Clock and ATF4 transcription system regulates drug resistance in human cancer cell lines.

The mechanisms underlying cellular drug resistance have been extensively studied, but little is known about its regulation. We have previously reported that activating transcription factor 4 (ATF4) is upregulated in cisplatin-resistant cells and plays a role in cisplatin resistance. Here, we find out a novel relationship between the circadian transcription factor Clock and drug resistance. Clock drives the periodical expression of many genes that regulate hormone release, cell division, sleep-awake cycle and tumor growth. We demonstrate that ATF4 is a direct target of Clock, and that Clock is overexpressed in cisplatin-resistant cells. Furthermore, Clock expression significantly correlates with cisplatin sensitivity, and that the downregulation of either Clock or ATF4 confers sensitivity of A549 cells to cisplatin and etoposide. Notably, ATF4-overexpressing cells show multidrug resistance and marked elevation of intracellular glutathione. The microarray study reveals that genes for glutathione metabolism are generally downregulated by the knockdown of ATF4 expression. These results suggest that the Clock and ATF4 transcription system might play an important role in multidrug resistance through glutathione-dependent redox system, and also indicate that physiological potentials of Clock-controlled redox system might be important to better understand the oxidative stress-associated disorders including cancer and systemic chronotherapy.

Mutations within the tyrosine kinase domain of EGFR gene specifically occur in lung adenocarcinoma patients with a low exposure of tobacco smoking.

Somatically acquired mutations in the epidermal growth factor receptor (EGFR) gene in lung cancer are associated with significant clinical responses to gefitinib, a tyrosine kinase inhibitor that targets EGFR. We screened the EGFR in 469 resected tumours of patients with lung cancer, which included 322 adenocarcinomas, 102 squamous cell carcinomas, 27 large cell carcinomas, 13 small cell carcinomas, and five other cell types. PCR with a specific condition was performed to identify any deletion in exon 19, while mutant-allele-specific amplification was performed to identify a mutation in codon 858 of exon 21. EGFR mutations were found in 136 cases (42.2%) with adenocarcinoma, in one case with large cell carcinoma, and in one case with pleomorphic carcinoma. An in-frame deletion in exon 19 was found in 62 cases while an L858R mutation was found in 77 cases. In the 322 cases with adenocarcinoma, these mutations were more frequently found in women than in men (P=0.0004), in well differentiated tumours than in poorly differentiated tumours (P=0.0014), and in patients who were never smokers than in patients who were current/former smokers (P<0.0001). The mutation was more frequently observed in patients who smoked

Simultaneous dietary supplementation of sodium cholate and beta-carotene markedly enhances accumulation of beta-carotene in mice.

This study evaluated whether simultaneous supplementation of sodium cholate and beta-carotene to a diet enhanced the accumulation of beta-carotene in mice. For 2 wk, male ICR mice were fed either a basal diet or a diet containing Dunaliella-bardawil beta-carotene 50 mg/100g that was or was not supplemented with sodium cholate (0.25 g/100 g). The concentrations of beta-carotene in liver and plasma were approximately 5 and 10 times higher, respectively. In the mice fed the beta-carotene diet with sodium cholate than in those fed the beta-carotene diet without sodium cholate. Beta-carotene was not detectable in the liver or plasma of mice fed either basal diet. The concentrations of vitamin E in the plasma and liver of mice fed either beta-carotene diet or the basal diet with sodium cholate were significantly lower than in those fed the basal diet. In a second study, mice were fed a diet containing 50 mg/100 g synthetic beta-carotene supplemented with various concentrations of sodium cholate (0, 0.05, 0.1, 0.25, 0.5 g/100 g) for 2 wk. The concentrations of beta-carotene and vitamin E in plasma, liver and bone marrow cells were higher in mice fed the beta-carotene diet supplemented with 0.05 g/100 g of sodium cholate than in those fed the unsupplemented diet. These findings show that simultaneous supplementation of sodium cholate and beta-carotene to a diet markedly enhances the accumulation of beta-carotene. This dietary protocol may be useful to introduce a high amount of beta-carotene in the tissue of mice in a short period of time.