Abstract 5331: CHK1 inhibition enhances chemosensitivity of p53 deficient osteosarcoma cells

Abstract

Listen

Translate article

Abstract Osteosarcoma is the most common malignant bone tumor in children. Using expression profiling, we have previously identified a 45-gene chemoresistance signature in osteosarcoma that can predict tumor response to neo-adjuvant chemotherapy. One of the signature genes is CHEK1, which was expressed significantly higher in osteosarcomas that respond poorly to neoadjuvant chemotherapy. CHEK1 encodes a Serine/threonine-protein kinase CHK1 that regulates both G2/M and S phases of the cell cycle mainly through phosphorylation of CDC25, and particularly controls the entry into mitosis. In this study, we used two independent short hairpin RNA (shRNA) constructs to knock-down CHEK1 expression in a p53-mutated osteosarcoma cell line 143B and a p53- wild type osteosarcoma cell line U2OS. The results show that the stably transduced CHEK1 knock-down 143B cells, but not U2OS cells, became more sensitive to both doxorubicin and cisplatin treatment relative to the parental or scrambled control cells. The results of the cytotoxicity assay were confirmed by clonogenic assay using 143B and U2OS stable transfectants. Using a CHK1 inhibitor UCN-01, we found that mutation status of p53 in different osteosarcoma cells lines correlated with their sensitivity to doxorubicin or cisplatin in the presence of UCN-01. Using flow cytometry, we also validated the activity of UCN-01 in abolishing the cell cycle arrest induced by doxorubicin or cisplatin treatment in 143B cells. In summary, our results confirm that CHEK1 expression is not only a potential biomarker for predicting chemoresistance in osteosarcoma, but also potentially represents a therapeutic target for overcoming chemoresistance in osteosarcoma with the use of small molecule CHK1 inhibitors. Further experiments involving in vivo orthotropic xenograft mouse model with both CHEK1 knock-down osteosarcoma cells and CHK1 inhibitors is underway. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5331. doi:10.1158/1538-7445.AM2011-5331