The hypoxic tumor microenvironment in vivo selects tumor cells with increased survival against genotoxic stresses. (1st September 2018)

• Record Type: Journal Article
• Authors: Kim, Hoon; Lin, Qun; Yun, Zhong
• Is Part Of: Cancer letters. Volume 431(2018)
• Page Start: 142
• Page End: 149
• Publication Date: 2018-09-01
• Subjects: Checkpoint kinases -- DNA damage response -- Hypoxia -- Tumor microenvironment -- Xenograft; Cancer -- Periodicals; Neoplasms -- Periodicals; Cancer -- Périodiques; Electronic journals; 616.994
• DOI: 10.1016/j.canlet.2018.05.047
• Languages: English
• ISSNs: 0304-3835

Abstract

Abstract: Tumor sensitivity to radiation therapy has been known to be dependent on O2 concentrations. However, radiosensitivity of naturally occurring hypoxic tumor cells remains to be well fully investigated in direct comparison to that of their adjacent non-hypoxic tumor cells within the same tumor. We developed a hypoxia-sensing xenograft model using the hypoxia-response element (HRE)-driven enhanced green fluorescence protein (EGFP) as a hypoxia reporter to identify hypoxic tumor cells in situ. Here, we have found that naturally hypoxic tumor cells are moderately radioresistant compared to their neighboring non-hypoxic tumor cells in the same tumor. These naturally hypoxic tumor cells are proficient at repairing DNA damages and resist apoptosis induced by genotoxic stresses, which involves activation of the ATM/CHK1/CHK2 DNA damage-sensing pathway. Inhibition of the checkpoint kinases sensitizes the ex vivo hypoxic tumor cells to ionizing irradiation. Second, the new functional phenotypes acquired by the hypoxic tumor cells in vivo are stable even after they are maintained under non-hypoxic conditions. These new results strongly suggest that the hypoxic tumor microenvironment is capable of selecting stable tumor cell populations with increased resistance to genotoxic stresses and enhanced survival. Highlights: Radiosensitivity of naturally hypoxic tumor cells remains to be fully understood. We developed a hypoxia-sensing tumor model to identify hypoxic tumor cells in situ. Tumor hypoxia in vivo selects a stable population of radioresistant tumor cells. ATM/CHK1/CHK2 DNA damage-sensing pathway is preferentially activated in hypoxic cells.