Some great research to touch on this week in top-notch journals including Science, Cell, and NEJM. The first publication really emphasizes the strength of collaborative research projects around the globe.
Understanding Endometriosis: Ovarian clear-cell carcinomas are less common than high-grade serous carcinomas (12% and 70% of total respectively), but still remain the second leading cause of death from ovarian cancer. It is important that the mechanisms behind the formation of this rare subtype are elucidated because it is not responsive to conventional platinum-taxane chemotherapeutic regimes that are currently the first-line treatment for ovarian cancer. In a comprehensive study published in The New England Journal of Medicine, researchers sequence the entire transcriptomes of 18 ovarian clear-cell carcinomas and identify frequent somatic mutations in the tumor suppressor gene ARID1A (the AT-rich interactive domain 1A). ARID1A encodes the protein BAF250a which in turn is part of the chromatin remodeling complex SWI-SNF that regulates a diversity of cellular processes including DNA repair and tumor suppression. Interestingly, the mutation appears specific to the clear-cell and endometrioid subtypes. After identifying the ARID1A mutation, researchers carried out targeted re-sequencing in a mutation-validation cohort consisting of an additional 210 carcinoma samples from all subtypes. Combining the discovery cohort and validation cohort, the ARID1A mutation was found in 55 of 119 clear cell carcinomas (46%), 10 of 33 endometrioid carcinomas (30%), but not one of 76 high-grade serous ovarian carcinomas. These findings strongly implicate ARID1A mutation in the early transformation of endometriosis into cancer and the genesis of clear-cell and endometrioid ovarian carcinomas. This exhaustive work was carried out by some 45 researchers in a dozen or so institutions found in Canada, the United States, and Australia.
Danger Signaling: Physical injury to tissue leads to cell necrosis and the release of special patterning molecules, including proteins, nucleic acids, extra-cellular matrix proteins, and various lipids as a complex milieu of chemotaxic signals. Neutrophils are able to use these unique signals to guide themselves to the site of a wound, and play an important role in recycling debris from dying cells. In a study published in Science, led by Dr. Paul Kubes of the Immunology Research Group at the University of Calgary, researchers used a mouse model of sterile injury and an in vivo imaging technique known as spinning disk confocal microscopy to observe the kinetics of eGFP-expressing neutrophils in response to thermal induced necrotic injury. Experiments revealed that necrotic cells activated a multistep hierarchy of cues that lured neutrophils to the site of danger. Another interesting finding of the study is that neutrophils appear to travel to the site of injury intravascularly as opposed to taking the most direct route through tissue. The group proposes that danger sensing and recruitment mechanisms may have evolved to prioritize intravascular travel in order to reduce the collateral damage incurred if neutrophils were to migrate directly through healthy tissue.
In Pursuit of Perfection: The fundamental limit of minimally invasive surgery is at the level of the single cell. In principal, lasers are capable of operating at this spatial resolution however efforts to achieve this have been limited by thermal and shock wave induced collateral damage to surrounding tissue. The long-held promise of a fine surgical laser has been delivered by two investigators in the Toronto research community with the creation of a novel laser source – the Picosecond IR Laser (PIRL). As a cutting modality the PIRL has a shorter pulse duration than conventional surgical lasers, vaporizing tissue on the picosecond timescale rather than burning on the nanosecond, and exploits a new cutting mechanism that selectively energizes water molecules. Researchers created full thickness wounds in CD1 mice using PIRL to demonstrate that it caused neither cavitation or any associated shock wave induced damage, and also showed that PIRL greatly reduced scar formation by comparison to conventional surgical laser or scalpel. The technology is expected to be useful in surgical procedures where scarring is particularly debilitating. Dr. Benjamin Alman, Head of the Division of Orthopedic Surgery at Sick Kids, and Dr. Dwayne Miller, in the Department of Chemistry at the University of Toronto, were co-principal investigators in this study published in PloS ONE.
At the Junction: The RAS/MAPK signaling pathway contributes to a number of important cellular processes including proliferation, differentiation, and survival. In its most basic form the pathway is regulated by the small GTPase RAS, and the three core kinases RAF, MEK, and ERK/MAPK. Like most signaling pathways, the RAS/MAPK pathway is controlled by a diversity of post-translational modifications but much less is known about regulation of its core protein components at the mRNA stage. Using a genome-wide RNAi screen in Drosophila S2 cells, researchers set out to identify other proteins involved in the pathway that could modulate MAPK protein levels. In doing so they identified the Exon Junction Complex (EJC) as a regulator of mapk transcripts. The complex is believed to contribute to the regulation of exon definition and suggests that the EJC has a key role in early regulation the RAS/MAPK pathway. This study, published in Cell, was led by Dr. Marc Therrien at the University of Montreal.