RESUMO
Radiotherapy is a leading treatment for various types of cancer. However, exposure to high-dose ionizing radiation causes acute gastrointestinal injury and gastrointestinal syndrome. This has significant implications for human health, and therefore, radioprotection is a major area of research. Radiation induces the loss of intestinal stem cells; hence, the protection of stem cells expressing LGR5 (a marker of intestinal epithelial stem cells) is a key strategy for the prevention of radiation-induced injury. In this study, we identified valproic acid (VPA) as a potent radioprotector using an intestinal organoid culture system. VPA treatment increased the number of LGR5+ stem cells and organoid regeneration after irradiation. N-[N-(3,5-difluorophenacetyl)-l-alanyl]-S-phenylglycine t-butyl ester (DAPT, an inhibitor of NOTCH signaling) blocked the radioprotective effects of VPA, indicating that NOTCH signaling is a likely mechanism underlying the observed effects of VPA. In addition, VPA acted as a radiosensitizer via the inhibition of histone deacetylase (HDAC) in a colorectal cancer organoid. These results demonstrate that VPA exerts strong protective effects on LGR5+ stem cells via NOTCH signaling and that the inhibition of NOTCH signaling reduces these protective effects, providing a basis for the improved management of radiation injury.
Assuntos
Neoplasias/radioterapia , Organoides/efeitos dos fármacos , Substâncias Protetoras/farmacologia , Lesões por Radiação/tratamento farmacológico , Ácido Valproico/farmacologia , Animais , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Receptores Notch/metabolismoRESUMO
Enhancing the radioresponsiveness of colorectal cancer (CRC) is essential for local control and prognosis. However, consequent damage to surrounding healthy cells can lead to treatment failure. We hypothesized that shortchain fatty acids (SCFAs) could act as radiosensitizers for cancer cells, allowing the administration of a lower and safer dose of radiation. To test this hypothesis, the responses of threedimensionalcultured organoids, derived from CRC patients, to radiotherapy, as well as the effects of combined radiotherapy with the SCFAs butyrate, propionate and acetate as candidate radiosensitizers, were evaluated via reverse transcriptionquantitative polymerase chain reaction, immunohistochemistry and organoid viability assay. Of the three SCFAs tested, only butyrate suppressed the proliferation of the organoids. Moreover, butyrate significantly enhanced radiationinduced cell death and enhanced treatment effects compared with administration of radiation alone. The radiationbutyrate combination reduced the proportion of Ki67 (proliferation marker)positive cells and decreased the number of S phase cells via FOXO3A. Meanwhile, 3/8 CRC organoids were found to be nonresponsive to butyrate with lower expression levels of FOXO3A compared with the responsive cases. Notably, butyrate did not increase radiationinduced cell death and improved regeneration capacity after irradiation in normal organoids. These results suggest that butyrate could enhance the efficacy of radiotherapy while protecting the normal mucosa, thus highlighting a potential strategy for minimizing the associated toxicity of radiotherapy.
Assuntos
Ácido Butírico/administração & dosagem , Quimiorradioterapia Adjuvante/métodos , Neoplasias do Colo/terapia , Proteína Forkhead Box O3/metabolismo , Neoplasias Retais/terapia , Idoso , Idoso de 80 Anos ou mais , Técnicas de Cultura de Células , Colectomia , Colo/citologia , Colo/efeitos dos fármacos , Colo/patologia , Colo/efeitos da radiação , Neoplasias do Colo/patologia , Colonoscopia , Feminino , Humanos , Mucosa Intestinal/citologia , Mucosa Intestinal/efeitos dos fármacos , Mucosa Intestinal/patologia , Mucosa Intestinal/efeitos da radiação , Masculino , Pessoa de Meia-Idade , Organoides , Protectomia , Neoplasias Retais/patologia , Reto/citologia , Reto/efeitos dos fármacos , Reto/patologia , Reto/efeitos da radiaçãoRESUMO
Shikonin derivatives, which are the active components of the medicinal plant Lithospermum erythrorhizon, exhibit many biological effects including apoptosis induction through undefined mechanisms. We recently discovered that orphan nuclear receptor Nur77 migrates from the nucleus to the mitochondria, where it binds to Bcl-2 to induce apoptosis. Here, we report that certain shikonin derivatives could modulate the Nur77/Bcl-2 apoptotic pathway by increasing levels of Nur77 protein and promoting its mitochondrial targeting in cancer cells. Structural modification of acetylshikonin resulted in the identification of a derivative 5,8-diacetoxyl-6-(1'-acetoxyl-4'-methyl-3'-pentenyl)-1,4-naphthaquinones (SK07) that exhibited improved efficacy and specificity in activating the pathway. Unlike other Nur77 modulators, shikonins increased the levels of Nur77 protein through their posttranscriptional regulation. The apoptotic effect of SK07 was impaired in Nur77 knockout cells and suppressed by cotreatment with leptomycin B that inhibited Nur77 cytoplasmic localization. Furthermore, SK07 induced apoptosis in cells expressing the COOH-terminal half of Nur77 protein but not its NH(2)-terminal region. Our data also showed that SK07-induced apoptosis was associated with a Bcl-2 conformational change and Bax activation. Together, our results show that certain shikonin derivatives act as modulators of the Nur77-mediated apoptotic pathway and identify a new shikonin-based lead that targets Nur77 for apoptosis induction.