title: The Chk1 inhibitor MK-8776 increases the radiosensitivity of human triple-negative breast cancer by inhibiting autophagy.
abstract: MK-8776 is a recently described inhibitor that is highly selective for checkpoint kinase 1 (Chk1), which can weaken the DNA repair capacity in cancer cells to achieve chemo-sensitization. A number of studies show that MK-8776 enhances the cytotoxicity of hydroxyurea and gemcitabine without increasing normal tissue toxicities. Thus far, there is no evidence that MK-8776 can be used as a radiotherapy sensitization agent. In this study, we investigated the effects of MK-8776 on the radiosensitivity of 3 human triple-negative breast cancer (TNBC) cell lines MDA-MB-231, BT-549 and CAL-51. MK-8776 dose-dependently inhibited the proliferation of MDA-MB-231, BT-549 and CAL-51 cells with IC50values of 9.4, 17.6 and 2.1 μmol/L, respectively. Compared with irradiation-alone treatment, pretreatment with a low dose of MK-8776 (100-400 nmol/L) significantly increased irradiation-induced γH2A.X foci in the 3 TNBC cell lines, suggesting enhanced DNA damage by MK-8776, inhibited the cell proliferation and increased the radiosensitivity of the 3 TNBC cell lines. Similar results were obtained in MDA-MB-231 xenograft tumors in nude mice that received MK-8776 (15 or 40 mg/kg, ip) 26 d after irradiation. To explore the mechanisms underlying the radio-sensitization by MK-8776, we used TEM and found that irradiation significantly increased the numbers of autophagosomes in the 3 TNBC cell lines. Moreover, irradiation markedly elevated the levels of Atg5, and promoted the transformation of LC3-I to LC3-II in the cells. Pretreatment with the low dose of MK-8776 suppressed these effects. The above results suggest that MK-8776 increases human TNBC radiosensitivity by inhibiting irradiation-induced autophagy and that MK-8776 may be a potential agent in the radiosensitization of human TNBC.
authors.affiliation: Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Shanghai 200032, China.|Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China.
authors.forename: Zhi-Rui
authors.initials: ZR
authors.lastname: Zhou
authors.affiliation: Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Shanghai 200032, China.|Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China.
authors.forename: Zhao-Zhi
authors.initials: ZZ
authors.lastname: Yang
authors.affiliation: Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China.|Cancer Institute and Department of Gynaecological Oncology, Fudan University Shanghai Cancer Center, Shanghai 200032, China.
authors.forename: Shao-Jia
authors.initials: SJ
authors.lastname: Wang
authors.affiliation: Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Shanghai 200032, China.|Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China.
authors.forename: Li
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Shanghai 200032, China.|Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China.
authors.forename: Ju-Rui
authors.initials: JR
authors.lastname: Luo
authors.affiliation: Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Shanghai 200032, China.|Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Feng
authors.affiliation: Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Shanghai 200032, China.|Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China.
authors.forename: Xiao-Li
authors.initials: XL
authors.lastname: Yu
authors.affiliation: Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Shanghai 200032, China.|Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China.
authors.forename: Xing-Xing
authors.initials: XX
authors.lastname: Chen
authors.affiliation: Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Shanghai 200032, China.|Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China.
authors.forename: Xiao-Mao
authors.initials: XM
authors.lastname: Guo
mesh_terms: D000818:Animals; D001343:Autophagy / Q000187:drug effects*; D045744:Cell Line, Tumor; D000071877:Checkpoint Kinase 1 / Q000037:antagonists & inhibitors*; D004249:DNA Damage; D005260:Female; D006801:Humans; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D047428:Protein Kinase Inhibitors / Q000494:pharmacology* / Q000627:therapeutic use; D011720:Pyrazoles / Q000494:pharmacology* / Q000627:therapeutic use; D011743:Pyrimidines / Q000494:pharmacology* / Q000627:therapeutic use; D011836:Radiation Tolerance; D011839:Radiation, Ionizing; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology* / Q000627:therapeutic use; D064726:Triple Negative Breast Neoplasms / Q000473:pathology / Q000532:radiotherapy*
chemical_list: C559815:MK-8776; D047428:Protein Kinase Inhibitors; D011720:Pyrazoles; D011743:Pyrimidines; D011838:Radiation-Sensitizing Agents; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1