Developing a clinical care pathway to reduce and treat enteric feeding tube site skin excoriation: a quality-improvement pilot study.

Skin excoriation is a common complication of enteral tube feeding; however, universal guidelines for treatment do not exist. A quality improvement pilot study to inform the development of a local clinical care pathway was conducted. The enteral nutrition team identified products and assessed patient preference, ease of use, availability, and clinical outcomes for inclusion. This pathway includes gentle site cleansing followed by skin protectant application. For mild skin excoriation (<5 mm), acrylate terpolymer barrier film (3M Cavilon No Sting Barrier Film) was applied once every seven days. Moderate skin excoriation (5-20 mm) received acrylate terpolymer barrier film twice a day for seven days. Severe skin excoriation (>20 mm) received advanced elastomeric skin protectant (3M Cavilon Advanced Skin Protectant) applied once every 3-4 days for 2-4 weeks. Ten patients were included, three were selected for discussion. Adoption of this local clinical care pathway resulted in skin healing and improved patient comfort.

Dissection of the sequence-specific DNA binding and exonuclease activities reveals a superactive yet apoptotically impaired mutant p53 protein.

Both sequence-specific DNA binding and exonuclease activities have been mapped to the central conserved core domain of p53. To gain more information about these two activities a series of mutants were generated that changed core domain histidine residues. Of these mutants, only one, H115N p53, showed markedly reduced exonuclease activity (ca. 15% of wild-type). Surprisingly, purified H115N p53 protein was found to be significantly more potent than wild-type p53 in binding to DNA by several criteria including gel mobility shift assay, filter binding and DNase I footprinting. Interestingly as well, non-specific DNA binding by the core domain of H115N p53 is superior to that of wild-type p53. To study H115N p53 in vivo, clones of H1299 cells expressing tetracycline regulated wild-type or H115N p53 were generated. H115N was both more potent than wild-type p53 in inducing p53 target genes such as p21 and PIG3 and was also more effective in arresting cells in G1. Unexpectedly, in contrast to wild-type p53, H115N p53 was markedly impaired in causing apoptosis when cells were subjected to DNA damage. Our results indicate that the exonuclease activity and transcriptional activation functions of p53 can be separated. They also extend previous findings showing that cell cycle arrest and apoptosis are separable functions of p53. Finally, these experiments confirm that DNA binding and xonuclease activities are distinct features of the p53 core domain.

p53 in the cytoplasm: a question of overkill?

The tumor suppressor p53 regulates cellular responses to stress by serving in the nucleus to regulate transcription of genes involved in processes including cell cycle arrest, DNA repair, and apoptosis. Nevertheless, recent papers show that p53 may have a separate cytoplasmic role in directly regulating the Bax-dependent mitochondrial pathway to cell death.

The proline-rich domain of p53 is required for cooperation with anti-neoplastic agents to promote apoptosis of tumor cells.

In some cell types either DNA damage or p53 expression leads to minimal cell death, while combining the two leads to a strong apoptotic response. To further understand features of p53 that contribute to this increased cell death we used clones of H1299 cells that express wild-type or several mutant forms of p53 under a tetracycline-regulated promoter. In these cells the induction of wild-type p53 leads to significant apoptosis only when combined with exposure to a number of chemotherapeutic agents. A common target of p53, p21, is itself not sufficient to cause apoptosis in the presence of these chemotherapeutic compounds. Many agents also effectively increase cell death when a transcriptionally-defective p53, p53([gln22ser23]), is induced, although a dramatic exception is treatment with 5-FU, which strongly cooperates with wild-type but not p53([gln22ser23]). Our results with 5-FU thus show that genetically separable functions of p53 are involved in its ability to respond to DNA-damaging agents to induce apoptosis. Notably as well, deleting the C-terminal 30 amino acids of p53 does not affect this cooperative effect with DNA-damaging agents. By contrast, a p53 mutant lacking the PXXP-domain between residues 60-90, while at least partially transcriptionally-competent, cannot be rendered apoptotic by any compounds that we tested. Thus the PXXP domain provides an essential component of the ability of p53 to respond to DNA-damaging agents to cause cell death.