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S1. MAPK dependence in UPS and HT-1080 cells

S7. Modeling UPS extravasation with zebrafish xenografts

S6. The role of RHAMM in UPS migration

S5. The role of RHAMM in UPS in proliferation and TGFB signaling

Supplementary Figure Legends 1-7

S3. YAP1 target expression in human and mouse UPS

S2. Colon carcinomas are insensitive to TGFB inhibition relative to sarcomas

Supplemental patient information from tissue microarray and additional quantitations.

This file contains additional data including material characterization, cell phenotype and migration, mechanotransduction pathway, proteases activity, tumor mechanics and human sarcoma cell migration.

Upregulation of collagen matrix crosslinking directly increases its ability to relieve stress under the constant strain imposed by solid tumor, a matrix property termed stress relaxation. However, it is unknown how rapid stress relaxation in response to increased strain impacts disease progression in a hypoxic environment. Previously, it has been demonstrated that hypoxia-induced expression of the crosslinker procollagen-lysine, 2-oxoglutarate 5-dioxygenase 2 (PLOD2), in sarcomas has resulted in increased lung metastasis. Here, we show that short stress relaxation times led to increased cell migration along a hypoxic gradient in 3D collagen matrices, and rapid stress relaxation upregulated PLOD2 expression via TGFβ-SMAD2 signaling, forming a feedback loop between hypoxia and the matrix. Inhibition of this pathway led to a decrease in migration along the hypoxic gradients. In vivo, sarcoma primed in a hypoxic matrix with short stress relaxation time enhanced collagen fiber size and tumor density and increased lung metastasis. High expression of PLOD2 correlated with decreased overall survival in patients with sarcoma. Using a patient-derived sarcoma cell line, we developed a predictive platform for future personalized studies and therapeutics. Overall, these data show that the interplay between hypoxia and matrix stress relaxation amplifies PLOD2, which in turn accelerates sarcoma cell motility and metastasis.Significance:These findings demonstrate that mechanical (stress relaxation) and chemical (hypoxia) properties of the tumor microenvironment jointly accelerate sarcoma motility and metastasis via increased expression of collagen matrix crosslinker PLOD2.

To date, no consistent oncogenic driver mutations have been identified in most adult soft tissue sarcomas; these tumors are thus generally insensitive to existing targeted therapies. Here we investigated alternate mechanisms underlying sarcomagenesis to identify potential therapeutic interventions. Undifferentiated pleomorphic sarcoma (UPS) is an aggressive tumor frequently found in skeletal muscle where deregulation of the Hippo pathway and aberrant stabilization of its transcriptional effector yes-associated protein 1 (YAP1) increases proliferation and tumorigenesis. However, the downstream mechanisms driving this deregulation are incompletely understood. Using autochthonous mouse models and whole genome analyses, we found that YAP1 was constitutively active in some sarcomas due to epigenetic silencing of its inhibitor angiomotin (AMOT). Epigenetic modulators vorinostat and JQ1 restored AMOT expression and wild-type Hippo pathway signaling, which induced a muscle differentiation program and inhibited sarcomagenesis. YAP1 promoted sarcomagenesis by inhibiting expression of ubiquitin-specific peptidase 31 (USP31), a newly identified upstream negative regulator of NFκB signaling. Combined treatment with epigenetic modulators effectively restored USP31 expression, resulting in decreased NFκB activity. Our findings highlight a key underlying molecular mechanism in UPS and demonstrate the potential impact of an epigenetic approach to sarcoma treatment.Significance: A new link between Hippo pathway signaling, NFκB, and epigenetic reprogramming is highlighted and has the potential for therapeutic intervention in soft tissue sarcomas. Cancer Res; 78(10); 2705–20. ©2018 AACR.

The concept of environmental sustainability, social responsibility, and good governance (ESG) is now well established in the corporate world and in for-profit organizations. However, it is not a concept that has reached medical and surgical association boardrooms in a meaningful way. It is important to define the concept of physician and corporate author expertise and objectives of ESG, provide a rationale for using ESG within orthopaedic organizations, and identify specific areas (primarily the "S" and the "G") where the American Academy of Orthopaedic Surgeons and other groups can align with this strategy.

Coaching is separate from mentoring, and can include life coaching, skills coaching, and behavior coaching. Life coaching can focus on purpose, work-life balance, well-being, and career path. Skills coaching encourages mastery and promotes autonomy. Behavior coaching may be mandated for a disruptive surgeon. Coaching has been shown to reduce burnout and promote well-being and can potentially advance a surgeon's career trajectory and leadership skills.

CD8+ T cell dysfunction is a critical barrier to anti-tumor immunity, but molecular mechanisms underlying the regulation of T cell dysfunction in solid tumors are diverse and complex. Extracellular matrix (ECM) composition facilitates solid tumor progression in part by inhibiting T cell migration/infiltration; however, the impact of individual ECM molecules on T cell function in the tumor microenvironment (TME) is virtually unknown. Moreover, upstream regulators of aberrant ECM deposition/organization in solid tumors are poorly defined. Therefore, we investigated the regulation and effects of ECM composition on CD8+ T cell function in undifferentiated pleomorphic sarcoma (UPS). This immunologically “hot” soft-tissue sarcoma exhibits durable responses to checkpoint therapy in some human patients, suggesting it may provide insights into strategies for optimizing T cell function and improving immunotherapy efficacy. Using an autochthonous model of UPS and data from multiple human patient cohorts, we discovered a multi-pronged mechanism wherein oncogene-induced remodeling of the TME promotes CD8+ T cell dysfunction, suppresses T cell-mediated cytolysis, and enhances immune evasion. Specifically, we observed that the transcriptional co-activator Yap1, which we previously linked to UPS progression, promotes the aberrant deposition of collagen VI in the UPS TME. In turn, collagen VI induces CD8+ T cell dysfunction by inhibiting T cell autophagic flux and remodeling fibrillar collagen architecture in the TME. Furthermore, collagen type I opposed ColVI in this setting, acting as tumor suppressor. Thus, our findings reveal that CD8+ T cell-mediated anti-tumor immunity in solid cancers is dependent upon oncogene-mediated ECM composition and remodeling in the TME.

Undifferentiated pleomorphic sarcoma (UPS), an aggressive subtype of soft-tissue sarcoma (STS), is exceedingly rare in humans and lacks effective, well-tolerated therapies. In contrast, STS are relatively common in canine companion animals; thus, incorporation of veterinary patients into studies of UPS offers an exciting opportunity to develop novel therapeutic strategies for this rare human disease. Genome-wide studies have demonstrated that UPS is characterized by aberrant patterns of DNA methylation. However, the mechanisms and impact of this epigenetic modification on UPS biology and clinical behavior are poorly understood. Leveraging cell lines and tissue specimens derived from human and canine patients, we discovered that the DNA methyltransferase DNMT3B is overexpressed in UPS relative to normal mesenchymal tissues and associated with a poor prognosis. Consistent with these findings, genetic DNMT3B depletion strongly inhibited UPS cell proliferation and tumor progression. However, existing hypomethylating agents, including the clinically approved drug 5-aza-2’-deoxycytidine and the DNMT3B-inhibiting tool compound nanaomycin A, were ineffective in UPS due to cellular uptake and toxicity issues. Thus, further development of DNMT3B-targeting strategies for these patients is critical.

Ewing sarcoma (EwS) is a highly aggressive tumor of bone and soft tissues that mostly affects children and adolescents. The pathognomonic oncofusion EWSR1::FLI1 transcription factor drives EwS by orchestrating an oncogenic transcription program through de novo enhancers. By integrative analysis of thousands of transcriptomes representing pan-cancer cell lines, primary cancers, metastasis, and normal tissues, we identify a 32-gene signature (ESS32 [Ewing Sarcoma Specific 32]) that stratifies EwS from pan-cancer. Among the ESS32, LOXHD1, encoding a stereociliary protein, is the most highly expressed gene through an alternative transcription start site. Deletion or silencing of EWSR1::FLI1 bound upstream de novo enhancer results in loss of the LOXHD1 short isoform, altering EWSR1::FLI1 and HIF1α pathway genes and resulting in decreased proliferation/invasion of EwS cells. These observations implicate LOXHD1 as a biomarker and a determinant of EwS metastasis and suggest new avenues for developing LOXHD1-targeted drugs or cellular therapies for this deadly disease.

CD8+ T cell dysfunction, characterized by reduced effector function, impaired proliferation, and inhibitory receptor upregulation, is a fundamental barrier to anti-tumor immunity. However, molecular mechanisms underlying the regulation of CD8+ T cell dysfunction in the tumor microenvironment (TME) are incompletely understood. In solid cancers, the extracellular matrix (ECM) facilitates tumor progression in part by inhibiting T cell migration/infiltration, but the impact of individual tumor-associated ECM molecules on T cell function remains unclear. Therefore, we investigated the regulation and impact of ECM composition on CD8+ T cell function in muscle-derived undifferentiated pleomorphic sarcoma (UPS). UPS exhibits durable responses to checkpoint therapy in a subset of human patients, potentially offering valuable insights into strategies for ameliorating T cell function and improving patient responses to immunotherapy. Using the autochthonous Kras G12D/+; Trp53 fl/fl (KP) murine model of UPS, we previously showed that deletion of the central Hippo pathway effector Yap1 (Kras G12D/+; Trp53 fl/fl; Yap1 fl/fl; KPY) suppressed UPS cell proliferation and tumor progression. Given the well-established role of Yap1 in mechanotransduction, we leveraged this system to investigate the effects of Yap1 on the ECM and CD8+ T cell function in UPS. We discovered that loss of UPS-cell intrinsic Yap1 reduced the proportion of dysfunctional CD8+ T cells in the TME and enhanced T cell cytolytic capacity. Yap1 loss also downregulated expression of multiple collagen genes in UPS cells and bulk tumors, including those that encode collagen type VI (ColVI). ColVI is a beaded microfilament collagen that binds to fibril-forming collagens in the ECM, such as collagen type I (ColI), and has been implicated in the pathogenesis of skeletal muscle myopathies. These data suggest that proper ColVI structure and function are critical for normal skeletal muscle physiology, with important implications for muscle-derived tumors such as UPS. Accordingly, COL6A1 was upregulated in human UPS relative to normal skeletal muscle, and inversely associated with UPS patient survival. Moreover, loss of UPS cell-intrinsic Col6a1 suppressed tumor progression, enhanced T cell cytolytic function, and attenuated CD8+ T cell exhaustion, phenocopying the effects of Yap1 deletion. Mechanistically, Yap1-mediated ColVI deposition promoted CD8+ T cell dysfunction by remodeling ColI networks in the UPS TME, and inhibiting T cell autophagic flux. Furthermore, ColI depletion dramatically increased tumor growth in an immunocompetent setting. Our findings reveal a novel role for UPS cell-intrinsic Yap1 in immune activation, and demonstrate that ColVI and ColI have opposing functions downstream of Yap in this context. These results underscore the need to systematically evaluate the roles of individual ECM components in the regulation of immune cell function, and implicate YAP1 and/or COLVI targeting as potential strategies for improving the efficacy of immunotherapy in human patients. Citation Format: Ashley M. Fuller, Hawley C. Pruitt, Hoogeun Song, Ying Liu, Ann Devine, Rohan S. Katti, Samir Devalaraja, Gabrielle E. Ciotti, Michael Gonzalez, Erik F. Williams, Ileana Murazzi, Nicolas Skuli, Hakon Hakonarson, Kristy Weber, Malay Haldar, Joseph A. Fraietta, Sharon Gerecht, T. S. Karin Eisinger-Mathason. Oncogene-induced matrix reorganization controls CD8+ T cell immunity in the UPS microenvironment [abstract]. In: Proceedings of the AACR Special Conference: Sarcomas; 2022 May 9-12; Montreal, QC, Canada. Philadelphia (PA): AACR; Clin Cancer Res 2022;28(18_Suppl):Abstract nr PR001.

This tumor quiz represents an interactive session where POSNA members are able to work through 9 clinical scenarios to challenge how they would address these problems. Associated with each scenario is an OITE-style question and multiple choice options that seek the most preferred answer from the clinician. In addition to the answer and follow-up radiographs, we have enlisted the opinions of three POSNA experts in oncology to provide an evidenced-based approach to thinking through each tumor problem.

The presence of discrimination, bullying, sexual harassment, and harassment (DBSH) in the healthcare workplace negatively affects the health and well-being of providers and is associated with poor mental health, low self-esteem, high levels of absenteeism, and low levels of productivity.The American Academy of Orthopaedic Surgeons (AAOS) developed and distributed a survey to a subset of AAOS members to assess the climate of workplace safety and overall workplace culture. Women and underrepresented minority (URM) AAOS members and an equal number of randomly selected non-URM men were invited to participate in the survey.Nine hundred twenty-seven of 5,638 (16.4%) members responded to the survey. Sixty-six percent of respondents reported experiencing DBSH behavior with specific exposures to DBSH of 79%, 55%, 47%, and 40%, respectively. Women (81%) were more likely than men (35%) to have experienced these behaviors. Fifty-eight percent of respondents reported that their workplaces were equipped to deal effectively with DBSH behaviors.DBSH behaviors occur in the orthopaedic workplace. More attention to these issues is necessary to ensure that all orthopaedic surgeons in training and in practice have a safe work environment that is inclusive, equitable, and health-promoting.N/A.

Women comprise approximately 50% of medical students; however, only 14% of current orthopaedic residents are women. There are many factors that contribute to the reluctance of female medical students to enter the field including limited exposure to musculoskeletal medicine during medical school, negative perception of the field, lack of female mentors, barriers to promotion, and acceptance by senior faculty. Diversity in orthopaedics is critical to provide culturally competent care. Two pipeline programs, the Perry Initiative and Nth Dimensions, have successful track records in increasing female and underrepresented minorities in orthopaedic surgery residency training. Recognizing and combating implicit bias in orthopaedics will improve recruitment, retention, promotion, and compensation of female orthopaedic surgeons. The purpose of this chapter is to provide an overview of the current status of women in orthopaedics, describe ways to improve diversity in the field, and make surgeons aware of how implicit bias can contribute to discrepancies seen in orthopaedic surgery, including pay scale inequities and women in leadership positions.

The evaluation of any orthopaedic condition often begins with obtaining plain radiographs. Fortuitously, plain radiographs provide surgeons with direct information on the biologic activity and, therefore, the aggressiveness of any bone lesion. More advanced imaging modalities may fail to elucidate the problem and may even obscure the diagnosis. The accurate interpretation of the aggressiveness of a bone lesion on plain radiographs is the first step in establishing a differential diagnosis for any bone lesion and, often, may result in a correct diagnosis without the need for additional imaging studies. A thorough understanding of the radiographic classification of bone lesions will allow surgeons to accurately diagnose and manage metabolic bone disease, benign bone lesions, and malignant bone lesions.

Fine-needle aspiration (FNA) is utilized in the diagnostic work-up of bone lesions in a number of institutions, either in isolation or in conjunction with core biopsy. We report our experience with FNA of bone-based lesions, including comparison of this approach with concurrent core biopsy specimens.Retrospective review over a 5-year period (2011-2015) revealed 233 cases of bone FNAs.The most commonly encountered diagnosis was malignant neoplasm (160 cases, 68.7%); within this group of malignancies, 103 cases (64.4%) represented metastatic carcinoma. Benign lesions were encountered infrequently (9 cases, 3.9%). While 37 cases (15.9%) revealed "no evidence of malignancy," 12 cases (5.2%) showed atypical findings, 3 cases (1.3%) demonstrated inflammatory conditions, and 12 aspiration biopsies were deemed nondiagnostic (5.2%). In 202 cases, concurrent core biopsies were performed following FNA and rapid on-site evaluation (ROSE). Comparison of the FNA and core biopsy diagnoses among malignant neoplasms revealed 19 diagnostic discrepancies, including 16 cases with a false-negative FNA (7.9% of all FNAs with concurrent core biopsy) and 3 cases with a false-negative core biopsy (1.5% of all cases with corresponding FNA).Our findings indicate that FNA of bone lesions is a useful diagnostic technique with high sensitivity, particularly when the cytologic findings are interpreted in conjunction with the core biopsy and pertinent clinical and radiologic findings. In addition, ROSE followed by open, dynamic communication with the performing radiologist leads to an extremely low rate of inadequate core biopsy specimens, resulting in optimal patient diagnosis and management. Diagn. Cytopathol. 2017;45:608-613. © 2017 Wiley Periodicals, Inc.

Peter J. Stern, MD, is Norman S. & Elizabeth C.A. Hill Professor and Chairman of Orthopaedic Surgery at the University of Cincinnati College of Medicine; Stephen Albanese, MD, is Professor and Chair of Orthopedic Surgery and Medical Director of Orthopedic Surgery Clinic at SUNY Upstate Medical University; Mathias Bostrom, MD, is Residency Program Director and Academic Director of Orthopaedics at Hospital for Special Surgery and Professor of Orthopaedic Surgery, Weill Cornell Medical College, Helen Hayes Hospital; Charles S. Day, MD, MBA, is Rabkin Fellow in Medical Education, Associate Professor of Orthopedic Surgery at Harvard Medical School, and Chief/Program Director of Hand and Upper Extremity Surgery at Beth Israel Deaconess Medical Center; Steven L. Frick, MD, is Chairman of Orthopedic Surgery at Nemours Children’s Hospital and Professor of Orthopedic Surgery at the University of Central Florida College of Medicine; William Hopkinson, MD, is Professor, Vice-Chair, and Program Director of Orthopaedic Surgery & Rehabilitation at Loyola University Stritch School of Medicine; Shepard Hurwitz, MD, is Executive Director of the American Board of Orthopaedic Surgery and Professor of Orthopaedics at the University of North Carolina; Keith Kenter, MD, is Director of the Orthopaedic Surgery Residency Program, Associate Professor of Orthopaedic Surgery, and Associate Professor of Physical Medicine and Rehabilitation at the University of Cincinnati College of Medicine; John S. Kirkpatrick, MD, is Professor and Chair of Orthopaedic Surgery and Rehabilitation and Program Director of Orthopaedic Surgery Residency at the University of Florida College of Medicine; J. L. Marsh, MD, is Program Director of Residency Training Program and Professor and Carroll B. Larson Chair of Orthopaedics and Rehabilitation at the University of Iowa; Anand M. Murthi, MD, is Chief of Shoulder and Elbow Surgery and Fellowship Director at MedStar Union Memorial Hospital; Lisa A. Taitsman, MD, MPH, is Associate Professor of Orthopaedics and Sports Medicine at the University of Washington; Brian C. Toolan, MD, is Associate Professor of Surgery and Director of the Residency Program of Orthopaedic Surgery at the University of Chicago Medicine; Kristy Weber, MD, is Virginia & William Percy Professor of Orthopaedic Surgery, Division Chief of Orthopaedic Oncology, and Director of the Sarcoma Center at Johns Hopkins School of Medicine; Rick W. Wright, MD, is Dr Asa C. Dorothy W. Jones Professor of Orthopaedic Surgery, Residency Program Director, and Co-Chief of Sports Medicine at Washington University School of Medicine; Pamela L. Derstine, PhD, MHPE, is Executive Director of the Review Committees for Colon and Rectal Surgery, Neurological Surgery, Orthopaedic Surgery, and Otolaryngology at the Accreditation Council for Graduate Medical Education; and Laura Edgar, EdD, CAE, is Senior Associate Director of Outcome Assessment at the Accreditation Council for Graduate Medical Education.

Malignant bone tumors represent a small percentage of cancers nationwide and also are much less common than malignant soft-tissue tumors. The rarity of the condition makes it imperative that orthopaedic surgeons in nononcologic practices are able to recognize the symptoms that suggest a possible bony malignancy to avoid inappropriate or delayed treatment. The most common primary malignant bone tumors, osteosarcoma and Ewing's sarcoma, occur in childhood. Chondrosarcoma occurs more frequently in older adults. Rare tumors such as chordoma and adamantinoma have anatomic predilections for the sacrum and tibia, respectively. The primary symptom of a patient with a malignant bone tumor is pain, which often occurs at rest or at night. There are also characteristic findings on physical examination such as swelling or decreased joint range of motion. Patients with a likely malignancy require thorough staging to determine the extent of disease and a well-planned biopsy for accurate diagnosis. The biopsy can be an image-guided needle biopsy or an open incisional biopsy. Knowledge of specific tumor characteristics and treatment options for osteosarcoma, Ewing's sarcoma, chondrosarcoma, malignant fibrous histiocytoma, chordoma, and adamantinoma is important. Patients with osteosarcoma and resectable Ewing's sarcoma are treated with chemotherapy followed by surgical resection. Secondary sarcomas can occur in previously benign bone lesions and require aggressive treatment. Specific techniques are available for the resection of malignant bone tumors from the upper extremities, lower extremities, pelvis, and spine. Reconstruction options include the use of allografts, megaprostheses, and vascularized autografts. There has been a trend toward more prosthetic reconstructions because of early complications with allografts. The care of patients with primary malignant bone tumors requires a multidisciplinary approach to treatment. The orthopaedic oncologist is a vital member of a team composed of musculoskeletal radiologists and pathologists, radiation oncologists, medical and pediatric oncologists, and microvascular surgeons.

We report six children with pigmented villonodular synovitis. they ranged in age from seven to fifteen years. In four patients, the knee was involved. One patient had involvement of the ankle, and one had diffuse involvement along a metacarpal. In five cases, the diagnosis was not suspected clinically or radiographically, and the delay in making the correct diagnosis was as long as two years. clinical diagnosis in these five patients was usually bacterial synovitis or juvenile rheumatoid arthritis. We feel that the diagnoses of pigmented villonodular synovitis should be considered in any child with chronic joint effusion.

Unicameral bone cysts of the pelvis are extremely rare. This study summarizes the clinical, radiologic and pathologic features of 16 cases. Patients ranged in age from nine to 69. Most lesions were in the anterior portion of the iliac wing; many appeared to be related to an open iliac crest apophysis. This suggests that the pathogenesis of unicameral bone cysts in this portion of the ilium is similar to that seen in the proximal humerus and the proximal femur. The correct diagnosis was made preoperatively in only five cases. This indicates that, although they are well documented, unicameral bone cysts of the pelvis remain a diagnostic problem. Patients received a spectrum of treatments from curettage to observation. There appeared to be no difference in the outcome after any form of treatment. Therefore, unicameral bone cysts of the pelvis can be managed conservatively. The choice to manage patients conservatively depends on making the correct diagnosis based on clinical history and imaging. The most effective imaging is a combination of plain radiographs, computed tomography (CT) and magnetic resonance imaging (MRI).

Tumoral calcinosis is the deposition of calcium crystals and salts in the periarticular soft tissues. It commonly is seen as a complication of renal dialysis or in patients with a hereditary disposition. Occasionally, it is seen as an isolated condition with no known cause. Tumoral calcinosis usually affects adults and rarely, children. This disorder is extremely uncommon in infants. Only 13 cases have been reported. In this study three additional infants with tumoral calcinosis are reported, bringing the total to 16 cases. These 16 cases provide the opportunity to compare tumoral calcinosis in infants (younger than 18 months) with the disease in older patients. Although histologic and radiologic features in infants and adults are identical, some clinical features differ. In almost all infants, the disease develops without any predisposing factors, such as a family history. Surgical removal of lesions in infants is curative. By contrast, lesions in adults tend to recur after surgery.

The melanoma cellular adhesion molecule, also known as MUC18, is highly expressed on several tumors, including bone sarcomas. The level of MUC18 expression has been found to correlate directly with tumor progression and metastatic potential. These observations have established MUC18 as a candidate mediator of tumor growth and metastasis, and suggest that blockade of MUC18 might be a potential target for immunotherapy against several MUC18-expressing tumors, including human bone sarcomas.To investigate whether blockade of MUC18 might be a potential target for immunotherapy against osteosarcoma, we have recently developed a fully human anti-MUC18 antibody, ABX-MA1. We studied the effect of ABX-MA1 on growth, adhesion, invasion, and metastasis of human osteosaroma cells both in vitro and in vivo.MUC18 was widely expressed on both osteosarcoma and Ewing's sarcoma cells. ABX-MA1 had no effect on the proliferation of osteosarcoma cells in vitro, nor did it significantly inhibit the growth of KRIB human osteosarcoma cells when they were orthotopically implanted into the tibias of nude mice. However, after 6 weeks, significantly fewer ABX-MA1-treated mice developed spontaneous pulmonary metastases than did IgG-treated control mice. Additionally, ABX-MA1 decreased the invasion of osteosarcoma cells through Matrigel-coated filters and disrupted homotypic adhesion between osteosarcoma cells and their heterotypic interaction with human vascular endothelial cells.Our findings demonstrate that MUC18 plays a central role in the metastasis of osteosarcoma and suggest that targeted inhibition of this antigen by ABX-MA1 may be a novel immunotherapeutic approach in the management of this tumor.

Osteosarcoma is an aggressive primary bone cancer characterized by expression of platelet-derived growth factor (PDGF) and its cognate receptor. Coexpression of the growth factor and receptor suggests their role in autocrine or paracrine growth mechanisms. It has been reported previously that STI571 has specific activity in inhibiting select tyrosine kinase receptors, including PDGF and c-Kit. Osteosarcomas express low levels of c-Kit but abundant levels of PDGF receptor (PDGFR).To investigate the potential of STI571 as therapy for osteosarcoma, we studied its effects on PDGF-mediated cell growth in vitro and in an in vivo mouse model.PDGF acted as a potent mitogen in a dose-dependent manner in two osteosarcoma cell lines. STI571 (1.0 micro M) inhibited both PDGFR-alpha and PDGFR-beta phosphorylation and the downstream phosphorylation targets extracellular signal-regulated kinase and Akt. STI571 also inhibited PDGF-mediated growth and induced apoptosis in vitro as determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and terminal deoxynucleotidyl transferase-mediated nick end labeling staining. To study the effect of STI571 alone or in combination with Taxol in an in vivo model, an osteosarcoma cell line (KRIB) was transplanted into the tibia of athymic nude mice. Mice were treated with STI571 (50 mg/kg p.o. q M-F), Taxol (8 mg/kg i.p. weekly), or STI571 plus Taxol for 6 weeks. There was no significant difference in tumor size between treatment and control mice. Aberrant signaling pathways downstream of the PDGFR in the v-Ki-ras oncogene-transformed KRIB cell line may in part explain this finding.Our data demonstrate that STI571 inhibits PDGF-mediated growth and leads to apoptosis of osteosarcoma cells in vitro by selective inhibition of the PDGFR tyrosine kinase. The effectiveness of STI571 in our studies suggests targeting of PDGFRs as a novel treatment for osteosarcoma.

Somatosensory (SEPs) and neurogenic-motor evoked potentials (NMEPs) were elicited from 16 hogs and two humans before, during, and after spinal cordotomy, dorsal, or ventral root rhizotomy. Results indicated that SEPs appear to be insensitive to the effects of motor tract lesioning in hogs and humans. In every case of motor paraplegia, SEPs remained unchanged in the presence of abnormal ischiatic/sciatic NMEPs. These results suggest that SEPs are not adequately sensitive to the functional status of the motor system in hogs and humans. Ischiatic/sciatic NMEPs remained unchanged after sensory tract lesioning, suggesting that these NMEPs are insensitive to the functional status of the sensory system. These results suggest that SEPs and NMEPs should be used in combination when monitoring spinal cord function during surgeries that place that structure at risk.