Nucleotide excision repair gene subunit XPD is highly expressed in cervical squamous cell carcinoma

One of the subunits in the mammalian transcription factor II H complex, XPD (TFIIH p80), plays a significant role in the nucleotide excision repair pathway. Events such as abnormal DNA excision repair may be involved in the cervical carcinogenesis process. Expression of the human XPD protein was examined using immunohistochemistry in 84 normal cervical tissues and 148 cervical squamous cell carcinoma samples. Additionally, qRT-PCR was performed to analyse the XPD mRNA expression in 69 fresh normal cervical tissues and 110 cervical carcinoma samples. The relationships between XPD expression and various clinicopathological features (including age, FIGO stage, tumor size, stroma involvement, lymph node metastasis and histologic grade) were assessed. The XPD (TFIIH p80) protein was detected primarily in the cytoplasm. We found a statistically significant difference in XPD expression level in cervical carcinoma versus normal cervical tissue (Z = -7.302, P = 0.000). Notably, XPD mRNA was significantly over-expressed in cervical carcinoma tissues but not in normal cervix tissues (t = 6.942, P = 0.000). However, no statistically significant relationship was found regarding XPD expression and age, FIGO stage, tumor size, stroma involvement, lymph node metastasis or histologic grade (P = 0.089, 0.953, 0.809, 0.275, 0.421, 0.387 respectively). Our results showed that XPD was highly expressed in cervical squamous cell carcinoma tissues. A poorly understood change may occur during the XPD transcription process, resulting in the abnormal enrichment seen from mRNA to the protein level, thus leaving the protein unable to perform the normal function of excision repair. There is a need for further research in order to elucidate the specific mechanism involved.