Tumor cell-organized fibronectin is required to maintain a dormant breast cancer population [preprint]

Tumors can undergo long periods of dormancy, with cancer cells entering a largely quiescent, non-proliferative state before reactivation and outgrowth. For a patient, these post-remission tumors are often drug resistant and highly aggressive, resulting in poor prognosis. To understand the role of the extracellular matrix (ECM) in regulating tumor dormancy, we created an in vitro cell culture system that combines carefully controlled ECM substrates with nutrient deprivation to observe entrance into and exit from dormancy with live imaging. We saw that cell populations capable of surviving entrance into long-term dormancy were heterogeneous, containing quiescent, cell cycle arrested, and actively proliferating cells. Cell populations that endured extended periods of serum-deprivation-induced dormancy formed an organized, fibrillar fibronectin matrix via αvβ3 and α5β1 integrin adhesion, ROCK-generated tension, and TGFβ2 stimulation. We surmised that the fibronectin matrix was primarily a mediator of cell survival, not proliferation, during the serum-deprivation stress, bacause cancer cell outgrowth after dormancy required MMP-2-mediated fibronectin degradation. Given the difficulty of animal models in observing entrance and exit from dormancy in real-time, we propose this approach as a new, in vitro method to study factors important in regulating dormancy, and we used it here to elucidate a role for fibronectin deposition and MMP activation

Estimating tag-reporting rates for Atlantic tropical tuna fleets using coincidental tag return and tag seeding experiment data

One of the most important biases to consider in tagging capture-recapture data for stock assessment studies is the proportion of reported tags among the actual recaptures, i.e., the tag-reporting rate. In this study, we used the model developed by Kimura (1976) and adapted in a Bayesian framework by Carruthers et al. (2015) to estimate the reporting rates for thirteen Atlantic Ocean tuna fleets using coincidental tagging data and catch data disaggregated by species, school-type (Fish Aggregating Device and Free Swimming Schools), location and time. The method was applied on recaptures and tag seeding experiments conducted during the Atlantic Ocean Tropical Tuna Tagging Program (AOTTP) of the ICCAT (International Commission for the Conservation of Atlantic Tunas). Tag seeding consists of secretly planting tags on fish by observers onboard fishing vessels to estimate how many tags are found during later stages (landing, processing, etc.) and reported to scientific authorities. Our results showed that the tag-reporting rate was as large as 84.70% (80.58–88.39%) for the European Union purse seiner fleet (Spain and France) but decreased for several surface fleets from 72.79% (67.49–77.77%) for the Spanish baitboats (operating off Senegal or in Canary islands) to 22.83% (15.26–31.24%) for the Ghanaian mixed purse seiner-baitboat fishery. Overall, we conclude that given the very low reporting rate for several important fleets operating in the Atlantic Ocean, it is crucial to account for the reporting rate estimates to avoid highly biased results in future stock assessment using tagging data