Decrease of p400 ATPase complex and loss of H2A.Z within the p21 promoter occur in senescent IMR-90 human fibroblasts.

Replicative senescence in human diploid fibroblasts is characterised by an exhaustion of proliferative potential and permanent cell cycle arrest. During senescence, telomere shortening-generated DNA damage activates p53 pathway that upregulates cell cycle inhibitors, such as p21. Human p400 ATPase is a chromatin remodeller that plays a key role in the deposition of the histone variant, H2A.Z within the p21 promoter, repressing p21 gene expression. Decline of p400 ATPase in senescent IMR-90 cells prompted us to investigate structural changes in the chromatin of the p21 promoter during in vitro aging. Whereas doxorubicin treatment in early-passaged cells results in nucleosome density changes near the p53 binding sites of the p21 promoter, our studies show that senescent cells with a high p21 transcription activity had a comparable nucleosome distribution as unstressed young cells. However, H2A.Z that is highly enriched within the p21 promoter of young cells is depleted in senescent cells, suggesting that downregulation of p400 and loss of H2A.Z localisation play roles in relieving p21 gene repression in senescent IMR-90 cells. Taken together, our results indicate that age-dependent p400 downregulation and loss of H2A.Z localisation may contribute to the onset of replicative senescence through a sustained high rate of p21 transcription.

Evaluation of the learning curve of total robotic hysterectomy with or without lymphadenectomy for a gynecologic oncology service.

We sought to determine the learning curve for total robotic hysterectomy, bilateral salpingo-oophorectomy (TRH, BSO) with/without lymphadenectomy (LND) for a gynecologic oncology service. Data was collected prospectively and included demographics, surgical data, and timed data points to calculate times for the following categories: total operating room (OR) time, setup time, hysterectomy (HYST) time, lymphadenectomy (LND) time, and console time. Cases were grouped into tens by chronological order and compared. A risk-adjusted cumulative sum (CUSUM) model was used to evaluate learning curves for hysterectomy and lymphadenectomy. The first 155 patients are reported. Average HYST time was 45.2 min and average LND time was 52.4 min. Cases were grouped by each consecutive 10 cases per surgeon (i.e. Group 1 = cases 1-10 for each surgeon). All groups were similar with respect to age, body mass index, stage, grade, cancer type, number of lymph nodes, and uterine weight. All times significantly improved with the increase in number of cases: total OR time (P < 0.001); setup time (P = 0.004); HYST time (P = 0.001); LND time (P = 0.05); console time (P = 0.05). CUSUM analysis demonstrated a learning curve of 14 cases for HYST time and 19 cases for lymphadenectomy. Our data describes the robotic laparoscopic learning curves for both hysterectomy and lymphadenectomy in a gynecologic oncology practice and could be utilized for hospital credentialing. The amount of experience required to achieve maximum time efficiency for robotic lymphadenectomy was greater than that for hysterectomy. A significant improvement was observed in all timed data points collected, and the time to proficiency appears reasonable.