Messenger RNA and protein expression of thymidylate synthase and DNA repair genes in thymic tumors

Pronounced between-subject and circadian variability in thymidylate synthase and dihydropyrimidine dehydrogenase enzyme activity in human volunteers

AIMS

The enzymatic activity of dihydropyrimidine dehydrogenase (DPD) and thymidylate synthase (TS) are important for the tolerability and efficacy of the fluoropyrimidine drugs. In the present study, we explored between-subject variability (BSV) and circadian rhythmicity in DPD and TS activity in human volunteers.

METHODS

The BSVs in DPD activity (n = 20) in peripheral blood mononuclear cells (PBMCs) and in plasma, measured by means of the dihydrouracil (DHU) and uracil (U) plasma levels and DHU : U ratio (n = 40), and TS activity in PBMCs (n = 19), were examined. Samples were collected every 4 h throughout 1 day for assessment of circadian rhythmicity in DPD and TS activity in PBMCs (n = 12) and DHU : U plasma ratios (n = 23). In addition, the effects of genetic polymorphisms and gene expression on DPD and TS activity were explored.

RESULTS

Population mean (± standard deviation) DPD activity in PBMCs and DHU : U plasma ratio were 9.2 (±2.1) nmol mg(-1) h(-1) and 10.6 (±2.4), respectively. Individual TS activity in PBMCs ranged from 0.024 nmol mg(-1) h(-1) to 0.596 nmol mg(-1) h(-1) . Circadian rhythmicity was demonstrated for all phenotype markers. Between 00:30 h and 02:00 h, DPD activity in PBMCs peaked, while the DHU : U plasma ratio and TS activity in PBMCs showed trough activity. Peak-to-trough ratios for DPD and TS activity in PBMCs were 1.69 and 1.62, respectively. For the DHU : U plasma ratio, the peak-to-trough ratio was 1.43.

CONCLUSIONS

BSV and circadian variability in DPD and TS activity were demonstrated. Circadian rhythmicity in DPD might be tissue dependent. The results suggested an influence of circadian rhythms on phenotype-guided fluoropyrimidine dosing and supported implications for chronotherapy with high-dose fluoropyrimidine administration during the night.

Correlation between S-1 treatment outcome and expression of biomarkers for refractory thymic carcinoma

BACKGROUND

Thymic carcinoma is a rare cancer with minimal evidence of a survival benefit following chemotherapy. An oral fluoropyrimidine of S-1, however, is the recommended active cytotoxic chemotherapy agent for refractory thymic carcinoma based on a case series, whereas sunitinib or everolimus are recommended as molecular-targeted agents based on Phase II trials. We retrospectively investigated the efficacy of S-1 for refractory thymic carcinoma and performed a biomarker analysis.

METHODS

We assessed the clinicopathological variables of 14 consecutive patients who underwent S-1 for refractory thymic carcinoma and correlated the clinical outcomes with potential biomarkers using paraffin-embedded cancer tissues of eight patients in the cohort.

RESULTS

A total of 178 thymic malignancies were identified, of whom 14 patients included 12 cases of squamous cell carcinoma, one lymphoepithelioma-like carcinoma, and one undifferentiated carcinoma. Six patients exhibited a partial response (42.9 %: 95 % confidence interval [CI], 21.4-67.4) and the disease control rate was 85.7 % (60.0-96.0 %). After a median follow-up of 24.2 months, the median progression-free survival was 8.1 months (range, 2.6-12.2 months), and median overall survival was 30.0 months (range, 6.2-41.9 months). No significant correlation between biomarker expression and response was noted. However, thymidine synthase (TS)/dihydropyrimidine dehydrogenase and TS/orotate phosphoribosyltransferase were observed.

CONCLUSIONS

S-1 for refractory thymic carcinoma offered clinical activity and achieved an 85 % disease control rate. Although the biomarkers did not correlate with clinical outcome, the study results showed efficacy of S-1 as a cytotoxic chemotherapy for refractory thymic carcinoma, which warrants future investigation.

Key components of chemotherapy for thymic malignancies: a systematic review and pooled analysis for anthracycline-, carboplatin- or cisplatin-based chemotherapy

Purpose

Thymic malignancies, comprising thymoma and thymic carcinoma, are rare. Consequently, optimal chemotherapy for advanced thymic malignancies remains controversial. Platinum-based chemotherapy is currently the consensus treatment based on the results of single-arm phase II trials and retrospective investigations. However, comparison of cisplatin-based and carboplatin-based chemotherapy has yet to be undertaken; the effectiveness of the addition of anthracycline also remains uncertain.

Methods

In the present study, clinical trials and retrospective data regarding platinum-based chemotherapy were analyzed. The endpoint was the response rate to each chemotherapy. For advanced thymoma, we compared platinum with anthracycline-based chemotherapy and platinum with non-anthracycline-based chemotherapy. For advanced thymic carcinoma, anthracycline-based versus non-anthracycline-based chemotherapy and carboplatin-based versus cisplatin-based chemotherapy were compared. This analysis included a retrospective study of response of advanced thymic carcinoma to irinotecan and cisplatin in our institution.

Results

The response rate for the 314 patients from 15 studies with advanced thymoma, including both prospective and retrospective data, was 69.4 % [95 % confidence interval (CI) 63.1–75.0 %] for platinum with anthracycline-based chemotherapy and 37.8 % (95 % CI 28.1–48.6 %; p < 0.0001) for platinum with non-anthracycline-based chemotherapy. The response rates after anthracycline-based and non-anthracycline-based chemotherapy for advanced thymic carcinoma were similar (41.8 vs. 40.9 %; p < 0.91), whereas the response rates after cisplatin-based and carboplatin-based chemotherapy for advanced thymic carcinoma differed significantly (53.6 vs. 32.8 %; p = 0.0029) in 206 patients from 10 studies.

Conclusions

Platinum with anthracycline-based chemotherapy is an optimal combination for advanced thymoma. For advanced thymic carcinoma, cisplatin-based chemotherapy may be superior to carboplatin-based chemotherapy.