Yin Yang 1 (YY1): Regulation of Survivin and Its Role In Invasion and Metastasis.

Despite significant clinical and basic science advancements, cancer remains a devastating disease that affects people of all ages, races, and backgrounds. The pathogenesis of cancer has recently been described to result from eight biological capabilities or hallmarks and two enabling characteristics. These eight hallmarks are: deregulation of cellular energetics, avoiding immune destruction, enabling replicative immortality, inducing angiogenesis, sustaining proliferative signaling, evading growth suppressors, resisting cell death, and activating invasion and metastasis. The enabling characteristics are: genome instability and mutation and tumor-promoting inflammation. Survivin, the fourth most common transcript found in cancer cells, is a protein that is thought to be involved in the enhanced proliferation, survival, and metastasis and possibly other key hallmarks of cancer cells. Understanding how this gene is turned on and off is vitally important for attempt improving cancer management and therapy. Our work has identified a novel transcriptional regulator of survivin called Yin Yang 1 (YY1), which has been observed to activate some gene promoters and repress others and is gaining increasing interest as a target of cancer therapy. Our work shows for the first time that YY1 represses survivin transcription by physically interacting with the survivin promoter. Furthermore, YY1 appears to contribute to basal survivin transcriptional activity, indicating that disruption of its binding may in part contribute to survivin overexpression after cellular stress events including chemotherapy and radiotherapy.

Yin Yang 1 regulates the transcriptional repression of Survivin.

The mechanisms for regulation of the Inhibitor of Apoptosis (IAP) Survivin in cells undergoing stress associated with tumor development and the tumor microenvironment are not well understood. The stress response transcription factors HIF-1α and Yin Yang 1 (YY1) were hypothesized to contribute to the upregulation of Survivin in tumor cells. As expected, U2OS cells overexpressing HIF-1α showed a 2- to 3-fold transactivation when transfected. Surprisingly, when YY1 was overexpressed in this survivin promoter reporter system, luciferase expression was repressed 30- to 40-fold. YY1 involvement in survivin promoter repression was confirmed using siRNA directed against YY1. These studies showed that knockdown of YY1 releases the survivin promoter from the observed repression and leads to a 3- to 5-fold increase in promoter activity above basal levels. A U2OS cell line containing a stable YY1 Tet-off system was used to determine whether a temporal increase in YY1 expression affects Survivin protein levels. A low to moderate decrease in Survivin protein was observed 24h and 48h after Tet removal. Studies also confirmed that YY1 is capable of directly binding to the survivin promoter. Collectively, these findings identify novel basal transcriptional requirements of survivin gene expression which are likely to play important roles in the development of cancer and resistance to its treatment.

Diffusion-weighted imaging predicts cognition in pediatric brain injury.

Apparent diffusion coefficient maps from diffusion-weighted imaging predict gross neurologic outcome in adults with traumatic brain injury. Few studies in children have been reported, and none have used apparent diffusion coefficient maps to predict long-term (>1 year) neurocognitive outcomes. In this study, pooled regional and total brain diffusion coefficients were used to predict long-term outcomes in 17 pediatric brain injury patients. Apparent diffusion coefficient values were grouped into peripheral and deep gray and white matter, posterior fossa, and total brain. Regions of interest excluded areas that appeared abnormal on T(2)-weighted images. Apparent diffusion coefficient values from peripheral regions were inversely correlated with cognitive functioning. No significant correlations were apparent between the cognitive scores and apparent diffusion coefficient values for deep tissue or the posterior fossa. Regression analyses suggested that combined peripheral gray and white matter apparent diffusion coefficients explained 42% of the variance in the combined neurocognitive index. Peripheral gray diffusion coefficients alone explained an additional 20% of variance after accounting for clinical variables. These results suggest that obtaining apparent diffusion coefficient values, specifically from peripheral brain regions, may predict long-term outcome after pediatric brain injury. Discrepancies in the literature on this topic, as well as possible explanations, including sampling and clinical considerations, are discussed.

Enhanced antitumor effect of combined gemcitabine and proton radiation in the treatment of pancreatic cancer.

OBJECTIVES: This study evaluates the efficacy of combining proton irradiation with gemcitabine, and the role the inhibitor of apoptosis proteins survivin and X-linked inhibitor of apoptosis protein (XIAP) play in the radiosensitive versus radioresistant status of pancreatic cancer. METHODS: The radioresistant (PANC-1) and radiosensitive (MIA PaCa-2) pancreatic carcinoma cells' response to combined gemcitabine and proton irradiation was compared. Cells were treated with 0.1 to 500 microM gemcitabine and 0- to 15-Gy proton irradiation after which trypan blue and flow cytometry were used to determine changes in the cell cycle and apoptosis. Expression levels of survivin and XIAP were measured using Western blotting. Combination therapy with gemcitabine for 24 hours followed by 10-Gy proton irradiation proved most effective. RESULTS: Gemcitabine and proton irradiation resulted in increased survivin levels with little apoptosis. However, combination therapy resulted in robust apoptotic induction with a concomitant survivin and XIAP reduction in the MIA PaCa-2 cells with little effect in the PANC-1 cells. Small interfering RNA studies confirmed a role for XIAP in the radioresistance of PANC-1 cells. CONCLUSIONS: Our data demonstrate that combining gemcitabine and proton irradiation enhances apoptosis in human pancreatic cancer cells when XIAP levels decrease. Therefore, XIAP may play an important role in human pancreatic cancer proton radioresistance.

Diffusion-weighted imaging improves outcome prediction in pediatric traumatic brain injury.

Diffusion-weighted imaging (DWI) and consequent apparent diffusion coefficient (ADC) maps have been used for lesion detection and as a predictor of outcome in adults with traumatic brain injury (TBI), but few studies have been reported in children. We evaluated the role of DWI and ADC for outcome prediction after pediatric TBI (n=37 TBI; n=10 controls). Fifteen regions of interest (ROIs) were manually drawn on ADC maps that were grouped for analysis into peripheral gray matter, peripheral white matter, deep gray and white matter, and posterior fossa. All ROIs excluded areas that appeared abnormal on T2-weighted images (T2WI). Acute injury severity was measured using the Glasgow Coma Scale (GCS) score, and 6-12-month outcomes were assessed using the Pediatric Cerebral Performance Category Scale (PCPCS) score. Patients were categorized into five groups: (1) controls; (2) all TBI patients; (3) mild/moderate TBI with good outcomes; (4) severe TBI with good outcomes; and (5) severe TBI with poor outcomes. ADC values in the peripheral white matter were significantly reduced in children with severe TBI with poor outcomes (72.8+/-14.4x10(-3) mm2/sec) compared to those with severe TBI and good outcomes (82.5+/-3.8x10(-3) mm2/sec; p<0.05). We also found that the average total brain ADC value alone had the greatest ability to predict outcome and could correctly predict outcome in 84% of cases. Assessment of DWI and ADC values in pediatric TBI is useful in evaluating injury, particularly in brain regions that appear normal on conventional imaging. Early identification of children at high risk for poor outcome may assist in aggressive clinical management of pediatric TBI patients.

Multi-modal magnetic resonance imaging alterations in two rat models of mild neurotrauma.

Magnetic resonance imaging (MRI) is increasingly used in the assessment of the severity and progression of neurotrauma. We evaluated temporal and regional changes after mild fluid percussion (FPI) and controlled cortical impact (CCI) injury using T2-weighted-imaging (T2WI) and diffusion-weighted imaging (DWI) MRI over 7 days. Region of interest analysis of brain areas distant to the injury site (such as the hippocampus, retrosplenial and piriform cortices, and the thalamus) was undertaken. In the hippocampus of CCI animals, we found a slow increase (51%) in apparent diffusion coefficients (ADC) over 72 h, which returned to control values. The hippocampal T2 values in the CCI animals were elevated by 18% over the 7-day time course compared to control, indicative of edema formation. Histological analysis supported the lack of overt cellular loss in most brain regions after mild CCI injury. FPI animals showed a generalized decrease in hippocampal ADC values over the first 72 h, which then returned to sham levels, with decreased T2 values over the same period, which remained depressed at 7 days. Histological assessment of FPI animals revealed numerous shrunken cells in the hippocampus and thalamus, but other regions showed little damage. Increased immunohistochemical staining for microglia and astroglia at 7 days post-injury was greater in FPI animals within the affected brain regions. In summary, traumatic brain injury is less severe in mild CCI than FPI, based on the temporal events assessed with MRI.