Expression Of APE1 And Chemotherapy Related Biomarkers In Advanced Non-small-cell Lung Cancer And Its Clinical Significance

BackgroundLung cancer is one of the most common malignant tumor in the world, and is the leading cause of died in the cancer population. 80% of lung cancer cases is non-small cell lung cancer(NSCLC), more than 70% of NSCLC are at the advanced-stages at the time of diagnosis(such as: stage IIIB for locally advanced and stage IV for metastatic disease), the proportion of patients usually with poor prognosis. Currently, platinum-based doublet chemotherapy is the criterion for clinical advanced NSCLC chemotherapy regimens.These combination regimens are preferred for patients with good performance status and only 30–40% patients have shown responses and the overall 5-year survival rate is still below 15%. Thus, a tailored chemotherapy based on potential predictive or prognostic markers is an urgent need.Resistance to platinum drug is not only a major obstacle to treatment, but also related to the poor prognosis in patients with NSCLC. DNA repair gene activities can impact treatment response to platinum and previous studies showed that patients with lower DNA repair capacity(DRC) were more chemosensitive than those who carries a proficient DNA repair activity. The human apurinic/apyrimidinic endonuclease 1(APE1) is a major enzyme in base excision repair(BER) pathways, which plays an important role in DNA repair and oxidation reduction. Several studies have demonstrated that APE1 was overexpressed in human cancers and increased APE1 expression is associated with poor prognosis, but the relationship between APE1 expression and first-line platinum-based chemotherapy in advanced NCSLC has yet not been reported. ERCC1(excision repair cross complementing 1) and BRCA1(breast cancer susceptibility gene 1) are components of the nucleotide excision repair(NER) pathway, they may be potential predictive and prognostic markers for NSCLC. However, previous retrospective and prospective studies demonstrated that ERCC1 and/or BRCA1 expression was not always consistent to predict sensitivity of NSCLC to platinum treatment. Different experiments tell us, platinum plays an irreplaceable role in treatment of NSCLS, and we need novel and more predictive platinum sensitivity markers to achieve better efficacy of the individualized chemotherapy treatment of advanced NSCLS.Paclitaxel, not only alone or combined with cisplatin or carboplatin, are widely used in the treatment of NSCLC. Several studies have shown that an increased TUBB3 expression predicts a poor prognosis in advanced NSCLC patients treated with paclitaxel-based treatment. BRCA1 was a predictive marker for platinum and anti-microtubulin agents and low levels of BRCA1 expression had a better cisplatin sensitivity but still resistance to paclitaxel.It is widely accepted that administration of effective drugs selected according to their predicted chemosensitivity could significantly improve the survival and/or quality of life of NSCLC patients. Therefore, in this study, we immunohistochemically analyzed the expression of APE1, BRCA1, ERCC1 and TUBB3 proteins in advanced NSCLC treatmented with platinum-based chemotherapy for association with treatment response, and progression-free and overall survival time.Study objectiveThis study was to explore APE1, BRCA1, ERCC1 and TUBB3 expression for advanced NSCLC treated with first-line platinum-based chemotherapy for association with chemotherapy effect and survival, and investigate the effect of APE1 on cisplatin, paclitaxel and gemcitabine sensitivity to lung adenocarcinoma A549 cells.Materials and methods1.The relationship between APE1, BRCA1, ERCC1 and TUBB3 expression and prognosis of advanced NSCLC treated with first-line platinum-based chemotherapy APE1, BRCA1, ERCC1 and TUBB3 expression and advanced NSCLC prognosis treated with first-line platinum-based chemotherapyAdvance NSCLC patients and their medical records were collected, then we immunohistochemically analyzed expression of APE1, BRCA1, ERCC1 and TUBB3 proteins in tissue samples from advanced NSCLC patients treated with platinum-based chemotherapy for association with treatment responses and progression-free and overall survival.2.The effect of APE1 on cisplatin, paclitaxel and gemcitabine sensitivity to lung adenocarcinoma A549 cells.Cells were transferred by APE1-siRNA and scramble-siRNA, then treated with different dose of cisplatin, paclitaxel and gemcitabine. The expression of APE1 protein was detected by westernblot analysis. Use MTT method to detect the survival rates of cell, and cell apoptosis was determined by AnnexinV/PI.Results1.The data showed that the response rate, PFS and OS were significantly better in NSCLC patients with low ERCC1 expression than those with high expression levels(p<0.05). Patients with APE1-negative tumors had a better response to chemotherapy(P=0.002), better median PFS(P=0.016), but not OS(P=0.263). In addition, the APE1 and ERCC1 both negative tumor patients had significantly higher response rate, better median PFS and OS than those with both positive tumors(P<0.01).2.Stratified analysis:136 patients with advanced NSCLC, who were treated with 1st-line platinum-paclitaxel chemotherapy,patients with negative expression of APE1, ERCC1 or TUBB3 benefited from platinum-paclitaxel chemotherapy regimen. Patients with ERCC1 negative tumor had longer median PFS(P=0.016) and median OS(P=0.030) compared with the positive patients. Similarly, the APE1-negative patients showed longer median PFS(P=0.004) but not OS. Multivariate analysis showed that APE1 and ERCC1 was an independent predictor of PFS(P=0.016) and OS(P=0.040). In addition, patients with APE1 and ERCC1 both negative or APE1 and TUBB3 both negative tumors had obviously higher response rate, longer median PFS and OS with platinum and paclitaxel chemotherapy(P<0.05).3.Knockdown of APE1 expression significantly increased lung adenocarcinoma A549 cells response to cisplatin and paclitaxel.Conclusion1.APE1 can be a noval predictor for advanced NSCLC patients treated with first-line platinum-based or platinum plus paclitaxel chemotherapy, and it is an independent prognostic indicator;2.ERCC1 can predict chemotherapy effect and prognosis in advanced NSCLC patients treated with first-line platinum-based or platinum plus paclitaxel chemotherapy; TUBB3 can predict chemotherapy effect in advanced NSCLC patients treated with first-line platinum plus paclitaxel chemotherapy;3.NSCLC patients with both APE1- and ERCC1-negative tumors had significantly higher response rate, better median PFS and OS than those with both positive tumors;4. Cell experiments further confirmed that knockdown of APE1 expression significantly increased lung adenocarcinoma A549 cells response to cisplatin and paclitaxel.