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Background: Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal disease with poor prognosis, as it is difficult to predict or circumvent, and it develops chemoresistance quickly. One cellular mechanism associated with chemoresistance is alternative splicing dysfunction, a process through which nascent mRNA is spliced into different isoforms. Survivin (Baculoviral IAP Repeat-Containing Protein 5 (BIRC5)), a member of the inhibitor of apoptosis (IAP) protein family and a cell cycle-associated oncoprotein, is overexpressed in most cancers and undergoes alternative splicing (AS) to generate six different splicing isoforms. Methods: To determine if survivin splice variants (SSV) could be involved in PDAC chemoresistance, a Gemcitabine (Gem) resistant (GR) cell line, MIA PaCa-2 GR, was created and assessed for its SSV levels and their potential association with GR. Cross-resistance was assessed in MIA-PaCa-2 GR cells to FIRINOX (5-fluorouracil (5-FU), irinotecan, and oxaliplatin). Once chemoresistance was confirmed, RT-qPCR was used to assess the expression of survivin splice variants (SSVs) in PDAC cell lines. To confirm the effect of SSVs on chemoresistance, we used siRNA to knockdown all SSVs or SSV 2ß. Results: The MIA PaCa-2 GR cell line was 40 times more resistant to Gem and revealed increased resistance to FIRINOX (5-fluorouracil (5-FU), irinotecan, and oxaliplatin); when compared to the parental MIA-PaCa-2 cells. RT-qPCR studies revealed an 8-fold relative expression increase in SSV 2ß and a 2- to 8-fold increase in the other five SSVs in the GR cells. Knockdown of all SSV or SSV 2ß only, using small inhibitory RNA (siRNA), sensitized the GR cells to Gem, indicating that these SSVs play a role in PDAC chemoresistance. Conclusion: These findings provide evidence for the potential role of SSV 2ß and other SSVs in innate and acquired PDAC chemoresistance. We also show that the expression of SSVs is not affected by the type of chemoresistance, therefore targeting survivin splice variants in combination with chemotherapy could benefit a wide range of patients.

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BACKGROUND: In response to the COVID-19 pandemic, the American Society of Breast Surgeons and American College of Radiology released a joint statement recommending that all breast screening studies be postponed effective March 26, 2020. STUDY DESIGN: A retrospective review of all canceled mammograms at a single tertiary care institution from January 1-August 31, 2020 was performed to evaluate the effect of this recommendation by quantifying both the number and reason for mammogram cancellations before and after March 26, 2020. Utilization of the electronic patient portal for appointment cancellation as a surrogate for telehealth uptake was noted. RESULTS: During the study period, 5340 mammogram appointments were kept and 2784 mammogram appointments were canceled. From a baseline of 30 (10.8%) canceled mammograms in January, cancellations peaked in March (576, 20.6%) and gradually decreased to a low in August (197, 7%). Reasons for cancellations varied significantly by month (P < .0001) and included COVID-19 related (236, 8.5%), unspecified patient reasons (1,210, 43.5%), administrative issues (147, 5.3%), provider requests (46, 1.7%), sooner appointments available (31, 1.1%), and reasons not given (486, 17.5%). In addition, compared to a baseline in January (51, 16.5%), electronic patient portal access peaked in August (67, 34.0%). CONCLUSION: Screening mammogram cancellations have gradually recovered after early COVID-19 restrictions were lifted and increasing use of electronic patient access appears to be sustained. Consequences for future staging at the time of diagnosis remain unknown. Understanding to what extent the pandemic affected screening may help surgeons plan for post-pandemic breast cancer care.

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The densities as a function of temperature of four fully hydrated saturated monoglycerides with even chain lengths ranging from eight to fourteen were determined by vibrating tube densitometry and their phase transition temperatures were determined by differential scanning calorimetry (DSC). We find the volume of a methylene group in a monoglyceride bilayer is 2% larger than in liquid alkanes at physiological temperatures, similar to the methylene group volumes found in phosphatidylcholine (PC) bilayers. Additionally, we carefully consider the traditional method of calculating component volumes from experimental data and note potential difficulties in this approach. In the literature, the ratio of terminal methyl volume (CH3) to methylene (CH2) volumes is typically assumed to be 2. By analysis of literature alkane data, we find this ratio actually ranges from 1.9 to 2.3 for temperatures ranging from 0 °C to 100 °C. For a rough sense of scale, we note that to effect a 2% reduction in volume requires of order 200 atmospheres of pressure, and pressures of this magnitude are biologically relevant. For instance, this amount of pressure is sufficient to reverse the effect of anesthesia. The component volumes obtained are an important parameter used for determining the structure of lipid bilayers and for molecular dynamics simulations.

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