polyglutamine, it seems, is not solely toblame. Two related papers in recent issues ofCell and Neuron highlight the importance oflooking elsewhere in the protein both forclues to pathogenesis and for potential routesto therapy2,3.

Despite sharing essentially the same muta-tion, polyglutamine diseases are clinicallydiverse. Take, for example, the two best-stud-ied polyglutamine diseases, Huntington dis-ease and spinocerebellar ataxia type 1(SCA-1). Physicians can easily distinguishHuntington disease (dementia, psychiatricillness and involuntary movements) fromSCA-1 (ataxia and brainstem signs). Almostcertainly, the chief reason for these differ-ences is the complete lack of similarity, other

than polyglutamine, between huntingtin andataxin-1, the disease proteins in Huntingtondisease and SCA-1, respectively. In each dis-ease, the protein surrounding polyglutamineclearly matters a great deal.

How does protein context contribute to ormodulate polyglutamine toxicity? The cur-rent studies by Orr, Zoghbi and their collabo-rators begin to answer this pressing questionfor SCA-1. Together, the studies suggest thatphosphorylation of ataxin-1 at a site farremoved from the polyglutamine tract has acritical role in pathogenesis, perhaps by pro-moting interactions with the multifunctionalregulator protein, 14-3-3.

These studies build on an impressive bodyof knowledge amassed over the past decadeby the same investigators4. Previous studiesin SCA-1 transgenic mice showed, for exam-ple, that expanded ataxin-1 causes cerebellardegeneration accompanied by nuclear inclu-sion formation, and that ataxin-1 must act in

The author is in the Department of Neurology,

Roy J and Lucille A Carver College of Medicine,

University of Iowa, Iowa City, Iowa 52245, USA.

e-mail: henry-paulson@uiowa.edu

the nucleus to cause neurodegeneration.Further research in a Drosophila model ofSCA-1 has identified trans-acting geneticmodifiers of polyglutamine neurotoxicity5.The most compelling modifiers to date, inSCA-1 flies and other model systems6,7, havebeen molecular chaperones, supporting thehypothesis that protein misfolding and per-turbed protein homeostasis are central topathogenesis.

The Neuron paper describes the pivotalrole of Ser776 in ataxin-1-mediated neurode-generation. Orr and colleagues2 first identi-fied Ser776 as the major phosphorylation sitein ataxin-1, then used a phosphospecificantibody in vivo to confirm that ataxin-1 isphosphorylated at this residue in cerebellarPurkinje cells. Phosphorylated ataxin-1 wasrestricted to the nucleus, the site of toxicity.

This phosporylation seemed to modulateataxin-1 aggregation: in cultured cells,expanded ataxin-1 containing an alanine in

Figure 1 Purkinje cells from 27-week-old mouse brains stained with ataxin-1 (green) and calbindin(red), a calcium-binding protein expressed in Purkinje cells. (a) An image from a mouse expressingmutant ataxin-1 with an expanded polyglutamine tract and a serine at residue 776. (b) Cells from amouse expressing mutant ataxin-1 with alanine at position 776. Orr, Zhoghbi and colleagues showthat phosphorylation of this residue promotes neuropathology.

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justify continuing study of autoimmunemechanisms in a variety of neuropsychi-atric disorders.

1. Husby, G., van de Rijn, I., Zabriskie, J.B., Abdin,Z.H. & Williams, R.C. Jr. Antibodies reacting withcytoplasm of subthalamic and caudate nuclei neu-rons in chorea and acute rheumatic fever. J. Exp.

Med. 144, 1094–1110 (1976).2. Swedo, S.E. et al. High prevalence of obsessive-

compulsive symptoms in patients with Sydenham’schorea. Am. J. Psychiatry 146, 246–249 (1989).

3. Kirvan, C.A., Swedo, S.E., Heuser, J.S. &Cunningham, M.W. Mimicry and autoantibody-mediated neuronal cell signaling in Sydenhamchorea. Nat. Med. 9, 914–920 (2003).

4. Giedd, J.N. et al. Sydenham’s chorea: magnetic res-

onance imaging of the basal ganglia. Neurology 45,2199–2202 (1995).

5. Hollander, E. et al. B lymphocyte antigen D8/17and repetitive behaviors in autism. Am. J.Psychiatry 156, 317–320 (1999).

6. Comi, A.M., Zimmerman, A.W., Frye, V.H., Law, P.A.& Peeden, J.N. Familial clustering of autoimmunedisorders and evaluation of medical risk factors inautism. J. Child Neurol. 14, 388–394 (1999).

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