Research Report 2010 - MDC

onment, the (cancer) stem cell niche. We have identifieda population of cancer stem cells in mouse epidermaltumors, i.e. early squamous cell carcinomas, whichare dependent on β-catenin and that are phenotypicallyand functionally similar to normal bulge skin stem cells.These cancer stem cells can be isolated by cell sortingbased on the presence of the stem cell marker CD34 andabsence of other markers. In normal mouse skin, CD34 +bulge stem cells account for approximately 1.8% of keratinocytes.However, cutaneous tumors, induced bychemical (DMBA/TPA) carcinogenesis or by expression ofthe Ras oncogene, contain a 9-fold increase of the CD34 +cell population. The tumorigenic capacity of the CD34 +cells was over 100-fold greater than that of unsortedcells, when these were transplanted into the back skin ofNOD/SCID mice. Secondary tumors that formed aftertransplantation resembled the parental tumors; theycontained a small population of CD34 + stem cells.Remarkably, the deletion of β-catenin in DMBA/TPA orRas-induced tumors using an inducible system thatallows conditional mutagenesis after the addition oftamoxifen (K14-cre ERT2 ; β-catenin flox ) resulted in completetumor regression. Thus, canonical Wnt signals arerequired for the maintenance of skin cancer stem cells,whereas in normal skin they instruct bulge stem cellstowards the hair cell fate.The tyrosine phosphatase Shp2 directsNeuregulin-1/ErbB signaling throughoutSchwann cell developmentKatja Grossmann, Hagen Wende, Florian Paul, Cyril Cheret,Alistair Garratt, Daniel Besser, Herbert Schulz, MatthiasSelbach, Walter Birchmeier and Carmen Birchmeier.The non-receptor tyrosine phosphatase Shp2 has beenimplicated in tyrosine kinase, chemokine and integrinreceptor signaling. We have produced a floxed allele ofthe Shp2 gene in mice in order to study the biologicalfunction of this tyrosine phosphatase. We showed thatconditional mutation of Shp2 in neural crest cells and inmyelinating Schwann cells resulted in deficits in glialdevelopment that are remarkably similar to thoseobserved in mice mutant for Neuregulin-1 (Nrg1) or theNrg1 receptors, ErbB2 and ErbB3. In cultured Shp2mutant Schwann cells, Nrg1-evoked cellular responseslike proliferation and migration were virtually abolished,and Nrg1-dependent intracellular signaling wasaltered. Pharmacological inhibition of Src family andMAP kinases mimicked all cellular and biochemicaleffects of the Shp2 mutation, implicating Src as a primaryShp2 target during Nrg1 signaling. Our phenotypicand biochemical analyses thus demonstrate thatShp2 is an essential component in the transduction ofNrg1/ErbB signals.Specific inhibitors of the protein tyrosinephosphatase Shp2 identified by high-throughputdockingKlaus Hellmuth, Ching Tung Lum, Martin Würtele, MartaRosario, Walter Birchmeier, Stefanie Grosskopf (FMP),Jörg Rademann (FMP) and Jens von Kries (FMP).The protein tyrosine phosphatase Shp2 is a positive regulatorof growth factor signaling. Gain-of-functionmutations in several types of leukemia define Shp2 as abona fide oncogene. We performed a high-throughputin silico screen for small-molecular-weight compoundsthat bind the catalytic site of Shp2. We have identifiedthe phenylhydrazonopyrazolone sulfonate PHPS1 as apotent and cell-permeable inhibitor, which is specificfor Shp2 over the closely related tyrosine phosphatasesShp1 and PTP1B. PHPS1 inhibits Shp2-dependent cellularevents such as hepatocyte growth factor/scatter factor(HGF/SF)-induced epithelial cell scattering and branchingmorphogenesis. PHPS1 also blocks Shp2-dependentdownstream signaling, namely HGF/SF-induced sustainedphosphorylation of the Erk1/2 MAP kinases anddephosphorylation of paxillin. Furthermore, PHPS1 efficientlyinhibits activation of Erk1/2 by the leukemiaassociatedShp2 mutant, Shp2-E76K, and blocks theanchorage-independent growth of a variety of humantumor cell lines. The PHPS compound class is thereforesuitable for further development of therapeutics for thetreatment of Shp2-dependent diseases.Selected PublicationsKlaus, A., and Birchmeier, W. (2008): Wnt signalling and its impact ondevelopment and cancer. Nature Rev. Cancer 8, 387-398Grigoryan, T., Wend, P., Klaus, A., and Birchmeier, W. (2008): Decipheringthe function of canonical Wnt signals in development and disease: conditionalloss- and gain-of-function mutations of beta-catenin in mice.Genes & Development 22, 2308-2341Malanchi, I., Peinado, H., Kassen, D., Hussenet, T., Metzger, D., Chambon,P., Huber, M., Hohl, D., Cano, A., Birchmeier, W., and Huelsken, J. (2008):Cutaneous cancer stem cell maintenance is dependent on beta-cateninsignalling. Nature 452, 650-654Hellmuth, K., Grosskopf, S., Tung Lum, C., Wuertele, M., Roeder, N., Kries v.,JP, Rosário, M., Rademann, J., and Birchmeier, W. (2008): Specific inhibitorsof the protein tyrosine phosphatase Shp2 identified by high-throughputdocking. Proc. Natl. Acad. Sci. USA. 105, 7275-7280Fritzmann, J., Morkel, M., Besser, D., Budczies, J., Kosel, F., Brembeck, F.H.,Stein, U., Fichtner, I., Schlag, P.M., and Birchmeier, W. (2009): A colorectalcancer expression profile that includes transforming growth factor betainhibitor BAMBI predicts metastatic potential. Gastroenterology 137,165-175PatentMDC 0501: Shp-2 inhibitors, pharmaceutical compositions comprisingthem and their use for treating phosphatase-mediated diseases.W. Birchmeier, K. Hellmuth. EP 05 090 160.2.Cancer Research 85