PIK3R3, part of the regulatory domain of PI3K, is upregulated in sarcoma stem-like cells and promotes invasion, migration, and chemotherapy resistance

To identify drivers of sarcoma cancer stem-like cells (CSCs), we compared gene expression using RNA sequencing between HT1080 fibrosarcoma and SK-LMS-1 leiomyosarcoma spheroids (which are enriched for CSCs) compared with the parent populations. The most overexpressed survival signaling-related gene in spheroids was phosphoinositide-3-kinase regulatory subunit 3 (PIK3R3), a regulatory subunit of PI3K, which functions in tumorigenesis and metastasis. In a human sarcoma microarray, PIK3R3 was also overexpressed by 4.1-fold compared with normal tissues. PIK3R3 inhibition using shRNA in the HT1080, SK-LMS-1, and DDLS8817 dedifferentiated liposarcoma in spheroids and in CD133+ cells (a CSC marker) reduced expression of CD133 and the stem cell factor Nanog and blocked spheroid formation by 61-71%. Mechanistic studies showed that in spheroid cells, PIK3R3 activated AKT and ERK signaling. Inhibition of PIK3R3, AKT, or ERK using shRNA or inhibitors decreased expression of Nanog, spheroid formation by 68-73%, and anchorage-independent growth by 76-91%. PIK3R3 or ERK1/2 inhibition similarly blocked sarcoma spheroid cell migration, invasion, secretion of MMP-2, xenograft invasion into adjacent normal tissue, and chemotherapy resistance. Together, these results show that signaling through the PIK3R3/ERK/Nanog axis promotes sarcoma CSC phenotypes such as migration, invasion, and chemotherapy resistance, and identify PIK3R3 as a potential therapeutic target in sarcoma.

Tropomyosin receptor kinases in sarcomas - of joy and despair

PURPOSE OF REVIEW

The relatively recent discovery of neurotrophic tropomyosin receptor kinase (NTRK) gene arrangements as pan-tumor predictive biomarkers has led to impressive novel treatments for patients with TRK fusions. Although the number of patients who qualify for treatment is vanishingly small for cancer patients in general, a few histological subsets of sarcomas exhibit NTRK fusions more commonly leading to large expectations within the sarcoma community.

RECENT FINDINGS

Larotrectenib and entrectenib have recently been approved based on durable responses in TRK positive cancers with nonresectable or metastatic disease, including many sarcomas. Identification of resistance mutations to TRKi has led to the development of novel salvage therapies which may soon further expand the armamentarium of treatments. The greatest barrier and frustration to date is the actual identification of patients who harbor the fusion. The dimension of rarity in sarcomas remains difficult to comprehend for both patients and caregivers. Diagnosis of NTRK fusions is complex, particularly in the context of sarcomas and can involve immunohistochemistry as a screening tool but frequently requires fluorescence-in-situ hybridization or next-generation sequencing (NGS) to confirm the diagnosis.

SUMMARY

The growing evidence on subtype-specific incidence of NTRK fusions will help to improve strategic prioritization or exclusion of subtypes to reduce the burden of negative testing. Next-generation inhibitors provide potential salvage treatment options for patients failing first-line therapy.

Elevated Adenosine Dehydrogenase (ADH) and Positive Tuberculin Test Firstly Misdiagnosed as Tuberculous Pleural Effusion Finally Proved as Pleural Mesothelial Sarcoma by Thoracoscopic Biopsy Pathology: a Case Report and Literature Review

BACKGROUND

In China, tuberculous pleural effusion is the most common cause for pleural effusion. Elevated ADH and positive tuberculin test usually are characteristic of tuberculous pleural effusion. We reported a 71-year-old male patient with elevated ADH and positive tuberculin test firstly misdiagnosed as tuberculous pleural effusion finally proven as pleural mesothelial sarcoma by thoracoscopic pathology.

METHODS

Appropriate laboratory tests and thoracentesis were carried out. Thoracoscopy and pathological biopsy were performed to differentiate tuberculous pleural effusion.

RESULTS

Chest CT showed right pleural effusion. ADH in pleural effusion was over 45 U/L and PPD test was positive. No abnormal cells were found in pleural effusion pathology. Pathology of thoracoscopic biopsy proved pleural mesothelioma.

CONCLUSIONS

Elevated ADH and positive tuberculin test are not a specific index for tuberculosis and thoracoscopic biopsy pathology is crucial for differential diagnosis.

Fructose-1,6-Bisphosphatase 2 Inhibits Sarcoma Progression by Restraining Mitochondrial Biogenesis

The remarkable cellular and genetic heterogeneity of soft tissue sarcomas (STSs) limits the clinical benefit of targeted therapies. Here, we show that expression of the gluconeogenic isozyme fructose-1,6-bisphosphatase 2 (FBP2) is silenced in a broad spectrum of sarcoma subtypes, revealing an apparent common metabolic feature shared by diverse STSs. Enforced FBP2 expression inhibits sarcoma cell and tumor growth through two distinct mechanisms. First, cytosolic FBP2 antagonizes elevated glycolysis associated with the "Warburg effect," thereby inhibiting sarcoma cell proliferation. Second, nuclear-localized FBP2 restrains mitochondrial biogenesis and respiration in a catalytic-activity-independent manner by inhibiting the expression of nuclear respiratory factor and mitochondrial transcription factor A (TFAM). Specifically, nuclear FBP2 colocalizes with the c-Myc transcription factor at the TFAM locus and represses c-Myc-dependent TFAM expression. This unique dual function of FBP2 provides a rationale for its selective suppression in STSs, identifying a potential metabolic vulnerability of this malignancy and possible therapeutic target.

Undifferentiated pleomorphic sarcomas with PRDM10 fusions have a distinct gene expression profile

Undifferentiated pleomorphic sarcoma (UPS) is a highly aggressive soft tissue tumor. A subset of UPS is characterized by a CITED2-PRDM10 or a MED12-PRDM10 gene fusion. Preliminary data suggest that these so-called PRDM10-rearranged tumors (PRT) are clinically more indolent than classical high-grade UPS, and hence important to recognize. Here, we assessed the spectrum of accompanying mutations and the gene expression profile in PRT using genomic arrays and sequencing of the genome (WGS) and transcriptome (RNA-seq). The fusion protein's function was further investigated by conditional expression of the CITED2-PRDM10 fusion in a fibroblast cell line, followed by RNA-seq and an assay for transposase-accessible chromatin (ATAC-seq). The CADM3 gene was found to be differentially up-regulated in PRT and cell lines and was also evaluated for expression at the protein level using immunohistochemistry (IHC). The genomic analyses identified few and nonrecurrent mutations in addition to the structural variants giving rise to the gene fusions, strongly indicating that the PRDM10-fusions represent the critical driver mutations. RNA-seq of tumors showed a distinct gene expression profile, separating PRT from high-grade UPS and other soft tissue tumors. CADM3 was among the genes that was consistently and highly expressed in both PRT and fibroblasts expressing CITED2-PRDM10, suggesting that it is a direct target of the PRDM10 transcription factor. This conclusion is in line with sequencing data from ATAC-seq, showing enrichment of PRDM10 binding sites, suggesting that the amino-terminal fusion partner contributes by making the DNA more accessible to PRDM10 binding. © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

The landscape of tyrosine kinase inhibitors in sarcomas: looking beyond pazopanib

Introduction: Tyrosine kinases are key mediators of intracellular signaling cascades and aberrations in these proteins have been implicated in driving oncogenesis through the dysregulation of fundamental cellular processes including proliferation, migration, and apoptosis. As such, targeting these proteins with small molecule tyrosine kinase inhibitors (TKI) has led to significant advances in the treatment of a number of cancer types.Areas covered: Soft tissue sarcomas (STS) are a heterogeneous and challenging group of rare cancers to treat, but the approval of the TKI pazopanib for the treatment of advanced STS demonstrates that this class of drugs may have broad utility against a range of different sarcoma histological subtypes. Since the approval of pazopanib, a number of other TKIs have entered clinical trials to evaluate whether their activity in STS matches the promising results seen in other solid tumors. In this article, we review the emerging role of TKIs in the evolving landscape of sarcoma treatment.Expert opinion: As our biological understanding of response and resistance of STS to TKIs advances, we anticipate that patient management will move away from a 'one size fits all' paradigm toward personalized, multi-line, and patient-specific treatment regimens where patients are treated according to the underlying biology and genetics of their specific disease.

Pan-mutant IDH1 inhibitor BAY 1436032 for effective treatment of IDH1 mutant astrocytoma in vivo

Mutations in codon 132 of isocitrate dehydrogenase (IDH) 1 are frequent in diffuse glioma, acute myeloid leukemia, chondrosarcoma and intrahepatic cholangiocarcinoma. These mutations result in a neomorphic enzyme specificity which leads to a dramatic increase of intracellular D-2-hydroxyglutarate (2-HG) in tumor cells. Therefore, mutant IDH1 protein is a highly attractive target for inhibitory drugs. Here, we describe the development and properties of BAY 1436032, a pan-inhibitor of IDH1 protein with different codon 132 mutations. BAY 1436032 strongly reduces 2-HG levels in cells carrying IDH1-R132H, -R132C, -R132G, -R132S and -R132L mutations. Cells not carrying IDH mutations were unaffected. BAY 1436032 did not exhibit toxicity in vitro or in vivo. The pharmacokinetic properties of BAY 1436032 allow for oral administration. In two independent experiments, BAY 1436032 has been shown to significantly prolong survival of mice intracerebrally transplanted with human astrocytoma carrying the IDH1R132H mutation. In conclusion, we developed a pan-inhibitor targeting tumors with different IDH1R132 mutations.

Epithelioid inflammatory myofibroblastic sarcoma treated with ALK inhibitor: a case report and review of literature

Epithelioid inflammatory myofibroblastic sarcoma is extremely rare and belongs to a variant of inflammatory myofibrobalstic tumor with aggressive clinical course. We describe a case of a 22 years old man presented with an abdominal huge tumor. Microscopically, the neoplasm cells were rounded and epithelioid in shape. Abundant interstitial edema and less myxoid stroma were also present together with an inflammatory infiltrate. Fluorescence in situ hybridization revealed that ALK gene presented mutation. After surgery the patient received chemotherapy with an anaplastic lymphoma kinase (ALK) inhibitor, crizotinib. The patient continues to be alive with disease for 16 months and has no recurrence. Although EIMS has a poor prognosis, this is the few successful case with sustained response of targeted therapy.

Undifferentiated pleomorphic sarcoma with co-existence of KRAS/PIK3CA mutations

Undifferentiated pleomorphic sarcoma (UPS), previously known as malignant fibrous histiocytoma, comprises a series of high-grade soft tissue sarcomas, which fail to exhibit any specific line of differentiation by using currently available ancillary techniques. Studies on gene mutation screening occurring in UPS are rarely conducted. In this study, we described a case of UPS and analyzed its mutation changes. We detected 19 hotspot oncogenes in the case. To the best of our knowledge, this study is the first to use a high-throughput OncoCarta panel 1.0 and MassARRAY system to detect 238 known mutations in 19 hotspot oncogenes in UPS. In this study, our result revealed two missense mutations, namely, KRAS mutation (35G > A, G12D) and PIK3CA mutation (1636C > A, Q546K) in the case.

Metabolic characterization of cultured mammalian cells by mass balance analysis, tracer labeling experiments and computer-aided simulations

Studying metabolic directions and flow rates in cultured mammalian cells can provide key information for understanding metabolic function in the fields of cancer research, drug discovery, stem cell biology, and antibody production. In this work, metabolic engineering methodologies including medium component analysis, (13)C-labeling experiments, and computer-aided simulation analysis were applied to characterize the metabolic phenotype of soft tissue sarcoma cells derived from p53-null mice. Cells were cultured in medium containing [1-(13)C] glutamine to assess the level of reductive glutamine metabolism via the reverse reaction of isocitrate dehydrogenase (IDH). The specific uptake and production rates of glucose, organic acids, and the 20 amino acids were determined by time-course analysis of cultured media. Gas chromatography-mass spectrometry analysis of the (13)C-labeling of citrate, succinate, fumarate, malate, and aspartate confirmed an isotopically steady state of the cultured cells. After removing the effect of naturally occurring isotopes, the direction of the IDH reaction was determined by computer-aided analysis. The results validated that metabolic engineering methodologies are applicable to soft tissue sarcoma cells derived from p53-null mice, and also demonstrated that reductive glutamine metabolism is active in p53-null soft tissue sarcoma cells under normoxia.

Inhibition of polo like kinase 1 in sarcomas induces apoptosis that is dependent on Mcl-1 suppression

Sarcomas are rare cancers and the current treatments in inoperable or metastatic disease have not been shown to prolong survival. In order to develop novel targeted therapies, we tested the efficacy of polo-like kinase 1 (PLK-1) inhibitor (TAK-960) in sarcoma. All the sarcoma cell lines were sensitive to TAK-960 with IC50s in the low nanomolar range. We chose MPNST, CHP100 and LS141 for our studies and of which MPNST cells exclusively underwent polyploidy after a delay in mitosis for about 18 hours; CHP100 cells, after a 24h mitotic delay, died of apoptosis; LS141, after a delay in mitosis stayed at 4N with mild apoptosis. Apoptosis induced by TAK-960 in CHP100 was associated with down-regulation of Mcl-1 and the effect was recapitulated by down-regulating PLK1 by siRNA, confirming that the effect of TAK-960 on Mcl-1 expression is target specific. With suppression of Mcl-1 by siRNA, TAK-960 induced apoptosis in MPNST cells as well. These effects were confirmed in vivo, such that TAK-960 more effectively inhibited CHP100 than MPNST xenografts. In the setting of PLK-1 inhibition, Mcl-1 down regulation is shown to be an important determinant of apoptosis. Collectively, the net effect of this is to drive cells to apoptosis, resulting in a greater anti-tumor effect in vivo. Therefore, targeting PLK-1 should have a greater impact in treating sarcomas provided there is concomitant suppression of Mcl-1. These results further indicate that Mcl-1 could be an important biomarker to predict sensitivity to the induction of apoptosis by PLK-1 targeted therapy in sarcoma.

Targeting protein kinase C in sarcoma

Protein kinase C (PKC) is a family of serine/threonine tyrosine kinases that regulate many cellular processes including division, proliferation, survival, anoikis and polarity. PKC is abundant in many human cancers and aberrant PKC signalling has been demonstrated in cancer models. On this basis, PKC has become an attractive target for small molecule inhibition within oncology drug development programmes. Sarcoma is a heterogeneous group of mesenchymal malignancies. Due to their relative insensitivity to conventional chemotherapies and the increasing recognition of the driving molecular events of sarcomagenesis, sarcoma provides an excellent platform to test novel therapeutics. In this review we provide a structure-function overview of the PKC family, the rationale for targeting these kinases in sarcoma and the state of play with regard to PKC inhibition in the clinic.

V-ATPase as an effective therapeutic target for sarcomas

Malignant tumors show intense glycolysis and, as a consequence, high lactate production and proton efflux activity. We investigated proton dynamics in osteosarcoma, rhabdomyosarcoma, and chondrosarcoma, and evaluated the effects of esomeprazole as a therapeutic agent interfering with tumor acidic microenvironment. All sarcomas were able to survive in an acidic microenvironment (up to 5.9–6.0 pH) and abundant acidic lysosomes were found in all sarcoma subtypes. V-ATPase, a proton pump that acidifies intracellular compartments and transports protons across the plasma membrane, was detected in all cell types with a histotype-specific expression pattern. Esomeprazole administration interfered with proton compartmentalization in acidic organelles and induced a significant dose-dependent toxicity. Among the different histotypes, rhabdomyosarcoma, expressing the highest levels of V-ATPase and whose lysosomes are most acidic, was mostly susceptible to ESOM treatment.

Human sarcomas are mosaic for telomerase-dependent and telomerase-independent telomere maintenance mechanisms: implications for telomere-based therapies

Telomere shortening necessitates that tumor cells activate a telomere maintenance mechanism (TMM) to support immortalization. Although most tumor cells activate expression of the enzyme telomerase, some cells elongate telomeres in a telomerase-independent manner, termed alternative lengthening of telomeres (ALT). Previous studies have evaluated the presence of telomerase or ALT mechanisms or both in a variety of tumor types. Our studies also show that TMMs are not mutually exclusive in some tumors. In contrast, our IHC analyses of human sarcomas identified a subset of tumors with some cells containing ALT-associated PML bodies, a hallmark of ALT, and separate cells expressing telomerase in the same tumor. By using a second set of human osteosarcomas, we merged IHC and biochemical analyses to characterize more fully the tumor TMM. The IHC data reveal the presence of both telomerase- and ALT-positive tumor cells in samples that demonstrate characteristics of both telomerase and ALT in biochemical assays. These assays, which measure telomere length and telomerase activity of tumor extracts, are conventionally used to classify tumor TMM. Our results suggest that TMM is not a single or perhaps static characteristic of some tumors and that TMM heterogeneity should be considered in tumor stratification. Furthermore, clinical interest in telomere-based therapies may necessitate accurate characterization of tumor TMM before treatment to maximize therapeutic efficacy.

PI3K inhibition enhances doxorubicin-induced apoptosis in sarcoma cells

We searched for a drug capable of sensitization of sarcoma cells to doxorubicin (DOX). We report that the dual PI3K/mTOR inhibitor PI103 enhances the efficacy of DOX in several sarcoma cell lines and interacts with DOX in the induction of apoptosis. PI103 decreased the expression of MDR1 and MRP1, which resulted in DOX accumulation. However, the enhancement of DOX-induced apoptosis was unrelated to DOX accumulation. Neither did it involve inhibition of mTOR. Instead, the combination treatment of DOX plus PI103 activated Bax, the mitochondrial apoptosis pathway, and caspase 3. Caspase 3 activation was also observed in xenografts of sarcoma cells in nude mice upon combination of DOX with the specific PI3K inhibitor GDC-0941. Although the increase in apoptosis did not further impact on tumor growth when compared to the efficient growth inhibition by GDC-0941 alone, these findings suggest that inhibition of PI3K may improve DOX-induced proapoptotic effects in sarcoma. Taken together with similar recent studies of neuroblastoma- and glioblastoma-derived cells, PI3K inhibition seems to be a more general option to sensitize tumor cells to anthracyclines.

Telomerase reverse transcriptase (TERT) expression and role of vincristine sulfate in mouse model of malignancy related peritoneal ascites: an experimental metastatic condition

AIM

To evaluate the efficacy of intraperitoneal vincristine administration into ascitic sarcoma-180 bearing mice as a model of human malignant ascites regarding various peritoneal/retroperitoneal sarcomatosis, and to evaluate the flowcytometric telomerase reverse transcriptase expression for the diagnostic and prognostic purposes.

METHODS

Present study included disease induction by intraperitoneal homologous ascitic sarcoma-180 transplantation followed by in vivo intraperitoneal drug administration to study mitotic index, flowcytometric cell cycle and telomerase reverse transcriptase expression pattern, erythrosin-B dye exclusion study for malignant cell viability assessment. Besides, in vitro malignant ascite culture in presence and absence of vincristine sulfate and survival study were also taken into consideration.

RESULTS

Intraperitoneal vincristine administration (concentration 0.5 mg/kg body weight) significantly diminished the mitotic index in diseased subjects in comparison to untreated control subjects. Treated group of animals showed increased life span and median survival time. Cell viability assessment during the course of drug administration also revealed gradual depression on cell viability over time. Flowcytometric cell cycle analysis showed a good prognostic feature of chemotherapeutic administration schedule by representing high G2/M phase blocked cells along with reduced telomerase reverse transcriptase positive cells in treated animals.

CONCLUSION

We conclude that long term administration of vincristine sulfate in small doses could be a good pharmacological intervention in case of malignant peritoneal ascites due to sarcomatosis as it indirectly reduced the level of telomerase reverse transcriptase expression in malignant cells by directly regulating cell cycle and simultaneously increased the life expectancy of the diseased subjects.

Extracellular pressure stimulates adhesion of sarcoma cells via activation of focal adhesion kinase and Akt

BACKGROUND

The effect of extracellular pressure on adhesion and adhesiogenic focal adhesion kinase (FAK) and Akt signaling in sarcomas was investigated.

METHODS

Human sarcoma cells (HT-1080 fibrosarcoma, KHOS-240S osteosarcoma, and A-673 rhabdomyosarcoma) were subjected to increased pressure followed by adhesion assay. Two cell lines were pretreated with the FAK inhibitor 1,2,4,5-benzenetetraamine tetrahydrochloride (Y15) or Akt IV inhibitor, followed by Western analysis for activated FAK and Akt. Parallel studies were conducted in cells from a resected human fibrous histiosarcoma.

RESULTS

Pressure increased adhesion in all 3 sarcoma lines and primary histosarcoma cells by 7% to 18% (n = 6; P < .01 each). Pressure activated FAK and Akt (n = 5; P < .01). Inhibiting FAK or Akt inhibited FAK or Akt phosphorylation and the stimulation of adhesion by increased pressure (n = 5 each; P < .01 each).

CONCLUSIONS

Pressure increases sarcoma cell adhesiveness via Akt and FAK. Perioperative manipulation or forces in lymphatic or circulatory systems may potentiate local recurrence or distant metastasis.

Immunoglobulin G locus events in soft tissue sarcoma cell lines

Recently immunoglobulins (Igs) have been found to be expressed by cells other than B lymphocytes, including various human carcinoma cells. Sarcomas are derived from mesenchyme, and the knowledge about the occurrence of Ig production in sarcoma cells is very limited. Here we investigated the phenomenon of immunoglobulin G (IgG) expression and its molecular basis in 3 sarcoma cell lines. The mRNA transcripts of IgG heavy chain and kappa light chain were detected by RT-PCR. In addition, the expression of IgG proteins was confirmed by Western blot and immunofluorescence. Immuno-electron microscopy localized IgG to the cell membrane and rough endoplasmic reticulum. The essential enzymes required for gene rearrangement and class switch recombination, and IgG germ-line transcripts were also identified in these sarcoma cells. Chromatin immunoprecipitation results demonstrated histone H3 acetylation of both the recombination activating gene and Ig heavy chain regulatory elements. Collectively, these results confirmed IgG expression in sarcoma cells, the mechanism of which is very similar to that regulating IgG expression in B lymphocytes.

Matrix metalloproteinase 1: role in sarcoma biology

In carcinomas stromal cells participate in cancer progression by producing proteases such as MMPs. The expression MMP1 is a prognostic factor in human chondrosarcoma, however the role in tumor progression is unknown. Laser capture microdissection and In Situ hybridization were used to determine cellular origin of MMP1 in human sarcomas. A xenogenic model of tumor progression was then used and mice were divided in two groups: each harboring either the control or a stably MMP1 silenced cell line. Animals were sacrificed; the neovascularization, primary tumor volumes, and metastatic burden were assessed. LCM and RNA-ISH analysis revealed MMP1 expression was predominantly localized to the tumor cells in all samples of sarcoma (p = 0.05). The percentage lung metastatic volume at 5 weeks (p = 0.08) and number of spontaneous deaths secondary to systemic tumor burden were lower in MMP1 silenced cell bearing mice. Interestingly, this group also demonstrated a larger primary tumor size (p<0.04) and increased angiogenesis (p<0.01). These findings were found to be consistent when experiment was repeated using a second independent MMP1 silencing sequence. Prior clinical trials employing MMP1 inhibitors failed because of a poor understanding of the role of MMPs in tumor progression. The current findings indicating tumor cell production of MMP1 by sarcoma cells is novel and highlights the fundamental differences in MMP biology between carcinomas and sarcomas. The results also emphasize the complex roles of MMP in tumor progression of sarcomas. Not only does metastasis seem to be affected by MMP1 silencing, but also local tumor growth and angiogenesis are affected inversely.

Lentiviral shRNA screen of human kinases identifies PLK1 as a potential therapeutic target for osteosarcoma

We describe an optimized systematic screen of known kinases using osteosarcoma cell lines (KHOS and U-2OS) and a lentiviral-based short hairpin RNA (shRNA) human kinase library. CellTiter 96(R)AQueous One Solution Cell Proliferation Assay was used to measure cell growth and survival. We identified several kinases, including human polo-like kinase (PLK1), which inhibit cell growth and induce apoptosis in osteosarcoma cells when knocked down. cDNA rescue and synthetic siRNA assays confirm that the observed phenotypic changes result from the loss of PLK1 gene expression. Furthermore, a small molecule inhibitor to PLK1 inhibited osteosarcoma cell growth and induced apoptosis. Western blot analysis confirmed that PLK1 is highly expressed and activated in several osteosarcoma cell lines as well as in resected tumor samples. Immunohistochemistry analysis showed that patients with high PLK1 tumor expression levels correlated with significantly shorter survival than patients with lower levels of tumor PLK1 expression. These results demonstrate the capability and feasibility of a high-throughput screen with a large collection of lentiviral kinases and its effectiveness in identifying potential drug targets. The development of more potent inhibitors that target PLK1 may open doors to a new range of anti-cancer strategies in osteosarcoma.

Proteasomes are not a target for doxorubicin in feline injection-site sarcoma

The potent anti-cancer agent doxorubicin (DOX) induces apoptosis of rapidly proliferating cells by inhibiting cellular proteasomes. The aim of the present study was to determine whether DOX modulates the level of expression and function of proteasomes in feline injection-site sarcoma (FISS). Tissue extracts from primary sarcoma lesions and the related healthy subcutis of 18 cats affected by FISS were investigated. Nine of these cats had received neoadjuvant DOX treatment and nine cats did not receive this therapy. There was enhanced proteasome expression in FISS, but this was not affected by administration of DOX. This finding may account for the low clinical effectiveness of DOX therapy in FISS and provides the rationale for developing new therapeutic protocols aimed at achieving better proteasomal inhibition in FISS and other tumours that respond poorly to DOX therapy.

Telomeres and telomerase in sarcomas

Telomeres of human tumor cells have two types of telomere maintenance mechanisms by telomerase activation and alternative lengthening of telomeres (ALT). Although over 80% of all carcinomas rely on telomerase activity to maintain stable telomere length, many types of sarcoma elongate telomeres consistent with ALT in the absence of telomerase activity. Recently, the presence of telomerase activity and ALT in several sarcomas was examined extensively, and recent studies indicate a positive correlation between the telomere maintenance mechanism and tumor aggressiveness in several sarcoma types. We reviewed both the activation of telomere maintenance in a variety of common bone and soft tissue sarcoma subtypes, and the consequences of telomere maintenance mechanisms with respect to the clinical characteristics.

Cyclooxygenase 2 expression in soft tissue leiomyosarcoma

BACKGROUND

Cyclooxygenase 2 (COX2) expression is up-regulated and associated with adverse prognosis in select types of carcinoma. Although not extensively studied in skeletal or soft tissue sarcoma, expression of COX2 has been described in a variable number of gynecological and non-gynecological leiomyosarcomas. In this study, the prevalence and prognostic implications of COX2 expression in leiomyosarcoma were evaluated further.

MATERIALS AND METHODS

Immunohistochemical stains for COX2 were performed on 33 samples of soft tissue leiomyosarcoma and tested for their association with clinicopathological parameters and patient outcome.

RESULTS

COX2 staining was limited to tumor cells surrounding areas of tumor necrosis in 6 cases. There were no statistically significant correlations with the clinicopathological parameters studied, including local recurrence, distant metastasis, or disease-specific death.

CONCLUSION

The low frequency, restricted distribution and absence of prognostic implications of COX2 expression soft tissue leiomyosarcoma suggest that this enzyme may not be a useful pharmacological target in this clinical setting.

Some properties of cathepsins chemically fixed to carriers

An insoluble preparation of rat liver cathepsin D was obtained by coupling the enzyme to Enzacryl Polyacetal (EPA-cathepsin) and to CNBr-activated Sepharose 4B. EPA-cathepsin was active toward the synthetic hexapeptides (Gly-Phe-Leu)2 and did not split hemoglobin. The optimum pH of splitting was displaced upward by 1.5 units to pH 5.0. The enzyme exhibited maximum activity at 60 degrees C. No appreciable loss of activity was seen on storage of the enzyme for 4 months or after repeated use of the preparations. Coupling of rat liver cathepsin D to activated Sepharose gave preparations active towards both protein and synthetic substrates. The preparations were totally inactive in acid media and exhibited maximum activity at pH 7.0, that is, under physiological conditions. Optimum temperature was 65 degrees. The specific activity of the preparations (pH 7.0, 65 degrees) was 60-110 percent that of the free enzyme in acid media. Proteolytic activity of the Sepharose-coupled cathepsin D was not inhibited by pepstatin, whereas that of the free enzyme was fully inhibited by this reagent. A sarcoma cathepsin, similar in some of its properties to the rat liver enzyme, was also coupled to CNBr-activated Sepharose 4B. The preparation split protein substrates at pH 7.0 and possessed enhanced thermostability. The enzymes fixed on Sepharose showed increased stability.

Von Hippel-Lindau-coupled and transcription-coupled nucleotide excision repair-dependent degradation of RNA polymerase II in response to trabectedin

PURPOSE

Ecteinascidin 743 (Et743; trabectedin, Yondelis) has recently been approved in Europe for the treatment of soft tissue sarcomas and is undergoing clinical trials for other solid tumors. Et743 selectively targets cells proficient for TC-NER, which sets it apart from other DNA alkylating agents. In the present study, we examined the effects of Et743 on RNA Pol II.

EXPERIMENTAL DESIGN AND RESULTS

We report that Et743 induces the rapid and massive degradation of transcribing Pol II in various cancer cell lines and normal fibroblasts. Pol II degradation was abrogated by the proteasome inhibitor MG132 and was dependent on TC-NER. Cockayne syndrome (CS) cells and xeroderma pigmentosum (XP) cells (XPD, XPA, XPG, and XPF) were defective in Pol II degradation, whereas XPC cells whose defect is limited to global genome NER in nontranscribing regions were proficient for Pol II degradation. Complementation of the CSB and XPD cells restored Pol II degradation. We also show that cells defective for the VHL complex were defective in Pol II degradation and that complementation of those cells restores Pol II degradation. Moreover, VHL deficiency rendered cells resistant to Et743-induced cell death, a similar effect to that of TC-NER deficiency.

CONCLUSION

These results suggest that both TC-NER-induced and VHL-mediated Pol II degradation play a role in cell killing by Et743.

Quantitative measurement of telomerase activity and localization of its catalytic subunit (hTERT) in chronic inflammation of capsule formation around various model implants and in sarcomas in a rat model

Telomerase is upregulated in some preneoplastic lesions and overexpressed in the majority of malignant tumors, but absent in most nonneoplastic somatic tissues. We analyzed telomerase activity using TRAP-assay in capsule tissues in a rat model with chronic inflammation and in tumor, and visualized the catalytic subunit of telomerase (hTERT) by immunhistochemistry. Significant elevated telomerase activity was found in tumor tissue compared with nonneoplastic tissue (p = 0.047). Cases with a strong inflammation in capsule tissue showed a specific telomerase activity. In these cases, there were no significant differences in telomerase activities compared with malignant tumor tissue. We demonstrate elevated telomerase activity and its diagnostic limits around model implants in a rat model, and visualize its expression not only in malignant tissue but also in inflammatory cells. So the quantitative measurement of telomerase activity should not be applied in general as a marker for malignancy in capsule tissue.

Ultrasound exposure in the presence of hematoporphyrin induced loss of membrane integral proteins and inactivity of cell proliferation associated enzymes in sarcoma 180 cells in vitro

Ultrasonically induced effects of hematoporphyrin (HPD) on cell damage and membrane protein alteration of S180 isolated tumor cells in vitro were investigated, and the potential mechanisms of sonodynamic therapy (SDT) inhibiting tumor growth were discussed. Tumor cells suspended in air-saturated PBS (pH 7.2) were exposed to ultrasound at 1.8 MHz for up to 180s in the presence and absence of HPD. The viability of cells was determined by a trypan blue exclusion test. To estimate the damage effects of SDT on plasma membrane of tumor cells primarily, membrane integral proteins (EGFR, Ras, Fas, FasL) and cell proliferation associated enzymes (adenylate cyclase and guanylate cyclase) were checked with immunochemical methods. The results indicated that the intensity threshold for ultrasonically induced cell damage at 1.8 MHz was 3 W/cm2. At this condition, the expression of the integral proteins was obviously inhibited and the activity of the enzymes was decreased post ultrasound treatment in the presence of 20 microg/ml HPD. Loss of the membrane proteins and inactivity of AC and GC post SDT was time-dependent. This paper reveals SDT can cause the loss of tumor cell membrane integral proteins and inactivity of the enzymes associated with cell proliferation which might be attributed to a sonochemical activation mechanism. The mechanisms by that tumor growth is inhibited by SDT can be understood as that the growth signaling pathway is partially interdicted and the resistance of tumor cells to the specifically activated immune cells is weakened.

The synthesis and activity of lipoprotein lipase in the subcutaneous adipose tissue of patients with musculoskeletal sarcomas

The purpose of this study was to explore the triacylglycerol (TG) deposition and lipoprotein lipase (LPL) activity in the adipose tissue of patients with muculoskeletal sarcoma. Subcutaneous adipose tissue was obtained from the thighs of 19 patients with musculoskeletal sarcomas (sarcoma group) and 20 patients with osteoarthritis of the hip joint (control group) at surgery. The adipose tissue was homogenized and aliquots of the homogenate were used to measure the TG content and to prepare an acetone/ether powder to measure the LPL activity. The TG content was higher, but not significantly, in the sarcoma group than in the control group. The LPL activity of the sarcoma group was significantly higher than that of the control group. The TG content of the sarcoma group correlated positively with the LPL activity. [35S]Methionine incorporation investigation showed that the rate of LPL synthesis was significantly higher in the sarcoma group than in the control group. These results indicated that LPL was up-regulated at the transcriptional/translational level, thus resulting in an increased TG deposition in the adipose tissue of patients with muculoskeletal sarcoma.

Inhibition of PKCalpha activation in human bone and soft tissue sarcoma cells by the selective PKC inhibitor PKC412

BACKGROUND

PKC412, formerly CGP41251, N-benzoylstaurosporine, was initially developed as a selective protein kinase C (PKC) inhibitor, and it preferentially inhibits conventional PKC family members. In this study, the expression of PKCa was examined in human osteosarcoma and MFH cell lines, and the inhibitory effect of PKC412 on the proliferation of the cell lines was evaluated.

MATERIALS AND METHODS

Three human osteosarcoma cell lines (KTHOS, MG63 and KHOS) and four human MFH cell lines (TNMY1, GBS-1, Nara-F and Nara-H) were used. The expression of PKCalpha and phosphorylated PKCalpha were analyzed using both Western blotting analysis and immunocytochemical analysis. The effect of PKC412 on cell proliferation was evaluated using the MTS assay technique.

RESULTS

PKC412 inhibited cell proliferation of all seven cell lines in a dose- and time-dependent manner. Both Western blotting analysis and immunocytochemical analysis revealed that not only PKCalpha but also phosphorylated PKCalpha were expressed in all cell lines incubated with the culture medium without any stimuli. PKC412 suppressed phosphorylation of PKCalpha in all cell lines at a concentration of 1 microM.

CONCLUSION

The inhibition of cell proliferation of the human osteosarcoma and MFH cell lines by PKC412 might be due to reduced PKCalpha activity. This suggests PKC412 might be a potent chemotherapeutic agent for human sarcomas.

Matrix metalloproteinase expression in high grade soft tissue sarcomas

Soft tissue sarcomas comprise a heterogeneous group of mesenchymal tumors with varying biological behavior ranging from indolent tumors with no or minimal metastatic risk to aggressive and frequently metastasizing tumors. Among the more common aggressive adult soft tissue sarcomas are malignant fibrous histiocytoma, synovial sarcoma and liposarcoma. Matrix metalloproteinases are enzymes which perform a homeostatic role in mesenchymal tissue and function in both tumorigenesis and metastasis. The objectives of this study are to determine the presence and relative quantity of matrix metalloproteinases (MMPs) -1, -2, -8, -9, and -13; extracellular matrix metalloproteinase inducer (EMMPRIN); and tissue inhibitors of matrix metalloproteinases (TIMP)-1 and -2 in high grade soft tissue sarcoma tumor specimens using real-time PCR. The second objective is to determine if a relationship exists between quantity of EMMPRIN, MMPs, and TIMPs expressed in tumor tissue and disease-free survival. One hundred and forty patients diagnosed with high grade soft tissue sarcomas between 1995-2003 were identified. Tissue blocks and histologic slides were acquired for 41 specimens. Tumor specimens included 29 malignant fibrous histiocytomas, 3 liposarcomas and 11 synovial sarcomas. RNA was extracted and RT-PCR was performed in triplicate. No significant differences were found between the three types of high grade soft tissue sarcomas studied and the expression of MMPs. Interestingly, no relationship was found between high or low levels of MMPs when compared with disease-free survival. Our data support other research which finds variable correlation between MMP expression in soft tissue sarcomas and disease-free survival. We assert that the difference in correlation between MMP expression in carcinomas and sarcomas and disease-free survival is based on the vast phenotypic and genotypic difference between the cells of origin.

The biology behind mTOR inhibition in sarcoma

Dysregulation of the mammalian target of rapamycin (mTOR) pathway has been found in many human tumors and implicated in the promotion of cancer cell growth and survival. Hence, the mTOR pathway is considered an important target for anticancer drug development. Currently, the mTOR inhibitor rapamycin and its derivatives CCI-779, RAD001, and AP23573 are being evaluated in cancer clinical trials. To date, clinical results have shown good tolerability of treatment with mTOR inhibitors in most reports and varying effectiveness of mTOR inhibitors in a variety of tumors in a subset of patients. For the targeted treatment of sarcomas, AP23573 has shown promising clinical efficacy and low toxicity profiles in patients. Further studies should define the optimal dose/schedule, patient selection, and combination strategies with other biological agents, especially those targeting signaling pathways crucial for cell survival. Disclosure of potential conflicts of interest is found at the end of this article.

Aromatase inhibitors in gynecologic cancers

The female genital tract is hormonally responsive, and consequently some tumors, which arise within in it, may be treated at least in part, with hormonal manipulation. The range of responses in clinical trials and case reports will be reviewed. Many of these diseases are too rare for clinical trial testing, and in some cases evidence is anecdotal at best. Recurrences of ovarian cancer have been treated with tamoxifen and megesterol acetate with variable response rates from 0 to 56%. The favorable toxicity profile of aromatase inhibitors led to trials of these agents for the treatment of relapsed epithelial ovarian cancer. These agents have proved tolerable with minor response rates but a significant disease stabilization rate, which may be prolonged in a minority of cases. It is unclear if these responses may be predicted by estrogen receptor expression or aromatase expression. Anastrazole has also been tried in combination with an EGFR receptor-inhibitor, again showing minor responses but possibly an increase in TTT in some patients. Granulosa cell tumors of the ovary are rare, hormonally sensitive tumors, with reported responses to a variety of hormonal manipulations, including aromatase inhibition. In addition, combined endocrine blockade, including aromatase inhibition, has been tried with reports of success. Endometrial cancers, particularly type I lesions, are often treated with hormonal manipulation, most commonly with progestins, but also with antiestrogens such as tamoxifen. A trial of aromatase inhibition in the treatment of recurrent endometrial cancer showed minimal responses. Endometrial stromal sarcoma, an uncommon uterine malignancy, has shown response to hormonal treatments, with multiple case reports of efficacy of aromatase inhibition. Despite the rarity of some of these tumor types, rare tumor study groups, such as within the Gynecologic Oncology Group, should make an effort to prospectively define the utility of these treatments.

Assessment of ifosfamide pharmacokinetics, toxicity, and relation to CYP3A4 activity as measured by the erythromycin breath test in patients with sarcoma

BACKGROUND

Ifosfamide is a chemotherapeutic agent that requires cytochrome P450 3A (CYP3A) for bioactivation and metabolism. To the authors' knowledge, the correlation between dose, pharmacokinetics, CYP3A, and toxicity has not been fully evaluated. A randomized Phase II trial was performed on 22 soft tissue sarcoma patients treated with doxorubicin (60 mg/m(2)/cycle) and either high-dose ifosfamide (12 g/m(2)/cycle) or standard-dose ifosfamide (6 g/m(2)/cycle). The pharmacokinetics of ifosfamide and CYP3A measurements observed are reported.

METHODS

Pharmacokinetic parameters for ifosfamide, 2-dichloroethylifosfamide (2-DCE), and 3-dichloroethylifosfamide (3-DCE) were collected after the first ifosfamide infusion in 13 patients. Bayesian designed limited pharmacokinetic data were collected from an additional 41 patients. The erythromycin breath test (ERMBT) was performed on 81 patients as an in vivo phenotypic assessment of CYP3A activity.

RESULTS

Fourteen-hour (peak) plasma levels of ifosfamide, 2-DCE, and 3-DCE were found to correlate strongly with the respective area under the curve (AUC) 0-24 values (r=0.97, 0.94, and 0.95; P<.0001). Patients who experienced a grade 3-4 absolute neutrophil count (ANC), platelet, or creatinine toxicity (using the National Cancer Institute Common Toxicity Criteria [version 2]) were found to have statistically significantly higher median 14-hour plasma levels of ifosfamide, 2-DCE, and 3-DCE compared with patients with grade 0-2 toxicity. ERMBT was not found to correlate with pharmacokinetic parameters of ifosfamide and metabolites or toxicity.

CONCLUSIONS

The 14-hour plasma level of ifosfamide, 2-DCE, and 3-DCE is a simple and appropriate substitute for describing the AUC of ifosfamide after 1 day of a 1-hour to 2-hour infusion of drug. Fourteen-hour plasma levels of ifosfamide and metabolites are useful predictors of neutropenia, thrombocytopenia, and creatinine toxicity. ERMBT was not found to accurately correlate with ifosfamide pharmacokinetics or clinical toxicity.

The AKT-mTOR pathway plays a critical role in the development of leiomyosarcomas

We analyzed the PI3K-AKT signaling cascade in a cohort of sarcomas and found a marked induction of insulin receptor substrate-2 (IRS2) and phosphorylated AKT and a concomitant upregulation of downstream effectors in most leiomyosarcomas. To determine the role of aberrant PI3K-AKT signaling in leiomyosarcoma pathogenesis, we genetically inactivated Pten in the smooth muscle cell lineage by cross-breeding Pten(loxP/loxP) mice with Tagln-cre mice. Mice carrying homozygous deletion of Pten alleles developed widespread smooth muscle cell hyperplasia and abdominal leiomyosarcomas, with a very rapid onset and elevated incidence (approximately 80%) compared to other animal models. Constitutive mTOR activation was restricted to the leiomyosarcomas, revealing the requirement for additional molecular events besides Pten loss. The rapamycin derivative everolimus substantially decelerated tumor growth on Tagln-cre/Pten(loxP/loxP) mice and prolonged their lifespan. Our data show a new and critical role for the AKT-mTOR pathway in smooth muscle transformation and leiomyosarcoma genesis, and support treatment of selected sarcomas by the targeting of this pathway with new compounds or combinations of these with conventional chemotherapy agents.

Analysis of potential receptor tyrosine kinase targets in intimal and mural sarcomas

Primary sarcomas of the great vessels are very rare neoplasms and only a few cases have been reported. They are divided into the two broad categories of intimal or luminal and mural sarcomas. We analysed eight advanced high-grade sarcomas originating from major vessels (seven intimal and one mural sarcoma) by means of immunohistochemistry and FISH analysis for PDGFRA, PDGFRB, EGFR and KIT receptor tyrosine kinases (RTKs), together with immunoprecipitation/western blotting, sequencing of the corresponding genes, and the search for cognate ligands. The intimal sarcomas showed a wide spectrum of morphologies and immunophenotypes, whereas the mural sarcoma had common leiomyosarcomatous features. Regardless of their category, all of the cases had a PDGFRA-deregulated cytogenetic profile mainly consisting of an amplification cluster; five were also polysomic for PDGFRB, whereas three showed disomy. Six cases had a deregulated EGFR gene, and c-Kit gene status was similar to that of PDGFRA. In one case, biochemical analysis revealed the presence of activated and highly expressed PDGFRA, PDGFRB and EGFR, whereas KIT was expressed at reference level. Sequencing of the corresponding genes revealed no activating mutations in any of the analysed receptors. The cognate ligands were detected in all cases. In predictive terms, the evidence of gene amplification/high polysomy of several RTKs, together with PDGFRA, PDGFRB and EGFR expression and phosphorylation, suggests that these tumours may be sensitive to RTK-inhibiting treatments.

Increased expression of calpain 6 in uterine sarcomas and carcinosarcomas: an immunohistochemical analysis

Calpain 6 (Capn6) is one of the calcium-dependent intracellular nonlysosomal proteases. Recently, Capn6 was found to be overexpressed in leiomyosarcomas (LMSs) compared with normal myometrium. This investigation was performed to determine the expression of Capn6 in uterine sarcomas and carcinosarcomas and to determine whether there is a relationship between the clinical findings and the expression of Capn6. Seventeen cases, treated from 1994 to 2004, were evaluated. These included five LMS, seven endometrial stromal sarcomas, and five uterine carcinosarcomas (malignant mullerian mixed tumor [MMMT]). Formalin-fixed, paraffin-embedded tissue sections were immunostained with anti-Capn6 domain-II (anti-DII) and anti-Capn6 domain-T (anti-DT) antibodies. A semiquantitative assessment was performed. All 17 tumors expressed the Capn6 protein; this finding was in contrast to the absence of expression of the Capn6 protein in all of the normal control tissues. The distribution of staining was diffuse. The cytoplasm and nucleus were stained evenly. The mean age of the patients whose samples were stained strongly by anti-DII was higher (P= 0.031). There were no significant associations between tumor stage and staining intensity by anti-DII (P= 1.000) or anti-DT (P= 0.576). However, there was a marginally significant association between tumor subtype and staining intensity (P= 0.054 and P= 0.053, respectively). The expression of Capn6 had no association with disease-free survival (P= 0.367 and P= 0.166, respectively). All of the uterine sarcomas and MMMTs expressed Capn6 protein. This study showed that there were marginally significant associations between tumor subtypes and staining intensity, but no association was found with tumor stage and survival.

PDGFR-α as a potential therapeutic target in uterine sarcomas

OBJECTIVE

Uterine sarcomas are a heterogeneous group of tumors with a propensity for metastasis and resistance to conventional therapy. Recent success in the treatment of other solid tumors with the targeted tyrosine kinase inhibitor imatinib mesylate offers new avenues for investigation. The primary target of imatinib is c-kit, but the drug also inhibits PDGFR-alpha and PDGFR-beta. Given the lack of identified molecular targets in endometrial stromal sarcomas, leiomyosarcomas, and carcinosarcomas, the purpose of this study was to determine the protein expression of c-kit, PDGFR-alpha, and PDGFR-beta in these tumors as a preliminary step to determining their susceptibility to directed therapy. A secondary goal was to identify specific gene mutations that might be associated with activation of these proteins in uterine sarcomas.

METHODS

Archived tissue from 42 cases of uterine sarcomas was stained for c-kit, PDGFR-alpha, and PDGFR-beta using immunohistochemistry. Laser-capture microdissected samples of uterine carcinosarcomas, or homogeneous areas of leiomyosarcomas or endometrial stromal sarcomas, were subjected to genetic analysis of PDGFR-alpha exons 12 and 18.

RESULTS

The majority (38/42, 90%) of uterine sarcomas lacked c-kit expression and 90% (38/42) demonstrated negative or weak staining for PDGFR-beta. In contrast, 70% (30/42) of cases had strong staining for PDGFR-alpha in the tumor but not in normal myometrium or endometrium. Sequencing results revealed no mutations in exons 12 or 18 of PDGFR-alpha.

CONCLUSION

c-kit and PDGFR-beta are unlikely to represent primary treatment targets in uterine sarcomas. The strong expression of PDGFR-alpha in uterine sarcoma specimens suggests a role for this receptor in tumor development, although its potential as a therapeutic target requires further investigation.

TFE3 fusions activate MET signaling by transcriptional up-regulation, defining another class of tumors as candidates for therapeutic MET inhibition

Specific chromosomal translocations encoding chimeric transcription factors are considered to play crucial oncogenic roles in a variety of human cancers but the fusion proteins themselves seldom represent suitable therapeutic targets. Oncogenic TFE3 fusion proteins define a subset of pediatric renal adenocarcinomas and one fusion (ASPL-TFE3) is also characteristic of alveolar soft part sarcoma (ASPS). By expression profiling, we identified the MET receptor tyrosine kinase gene as significantly overexpressed in ASPS relative to four other types of primitive sarcomas. We therefore examined MET as a direct transcriptional target of ASPL-TFE3. ASPL-TFE3 binds to the MET promoter and strongly activates it. Likewise, PSF-TFE3 and NONO-TFE3 also bind this promoter. Induction of MET by ASPL-TFE3 results in strong MET autophosphorylation and activation of downstream signaling in the presence of hepatocyte growth factor (HGF). In cancer cell lines containing endogenous TFE3 fusion proteins, inhibiting MET by RNA interference or by the inhibitor PHA665752 abolishes HGF-dependent MET activation, causing decreased cell growth and loss of HGF-dependent phenotypes. MET is thus a potential therapeutic target in these cancers. Aberrant transcriptional up-regulation of MET by oncogenic TFE3 fusion proteins represents another mechanism by which certain cancers become dependent on MET signaling. The identification of kinase signaling pathways transcriptionally up-regulated by oncogenic fusion proteins may reveal more accessible therapeutic targets in this class of human cancers.

The inhibition of glutamine synthetase sensitizes human sarcoma cells to L-asparaginase

PURPOSE

To evaluate the activity of the antitumor enzyme L: -asparaginase (ASNase) on tumor cells of mesenchymal origin and the contribution of glutamine synthetase (GS) to the adaptation to the metabolic stress caused by the anti-tumor enzyme.

METHODS

We studied the effects of ASNase in six human sarcoma cell lines: HT1080 (fibrosarcoma); RD (rhabdomyosarcoma); SW872 (liposarcoma); HOS, SAOS-2, and U2OS (osteosarcoma) in the absence or in the presence of the GS inhibitor methionine L: -sulfoximine (MSO).

RESULTS

HT1080 and SW872 cells were highly sensitive to ASNase-dependent cytotoxicity. In contrast, RD, SAOS-2, HOS, and U2OS cells exhibited only a partial growth suppression upon treatment with the anti-tumor enzyme. In these cell lines ASNase treatment was associated with increased levels of GS. When ASNase was used together with MSO, the proliferation of the poorly sensitive cell lines was completely blocked and a significant decrease in the IC(50) for ASNase was observed. Moreover, when ASNase treatment was carried on in the presence of MSO, HOS and U2OS osteosarcoma cells exhibited a marked cytotoxicity, with increased apoptosis.

CONCLUSIONS

In human sarcoma cells (1) GS markedly contributes to the metabolic adaptation of tumor cells to ASNase and (2) the inhibition of GS activity enhances the antiproliferative and cytotoxic effects of ASNase. The two-step interference with glutamine metabolism, obtained through the combined treatment with ASNase and MSO, may provide a novel therapeutic approach that should be further investigated in human tumors of mesenchymal origin.

Wild-type p53 inhibits nuclear factor-kappaB-induced matrix metalloproteinase-9 promoter activation: implications for soft tissue sarcoma growth and metastasis

Human soft tissue sarcoma (STS) is a highly lethal malignancy in which control of metastasis determines survival. Little is known about the molecular determinants of STS dissemination. Here, we show that human STS express high levels of matrix metalloproteinase-9 (MMP-9) and that MMP-9 expression levels correlate with sequence analysis-defined p53 mutational status. Reintroduction of wild-type p53 (wtp53) into mutant p53 STS cell lines decreased MMP-9 mRNA and protein levels, decreased zymography-assessed MMP-9 proteolytic activity, and decreased tumor cell invasiveness. Reintroduction of wtp53 into STS xenografts decreased tumor growth and MMP-9 protein expression. Luciferase reporter studies showed that reintroduction of wtp53 into mutant p53 STS cells decreased MMP-9 promoter activity. Deletion constructs of the MMP-9 promoter identified a region containing a p53-responsive element that lacked a p53 consensus binding site but did contain a nuclear factor-kappaB (NF-kappaB) site. Mutating this NF-kappaB binding site eliminated the wtp53-repressive effect. Electrophoretic mobility shift assays confirmed decreased NF-kappaB binding in STS cells in the presence of wtp53. Our findings suggest a role for MMP-9 in STS progression and expand the role of p53 in molecular control of STS growth and metastasis. Therapeutic interventions in human STS targeting MMP-9 activity directly or via reintroduction of wtp53 merit further investigation.

Complete Regression of Large Solid Tumors Using Engineered Drug-Resistant Hematopoietic Cells and Anti-CD137 Immunotherapy

Combining chemotherapy and immunotherapy is problematic because chemotherapy can ablate the immune responses initiated by modulators of the immune system. We hypothesized that protection of immunocompetent cells from the toxic effects of chemotherapy, using drug resistance gene therapy strategies, would allow the combined use of chemotherapy and immunotherapy. In wild-type mice, the antitumor effectiveness of an immunotherapy regimen employing an agonistic anti-CD137 antibody is diminished with escalating doses of the antifolate trimetrexate (TMTX). Using retroviral gene transfer of a mutant form of dihydrofolate reductase (L22Y-DHFR), hematopoietic stem cells were genetically engineered to withstand the toxic effects of TMTX. Mice transplanted with L22Y-DHFR-modified bone marrow were then challenged with AG104 sarcoma cells and treated with TMTX only, anti-CD137 only, or a combination of chemotherapy and immunotherapy. Although tumor burden was transiently decreased during TMTX administration, no mice treated with TMTX alone survived the tumor challenge, whereas approximately 40% of transplanted mice treated with anti-CD137 alone survived. However, 100% of mice survived with complete tumor regression after transplantation with L22Y-DHFR-transduced bone marrow followed by combined treatment with TMTX and anti-CD137. In addition, adoptive transfer of splenocytes from cured mice extended the survival of tumor- bearing animals by approximately 3 weeks compared with controls. Therefore, protection of the hematopoietic system can allow for the combined administration of chemotherapy and immunotherapy, which results in complete tumor clearance.

Apoptosis induced by chemotherapeutic agents involves c-Jun N-terminal kinase activation in sarcoma cell lines

Molecular mechanisms underlying chemotherapeutic agent-induced apoptosis in sarcoma cells are not well known. Induction of apoptosis is regulated by several components including mitogen-activated protein kinases (MAPKs) comprising ERK, p38MAPKs, and c-Jun N-terminal kinase (JNK). In the present study, we examined whether activation of JNK is induced by the chemotherapeutic agents cis-diaminedichloroplatinum (cisplatin, CDDP) or doxorubicin (DXR), and whether the ectopic expression of constitutively active (MKK7-JNK1) or dominant-negative form of JNK (dnJNK) influenced apoptosis in response to the CDDP or DXR in sarcoma cell lines MG-63 and SaOS-2. The CDDP or DXR induced JNK activation in the both cell lines, as assessed by Western blotting using phosphospecific antibodies. A transient expression of the activated form of JNK sensitized the MG-63 and SaOS-2 cells to the drug-induced apoptosis, while dnJNK1 reduced the proportion of apoptotic cell death. Apoptosis was determined by flow cytometry using annexin-V Cy5. Collectively, our results indicate that JNK activation is involved in apoptotic cell death in sarcoma cell lines following stimulation with CDDP or DXR.

C-jun N-terminal kinase activation is required for apoptotic cell death induced by TNF-related apoptosis-inducing ligand plus DNA-damaging agents in sarcoma cell lines

BACKGROUND

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) in combination with a chemotherapeutic agent, cis-diammine dichloroplatinum (CDDP) or doxorubicin (DXR), has recently been demonstrated to result in enhanced apoptotic cell death in the sarcoma cell lines MG-63 and SaOS-2. DNA-damaging agents, such as CDDP induced sustained activation of c-Jun N-terminal kinase (JNK), probably leading to apoptosis. In the present study, whether JNK activation is involved in apoptotic cell death induced by combined treatment with CDDP/DXR and TRAIL was addressed.

RESULTS

MG-63 or SaOS-2 cells overexpressing the dominant-negative (dn) form of JNK (dnJNK1) were established by transfection with dnJNK1 cDNA. Following stimulation with the chemotherapeutic agent CDDP or TRAIL, both MG-63 and SaOS-2 cells demonstrated enhanced cell death compared with stimulation by either agent alone, as assayed for apoptosis using annexin V staining or mitochondrial membrane potential using DiOC6 staining. Interestingly, partial inhibition of the cell death induced by the combined treatment with CDDP/DXR and TRAIL was found in MG-63 or SaOS-2 cells overexpressing dnJNK1, suggesting that JNK activation is required for the combined treatment. Moreover, induction of caspase-8 activation by TRAIL or TRAIL plus CDDP/DXR was substantially prevented by dnJNK.

CONCLUSION

Efficient cell death induced by combined treatment with the chemotherapeutic agents CDDP/DXR and TRAIL is involved in JNK activation in the sarcoma cell lines MG-63 and SaOS-2. These results would be useful for treatment modalities of patients with sarcoma.

Gemcitabine resistance due to deoxycytidine kinase deficiency can be reverted by fruitfly deoxynucleoside kinase, DmdNK, in human uterine sarcoma cells

PURPOSE

Cytotoxic nucleoside analogues are widely used in the treatment of cancers. Resistance to these compounds is frequent and often multifactorial. Deficiency in deoxycytidine kinase (dCK), the rate-limiting activating enzyme, has been reported in a number of in vitro models as well as in various clinical situations. Some strategies to overcome this mechanism of resistance have been proposed there by gene transfer based therapy.

METHODS

We have developed and characterized a gemcitabine-resistant cell line (Messa 10 K) from the human uterine sarcoma Messa strain, and transfected this cell line with the multisubstrate deoxynucleoside kinase from Drosophila melanogaster (DmdNK) in order to revert the resistance in Messa 10 K cells which was due to dCK-deficiency.

RESULTS

Messa 10 K is highly resistant to gemcitabine (122-fold), troxacitabine (>15-fold) and araC (13,556-fold). Quantitative real-time PCR and western blot analysis showed that dCK was not detectable in Messa 10 K cells, presumably because of a genetic modification. The transfection of Messa 10 K cells with DmdNK significantly increased the sensitivity to gemcitabine.

CONCLUSIONS

These results show that genetic modifications in non-hematological malignant cells may be associated with resistance to gemcitabine, and that the gene transfer of non-human genes can be used for the reversion of nucleoside analogue resistance due to dCK deficiency.

Osteoclasts direct bystander killing of cancer cells in vitro

Cytosine deaminase (CD) catalyzes the deamination of 5-fluorocytosine (5FC) to produce the highly toxic chemotherapeutic agent 5-fluorouracil (5FU). A unique feature of the CD/5FC enzyme/prodrug system is its ability to kill adjacent cells via bystander killing. Bystander killing of cancer cells can be mediated by non-cancerous accessory cells transduced with the CD gene; one type of non-cancerous accessory cell found in primary bone cancer and breast cancer metastases to bone is the osteoclast. This manuscript determines if osteoclast precursor cells, transduced with the CD gene, can function as a gene delivery system capable of killing cancer cells. An osteoclast precursor cell line (RAW 264.7, RAW) and authentic bone marrow-derived osteoclast precursor cells were transduced with a retroviral vector containing the cytosine deaminase fusion gene (NCD) composed of the human nerve growth factor receptor and CD genes. RAW cells and bone marrow-derived osteoclast precursor cells transduced with NCD expressed NCD protein and converted 5FC to 5FU. Treatment of NCD-transduced osteoclast precursor cells with the 5FC prodrug resulted in significant killing in vitro. NCD-transduced osteoclasts were co-cultured with either DsRed2-labeled sarcoma cells (2472-DSR) or green fluorescent protein (GFP)-labeled breast cancer cells (GFP-4T1). Treatment of the NCD osteoclast/tumor cell co-cultures with 5FC resulted in bystander killing of 2472-DSR cells (P < 0.006) and GFP-4T1 cells (P < 0.004). These findings demonstrate that NCD-transduced osteoclasts can promote killing of cancer cells and introduce the exciting possibility for developing osteoclast-mediated, CD-based treatment of primary bone cancers and breast cancer metastases to bone.

Expression of transcription factor E2F1 and telomerase in glioblastomas: mechanistic linkage and prognostic significance

BACKGROUND

Several tumor suppressor pathways have been identified as modulators of telomerase function. We examined the functional role of the retinoblastoma-E2F1 pathway in regulating telomerase activity in malignant gliomas.

METHODS

Adenovirus vectors were used to transfer cDNAs into human glioblastoma and sarcoma cells. Telomerase activity was assessed with a telomere repeat amplification protocol. Promoter activity in cancer cells was assessed with promoter-luciferase reporter constructs. Promoter binding was assessed with the chromatin immunoprecipitation (ChIP) assay. We isolated astrocytes from E2F1 transgenic mice and normal mice for in vivo studies. We evaluated the expression of E2F1 and hTERT (the catalytic subunit of human telomerase) mRNAs by reverse transcriptase-polymerase chain reaction and proteins in human glioblastoma samples by immunoblot analysis. Associations between survival among 61 glioblastoma multiforme patients and expression of E2F1 and hTERT mRNA and protein were examined with Kaplan-Meier analysis, the log-rank test, and Cox proportional hazards regression models. All statistical tests were two-sided.

RESULTS

Ectopic E2F1 expression increased hTERT promoter activity in cancer cells. We detected an interaction between E2F1 protein and the hTERT promoter. Transgenic E2F1 astrocytes contained functional telomerase protein. E2F1 mRNA expression and hTERT mRNA expression were statistically significantly correlated in human glioblastoma specimens (R = .8; P < .001). Longer median survival was statistically significantly associated with lower E2F1 mRNA expression in tumors (103.6 weeks) rather than with higher expression (46.1 weeks) (difference = 57.5 weeks; 95% confidence interval [CI] = 14.7 to 159.7; log-rank P = .002). E2F1 mRNA was the only factor that was statistically significantly associated with overall survival in a multivariable model (P = .04). Among 27 patients with glioblastoma multiforme samples, the expression of E2F1 protein was statistically significantly associated with survival (log-rank P < .001).

CONCLUSIONS

E2F1 may participate in telomerase activity regulation in malignant glioma cells. Its expression appears to be strongly associated with the survival of patients with malignant brain tumors.

Telomerase activity with concurrent loss of cell cycle regulation in feline post-traumatic ocular sarcomas

Paraffin wax-embedded ocular globes of cats with post-traumatic ocular sarcomas were examined for the presence of TERT, the active subunit of telomerase. The latter is a ribonucleoprotein complex essential for immortalization and expressed by most malignant tumours, germ line cells, lens epithelial cells, and some stem cells. Due to the frequent loss of cell cycle control with the increased expression of telomerase activity, post-traumatic ocular sarcomas were also examined for loss of p16 expression and alterations in p53, the findings being related to mitotic score, tumour grade, and proliferating cell nuclear antigen. These sarcomas expressed telomerase at a high frequency (62.5%); in addition, the majority showed alterations in cell cycle control, as evaluated by lack of p16 immunolabelling (66.7%). Alterations in p53 were the sole mechanism by which cell cycle control was dysregulated in only two tumours expressing TERT (13%). These findings suggest that p16, and not p53, represents the primary mechanism by which post-traumatic ocular sarcomas that express telomerase activity escape cell cycle control.