Liquid biopsies and patient-reported outcome measures for integrative monitoring of patients with early-stage breast cancer: a study protocol for the longitudinal observational Prospective Breast Cancer Biobanking (PBCB) study

INTRODUCTION

Breast cancer is still the most common malignancy among women worldwide. The Prospective Breast Cancer Biobank (PBCB) collects blood and urine from patients with breast cancer every 6 or 12 months for 11 years from 2011 to 2030 at two university hospitals in Western Norway. The project aims to identify new biomarkers that enable detection of systemic recurrences at the molecular level. As blood represents the biological interface between the primary tumour, the microenvironment and distant metastases, liquid biopsies represent the ideal medium to monitor the patient's cancer biology for identification of patients at high risk of relapse and for early detection systemic relapse.Including patient-reported outcome measures (PROMs) allows for a vast number of possibilities to compare PROM data with biological information, enabling the study of fatigue and Quality of Life in patients with breast cancer.

METHODS AND ANALYSIS

A total of 1455 patients with early-stage breast cancer are enrolled in the PBCB study, which has a one-armed prospective observational design. Participants consent to contribute liquid biopsies (i.e., peripheral blood and urine samples) every 6 or 12 months for 11 years. The liquid biopsies are the basis for detection of circulating tumour cells, circulating tumour DNA (ctDNA), exosomal micro-RNA (miRNA), miRNA in Tumour Educated Platelet and metabolomic profiles. In addition, participants respond to 10 PROM questionnaires collected annually. Moreover, a control group comprising 200 women without cancer aged 25-70 years will provide the same data.

ETHICS AND DISSEMINATION

The general research biobank PBCB was approved by the Ministry of Health and Care Services in 2007, by the Regional Ethics Committee (REK) in 2010 (#2010/1957). The PROM (#2011/2161) and the biomarker study PerMoBreCan (#2015/2010) were approved by REK in 2011 and 2015 respectively. Results will be published in international peer reviewed journals. Deidentified data will be accessible on request.

TRIAL REGISTRATION NUMBER

NCT04488614.

Astrocytes enhance glioblastoma growth

Glioblastoma (GBM) is a deadly disease with a need for deeper understanding and new therapeutic approaches. The microenvironment of glioblastoma has previously been shown to guide glioblastoma progression. In this study, astrocytes were investigated with regard to their effect on glioblastoma proliferation through correlative analyses of clinical samples and experimental in vitro and in vivo studies. Co-culture techniques were used to investigate the GBM growth enhancing potential of astrocytes. Cell sorting and RNA sequencing were used to generate a GBM-associated astrocyte signature and to investigate astrocyte-induced GBM genes. A NOD scid GBM mouse model was used for in vivo studies. A gene signature reflecting GBM-activated astrocytes was associated with poor prognosis in the TCGA GBM dataset. Two genes, periostin and serglycin, induced in GBM cells upon exposure to astrocytes were expressed at higher levels in cases with high "astrocyte signature score". Astrocytes were shown to enhance glioblastoma cell growth in cell lines and in a patient-derived culture, in a manner dependent on cell-cell contact and involving increased cell proliferation. Furthermore, co-injection of astrocytes with glioblastoma cells reduced survival in an orthotopic GBM model in NOD scid mice. In conclusion, this study suggests that astrocytes contribute to glioblastoma growth and implies this crosstalk as a candidate target for novel therapies.

Drug repurposing in cancer

Cancer is a major health issue worldwide, and the global burden of cancer is expected to increase in the coming years. Whereas the limited success with current therapies has driven huge investments into drug development, the average number of FDA approvals per year has declined since the 1990s. This unmet need for more effective anti-cancer drugs has sparked a growing interest for drug repurposing, i.e. using drugs already approved for other indications to treat cancer. As such, data both from pre-clinical experiments, clinical trials and observational studies have demonstrated anti-tumor efficacy for compounds within a wide range of drug classes other than cancer. Whereas some of them induce cancer cell death or suppress various aspects of cancer cell behavior in established tumors, others may prevent cancer development. Here, we provide an overview of promising candidates for drug repurposing in cancer, as well as studies describing the biological mechanisms underlying their anti-neoplastic effects.

Tumour-associated glial host cells display a stem-like phenotype with a distinct gene expression profile and promote growth of GBM xenografts

BACKGROUND

Little is known about the role of glial host cells in brain tumours. However, supporting stromal cells have been shown to foster tumour growth in other cancers.

METHODS

We isolated stromal cells from patient-derived glioblastoma (GBM) xenografts established in GFP-NOD/scid mice. With simultaneous removal of CD11b⁺ immune and CD31⁺ endothelial cells by fluorescence activated cell sorting (FACS), we obtained a population of tumour-associated glial cells, TAGs, expressing markers of terminally differentiaed glial cell types or glial progenitors. This cell population was subsequently characterised using gene expression analyses and immunocytochemistry. Furthermore, sphere formation was assessed in vitro and their glioma growth-promoting ability was examined in vivo. Finally, the expression of TAG related markers was validated in human GBMs.

RESULTS

TAGs were highly enriched for the expression of glial cell proteins including GFAP and myelin basic protein (MBP), and immature markers such as Nestin and O4. A fraction of TAGs displayed sphere formation in stem cell medium. Moreover, TAGs promoted brain tumour growth in vivo when co-implanted with glioma cells, compared to implanting only glioma cells, or glioma cells and unconditioned glial cells from mice without tumours. Genome-wide microarray analysis of TAGs showed an expression profile distinct from glial cells from healthy mice brains. Notably, TAGs upregulated genes associated with immature cell types and self-renewal, including Pou3f2 and Sox2. In addition, TAGs from highly angiogenic tumours showed upregulation of angiogenic factors, including Vegf and Angiopoietin 2. Immunohistochemistry of three GBMs, two patient biopsies and one GBM xenograft, confirmed that the expression of these genes was mainly confined to TAGs in the tumour bed. Furthermore, their expression profiles displayed a significant overlap with gene clusters defining prognostic subclasses of human GBMs.

CONCLUSIONS

Our data demonstrate that glial host cells in brain tumours are functionally distinct from glial cells of healthy mice brains. Furthermore, TAGs display a gene expression profile with enrichment for genes related to stem cells, immature cell types and developmental processes. Future studies are needed to delineate the biological mechanisms regulating the brain tumour-host interplay.

Dactolisib (NVP-BEZ235) toxicity in murine brain tumour models

Background

Glioblastomas (GBMs) are highly malignant brain tumours with a poor prognosis, and current cytotoxic regimens provide only a limited survival benefit. The PI3K/Akt/mTOR pathway has been an attractive target for therapy due to its high activation in GBMs as well as other cancers. The dual pan-PI3K/mTOR kinase inhibitor dactolisib (NVP-BEZ235) is an anti-neoplastic compound currently under investigation. However, little is known about its efficacy in human GBMs. We aimed at evaluating the efficacy of dactolisib in human glioblastoma cells, as well as in murine models carrying human GBM xenografts.

Methods

To assess the effect of dactolisib in vitro, MTS assay, manual cell count, BrdU incorporation and Annexin V staining experiments were used to observe growth and apoptosis. Furthermore, Akt phosphorylation (S473), a downstream target of PI3K, was explored by western blotting. Animal studies utilizing orthotopic xenograft models of glioblastoma were performed in nude rats and NOD/SCID mice to monitor survival benefit or inhibition of tumor growth.

Results

We found that dactolisib in vitro shows excellent dose dependent anti-growth properties and increase in apoptosis. Moreover, dose dependent inhibition of Akt phosphorylation (S473), a downstream effect of PI3K, was observed by western blotting. However, in two independent animal studies utilizing nude rats and NOD/SCID mice in orthotopic xenograft models of glioblastoma, we observed no survival benefit or inhibition of tumour growth. Severe side effects were observed, such as elevated levels of blood glucose and the liver enzyme alanine transaminase (ALT), in addition to diarrhoea, hair loss (alopecia), skin rash and accumulation of saliva in the oral cavity.

Conclusion

Taken together, our results suggest that despite the anti-neoplastic efficacy of dactolisib in glioma treatment in vitro, its utility in vivo is questionable due to toxicity.

Abstract 3048: Drug repurposing: Validation of sulfasalazine as a radiosensitizer in melanoma by blocking system Xc−

Melanoma is a cancer that has become increasingly frequent over the last decades in the western world. Initial treatment for primary and locoregional melanoma is surgery. In metastatic disease, systematic treatment and recently immunotherapy has been the mainstay. At this stage however, the prognostic outlook is still bleak. Thus, new treatments are urgently needed.

Melanoma is considered to be a radioresistant cancer. The mechanisms underlying radioresistance are multiple and incompletely characterized. In some tumors, radioresistance is mediated by increased synthesis of anti-oxidants that scavenge reactive oxygen species (ROS), induced by radiotherapy. Glutathione (GSH) is an anti-oxidant synthesized from cystine and constitutes a major defense system against oxidative stress in mammalian cells. Cystine is taken up through system Xc− (SXC), an anti-port transmembrane protein with catalytic subunit xCT. Sulfasalazine, a drug approved in the 1950s for treatment of rheumatoid arthritis and inflammatory bowel disease, has been shown to block SXC. Based on previous reports by others, and our own recent findings, we hypothesize that: I) xCT represents a mechanism for radioresistance and is expressed in radioresistant melanoma cancer and II) xCT inhibitors can act as radiosensitizers to potentiate the efficacy of radiotherapy. Expression of the catalytic subunit of SXC, xCT, was found in tissue micro array of primary and secondary melanoma biopsies. In addition, SAS treatment dramatically reduced cystine-uptake and GSH levels in melanoma cells in vitro, and markedly increased the levels of reactive oxygen species (ROS). Furthermore, SAS and radiation synergistically increased DNA double-strand breaks and increased glioma cell death, whereas adding the anti-oxidant N-acetyl-L-cysteine (NAC) reversed cell death. Moreover, SAS and irradiation synergistically reduced subcutaneous melanoma tumor growth in vivo, compared to controls or either treatment alone. Thus, future experimental studies are warranted to validate SAS as a radiosensitizer in the treatment of metastatic melanoma. Future studies will also be aimed at assessing the effect on pulmonary melanoma metastasis.

Citation Format: Hilde Elise Førde, Linda Sleire, Heidi Espedal, Jan Ingemann Heggdal, Frode Selheim, Paal-Henning Pedersen, Per Øyvind Enger. Drug repurposing: Validation of sulfasalazine as a radiosensitizer in melanoma by blocking system Xc−. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3048.

Treatment with the PI3K inhibitor buparlisib (NVP-BKM120) suppresses the growth of established patient-derived GBM xenografts and prolongs survival in nude rats

Glioblastomas (GBMs) are aggressive brain tumours with a dismal prognosis, despite combined surgery, radio- and chemotherapy. Close to 90 % of all GBMs harbour a deregulated PI3K pathway, which is essential in regulating central cellular functions such as proliferation, cell growth, motility and survival. Thus, PI3K represents a potential target for molecular therapy in GBM. We investigated the anti-tumour efficacy of the PI3K inhibitor buparlisib (NVP-BKM120) in GBM cell lines in vitro and in vivo, when treatment was initiated after MRI-confirmed tumour engraftment. We found that buparlisib inhibited glioma cell proliferation in a dose dependent manner, demonstrated by MTS assay, manual cell count and BrdU incorporation. A dose dependent increase in apoptosis was observed through flow cytometric analysis. Furthermore, by immunocytochemistry and western blot, we found a dose dependent inhibition of Akt phosphorylation. Moreover, buparlisib prolonged survival of nude rats harboring human GBM xenografts in three independent studies and reduced the tumours’ volumetric increase, as determined by MRI. In addition, histological analyses of xenograft rat brains showed necrotic areas and change in tumour cell nuclei in buparlisib-treated animals. The rats receiving buparlisib maintained their weight, activity level and food- and water intake. In conclusion, buparlisib effectively inhibits glioma cell proliferation in vitro and growth of human GBM xenografts in nude rats. Moreover, the compound is well tolerated when administered at doses providing anti-tumour efficacy. Thus, buparlisib may have a future role in glioma therapy, and further studies are warranted to validate this compound for human use.

Abstract 1789: Drug repurposing: Sulfasalazine sensitizes gliomas to gamma knife surgery by blocking cystine uptake through System XC−, leading to gluthatione depletion

Glioblastomas (GBMs) are lethal cancers and inherently resistant to radiotherapy. Established treatments including surgery, radio- and chemotherapy have a limited efficacy, and the median survival is approximately 14.6 months. Thus, treatment resistance represents a major challenge in the clinical management of these patients, and new therapies are urgently needed.

We hypothesized that the Xc−-inhibitor sulfasalazine (SAS) could potentiate the efficacy of radiotherapy against gliomas. Expression of the catalytic subunit of system Xc−, xCT, was found in a panel of 30 human GBM biopsies. Sections from normal brain tissue displayed only weak immunopositivity, thus our findings therefore suggest that xCT expression is common to most GBMs, which together with its low expression in normal brain tissue could provide a therapeutic window. SAS treatment dramatically reduced cysteine-uptake and glutathione (GSH) levels in glioma cells in vitro and markedly increased the levels of reactive oxygen species (ROS). Furthermore, SAS and radiation synergistically increased DNA double-strand breaks and increased glioma cell death, whereas adding the antioxidant N-acetyl-L-cysteine (NAC) reversed cell death. Moreover, SAS and gamma knife radiosurgery (GKRS) synergistically prolonged survival in nude rats harboring human GBM xenografts, compared to controls or either treatment alone. In conclusion, SAS effectively blocks cystine uptake in glioma cells in vitro, leading to GSH depletion and increased ROS levels, DNA damage and cell death. Moreover, it potentiates the anti-tumor efficacy of GKRS in rats with human GBM xenografts, providing a survival benefit. Thus, SAS may have a role as a radiosensitizer to enhance the efficacy of current radiotherapies for glioma patients. We are currently preparing a clinical trial for patients with GBM recurrences combining pre-treatment with SAS and GKRS.

Citation Format: Linda Sleire, Bente Sandvei Skeie, Inger Anne Netland, Hilde Elise Førde, Ernest Dodoo, Frode Selheim, Lina Leiss, Jian Wang, Jan Heggdal, Paal-Henning Pedersen, Per Øyvind Enger. Drug repurposing: Sulfasalazine sensitizes gliomas to gamma knife surgery by blocking cystine uptake through System XC−, leading to gluthatione depletion. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1789. doi:10.1158/1538-7445.AM2015-1789

Drug repurposing: sulfasalazine sensitizes gliomas to gamma knife radiosurgery by blocking cystine uptake through system Xc-, leading to glutathione depletion

Glioblastomas (GBMs) are aggressive brain tumors that always recur after radiotherapy. Cystine, mainly provided by the system X(c)(-) antiporter, is a requirement for glioma cell synthesis of glutathione (GSH) which has a critical role in scavenging free radicals, for example, after radiotherapy. Thus, we hypothesized that the X(c)(-)-inhibitor sulfasalazine (SAS) could potentiate the efficacy of radiotherapy against gliomas. Here, we show that the catalytic subunit of system X(c)(-), xCT, was uniformly expressed in a panel of 30 human GBM biopsies. SAS treatment significantly reduced cystine uptake and GSH levels, whereas it significantly increased the levels of reactive oxygen species (ROS) in glioma cells in vitro. Furthermore, SAS and radiation synergistically increased DNA double-strand breaks and increased glioma cell death, whereas adding the antioxidant N-acetyl-L-cysteine (NAC) reversed cell death. Moreover, SAS and gamma knife radiosurgery (GKRS) synergistically prolonged survival in nude rats harboring human GBM xenografts, compared with controls or either treatment alone. In conclusion, SAS effectively blocks cystine uptake in glioma cells in vitro, leading to GSH depletion and increased ROS levels, DNA damage and cell death. Moreover, it potentiates the anti-tumor efficacy of GKRS in rats with human GBM xenografts, providing a survival benefit. Thus, SAS may have a role as a radiosensitizer to enhance the efficacy of current radiotherapies for glioma patients.

Abstract LB-66: NVP-BEZ235 and bevacizumab as therapy for glioblastoma

Glioblastoma (GBM) is the most common and aggressive primary brain tumour. Its dismal prognosis despite multimodal treatment comprising surgery, radiotherapy and chemotherapy, calls for new therapeutic strategies.

GBM is a highly vascularized cancer, with elevated expression levels of vascular endothelial growth factor (VEGF), a key mediator of angiogenesis. Bevacizumab is a humanized anti-VEGF monoclonal antibody in clinical use as an angiogenesis inhibitor. Although bevacizumab is approved for treatment of GBM, several studies now show that it does not prolong survival. In addition, it has been shown that bevacizumab treatment leads to increased invasion and upregulation of gene transcripts involved in phosphoinositol-3-kinase (PI3K) - pathways. NVP-BEZ235 is a dual PI3K/mTOR kinase inhibitor. Combining NVP-BEZ235 with bevacizumab may therefore target both the angiogenic and invasive phenotype of GBMs.In vitro, the U-87 glioma cell line showed a dose-dependent reduction in cell proliferation to doses of NVP-BEZ235 from 0 to 250nM, as shown by direct cell count, BrdU incorporation and MTS assay. Furthermore, this was accompanied by a dose-dependent reduction of phosphorylated Akt at Serine 473, while the total levels of Akt remained unchanged. An IC50 of 11nM NVP-BEZ235 for the tumour material implanted, was determined in vitro by MTS assay. In order to validate combination treatment of BEZ235 and Avastin in vivo, we utilized a clinically relevant patient-based GBM xenograft model in NOD/SCID mice that mimics both the invasive and angiogenic growth pattern of human GBMs. In total 40 mice were allocated to four groups that received combination treatment with Avastin/BEZ235, monotreatment with Avastin or BEZ235 and untreated controls. Tumor engraftment and growth was confirmed and monitored longitudinally with MRI. The study is ongoing, survival data including histopathological analysis will be presented.

Citation Format: Inger Anne Netland, Hilde Førde, Linda Sleire, Bente S. Skeie, Per Øyvind Enger, Dorota Goplen. NVP-BEZ235 and bevacizumab as therapy for glioblastoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr LB-66. doi:10.1158/1538-7445.AM2014-LB-66

Gamma knife surgery as monotherapy with clinically relevant doses prolongs survival in a human GBM xenograft model

OBJECT

Gamma knife surgery (GKS) may be used for recurring glioblastomas (GBMs). However, patients have then usually undergone multimodal treatment, which makes it difficult to specifically validate GKS independent of established treatments. Thus, we developed an experimental brain tumor model to assess the efficacy and radiotoxicity associated with GKS.

METHODS

GBM xenografts were implanted intracerebrally in nude rats, and engraftment was confirmed with MRI. The rats were allocated to GKS, with margin doses of 12 Gy or 18 Gy, or to no treatment. Survival time was recorded, tumor sections were examined, and radiotoxicity was evaluated in a behavioral open field test.

RESULTS

In the first series, survival from the time of implantation was 96 days in treated rats and 72 days in controls (P < 0.001). In a second experiment, survival was 72 days in the treatment group versus 54 days in controls (P < 0.006). Polynuclear macrophages and fibrosis was seen in groups subjected to GKS. Untreated rats with GBM xenografts displayed less mobility than GKS-treated animals in the open field test 4 weeks after treatment (P = 0.04).

CONCLUSION

GKS administered with clinically relevant doses prolongs survival in rats harboring GBM xenografts, and the associated toxicity is mild.

Abstract 1590: Sulfasalazine sensitizes glioblastoma cells to radiation treatment

Glioblastoma (GBM) is a lethal cancer with a limited response to ionizing radiation. Recent studies suggest that Sulfasalazine (SAS), a drug used to treat inflammatory bowel disease, inhibits the Xc− antiporter system in glioma cells, thereby blocking their uptake of cystein. Since the availability of cystein is a rate limiting step in intracellular antioxidant production, we wanted to investigate whether sulfasalazine sensitizes glioma cells to radiation.

Expression of xCT, the catalytic subunit of system Xc−, was found in 30 patient GBM biopsies. SAS effect on glioma cell growth was investigated using an electric cell substrate impedance sensing (ECIS) instrument. All glioma cell lines showed altered growth curves in response to SAS treatment. To assess the effect of blocking the antiporter, intracellular levels of the antioxidant glutathione were measured. With increasing doses of SAS, glutathione levels decreased in a dose response manner. In addition, cysteine was added to the medium to see if the toxic effects of SAS could be counteracted. Furthermore, accumulation of reactive oxygen species upon SAS treatment was measured. Glioma cells were also treated with escalating doses of SAS, alone or in combination with radiation (8 Gy). The presence of double stranded breaks increased markedly in the irradiated samples and also somewhat with increasing doses with SAS. In addition, cell death, viability and clonogenicity were investigated using live/dead staining, the MTS assay and the clonogenic assay.

All treatment groups exhibited increased rates of cell death compared to untreated controls. A combination of SAS and radiation resulted in higher levels of cell death, than radiation or SAS administered alone. Furthermore we continued with implantation of human GBMs into the brain of Nude rats. These animals were treated with Gamma Knife Radiosurgery alone or in combination with SAS. SAS were administered as a pre-treatment for three days before Radiosurgery. The rats receiving the combination treatment lived significantly longer compared to either treatment alone. Interestingly, the animals only receiving pre-treatment with SAS for three days lived significantly longer compared to the untreated controls, although this was not statistically significant. We are currently preparing a clinical trial for patients with GBM recurrences combining pre-treatment with Sulfasalazine and Gamma Knife Radiosurgery.

Citation Format: Linda Sleire, Bente S. Skeie, Inger A. Netland, Jan Heggdal, Paal-Henning Pedersen, Per Ø. Enger. Sulfasalazine sensitizes glioblastoma cells to radiation treatment. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1590. doi:10.1158/1538-7445.AM2013-1590

Establishment of a novel dsRed NOD/Scid mouse strain to investigate the host and tumor cell compartments

Here we describe a NOD/Scid mouse strain expressing the dsRed transgene. The strain is maintained by inbreeding of homozygous dsRed NOD/Scid siblings, and expresses red fluorescence from various organs. The model allows engraftment of human tumor tissue, and engrafted tumors were separated into stromal and malignant cell compartments. Furthermore, we compared tumor-associated and normal fibroblast for expression of fibroblast-associated markers, and identified a marker panel that was upregulated in the tumor-associated fibroblasts. In conclusion, we propose that this model may be used in a variety of studies of tumor progression and to elucidate the role of the tumor microenvironment.

Abstract 1456: Sulfasalazine sensitizes glioblastoma cells to radiation treatment

Glioblastoma (GBM) is a lethal cancer with a limited response to ionizing radiation. Recent studies suggest that Sulfasalazine (SAS), a drug used to treat inflammatory bowel disease, inhibits the Xc- antiporter system in glioma cells, thereby blocking their uptake of cystein. Since the availability of cystein is a rate limiting step in intracellular antioxidant production, we wanted to investigate whether sulfasalazine sensitizes glioma cells to radiation. Expression of xCT, the catalytic subunit of system Xc-, was found in 30 patient GBM biopsies. SAS effect on glioma cell growth was investigated using an electric cell substrate impedance sensing (ECIS) instrument. All glioma cell lines showed altered growth curves in response to SAS treatment. To assess the effect of blocking the antiporter, intracellular levels of the antioxidant glutathione were measured. With increasing doses of SAS, glutathione levels decreased in a dose response manner. In addition, cysteine was added to the medium to see if the cells could survive high doses of SAS. U251 glioma cells were treated with escalating doses of SAS, alone or in combination with radiation (8 Gy). Nuclear integrity was evaluated to estimate cell death following treatment, as well as the presence of double stranded breaks. In addition, cell death and viability were investigated using live/dead staining and the MTS assay. All treatment groups exhibited increased rates of cell death compared to untreated controls. A combination of SAS and radiation resulted in higher levels of cell death, than radiation or SAS administered alone. In order to assess whether this can be exploited therapeutically, we are preparing to treat nude rats harbouring glioblastoma biopsy xenografts with SAS, alone or in combination with gamma knife radiation.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1456. doi:1538-7445.AM2012-1456

Gene expression in tumor cells and stroma in dsRed 4T1 tumors in eGFP-expressing mice with and without enhanced oxygenation

Background

The tumor microenvironment is pivotal in tumor progression. Thus, we aimed to develop a mammary tumor model to elucidate molecular characteristics in the stroma versus the tumor cell compartment by global gene expression. Secondly, since tumor hypoxia influences several aspects of tumor pathophysiology, we hypothesized that hyperoxia might have an inhibitory effect on tumor growth per se. Finally, we aimed to identify differences in gene expression and key molecular mechanisms, both in the native state and following treatment.

Methods

4T1 dsRed breast cancer cells were injected into eGFP expressing NOD/SCID mice. Group 1 was exposed to 3 intermittent HBO treatments (Day 1, 4 and 7), Group 2 to 7 daily HBO treatments (both 2.5bar, 100% O₂, à 90 min), whereas the controls were exposed to a normal atmosphere. Tumor growth, histology, vascularisation, cell proliferation, cell death and metastasis were assessed. Fluorescence-activated cell sorting was used to separate tumor cells from stromal cells prior to gene expression analysis.

Results

The purity of sorted cells was verified by fluorescence microscopy. Gene expression profiling demonstrated that highly expressed genes in the untreated tumor stroma included constituents of the extracellular matrix and matrix metalloproteinases. Tumor growth was significantly inhibited by HBO, and the MAPK pathway was found to be significantly reduced. Immunohistochemistry indicated a significantly reduced microvessel density after intermittent HBO, whereas daily HBO did not show a similar effect. The anti-angiogenic response was reflected in the expression trends of angiogenic factors.

Conclusions

The present in vivo mammary tumor model enabled us to separate tumor and stromal cells, and demonstrated that the two compartments are characterized by distinct gene expressions, both in the native state and following HBO treatments. Furthermore, hyperoxia induced a significant tumor growth-inhibitory effect, with significant down-regulation of the MAPK pathway. An anti-angiogenic effect after intermittent HBO was observed, and reflected in the gene expression profile.

Neuronal markers are expressed in human gliomas and NSE knockdown sensitizes glioblastoma cells to radiotherapy and temozolomide

BACKGROUND

Expression of neuronal elements has been identified in various glial tumors, and glioblastomas (GBMs) with neuronal differentiation patterns have reportedly been associated with longer survival. However, the neuronal class III β-tubulin has been linked to increasing malignancy in astrocytomas. Thus, the significance of neuronal markers in gliomas is not established.

METHODS

The expressions of class III β-tubulin, neurofilament protein (NFP), microtubule-associated protein 2 (MAP2) and neuron-specific enolase (NSE) were investigated in five GBM cell lines and two GBM biopsies with immunocytochemistry and Western blot. Moreover, the expression levels were quantified by real-time qPCR under different culture conditions. Following NSE siRNA treatment we used Electric cell-substrate impedance sensing (ECIS) to monitor cell growth and migration and MTS assays to study viability after irradiation and temozolomide treatment. Finally, we quantitated NSE expression in a series of human glioma biopsies with immunohistochemistry using a morphometry software, and collected survival data for the corresponding patients. The biopsies were then grouped according to expression in two halves which were compared by survival analysis.

RESULTS

Immunocytochemistry and Western blotting showed that all markers except NFP were expressed both in GBM cell lines and biopsies. Notably, qPCR demonstrated that NSE was upregulated in cellular stress conditions, such as serum-starvation and hypoxia, while we found no uniform pattern for the other markers. NSE knockdown reduced the migration of glioma cells, sensitized them to hypoxia, radio- and chemotherapy. Furthermore, we found that GBM patients in the group with the highest NSE expression lived significantly shorter than patients in the low-expression group.

CONCLUSIONS

Neuronal markers are aberrantly expressed in human GBMs, and NSE is consistently upregulated in different cellular stress conditions. Knockdown of NSE reduces the migration of GBM cells and sensitizes them to hypoxia, radiotherapy and chemotherapy. In addition, GBM patients with high NSE expression had significantly shorter survival than patients with low NSE expression. Collectively, these data suggest a role for NSE in the adaption to cellular stress, such as during treatment.

Abstract 2499: Sulfasalazine sensitizes glioblastoma cells to radiation treatment

Glioblastomas (GBMs) are lethal cancers with a limited response to ionizing radiation. Recent studies suggest that Sulfasalazine (SAS), a drug used to treat inflammatory bowel disease, inhibits the xCT antiporter system in glioma cells, thereby blocking their uptake of cystein. Since the availability of cystein is a rate limiting step in intracellular antioxidant production, we wanted to investigate whether sulfasalazine sensitizes glioma cells to radiation.

SAS effect on glioma cell growth was investigated using an electric cell substrate impedance sensing (ECIS) instrument. All cell lines showed altered growth curves in response to SAS treatment. To assess the effect of blocking the xCT antiporter, intracellular levels of the antioxidant glutathione were measured. With increasing doses of SAS, glutathione levels decreased in a dose response manner. Further, U251 glioma cells were treated with escalating doses of SAS, alone or in combination with radiation (8 Gy). Nuclear integrity was evaluated to estimate cell death following treatment. In addition, cell death and viability were investigated using live/dead staining and MTS assay respectively.

All treatment groups exhibited increased rates of cell death compared to untreated controls. However, a combination of SAS and radiation resulted in higher levels of cell death, than radiation or SAS administered alone. In order to assess whether this can be exploited therapeutically, we are currently preparing to treat nude rats harbouring gliblastoma biopsy xenografts with SAS, alone or in combination with radiation.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2499. doi:10.1158/1538-7445.AM2011-2499

Abstract 528: A tumor-stroma interaction study in red mammary tumors in green mice with and without enhanced oxygenation

Background: The tumor microenvironment is increasingly recognized as pivotal in tumor progression. Thus, by completely separating tumor cells from stromal cells it enables a thorough elucidation of gene-changes in the two compartments, and thereby offers the possibility to better understand the biological effects in tumors with and without treatment.

Since tumor hypoxia is considered to be relevant for several aspects of tumor pathophysiology, including activation of signalling pathways that regulate proliferation, angiogenesis and death, our hypothesis was that a reduction in the hypoxic state of the tumor, might have an inhibitory effect on tumor growth per se. Induction of hyperoxia by hyperbaric oxygen (HBO) exposure, enhance dissolved oxygen in the plasma and thereby the pO2 in the tumor tissue.

Methods: The murine mammary dsRed cell line 4T1 was implanted into the mouse mammary fat pad in eGFP expressing NOD/Scid mice. One group was exposed to repeated HBO treatment (2.5 bar, 100% O2, 3 exposures à 90 min), one to daily HBO treatment (2.5bar, 100% O2, 7 exposures à 90 min), whereas the control group was housed under normal atmosphere. Treatment effects were determined by assessment of tumor growth, tumor vascularisation, tumor cell proliferation and cell death. FACS was used to completely separate red tumor cells from green host cells, RNA was extracted and gene expression profiling performed.

Results: The model enabled us to completely separate the two compartments (tumor vs stroma), as verified by confocal microscopy and gene expression profiling. Highly upregulated genes in the untreated tumor stroma, included constituents of the ECM and MMP's, as well as genes related to cell-migration and motility. Significant changes in response to treatment between the tumor and stroma was found, especially concerning genes related to cell adhesion and angiogenesis. Furthermore, changes occurring within each of these compartments were found. Tumor growth was significantly inhibited (∼ 50%, after 8 days) after both repeated and daily HBO treatment compared to controls. Repeated HBO treatment showed a significant anti-angiogenic effect, while daily HBO treatment did not. The gene expression confirmed this. Neither morphology, proliferation nor the amount of cell death was significantly changed after the two HBO treatment regimes, despite the significant effect on tumor growth.

Conclusion: The present model provides a significant insight into how tumor cells communicate with the stroma, both before any treatment and after enhanced oxygenation. Furthermore, hyperoxia induced a significant inhibitory effect on the 4T1 mammary tumor growth, with a significant anti-angiogenic effect after repeated hyperoxic treatment.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 528. doi:10.1158/1538-7445.AM2011-528

Abstract 4320: Separate analysis of the cancer and stroma cell populations from orthotopically implanted cancer cell lines in fluorescent mice

The tumour microenvironment is increasingly recognised as important in most aspects of tumourigenesis, from tumor formation, growth and invasion, to metastasis and priming of distant metastatic sites. It has been estimated that around 50% of a solid tumor mass may be of stromal origin, including cells of the immune system, endothelial cells and fibroblasts, with the latter being the most abundant. The fibroblasts recruited to a tumor are commonly known as cancer associated fibroblasts (CAFs), and are characterized by their heterogeneity of marker expression and origin, making them a challenge to study.

Therefore, we have developed a new strain of mice for the analysis of the tumour microenvironment in xenograft models. The strain was created by crossbreeding dsRed positive mice with severe combined immunodeficient (SCID) mice, and backcrossing on a SCID background until we obtained a homozygous dsRed-SCID inbred strain. As the tumor cells implanted are non-fluorescent, whereas the stromal contributions to the growing tumors are dsRed positive, the two compartments were successfully separated by Fluorescence-activated cell sorting (FACS) after mechanical and enzymatic dissociation.

The dsRed phenotype is visibly red with the naked eye, and fluoresces under a 488 nm dark reader lamp light. The organs have been confirmed dsRed positive by imaging and further confirmed and quantified by RT-PCR. The SCID phenotype was confirmed by immune phenotyping, using markers for B, T, Tc, Th and NK cells. Furthermore, the mice were confirmed immune deficient when they were orthotopicaly grafted with breast (4T1) and lung (A549) cancer cell lines.

Fibroblast enriched populations were isolated from primary A549 tumours, 4T1 tumours and 4T1 tumour metastasis to the lungs, by subsorting the dsRed positive stromal compartment, excluding cells of the immune system and endothelial cells. Preliminary data clearly show distinct tumor and stroma populations in primary breast and lung cancer, as well as in lung metastasis from breast cancer xenografts. Furthermore, when investigating the breast cancers dissociated at different time points from implantation, it is clear that the percentage of stromal cells in the overall tumour mass decreases as the tumour grows. The fibroblasts were further analyzed for marker expression, cell cycle phase distribution and in vitro growth properties. We conclude that this model provides a valuable tool for investigating the stromal compartment of xenograft tumours.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4320. doi:10.1158/1538-7445.AM2011-4320

Abstract LB-169: Sulfasalazine sensitizes glioblastoma cells to radiation treatment

Glioblastomas (GBMs) are lethal cancers with a limited response to ionizing radiation. Recent studies suggest that Sulfasalazine (SAS), a drug used to treat inflammatory bowel disease, inhibits the xCT antiporter system in glioma cells, thereby blocking their uptake of cystine. Since the availability of cystine is a rate limiting step in intracellular antioxidant production, we wanted to investigate whether sulfasalazine sensitizes glioma cells to radiation. SAS effect on glioma cell growth was investigated using a electric cell substrate impedance sensing (ECIS) instrument. All cell lines showed altered growth curves in response to SAS treatment. Further, U251 glioma cells were treated with escalating doses of SAS, alone or in combination with radiation (8 Gy). Immunocytochemistry for the apoptotic marker Annexin V as well as DAPI staining to assess nuclear integrity were conducted to estimate cell death following treatment.

All treatment groups exhibited increased rates of cell death compared to untreated controls. However, a combination of SAS and radiation resulted in higher levels of cell death, than radiation or SAS administered alone. In order to assess whether this can be exploited therapeutically, we are currently preparing to treat nude rats harbouring gliblastoma biopsy xenografts with SAS, alone or in combination with radiation.

Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr LB-169.

Induction of circadian rhythm in cultured human mesenchymal stem cells by serum shock and cAMP analogs in vitro

Circadian clocks have been shown to operate developmentally in mouse and human hematopoietic stem and progenitor cells in vivo, but little is known about their possible oscillations in vitro. Here, we show that repeated circadian oscillations could be induced in both cultured bone marrow-derived mesenchymal- and adipose-derived stem cells (MSCs and ASCs, respectively) by serum shock. In particular, the novel finding of rhythmic clock gene expression induced by cAMP analogs showed similarities as well as differences to serum-induced oscillations. Rhythmic PER1 expression was found in serum-shocked MSCs, suggesting the phosphorylation status of PER1 is important for its activity in circadian rhythms. Furthermore, immunofluoresent staining showed that the localization of PER1 was dependent on the level of PER1 expression. These inducible self-sustained circadian clocks in primary cultures of human MSCs in vitro with rhythmic changes in expression levels, phosphorylation, and localization of clock protein, PER1, may be of importance for maintaining the induced oscillations in stem cells. Therefore, the established cell models described here appear to be valuable for studying the molecular mechanism driving and coordinating the circadian network between stem and stromal cells.