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This paper presents a new method for accurately measuring the vocabulary size of second language (L2) learners. Traditional vocabulary size tests (VSTs) are limited in capturing a tester's vocabulary and are often population-specific. To overcome these issues, we propose an intelligent vocabulary size measurement method that utilizes massive robot testers. They are equipped with randomized and word-frequency-based vocabularies to simulate L2 learners' variant vocabularies. An intelligent vocabulary size test (IVST) is developed to precisely measure vocabulary size for any population. The robot testers "take" the IVST, which dynamically generates quizzes with varying levels of difficulty adapted to the estimated tester's vocabulary size in real-time using an artificial neural network (ANN) through iterative learning. The effectiveness of the IVST is factually verified by their visible vocabularies. Additionally, we apply a long short-term memory (LSTM) model to further enhance the method's performance. The proposed method has demonstrated high reliability and effectiveness, achieving accuracies of 98.47% for the IVST and 99.87% for the IVST with LSTM. This novel approach provides a more precise and reliable method for measuring vocabulary size in L2 learners compared to traditional VSTs, offering potential benefits to language learners and educators.

Since the prognosis of patients with pancreatic cancer is very poor and there is a lack of treatment methods, this study is performed to investigate the function of PITX2 in pancreatic stellate cells (PSCs) in the progression of pancreatic cancer. Scientific hypotheses are proposed according to bioinformatics analysis and tissue microarray analysis. Stable knockdown of PITX2 in PSCs is achieved through lentiviral infection. The relative expressions of PITX2, α-SMA, vimentin, CTNNB1, AXIN1 and LEF1 are measured in wild-type PSCs and PITX2-knockdown PSCs. Proliferative capacity is measured by EdU assay. After coculture with PSCs, the proliferation, invasion and migration capacity of pancreatic cancer cells are tested. EMT and Wnt/β-catenin downstream genes of pancreatic cancer cells are investigated to reveal the potential mechanism. Bioinformatics analysis reveals that the PITX2 gene is highly expressed in stromal cells in pancreatic cancer and is correlated with squamous-type PDAC. Analysis of PDAC tissue microarray further demonstrates that high PITX2 level in stromal cells is correlated with poor prognosis in PDAC. After stable knockdown of PITX2 in PSCs, the relative protein levels of α-SMA, vimentin, CTNNB1, AXIN1 and LEF1 are decreased, and the proliferative capacity of PSCs is also decreased. After coculture with PSCs, in which PITX2 expression is downregulated, the proliferation, invasion and migration capacities of pancreatic cancer cells are inhibited. Thus, our results show that PITX2-silenced PSCs inhibit the growth, migration and invasion of pancreatic cancer cells via reduced EMT and Wnt/β-catenin signaling.

A single enzyme active site that catalyzes multiple reactions is a well-established biochemical theme, but how one nuclease site cleaves both DNA strands of a double helix has not been well understood. In analyzing site-specific DNA cleavage by the mammalian RAG1-RAG2 recombinase, which initiates V(D)J recombination, we find that the active site is reconfigured for the two consecutive reactions and the DNA double helix adopts drastically different structures. For initial nicking of the DNA, a locally unwound and unpaired DNA duplex forms a zipper via alternating interstrand base stacking, rather than melting as generally thought. The second strand cleavage and formation of a hairpin-DNA product requires a global scissor-like movement of protein and DNA, delivering the scissile phosphate into the rearranged active site.

The RAG1-RAG2 recombinase (RAG) cleaves DNA to initiate V(D)J recombination, but RAG also belongs to the RNH-type transposase family. To learn how RAG-catalyzed transposition is inhibited in developing lymphocytes, we determined the structure of a DNA-strand transfer complex of mouse RAG at 3.1-Å resolution. The target DNA is a T form (T for transpositional target), which contains two >80° kinks towards the minor groove, only 3 bp apart. RAG2, a late evolutionary addition in V(D)J recombination, appears to enforce the sharp kinks and additional inter-segment twisting in target DNA and thus attenuates unwanted transposition. In contrast to strand transfer complexes of genuine transposases, where severe kinks occur at the integration sites of target DNA and thus prevent the reverse reaction, the sharp kink with RAG is 1 bp away from the integration site. As a result, RAG efficiently catalyzes the disintegration reaction that restores the RSS (donor) and target DNA.

Pancreatic neuroendocrine tumor (pNET) is the second most common malignant tumors of the pancreas. Multiple endocrine neoplasia 1 ( MEN1) is the most frequently mutated gene in pNETs and MEN1-encoded protein, menin, is a scaffold protein that interacts with transcription factors and chromatin-modifying proteins to regulate various signaling pathways. However, the role of MEN1 in lipid metabolism has not been studied in pNETs. In this study, we perform targeted metabolomics analysis and find that MEN1 promotes the generation and oxidation of polyunsaturated fat acids (PUFAs). Meanwhile lipid peroxidation is a hallmark of ferroptosis, and we confirm that MEN1 promotes ferroptosis by inhibiting the activation of mTOR signaling which is the central hub of metabolism. We show that stearoyl-coA desaturase (SCD1) is the downstream of MEN1-mTOR signaling and oleic acid (OA), a metabolite of SCD1, recues the lipid peroxidation caused by MEN1 overexpression. The negative correlation between MEN1 and SCD1 is further verified in clinical specimens. Furthermore, we find that BON-1 and QGP-1 cells with MEN1 overexpression are more sensitive to everolimus, a widely used drug in pNETs that targets mTOR signaling. In addition, combined use everolimus with ferroptosis inducer, RSL3, possesses a more powerful ability to kill cells, which may provide a new strategy for the comprehensive therapy of pNETs.

ERK1/2 are essential proteins mediating mitogen-activated protein kinase signaling downstream of RAS in pancreatic adenocarcinoma (PDAC). Our previous study reveals that ARF6 plays a positive regulatory role in ERK1/2 pathway in a feedback loop manner. A significant part of the literature on ARF6 has emphasized its oncogenic effect as an essential downstream molecule of ERK1/2, and no research has been done on the regulation mechanisms of the feedback loop between ARF6 and the ERK1/2 signaling pathway. In the present study, we explore the gene network downstream of ARF6 and find that DUSP6 may be the critical signal molecule in the positive feedback loop between ARF6 and ERK1/2. Specifically, to elucidate the negative correlations between ARF6 and DUSP6 in pancreatic cancer, we examine their expressions in pancreatic cancer tissues by immunohistochemical staining. Then the impact of DUSP6 on the proliferation and apoptosis of PDAC cells are investigated by gain-of-function and loss-of-function approaches. Mechanism explorations uncover that ARF6 suppresses the expression of DUSP6, which is responsible for the dephosphorylation of ERK1/2. Altogether, these results indicate that DUSP6 plays a tumor-suppressive role and acts as an intermediate molecule between ARF6 and ERK1/2 in PDAC cells, thereby forming a positive feedback loop.