RESUMO
Diffuse intrinsic pontine gliomas (DIPG), the first cause of cerebral pediatric cancer death, will greatly benefit from specific and non-invasive biomarkers for patient follow-up and monitoring of drug efficacy. Since biopsies are challenging for brain tumors, molecular imaging may be a technique of choice to target and follow tumor evolution. So far, MR remains the imaging technique of reference for DIPG, although it often fails to define the extent of tumors, an essential parameter for therapeutic efficacy assessment. Thanks to its high sensitivity, positron emission tomography (PET) offers a unique way to target specific biomarkers in vivo. We demonstrated in a patient-derived orthotopic xenograft (PDOX) model in the rat that the translocator protein of 18 kDa (TSPO) may be a promising biomarker for monitoring DIPG tumors. We studied the distribution of 18F-DPA-714, a TSPO radioligand, in rats inoculated with HSJD-DIPG-007 cells. The primary DIPG human cell line HSJD-DIPG-007 highly represents this pediatric tumor, displaying the most prevalent DIPG mutations, H3F3A (K27M) and ACVR1 (R206H). Kinetic modeling and parametric imaging using the brain 18F-DPA-714 PET data enabled specific delineation of the DIPG tumor area, which is crucial for radiotherapy dose management.
Assuntos
Astrocitoma , Neoplasias do Tronco Encefálico , Glioma Pontino Intrínseco Difuso , Glioma , Criança , Animais , Humanos , Ratos , Glioma/diagnóstico por imagem , Glioma/genética , Glioma/metabolismo , Linhagem Celular Tumoral , Neoplasias do Tronco Encefálico/diagnóstico por imagem , Neoplasias do Tronco Encefálico/genética , Tomografia por Emissão de Pósitrons/métodos , Proteínas de Transporte , Modelos Animais de Doenças , Biomarcadores , Receptores de GABA/genética , Receptores de GABA/metabolismo , Receptores de GABA-ARESUMO
Neurodegeneration elicits neuroinflammatory responses to kill pathogens, clear debris and support tissue repair. Neuroinflammation is a dynamic biological response characterized by the recruitment of innate and adaptive immune system cells in the site of tissue damage. Resident microglia and infiltrating immune cells partake in the restoration of central nervous system homeostasis. Nevertheless, their activation may shift to chronic and aggressive responses, which jeopardize neuron survival and may contribute to the disease process itself. Positron Emission Tomography (PET) molecular imaging represents a unique tool contributing to in vivo investigating of neuroinflammatory processes in patients. In the present review, we first provide an overview on the molecular basis of neuroinflammation in neurodegenerative diseases with emphasis on microglia activation, astrocytosis and the molecular targets for PET imaging. Then, we review the state-of-the-art of in vivo PET imaging for neuroinflammation in dementia conditions associated with different proteinopathies, such as Alzheimer's disease, frontotemporal lobar degeneration and Parkinsonian spectrum.
Assuntos
Doença de Alzheimer/diagnóstico por imagem , Tomografia por Emissão de Pósitrons/métodos , Doença de Alzheimer/metabolismo , Doença de Alzheimer/patologia , Humanos , Inflamação/diagnóstico por imagem , Microglia/metabolismo , Microglia/patologia , Receptores de GABA/metabolismoRESUMO
Translocator protein (TSPO) is involved in several cellular mechanisms such as steroidogenesis, immunomodulation, cell proliferation and differentiation. Overexpressed in several neurodegenerative diseases and brain cancer, TSPO radioligands have been developed over the last 20 years in positron emission tomography (PET) imaging. Recently, TSPO radioligands have extended beyond their initial application due to their specific binding to activated macrophages, making them a compelling biomarker for deciphering the intricacies of the tumor microenvironment (TME). In this review, we synthesized recent progress from the evaluation of TSPO-specific PET tracers in various peripheral tumor models and highlighted the hurdles and limitations associated with heterogeneous uptake in healthy tissue and tumor regions to achieve the clinical development of such a radiotracer.