Human Soft Tissue Sarcoma Cell Lines Research Articles

Oncolytic virotherapy promotes radiosensitivity in soft tissue sarcoma by suppressing anti-apoptotic MCL1 expression.

Soft tissue sarcoma (STS) is a rare cancer that develops from soft tissues in any part of the body. Despite major advances in the treatment of STS, patients are often refractory to conventional radiotherapy, leading to poor prognosis. Enhancement of sensitivity to radiotherapy would therefore improve the clinical outcome of STS patients. We previously revealed that the tumor-specific, replication-competent oncolytic adenovirus OBP-301 kills human sarcoma cells. In this study, we investigated the radiosensitizing effect of OBP-301 in human STS cells. The in vitro antitumor effect of OBP-301 and ionizing radiation in monotherapy or combination therapy was assessed using highly radiosensitive (RD-ES and SK-ES-1) and moderately radiosensitive (HT1080 and NMS-2) STS cell lines. The expression of markers for apoptosis and DNA damage were evaluated in STS cells after treatment. The therapeutic potential of combination therapy was further analyzed using SK-ES-1 and HT1080 cells in subcutaneous xenograft tumor models. The combination of OBP-301 and ionizing radiation showed a synergistic antitumor effect in all human STS cell lines tested, including those that show different radiosensitivity. OBP-301 was found to enhance irradiation-induced apoptosis and DNA damage via suppression of anti-apoptotic myeloid cell leukemia 1 (MCL1), which was expressed at higher levels in moderately radiosensitive cell lines. The combination of OBP-301 and ionizing radiation showed a more profound antitumor effect compared to monotherapy in SK-ES-1 (highly radiosensitive) and HT1080 (moderately radiosensitive) subcutaneous xenograft tumors. OBP-301 is a promising antitumor reagent to improve the therapeutic potential of radiotherapy by increasing radiation-induced apoptosis in STS.

The Oncolytic Activity of Myxoma Virus against Soft Tissue Sarcoma Is Mediated by the Overexpression of Ribonucleotide Reductase.

Background:Myxoma virus (MYXV) is an oncolytic poxvirus that lacks the gene for 1 of the subunits of ribonucleotide reductase (RR), a crucial DNA synthesis and repair enzyme. The overexpression of RR has been implicated in the invasiveness of several cancers, including soft tissue sarcomas (STS). The purpose of the study was to investigate the oncolytic efficacy of MYXV in STS with different levels of RR expression.Methods:The oncolytic effect of recombinant MYXV was evaluated in 4 human STS cell lines, LS141 (a dedifferentiated liposarcoma), DDLS8817 (a dedifferentiated liposarcoma), RDD2213 (recurrent dedifferentiated liposarcoma), and HSSYII (a synovial sarcoma) using infectivity and cytotoxicity assays. Following the overexpression of RRM2 by cDNA transfection and silencing of RRM2 by siRRM2 in these STS cell lines, the RRM2 expression levels were analyzed by Western blot.Results:We observed a direct correlation between viral oncolysis and RRM2 mRNA levels (R = 0.96) in STS. Higher RRM2 expression was associated with a more robust cell kill. Silencing the RRM2 gene led to significantly greater cell survival (80%) compared with the control group (P = .003), whereas overexpression of the RRM2 increased viral oncolysis by 33% (P < .001).Conclusions:Our results show that the oncolytic effects of MYXV correlate directly with RR expression levels and are enhanced in STS cell lines with naturally occurring or artificially induced high expression levels of RR. Myxoma virus holds promise in the treatment of advanced soft tissue cancer, especially in tumors overexpressing RR.

Abstract 5188: Molecular radiosensitization in soft tissue sarcomas by telomerase-specific oncolytic adenovirus

Abstract INTRODUCTION:Treatment options for soft tissue sarcoma (STS) include surgical resection and adjuvant chemotherapy and radiotherapy. Despite the development of combined modality treatments in recent years, a significant proportion of patients with sarcomas respond poorly to adjuvant therapy, leading to local recurrence or distant metastasis. Therefore, there is an urgent need to develop novel therapeutic strategies for improvement of patient prognoses. We previously reported the therapeutic potential of OBP-301, a telomerase-specific oncolytic adenoviruses, and OBP-702, an armed OBP-301 expressing the wild-type p53 tumor suppressor gene against bone and soft tissue sarcoma cells. Furthermore, the synergistic anti-tumor effect of OBP-301 in combination with radiation has been observed. While OBP-702 suppressed the viability of OBP-301-sensitive and -resistant osteosarcoma cells more efficiently, the combination effect of OBP-702 and radiotherapy has been unknown. In this study, we investigated the radiosensitizing effect of OBP-702 against human STS cells. METHODS:We used four human STS cell lines, HT1080 (fibrosarcoma), NMS-2 (malignant peripheral nerve sheath tumor), and SYO-1 (synovial sarcoma). Cells were irradiated 24 h after infection with OBP-301 and OBP-702, and cell viability was assessed by XTT assay 4 days after irradiation. Combined effect of radiation with OBP-301 and OBP-702 was analyzed with the CalcuSyn software (BioSoft). These cells were also analyzed for apoptosis and DNA damage using Western blot analysis. RESULTS:While OBP-301 and OBP-702 showed anti-tumor effect for STS cell lines respectively, HT1080 and NMS-2 were highly resistant to radiation. When combined with radiation, not only OBP-301 but also OBP-702 enhanced the inhibitory anti-tumor effect in all STS cell lines. The calculation of combination index demonstrated additive or synergistic anti-tumor effect in combination therapy. Further analysis revealed that OBP-301 and OBP-702 increased radiation-induced apoptosis in STS cells. Notably, the radio-sensitizing effect of OBP-702 was associated with increase of p53 expression and interruption of anti-apoptotic myeloid cell leukemia 1 (MCL1) expression. DISCUSSION:Our study demonstrated that OBP-702 had much stronger anti-tumor effect compared to OBP-301, and sensitized radiotherapy to various types of osteosarcoma cell lines. Currently, the clinical trial of OBP-301 is performed, and preclinically OBP-702 accumulates good therapeutic results in various tumors. Thus, OBP-702 may provide a novel treatment strategy for STSs and wide application of radiotherapy for localized as well as advanced STSs. Citation Format: Tadashi Komatsubara, Toshinori Omori, Hiroshi Tazawa, Kazuhisa Sugiu, Yusuke Mochizuki, Yasuaki Yamakawa, Shuhei Osaki, Joe Hasei, Tomohiro Fujiwara, Toshiyuki Kunisada, Yasuo Urata, Tsoshifumi Ozaki, Toshiyoshi Fujiwara. Molecular radiosensitization in soft tissue sarcomas by telomerase-specific oncolytic adenovirus [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5188. doi:10.1158/1538-7445.AM2017-5188

Curcumin and Viscum album Extract Decrease Proliferation and Cell Viability of Soft-Tissue Sarcoma Cells: An In Vitro Analysis of Eight Cell Lines Using Real-Time Monitoring and Colorimetric Assays

ABSTRACTBackground: The cytostatic effects of the polyphenol curcumin and Viscum album extract (VAE) were assessed in soft-tissue sarcoma (STS) cells. Methods: Eight human STS cell lines were used: fibrosarcoma (HT1080), liposarcoma (SW872, T778, MLS-402), synovial sarcoma (SW982, SYO1, 1273), and malignant fibrous histiocytoma (U2197). Primary human fibroblasts served as control cells. Cell proliferation, viability, and cell index (CI) were analyzed by BrdU assay, MTT assay, and real-time cell analysis (RTCA). Results: As indicated by BrdU and MTT, curcumin significantly decreased the cell proliferation of five cell lines (HT1080, SW872, SYO1, 1273, and U2197) and the viability of two cell lines (SW872 and SW982). VAE led to significant decreases of proliferation in eight cell lines (HT1080, SW872, T778, MLS-402, SW982, SYO1, 1293, and U2197) and reduced viability in seven STS lines (HT1080, SW872, T778, MLS-402, SW982, SYO1, and 1273). As indicated by RTCA for 160 h, curcumin decreased the CI of all synovial sarcoma cell lines as well as T778 and HT1080. VAE diminished the CI in most of the synovial sarcoma (SW982, SYO1) and liposarcoma (SW872, T778) cell lines as well as HT1080. Primary fibroblasts were not affected adversely by the two compounds in RTCA. Conclusion: Curcumin and VAE can inhibit the proliferation and viability of STS cells.

Anti‑proliferative activity of epigallocatechin‑3‑gallate and silibinin on soft tissue sarcoma cells.

Disseminated soft tissue sarcomas (STS) present a therapeutic dilemma. The first-line cytostatic doxorubicin demonstrates a response rate of 30% and is not suitable for elderly patients with underlying cardiac disease, due to its cardiotoxicity. Well-tolerated alternative treatment options, particularly in palliative situations, are rare. Therefore, the present study assessed the anti-proliferative effects of the natural compounds epigallocatechin-3-gallate (EGCG), silibinin and noscapine on STS cells. A total of eight different human STS cell lines were used in the study: Fibrosarcoma (HT1080), liposarcoma (SW872, T778 and MLS-402), synovial sarcoma (SW982, SYO1 and 1273) and pleomorphic sarcoma (U2197). Cell proliferation and viability were analysed by 5-bromo-2′-deoxyuridine and MTT assays and real-time cell analysis (RTCA). RTCA indicated that noscapine did not exhibit any inhibitory effects. By contrast, EGCG decreased proliferation and viability of all cell lines except for the 1273 synovial sarcoma cell line. Silibinin exhibited anti-proliferative effects on all synovial sarcoma, liposarcoma and fibrosarcoma cell lines. Liposarcoma cell lines responded particularly well to EGCG while synovial sarcoma cell lines were more sensitive to silibinin. In conclusion, the green tea polyphenol EGCG and the natural flavonoid silibinin from milk thistle suppressed the proliferation and viability of liposarcoma, synovial sarcoma and fibrosarcoma cells. These compounds are therefore potential candidates as mild therapeutic options for patients that are not suitable for doxorubicin-based chemotherapy and require palliative treatment. The findings from the present study provide evidence to support in vivo trials assessing the effect of these natural compounds on solid sarcomas.

Abstract 344: Antimitotic effect and complex of nonmitotic effect on tumor biology of eribulin mesilate in soft tissue sarcoma model

Abstract Background and objectives: Eribulin mesilate (Eribulin), a first-in-class halichondrin B-based microtubule dynamics inhibitor, has been shown to have novel mechanism of actions (reversion of epithelial-mesenchymal transition of tumor cell and promotion of vascular remodeling) beyond its established antimitotic activity in breast cancer models, leading to decrease of tumor metastatic potency. Recently, eribulin showed trends towards greater overall survival compared to Dacarbazine in subjects with leiomyosarcoma and liposarcoma patients in phase 3 trial. The objective of this study was to investigate the effect of eribulin on tumor cell proliferation of soft tissue sarcoma (STS). Furthermore, the effects of eribulin on morphology and gene expression of differentiation markers against STS and tumor blood perfusion in a leiomyosarcoma xenograft model were examined. Methods: Anti-proliferation activity of eribulin was examined in 6 human STS cell lines. Anti-tumor activity of eribulin was examined in xenografts of A-673 (Ewing's sarcoma), SK-LMS-1 (leiomyosarcoma), SW 872 (liposarcoma), and HT-1080 (fibrosarcoma) at several doses. To analyze the effect of eribulin on in vitro morphological change, 3 human STS cell lines were treated with eribulin at 1, 3, and 10 nmol/L for 7 days. Gene expression change was analyzed by microarray and differentiation marker genes in 2 cell lines were confirmed by qPCR analysis. For tumor blood perfusion analysis, eribulin was administered at doses of 0.38, 0.75, and 1.5 mg/kg one shot in SK-LMS-1 xenografts, and tumor blood perfusion was calculated as Hoechst-positive areas in tumor cryosections 5 days after the administration. Results: Eribulin showed anti-proliferation activity in vitro against all 6 cell lines in a dose dependent manner with 50% inhibitory concentration values of around 1 nmol/L. Eribulin showed significant antitumor activity against 4 xenografts in a dose dependent manner. Eribulin treatment for 7 days induced apparent morphological change in 3 cell lines. Of these, expression level of smooth muscle differentiation marker gene CNN1 was 7.1-fold upregulated in SK-UT-1 and adipocyte differentiation marker genes MYLK, C/EBPβ, and KIF23 were 1.9-, 1.4-, and 1.3-fold upregulated in SW 872, respectively, by 10 nmol/L treatment compared to vehicle control. In addition, eribulin significantly enhanced tumor blood perfusion compared to vehicle control 5 days after the administration in SK-LMS-1 xenografts at all doses.Conclusions: Eribulin showed anti-proliferation activity against all of STS cell lines we tested in vitro and in vivo. Furthermore, eribulin might cause differentiation of STS cells and remodeling of tumor vasculature to enhance tumor blood perfusion. These data supported that eribulin showed mitotic effect and non-mitotic effect, which may decrease tumor metastatic potency in STS, as well in breast cancer. Citation Format: Satoshi Kawano, Makoto Asano, Yusuke Adachi, Junji Matsui. Antimitotic effect and complex of nonmitotic effect on tumor biology of eribulin mesilate in soft tissue sarcoma model. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 344.

Sesquiterpene Lactones Downregulate G2/M Cell Cycle Regulator Proteins and Affect the Invasive Potential of Human Soft Tissue Sarcoma Cells

Soft tissue sarcomas (STS) represent a rare group of malignant tumors that frequently exhibit chemotherapeutic resistance and increased metastatic potential. Many studies have demonstrated the great potential of plant-derived agents in the treatment of various malignant entities. The present study investigates the effects of the sesquiterpene lactones costunolide and dehydrocostus lactone on cell cycle, MMP expression, and invasive potential of three human STS cell lines of various origins. Both compounds reduced cell proliferation in a time- and dose-dependent manner. Dehydrocostus lactone significantly inhibited cell proliferation, arrested the cells at the G2/M interface and caused a decrease in the expression of the cyclin-dependent kinase CDK2 and the cyclin-dependent kinase inhibitor p27Kip1. In addition, accumulation of cells at the G2/M phase transition interface resulted in a significant decrease in cdc2 (CDK1) together with cyclin B1. Costunolide had no effect on the cell cycle. Based on the fact that STS tend to form daughter cell nests and metastasize, the expression levels of matrix metalloproteinases (MMPs), which play a crucial role in extracellular matrix degradation and metastasis, were investigated by Luminex® technology and real-time RT-PCR. In the presence of costunolide, MMP-2 and -9 levels were significantly increased in SW-982 and TE-671 cells. Dehydrocostus lactone treatment significantly reduced MMP-2 and -9 expression in TE-671 cells, but increased MMP-9 level in SW-982 cells. In addition, the invasion potential was significantly reduced after treatment with both sesquiterpene lactones as investigated by the HTS FluoroBlock™ insert system.

Effects of TRAIL and taurolidine on apoptosis and proliferation in human rhabdomyosarcoma, leiomyosarcoma and epithelioid cell sarcoma

Soft tissue sarcomas (STS) are a heterogeneous group of malignant tumours representing 1% of all malignancies in adults. Therapy for STS should be individualised and multimodal, but complete surgical resection with clear margins remains the mainstay of therapy. Disseminated soft tissue sarcoma still represents a therapeutic dilemma. Commonly used chemotherapeutic agents such as doxorubicin and ifosfamide have proven to be effective in fewer than 30% in these cases. Therefore, we tested the apoptotic and anti-proliferative in vitro effects of TNF-related apoptosis-inducing ligand (TRAIL) and taurolidine (TRD) on rhabdomyosarcoma (A-204), leiomyosarcoma (SK-LMS-1) and epithelioid cell sarcoma (VA-ES-BJ) cell lines. Viability, apoptosis and necrosis were quantified by FACS analysis (propidium iodide/Annexin V staining). Gene expression was analysed by DNA microarrays and the results validated for selected genes by rtPCR. Protein level changes were documented by western blot analysis. Cell proliferation was analysed by BrdU ELISA assay. The single substances TRAIL and TRD significantly induced apoptotic cell death and decreased proliferation in rhabdomyosarcoma and epithelioid cell sarcoma cells. The combined use of TRAIL and TRD resulted in a synergistic apoptotic effect in all three cell lines, especially in rhabdomyosarcoma cells leaving 18% viable cells after 48 h of incubation (p<0.05). Analysis of the differentially regulated genes revealed that TRD and TRAIL influence apoptotic pathways, including the TNF-receptor associated and the mitochondrial pathway. Microarray analysis revealed remarkable expression changes in a variety of genes, which are involved in different apoptotic pathways and cross talk to other pathways at multiple levels. This in vitro study demonstrates that TRAIL and TRD synergise in inducing apoptosis and inhibiting proliferation in different human STS cell lines. Effects on gene expression differ relevantly in the sarcoma entities. These results provide experimental support for in vivo trials assessing the effect of TRAIL and TRD in STS and sustain the approach of individualized therapy.

Abstract 2665: NBTXR3 hafnium oxide nanoparticle activated by ionizing radiation demonstrates marked radio-enhancement and antitumor effect via high energy deposit in human soft tissue sarcoma

Abstract Local and systemic control of Soft Tissue Sarcoma (STS) remains a clinical challenge. Radiation therapy is part of the standard of care of STS. The narrowness of its therapeutic window represents the main concern for different clinical settings. Thus, local delivery of radiation doses is critical to ensure optimal benefit-risk ratio. NBTXR3, biocompatible hafnium oxide nanoparticles were designed as therapeutics to be activated by ionizing radiation to achieve tumor control by enhancement of local energy deposition. A global non clinical program was implemented in mesenchymal tumor models. In vitro clonogenic survival assays were performed in two human fibrosarcoma cell lines (HT1080 and Hs913t) and a human liposarcoma cell line (SW872) to evaluate the cellular response to radiation-activated NBTXR3 at increasing concentrations. A marked radio-enhancement was observed in human STS cell lines with dose enhancement factors estimated at 4 Gy ranging from 1.48 up to 5.36 according to NBTXR3 concentrations. Further, in human immortalized MRC5V1 fibroblasts, no significant decrease in clonogenic surviving fraction was observed upon activation of NBTXR3 under similar conditions suggesting a differential radiation response between fibroblasts and fibrosarcoma, liposarcoma cell lines. This differential radiation response was further confirmed between HT1080 fibrosarcoma cell line and MRC5V1 fibroblasts upon activation of NBTXR3 at increasing concentration using high energy gamma-rays. Mechanistic studies have demonstrated in HT1080 cells that NBTXR3 activation induces an increase of 53BP1 foci associated with more “complex” DNA damages than ionizing radiation alone. The level of unrepaired DNA damages was also estimated by flow cytometry analysis showing a higher level of gamma-H2AX at 48h following NBTXR3 activation than after radiotherapy alone. DNA fragmentation and Annexin V staining have demonstrated that these unrepaired DNA damages upon NBTXR3 activation induces apoptosis in HT1080 fibrosarcoma cells. In vivo, tolerance and tumor growth delay were investigated in two human xenografted tumor models, HT1080 fibrosarcoma and a patient derived liposarcoma LPS80T3 (poorly differentiated grade 3). No toxicity related to NBTXR3 was reported. In both models, a significant advantage was demonstrated in terms of tumor growth inhibition and survival when compared to radiation therapy alone. These findings establish a novel approach of treatment, which may be applied to a broad range of tumors. Therefore, incrementing the amount of energy deposited within the tumor through the activation of NBTXR3 crystalline nanoparticles constitutes a revolutionary approach for future clinical investigation. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2665. doi:10.1158/1538-7445.AM2011-2665

Gemcitabine-Mediated Radiosensitization of Human Soft Tissue Sarcoma

Local and systemic control of soft tissue sarcoma (STS) remains a clinical challenge, particularly for retroperitoneal, deep truncal, or advanced extremity disease. 2',2'-Difluoro-2'-deoxycytidine (gemcitabine) is a potent radiosensitizer in many tumor types, but it has not been studied in human STS. The purpose of this study was to determine the radiosensitizing potential of gemcitabine in preclinical models of human STS. The in vitro radiosensitizing activity of gemcitabine was assessed with clonogenic survival assay on three human STS cell lines: SK-LMS-1 (leiomyosarcoma), SW-872 (liposarcoma), and HT-1080 (fibrosarcoma). Cell cycle distribution was determined using dual-channel flow cytometry. The in vivo radiosensitizing activity of gemcitabine was assessed with subcutaneous SK-LMS-1 nude mice xenografts. Tumor-bearing mice were treated with concurrent weekly gemcitabine and fractionated daily radiotherapy (RT) (2 Gy daily) for 3 weeks (a total dose of 30 Gy). The 50% inhibitory concentration (IC(50)) of gemcitabine for the human STS cell lines ranged from 10 to 1000 nM. Significant in vitro radiosensitization was demonstrated in all three human STS cell lines using gemcitabine concentrations at and below the IC(50). Maximal radiosensitization was associated with accumulation of cells in early S-phase. SK-LMS-1 xenografts displayed significant tumor growth delay with combined gemcitabine and RT compared to either treatment alone. Treatment related toxicity was greatest in the gemcitabine plus RT arm, but remained at an acceptable level. Gemcitabine is a potent radiosensitizer in preclinical models of human STS. Clinical trials combining gemcitabine and RT in human STS are warranted.

Altered expression of urokinase-type plasminogen activator and plasminogen activator inhibitor in high-risk soft tissue sarcomas

In recent years, classification of soft-tissue sarcomas (STS) has improved with cytogenetic analyses, but their clinical behavior is still not easily predictable. The aim of this study was to detect alterations in the urokinase-type plasminogen system, involved in tumor growth and invasion, by comparing mRNA levels of its components with those of paired normal tissues, and relating them with patient clinical course. Real-time PCR was performed on human STS cell lines and tissues from highly malignant STS, including leiomyosarcomas and malignant fibrous histiocytomas, to evaluate the expression of urokinase-type plasminogen activator (uPA), uPA receptor (uPAR) and plasminogen activator inhibitor-1 (PAI-1). Immunohistochemistry of gene products was also performed. Median mRNA values of all genes studied were higher in tumors than in paired normal tissues. In agreement with data on STS cell lines, significant up-regulation for uPA and PAI-1 genes compared to reference values was seen. Moreover, different levels of expression were related to histotype and metastatic phenotype. There was accordance between uPA mRNA and protein expression, while immunodetection of PAI-1 product was weak and scattered. Clearly, the controversial role of PAI-1 protein requires further biological analyses, but evident involvement of uPA/PAI-1 gene overexpression in STS malignancy may highlight a molecular defect useful in discriminating STS high-risk patients.

Rad51 overexpression contributes to chemoresistance in human soft tissue sarcoma cells: a role for p53/activator protein 2 transcriptional regulation

We investigated whether Rad51 overexpression plays a role in soft tissue sarcoma (STS) chemoresistance as well as the regulatory mechanisms underlying its expression. The studies reported here show that Rad51 protein is overexpressed in a large panel of human STS specimens. Human STS cell lines showed increased Rad51 protein expression, as was also observed in nude rat STS xenografts. STS cells treated with doxorubicin exhibited up-regulation of Rad51 protein while arrested in the S-G(2) phase of the cell cycle. Treatment with anti-Rad51 small interfering RNA decreased Rad51 protein expression and increased chemosensitivity to doxorubicin. Because we previously showed that reintroduction of wild-type p53 (wtp53) into STS cells harboring a p53 mutation led to increased doxorubicin chemosensitivity, we hypothesized that p53 participates in regulating Rad51 expression in STS. Reintroduction of wtp53 into STS cell lines resulted in decreased Rad51 protein and mRNA expression. Using luciferase reporter assays, we showed that reconstitution of wtp53 function decreased Rad51 promoter activity. Deletion constructs identified a specific Rad51 promoter region containing a p53-responsive element but no p53 consensus binding site. Electrophoretic mobility shift assays verified activator protein 2 (AP2) binding to this region and increased AP2 binding to the promoter in the presence of wtp53. Mutating this AP2 binding site eliminated the wtp53 repressive effect. Furthermore, AP2 knockdown resulted in increased Rad51 expression. In light of the importance of Rad51 in modulating STS chemoresistance, these findings point to a potential novel strategy for molecular-based treatments that may be of relevance to patients burdened by STS.

Vascular Endothelial Growth Factor Overexpression by Soft Tissue Sarcoma Cells: Implications for Tumor Growth, Metastasis, and Chemoresistance

To better elucidate the role of vascular endothelial growth factor (VEGF)(165) in soft tissue sarcoma (STS) growth, metastasis, and chemoresistance, we generated stably transfected human STS cell lines with VEGF(165) to study the effect of VEGF(165) on STS cells in vitro and the effect of culture medium from these cells on human umbilical vascular endothelial cells. Severe combined immunodeficient mice bearing xenografts of transfected cell lines were used to assess the effect of VEGF overexpression and the effect of VEGF receptor (VEGFR) 2 inhibition on STS growth, metastasis, and response to doxorubicin. VEGF(165)-transfected xenografts formed highly vascular tumors with shorter latency, accelerated growth, enhanced chemoresistance, and increased incidence of pulmonary metastases. Blockade of VEGFR2 signaling using DC101 anti-VEGFR2 monoclonal antibody enhanced doxorubicin chemoresponse; this combined biochemotherapy inhibited tumor growth and decreased pulmonary metastases without overt toxicity. Combined therapy reduced microvessel counts while increasing vessel maturation index. VEGF overexpression did not affect on the sarcoma cells per se; however, conditioned medium from VEGF transfectants caused increased endothelial cell proliferation, migration, and chemoresistance. Addition of DC101 induced endothelial cell sensitivity to doxorubicin and suppressed the activity of matrix metalloproteinases secreted by endothelial cells. We therefore conclude that VEGF is a critical determinant of STS growth and metastasis and that STS chemoresistance, in our model, is a process induced by the interplay between STS cells and tumor-associated endothelial cells. STS growth and metastasis can be interrupted by combined low-dose doxorubicin and anti-VEGFR2, a strategy that attacks STS-associated endothelial cells. In the future, such therapeutic approaches may be useful in treating STS before the development of clinically apparent metastases.

Morphological and molecular characterization of an undifferentiated soft tissue sarcoma cell line and derivative clones

From an undifferentiated soft tissue sarcoma (STS) a cell line designated US8-93 has been established. At subcloning the cell line US8-93 three different lines (US8-93A, B and C) could be set up. In a subsequent study characteristics for ultrastructure, growth, cell cycle distribution, karyotype, protein overexpression detected by immunohistochemistry (IHC) and p53 mutational status were determined. The cell line US8-93 as well as subclones contain mainly bipolar spindle-shaped cells and additionally some polygonal and multinucleated cells. Cells possess the characteristics of primitive mesenchymal cells based on their positive reactions with anti-vimentin and negative reactions for desmin, cytokeratin, myoglobin, S100, and NSE, implying a classification as an undifferentiated STS. Cytogenetic analysis revealed nearly diploid cells with several structural and numerical aberrations for chromosomes 1, 3, 4, 6, 9, 10, 12, 13, 15 and 18. IHC positivity was found for the tumor suppressor proteins p53 and Rb, the oncogene products Bcl-2, K-ras, N-ras, P-glycoprotein Mdr-1 and MDM-2. In the p53 gene a nonsense mutation in exon 4 was detected, that was confirmed in the original primary tumor and in three derivative clonal lines. The described STS cell line represents a valuable supplementation to the relatively small number of human STS cell lines currently available and may also provide a good in vitro model for studies of STS tumorigenesis in respect to a mutated p53 gene.