Cancer cells maintain their telomeres by either re-activating telomerase or adopting the homologous recombination (HR)-based Alternative Lengthening of Telomere (ALT) pathway. Among the many prominent features of ALT cells, C-circles (CC) formation is considered to be the most specific and quantifiable biomarker of ALT. However, the molecular mechanism behind the initiation and maintenance of CC formation in ALT cells is still largely unknown. We reported previously that depletion of the FANCM complex (FANCM-FAAP24-MHF1&2) in ALT cells induced pronounced replication stress, which primarily takes place at their telomeres. Here, we characterized the changes in ALT associated phenotypes in cells deficient of the FANCM complex. We found that depletion of FAAP24 or FANCM, but not MHF1&2, induces a dramatic increase of CC formation. Most importantly, we identified multiple DNA damage response (DDR) and DNA repair pathways that stimulate the dramatic increase of CC formation in FANCM deficient cells, including the dissolvase complex (BLM-TOP3A-RMI1/2, or BTR), DNA damage checkpoint kinases (ATR and Chk1), HR proteins (BRCA2, PALB2, and Rad51), as well as proteins involved in Break-Induced Replication (BIR) (POLD1 and POLD3). In addition, FANCD2, another Fanconi Anemia (FA) protein, is also required for CC formation, likely through promoting the recruitment of BLM to the replication stressed ALT telomeres. Finally, we demonstrated that TERRA R-loops accumulate at telomeres in FANCM deficient ALT cells and downregulation of which attenuates the ALT-associated PML bodies (APBs), replication stress and CC formation. Taken together, our data suggest that FANCM prevents replisomes from stalling/collapsing at ALT telomeres by disrupting TERRA R-loops.

BACKGROUND Obscure small bowel bleeding is defined as gastrointestinal bleeding (GIB) that is unidentifiable with esophagogastroduodenoscopy and a colonoscopy with video capsule endoscopy (VCE) being the next gold standard step for evaluation. Small bowel transit time (SBTT) is a metric of a VCE study that is defined as the time the capsule takes to travel through the small intestine. AIM To determine if SBTT within the VCE study, correlates to overall detection of obscure small bowel bleeds. Furthermore, we attempted to identify any existing correlation between SBTT and re-bleeding after a negative VCE study. METHODS This is a single center retrospective analysis of VCE studies performed for overt and occult GIB at Einstein Medical Center, Philadelphia, between 2015 and 2019. Inclusion criteria primarily consisted of patients 18 years or older who had a VCE study done as part of the workup for a GIB. Patients with incomplete VCEs, poor preparation, or with less than 6 mo of follow up were excluded. A re-bleeding event was defined either as overt or occult within a 6-mo timeframe. Overt re-bleeding was defined as Visible melena or hematochezia with > 2 gm/dL drop in hemoglobin defined an overt re-bleeding event; whereas an unexplained > 2 gm/dL drop in hemoglobin with no visible bleeding defined an occult re-bleed. RESULTS Results indicated that there was a significant and positive point biserial correlation between SBTT of 220 min and detection of a bleeding focus with a statistically significant p value of 0.008. However, the area under the curve was negligible when trying to identify a threshold time for SBTT to discriminate between risk of re-bleeding events after a negative VCE. CONCLUSION In terms of SBTT and association with accuracy of VCE finding a bleeding focus, 220 min was found to be adequate transit time to accurately find a bleeding focus, when present. It was found that no threshold SBTT could be identified to help predict re-bleeding after a negative VCE.

A 51-year-old female with a history of hypertension, and severe cyclic vomiting syndrome (CVS) secondary to gastroparesis, presented with acute onset nausea, vomiting, epigastric and substernal discomfort. Electrocardiogram (ECG) revealed non-specific T-wave abnormalities (Figure 1A-B) and serum troponin T was 5.54 ng/mL (normal value: < 0.05 ng/mL). Coronary

The median GRWR and postperfusion portal vein flow in the RLLS group were 2.3 (1.5-3.1) and 132 mL/100 g liver tissue. The overall, <10 Kg LLS and RLLS recipient operative mortalities were 3%, 22%, and 0%; HAT rates were 1.8%, 11%, and 0%, and PVT rates were 6%, 22%, and 11%, respectively. The single patient with HA thrombosis died, while all the 3 PVTs were successfully treated at re-laparotomy. Mesh was used for abdominal closure only in the patient with GRWR of 4.1. Conclusion: Routine reduction of LLS grafts to GRWR <2.5 provides better size-matched livers for children under 10 Kg, results in a low incidence of serious vascular complications, circumvents the difficulties in abdominal closure, and results in excellent patient and graft survival.

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