Barry Anderson, M.D., Ph.D.
Senior Investigator, Pediatric Section
Clinical Investigations Branch
Cancer Therapy Evaluation Program, DCTD
National Cancer Institute
Executive Plaza North, Room 7025
6130 Executive Boulevard
Rockville, MD 20852
Telephone: (301) 496-2522
Fax: (301) 402-0557

Suzanne Baker, Ph.D.
Associate Member
Department of Developmental Neurobiology
St. Jude Children's Research Hospital
332 North Lauderdale
Memphis, TN 38105
Telephone: (901) 495-2254
Fax: (901) 495-2270

Frederic G. Barr, M.D., Ph.D.
Associate Professor, Pathology and Laboratory Medicine
University of Pennsylvania School of Medicine
36th Street and Hamilton Walk
Philadelphia, PA 19104-6082
Telephone: (215) 898-0884
Fax: (215) 898-4227

Dafna Benayahu, Ph.D.
Department of Cellular and Developmental Biology
Sackler School of Medicine
Tel Aviv University
69978 Tel Aviv
Israel
Telephone: 972-3-640-6187
Fax: 972-3-640-7432

Peter Besmer, Ph.D.
Member and Professor
Developmental Biology Program
Memorial Sloan-Kettering Cancer Center
1275 York Avenue
New York, NY 10021
Telephone: (212) 639-8188
Fax: (212) 422-2355

Paolo Bianco, M.D.
Professor of Anatomic Pathology
Dipartimento di Medicina Sperimentale e Patologia
La Sapienza University Rome Italy
Viale Regina Elena 324
00161 Roma
Italy
Telephone: 39-06-444-1049
Fax: 39-06-494-0896

David Bodine, Ph.D.
Chief, Hematopoiesis Section
Genetics and Molecular Biology Branch
National Human Genome Research Institute
Building 49, Room 3A04
Bethesda, MD 20892-4442
Telephone: (301) 402-0902
Fax: (301) 402-4929

Arnold I. Caplan, Ph.D.
Professor, Department of Biology
Skeletal Research Center
Case Western Reserve University
2080 Adelbert Road
Cleveland, OH 44106
Telephone: (216) 368-3562
Fax: (216) 368-4077

Carlos Cordon-Cardo, M.D., Ph.D.
Director, Division of Molecular Pathology
Memorial Sloan-Kettering Cancer Center
1275 York Avenue, Box 105
New York, NY 10021
Telephone: (212) 639-7746
Fax: (212) 794-7746

Christopher Denny, M.D.
Professor, UCLA School of Medicine
University of California, Los Angeles
A2-312 MDCC, UCLA Medical Center
Los Angeles, CA 90095
Telephone: (310) 825-0704
Fax: (310) 267-2848

David E. Fisher, M.D., Ph.D.
Department of Pediatric Hematology/Oncology
Dana Farber Cancer Institute
Harvard Medical School
44 Binney Street, Room D630
Boston, MA 02115
Telephone: (617) 632-4916
Fax: (617) 632-2085

Christopher Fletcher, M.D.
Professor of Pathology
Harvard Medical School
Brigham and Women's Hospital
75 Francis Street
Boston, MA 02115
Telephone: (617) 732-8558
Fax: (617) 566-3897

Jonathan Fletcher, M.D.
Associate Professor, Pathology and Pediatrics
Harvard Medical School
Brigham and Women's Hospital
75 Francis Street
Boston, MA 02115
Telephone: (617) 732-5152
Fax: (617) 278-6921

Richard Gorlick, M.D.
Chief, Pediatric Hematology/Oncology
Children's Hospital of Montefiore
3415 Bainbridge Avenue, Rosenthal 3rd Floor
Bronx, NY 10467
Telephone: (718) 741-2333
Fax: (718) 920-6506

Carl Gregory, Ph.D.
Research Instructor
Center for Gene Therapy
Tulane University Health Sciences Center
6th Floor JBJ Building
1430 Tulane Avenue
New Orleans, LA 70112
Telephone: (504) 988-7716
Fax: (504) 988-7710

Gerard C. Grosveld, Ph.D.
Chairman and Member
Department of Genetics and Tumor Cell Biology
St. Jude Children's Research Hospital
332 North Lauderdale
Memphis, TN 38105
Telephone: (901) 495-2692
Fax: (901) 526-2907

Lee J. Helman, M.D.
Chief, Pediatric Oncology Branch, CCR
National Cancer Institute
Building 10, Room 13N240
Bethesda, MD 20892-1928
Telephone: (301) 496-4257
Fax: (301) 480-4318

Janet M. Hock, B.D.S., Ph.D.
Professor and Program Director
IUCC Bone Cancers Research Center
Department of Anatomy and Cell Biology
Indiana University School of Medicine
635 Barnhill Drive, MS 5045A
Indianapolis, IN 46202
Telephone: (317) 274-1283
Fax: (317) 278-2040

Pancras C.W. Hogendoorn, M.D., Ph.D.
Professor, Department of Pathology
Leiden University Medical Center
P.O. Box 9600, L1-Q
2300 RC Lenide
The Netherlands
Telephone: 31-71-526-6639
Fax: 31-71-524-8158

Siwen Hu, M.D., Ph.D.
Postdoctoral Fellow
Department of Pathology
Children's Hospital Los Angeles
Keck School of Medicine
University of Southern California
4650 Sunset Boulevard, SRT 1015, MS 103
Los Angeles, CA 90027
Telephone: (323) 669-5607
Fax: (323) 671-3669

Chand Khanna, D.V.M., Ph.D.
Head, Tumor and Metastasis Biology Section
Pediatric Oncology Branch, CCR
National Cancer Institute
9610 Medical Center Drive, Room 315
Rockville, MD 20850
Telephone: (301) 594-3406
Fax: (301) 594-4422

Marc Ladanyi, M.D.
Associate Member
Department of Pathology
Memorial Sloan-Kettering Cancer Center
1275 York Avenue, Room S-801
New York, NY 10021
Telephone: (212) 639-6369
Fax: (212) 717-3515

Nadim Mahmud, M.D., Ph.D.
Director and Assistant Professor
Department of Hematology and Oncology
University of Illinois Medical Center at Chicago
MBRB, Room 3150, MC 734
900 South Ashland Avenue
Chicago, IL 60607
Telephone: (312) 413-9183
Fax: (312) 413-7963

Robert Maki, M.D., Ph.D.
Co-Director, Sarcoma Disease Management Team
Assistant Member
Memorial Sloan-Kettering Cancer Center
1275 York Avenue, Box 223
New York, NY 10021-6007
Telephone: (212) 639-5720
Fax: (646) 422-2076

Paul Meltzer, M.D., Ph.D.
Senior Investigator
Molecular Genetics Section
National Human Genome Research Institute
Building 50, Room 5140
Bethesda, MD 20892
Telephone: (301) 594-5283
Fax: (301) 480-3281

Glenn Merlino, Ph.D.
Chief, Molecular Genetics Section
Laboratory of Molecular Biology, CCR
National Cancer Institute
Building 37, Room 5002
Bethesda, MD 20892-4264
Telephone: (301) 496-4270
Fax: (301) 480-7618

William Pavan, Ph.D.
Senior Investigator
National Human Genome Research Institute
Building 49, Room 4A82
Bethesda, MD 20892
Telephone: (301) 496-7584
Fax: (301) 402-2170

Donald G. Phinney, Ph.D.
Associate Professor
Center for Gene Therapy
Tulane University Health Sciences Center
1430 Tulane Avenue
New Orleans, LA 70112
Telephone: (504) 988-7725
Fax: (504) 988-7710

Mark F. Pittenger, Ph.D.
Vice President of Research
Osiris Therapeutics, Inc.
2001 Aliceanna Street
Baltimore, MD 21231
Telephone: (410) 522-5005, ext. 237
Fax: (410) 563-0794

Darwin J. Prockop, M.D., Ph.D.
Director, Center for Gene Therapy
Tulane University Health Sciences Center
1430 Tulane Avenue, SL-99
New Orleans, LA 70112
Telephone: (504) 988-7711
Fax: (504) 988-7710

Brian P. Rubin, M.D., Ph.D.
Assistant Professor and Director
Bone and Soft Tissue Pathology
Department of Anatomic Pathology
University of Washington Medical Center
1959 N.E. Pacific Street, Box 356100
Seattle, WA 98195
Telephone: (206) 598-5024
Fax: (206) 598-8697

Michael A. Rudnicki, Ph.D.
Director and Senior Scientist, Molecular Medicine
Ottawa Health Research Institute
501 Smyth Road
Ottawa, Ontario K1H 8L6
Canada
Telephone: (613) 739-6740
Fax: (613) 737-8803

Scott Saxman, M.D.
Senior Investigator, Clinical Investigation Branch
Cancer Therapy Evaluation Program, DCTD
National Cancer Institute
Executive Plaza North, Room 7025
6130 Executive Boulevard
Bethesda, MD 20892-7436
Telephone: (301) 496-2522
Fax: (301) 402-0557

Stephen X. Skapek, M.D.
Assistant Member
Department of Hematology/Oncology and
Molecular Therapeutics Laboratory
St. Jude Children's Research Hospital
332 North Lauderdale Street
Memphis, TN 00003-8105
Telephone: (901) 495-4019
Fax: (901) 495-3966

Malcolm A. Smith, M.D., Ph.D.
Associate Branch Chief for Pediatrics
Clinical Investigations Branch
Cancer Therapy Evaluation Program, DCTD
National Cancer Institute
Executive Plaza North, Room 7025
6130 Executive Boulevard
Rockville, MD 20852
Telephone: (301) 496-2522
Fax: (301) 402-0557

Poul Sorensen, M.D, Ph.D.
Professor, Department of Pathology
University of British Columbia
950 West 28th Avenue, Room 3082
Vancouver, BC V5Z 4H4
Canada
Telephone: (604) 875-2936
Fax: (604) 875-3417

Clifford Tabin, Ph.D.
Professor, Department of Genetics
Harvard Medical School
New Research Building, 3rd Floor
77 Avenue Louis Pasteur
Boston, MA 02115
Telephone: (617) 432-7618
Fax: (617) 432-7595

Mark Thornton, M.D.
President
Sarcoma Foundation of America
26120 Kings Valley Road
Damascus, MD 20872
Telephone: (301) 520-7648
Fax: (301) 482-2303

Timothy J. Triche, M.D., Ph.D.
Professor, Keck School of Medicine
Children's Hospital Los Angeles
University of Southern California
4650 Sunset Boulevard, Mail Stop 43
Los Angeles, CA 90027
Telephone: (323) 669-4516
Fax: (323) 667-1123

Matt van de Rijn, M.D., Ph.D.
Associate Professor
Department of Pathology
Stanford University Medical Center
300 Pasteur Drive, L 235
Stanford, CA 94305
Telephone: (650) 498-7154
Fax: (650) 725-6902

Catherine M. Verfaillie, M.D.
Director, Stem Cell Institute
University of Minnesota
420 Delaware Street, S.E., MMC 716
Minneapolis, MN 55455
Telephone: (612) 625-0602
Fax: (612) 624-2436

Adult MSC constitute a source and lineage for the mesenchymal connective tissues in the postnatal human. The postembryonic locations of MSC are the bone marrow, a privileged site of a stem cell reserve, and a locally positioned number of satellite cells associated with each nonhematopoietic tissue type. The satellite cells serve to replace, repair, and regenerate damaged tissue; however, these peripherally located MSC are not tissue histology specific. The differentiation of mesenchymal progenitor cells into particular histologic tissue may result from cellular intrinsic properties (receptors or transcription factors), growth factors and cytokines, and cell-cell signaling and local tissue interactions. It is unclear whether mesenchymal adult pluripotent cells or mesenchymal progenitor cells represent mesenchymal stem cells. Additionally, there is plasticity among MSC even when they have reached a differentiation state that is influenced by external factors that can direct individual clone lineage progression. The steps in differentiation and the cytokines and growth factors needed to advance MSC toward differentiation are consistent with those known from developmental biology and the pathways of embryology. Interestingly, the satellite cells have a trophic activity that includes: (1) anti-fibrotic; (2) angiogenic; (3) anti-apoptotic; and (4) mitosis promoting in a regenerative milieu.

The study of MSC is just beginning to grasp the difference between the in vivo mesenchymal progenitors and the MSC existing in laboratory conditions. Investigations are currently limited by the isolation of MSC by long-term culture of bone marrow cells; limited surface markers for reliably identifying a true MSC; very limited gene array profiling of MSC; and only a limited number of functional pathways for controlling MSC replication, differentiation, and dormancy (FGF2 Dkk-1 and ERK). Gene expression profiling by serial analysis of gene expression (SAGE) has been undertaken and suggests that the regulatory activities (neuro-regulatory, immunomodulatory, bone turnover, pro-angiogenic, anti-apoptotic) of MSCs may make a greater contribution to the repair benefit effected by the MSC than direct tissue replacement activity. The influence of such regulatory activity or loss of these effects and its possible relationship to malignant transformation of mesenchymal tissue was discussed. There is likely a regulatory component for eventual stem cell lineage commitment based on cell shape and cytoskeleton that is invoked in particular laboratory conditions. Gene expression of MSC is influenced by the in vitro cell environment and the culture media, and the gene expression varies according to which mature mesenchymal tissue is developed. The possibility that de-differentiation of "mature" mesenchymal tissue could lead to malignant transformation or that signals identified with differentiation/de-differentiation could be relevant to the understanding of sarcoma formation was discussed.

Sarcoma is thought by sarcoma biologists possibly to derive from autonomous proliferation of “mature” mesenchymal tissues, which has the ability to be angioinvasive and metastasize. The histologic tissue identified with sarcomas normally has limited capacity for self-renewal and no “sarcoma” stem cell has been identified in vivo, so the origin of sarcoma cells is unknown. It seems doubtful that they derive from their histologic tissue because differentiated mesenchymal cells are thought to be unable to replicate. There is the possibility of some subpopulation of mesenchymal cells retaining replication competence, as would be the case for a stem cell. Or, as posed for normal MSC, the sarcomas could derive from adult stem cells within the tissue or originating in the bone marrow. This is further complicated by the general finding of two broad groups within sarcomas: those with specific genetic alterations resulting in fusion proteins through reciprocal translocations or point mutations and those with nonspecific complex unbalanced karyotypes. For the specific chromosomal translocations, it is unclear what cells the translocations occur in and the relationship between the cell lineage and the gene fusion function is unknown. Among the sarcomas with complex karyotypes, there are few clues as to the preceding lesion(s) or cell of origin. Interestingly, although most sarcomas show only one line of differentiation, a substantial number do show additional lines of differentiation (i.e., liposarcoma may also include bone or muscle tissue). Also, there exists a small number of sarcomas, usually found in younger patients, that does not have a normal histology counterpart.

However, investigations of the molecular and genetic factors leading to sarcoma cell development have revealed specific reciprocal chromosomal translocations that correspond with specific histologic subtypes of sarcoma such as Ewing’s sarcoma (EWS-Fli) and rhabdomyosarcoma (PAX3-FKHR). These translocations create fusion genes that clearly play a role in tumorigenesis, but the interaction of the fusion gene product with other elements of MSC differentiation and lineage commitment remain unclear. While many genetic and signal-pathway abnormalities have been identified in sarcomas, their influence in determining cell transformation and consequence on downstream signaling is not clearly understood. Importantly, the determination of which abnormalities are vital to tumor cell replication and survival may identify potential tumor-specific targets for molecularly targeted therapeutics, as has been the case with the targeting of the c-KIT receptor tyrosine kinase of gastrointestinal stromal tumors (GISTs) by imatinib, a c-KIT tyrosine kinase inhibitor.

Many growth signaling factors and cell cycle regulatory pathways that function in normal cell development are activated in sarcomas, and the source of non-genetic activation (via growth factors) that has a role in the altered growth of mature tissue could relate to the activity of cells in the local tissue environment (i.e., stromal tissue), such as MSC satellite cells. Sarcoma biologists have defined fusion proteins and genetic translocations that define and identify specific sarcoma tumor cells. A variety of signal pathways related to tumor cell replication, apoptosis, and treatment resistance have been characterized in an effort to establish possible targeted therapy vulnerability. Despite these advances, the cellular etiology of each histological tumor type remains unknown, and the relationship of the defined fusion proteins/translocations to the malignant process remains unclear.

Participants considered the following issues during discussions:

1. Do some sarcoma cell lines derive from pluripotent stem cells with oncogene-induced differentiation program? If so, could you trade out oncogene-mediated differentiation program with the sarcoma cell line to convert the sarcoma phenotype?
2. Could the differentiation of oncogenes be a secondary event in sarcoma etiology, that is, could a primitive sarcoma cell differentiate toward particular tumor histology with oncogene development?
3. Does the plasticity found by developmental biologists between muscle stem cells, satellite cells, and endothelial cells relate to sarcoma development?

A list of the collaborations that were established among the participants during the workshop include:

1. Dr. Pancras Hogendorn (Dutch sarcoma pathologist/biologist) is collaborating with Dr. Darwin Prockop (Tulane University stem cell biologist) to develop standardized MSC preparations for use in models of chondrosarcoma development. The Tulane lab is to provide a preparation protocol, consultation, and perhaps a sample of MSC previously isolated.
2. Dr. Matt van de Rijn (Stanford cancer biologist working on molecular profiling of sarcomas) will be investigating deep vs. superficial fibroblasts in collaboration with Dr. Arthur Caplan (Case Western stem cell biologist) to further his research on connective tissue differentiation markers and stromal-cell involvement in sarcoma development. This sarcoma biologist is also to receive frozen tissue specimens for molecular profiling from three workshop participants.
3. Dr. Jonathan Fletcher (Harvard pediatric sarcoma biologist) will work with stem cell researchers from the University of Minnesota (Dr. Catherine Verfaillie) and Tulane University (Dr. Darwin Prockop) to develop MSC isolation techniques and share isolated stem cells for sarcoma-related research.
4. Dr. Richard Gorlick (Montefiore Children’s Hospital pediatric osteosarcoma biologist) has written an R01 grant to be submitted Spring 2005 (“Determination of the Molecular Pathogenesis of Osteosarcoma”). It contains significant MSC-related investigations developed through collaboration with Dr. Donald Phinney (Tulane stem cell biologist). Additionally, Dr. Gorlick and Dr. Phinney have exchanged databases of SAGE to explore gene expression profiles within bone sarcomas and bone-related MSC, respectively.
5. Dr. Michael Rudnicki (Ottawa stem cell biologist) has developed collaboration with Dr. Gerald Grosveld (St. Judes sarcoma biologist) regarding growth factors in the development of MSC and sarcomas.