Christopher J. Dougherty

Selective apoptosis of breast cancer cells by siRNA targeting of BORIS

Brother of the regulator of imprinted sites (BORIS) is an epigenetically acting transcription factor which represses the tumor inhibitor functions of the tumor suppressor protein CTCF. BORIS expression has not been documented in adult females, making it an exciting molecular target for drug development in breast cancer. Previously, we demonstrated that vaccination of mice with zing-finger (ZF)-deleted non-functional BORIS results in regression of breast cancer and generation of potent anti-tumor immune responses. RNAi induction can be used as an alternative approach for selective tumor cell killing. Short interfering RNA (siRNA) molecules targeting BORIS were generated and their efficacy was tested in MDA-MB-231 breast cancer and non-malignant epithelial cell lines. Treatment with BORIS-specific siRNA, but not control siRNA led to a concentration-dependent reduction in BORIS expression and proportional apoptotic death of the cancer but not control cells. To our knowledge this is first report demonstrating a critical role of BORIS in maintaining tumor cell viability.

Selective Degeneration of Central Photoreceptors after Hyperbaric Oxygen in Normal and Metallothionein-Knockout Mice

PURPOSE Metallothioneins (MTs) in the brain and retina are believed to bind metals and reduce free radicals, thereby protecting neurons from oxidative damage. This study was undertaken to investigate whether retinal photoreceptor (PR) cells lacking MTs are more susceptible to hyperbaric oxygen (HBO)-induced cell death in vivo. METHODS Wild-type (WT) and MT-knockout (MT-KO) mice lacking metallothionein (MT)-1 and MT-2 were exposed to three atmospheres of 100% oxygen for 3 hours, 3 times per week for 1, 3, or 5 weeks. The control animals were not exposed. Histologic analysis of PR viability was performed by counting rows of nuclei in the outer nuclear layer (ONL). Ultrastructure studies verified PR damage. RESULTS HBO exposure produced a major loss of PR cells in the central retinas of WT and MT-KO mice, with no effect on the peripheral retina even at the longest (5 weeks) exposures. The degree of PR damage and cell death increased with duration of HBO exposure. One week of HBO exposure was insufficient to cause PR death, but tissue damage was observed in the inner and outer segments. At 3 weeks, the rows of PR nuclei in the central retina were significantly reduced by 38% in WT and 28% in MT-KO animals. At 5 weeks, PR loss was identical in WT (34%) and MT-KO (34%) animals and was comparable to that in WT at 3 weeks. CONCLUSIONS The data suggest that MT-1 and -2 alone are not sufficient for protecting PRs against HBO-induced cell death. The selective degeneration of central PRs may provide clues to mechanisms of oxidative damage in retinal disease.