Cellular effects of genotoxic stress and gene silencing of the checkpoint kinases in human oral cells.

ABSTRACT

BACKGROUND: The human oral cells have different physiological properties and different origins in developmental stages. Mechanical, physiological, and chemical stress can cause damage and irritation during clinical treatment in various oral tissues. PURPOSE: The effects of DNA damage response and gene silencing of checkpoint kinases (Chk1/2) is not unclear in oral primary and cancer cells. METHOD: Treatment with doxorubicin involving DNA damage and gene silencing of Chk1/2 by shRNA constructs was performed in pulp, periodontal ligament, gingival tissues (HGF), and mouth epithelial carcinoma cells (KB). RESULTS: The KB cells were more sensitive to genotoxic stress response than oral primary cells. Endogenous levels of Chk1/2 in KB cell were higher than in pulp cells. When doxorubicin was administered, Chk2 activation was induced in KB cell, but not in pulp cells. However, viability in KB cells did not decrease by the suppression of the checkpoint proteins, whereas primary cells were defective in gene silencing. When doxorubicin treatment and gene silencing were combined, both primary cells and KB cell were defective. Moreover, in case of KB cell, cell death was increased and activation of Chk2 was increased in doxorubicin dose-dependent. CONCLUSION: These data indicate that not only stress response mechanism may be different in oral primary and cancer cells but also Chk1/2 proteins may have essential roles in oral primary cells. Based on these data, checkpoint proteins may be crucial drug targets for oral cancer therapy.