Consequences of the Hsp110DE9 mutation in tumorigenesis and the 5-fluorouracil-based chemotherapy response in Msh2-deficient mice.

Heat shock proteins (HSPs) play oncogenic roles in human tumours. We reported a somatic inactivating mutation of HSP110 (HSP110DE9) in mismatch repair-deficient (dMMR) cancers displaying microsatellite instability (MSI) but did not assess its impact. We evaluated the impact of the Hsp110DE9 mutation on tumour development and the chemotherapy response in a dMMR knock-in mouse model (Hsp110DE9KIMsh2KO mice). The effect of the Hsp110DE9 mutation on tumorigenesis and survival was evaluated in Msh2KO mice that were null (Hsp110wt), heterozygous (Hsp110DE9KI/+), or homozygous (Hsp110DE9KI/KI) for the Hsp110DE9 mutation by assessing tumoral syndrome (organomegaly index, tumour staging) and survival (Kaplan-Meier curves). 5-Fluorouracil (5-FU), which is the backbone of chemotherapy regimens in gastrointestinal cancers and is commonly used in other tumour types but is not effective against dMMR cells in vivo, was administered to Hsp110DE9KI/KI, Hsp110DE9KI/+, and Hsp110wtMsh2KO mice. Hsp110, Ki67 (proliferation marker) and activated caspase-3 (apoptosis marker) expression were assessed in normal and tumour tissue samples by western blotting, immunophenotyping and cell sorting. Hsp110wt expression was drastically reduced or totally lost in tumours from Msh2KOHsp110DE9KI/+ and Msh2KOHsp110DE9KI/KI mice. The Hsp110DE9 mutation did not affect overall survival or tumoral syndrome in Msh2KOHsp110DE9KI/+ and Msh2KOHsp110DE9KI/KI mice but drastically improved the 5-FU response in all cohorts (Msh2KOHsp110DE9KI/KI: P5fu = 0.001; Msh2KOHsp110DE9KI/+: P5fu = 0.005; Msh2KOHsp110wt: P5fu = 0.335). Histopathological examination and cell sorting analyses confirmed major hypersensitization to 5-FU-induced death of both Hsp110DE9KI/KI and Hsp110DE9KI/+ dMMR cancer cells. This study highlights how dMMR tumour cells adapt to HSP110 inactivation but become hypersensitive to 5-FU, suggesting Hsp110DE9 as a predictive factor of 5-FU efficacy.

Rectovaginal fistula model in the New Zealand white rabbit.

INTRODUCTION AND HYPOTHESIS: The purpose of this study was to create an animal model to study rectovaginal fistula repair. METHODS: Fourteen New Zealand white rabbits underwent surgical creation of a rectovaginal fistula. The technique was developed with a pilot study conducted on the first two animals, then standardized and performed on the remaining 12 rabbits. The standardized technique included making a defect in the rectovaginal septum using a 3-mm skin punch then splinting the defect with 6-mm tubing for 2 weeks. RESULTS: Using the standardized technique, a fistula was successfully created in all 12 rabbits ranging from 1 to 5 mm (mean = 2.8 mm, SD = 1.1). A 95% tolerance interval was calculated for the model and predicted that a successful fistula can be created ranging from 0.3 to 5.2 mm in 85% of attempts with the model. CONCLUSION: The New Zealand white rabbit is a promising animal model to study rectovaginal fistula repair.

Overactive bladder medication adherence when medication is free to patients.

PURPOSE: We examined overactive bladder medication compliance in a health care system in which patients do not pay for medication. MATERIALS AND METHODS: Pharmacy dispensing records were reviewed for antimuscarinic agents from January 2003 to December 2006 for the United States Military Health System National Capital Region. Medication nonpersistence, switching and adherence were examined. Kaplan-Meier survival analysis was done to compare medication persistence duration. RESULTS: Overactive bladder medications were dispensed to 7,879 adults. Tolterodine extended release (4,716 patients or 60%) and oxybutynin immediate release (2,003 or 25.5%) were most commonly prescribed. The medication nonpersistence rate, defined as the proportion of patients who never refilled a prescription for antimuscarinics during the study period, was 35.1% (2,760 of 7,858). Of 5,098 patients who refilled a prescription 1,305 changed the medication or dose at least once for a medication switch rate of 25.6%. The overall median medication possession ratio, defined as the total days of medication dispensed except for the last refill divided by the number of days between the first dispense date and the last refill date, was 0.82 in all cases. Men had a significantly higher median medication possession ratio than women (0.86 vs 0.81, p <0.001). Of patients who obtained at least 1 refill women remained on medication longer than men (median 606 vs 547 days, p = 0.01). Patients on tolterodine extended release had a higher medication nonpersistence rate than those on oxybutynin immediate release (0.89 vs 0.68, p <0.01). There was no difference between extended release medications. CONCLUSIONS: In a health care system in which patients do not pay for medications 35% of patients did not refill a prescription for overactive bladder medication, similar to previous reports. However, other measures of medication compliance were higher than those published previously in systems with copays.