HMGB1 Mediates Endogenous TLR2 Activation and Brain Tumor Regression
Background Glioblastoma multiforme (GBM) is the most aggressive primary brain tumor that carries a 5-y survival rate of 5%. Attempts at eliciting a clinically relevant anti-GBM immune response in brain tumor patients have met with limited success, which is due to brain immune privilege, tumor immune evasion, and a paucity of dendritic cells (DCs) within the central nervous system. Herein we uncovered a novel pathway for the activation of an effective anti-GBM immune response mediated by high-mobility-group box 1 (HMGB1), an alarmin protein released from dying tumor cells, which acts as an endogenous ligand for Toll-like receptor 2 (TLR2) signaling on bone marrow-derived GBM-infiltrating DCs. Methods and Findings Using a combined immunotherapy/conditional cytotoxic approach that utilizes adenoviral vectors (Ad) expressing Fms-like tyrosine kinase 3 ligand (Flt3L) and thymidine kinase (TK) delivered into the tumor mass, we demonstrated that CD4+ and CD8+ T cells were required for tumor regression and immunological memory. Increased numbers of bone marrow-derived, tumor-infiltrating myeloid DCs (mDCs) were observed in response to the therapy. Infiltration of mDCs into the GBM, clonal expansion of antitumor T cells, and induction of an effective anti-GBM immune response were TLR2 dependent. We then proceeded to identify the endogenous ligand responsible for TLR2 signaling on tumor-infiltrating mDCs. We demonstrated that HMGB1 was released from dying tumor cells, in response to Ad-TK (+ gancyclovir [GCV]) treatment. Increased levels of HMGB1 were also detected in the serum of tumor-bearing Ad-Flt3L/Ad-TK (+GCV)-treated mice. Specific activation of TLR2 signaling was induced by supernatants from Ad-TK (+GCV)-treated GBM cells; this activation was blocked by glycyrrhizin (a specific HMGB1 inhibitor) or with antibodies to HMGB1. HMGB1 was also released from melanoma, small cell lung carcinoma, and glioma cells treated with radiation or temozolomide. Administration of either glycyrrhizin or anti-HMGB1 immunoglobulins to tumor-bearing Ad-Flt3L and Ad-TK treated mice, abolished therapeutic efficacy, highlighting the critical role played by HMGB1-mediated TLR2 signaling to elicit tumor regression. Therapeutic efficacy of Ad-Flt3L and Ad-TK (+GCV) treatment was demonstrated in a second glioma model and in an intracranial melanoma model with concomitant increases in the levels of circulating HMGB1. Conclusions Our data provide evidence for the molecular and cellular mechanisms that support the rationale for the clinical implementation of antibrain cancer immunotherapies in combination with tumor killing approaches in order to elicit effective antitumor immune responses, and thus, will impact clinical neuro-oncology practice.
MicroRNAs in cerebrospinal fluid identify glioblastoma and metastatic brain cancers and reflect disease activity.
An accurate, nonsurgical diagnostic test for brain tumors is currently unavailable, and the methods of monitoring disease progression are not fully reliable. MicroRNA profiling of biological fluids has recently emerged as a diagnostic tool for several pathologic conditions. Here we tested whether microRNA profiling of cerebrospinal fluid (CSF) enables detection of glioblastoma, discrimination between glioblastoma and metastatic brain tumors, and reflects disease activity. We determined CSF levels of several cancer-associated microRNAs for 118 patients diagnosed with different types of brain cancers and nonneoplastic neuropathologies by quantitative reverse transcription PCR analysis. The levels of miR-10b and miR-21 are found significantly increased in the CSF of patients with glioblastoma and brain metastasis of breast and lung cancer, compared with tumors in remission and a variety of nonneoplastic conditions. Members of the miR-200 family are highly elevated in the CSF of patients with brain metastases but not with any other pathologic conditions, allowing discrimination between glioblastoma and metastatic brain tumors. Quantification of as few as 7 microRNAs in CSF enables differential recognition of glioblastoma and metastatic brain cancer using computational machine learning tools (Support Vector Machine) with high accuracy (91%-99%) on a test set of samples. Furthermore, we show that disease activity and treatment response can be monitored by longitudinal microRNA profiles in the CSF of glioblastoma and non-small cell lung carcinoma patients. This study demonstrates that microRNA-based detection of brain malignancies can be reliably performed and that microRNAs in CSF can serve as biomarkers of treatment response in brain cancers.
neural network support vector machine deep learning convolutional neural network convolutional neural image segmentation magnetic resonance magnetic resonance imaging division multiple acces resonance imaging confidence interval rayleigh fading channel division multiple bayesian model conditional random field human brain brain tumor block code magnetic resonance image classification problem turbo code mri image decoding algorithm nervous system convolutional code stem cell automatic segmentation analysis and application space-time block positron emission tomography white matter space-time block code transmit antenna emission tomography biometric authentication cellular phone positron emission tumor segmentation central nervous system time division multiple graph partitioning brain tumor segmentation bch code space-time code space-time block coding tumor detection piston pump tumor growth central nervou linear block code partitioning algorithm tumor cell linear block orthogonal space-time block biometric authentication system brain tumor detection sensor location brain magnetic resonance axial piston growth factor diagnostic accuracy axial piston pump orthogonal space-time tumor classification national cancer emergent behavior current concept bayesian modelling rat brain brain tumor classification brain tumor image quasi-orthogonal space-time block graph partitioning algorithm tumor image automatic brain tumor glioblastoma multiforme neural stem cell number of transmit emergent technology contrast media multimodal brain tumor tumor segmentation method neural stem tumor image segmentation tumor type brain tumor patient malignant brain tumor brain tumor type primary brain tumor human brain tumor pediatric brain malignant brain tumor imaging brain tumor growth brain tumor surgery primary brain tumor surgery k-way partitioning primary malignant neoplasm of brain anaplastic astrocytoma cns disorder non-small cell lung carcinoma protein tyrosine kinase adverse reaction to drug recurrent childhood brain stem glioma brain neoplasm childhood brain stem glioma neoplasms, intracranial pituitary neoplasm millimole per kilogram angiogenic proces xenograft procedure small cell carcinoma of lung gadopentetate dimeglumine hematology (discipline) high-grade childhood cerebral astrocytoma childhood brain tumor united state