Markus P. Ghadimi

Activated MET is a molecular prognosticator and potential therapeutic target for malignant peripheral nerve sheath tumors

Purpose: MET signaling has been suggested a potential role in malignant peripheral nerve sheath tumors (MPNST). Here, MET function and blockade were preclinically assessed. Experimental Design: Expression levels of MET, its ligand hepatocyte growth factor (HGF), and phosphorylated MET (pMET) were examined in a clinically annotated MPNST tissue microarray (TMA) incorporating univariable and multivariable statistical analyses. Human MPNST cells were studied in vitro and in vivo; Western blot (WB) and ELISA were used to evaluate MET and HGF expression, activation, and downstream signaling. Cell culture assays tested the impact of HGF-induced MET activation and anti-MET–specific siRNA inhibition on cell proliferation, migration, and invasion; in vivo gel-foam assays were used to evaluate angiogenesis. Cells stably transduced with anti-MET short hairpin RNA (shRNA) constructs were tested for growth and metastasis in severe combined immunodeficient (SCID) mice. The effect of the tyrosine kinase inhibitor XL184 (Exelixis) targeting MET/VEGFR2 (vascular endothelial growth factor receptor 2) on local and metastatic MPNST growth was examined in vivo. Results: All three markers were expressed in MPNST human samples; pMET expression was an independent prognosticator of poor patient outcome. Human MPNST cell lines expressed MET, HGF, and pMET. MET activation increased MPNST cell motility, invasion, angiogenesis, and induced matrix metalloproteinase-2 (MMP2) and VEGF expression; MET knockdown had inverse effects in vitro and markedly decreased local and metastatic growth in vivo. XL184 abrogated human MPNST xenograft growth and metastasis in SCID mice. Conclusions: Informative prognosticators and novel therapies are crucially needed to improve MPNST management and outcomes. We show an important role for MET in MPNST, supporting continued investigation of novel anti-MET therapies in this clinical context. Clin Cancer Res; 17(12); 3943–55. ©2011 AACR.

Involvement of the PI3K/Akt Pathway in Myxoid/Round Cell Liposarcoma

The molecular determinants involved in the progression of myxoid liposarcoma to increased cellularity/round cell change are poorly understood. We studied the PI3K/Akt pathway in myxoid and round cell liposarcomas using a tissue microarray composed of 165 tumors from 111 patients, and mutational analysis of PIK3CA in 44 cases. Activating PIK3CA mutations were found in 6/44 cases, 14%; mutations were more frequent in round cell vs myxoid tumors (5/15, 33% vs 1/29, 3%; P=0.013). Complete loss of PTEN, an alternative mechanism for PI3K/Akt activation, was found in 13/111 (12%) cases and was mutually exclusive with PIK3CA mutation. Strong IGF1R expression was demonstrated in 14/39 (36%) of round cell and 11/58 (19%) of myxoid tumors (P=0.062). Activation of the PI3K pathway was confirmed using immunohistochemical analysis for downstream targets phospho-S6 ribosomal protein and phospho-4EBP1. Phospho-4EBP1 was increased in round cell tumors compared with myxoid tumors (24/30, 80% vs 25/44, 57%; P=0.038) or tumors with treatment effect (10/24, 42%; P=0.02). Phospho-S6 was highly expressed in both myxoid and round cell tumors (29/47, 62% and 14/30, 47%, respectively; P=0.2). In tumors with PIK3CA mutation, any IGF1R expression, or loss of PTEN expression, phospho-4EBP1 was more frequently elevated compared with tumors without a known activating event in the PI3K pathway (55/72; 76% vs 3/8, 38%; P=0.033). These findings suggest that activation of the PI3K/Akt pathway via activating mutation of PIK3CA, loss of PTEN, or IGF1R expression have a role in round cell transformation. The PI3K/Akt pathway may therefore provide a therapeutic target in round cell liposarcoma.

Localized and metastatic myxoid/round cell liposarcoma: Clinical and molecular observations

Myxoid liposarcoma (MLPS), a disease especially of young adults with potential for local recurrence and metastasis, currently lacks solid prognostic factors and therapeutic targets. The authors of this report evaluated the natural history and outcome of patients with MLPS and commonly deregulated protein biomarkers.

Pleomorphic liposarcoma: clinical observations and molecular variables.

Pleomorphic liposarcoma (PLS) is a rare high‐grade sarcoma that has lipoblastic differentiation. In this study, the authors evaluated PLS natural history, patient outcomes, and commonly deregulated protein biomarkers.

Targeting the PI3K/mTOR axis, alone and in combination with autophagy blockade, for the treatment of malignant peripheral nerve sheath tumors

There is a critical need for efficacious therapeutic strategies to improve the outcome of patients afflicted by malignant peripheral nerve sheath tumors (MPNST). Multiple lines of evidence suggest a role for deregulated phosphoinositide 3-kinase (PI3K)/mTOR signaling in MPNST, making this axis an attractive target for therapeutic manipulation. On the basis of previous observations obtained from in vitro experimentation, here we aimed to assess the effects of PI3K/mTOR blockade on MPNST growth in vivo. The anti-MPNST impact of XL765, a dual PI3K/mTOR inhibitor currently being evaluated in human cancer clinical trials, was tested in two human MPNST xenograft models (STS26T and MPNST724) and an experimental model of pulmonary metastasis (STS26T). XL765 abrogated human MPNST local and metastatic growth in severe combined immunodeficient mice. Notably, this therapeutic approach failed to induce apoptosis in MPNST cells but rather resulted in marked productive autophagy. Importantly, genetic and pharmacologic autophagy blockade reversed apoptotic resistance and resulted in significant PI3K/mTOR inhibition-induced MPNST cell death. The addition of the autophagy inhibitor, chloroquine, to the therapeutic regimen of MPNST xenografts after pretreatment with XL765 resulted in superior antitumor effects as compared with either agent alone. Together, preclinical studies described here expand our previous findings and suggest that PI3K/mTOR inhibition alone and (most importantly) in combination with autophagy blockade may comprise a novel and efficacious therapy for patients harboring MPNST. Mol Cancer Ther; 11(8); 1758–69. ©2012 AACR.

Survivin Is a Viable Target for the Treatment of Malignant Peripheral Nerve Sheath Tumors

Purpose: To examine the role of survivin as a therapeutic target in preclinical models of human malignant peripheral nerve sheath tumors (MPNST) Experimental Design: Survivin protein expression levels and subcellular localization were examined immunohistochemically in an MPNST tissue microarray. Human MPNST cells were studied in vitro and in vivo; real-time PCR, Western blotting, and immunocytochemical analyses were used to evaluate survivin expression and localization activation. Cell culture assays were used to evaluate the impact of anti-survivin–specific siRNA inhibition on cell growth and cell-cycle progression and survival. The effect of the small-molecule survivin inhibitor YM155 on local and metastatic MPNST growth was examined in vivo. Results: Survivin was found to be highly expressed in human MPNSTs; enhanced cytoplasmic subcellular localization differentiated MPNSTs from their plexiform neurofibroma premalignant counterparts. Human MPNST cell lines exhibited survivin mRNA and protein overexpression; expression in both nuclear and cytoplasmic compartments was noted. Survivin knockdown abrogated MPNST cell growth, inducing G2 cell-cycle arrest and marked apoptosis. YM155 inhibited human MPNST xenograft growth and metastasis in severe combined immunodeficient (SCID) mice. Antitumor effects were more pronounced in fast-growing xenografts. Conclusions: Our studies show an important role for survivin in human MPNST biology. Patients with MPNSTs should be considered for ongoing or future clinical trials that evaluate anti-survivin therapeutic strategies. Most importantly, future investigations should evaluate additional pathways that can be targeted in combination with survivin for maximal synergistic anti-MPNST effects. Clin Cancer Res; 18(9); 2545–57. ©2012 AACR.

Combining EGFR and mTOR Blockade for the Treatment of Epithelioid Sarcoma

Purpose: Molecular deregulations underlying epithelioid sarcoma (ES) progression are poorly understood yet critically needed to develop new therapies. Epidermal growth factor receptor (EGFR) is overexpressed in ES; using preclinical models, we examined the ES EGFR role and assessed anti-ES EGFR blockade effects, alone and with mTOR inhibition. Experimental Design: EGFR and mTOR expression/activation was examined via tissue microarray (n = 27 human ES specimens; immunohistochemistry) and in human ES cell lines (Western blot and quantitative reverse transcriptase PCR). Cell proliferation, survival, migration, and invasion effects of EGFR and mTOR activation treated with erlotinib (anti-EGFR small-molecule inhibitor) alone and combined with rapamycin were assessed in cell culture assays. In vivo growth effects of erlotinib alone or with rapamycin were evaluated using severe combined immunodeficient mouse ES xenograft models. Results: EGFR was expressed and activated in ES specimens and cell lines. EGFR activation increased ES cell proliferation, motility, and invasion and induced cyclin D1, matrix metalloproteinase (MMP) 2, and MMP9 expression. EGFR blockade inhibited these processes and caused significant cytostatic ES growth inhibition in vivo. mTOR pathway activation at varying levels was identified in all tissue microarray–evaluable ES tissues; 88% of samples had no or reduced PTEN expression. Similarly, both ES cell lines showed enhanced mTOR activity; VAESBJ cells exhibited constitutive mTOR activation uncoupled from EGFR signaling. Most importantly, combined erlotinib/rapamycin resulted in synergistic anti-ES effects in vitro and induced superior tumor growth inhibition in vivo versus single agent administration. Conclusions: EGFR and mTOR signaling pathways are deregulated in ES. Preclinical ES model–derived insights suggest that combined inhibition of these targets might be beneficial, supporting evaluations in clinical trials. Clin Cancer Res; 17(18); 5901–12. ©2011 AACR.

The expression of c-Met pathway components in unclassified pleomorphic sarcoma/malignant fibrous histiocytoma (UPS/MFH): a tissue microarray study.

Lahat G, Zhang P, Zhu Q‐S, Torres K, Ghadimi M, Smith K D, Wang W‐L, Lazar A J & Lev D
(2011) Histopathology59, 556–561

Randomized comparative long-term survival study of endoscopic and thoracoscopic esophageal wall repair after NOTES mediastinoscopy in healthy and compromised animals.

BACKGROUND AND STUDY AIMS Natural orifice transluminal endoscopic surgery (NOTES) has not yet been widely adopted because of lack of suitable equipment and fear of possible serious complications, especially in the mediastinum. We compared endoscopic with thoracoscopic esophageal wall repair after full-thickness esophageal wall incision (FTEI) and NOTES mediastinoscopy in healthy versus compromised animals. METHODS After FTEI for mediastinoscopy, 24 pigs (12 healthy, 12 compromised) were randomly allocated to endoscopic or thoracoscopic repair (each arm of each group, n = 6). They were kept alive for 3 months after endoscopic closure with prototype T-anchor suturing or thoracoscopic repair. RESULTS FTEI and mediastinoscopy were uneventful in all as was the initial repair of the incision (mean repair times: thoracoscopic 65 +/- 3.2 minutes, endoscopic 52 +/- 5.1 minutes; P < 0.0005). Post procedure, all 12 healthy pigs thrived with no complications or deaths. Two compromised animals died during the preparation period, and had to be replaced. In the compromised group, during endoscopic repair, 2 / 6 pigs suffered from gastric reflux into esophagus and mediastinum; the repair was completed and the pigs kept alive; one subsequently died of mediastinitis, and in the other, autopsy showed a gastric abscess in the lower mediastinum. Regarding the compromised thoracoscopic subgroup, one animal died from mediastinitis and all had abscesses at or near the incision sites. CONCLUSION Transesophageal mediastinoscopy could be performed equally well as the transthoracic procedure, both in healthy and compromised animals. However, on follow-up, the compromised animals had worse outcomes, with more complications and two deaths (17 %), one in each arm.

Increased midkine expression correlates with desmoid tumour recurrence: a potential biomarker and therapeutic target.

Desmoid tumours (DTs) are soft tissue monoclonal neoplasms exhibiting a unique phenotype, consisting of aggressive local invasiveness without metastatic capacity. While DTs can infrequently occur as part of familial adenomatosis polyposis, most cases arise sporadically. Sporadic DTs harbour a high prevalence of CTNNB1 mutations and hence increased β‐catenin signalling. However, β‐catenin downstream transcriptional targets and other molecular deregulations operative in DT inception and progression are currently not well defined, contributing to the lack of sensitive molecular prognosticators and efficacious targeted therapeutic strategies. We compared the gene expression profiles of 14 sporadic DTs to those of five corresponding normal tissues and six solitary fibrous tumour specimens. A DT expression signature consisting of 636 up‐ and 119 down‐regulated genes highly enriched for extracellular matrix, cell adhesion and wound healing‐related proteins was generated. Furthermore, 98 (15%) of the over‐expressed genes were demonstrated to contain a TCF/LEF consensus binding site in their promoters, possibly heralding direct β‐catenin downstream targets relevant to DT. The protein products of three of the up‐regulated DT genes: ADAM12, MMP2 and midkine, were found to be commonly expressed in a large cohort of human DT samples assembled on a tissue microarray. Interestingly, enhanced midkine expression significantly correlated with a higher propensity and decreased time for primary DT recurrence (log‐rank p = 0.0025). Finally, midkine was found to enhance the migration and invasion of primary DT cell cultures. Taken together, these studies provide insights into potential DT molecular aberrations and novel β‐catenin transcriptional targets. Further studies to confirm the utility of midkine as a clinical DT molecular prognosticator and a potential therapeutic target are therefore warranted. Raw gene array data can be found at: http://smd.stanford.edu/ Copyright