Impact of thymidylate synthase protein expression on efficacy of chemotherapy in advanced lung cancer patients

Cyclin E overexpression confers resistance to the CDK4/6 specific inhibitor palbociclib in gastric cancer cells

Palbociclib is a specific inhibitor of CDK4/6 and has been shown to provide a survival benefit in hormone receptor-positive advanced breast cancer. TCGA database reported that about half of gastric cancers exhibit abnormalities in cell-cycle-related molecules, suggesting that gastric cancer is a good candidate for palbociclib treatment; however, the antitumor effects and predictive markers of palbociclib in gastric cancer remain incompletely described. Herein, the effect and predictive markers of palbociclib on gastric cancer cells were investigated. Our results reveal that palbociclib showed anti-proliferative effects by inducing G1 phase cell-cycle arrest and cellular senescence in some gastric cancer cells. Basal protein expression level of cyclin E showed an inverse correlation of cancer cell sensitivity to palbociclib. In addition, palbociclib enhanced the antitumor effect of 5-FU in vitro and in vivo by modulating thymidine synthase expression. These results suggest that cyclin E protein expression determines the anti-proliferative effect of palbociclib, and palbociclib acts synergistically with 5-FU in gastric cancer. These findings provide a rationale for future clinical trials of palbociclib and 5-FU combination-based chemotherapy in gastric cancer.

Thymidylate synthase gene amplification predicts pemetrexed resistance in patients with advanced non-small cell lung cancer

BACKGROUND

Thymidylate synthase (TYMS) expression in lung cancer tissue affects the therapeutic efficacy of pemetrexed (PMT). TYMS protein expression is primarily assessed using immunohistochemistry (IHC), but this method is not suitable for accurate quantitative analysis. It is not known whether the analysis of TYMS gene copy number using fluorescence in situ hybridization (FISH) is a useful method for assessment of TYMS expression.

PATIENTS AND METHODS

The participants were patients with chemo-naïve advanced NSCLC treated with PMT plus carboplatin (CBDCA) in prospective clinical phase II study. TYMS expression was evaluated in 40 patients by gene copy number and protein expression using FISH and IHC. Therapeutic efficacy was evaluated by investigating the response rate (RR), disease control rate (DCR), progression-free survival (PFS), and overall survival (OS).

RESULTS

TYMS gene amplification was detected in 8 patients (32 %) among 25 patients who could be evaluated for TYMS gene copy number. There were no patients with complete or partial response in the TYMS amplified group. RR and DCR were lower in the TYMS amplified group compared with the TYMS unamplified group (0 versus 35.3 %, p = 0.0539, 62.5 versus 94.1 %, p = 0.0443). PFS and OS were reduced in the TYMS amplified group. The analysis of TYMS gene copy number had higher sensitivity and specificity compared with TYMS protein expression (76.2 versus 50.0 %, 75.0 versus 66.7 %).

CONCLUSION

The analysis of TYMS gene copy number is more suitable than TYMS protein expression for assessment of TYMS expression. TYMS gene amplification predicts outcome of patients receiving PMT with advanced NSCLC.

Prognostic significance of thymidylate synthase in postoperative non-small cell lung cancer patients

The aim of the present study was to investigate the clinicopathologic/prognostic significance of thymidylate synthase (TS), orotate phosphoribosyltransferase (OPRT), and thymidine phosphorylase (TP) proteins in postoperative non-small cell lung cancer (NSCLC) patients. Microarray slides from a set of 178 NSCLC patients were used for the detection of TS, OPRT, and TP expression by immunohistochemistry. The correlation between clinicopathologic factors and protein expression of three proteins was analyzed. Ninety seven carcinomas (57.4%) were TS-positive, 90 carcinomas (53.9%) were OPRT-positive, and 102 carcinomas (69.4%) were TP-positive. Compared with the TS-positive patients, the overall survival (OS) was significantly lower in the TS-negative patients (hazard ratio [HR] =1.766, 95% confidence interval [CI] =1.212–2.573, P=0.003). Significant differences between TS-positive and TS-negative patients was also observed in the following stratified analyses: 1) adenocarcinoma subgroup (HR =2.079, 95% CI =1.235–3.500, P=0.006); 2) less than 60-year-old subgroup (HR =1.890, 95% CI =1.061–3.366, P=0.031); 3) stage II/III subgroup (HR =1.594, 95% CI =1.036–2.453, P=0.034); and 4) surgery plus adjuvant therapy subgroup (HR =1.976, 95% CI =1.226–3.185, P=0.005). However, the OS was not significantly correlated with OPRT or TP protein expression. This study demonstrates that the TS level in tumor tissues may be a useful marker to predict the postoperative OS in NSCLC patients.