Mitochondrial DNA determines androgen dependence in prostate cancer cell lines

Prostate cancer progresses from an androgen-dependent to androgen-independent stage after androgen ablation therapy. Mitochondrial DNA plays a role in cell death and metastatic competence. Further, heteroplasmic large-deletion mitochondrial DNA is very common in prostate cancer. To investigate the role of mitochondrial DNA in androgen dependence of prostate cancers, we tested the changes of normal and deleted mitochondrial DNA in accordance with the progression of prostate cancer. We demonstrated that the androgen-independent cell line C4-2, established by inoculation of the androgen-dependent LNCaP cell line into castrated mice, has a greatly reduced amount of normal mitochondrial DNA and an accumulation of large-deletion DNA. Strikingly, the depletion of mitochondrial DNA from androgen-dependent LNCaP resulted in a loss of androgen dependence. Reconstitution of normal mitochondrial DNA to the mitochondrial DNA-depleted clone restored androgen dependence. These results indicate that mitochondrial DNA determines androgen dependence of prostate cancer cell lines. Further, mitochondrial DNA-deficient cells formed tumors in castrated athymic mice, whereas LNCaP did not. The accumulation of large deletion and depletion of mitochondrial DNA may thus play a role in the development of androgen independence, leading to progression of prostate cancers.

Anoxic depolarization of rat hippocampal slices is prevented by thiopental but not by propofol or isoflurane

BACKGROUND

There is strong evidence to suggest that anoxic depolarization (AD) is an important factor in hypoxia/ischaemia-induced neural damage. Treatments that prevent the occurrence of AD may be useful in providing neuronal protection against hypoxia. The current study was designed to determine whether general anaesthetics which have been suggested to 'induce prophylaxis' against hypoxia can attenuate the incidence of AD.

METHODS

The effects of anoxia (3 min) on evoked extracellularly recorded field potentials of CA1 neurons in rat hippocampal slices were assessed in the absence and presence of the i.v. general anaesthetics thiopental and propofol and the volatile anaesthetic isoflurane.

RESULTS

In the absence of anaesthetics, AD occurred in 81% of the preparations tested. Thiopental (2 x 10(-4) M) significantly reduced the incidence of AD (16%, P=0.0006). In comparison, propofol (2 x 10(-4) M) and isoflurane (1.5 vol%) were ineffective (69% and 60%, respectively). Furthermore, in the presence of thiopental, the population spike amplitude recovered with and without AD (90% and 94% of pre-anoxic value, respectively) following 3 min anoxia.

CONCLUSION

The prophylactic effect of thiopental against hypoxia might be induced, in part, by preventing the generation of AD.

Overview of mammalian zinc transporters

In recent years, a number of mammalian zinc transporters have been identified, and candidate genes are rapidly growing. These transporters are classified into two families: ZIP (ZRT, IRT-like protein) and CDF (cation diffusion facilitator). ZIP members facilitate zinc influx into the cytosol, while CDF members facilitate its efflux from the cytosol. Molecular characterization of the transporters has brought about major advances in our understanding of their physiological functions. Zinc metabolism is regulated primarily through zinc-dependent control of transcription, translation, and intracellular trafficking of transporters. Analyses of mice whose zinc transporter genes have been genetically disrupted and of the naturally occurring mutant mice with symptoms related to abnormal zinc metabolism have provided compelling evidence that some zinc transporters play critical roles in zinc homeostasis. In this review, we review the literature of mammalian zinc transporters with emphasis on very recent findings and elicit integrative knowledge of zinc homeostasis.

Case of radiation-induced esophageal ulcer worsened after endoscopic biopsy

Esophageal ulcer is one of the most important late complications of the esophagus treated with radiation therapy, especially with intraluminal brachytherapy. We encountered a patient with esophageal cancer treated with external radiation therapy and intraluminal brachytherapy, who developed radiation ulcer and who had severe dysphagia soon after endoscopic biopsy of the ulcer edge. A 55-year-old man was diagnosed as esophageal cancer without symptoms. He received 60 Gy/30 Fr of external radiation therapy and 12 Gy/3 Fr of intraluminal brachytherapy at a point of 5 mm in depth from the mucosa surface. He developed an asymptomatic esophageal ulcer 13 months after treatment, and endoscopic biopsy was obtained from the edge of the ulcer. Thereafter, swallowing difficulties appeared, and endoscopy revealed severe esophageal stenosis and a deep ulcer. A possibility that the biopsy contributed to worsening the ulcer can be considered. Except for cases where relapse is apparent, endoscopic biopsy is considered to be avoided.