Structure-function analysis of the SHOC2-MRAS-PP1C holophosphatase complex.

Receptor tyrosine kinase (RTK)-RAS signalling through the downstream mitogen-activated protein kinase (MAPK) cascade regulates cell proliferation and survival. The SHOC2-MRAS-PP1C holophosphatase complex functions as a key regulator of RTK-RAS signalling by removing an inhibitory phosphorylation event on the RAF family of proteins to potentiate MAPK signalling1. SHOC2 forms a ternary complex with MRAS and PP1C, and human germline gain-of-function mutations in this complex result in congenital RASopathy syndromes2-5. However, the structure and assembly of this complex are poorly understood. Here we use cryo-electron microscopy to resolve the structure of the SHOC2-MRAS-PP1C complex. We define the biophysical principles of holoenzyme interactions, elucidate the assembly order of the complex, and systematically interrogate the functional consequence of nearly all of the possible missense variants of SHOC2 through deep mutational scanning. We show that SHOC2 binds PP1C and MRAS through the concave surface of the leucine-rich repeat region and further engages PP1C through the N-terminal disordered region that contains a cryptic RVXF motif. Complex formation is initially mediated by interactions between SHOC2 and PP1C and is stabilized by the binding of GTP-loaded MRAS. These observations explain how mutant versions of SHOC2 in RASopathies and cancer stabilize the interactions of complex members to enhance holophosphatase activity. Together, this integrative structure-function model comprehensively defines key binding interactions within the SHOC2-MRAS-PP1C holophosphatase complex and will inform therapeutic development .

Risk factors for the recurrence in patients with early endometrioid endometrial cancer achieving complete remission for fertility-sparing hormonal treatment.

OBJECTIVE: This study aimed to assess the recurrence risk factors in patients with early-stage endometrioid endometrial cancer (EC) who achieved a complete response (CR) through fertility-sparing hormonal treatment (FST). METHODS: We retrospectively analyzed patients who received FST for presumed stage IA and grade 1 endometrioid EC at two institutions. Medroxyprogesterone (MPA)- and levonorgestrel-releasing intrauterine devices (LNG-IUD) were used concurrently. Maintenance therapy involved maintaining the LNG-IUDs in situ for those who did not attempt to conceive immediately after achieving CR. Cox regression analysis was used to identify clinicopathological variables for recurrence-free survival (RFS) following CR. RESULTS: Among 178 patients with endometrioid EC who received FST, 142 (79.8 %) achieved CR. The median time to achieve CR and the median FST duration were 10 months (range 1-34) and 14 months (range 3-49), respectively. During the median follow-up period of 44 months (range 6-143), 59.9 % (85/142) of patients had recurrence, with a median RFS of 14 months (range 1-123) after CR. In multivariable analysis, age > 35-years (hazard ratio (HR) 1.892, 95 % confidence interval (CI) 1.224-2.923; P < 0.05) and pregnancy after the first CR (HR 0.203, 95 % CI 0.093-0.444; P < 0.05) were significantly associated with RFS. CONCLUSIONS: Older age and non-pregnancy status may be risk factors for recurrence after CR. Therefore, patients with these conditions should undergo stringent follow-up, including imaging and histological examinations, to detect recurrence after CR.

Image quality and lesion detectability of deep learning-accelerated T2-weighted Dixon imaging of the cervical spine.

OBJECTIVES: To validate the subjective image quality and lesion detectability of deep learning-accelerated Dixon (DL-Dixon) imaging of the cervical spine compared with routine Dixon imaging. MATERIALS AND METHODS: A total of 50 patients underwent sagittal routine Dixon and DL-Dixon imaging of the cervical spine. Acquisition parameters were compared and non-uniformity (NU) values were calculated. Two radiologists independently assessed the two imaging methods for subjective image quality and lesion detectability. Interreader and intermethod agreements were estimated with weighted kappa values. RESULTS: Compared with the routine Dixon imaging, the DL-Dixon imaging reduced the acquisition time by 23.76%. The NU value is slightly higher in DL-Dixon imaging (p value: 0.015). DL-Dixon imaging showed superior visibility of all four anatomical structures (spinal cord, disc margin, dorsal root ganglion, and facet joint) for both readers (p value: < 0.001 ~ 0.002). The motion artifact scores were slightly higher in the DL-Dixon images than in routine Dixon images (p value = 0.785). Intermethod agreements were almost perfect for disc herniation, facet osteoarthritis, uncovertebral arthritis, central canal stenosis (κ range: 0.830 ~ 0.980, all p values < 0.001) and substantial to almost perfect for foraminal stenosis (κ = 0.955, 0.705 for each reader). There was an improvement in the interreader agreement of foraminal stenosis by DL-Dixon images, from moderate to substantial agreement. CONCLUSION: The DLR sequence can substantially decrease the acquisition time of the Dixon sequence with subjective image quality at least as good as the conventional sequence. And no significant differences in lesion detectability were observed between the two sequence types.

Minimally invasive surgery versus open surgery in high-risk histologic endometrial cancer patients: A meta-analysis.

OBJECTIVE: To compare the effects of minimally invasive surgery (MIS) and open surgery (OPS) on the risk of recurrence and mortality in patients with endometrial cancer (EC) of high-risk histology (grade 3 endometrioid adenocarcinoma, papillary serous carcinoma [PS], clear cell carcinoma [CC], and carcinosarcoma) using meta-analysis. MATERIAL AND METHODS: We systematically reviewed published studies comparing MIS and OPS in EC patients with high-risk histology until January 2022. The endpoints were recurrence and mortality rate. Study design features that may have affected participant selection, recurrence/death detection, and manuscript publication were assessed. For pooled estimates of the effect of MIS on recurrence/mortality, the random- or fixed-effects meta-analytical models were used after assessing the cross-study heterogeneity. RESULT: Nine observational studies (eight retrospective and one prospective) fulfilled our search criteria (MIS, 8877 patients; OPS, 5751 patients). The fixed-effects model-based meta-analysis indicated that MIS did not significantly increase the risk of recurrence (hazard ratio [HR], 0.86; 95% confidence interval [CI], 0.71-1.05; p = 0.13) and mortality (HR, 0.86; 95% CI, 0.79-0.93; p < 0.001) when compared with OPS. This pattern was also observed in the subgroup analyses based on the stage (early stage vs. all stage), histology (PS and CC), and MIS type (laparoscopy vs. robotic). There was no evidence of publication bias. CONCLUSION: This meta-analysis of observational studies revealed that MIS did not compromise the prognosis of EC patients with high-risk histology. Well-designed randomized controlled trials could verify the results of this uncommon but deadly tumor.

Retreatment with progestin for recurrence after complete response with fertility-sparing treatment in patients with endometrial cancer.

OBJECTIVE: To assess the outcomes of retreatment using progestin for recurrence after a complete response with fertility-sparing treatment in patients with early endometrial cancer. METHODS: We retrospectively reviewed the data of patients with presumed stage IA, grade 1 endometrioid endometrial cancer who developed intra-uterine recurrence after a complete response with fertility-sparing treatment using progestin. Oncological and pregnancy outcomes were analyzed after repeated fertility-sparing treatment. Logistic and Cox regression analyses were performed to analyze the prognostic factors associated with a complete response with secondary fertility-sparing treatment and recurrence-free survival after secondary fertility-sparing treatment, respectively. RESULTS: Fifty patients with a median age of 31 years (range 23-40) underwent secondary fertility-sparing treatment. With a median secondary progestin treatment duration of 9 months (range 3-55), the complete response rate was 78% (39/50) and no patients had extra-uterine spread of disease. Among the 26 (67%) patients who attempted to conceive after complete response, 10 became pregnant (3 spontaneous abortions, 7 live births). Eighteen (46.1%) patients had a second recurrence, with a median recurrence-free survival after secondary fertility-sparing treatment of 14 months (range 3-36); 15 patients received tertiary fertility-sparing treatment and nine (60%) achieved a complete response. Polycystic ovary on ultrasound (OR 5.82, 95% CI 1.1 to 30.6, p=0.037) was associated with an increased complete response rate with secondary fertility-sparing treatment. Multivariable analysis revealed that recurrence-free survival after initial hormonal treatment >6 months (HR 0.11, 95% CI 0.02 to 0.51, p=0.005) and pregnancy after secondary fertility-sparing treatment (HR 0.27, 95% CI 0.08 to 0.98; p=0.047) were significantly associated with longer recurrence-free survival after secondary fertility-sparing treatment. CONCLUSIONS: Repeated progestin treatment was associated with a 78% response rate and it was safe in patients with intra-uterine recurrent endometrial cancer. Thus, it might help preserve fertility after first and second recurrences.

Zileuton Alleviates Radiation-Induced Cutaneous Ulcers via Inhibition of Senescence-Associated Secretory Phenotype in Rodents.

Radiation-induced cutaneous ulcers are a challenging medical problem for patients receiving radiation therapy. The inhibition of cell senescence has been suggested as a prospective strategy to prevent radiation ulcers. However, there is no effective treatment for senescent cells in radiation ulcers. In this study, we investigated whether zileuton alleviated radiation-induced cutaneous ulcer by focusing on cell senescence. We demonstrate increased cell senescence and senescence-associated secretory phenotype (SASP) in irradiated dermal fibroblasts and skin tissue. The SASP secreted from senescent cells induces senescence in adjacent cells. In addition, 5-lipoxygenase (5-LO) expression increased in irradiated dermal fibroblasts and skin tissue, and SASP and cell senescence were regulated by 5-LO through p38 phosphorylation. Finally, the inhibition of 5-LO following treatment with zileuton inhibited SASP and mitigated radiation ulcers in animal models. Our results demonstrate that inhibition of SASP from senescent cells by zileuton can effectively mitigate radiation-induced cutaneous ulcers, indicating that inhibition of 5-LO might be a viable strategy for patients with this condition.

Potassium channel selectivity filter dynamics revealed by single-molecule FRET.

Potassium (K) channels exhibit exquisite selectivity for conduction of K+ ions over other cations, particularly Na+. High-resolution structures reveal an archetypal selectivity filter (SF) conformation in which dehydrated K+ ions, but not Na+ ions, are perfectly coordinated. Using single-molecule FRET (smFRET), we show that the SF-forming loop (SF-loop) in KirBac1.1 transitions between constrained and dilated conformations as a function of ion concentration. The constrained conformation, essential for selective K+ permeability, is stabilized by K+ but not Na+ ions. Mutations that render channels nonselective result in dilated and dynamically unstable conformations, independent of the permeant ion. Further, while wild-type KirBac1.1 channels are K+ selective in physiological conditions, Na+ permeates in the absence of K+. Moreover, whereas K+ gradients preferentially support 86Rb+ fluxes, Na+ gradients preferentially support 22Na+ fluxes. This suggests differential ion selectivity in constrained versus dilated states, potentially providing a structural basis for this anomalous mole fraction effect.

Optimal duration of fertility-sparing hormonal treatment for early-stage endometrioid endometrial cancer.

OBJECTIVES: To analyze the oncologic outcomes of long-term fertility-sparing treatment (FST) in patients with early-stage endometrial cancer (EC) and to determine the optimal duration of FST that would not hamper survival outcomes. METHODS: Patients undergoing FST for presumed stage IA, grade 1 EC between 2005 and 2018 were retrospectively analyzed. Oncologic outcomes were compared between the group with ≤6 months of FST and the group with >6 months of FST. Segmented regression analysis was used to estimate the dynamic changes in cumulative complete response (CR) rates according to FST duration. RESULTS: A total of 122 patients received oral progestin, with concurrent levonorgestrel-releasing intrauterine device use in 108 (88.5%) and 105 (86.1%) achieved CR with a median time to achieve CR of 10 (3-42) months. Of the patients not achieving CR at 6 months of FST, 95.1% (78/82) continued further FST. The overall CR rate (88.9% [32/36] vs. 84.9% [73/86], P = 0.436] was not significantly different between the groups with ≤6 and > 6 months of FST. The changes in cumulative CR rates were significantly different between the two segments divided by 15 months from the initial FST (P = 0.0015, segmented regression analysis). The overall progressive disease (PD) rate was 3.3% (4/122), and PD was first detected during 9-12 months of FST. CONCLUSION: Patients not achieving CR and not showing PD at 6 months of FST could continue further FST. If disease progression is excluded, 15 months of FST can be considered as the cutoff for the optimal FST duration.

Peripheral nerve sheath tumor: differentiation of malignant from benign tumors with conventional and diffusion-weighted MRI.

OBJECTIVES: To evaluate potential of conventional MRI and diffusion-weighted imaging (DWI) for differentiating malignant from benign peripheral nerve sheath tumors (PNSTs). METHODS: Eighty-seven cases of malignant or benign PNSTs in the trunk or extremities that underwent conventional MRI with contrast enhancement, DWI, and pathologic confirmation between Sep. 2014 and Dec. 2017 were identified. Of these, 55 tumors of uncertain nature on MRI were included. Tumor size, signal, and morphology were reviewed on conventional MRI, and apparent diffusion coefficient (ADC) values of solid enhancing portions were measured from DWI. Patient demographics, MRI features, and ADC values were compared between benign and malignant tumors, and robust imaging findings for malignant peripheral nerve sheath tumors (MPNSTs) were identified using multivariable models. RESULTS: A total of 55 uncertain tumors consisted of 18 malignant and 37 benign PNSTs. On MRI, tumor size, margin, perilesional edema, and presence of split fat, fascicular, and target signs were significantly different between groups (p < 0.05), as were mean and minimum ADC values (p = 0.002, p < 0.0001). Most inter-reader agreement was moderate to excellent (κ value, 0.45-1.0). The mean ADC value and absence of a split fat sign were identified as being associated with MPNSTs (odds ratios = 13.19 and 25.67 for reader 1; 49.05 and 117.91 for reader 2, respectively). The C-indices obtained by combining these two findings were 0.90 and 0.95, respectively. CONCLUSIONS: Benign and malignant PNSTs showed different features on MRI and DWI. A combination of mean ADC value and absence of split fat was excellent for discriminating malignant from benign PNSTs. KEY POINTS: • It is important to distinguish between malignant peripheral nerve sheath tumors (MPNSTs) and benign peripheral nerve sheath tumors (BPNSTs) to ensure an appropriate treatment plan. • On conventional MRI and diffusion-weighted imaging (DWI), MPNSTs and BPNSTs showed significant differences in tumor size, margin, presence of perilesional edema, and absence of split fat, fascicular, and target signs. • Absence of a split fat sign and mean apparent diffusion coefficient (ADC) values were robust imaging findings distinguishing MPNSTs from BPNSTs, with a C-index of > 0.9.

Computed tomography arthrography of the shoulder with tin filter-based spectral shaping at 100 kV and 140 kV.

BACKGROUND: Tin filter-based spectral shaping has been used for low-dose and ultra-low-dose computed tomography (CT) in several body parts. However, studies of shoulder CT arthrography with spectral shaping are limited. PURPOSE: To investigate image quality and radiation dose of shoulder CT arthrography with tin filter-based spectral shaping at 100 kV (Sn 100 kV) and 140 kV (Sn 140 kV) in comparison with the conventional protocol. MATERIAL AND METHODS: Ninety-nine shoulder CT arthrographies with protocols of Sn 100 kV (n = 32), Sn 140 kV (n = 25), and conventional 120 kV (n = 42) were retrospectively evaluated. Qualitative image quality, CT attenuations of intra-articular contrast mixture and tissues, background noise, contrast-to-noise ratios (CNRs), and figures of merit were assessed. Radiation doses were compared. RESULTS: CT arthrographies with Sn 100 kV and Sn 140 kV yielded approximately 70% and 60% radiation dose reduction, respectively, compared with the conventional 120 kV (P < 0.001). Qualitative image noise and quantitative background noise of Sn 100 kV and Sn 140 kV were significantly less than those of the conventional protocol. Qualitative image contrast, CT attenuations of intra-articular contrast mixture and tissues, and CNRs for Sn 100 were similar to those of the conventional 120 kV. However, Sn 140 kV showed significantly lower qualitative contrast and CNRs than 120 kV. Sn 100 kV was the most dose efficient among the three protocols. CONCLUSION: Shoulder CT arthrography with Sn 100 kV substantially reduced radiation dose and image noise and maintained image contrast, compared with the conventional protocol.