RESUMO
Hepatocellular carcinoma (HCC) is one of the leading causes of cancer death worldwide. Cancer stem cells (CSCs) have attracted attention as a novel therapeutic target for cancer because they play important roles in the development and aggravation of cancer. CD44 is expressed as a standard isoform (CD44s) and several variant isoforms. CD44v is a major isoform expressed on CSCs of a variety of tumors and has been extensively studied. However, HCC tissues dominantly express CD44s, whose function in CSCs remains unclear. In the present study, we investigated the roles of CD44s in CSCs of HCC. Knock-out of the CD44 gene in HuH7 HCC cells on which only CD44s is expressed resulted in decreased spheroid formation and increased drug sensitivity. The expression of CSC marker genes, including CD133 and EpCAM, was significantly downregulated in the spheroids of CD44-deficient cells compared with those in the spheroids of HuH7 cells. In addition, CD44 deficiency impaired antioxidant capacity, concomitant with downregulation of glutathione peroxidase 1 (GPX1) and thioredoxin. Because GPX1 uses the reduced form of glutathione (GSH) to regenerate oxidized cellular components, GSH levels were significantly increased in the CD44-deficient cells. We also found that NOTCH3 and its target genes were downregulated in the spheroids of CD44-deficient cells. NOTCH3 expression in HCC tissues was significantly increased compared with that in adjacent nontumor liver tissues and was correlated with CD44 expression. These results suggest that CD44s is involved in maintenance of CSCs in a HCC cell line, possibly through the NOTCH3 signaling pathway.
Assuntos
Carcinoma Hepatocelular , Receptores de Hialuronatos , Neoplasias Hepáticas , Células-Tronco Neoplásicas , Receptor Notch3 , Idoso , Carcinoma Hepatocelular/genética , Carcinoma Hepatocelular/metabolismo , Linhagem Celular Tumoral , Resistencia a Medicamentos Antineoplásicos , Feminino , Glutationa/metabolismo , Humanos , Receptores de Hialuronatos/genética , Receptores de Hialuronatos/metabolismo , Neoplasias Hepáticas/genética , Neoplasias Hepáticas/metabolismo , Masculino , Pessoa de Meia-Idade , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Receptor Notch3/genética , Receptor Notch3/metabolismo , Transdução de SinaisRESUMO
BACKGROUND/AIM: Colorectal cancer (CRC) is one of the most malignant types of cancer worldwide. Recent studies suggest that a small subpopulation of cells, so-called cancer stem cells (CSCs), promote the high metastasis and relapse associated with CRC. WNT/ß-catenin signaling plays a critical role in CSC maintenance. Therefore, its inhibitor may suppress CSCs and improve therapeutic effects on CRC. MATERIALS AND METHODS: The effects of a derivative of WNT/ß-catenin signaling inhibitor, IC-2, which we recently developed, on the CRC cell line DLD-1, were examined by luciferase reporter assay, WST assay, western blot, and sphere assay. RESULTS: The reporter assay showed that IC-2 reduced WNT/ß-catenin transcriptional activity in DLD-1 cells. Notably, IC-2 reduced expression levels of CSC marker proteins, as well as sphere formation. In addition, IC-2 increasesd cytotoxicity of 5-fluorouracil (5-FU) in DLD-1 cells. CONCLUSION: These results suggest that the combination treatment of IC-2 and 5-FU can stimulate tumor-suppressive effects on CRC.