Inter-relationship between microsatellite instability, thymidylate synthase expression, and p53 status in colorectal cancer: implications for chemoresistance

BACKGROUND: Studies indicate that thymidylate synthase (TS) expression, p53 and mismatch repair status have potential to influence colorectal cancer (CRC) outcome. There is, however, little data on the inter-relationship between these three markers. We sought to investigate whether relationships exist between these markers that might contribute to CRC phenotypes. METHODS: Four hundred and forty-one stage I-III CRCs were investigated. p53 status and TS expression were assessed by standard immunohistochemistry methods. Mismatch repair status was determined by assessment of microsatellite instability (MSI) using radiolabelled microsatellite genotyping. RESULTS: 244 tumours (55%) over-expressed p53, and 259 (58%) expressed high TS levels. 65 tumours (15%) had MSI. A significant relationship between p53 over-expression and high TS expression was observed (p = 0.01). This was independent of MSI status. A highly significant inverse relationship between MSI and p53 status was observed (p = 0.001). No relationship was seen between MSI status and TS expression (p = 0.59). CONCLUSION: Relationships exist between p53 status and TS expression, and MSI and p53 status. These inter-relationships may contribute to the clinical phenotype of CRCs associated with each of the molecular markers. High TS expression is unlikely to account for the clinical behaviour of CRCs with MSI

Dormant Cells of Staphylococcus aureus Are Resuscitated by Spent Culture Supernatant

We describe the first in vitro model of dormancy in Staphylococcus aureus, showing that cells are generated which can beresuscitated by addition of spent medium supernatant taken from cultures of the same organism. Over 30 days, culturablecounts in dormant cultures of S. aureus SH1000 fell from 106–107 cfu/ml to ,10 cfu/ml as measured by the Most ProbableNumber method in liquid culture, while total counts as determined by microscopy, and supported by data from RT-qPCR,remained around 106–107 cells/ml. Supplementing cultures with 25–50% spent medium resulted in a .600-fold increase inbacterial growth. Resuscitation was a specific effect, greatly reduced by boiling or addition of trypsin to the spentsupernatant. Supernatant also effected a reduction in lag phase of dormant cultures. SEM demonstrated the presence ofsmall coccoid cells in dormant cultures. The results are similar to those seen with resuscitation promoting factors (Rpfs) inactinobacteria. This is the first time resuscitation has been demonstrated in Staphylococcus aureus, which is an importanthuman pathogen. A better understanding of control and reactivation of dormant cells could lead to major improvements inmanaging staphylococcal infections; resuscitation could be an important step in restoring susceptibility to antibiotictreatment