DNA polymerase ζ as a potential biomarker of chemoradiation resistance and poor prognosis for cervical cancer

DNA Polymerase ζ (Polζ), an error-prone DNA polymerase involved in translesion DNA synthesis, plays a significant role in the cytotoxicity, mutagenicity, and chemoresistance of several cancers. To evaluate the association of Polζ with chemoradiation resistance and prognosis in cervical cancer, we enrolled 123 patients with squamous cell carcinoma of cervical cancer, who had adjuvant concurrent chemoradiation therapy after radical surgery treated at Fudan University Shanghai Cancer Center between 2008 and 2009, and tested their in vitro tumor inhibition rates using the 3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-di-phenytetrazoliumromide method and Polζ protein expression in paraffin-embedded tissues using immunohistochemistry. We found that the Polζ-positive expression was detected in 22 % of the cases. The median in vitro inhibition rate of tumor cell growth by cisplatin, carboplatin, nedaplatin, and oxaliplatin was 80, 37, 78, and 51 %, respectively. Among the tumor-related variables, FIGO stage, tumor grade, and Polζ protein expression (adjusted HR 6.7, 4.2 and 6.7; 95 % CI 1.7–26.3, 1.0–17.3 and 1.8–25.4; P = 0.007, 0.046 and 0.005, respectively) were found to be significant predictors for recurrence. Kaplan–Meier survival estimates showed that the patients with more advanced stage (IIB) or Polζ-positive expression had a significantly shorter progression-free survival. Polζ-positive expression was significantly associated with depth of cervical stromal invasion (P = 0.012). However, the association between Polζ expression and in vitro tumor inhibition rates was not significant. Taken together, Polζ expression can be used as the predictor for poor prognosis, which might be caused by the potential chemoradiation resistance of the cervical cancer patients. The mechanism deserves further exploration.