Dataset Information

The cystine/glutamate antiporter system xc- drives breast tumor cell glutamate release and cancer-induced bone pain.

ABSTRACT: Bone is one of the leading sites of metastasis for frequently diagnosed malignancies, including those arising in the breast, prostate and lung. Although these cancers develop unnoticed and are painless in their primary sites, bone metastases result in debilitating pain. Deeper investigation of this pain may reveal etiology and lead to early cancer detection. Cancer-induced bone pain (CIBP) is inadequately managed with current standard-of-care analgesics and dramatically diminishes patient quality of life. While CIBP etiology is multifaceted, elevated levels of glutamate, an excitatory neurotransmitter, in the bone-tumor microenvironment may drive maladaptive nociceptive signaling. Here, we establish a relationship between the reactive nitrogen species peroxynitrite, tumor-derived glutamate, and CIBP. In vitro and in a syngeneic in vivo model of breast CIBP, murine mammary adenocarcinoma cells significantly elevated glutamate via the cystine/glutamate antiporter system xc. The well-known system xc inhibitor sulfasalazine significantly reduced levels of glutamate and attenuated CIBP-associated flinching and guarding behaviors. Peroxynitrite, a highly reactive species produced in tumors, significantly increased system xc functional expression and tumor cell glutamate release. Scavenging peroxynitrite with the iron and mangano-based porphyrins, FeTMPyP and SRI10, significantly diminished tumor cell system xc functional expression, reduced femur glutamate levels and mitigated CIBP. In sum, we demonstrate how breast cancer bone metastases upregulate a cystine/glutamate co-transporter to elevate extracellular glutamate. Pharmacological manipulation of peroxynitrite or system xc attenuates CIBP, supporting a role for tumor-derived glutamate in CIBP and validating the targeting of system xc as a novel therapeutic strategy for the management of metastatic bone pain.

SUBMITTER: Slosky LM

PROVIDER: S-EPMC5065056 | biostudies-literature | 2016 Nov

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

The cystine/glutamate antiporter system xc- drives breast tumor cell glutamate release and cancer-induced bone pain.

Slosky Lauren M LM BassiriRad Neemah M NM Symons Ashley M AM Thompson Michelle M Doyle Timothy T Forte Brittany L BL Staatz William D WD Bui Lynn L Neumann William L WL Mantyh Patrick W PW Salvemini Daniela D Largent-Milnes Tally M TM Vanderah Todd W TW

Pain 20161101 11

Bone is one of the leading sites of metastasis for frequently diagnosed malignancies, including those arising in the breast, prostate and lung. Although these cancers develop unnoticed and are painless in their primary sites, bone metastases result in debilitating pain. Deeper investigation of this pain may reveal etiology and lead to early cancer detection. Cancer-induced bone pain (CIBP) is inadequately managed with current standard-of-care analgesics and dramatically diminishes patient qualit ...[more]

PMID: 27482630

Similar Datasets

Project description:The cystine-glutamate antiporter (system xc-) is a Na+-independent amino acid transporter that exchanges extracellular cystine for intracellular glutamate. It is thought to play a critical role in cellular redox processes through regulation of intracellular glutathione synthesis via cystine uptake. In gliomas, system xc- expression is universally up-regulated while that of glutamate transporters down-regulated, leading to a progressive accumulation of extracellular glutamate and excitotoxic cell death of the surrounding non-tumorous tissue. Additionally, up-regulation of system xc- in activated microglia has been implicated in the pathogenesis of several neurodegenerative disorders mediated by excess glutamate. Consequently, system xc- is a new drug target for brain cancer and neuroinflammatory diseases associated with excess extracellular glutamate. Unfortunately no potent and selective small molecule system xc- inhibitors exist and to our knowledge, no high throughput screening (HTS) assay has been developed to identify new scaffolds for inhibitor design. To develop such an assay, various neuronal and non-neuronal human cells were evaluated as sources of system xc-. Human glioma cells were chosen based on their high system xc- activity. Using these cells, [14C]-cystine uptake and cystine-induced glutamate release assays were characterized and optimized with respect to cystine and protein concentrations and time of incubation. A pilot screen of the LOPAC/NINDS libraries using glutamate release demonstrated that the logistics of the assay were in place but unfortunately, did not yield meaningful pharmacophores. A larger, HTS campaign using the 384-well cystine-induced glutamate release as primary assay and the 96-well 14C-cystine uptake as confirmatory assay is currently underway. Unexpectedly, we observed that the rate of cystine uptake was significantly faster than the rate of glutamate release in human glioma cells. This was in contrast to the same rates of cystine uptake and glutamate release previously reported in normal human fibroblast cells.

Project description:BackgroundThe cystine/glutamate antiporter (xc-) has been implicated in several neurological disorders and, specifically, in multiple sclerosis (MS) as a mediator of glutamate excitotoxicity and proinflammatory immune responses. We aimed to evaluate an xc-specific positron emission tomography (PET) radiotracer, (4S)-4-(3-[18F]fluoropropyl)-L-glutamate ([18F]FSPG), for its ability to allow non-invasive monitoring of xc- activity in a mouse model of MS.MethodsExperimental autoimmune encephalomyelitis (EAE) was induced in C57BL/6 mice by subcutaneous injection of myelin oligodendrocyte glycoprotein (MOG35-55) peptide in complete Freund's adjuvant (CFA) followed by pertussis toxin. Control mice received CFA emulsion and pertussis toxin without MOG peptide, while a separate cohort of naïve mice received no treatment. PET studies were performed to investigate the kinetics and distribution of [18F]FSPG in naïve, control, pre-symptomatic, and symptomatic EAE mice, compared to 18F-fluorodeoxyglucose ([18F]FDG). After final PET scans, each mouse was perfused and radioactivity in dissected tissues was measured using a gamma counter. Central nervous system (CNS) tissues were further analyzed using ex vivo autoradiography or western blot. [18F]FSPG uptake in human monocytes, and T cells pre- and post-activation was investigated in vitro.Results[18F]FSPG was found to be more sensitive than [18F]FDG at detecting pathological changes in the spinal cord and brain of EAE mice. Even before clinical signs of disease, a small but significant increase in [18F]FSPG signal was observed in the spinal cord of EAE mice compared to controls. This increase in PET signal became more pronounced in symptomatic EAE mice and was confirmed by ex vivo biodistribution and autoradiography. Likewise, in the brain of symptomatic EAE mice, [18F]FSPG uptake was significantly higher than controls, with the largest changes observed in the cerebellum. Western blot analyses of CNS tissues revealed a significant correlation between light chain of xc- (xCT) protein levels, the subunit of xc- credited with its transporter activity, and [18F]FSPG-PET signal. In vitro [18F]FSPG uptake studies suggest that both activated monocytes and T cells contribute to the observed in vivo PET signal.ConclusionThese data highlight the promise of [18F]FSPG-PET as a technique to provide insights into neuroimmune interactions in MS and the in vivo role of xc- in the development and progression of this disease, thus warranting further investigation.

Project description:BackgroundThe upregulation of antioxidant mechanisms is a common occurrence in cancer cells, as they strive to maintain balanced redox state and prevent oxidative damage. This includes the upregulation of the cystine/glutamate antiporter xCT, which plays a crucial role in protecting cancer cells from oxidative stress. Consequently, targeting xCT has become an attractive strategy for cancer treatment. However, xCT is also expressed by several types of immune cells where it has a role in proliferation and effector functions. In light of these observations, a comprehensive understanding of the specific role of xCT in the initiation and progression of cancer, as well as its potential impact on the immune system within the tumor microenvironment and the anti-tumor response, require further investigation.MethodsWe generated xCTnull BALB/c mice to investigate the role of xCT in the immune system and xCTnull/Erbb2-transgenic BALB-neuT mice to study the role of xCT in a mammary cancer-prone model. We also used mammary cancer cells derived from BALB-neuT/xCTnull mice and xCTKO 4T1 cells to test the contribution of xCT to malignant properties in vitro and in vivo.ResultsxCT depletion in BALB-neuT/xCTnull mice does not alter autochthonous tumor initiation, but tumor cells isolated from these mice display proliferation and redox balance defects in vitro. Although xCT disruption sensitizes 4T1 cells to oxidative stress, it does not prevent transplantable tumor growth, but reduces cell migration in vitro and lung metastasis in vivo. This is accompanied by an altered immune cell recruitment in the pre-metastatic niche. Finally, systemic depletion of xCT in host mice does not affect transplantable tumor growth and metastasis nor impair the proper mounting of both humoral and cellular immune responses in vivo.ConclusionsxCT is dispensable for proper immune system function, thus supporting the safety of xCT targeting in oncology. Nevertheless, xCT is involved in several processes required for the metastatic seeding of mammary cancer cells, thus broadening the scope of xCT-targeting approaches.

Dataset Information

The cystine/glutamate antiporter system xc- drives breast tumor cell glutamate release and cancer-induced bone pain.

Publications

The cystine/glutamate antiporter system xc- drives breast tumor cell glutamate release and cancer-induced bone pain.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets