Functional imaging of multidrug resistance in an orthotopic model of osteosarcoma using 99mTc-sestamibi

LAMTOR5-AS1 regulates chemotherapy-induced oxidative stress by controlling the expression level and transcriptional activity of NRF2 in osteosarcoma cells

Long-noncoding RNAs (lncRNAs) play roles in regulating cellular functions. High-throughput sequencing analysis identified a new lncRNA, termed LAMTOR5-AS1, the expression of which was much higher in the chemosensitive osteosarcoma (OS) cell line G-292 than in the chemoresistant cell line SJSA-1. Further investigations revealed that LAMTOR5-AS1 significantly inhibits the proliferation and multidrug resistance of OS cells. In vitro assays demonstrated that LAMTOR5-AS1 mediates the interaction between nuclear factor erythroid 2-related factor 2 (NFE2L2, NRF2) and kelch-like ECH-associated protein 1 (KEAP1), which regulate the oxidative stress. Further mechanistic studies revealed that LAMTOR5-AS1 inhibited the ubiquitination degradation pathway of NRF2, resulting in a higher level of NRF2 but a loss of NRF2 transcriptional activity. High level of NRF2 in return upregulated the downstream gene heme oxygenase 1 (HO-1). Moreover, NRF2 controls its own activity by promoting LAMTOR5-AS1 expression, whereas the feedback regulation is weakened in drug-resistant cells due to high antioxidant activity. Overall, we propose that LAMTOR5-AS1 globally regulates chemotherapy-induced cellular oxidative stress by controlling the expression and activity of NRF2.

Itraconazole synergistically increases therapeutic effect of paclitaxel and 99mTc-MIBI accumulation, as a probe of P-gp activity, in HT-29 tumor-bearing nude mice

P-glycoprotein (P-gp), is an important efflux pump involved in chemotherapy resistance in human colon cancer. We investigated the efficacy of itraconazole as a P-gp inhibitor and its therapeutic synergistic relationship to paclitaxel through 99mTc-MIBI accumulation in HT-29 tumor-bearing nude mice. Histopathological screening along with in vitro experiments was done for further assessment. Itraconazole successfully inhibited P-gp mediated 99mTc-MIBI efflux, increasing its in vitro accumulation in itraconazole-receiving dishes. Notably, the co-administration of itraconazole with paclitaxel significantly enhanced the in vitro cytotoxicity effect of paclitaxel in itraconazole + paclitaxel wells containing HT-29 cells. Compared to the control, tumor volume in mice treated with itraconazole, paclitaxel and itraconazole +paclitaxel showed growth suppression approximately by 36.21, 60.02, and 73.3% respectively. And compared to paclitaxel group, the nude mice co-treated with paclitaxel and itraconazole showed suppression of tumor growth by about 33.31 % at the end of the treatment period. Also the biodistribution result showed that the co-administration of itraconazole with paclitaxel raised the mean tumor radioactivity accumulation compared to control and paclitaxel group. When given paclitaxel alone, the ID% of hepatic and cardiac tissue was reduced while co-administration of itraconazole with paclitaxel increased 99mTc-MIBI accumulation in these organs. Furthermore, the histopathological findings confirmed the biodistribution results. These results demonstrate that although monotherapy with itraconazole or paclitaxel has anti-tumor activity against HT-29 human colorectal cancer, a synergistic anti-tumor activity can be achieved when itraconazole is co-administered with paclitaxel. Also, 99mTc-MIBI is an effective radiotracer for monitoring response to treatment in MDR tumors.

Tumor cell MT1-MMP is dispensable for osteosarcoma tumor growth, bone degradation and lung metastasis

The membrane-anchored matrix metalloprotease MT1-MMP is a potent collagenolytic enzyme with a well-established role in extracellular matrix turnover and cellular invasion into collagen-rich tissues. MT1-MMP is highly expressed in various types of cancer and has been demonstrated to be directly involved in several stages of tumor progression, including primary tumor growth, angiogenesis, invasion and metastasis. Osteosarcoma is the most common type of primary bone cancer. This disease is characterized by invasive tumor growth, leading to extensive bone destruction, and metastasis to the lungs. The tumor cells in human osteosarcoma display a strong expression of MT1-MMP, but the role of MT1-MMP in osteosarcoma progression is currently unknown. In this study, we investigated the role of MT1-MMP during various stages of osteosarcoma development. We utilized an optimized orthotopic murine osteosarcoma model and human osteosarcoma cells in which the MT1-MMP gene was knocked out using CRISPR/Cas9. We observed a strong expression of MT1-MMP in wildtype cells of both primary tumors and lung metastases, but, surprisingly, MT1-MMP deficiency did not affect primary tumor growth, bone degradation or the formation and growth of lung metastases. We therefore propose that, unlike findings reported in other cancers, tumor-expressed MT1-MMP is dispensable for all stages of osteosarcoma progression.

What "The Cancer Genome Atlas" database tells us about the role of ATP-binding cassette (ABC) proteins in chemoresistance to anticancer drugs

Introduction: Chemotherapy remains the only option for advanced cancer patients when other alternatives are not feasible. Nevertheless, the success rate of this type of therapy is often low due to intrinsic or acquired mechanisms of chemoresistance. Among them, drug extrusion from cancer cells through ATP-binding cassette (ABC) proteins plays an important role. ABC pumps are primary active transporters involved in the barrier and secretory functions of many healthy cells. Areas covered: In this review, we have used The Cancer Genome Atlas (TCGA) database to explore the relationship between the expression of the major ABC proteins involved in cancer chemoresistance in the most common types of cancer, and the drugs used in the treatment of these tumors that are substrates of these pumps. Expert opinion: From unicellular organisms to humans, several ABC proteins play a major role in detoxification processes. Cancer cells exploit this ability to protect themselves from cytostatic drugs. Among the ABC pumps, MDR1, MRPs and BCRP are able to export many antitumor drugs and are expressed in several types of cancer, and further up-regulated during treatment. This event results in the enhanced ability of tumor cells to reduce intracellular drug concentrations and hence the pharmacological effect of chemotherapy.

99mTc-Radiolabeled TPGS Nanomicelles Outperform 99mTc-Sestamibi as Breast Cancer Imaging Agent

D-α-Tocopheryl polyethylene glycol 1000 succinate (TPGS) is a Food and Drug Administration (FDA) approved biomaterial that can form nanosized micelles in aqueous solution. TPGS micelles stand as an interesting system to perform drug delivery as they can carry lipophilic drugs and overcome P glycoprotein efflux as well. Therefore, TPGS micelles combined with other copolymers have been reported in many cancer research studies as a carrier for therapeutic drugs. Their ability to reach tumoral tissue can also be exploited to develop imaging agents with diagnostic application. A radiolabeling method with ^99mTc for TPGS nanosized micelles and their biodistribution in a healthy animal model as well as their pharmacokinetics and radiolabeling stability in vivo was previously reported. The aim of this work was to evaluate the performance of this radioactive probe as a diagnostic imaging agent compared to routinely available SPECT radiopharmaceutical, ^99mTc-sestamibi. A small field of view gamma camera was used for scintigraphy studies using radiolabeled TPGS micelles in two animal models of breast cancer: syngeneic 4T1 murine cell line (injected in BALB/c mice) and chemically NMU-induced (Sprague-Dawley rats). Ex vivo radioactivity accumulation in organs of interest was measured by a solid scintillation counter, and a semiquantitative analysis was performed over acquired images as well. Results showed an absence of tumoral visualization in 4T1 model for both radioactive probes by gamma camera imaging. On the contrary, NMU-induced tumors had a clear tumor visualization by scintigraphy. A higher tumor/background ratio and more homogeneous uptake were found for radiolabeled TPGS micelles compared to ^99mTc-sestamibi. In conclusion, ^99mTc-radiolabeled TPGS micelles might be a potential SPECT imaging probe for diagnostic purposes.

A new therapeutic proposal for inoperable osteosarcoma: Photodynamic therapy

BACKGROUND

Osteosarcoma, a malignant tumor characterized by bone or osteoid formation, is the second most common primary bone neoplasm. Clinical symptoms include local and surrounding pain, unrelieved by rest or anesthesia. Osteosarcoma has a poor chemotherapeutic response with prognosis dependent on complete tumor excision. Therefore, for inoperable osteosarcoma new therapeutic strategies are needed. The present study aimed to develop murine models of cranial and vertebral osteosarcoma that facilitate simple clinical monitoring and real-time imaging to evaluate the outcome of photodynamic therapy based on a previously developed photosensitizer.

METHODS

Balb/c nude mice were divided into two groups: the cranial and vertebral osteosarcoma groups. Each group was further subdivided into the photodynamic therapy-treated and untreated groups. Images were obtained by scintigraphy with ^99mTc-MIBI and radiography. Tumor growth, necrotic area, osteoid matrix area, and inflammatory infiltration were analyzed.

RESULTS

Cranial and vertebral tumors could be macroscopically observed and measured. Radiographic and scintigraphic images showed tumor cells present at the inoculation sites. After photodynamic therapy, scintigraphy showed lower tumoral radiopharmaceutical uptake, which correlated histologically with increased necrosis. Osteoid matrix volume increased, and tumor size decreased in all photodynamic therapy-treated animals.

CONCLUSION

Cranial and vertebral osteosarcoma models in athymic mice are feasible and facilitate in vivo monitoring for the development of new therapies. Photodynamic therapy is a potential antitumoral treatment for surgically inoperable osteosarcoma.

Tissue factor associates with survival and regulates tumour progression in osteosarcoma

Osteosarcoma is the most common primary malignant bone tumour. Patients often develop lung metastasis and have a poor prognosis despite extensive chemotherapy and surgical resections. Tissue Factor is associated with poor clinical outcome in a wide range of cancer types, and promotes angiogenesis and metastasis. The role of Tissue Factor in OS tumourigenesis is unknown. Fifty-three osteosarcoma pre-treatment biopsies and four osteosarcoma cell lines were evaluated for Tissue Factor expression, and a possible association with clinical parameters was investigated. Tissue Factor function was inhibited in an osteosarcoma cell line (143B) by shRNA knockdown or specific antibodies, and pro-tumourigenic gene expression, proliferation, matrigel invasion and transwell migration was examined. 143B cells were implanted in mice in the presence of Tissue Factor-blocking antibodies, and tumour volume, micro-vessel density and metastases in the lung were evaluated. Tissue Factor was highly expressed in 73.6 % of osteosarcoma biopsies, and expression associated significantly with disease-free survival. Tissue Factor was expressed in all four investigated cell lines. Tissue Factor was knocked down in 143B cells, which led to reduced expression of IL-8, CXCL-1, SNAIL and MMP2, but not MMP9. Tissue Factor knockdown or inhibition with antibodies reduced matrigel invasion. Tissue Factor antibodies limited 143B tumour growth in vivo, and resulted in decreased intra-tumoural micro-vessel density. Furthermore, lung metastasis from the primary tumour was significantly reduced. Thus, Tissue Factor expression in osteosarcoma reduces metastasis-free survival in patients, and increases pro-tumourigenic behaviour both in vitro and in vivo.

Orthotopic murine model of a primary malignant bone tumor in the spine: functional, bioluminescence, and histological correlations

OBJECT

There is currently no reproducible animal model of human primary malignant bone tumors in the spine to permit laboratory investigation of the human disease. Therefore, the authors sought to adapt their previously developed orthotopic model of spinal metastasis to a model for primary malignant bone tumors of the spine.

METHODS

A transperitoneal surgical approach was used to implant osteosarcoma (Krib-1) into the L-3 vertebral body of nude mice via a drill hole. Motor function was evaluated daily using the previously validated qualitative key milestones of tail dragging, dorsal stepping, hindlimb sweeping, and paralysis. A subset of these animals was euthanized upon reaching the various milestones, and the spines were removed, sectioned, and stained. The degree of spinal cord compression was correlated with the occurrence of milestones and assessed by a ratio between the neural elements divided by the area of the spinal canal. Another subset of animals received stably transfected Krib-1 cells with the luciferase gene, and bioluminescence was measured at 10, 20, and 30 days postimplantation.

RESULTS

Osteosarcoma xenografts grew in all animals according to a reliable and reproducible time course; the mean time for development of behavioral milestones was noted in relation to the day of implantation (Day 1). Tail dragging (Milestone 1) occurred on Day 19.06 (95% CI 16.11-22.01), dorsal stepping (Milestone 2) occurred on Day 28.78 (95% CI 26.79-30.77), hindlimb sweeping (Milestone 3) occurred on Day 35.61 (95% CI 32.9-38.32), and paralysis of the hindlimb (Milestone 4) occurred on Day 41.78 (95% CI 39.31-44.25). These clinically observed milestones correlated with increasing compression of the spinal cord on histological sections. The authors observed a progressive increase in the local bioluminescence (in photons/cm²/sec) of the implanted level over time with a mean of 2.17 (range 0.0-8.61) at Day 10, mean 4.68 (range 1.17-8.52) at Day 20, and mean 5.54 (range 1.22-9.99) at Day 30.

CONCLUSIONS

The authors have developed the first orthotopic murine model of a primary malignant bone tumor in the spine, in which neurological decline reproducibly correlates with tumor progression as evidenced by pathological confirmation and noninvasive bioluminescence measurements. Although developed for osteosarcoma, this model can be expanded to study other types of primary malignant bone tumors in the spine. This model will potentially allow animal testing of targeted therapies against specific primary malignant tumor types.

Osteosarcoma models: from cell lines to zebrafish

High-grade osteosarcoma is an aggressive tumor most commonly affecting adolescents. The early age of onset might suggest genetic predisposition; however, the vast majority of the tumors are sporadic. Early onset, most often lack of a predisposing condition or lesion, only infrequent (<2%) prevalence of inheritance, extensive genomic instability, and a wide histological heterogeneity are just few factors to mention that make osteosarcoma difficult to study. Therefore, it is sensible to design and use models representative of the human disease. Here we summarize multiple osteosarcoma models established in vitro and in vivo, comment on their utilities, and highlight newest achievements, such as the use of zebrafish embryos. We conclude that to gain a better understanding of osteosarcoma, simplification of this extremely complex tumor is needed. Therefore, we parse the osteosarcoma problem into parts and propose adequate models to study them each separately. A better understanding of osteosarcoma provides opportunities for discovering and assaying novel effective treatment strategies.

“Sometimes the model is more interesting than the original disease”

PJ Hoedemaeker (1937–2007).

Real-time cancer cell tracking by bioluminescence in a preclinical model of human bladder cancer growth and metastasis

BACKGROUND

Bladder cancer is the fifth most common malignancy in the Western world and the second most frequently diagnosed genitourinary tumor. In the majority of cases, death from bladder cancer results from metastatic disease. Understanding the multistep process of carcinogenesis and metastasis in urothelial cancers is pivotal to the development of new therapeutic strategies. Molecular imaging of cancer growth and metastasis in preclinical models provides the essential link between cell-based experiments and clinical translation.

OBJECTIVE

Develop preclinical models for sensitive bladder cancer cell tracking during tumor progression and metastasis.

DESIGN, SETTING, AND PARTICIPANTS

A human transitional cell carcinoma UM-UC-3 cell line was generated that stably expresses luciferase 2 (UM-UC-3luc2), a mammalian codon-optimized firefly luciferase with superior expression. Preclinical models were developed with human UM-UC-3luc2 cells xenografted into the bladder (orthotopic model with metastases) or inoculated into the left cardiac ventricle (bone metastasis model) of immunocompromised mice.

MEASUREMENTS

Noninvasive, sensitive bioluminescent imaging of human firefly luciferase 2-positive bladder cancer in mice using the IVIS100 imaging system.

RESULTS AND LIMITATIONS

In the orthotopic model (intravesical inoculation), tumor growth could be followed directly after inoculation of UM-UC-3luc2 cells. Importantly, micrometastatic lesions originating from orthotopically implanted cancer cells could be detected in the locoregional lymph nodes and in distant organs. In addition, the superior bioluminescent indicator firefly luciferase 2 allows the detection and monitoring of micrometastatic lesions in real time after intracardiac inoculation of human bladder cancer cells in mice. The main disadvantage is the lack of T-cell immunity in the preclinical models.

CONCLUSIONS

The new bioluminescence-based preclinical bladder cancer models enable superior, noninvasive, and real-time tracking of cancer cells, tumor progression, and micrometastasis. Because of the significant improvement in detection of small cell numbers, the presented models are ideally suited for functional studies dealing with minimal residual disease as well as real-time imaging of drug response.

P-glycoprotein versus MRP1 on transport kinetics of cationic lipophilic substrates: a comparative study using [99mTc]sestamibi and [99mTc]tetrofosmin

The multidrug resistance (MDR) phenotype in cancer is closely related with the overexpression of P-glycoprotein (Pgp) and multidrug resistance protein-1 (MRP1). Although conferring resistance to a similar spectrum of drugs, these proteins present distinct transport mechanisms and have their own substrates. In this work, we compared the functional properties of Pgp and MRP1 in the transport kinetics of two cationic lipophilic tracers, [(99m)Tc]sestamibi and [(99m)Tc]tetrofosmin, in cellular models of resistance. Cellular transport kinetics of both tracers was evaluated in Small-cell lung cancer cell line H69 and in its drug-resistant sublines, H69LX4 and H69AR, overexpressing Pgp and MRP1, respectively. Studies were performed in the absence and in the presence of MDR modulators. Kinetic parameters extracted from time-activity curves were analyzed through receiver-operating characteristics curve analysis. The uptake and the efflux rate of both radiotracers were significantly higher (p < 0.05) in sensitive cells. However, MRP1 was more effective than Pgp in removing tracers from the intracellular medium. The addition of verapamil and PSC833 significantly reduced the efflux rate and restored the accumulation of both tracers in H69LX4 cells. Only verapamil was effective in the inhibition of MRP1; however, the effects were more pronounced with [(99m)Tc]sestamibi, when compared to [(99m)Tc]tetrofosmin. Outward transport of radiotracers by MRP1 was dependent on the intracellular glutathione levels. We concluded that both tracers can detect Pgp- and MRP1-mediated drug resistance, based on transport kinetics; however, MRP1 is more effective than Pgp on outward transport of radiotracers. We postulate that this finding can be useful to distinguish between the two resistance mechanisms.

A mouse model of pulmonary metastasis from spontaneous osteosarcoma monitored in vivo by Luciferase imaging

Background

Osteosarcoma (OSA) is lethal when metastatic after chemotherapy and/or surgical treatment. Thus animal models are necessary to study the OSA metastatic spread and to validate novel therapies able to control the systemic disease. We report the development of a syngeneic (Balb/c) murine OSA model, using a cell line derived from a spontaneous murine tumor.

Methodology

The tumorigenic and metastatic ability of OSA cell lines were assayed after orthotopic injection in mice distal femur. Expression profiling was carried out to characterize the parental and metastatic cell lines. Cells from metastases were propagated and engineered to express Luciferase, in order to follow metastases in vivo.

Principal Findings

Luciferase bioluminescence allowed to monitor the primary tumor growth and revealed the appearance of spontaneous pulmonary metastases. In vivo assays showed that metastasis is a stable property of metastatic OSA cell lines after both propagation in culture and luciferase trasduction. When compared to parental cell line, both unmodified and genetically marked metastatic cells, showed comparable and stable differential expression of the enpp4, pfn2 and prkcd genes, already associated to the metastatic phenotype in human cancer.

Conclusions

This OSA animal model faithfully recapitulates some of the most important features of the human malignancy, such as lung metastatization. Moreover, the non-invasive imaging allows monitoring the tumor progression in living mice. A great asset of this model is the metastatic phenotype, which is a stable property, not modifiable after genetic manipulation.