Preoperative US Integrated Random Forest Model for Predicting Delphian Lymph Node Metastasis in Patients with Papillary Thyroid Cancer.

BACKGROUND: Delphian lymph node (DLN) has been considered to be a gate that predicts widespread lymph node involvement, higher recurrence and mortality rates of head and neck cancer. OBJECTIVE: This study aimed to establish a preoperative ultrasonography integrated machine learning prediction model to predict Delphian lymph node metastasis (DLNM) in patients with diagnosed papillary thyroid carcinoma (PTC). METHODS: Ultrasonographic and clinicopathologic variables of PTC patients from 2014 to 2021 were retrospectively analyzed. The risk factors associated with DLNM were identified and validated through a developed random forest (RF) algorithm model based on machine learning and a logistic regression (LR) model. RESULTS: A total of 316 patients with 402 thyroid lesions were enrolled for the training dataset and 280 patients with 341 lesions for the validation dataset, with 170 (28.52%) patients developed DLNM. The elastography score of ultrasonography, central lymph node metastasis, lateral lymph node metastasis, and serum calcitonin were predictive factors for DLNM in both models. The RF model has better predictive performance in the training dataset and validation dataset (AUC: 0.957 vs. 0.890) than that in the LR model (AUC: 0.908 vs. 0.833). CONCLUSION: The preoperative ultrasonography integrated RF model constructed in this study could accurately predict DLNM in PTC patients, which may provide clinicians with more personalized clinical decision-making recommendations preoperatively. Machine learning technology has the potential to improve the development of DLNM prediction models in PTC patients.

Binding of cyclic diguanylate in the non-catalytic EAL domain of FimX induces a long-range conformational change.

FimX is a multidomain signaling protein required for type IV pilus biogenesis and twitching motility in the opportunistic pathogen Pseudomonas aeruginosa. FimX is localized to the single pole of the bacterial cell, and the unipolar localization is crucial for the correct assembly of type IV pili. FimX contains a non-catalytic EAL domain that lacks cyclic diguanylate (c-di-GMP) phosphodiesterase activity. It was shown that deletion of the EAL domain or mutation of the signature EVL motif affects the unipolar localization of FimX. However, it was not understood how the C-terminal EAL domain could influence protein localization considering that the localization sequence resides in the remote N-terminal region of the protein. Using hydrogen/deuterium exchange-coupled mass spectrometry, we found that the binding of c-di-GMP to the EAL domain triggers a long-range (∼ca. 70 Å) conformational change in the N-terminal REC domain and the adjacent linker. In conjunction with the observation that mutation of the EVL motif of the EAL domain abolishes the binding of c-di-GMP, the hydrogen/deuterium exchange results provide a molecular explanation for the mediation of protein localization and type IV pilus biogenesis by c-di-GMP through a remarkable allosteric regulation mechanism.