Wild type p53 sensitizes soft tissue sarcoma cells to doxorubicin by down-regulating multidrug resistance-1 expression

Genetic and Epigenetic Characterization of Sarcoma Stem Cells Across Subtypes Identifies EZH2 as a Therapeutic Target

High-grade complex karyotype soft tissue sarcomas (STS) are a heterogeneous and aggressive set of cancers that share a common treatment strategy. Disease progression and failure to respond to anthracycline based chemotherapy, standard first-line treatment, is associated with poor patient outcomes. To address this, we investigated the contribution of STS cancer stem cells (STS-CSCs) to doxorubicin resistance. We identified a positive correlation between CSC abundance and doxorubicin IC 50 in resistant cell lines. We investigated if a common genetic signature across STS-CSCs could be targeted. Utilizing patient derived samples from five sarcoma subtypes we identified Enhancer of Zeste homolog 2 (EZH2), a member of the polycomb repressive complex 2 (PRC2) responsible for H3K27 methylation as being enriched in the CSC population. EZH2 activity and a shared epigenetic profile was observed across subtypes. Targeting of EZH2 using Tazemetostat, an FDA approved inhibitor specifically ablated the STS-CSC population. Treatment of doxorubicin resistant cell lines with tazemetostat resulted in a decrease in the STS-CSC population. Further, co-treatment was not only synergistic in the parent cell lines, but restored chemosensitivity in doxorubicin resistant lines. These data confirm the presence of shared genetic programs across distinct subtypes of CSC-STS that can be therapeutically targeted.

The biology and treatment of leiomyosarcomas

Leiomyosarcoma (LMS) is a soft tissue sarcoma of smooth muscle origin that can arise in multiple anatomical sites and is broadly classified as extra-uterine LMS or uterine LMS. There is substantial interpatient heterogeneity within this histological subtype, and despite multi-modal therapy, clinical management remains challenging with poor patient prognosis and few new therapies available. Here we discuss the current treatment landscape of LMS in both the localised and advanced disease setting. We further describe the latest advances in our evolving understanding of the genetics and biology of this group of heterogeneous diseases and summarise the key studies delineating the mechanisms of acquired and intrinsic chemotherapy resistance in this histological subtype. We conclude by providing a perspective on how novel targeted agents such as PARP inhibitors may usher in a new paradigm of biomarker-driven therapies that will ultimately impact the outcomes of patients with LMS.

Soft Tissue Sarcoma Study: Association of Genetic Alterations in the Apoptosis Pathways with Chemoresistance to Doxorubicin

Simple Summary

Genotoxic chemotherapy is the main component of the treatment for advanced soft tissue sarcomas. However, its efficacy is rather low and it is followed by rapid appearance of drug resistance. Our study was directed to the search of molecular drivers of chemoresistance in synovial and undifferentiated pleomorphic sarcomas to genotoxic drugs mostly used for their treatment. Using primary cell cultures obtained from sarcomas after surgery, we estimated their chemoresistance in vitro and performed exome sequencing. We revealed that cancer cells of more than one quarter of patients had molecular alterations preventing apoptosis and observed an association between molecular alterations found and chemoresistance to Doxorubicin, but not to Ifosfamide or Gemcitabine and Docetaxel. Information concerning the peculiar drivers of individual drug resistance could help to improve personalized chemotherapy by withdrawal from an inefficient drug or by targeting the revealed mechanism of chemoresistance.

Abstract

Soft tissue sarcomas (STS) are heterogeneous cancers with more than 100 histological subtypes, different in molecular alterations, which make its personalized therapy very complex. Gold standard of chemotherapy for advanced STS includes combinations of Doxorubicin and Ifosfamide or Gemcitabine and Docetaxel. Chemotherapy is efficient for less than 50% of patients and it is followed by a fast development of drug resistance. Our study was directed to the search of genetic alterations in cancer cells associated with chemoresistance of undifferentiated pleomorphic and synovial sarcomas to the abovementioned genotoxic drugs. We analyzed chemoresistance of cancer cells in vitro using primary STS cultures and performed genetic analysis for the components of apoptotic signaling. In 27% of tumors, we revealed alterations in TP53, ATM, PIK3CB, PIK3R1, NTRK1, and CSF2RB. Cells from STS specimens with found genetic alterations were resistant to Dox, excluding the only one case when TP53 mutation resulted in the substitution Leu344Arg associated with partial oligomerization loss and did not cause total loss of TP53 function. Significant association between alterations in the components of apoptosis signaling and chemoresistance to Dox was found. Our data are important to elaborate further the therapeutic strategy for STS patients with alterations in apoptotic signaling.

Construction of GSH-triggered cationic fluoropolymer as two-in-one nanoplatform for combined chemo/gene therapy

The combined chemo-gene therapy has become a promising approach for enhanced anti-cancer treatment. However, effective co-delivery of therapeutic gene and drug into target cells and tissues remains a major obstacle....

Biological indicators of chemoresistance: an ex vivo analysis of γH2AX and p53 expression in feline injection-site sarcomas

Background

The response of soft tissue sarcomas to cytotoxic chemotherapy is inconsistent. Biomarkers of chemoresistance or chemosensitivity are needed in order to identify appropriate patients for treatment. Given that many chemotherapeutics kill cells through direct DNA interactions, we hypothesized that upregulation of DNA damage response mechanisms would confer resistance to cytotoxic chemotherapy in sarcomas. To study this, we used spontaneously-occurring feline injection-site sarcomas (FISS).

Methods

γH2AX and p53 expression were determined in biopsy samples of FISS. γH2AX expression was determined via immunohistochemistry whereas p53 expression was determined via qRT-PCR. Cell lines derived from these sarcoma biopsies were then treated with carboplatin (N = 11) or doxorubicin (N = 5) and allowed to grow as colonies. Colony forming-ability of cells exposed to chemotherapy was compared to matched, untreated cells and expressed as percent survival relative to controls. ImageJ was used for quantification. A mixed model analysis was performed to determine if an association existed between relative survival of the treated cells and γH2AX or p53 expression in the original tumors. Cell lines were validated via vimentin expression or growth as subcutaneous sarcomas in nude mice.

Results

An association was detected between γH2AX expression and relative survival in cells exposed to carboplatin (P = 0.0250). In the 11 FISS tumors evaluated, γH2AX expression ranged from 2.2 to 18.8% (mean, 13.3%). Cells from tumors with γH2AX expression higher than the sample population mean had fourfold greater relative survival after carboplatin exposure than cells from tumors with γH2AX expression less than the mean. There was no association between relative survival after carboplatin exposure and p53 expression (P = 0.1608), and there was no association between relative survival after doxorubicin exposure and either γH2AX (P = 0.6124) or p53 (P = 0.8645) expression. Four cell lines were validated via growth as sarcomas in nude mice. Vimentin expression was confirmed in the other 7 cell lines.

Conclusions

γH2AX expression, but not wild type p53, may potentially serve as a biomarker of resistance to platinum therapeutics in soft tissue sarcomas. To further investigate this finding, prospective, in vivo studies are indicated in animal models.

A DNA-Based Nanocarrier for Efficient Gene Delivery and Combined Cancer Therapy

The efficient delivery of a therapeutic gene into target tissues has remained a major obstacle in realizing a viable gene-based medicine. Herein, we introduce a facile and universal strategy to construct a DNA nanostructure-based codelivery system containing a linear tumor therapeutic gene (p53) and a chemotherapeutic drug (doxorubicin, DOX) for combined therapy of multidrug resistant tumor (MCF-7R). This novel codelivery system, which is structurally similar to a kite, is rationally designed to contain multiple functional groups for the targeted delivery and controlled release of the therapeutic cargoes. The self-assembled DNA nanokite achieves efficient gene delivery and exhibits effective inhibition of tumor growth in vitro and in vivo without apparent systemic toxicity. These structurally and chemically well-defined codelivery nanovectors provide a new platform for the development of gene therapeutics for not only cancer but also a wide range of diseases.

Individualized doxorubicin sensitivity testing of undifferentiated soft tissue sarcoma (USTS) in a patient-derived orthotopic xenograft (PDOX) model demonstrates large differences between patients

Doxorubicin (DOX) is often first-line treatment of undifferentiated/unclassified soft tissue sarcoma (USTS). However, the DOX response rate for USTS patients is low. Individualized precision-medicine technology that could identify DOX responders as well as non-responders would be of high value to cancer patients. In the present study, we established 5 patient-derived orthotopic xenograft (PDOX) nude mouse models from 5 USTS patients and evaluated the efficacy of DOX in each PDOX model. USTS's were grown orthotopically in the right thigh of nude mice to establish the PDOX models. Two weeks after implantation, the mouse models were randomized into two groups of 8 mice each: untreated control; and DOX (3 mg/kg, i.p., once a week for 2 weeks). DOX showed significant growth inhibition in only 2 USTS PDOX models out of 5 (p = 0.0054, p = 0.0055, respectively) on day 14 after initiation. DOX was ineffective in the other 3 PDOX models. However, even in the DOX-sensitive cases, DOX could not regress the PDOX tumors responding to treatment. The present study has important implications since this is the first in vivo study to compare the DOX sensitivity for USTS on multiple patient tumors. We showed that only two of five USTS were responsive to DOX, despite DOX being first line chemotherapy for USTS. The 3 resistant cases should not be treated with DOX clinically, in order to spare the patients' unnecessary toxicity. This PDOX model is useful for precise individualized drug sensitivity testing, especially for rare heterogeneous recalcitrant sarcomas such as USTS.

Modulatory effects of green tea extract against the hepatotoxic effects of 4-nonylphenol in catfish (Clarias gariepinus)

The antioxidant role of the green tea (Camellia sinensis) extract (GTE) was examined to remedy the toxic effects of (0.2mgl^-1) 4-nonylphenol(4-NP). Biochemical parameters, antioxidant enzymes, liver lipid peroxidation (LPO), DNA fragmentation, and apoptosis as well as histopathology of liver of African catfish Clarias gariepinus were considered. Catfishes were divided into four groups: first group (control), second group (0.2mgl^-1 of 4-NP), third group (0.2mgl^-1of 4-NP +100mg GTE l^-1water), and fourth group (0.2mgl^-1 of 4-NP +200mg GTE l^-1water). The results showed that significant increments of serum glucose, AST, ALT, total protein, total lipids, cholesterol, G6PDH, and cortisol. Meanwhile, serum acetylcholinesterase, ALP, and LDH were significantly reduced. In addition, antioxidant enzymes (SOD, CAT, GST, and TAC) levels were reduced in 4-NP treated fish compared to control. Also, there were significant increments in hepatic LPO, DNA fragmentation, and apoptotic erythrocytes in 4-NP treated fish compared to control. Liver of 4-NP treated fish showed some histopathological alterations such as, vacuolization in hepatocytes, congestion in central vein, infiltration of mononuclear inflammatory cells, and necrosis as well as depletion of glycogen content of liver. Addition of green tea extract into the water restored the alterations in most of those biomarkers induced by 4-NP. We concluded that, GTE has a protective role against hepatic failure, depletion of antioxidant defense, and genotoxicity induced 4-NP in C. gariepinus.

Cepharanthine hydrochloride reverses the mdr1 (P-glycoprotein)-mediated esophageal squamous cell carcinoma cell cisplatin resistance through JNK and p53 signals

Esophageal squamous cell carcinoma (ESCC) is an aggressive malignancy that is often resistant to therapy. Nowadays, chemotherapy is still one of the main methods for the treatment of ESCC. However, the multidrug resistance (MDR)-mediated chemotherapy resistance is one of the leading causes of death. Exploring agents able to reverse MDR, which thereby increase the sensitivity with clinical first-line chemotherapy drugs, could significantly improve cancer treatment. Cepharanthine hydrochloride (CEH) has the ability to reverse the MDR in ESCC and the mechanism involved have not been reported. The aim of the study was to investigate the potential of CEH to sensitize chemotherapeutic drugs in ESCC and explore the underlying mechanisms by in vitro and in vivo studies. Our data demonstrated that CEH significantly inhibited ESCC cell proliferation in a dose-dependent manner, induced G2/M phase cell cycle arrest and apoptosis, and increased the sensitivity of cell lines resistant to cisplatin (cDDP). Mechanistically, CEH inhibited ESCC cell growth and induced apoptosis through activation of c-Jun, thereby inhibiting the expression of P-gp, and enhancing p21 expression via activation of the p53 signaling pathway. In this study, we observed that growth of xenograft tumors derived from ESCC cell lines in nude mice was also significantly inhibited by combination therapy. To our knowledge, we demonstrate for the first time that CEH is a potentially effective MDR reversal agent for ESCC, based on downregulation of the mRNA expression of MDR1 and P-gp. Together, these results reveal emphasize CEH putative role as a resistance reversal agent for ESCC.

Adipose-Induced Retroperitoneal Soft Tissue Sarcoma Tumorigenesis: A Potential Crosstalk between Sarcoma and Fat Cells

Previous data demonstrated that high retroperitoneal visceral fat content increases retroperitoneal soft-tissue sarcoma (RSTS) local recurrence and patients' mortality. Most RSTS tumors initiate and recur within visceral fat. The objective of the current study was to evaluate potential paracrine effects of visceral fat on RSTS. A xenograft model was used to evaluate in vivo effects of human visceral fat on STS growth. Tissue explants were prepared from visceral fat, and their conditioned medium (CM) was utilized for various in vitro experiments designed to evaluate growth, survival, migration, and invasion of STS and endothelial cells. Visceral fat-secreted protumorigenic factors were identified by mass spectrometry. The in vivo experiments demonstrated a significant increase in STS tumor growth rate when SK-LMS-1 leiomyosarcoma cells were colocalized with human visceral fat compared with subcutaneous injection of cancer cells only. The in vitro model demonstrated that visceral fat CM increased STS cellular growth and reduced doxorubicin-induced apoptosis. Visceral fat also enhanced STS cellular migration and invasion. In addition, visceral fat CM significantly increased endothelial cell tube formation, suggesting its role as a proangiogenic factor in the STS tumor microenvironment (TME). Using a robust proteomic approach, liquid chromatography and tandem mass spectrometry resolved various molecules within the visceral fat CM, of which a subset was associated with protumorigenic biologic processes. These results suggest that visceral fat directly interacts with STS cells by secreting specific adipokines into the TME, thus augmenting STS tumor cell proliferation and invasiveness. Fat-induced STS molecular deregulations should be studied to identify new potential prognostic and therapeutic targets.

IMPLICATIONS

Visceral fat induces protumorigenic effects, in STS, through various secreted factors that should be investigated to improve our understanding of adipose-cancer cell interactions. Mol Cancer Res; 14(12); 1254-65. ©2016 AACR.

Inhibition of Bcl-2 family members sensitises soft tissue leiomyosarcomas to chemotherapy

Background:

Leiomyosarcoma is an aggressive soft tissue sarcoma with a 5-year survival rate of 15 to 60%. Treatment options for inoperable or metastatic patients are limited owing to frequent resistance of tumours to chemotherapy and radiation. In this study, we hypothesised that antiapoptotic Bcl-2 family proteins might contribute to leiomyosarcoma chemoresistance and therefore inhibition of Bcl-2 family proteins might sensitise leiomyosarcomas to conventional chemotherapy.

Methods:

Expression of the Bcl-2 family proteins Bcl-xL, Bcl-w and Bcl-2 was investigated using immunohistochemistry on a tissue microarray containing 43 leiomyosarcomas. Furthermore, we investigated whether ABT-737, a potent BH3 mimetic, sensitises leiomyosarcoma cells to doxorubicin treatment in vitro.

Results:

Seventy-seven per cent, 84% and 42% of leiomyosarcomas demonstrated high expression of Bcl-2, Bcl-xL and Bcl-w, respectively. Single-agent treatment with ABT-737 resulted in a minor reduction of cell viability. However, combination treatment of ABT-737 and doxorubicin revealed synergism in all four cell lines, by inducing apoptosis.

Conclusions:

In conclusion, Bcl-2 family proteins contribute to soft tissue leiomyosarcoma chemoresistance. Antiapoptotic proteins are highly expressed in leiomyosarcoma of soft tissue, and inhibition of these proteins using a BH3 mimetic increases leiomyosarcoma sensitivity to doxorubicin.

Cancer chemoresistance; biochemical and molecular aspects: a brief overview

The effectiveness of chemotherapy is one of the main challenges in cancer treatment and resistance to classic drugs and traditional treatment processes is an obstacle to this goal. Drug resistance that may be inherent or adventitious can cause poor treatment outcome and tumor relapse. In most cases, resistance to a drug can lead to resistance to many other drugs structure and function of which is not necessarily similar to the first drug. This phenomenon is the main mechanism behind failure of many of metastatic cancers. There are various molecular mechanisms involved in multidrug resistance, including change in the activity of membrane transporters (such as ABC transporters), increase of drug metabolism, change of the target enzyme (such as mutations that change thymidylate synthase and topoisomerases), promotion of DNA damage repair, and escape from drug induced apoptosis. Clinical and laboratory investigations on biomarkers involved in the response to chemotherapy have characterized the key factors behind the failure of treatments. Knowing the molecular factors involved in drug resistance may help us to develop new strategies for more promising chemotherapy and reduce the rate of relapse. In this brief review, molecular mechanisms and tumor microenvironment leading to decreased drug sensitivity, and strategies of reversing drug resistance are described.

Hitting the Bull's-Eye in Metastatic Cancers-NSAIDs Elevate ROS in Mitochondria, Inducing Malignant Cell Death

Tumor metastases that impede the function of vital organs are a major cause of cancer related mortality. Mitochondrial oxidative stress induced by hypoxia, low nutrient levels, or other stresses, such as genotoxic events, act as key drivers of the malignant changes in primary tumors to enhance their progression to metastasis. Emerging evidence now indicates that mitochondrial modifications and mutations resulting from oxidative stress, and leading to OxPhos stimulation and/or enhanced reactive oxygen species (ROS) production, are essential for promoting and sustaining the highly metastatic phenotype. Moreover, the modified mitochondria in emerging or existing metastatic cancer cells, by their irreversible differences, provide opportunities for selectively targeting their mitochondrial functions with a one-two punch. The first blow would block their anti-oxidative defense, followed by the knockout blow—promoting production of excess ROS, capitulating the terminal stage—activation of the mitochondrial permeability transition pore (mPTP), specifically killing metastatic cancer cells or their precursors. This review links a wide area of research relevant to cellular mechanisms that affect mitochondria activity as a major source of ROS production driving the pro-oxidative state in metastatic cancer cells. Each of the important aspects affecting mitochondrial function are discussed including: hypoxia, HIFs and PGC1 induced metabolic changes, increased ROS production to induce a more pro-oxidative state with reduced antioxidant defenses. It then focuses on how the mitochondria, as a major source of ROS in metastatic cancer cells driving the pro-oxidative state of malignancy enables targeting drugs affecting many of these altered processes and why the NSAIDs are an excellent example of mitochondria-targeted agents that provide a one-two knockout activating the mPTP and their efficacy as selective anticancer metastasis drugs.

Codelivery of antitumor drug and gene by a pH-sensitive charge-conversion system

In the present study, a gene and drug codelivery system was developed by electrostatic binding of polyethylenimine-poly(l-lysine)-poly(l-glutamic acid) (PELG), polyethylenimine (PEI), cis-aconityl-doxorubicin (CAD), and DNA. Zeta potential and drug release analysis confirmed the pH-responsive charge conversion and acid-sensitive drug release functional properties of the PELG/PEI/(DNA+CAD) system. Gel retardation assay and transfection experiment showed the codelivery system had effective DNA binding ability and good transfection efficiency on HepG2 cells. The therapeutic gene p53 was further employed to study its combinational effects with CAD. Cytotoxicity assay showed the half inhibitory concentration (IC50) of the PELG/PEI/(p53+CAD) codelivery system was lower than that of the gene or the drug delivery system. Confocal laser scanning microscopy (CLSM) showed that the drug and gene could be delivered into the cells simultaneously. A significant increase of p53 gene expression was achieved after HepG2 cells treated by PELG/PEI/(p53+CAD) codelivery system. The apoptosis experiment indicated clearly that the codelivery system could lead an effective apoptosis on tumor cells, which was beneficial for the treatment of cancer. The biodistribution and tumor accumulation of the codelivery system was explored via in vivo imaging in subcutaneous xenograft and in situ tumor models. The tumor and some major organs were excised and imaged, and the results showed that the codelivery system can accumulate efficiently in tumor for both tumor models. It can be suggested from the above results that the PELG/PEI/(DNA+CAD) codelivery system will have great potential applications in cancer therapy.

Alginate/CaCO3 hybrid nanoparticles for efficient codelivery of antitumor gene and drug

In this study, a facile strategy for efficient codelivery of gene and drug was developed. Using a coprecipitation method, doxorubicin hydrochloride (DOX), an antitumor drug, and p53 expression plasmid were encapsulated in alginate/CaCO(3)/DNA/DOX nanoparticles with high encapsulation efficiency. The in vitro cell inhibition effect of the alginate/CaCO(3)/DNA/DOX nanoparticles was evaluated by MTT assay in HeLa cells. The alginate/CaCO(3)/DNA/DOX nanoparticles exhibited a high cell inhibition rate about 80%, indicating that the alginate/CaCO(3)/DNA/DOX nanoparticles could effectively mediate gene transfection and deliver the drug to the cells. Compared with the codelivery of gene and drug, the treatments by alginate/CaCO(3)/DOX nanoparticles and alginate/CaCO(3)/DNA nanoparticles separately led to much lower cell inhibition rates. Compared with the CaCO(3)/DNA/DOX nanoparticles without alginate modification, the alginate/CaCO(3)/DNA/DOX nanoparticles with a decreased particle size exhibited enhanced delivery efficiency. The alginate/CaCO(3)/DNA/DOX nanoparticles have promising applications in cancer treatments.

Pleomorphic liposarcoma: clinical observations and molecular variables

BACKGROUND

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

METHODS

Medical records from patients (n = 155) who had PLS from 1993 to 2010 were reviewed. Univariate and multivariate analyses were conducted to identify independent prognosticators. A PLS tissue microarray (TMA) (n = 56 patient specimens) was constructed for immunohistochemical analysis of molecular markers, and p53 gene sequencing (exons 5-9) was conducted.

RESULTS

The average patient age was 57 years, and the patients presented with primary disease (n = 102), recurrent disease (n = 16), and metastatic disease (n = 37). Lower extremity was the most common disease site (40%), and the average tumor size was 11 cm. Complete follow-up data were available for 83 patients, and their median follow-up was 22.6 months. The 5-year disease-specific survival rate was 53%; and recurrent disease, unresectability, and microscopic positive margins were identified as predictors of a poor prognosis. Systemic relapse (the strongest poor prognostic determinant) developed in 35% of patients with localized PLS. Immunohistochemical analysis revealed increased expression of peroxisome proliferator-activated receptor gamma (an adipogenic marker), B-cell leukemia 2 and survivin (survival factors), vascular endothelial growth factor (an angiogenic factor), matrix metalloproteinase 2, and other biomarkers. Frequent loss of retinoblastoma protein expression and high p53 mutation rates (approximately 60%) were observed.

CONCLUSIONS

PLS is an aggressive, metastasizing sarcoma. Identifying ubiquitous molecular events underlying PLS progression is crucial for progress in patient management and outcomes.

The histone deacetylase inhibitor vorinostat selectively sensitizes fibrosarcoma cells to chemotherapy

Soft tissue sarcoma (STS) is a rare malignancy that is generally resistant to chemotherapy. We investigated the ability of the histone deacetylase inhibitor vorinostat to sensitize STS cells versus normal fibroblasts to chemotherapy. Fibrosarcoma, leiomyosarcoma, and liposarcoma cells and normal fibroblasts were treated with vorinostat to determine effects on proliferation and basal apoptosis as measured by total cell number and cleaved caspase 3 staining. Effects on histone deacetylases (HDAC) activity were confirmed by Western blotting for acetylated histone H3. A clinically relevant dose of vorinostat that had no effect on basal apoptosis was selected to examine altered sensitivity to doxorubicin. The effects of vorinostat, doxorubicin, or the combination on fibrosarcoma growth in vivo were determined in a xenograft model. Tumor volume was measured biweekly and HDAC activity and cell death were assessed by immunohistochemical analysis of acetylated histone H3, cleaved caspase 3, and TUNEL staining. Vorinostat inhibited proliferation and induced histone acetylation without affecting basal apoptosis levels. Combined treatment with vorinostat and doxorubicin synergistically induced apoptosis in vitro in fibrosarcoma but not leiomyosarcoma, liposarcoma, or normal fibroblasts. In nude mice, the combination of vorinostat and doxorubicin inhibited fibrosarcoma xenograft growth further than either agent alone. Cell death, as measured by cleaved caspase 3 and TUNEL staining, was greatest in xenografts from mice treated with vorinostat and doxorubicin. Vorinostat inhibits growth and induces chemosensitivity in fibrosarcoma cells in vitro and in vivo, suggesting that the combination of vorinostat and chemotherapy may represent a novel treatment option for this STS subtype. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29:623-632, 2011.

New frontiers in the treatment of liposarcoma, a therapeutically resistant malignant cohort

The adipogenic origin-derived liposarcoma (LPS) family is the most common soft tissue sarcoma histological subtype. This group is composed of three categories as per the 2002 WHO guidelines: (1) well-differentiated and dedifferentiated liposarcoma (WDLPS/DDLPS); (2) myxoid and round cell liposarcoma (MLS and RCL); and (3) pleomorphic liposarcoma (PLS). While clustered together, these histological subtypes are widely diverse in their clinical, pathological, and molecular characteristics. In general, surgery still remains the mainstay of LPS therapy and the only approach offering the potential of cure. Effective therapeutic strategies for locally advanced and metastatic disease are currently lacking and are crucially needed. With the current gradually increasing knowledge of LPS genetic- and epigenetic-associated deregulations, the ultimate goal is to develop drugs that can specifically eliminate LPS cells while sparing normal tissues. This tumor-tailored target-orientated approach will hopefully result in a significant improvement in the outcome of patients suffering from these poor prognosis malignancies.

Wide-spectrum characterization of trabectedin: biology, clinical activity and future perspectives

Ecteinascidin-743 (trabectedin, Yondelis®; PharmaMar, Madrid, Spain), a 25-year-old antineoplastic alkylating agent, has recently shown unexpected and interesting mechanisms of action. Trabectedin causes perturbation in the transcription of inducible genes (e.g., the multidrug resistance gene MDR1) and interaction with DNA repair mechanisms (e.g., the nucleotide excision repair pathway) owing to drug-related DNA double strand breaks and adduct formation. Trabectedin was the first antineoplastic agent from a marine source (namely, the Caribbean tunicate Ecteinascidia turbinata) to receive marketing authorization. This article summarizes the mechanisms of action, the complex metabolism, the main toxicities, the preclinical and clinical evidences of its antineoplastic effects in different types of cancer and, finally, the future perspectives of this promising drug.

TRAIL and doxorubicin combination induces proapoptotic and antiangiogenic effects in soft tissue sarcoma in vivo

PURPOSE

Novel therapeutic approaches for complex karyotype soft tissue sarcoma (STS) are crucially needed. Consequently, we assessed the efficacy of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), in combination with chemotherapy, on local and metastatic growth of human STS xenografts in vivo.

EXPERIMENTAL DESIGN

TRAIL was evaluated alone and combined with low-dose doxorubicin in two human STS severe combined immunodeficient mouse xenograft models using fibrosarcoma (HT1080; wild-type p53) and leiomyosarcoma (SKLMS1; mutated p53), testing for effects on local growth, metastasis, and overall survival. Magnetic resonance imaging was used to evaluate local growth and bioluminescence was used to longitudinally assess lung metastases. Tissues were evaluated through immunohistocemistry and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling staining for treatment effects on tumor cell proliferation, apoptosis, angiogenesis, angiogenic factors, and TRAIL receptor expression. Quantitative real-time polymerase chain reaction (QRTPCR) angiogenesis array was used to assess therapy-induced gene expression changes.

RESULTS

TRAIL/doxorubicin combination induced marked STS local and metastatic growth inhibition in a p53-independent manner. Significantly increased (P < 0.001) host survival was also demonstrable. Combined therapy induced significant apoptosis, decreased tumor cell proliferation, and increased TRAIL receptor (DR4 and DR5) expression in all treated tumors. Moreover, decreased microvessel density was observed, possibly secondary to increased expression of the antiangiogenic factor CXCL10 and decreased proangiogenic interleukin-8 cytokine in response to TRAIL/doxorubicin combination, as was also observed in vitro.

CONCLUSIONS

Given the urgent need for better systemic approaches to STS, clinical trials evaluating TRAIL in combination with low-dose chemotherapy are potentially warranted.

Structural biology of the tumor suppressor p53 and cancer-associated mutants

The tumor suppressor protein p53 is a transcription factor that plays a key role in the prevention of cancer development. In response to oncogenic or other stresses, the p53 protein is activated and regulates the expression of a variety of target genes, resulting in cell cycle arrest, senescence, or apoptosis. Mutation of the p53 gene is the most common genetic alteration in human cancer, affecting more than 50% of human tumors. Most of these mutations inactivate the DNA-binding domain of the protein. In this chapter, we describe the structure of the wild-type p53 protein and present structural and functional data that provide the molecular basis for understanding the effects of common cancer mutations. Further, we assess novel therapeutic strategies that aim to rescue the function of p53 cancer mutants.

Combining PCI-24781, a novel histone deacetylase inhibitor, with chemotherapy for the treatment of soft tissue sarcoma

PURPOSE

Histone deactylase inhibitors (HDACi) are a promising new class of anticancer therapeutics; however, little is known about HDACi activity in soft tissue sarcoma (STS), a heterogeneous cohort of mesenchymal origin malignancies. Consequently, we investigated the novel HDACi PCI-24781, alone/in combination with conventional chemotherapy, to determine its potential anti-STS-related effects and the underlying mechanisms involved.

EXPERIMENTAL DESIGN

Immunoblotting was used to evaluate the effects of PCI-24781 on histone and nonhistone protein acetylation and expression of potential downstream targets. Cell culture-based assays were utilized to assess the effects of PCI-24781 on STS cell growth, cell cycle progression, apoptosis, and chemosensitivity. Quantitative reverse transcription-PCR, chromatin immunoprecipitation, and reporter assays helped elucidate molecular mechanisms resulting in PCI-24781-induced Rad51 repression. The effect of PCI-24781, alone or with chemotherapy, on tumor and metastatic growth was tested in vivo using human STS xenograft models.

RESULTS

PCI-24781 exhibited significant anti-STS proliferative activity in vitro, inducing S phase depletion, G(2)/M cell cycle arrest, and increasing apoptosis. Superior effects were seen when combined with chemotherapy. A PCI-24781-induced reduction in Rad51, a major mediator of DNA double-strand break homologous recombination repair, was shown and may be a mechanism underlying PCI-24781 chemosensitization. We showed that PCI-24781 transcriptionally represses Rad51 through an E2F binding-site on the Rad51 proximal promoter. Although single-agent PCI-24781 had modest effects on STS growth and metastasis, marked inhibition was observed when combined with chemotherapy.

CONCLUSIONS

In light of these findings, this novel molecular-based combination may be applicable to multiple STS histologic subtypes, and potentially merits rigorous evaluation in human STS clinical trials.

Heterogeneous in vitro effects of doxorubicin on gene expression in primary human liposarcoma cultures

BACKGROUND

Doxorubicin is considered one of the most potent established chemotherapeutics in the treatment of liposarcoma; however, the response rates usually below 30%, are still disappointing. This study was performed to identify gene expression changes in liposarcoma after doxorubicin treatment.

METHODS

Cells of 19 primary human liposarcoma were harvested intraoperatively and brought into cell culture. Cells were incubated with doxorubicin for 24 h, RNA was isolated and differential gene expression was analysed by the microarray technique.

RESULTS

A variety of genes involved in apoptosis were up and down regulated in different samples revealing a heterogeneous expression pattern of the 19 primary tumor cell cultures in response to doxorubicin treatment. However, more than 50% of the samples showed up-regulation of pro-apoptotic genes such as TRAIL Receptor2, CDKN1A, GADD45A, FAS, CD40, PAWR, NFKBIA, IER3, PSEN1, RIPK2, and CD44. The anti-apoptotic genes TNFAIP3, PEA15, Bcl2A1, NGFB, and BIRC3 were also up-regulated. The pro-apoptotic CD14, TIA1, and ITGB2 were down-regulated in more than 50% of the tumor cultures after treatment with doxorubicin, as was the antiapoptotic YWHAH.

CONCLUSION

Despite a correlation of the number of differentially regulated genes to the tumor grading and to a lesser extent histological subtype, the expression patterns varied strongly; however, especially among high grade tumors the responses of selected apoptosis genes were similar. The predescribed low clinical response rates of low grade liposarcoma to doxorubicin correspond to our results with only little changes on gene expression level and also divergent findings concerning the up- and down-regulation of single genes in the different sarcoma samples.

Pancreatic cancer: from molecular pathogenesis to targeted therapy

Pancreatic cancer is a deadly malignancy with still high mortality and poor survival despite the significant advances in understanding, diagnosis, and access to conventional and novel treatments. Though cytotoxic chemotherapy based on the purine analogue gemcitabine remains the standard approach in adjuvant and palliative setting the need for novel agents aiming at the main pathophysiological abnormalities and molecular pathways involved remains soaring. So far, evidence of clinical benefit, though small, exists only from the addition of the targeted agent erlotinib on the standard gemcitabine chemotherapy. Apart from the popular monoclonal antibodies and small molecules tyrosine kinase inhibitors, other novel compounds being tested in preclinical and clinical studies target mTOR, NF-kappaB, proteasome and histone deacetylase. These new drugs along with gene therapy and immunotherapy, which are also under clinical evaluation, may alter the unfavorable natural course of this disease. In this review we present the main pathophysiological alterations met in pancreatic cancer and the results of the florid preclinical and clinical research with regards to the targeted therapy associated to these abnormalities.

Epidermal growth factor receptor blockade in combination with conventional chemotherapy inhibits soft tissue sarcoma cell growth in vitro and in vivo

PURPOSE

The epidermal growth factor receptor (EGFR) is highly expressed in many human soft tissue sarcomas (STS). However, EGFR blockade has not apparently been used for human STS therapy; therefore, we examined the in vitro and in vivo effects and the underlying mechanisms before considering EGFR blockade as a therapy for STS patients.

EXPERIMENTAL DESIGN

Human STS tissues and cell lines were used to study EGFR expression and activation. Western blot analysis was used to evaluate effects of EGFR activation on downstream signaling. Cell culture assays were used to assess the effect of EGF stimulation as well as EGFR blockade (using an EGFR tyrosine kinase inhibitor, Iressa; AstraZeneca) on STS cell growth, apoptosis, and chemosensitivity. An in vivo study (HT1080 human fibrosarcoma cell line in nude/nude mice: Iressa, doxorubicin, Iressa + doxorubicin, vehicle) was used to examine tumor growth; pEGFR, proliferating cell nuclear antigen, and terminal deoxyribonucleotide transferase-mediated nick-end labeling staining helped assess the effect of therapy in vivo on STS EGFR activation, proliferation, and apoptosis.

RESULTS

EGFR was expressed and activated in STS cell lines and tumors, probably due to ligand binding rather than EGFR mutation. Stimulation caused activation of AKT and mitogen-activated protein kinase pathways. EGFR blockade inhibited these effects and also caused increased apoptosis, a p53-independent G(0)-G(1) cell cycle arrest, and decreased cyclin D1 expression. In vivo, Iressa + doxorubicin had markedly synergistic anti-STS effects.

CONCLUSION

EGFR blockade combined with conventional chemotherapy results in anti-human STS activity in vitro and in vivo, suggesting the possibility that combining these synergistic treatments will improve anti-STS therapy.

Soft tissue sarcoma cells are highly sensitive to AKT blockade: a role for p53-independent up-regulation of GADD45 alpha

The AKT signaling pathway is activated in soft tissue sarcoma (STS). However, AKT blockade has not yet been studied as a potential targeted therapeutic approach. Here, we examined the in vitro and in vivo effects of AKT inhibition in STS cells. Western blot analysis was used to evaluate the expression of AKT pathway components and the effect of AKT stimulation and inhibition on their phosphorylation. Cell culture assays were used to assess the effect of AKT blockade (using a phosphatidylinositol 3-kinase inhibitor and a specific AKT inhibitor) on STS cell growth, cell cycle, and apoptosis. Oligoarrays were used to determine gene expression changes in response to AKT inhibition. Reverse transcription-PCR was used for array validation. Specific small inhibitory RNA was used to knockdown GADD45 alpha. Human STS xenografts in nude mice were used for in vivo studies, and immunohistochemistry was used to assess the effect of treatment on GADD45 alpha expression, proliferation, and apoptosis. Multiple STS cell lines expressed activated AKT. AKT inhibition decreased STS downstream target phosphorylation and growth in vitro; G(2) cell cycle arrest and apoptosis were also observed. AKT inhibition induced GADD45 alpha mRNA and protein expression in all STS cells treated independent of p53 mutational status. GADD45 alpha knockdown attenuated the G(2) arrest induced by AKT inhibition. In vivo, AKT inhibition led to decreased STS xenograft growth. AKT plays a critical role in survival and proliferation of STS cells. Modulation of AKT kinase activity may provide a novel molecularly based strategy for STS-targeted therapies.

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.

Irinotecan-induced apoptosis is inhibited by increased P-glycoprotein expression and decreased p53 in human hepatocellular carcinoma cells

Irinotecan, a DNA topoisomerase I inhibitor, is widely used in cancer chemotherapy. However, little is known of the mechanisms of its antitumor effects and the development of drug resistance in human hepatocellular carcinoma (HCC). In this study, we investigated the effects of short-term culture with SN-38, the active metabolite of irinotecan, on apoptosis in Huh7 cells. The cells were cultured with SN-38 for 24, 72, and 120 h, and apoptosis was determined using the terminal dUTP nick-end labeling (TUNEL) assay. The expressions of p53, apoptosis-related proteins, and P-glycoprotein (P-gp), a protein conferring the multidrug-resistant phenotype, were analyzed using Western blotting. Induced expression of P-gp was detected using fluorescence microscopy. SN-38 significantly induced apoptosis in Huh7 cells at 24 h. SN-38 also increased the expression of p53, Bax, and caspase-9 and decreased Bcl-xL expression in Huh7 cells. SN-38 decreased p53 expression and increased P-gp expression after 120 h, resulting in inhibition of apoptosis. This inhibition was reversed by the addition of verapamil to the culture medium during 120 h incubation. SN-38-induced P-gp expression was additionally enhanced by p53 decoy oligodeoxynucleotide. The changes in P-gp expression were directly moderated by p53 gene downregulation, suggesting that it plays a role in the mechanism of drug resistance. These results suggest that the accumulation of irinotecan in HCC leads to the development of drug resistance.

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.

High prevalence of p53 exon 4 mutations in soft tissue sarcoma

BACKGROUND

p53 is the most commonly mutated gene in cancer, including soft tissue sarcoma (STS). The authors characterized p53 alterations (protein accumulation and gene mutation) in STS to evaluate possible associations with patient outcomes.

METHODS

Thirty-one STS specimens (multiple histologies) were analyzed by p53 immunohistochemistry (IHC) and direct DNA sequencing of p53 exons 2-11 and then correlated with outcomes.

RESULTS

Direct p53 sequencing detected mutations in 10 of 31 STSs; 7 of 10 were missense mutations, whereas 3 of 10 were either insertions or frameshift mutations, leading to nonfunctional truncated p53; 7 of these p53 mutations have not been previously described. Four p53 exon 4 mutations were identified, a p53 region previously unknown to be mutation prone. Eighteen of the 31 specimens expressed p53 when the authors used the clinical IHC assay of their institution. Interassay concordance of 48% was observed; only 6 of 10 sequencing-identified p53 mutated specimens exhibited nuclear p53 protein expression by IHC, whereas 12 of 18 specimens exhibiting p53 protein expression by IHC harbored sequencing-identified wild-type p53. Decreased survival was observed in STS patients bearing sequencing-identified mutated p53 versus wild-type p53, as was a correlation between IHC-determined nuclear p53 protein expression and decreased survival.

CONCLUSIONS

p53 protein stabilization and p53 mutation frequently occur in STS, and both suggest worse outcomes for patients so affected. However, increased p53 protein expression does not necessarily indicate p53 gene mutation. The high incidence of exon 4 mutations found in STS suggests that p53 sequencing should not be limited to the core DNA binding domain.

Self-assembled polyethylenimine-graft-poly(epsilon-caprolactone) micelles as potential dual carriers of genes and anticancer drugs

A series of amphiphilic cationic graft polymers (PEC) were synthesized by coupling poly(epsilon-caprolactone) of differing molecular weights (MW) to low MW branched polyethylenimine via an amide group. IR, (1)H-NMR and GPC were employed to characterize the graft copolymers. The self-assembly characteristics of these copolymers in an aqueous solution were studied by fluorescence techniques. The critical micelle concentration (CMC) varied from 0.044 to 0.032g/L when the MW of poly(epsilon-caprolactone) increased from 1,800 to 5,500. The micelles formed electrostatic complexes with a reporter gene (pCMV-Luc) after an anticancer drug, Doxorubicin (DOX), was loaded by dialysis method. Gel retardation studies proved that micelles with or without DOX were able to complex with DNA completely at an equivalent N/P ratio of around 2.0, indicating that drug loading did not interfere in the interaction between the PEI shell and DNA. Particle size slightly decreased at higher N/P ratios of polyplexes, but increased with drug encapsulation. It was also noted that DNA/micelle complexes were significantly less toxic to HepG2 cells than blank PEC micelles, and improved gene transfection efficiency (about 3 orders of magnitude greater than PEI 25K alone at most) whether DOX was present in the system or not. These results suggest that this group of cationic graft polymers may be a potential candidate for the development of a drug delivery system that can examine the synergistic effects of combined drug and gene therapy.

Adult human sarcomas. II. Medical oncology

Human sarcoma cells can be killed by radio- and chemotherapy, but tumor cells acquiring resistance frequently kill the patient. A keen understanding of the intracellular course of oncogenic cascades leads to the discovery of small molecular inhibitors of the involved phosphorylated kinases. Targeted therapy complements chemotherapy. Oncogene silencing is feasible by small interfering RNA. The restoration of some of the mutated or deleted tumor-suppressor genes (p53, Rb, PTEN, hSNF, INK/ARF and WT) by demethylation or reacetylation of their histones has been accomplished. Genetically engineered or naturally oncolytic viruses selectively lyse tumors and leave healthy tissues intact. Adeno- or retroviral vectors deliver genes of immunological costimulators, tumor antigens, chemo- or cytokines and/or tumor-suppressor proteins into tumor (sarcoma) cells. Suicide gene delivery results in apoptosis induction. Genes of enzymes that target prodrugs as their substrates render tumor cells highly susceptible to chemotherapy, with the prodrug to be targeted intracellularly. It will be combinations of sophisticated surgical removal of the nonencapsulated and locally invasive primary sarcomas, advanced forms of radiotherapy to the involved sites and immunotherapy with sarcoma vaccines that will cure primary sarcomas. Adoptive immunotherapy with immune lymphocytes will be operational in metastatic disease only when populations of regulatory T cells are controlled. Targeted therapy with small molecular inhibitors of oncogene cascades, the driving forces of sarcoma cells, alteration of the tumor stroma from a supportive to a tumor-hostile environment, reactivation or replacement of wild-type tumor-suppressor genes, and radio-chemotherapy (with much reduced toxicity) will eventually accomplish the cure of metastatic sarcomas.

Extreme sensitivity to Yondelis (Trabectedin, ET-743) in low passaged sarcoma cell lines correlates with mutated p53

Yondelis (Trabectedin, ET-743) is a marine anticancer agent currently in Phase II/III development in patients with advanced pretreated soft tissue sarcoma. In the present study, we generated a panel of low passaged tumor cell lines from samples explanted from chemonaive sarcoma patients with different tumor types. We assessed in vitro sensitivity/resistance to Trabectedin and doxorubicin in a panel of sarcoma cell lines and examined the correlation between molecular alterations in DNA repair genes and sensitivity to Trabectedin. We treated cell lines with Trabectedin and doxorubicin in both 96-h and clonogenic assays. In both assays, well-defined groups of resistant and sensitive cell lines were observed. Resistance to Trabectedin did not correlate with resistance to doxorubicin, indicating that the two drugs may have different mechanisms of resistance. p53 mutations and deletions correlated with extreme sensitivity (IC50 < 1 nM) to Trabectedin (P < 0.01). In a pair of isogenic cell lines differing only in the presence or absence of wild-type p53, the absence of p53 rendered cells threefold more sensitive to Trabectedin.

Isolated limb perfusion: a novel delivery system for wild-type p53 and fiber-modified oncolytic adenoviruses to extremity sarcoma

Isolated limb perfusion (ILP) is a limb salvage surgical modality used to deliver chemotherapy and biologic agents to locally advanced and recurrent extremity soft tissue sarcoma (STS), and may be readily tailored for delivery of gene therapy. We set out to test the feasibility of delivering AdFLAGp53 (replication incompetent adenovirus bearing FLAG-tagged wild-type p53) and Ad.hTC.GFP/E1a.RGD (a fiber-modified, replication selective oncolytic adenovirus) into human leiomyosarcoma xenografts by ILP. Nude rats bearing SKLMS-1 tumors in their hind limbs underwent ILP with escalating doses of AdLacZ or AdFLAGp53 (study 1), or with Ad.CMV.GFP.RGD or Ad.hTC.GFP/E1a.RGD (study 2) following in vitro confirmation of therapeutic potential in STS cell lines and strains. Seventy-two hours after delivery, reverse transcription-polymerase chain reaction confirmed FLAGp53 expression, and immunohistochemistry confirmed diffuse upregulation of p21CIP1/WAF1 in ILP-treated tumors. Ad.hTC.GFP/E1a.RGD perfused tumors demonstrated robust macroscopic transgene expression throughout their substance, but not in perfused normal tissues, 21 days after delivery. Intra-tumoral viral replication was confirmed by immunohistochemical staining for early (E1a) and late (hexon) viral protein expression. Terminal deoxynucleotidyl transferase-mediated-digoxigenin nick end-labeling staining identified foci of cell death within regions of viral replication. In conclusion, therapeutic adenoviral gene therapy against limb borne human STS can be successfully delivered by ILP and warrants further investigation.

Adult soft tissue sarcomas: Conventional therapies and molecularly targeted approaches

The therapeutic approach to soft tissue sarcomas (STS) has evolved over the past two decades based on the results from randomized controlled trials, which are guiding physicians in the treatment decision-making process. Despite significant improvements in the control of local disease, a significant number of patients ultimately die of recurrent/metastatic disease following radical surgery due to a lack of effective adjuvant treatments. In addition, the characteristic chemoresistance of STS has compromised the therapeutic value of conventional antineoplastic agents in cases of unresectable advanced/metastatic disease. Therefore, novel therapeutic strategies are urgently needed to improve the prognosis of patients with STS. Recent advances in STS biology are paving the way to the development of molecularly targeted therapeutic strategies, the efficacy of which relies not only on the knowledge of the molecular mechanisms underlying cancer development/progression but also on the personalization of the therapeutic regimen according to the molecular features of individual tumours. In this work, we review the state-of-the-art of conventional treatments for STS and summarize the most promising findings in the development of molecularly targeted therapeutic approaches.

The co-transfection of p16(INK4a) and p14(ARF) genes into human lung cancer cell line A549 and the effects on cell growth and chemosensitivity

Two functionally and structurally different proteins, p16(INK4a) and p14(ARF), encoded by the gene INK4a/ARF located at 9p21 are cyclin-dependent kinase (cdk) inhibitors and important cell cycle regulators. More and more evidences have been accumulated to show that the exogenous p16(INK4a) or p14(ARF) can inhibit the cell growth and/or induce the apoptosis. But it is still unclear if they can play positive role when combine with the conventional chemotherapy in cancer treatment. Here we show that cationic liposome-mediated gene transfection of INK4a/ARF into lung cancer cell line A549, in which the INK4a/ARF locus was lost, suppressed the growth and induced apoptosis. When treated with five different chemotherapy drugs with different mechanism after the transfection, A549 got an increased chemosensitivity for adriamycin and cisplatin and an unchanged result for topotecan, taxol or vinorelbine. The results indicated that cell cycle redistribution and increased apoptosis index after transfection might be the main explanation for the enhanced chemosensitivity. The combination of gene therapy with conventional chemotherapy is not always better than single chemotherapy. This trial will be of benefit to the treatment of lung cancer when combine the conventional chemotherapy and gene therapy in the future.

Response rate of fibrosarcoma cells to cytotoxic drugs on the expression level correlates to the therapeutic response rate of fibrosarcomas and is mediated by regulation of apoptotic pathways

BACKGROUND

Because of the high resistance rate of fibrosarcomas against cytotoxic agents clinical chemotherapy of these tumors is not established. A better understanding of the diverse modes of tumor cell death following cytotoxic therapies will provide a molecular basis for new chemotherapeutic strategies. In this study we elucidated the response of a fibrosarcoma cell line to clinically used cytostatic agents on the level of gene expression.

METHODS

HT1080 fibrosarcoma cells were exposed to the chemotherapeutic agents doxorubicin, actinomycin D or vincristine. Total RNA was isolated and the gene expression patterns were analyzed by microarray analysis. Expression levels for 46 selected candidate genes were validated by quantitative real-time PCR.

RESULTS

The analysis of the microarray data resulted in 3.309 (actinomycin D), 1.019 (doxorubicin) and 134 (vincristine) probesets that showed significant expression changes. For the RNA synthesis blocker actinomycin D, 99.4% of all differentially expressed probesets were under-represented. In comparison, probesets down-regulated by doxorubicin comprised only 37.4% of all genes effected by this agent. Closer analysis of the differentially regulated genes revealed that doxorubicin induced cell death of HT1080 fibrosarcoma cells mainly by regulating the abundance of factors mediating the mitochondrial (intrinsic) apoptosis pathway. Furthermore doxorubicin influences other pathways and crosstalk to other pathways (including to the death receptor pathway) at multiple levels. We found increased levels of cytochrome c, APAF-1 and members of the STAT-family (STAT1, STAT3), while Bcl-2 expression was decreased. Caspase-1, -3, -6, -8, and -9 were increased indicating that these proteases are key factors in the execution of doxorubicin mediated apoptosis.

CONCLUSION

This study demonstrates that chemotherapy regulates the expression of apoptosis-related factors in fibrosarcoma cells. The number and the specific pattern of the genes depend on the used cytotoxic drug. The response rates on the gene expression level, i.e. the number of genes regulated by the drugs actinomycin D, doxorubicin and vincristine, correlate to the clinical effectiveness of the drugs. Doxorubicin seems to exert its cytotoxic mechanism by regulating genes, which are involved in several different apoptosis regulating pathways. The exact knowledge of the genes affected by the drugs will help to understand the diverse modes of soft tissue sarcoma cell death in response to cytotoxic therapies.

Tamoxifen can reverse multidrug resistance of colorectal carcinoma in vivo

AIM: To investigate the effect of tamoxifen (TAM) on multidrug resistance (MDR) of colorectal carcinoma in vivo and its relationship with estrogen receptor (ER).

METHODS: Multidrug resistance was determined by means of semi-quantitative retro-transcription polymerase chain reaction (RT-PCR) to test mdr1 gene mRNA and ER expression was studied by immunohistochemistry. Tumor tissues from three cases of human colon carcinoma, which had mdr1(+)/ER(+), mdr1(+)/ER(-), mdr1(-) expressions, were planted subcutaneously in the neck of nude mice to establish three xenograft models. These models were subdivided into four subgroups randomly: Doxorubicin (DOX)-treated group, TAM-treated group, DOX and TAM group and control group. The dimensions of these xenografts were measured after each course of treatment and the xenografts were removed at the end of the experiments for measurements of weight and the variation of mdr1 mRNA level with RT-PCR. In each course, TAM [15 mg/(kg/d)] was administrated orally per day in the first seven days and DOX (3.6 mg/kg) was injected peritoneally on the first day. Data was evaluated by q and t tests.

RESULTS: In the animal models with mdr1(-) tumor, the weights and volumes of the planted tumor in DOX group [(39.1±2.29) mg, (31.44±1.61) mm³] and TAM and DOX group [(38.72±2.56) mg, (31.31±1.74) mm³], which were lesser than that of control group [(45.48±3.92) mg, (36.42±2.77) mm³, P = 0.037, P = 0.016 respectively] significantly. In the animal models with mdr1(+)/ER(+) tumor, the weights and volumes of planted tumor were not affected by DOX or TAM treatment; however, in TAM and DOX group [(425.5±28.58) mg, (340.35±22.28) mm³], they were significantly less than that of control group [(634.23±119.41) mg, (507.45±93.34) mm³, P = 0.022, P = 0.045 respectively], which are similar to that in the models with mdr1(+)/ER(-) tumor. No significant changes were found in the expressive level of mdr1 mRNA following these treatments.

CONCLUSION: The expression of mdr1 gene corresponds to the sensitivity of colon cancer to anti-tumor drugs in vivo. TAM can reverse the MDR of colorectal carcinoma in nude mice, which is independent of the expression of ER; however, no change was observed in the expressive level of mdr1 mRNA.

Transcriptional repression of protein kinase Calpha via Sp1 by wild type p53 is involved in inhibition of multidrug resistance 1 P-glycoprotein phosphorylation

The protein kinase C (PKC) family consists of serine/threonine protein kinases that play important roles in signal transduction, cell proliferation, and tumor formation. Recent studies found that PKCs are commonly overexpressed in human tumors, including soft tissue sarcoma (STS). Overexpression of PKCs contributes to invasion and migration of tumor cells and induction of angiogenesis. PKC can also phosphorylate the multidrug resistance (MDR) gene-encoded P-glycoprotein and induce MDR phenotype. Our previous studies showed that mutation of p53 enhanced STS metastasis and mediated the MDR phenotype. Restoring wild type (WT) p53 in STS cells containing mutant p53 sensitized the cells to chemotherapy. In the present study, we found that PKCalpha protein expression is inhibited by WT p53 partly due to reduced PKCalpha mRNA expression in STS cells, but p53 does not affect PKCalpha mRNA stability. Deletion and mutation analysis of the PKCalpha promoter fused to the luciferase reporter gene identified a Sp1 binding site (-244/-234) in the PKCalpha promoter that is required for p53-mediated inhibition of PKCalpha promoter activity. More importantly, PKCalpha phosphorylates and activates MDR1 P-glycoprotein, whereas inhibition of PKCalpha by p53 leads to decreased MDR1 phosphorylation in STS cells, which sensitizes STS cells to chemotherapeutic agents. These data indicate that WT p53 may resensitize STS to chemotherapeutic agents by reducing MDR1 phosphorylation via transcriptional repression of PKCalpha expression. Thus, molecular-based therapies targeting mutant p53 and PKCalpha may be an effective new strategy to improve chemotherapeutic efficacy in STS.

A modified p53 enhances apoptosis in sarcoma cell lines mediated by doxorubicin

Mdm2 is frequently overexpressed in sarcoma cells and may contribute to drug resistance by increasing p53 degradation. We investigated the induction of apoptosis in sarcoma cells via adenovirus-mediated gene transfer of wild-type p53 and two modified p53 genes, p53 14/19 and p53 22/23, whose protein products are resistant to Mdm2-mediated degradation. We found that adenovirus-wt p53 (Ad-wt p53) induces significant apoptosis in HT1080 fibrosarcoma cells expressing low levels of Mdm2, but fails to induce apoptosis in SJSA osteosarcoma cells expressing high levels of Mdm2. In contrast, Ad-p53 14/19 induces significant apoptosis in both cell lines. Interestingly, Ad-p53 22/23, a vector encoding a transcription-defective p53 mutant, causes limited apoptosis in both cell lines. We demonstrate that doxorubicin induces phosphorylation of both wt p53 and p53 14/19 protein at multiple sites. We tested the efficacy of doxorubicin and cisplatin with either Ad-wt p53, Ad-p53 22/23 or Ad-p53 14/19. SJSA cells, although harbouring endogenous wt p53, did not undergo significant apoptosis following doxorubicin or cisplatin exposure alone or combined with Ad-wt p53. In contrast, doxorubicin or cisplatin plus Ad-p53 14/19 induced significant apoptosis. Gene transfer of p53 14/19 in combination with the administration of doxorubicin or cisplatin is a potential therapeutic approach for cancers expressing high levels of Mdm2.

Multidrug resistance proteins in tuberous sclerosis and refractory epilepsy

Tuberous sclerosis is an autosomal dominant syndrome characterized by seizures that are refractory to medication in severely affected individuals. The mechanism involved in drug resistance in tuberous sclerosis is unknown. The proteins MDR-1 (multidrug resistance) and MRP-1 (multidrug resistance-associated protein-1) are linked to chemotherapy resistance in tumor cells. However, the relationship between refractoriness to antiepileptic drugs and MDR-1 or MRP-1 brain expression has been poorly studied. We have previously described a case of tuberous sclerosis with refractory epilepsy that expressed multidrug resistance gene (MDR-1) in tuber cells from epileptogenic brain lesion. In this retrospective study, we describe the expression of MDR-1 and MRP-1 in the epileptogenic cortical tubers of three pediatric patients with tuberous sclerosis and refractory epilepsy surgically treated. Monoclonal antibodies for MDR-1 and MRP-1 proteins were used for immunohistochemistry. In epileptogenic cortical tuber brain specimens, MDR-1 and MRP-1 proteins were strongly immunoreactive in abnormal balloon cells, dysplastic neurons, astrocytes, microglial cells, and some blood-brain vessels. A more extensive MDR-1 immunoreactivity was observed. These data suggest that refractory epilepsy phenotype in tuberous sclerosis can be associated with the expression of both multidrug resistance MDR-1 and MRP-1 transporters in epileptogenic cortical tubers.

Spontaneous Reversal of P-Glycoprotein Expression in Multidrug Resistant Cell Lines*

Increased expression of P-glycoprotein encoded by the mdr-1 gene is a well-characterised mechanism for resistance to cancer chemotherapeutic drugs in cell lines. However, the P-glycoprotein expression after removal of the selection pressure has not fully been elucidated. The stability of P-glycoprotein expression in the presence (+) and absence (-) of vincristine (30 or 150 nM) was studied in multidrug resistant K562 cell lines (VCR30+, VCR150+, VCR30- and VCR150-) for 11 months. The P-glycoprotein protein and mdr-1 mRNA levels were determined at regular intervals using flow cytometry and real-time PCR, respectively. Chemosensitivity to a panel of antineoplastic drugs was measured using an MTT assay. The presence of vincristine (VCR30+ and VCR150+) resulted in high and stable levels of P-glycoprotein and mdr-1 mRNA during the whole period compared to wild type. As for the VCR30- and VCR150- subcultures, the expressions of P-glycoprotein and mdr-1 mRNA were stable for five months, and then the levels decreased rapidly. Concomitantly, the sensitivity to drugs known as P-glycoprotein substrates was restored. In conclusion, resistant cells growing in the presence of the inducing drug have a stable P-glycoprotein expression and resistance level, but removing the inducing drug may result in a sudden and rapid lowering of P-glycoprotein and mdr-1 mRNA levels as long as five months after drug withdrawal.

Isolation of temperature-sensitive p53 mutations from a comprehensive missense mutation library

Temperature-sensitive (ts) mutations have been used as a genetic and molecular tool to study the functions of many gene products. Each ts mutant protein may contain a temperature-dependent intramolecular mechanism such as ts conformational change. To identify key ts structural elements controlling the protein function, we screened ts p53 mutants from a comprehensive mutation library consisting of 2,314 p53 missense mutations for their sequence-specific transactivity through p53-binding sequences in Saccharomyces cerevisiae. We isolated 142 ts p53 mutants, including 131 unreported ts mutants. These mutants clustered in beta-strands in the DNA-binding domain, particularly in one of the two beta-sheets of the protein, and 15 residues (Thr155, Arg158, Met160, Ala161, Val172, His214, Ser215, Pro223, Thr231, Thr253, Ile254, Thr256, Ser269, Glu271, and Glu285) were ts hot spots. Among the 142 mutants, 54 were examined further in human osteosarcoma Saos-2 cells, and it was confirmed that 89% of the mutants were also ts in mammalian cells. The ts mutants represented distinct ts transactivities for the p53 binding sequences and a distinct epitope expression pattern for conformation-specific anti-p53 antibodies. These results indicated that the intramolecular beta-sheet in the core DNA-binding domain of p53 was a key structural element controlling the protein function and provided a clue for finding a molecular mechanism that enables the rescue of the mutant p53 function.

Experimental approaches to treatment of soft tissue sarcoma

The experimental approaches described in this article represent potential new approaches for targeted therapy. Thus far, none of the preclinical data have demonstrated a cure for sarcomas; however, the antitumor effects of many of these new agents seem to be enhanced when the agents are combined with chemotherapeutic agents. The combination of novel therapeutics with conventional chemotherapy may be the most effective strategy in terms of maximization of tumor killing and minimization of toxicity and the risk of drug resistance. Not only are new drugs being developed for treatment of sarcomas but new ways of delivering drugs are also being investigated. The angiogenic, or metronomic, schedule of drug delivery may be preferable to conventional schedules in achieving optimal tumor inhibition. In addition, isolated limb perfusion is a unique approach to delivery of drugs, such as TNF and melphalan, for sarcomas and melanomas [137, 138]. The advantages of this method of drug delivery include the ability to administer therapeutic agents in high concentrations to a specific region of the body without systemic toxicity. Further advances in the understanding of the biology of sarcomas along with novel approaches to delivery of drugs are crucial to the development of new and effective therapies.

Tumor p53 status and response to topoisomerase II inhibitors

It is thought that when tumor cells are treated with anticancer drugs, they die through the apoptotic pathway and that cell resistance to cancer chemotherapy is mainly a resistance to apoptosis commitment. p53 is not functional in nearly half of the tumors examined and because of its involvement (directly or through its target genes) in the apoptotic pathway, drug resistance to chemotherapy has been largely attributed to the status of this "tumor suppressor protein". Topoisomerase II (topo II) inhibitors are widely used not only as single agents, but also in the majority of combination treatment protocols for hematologic malignancies and solid tumors. The relationship between p53 and topo II raises many questions about basic regulatory, biochemical, structural and functional characteristics that could be different in cells in different tissues, and most importantly, between different tumor cell types and their normal tissue counterpart. Understanding these relationships may lead to strategies for chemotherapy optimization and further precision targeting of tumor cells in order to avoid drug resistance and thereby chemotherapy failure.

Expression and function of classical protein kinase C isoenzymes in gastric cancer cell line and its drug-resistant sublines

AIM: To investigate the expression and function of classical protein kinase C (PKC) isoenzymes in inducing MDR phenotype in gastric cancer cells.

METHODS: Two cell lines were used in the study: gastric cancer cell SGC7901 and its drug-resistant cell SGC7901/VCR stepwise-selected by vincristine 0.3, 0.7 and 1.0 mg·L^-1, respectively. The expression of classical PKC (cPKC) isoenzymes in SGC7901 cells and SGC7901/VCR cells were detected using immunofluorescent cytochemistry, laser confocal scanning microscope and Western blot. The effects of anti-PKC isoenzymes antibody on adriamycin accumulation in SGC7901/VCR cells were determined using flow cytometric analysis.

RESULTS: (1) SGC7901 cells exhibited positive staining of PKC-α. SGC7901/VCR cells exhibited stronger staining of PKC-α than SGC7901 cells. The higher dosage vincristine selected, the much stronger staining of PKC-α was observed on SGC7901/VCR cells. (2) Both SGC7901 and SGC7901/VCR cells exhibited positive staining of PKC-β I and PKC-β II with no significant difference. (3) Compared with SGC7901, SGC7901/VCR cells had decreased adriamycin accumulation and retention. Accumulation of adriamycin in SGC7901 was 5.21 ± 2.56 mg·L^-1, in SGC7901/VCR 0.3 was 0.85 ± 0.29 mg·L^-1, in SGC7901/VCR 0.7 was 0.81 ± 0.32 mg·L^-1, and in SGC7901/VCR 1.0 was 0.80 ± 0.33 mg·L^-1; Retention of adriamycin in SGC7901 was 2.51 ± 1.23 mg·L^-1, in SGC7901/VCR 0.3 was 0.47 ± 0.14 mg·L^-1, in SGC7901/VCR 0.7 was 0.44 ± 0.15 mg·L^-1, and in SGC7901/VCR 1.0 was 0.41 ± 0.11 mg·L^-1. (4) Fluorescence intensity presented adriamycin accumulation in SGC7901/VCR cells was increased from 1.14 ± 0.36 to 2.71 ± 0.94 when cells were co-incubated with anti-PKC-α but not with anti-PKC-β I, PKC-α II and PKCγ antibodies.

CONCLUSION: PKC-α, but not PKC-β I, PKC-β II or PKCγ, may play a role in multidrug resistance of gastric cancer cells SGC7901/VCR.