Therapy-induced APOBEC3A drives evolution of persistent cancer cells.

Acquired drug resistance to anticancer targeted therapies remains an unsolved clinical problem. Although many drivers of acquired drug resistance have been identified1-4, the underlying molecular mechanisms shaping tumour evolution during treatment are incompletely understood. Genomic profiling of patient tumours has implicated apolipoprotein B messenger RNA editing catalytic polypeptide-like (APOBEC) cytidine deaminases in tumour evolution; however, their role during therapy and the development of acquired drug resistance is undefined. Here we report that lung cancer targeted therapies commonly used in the clinic can induce cytidine deaminase APOBEC3A (A3A), leading to sustained mutagenesis in drug-tolerant cancer cells persisting during therapy. Therapy-induced A3A promotes the formation of double-strand DNA breaks, increasing genomic instability in drug-tolerant persisters. Deletion of A3A reduces APOBEC mutations and structural variations in persister cells and delays the development of drug resistance. APOBEC mutational signatures are enriched in tumours from patients with lung cancer who progressed after extended responses to targeted therapies. This study shows that induction of A3A in response to targeted therapies drives evolution of drug-tolerant persister cells, suggesting that suppression of A3A expression or activity may represent a potential therapeutic strategy in the prevention or delay of acquired resistance to lung cancer targeted therapy.

Medication use and polypharmacy in patients referred to a tertiary gastroenterology practice.

Introduction. Commonly prescribed medications are associated with various gastrointestinal (GI) side effects but few data are available on prescription medication use and polypharmacy in a gastroenterology outpatient practice. We aimed to examine the prevalence of polypharmacy, defined as the simultaneous use of 5 or more medications.Methods. A descriptive correlational study of consecutive outpatient consultations in 988 patients referred to a tertiary gastroenterology practice. Main outcome measurements were frequency of prescription medication use and polypharmacy.Results. The most common GI symptoms were abdominal pain (72%), nausea (57%), and constipation (53%). The frequency of polypharmacy was 10%. Eighty percent of patients took at least one medication and 60% took two or more. The most frequently used medication classes were proton pump inhibitors (43%), followed by benzodiazepines (30%), selective serotonin-reuptake or norepinephrine-reuptake inhibitors (28%), non-steroidal anti-inflammatory drugs (27%), and opioids (21%).Conclusion. There was a higher use of prescription medicine including antidepressants, and a lower frequency of polypharmacy in our study cohort compared to the general population. The use of medications may have contributed to the symptoms leading to our study's population GI consultation.

Hepatic iron overload identified by magnetic resonance imaging-based T2* is a predictor of non-diagnostic elastography.

BACKGROUND: Magnetic resonance elastography (MRE) is a non-invasive test used to assess liver stiffness and fibrosis in chronic liver disease, which includes systemic iron overload. However, iron deposition by itself is associated with technical failure of MRE of the liver which necessitates the use of invasive liver biopsy as an alternative monitoring method for these patients. T2*-weighted magnetic resonance imaging (T2*) is a reliable modality to asses for hepatic as well as total body iron overload. Therefore, we aimed to determine a cutoff value on the T2* reading at which MRE would no longer provide accurate stiffness measurements in patients with iron overload. METHODS: Ninety-five patients with iron overload who underwent MRE at our institution, between 2010 and 2017 were reviewed retrospectively. We compared T2* values between patients with adequate elastography (N=63) versus those with non-diagnostic elastography (N=32). We additionally examined the ability of T2* to predict the likelihood of non-diagnostic elastography by estimating area under the ROC curve (AUC). RESULTS: T2* was significantly different between patients with and without an adequate elastography (P<0.0001) and predicted occurrence of non-diagnostic elastography with an AUC of 0.95. All patients with a non-diagnostic elastography had a T2* value below 20 milliseconds (ms), and correspondingly 55% of the patients with a T2* value below 20 ms had a non-diagnostic elastography. The subgroups of patients with a T2* value ≤10, ≤8, and ≤6 ms, had a higher likelihood of non-diagnostic elastography (87%, 92%, and 95%, respectively). CONCLUSIONS: T2* can be used to accurately predict which patients are most likely to have a non-diagnostic elastography reading. T2* of 20 ms or lower reflects a higher likelihood of non-diagnostic elastography.