Evaluation of CHK1 activation in vulvar squamous cell carcinoma and its potential as a therapeutic target in vitro

摘要

CHK1 is an important regulator of the cell cycle and DNA damage response, and its altered expression has been identified in various tumors. Chk1 inhibitors are currently being evaluated as monotherapy and as potentiators of chemotherapy in clinical settings. However, to our knowledge, no previous study has investigated either the activation status or the therapeutic potential of CHK1 targeting in vulvar cancer. Therefore, we examined the expression status of activated CHK1 forms pCHK1^Ser345, pCHK1^Ser317, pCHK1^Ser296, and pCHK1^Ser280 in 294 vulvar squamous cell carcinomas (VSCC) using immunohistochemistry and analyzed their relationships with various clinicopathological variables and clinical outcome. To aid translation of preclinical studies, we also assessed cell sensitivity to the Chk1 inhibition in two vulvar cancer cell lines. Compared to the levels of pCHK1^Ser345, pCHK1^Ser317, pCHK1^Ser296, and pCHK1^Ser280 in normal vulvar squamous epithelium, high nuclear pCHK1^Ser345 expression was found in 57% of vulvar carcinomas, whereas low nuclear pCHK1^Ser317, pCHK1^Ser296, and style="fixed-case">pCHK1^Ser280 expressions were observed in 58%, 64%, and 40% of the cases, respectively. Low levels of style="fixed-case">pCHK1^Ser317 and style="fixed-case">pCHK1^Ser280 in the nucleus correlated significantly with advanced tumor behaviors and aggressive features. None of style="fixed-case">pCHK1^Ser345, style="fixed-case">pCHK1^Ser317, style="fixed-case">pCHK1^Ser296, and style="fixed-case">pCHK1^Ser280 forms were identified as prognostic factors. In vitro inhibition of style="fixed-case">CHK1 by small molecular inhibitors or si style="fixed-case">RNA reduced viability by inducing style="fixed-case">DNA damage and apoptosis of vulvar cancer cell lines. In summary, we conclude that cellular functions regulated by style="fixed-case">CHK1 are phosphorylation/localization‐dependent and deregulation of style="fixed-case">CHK1 function occurs in style="fixed-case">VSCC and might contribute to tumorigenesis. Targeting style="fixed-case">CHK1 might represent as a useful antitumor strategy for the subgroup of VSCC harboring p53 mutations.