This study aims to evaluate the diagnostic value of human serum cysteine protease inhibitors (cystatin 4 [CST4]) in colorectal cancer (CRC) patients.
A total of 291 patients who were admitted to Zhuzhou Central Hospital for colonoscopy from January 2020 to December 2021 and met the inclusion criteria were selected. Serum samples of the patients were collected, and CST4 was detected by double-antibody sandwich enzyme-linked immunosorbent assay. Simultaneously, CEA and CA19-9 were detected, and the patients were divided into the CRC group, benign lesion group, and healthy control group. An attempt was made to construct a CRC prediction model including CST4 and draw a subject working characteristic curve as a diagnostic threshold for CRC prediction, and evaluate the diagnostic efficacy of the above indicators. At the same time, the expression analysis of CST4, CEA, and CA19-9 was verified by combining the data of CRC in the Tumor Genome Atlas (TCGA).
In this study, the levels of serum CST4, CEA, and CA19-9 in the CRC group were higher than those in the colorectal benign lesion group and healthy control group, with statistical significance (P < .001). The analysis results of the receiver operating characteristic curve showed that the area under the receiver operator characteristic curve (AUC) of CST4 was 0.7739, which was obviously larger than the AUC of CA19-9 and CEA. CRC data from the TCGA expression database showed that CST4 expression and CEA expression were higher in CRC patients than in normal samples. The combined model based on CST4 was successfully constructed, and the AUC for predicting the occurrence of CRC was 0.7851.
CST4 is a novel and improved diagnostic marker for CRC. The combined model based on CST4 has a certain potential value in terms of predicting the occurrence of intestinal cancer.

OBJECTIVE: In this study, the abundance of the protective salivary proteins lysozyme, lactoferrin, and cystatin S was quantified in the in situ formed pellicle of caries-free and caries-active children to determine whether they may be possible biomarkers for caries.
METHODS: Pellicle formation was performed in situ for 10 min on ceramic specimens from the oral cavity of children (5-8 years) with caries (n = 17) and without evidence of caries (n = 17). Additionally, unstimulated saliva was collected. Levels of lysozyme, lactoferrin, and cystatin S were measured in desorbed pellicle eluates and saliva using ELISA.
RESULTS: No statistically significant differences were found in the occurrence of cystatin S and lysozyme in saliva and pellicle between caries-active and caries-free children. However, significantly higher amounts of lactoferrin were detected in the pellicle of caries-active children.
CONCLUSIONS: The protective salivary protein lactoferrin may be a biomarker for caries susceptibility in children.

BACKGROUND: Early diagnosis is of great significance for the prognosis of colorectal cancer (CRC) patients. Either serum cystatin S (CST4) or DR-70 has been demonstrated to play an important role on the diagnosis for CRC, however, the diagnostic performances of individual and combined detection of serum CST4 and DR-70 for the patients with CRC at early stage have still not been clarified up to now.
METHODS: The performances of CST4 and DR-70 were evaluated by ELISA for the early diagnosis of CRC with 288 retrospective serum samples. A training set comprised of 64 patients with early CRC, 64 patients with colorectal benign lesions (CBL), and 64 healthy controls (HC) was used to develop the predictive model for early CRC. And then, data obtained from an independent validation set was applied to evaluate and validate the predictive model.
RESULTS: In the training set, the levels of CST4 and DR-70 in early CRC group were significantly higher than that in CBL group/HC group (P < 0.001); serum CST4 presented the AUC of 0.927 for early CRC patients, with 57.8% sensitivity at 95.3% specificity; serum DR-70 presented the AUC of 0.725 for early CRC patients, with 29.7% sensitivity at 95.3% specificity; combination of serum CST4 and DR-70 presented the AUC of 0.941, with 68.8% sensitivity at 93.8% specificity. Additionally, the combination of serum CST4 and DR-70 showed the AUC of 0.940 for early CRC patients, with 71.9 % sensitivity at 89.1% specificity in the validation set.
CONCLUSIONS: Both serum CST4 and DR-70 present the diagnostic value for the patients with early CRC, and the combination of CST4 and DR-70 contributes to the further improvement of the early diagnosis for CRC.

Early childhood caries is the most common infectious disease in childhood, with a high prevalence in developing countries. The assessment of the variables that influence early childhood caries as well as its pathophysiology leads to improved control of this disease. Cystatin S, as one of the salivary proteins, has an essential role in pellicle formation, tooth re-mineralization, and protection. The present study aims to assess salivary cystatin S levels and demographic data in early childhood caries in comparison with caries-free ones using statistical analysis and machine learning methods.
A cross-sectional, case-control study was undertaken on 20 cases of early childhood caries and 20 caries-free children as a control. Unstimulated whole saliva samples were collected by suction. Cystatin S concentrations in samples were determined using human cystatin S ELISA kit. The checklist was collected from participants about demographic characteristics, oral health status, and dietary habits by interviewing parents. Regression and receiver operating characteristic (ROC) curve analysis were done to evaluate the potential role of cystatin S salivary level and demographic using statistical analysis and machine learning.
The mean value of salivary cystatin S concentration in the early childhood caries group was 191.55 ± 81.90 (ng/ml) and in the caries-free group was 370.06 ± 128.87 (ng/ml). T-test analysis showed a statistically significant difference between early childhood caries and caries-free groups in salivary cystatin S levels (p = 0.032). Investigation of the area under the curve (AUC) and accuracy of the ROC curve revealed that the logistic regression model based on salivary cystatin S levels and birth weight had the most and acceptable potential for discriminating of early childhood caries from caries-free controls. Furthermore, using salivary cystatin S levels enhanced the capability of machine learning methods to differentiate early childhood caries from caries-free controls.
Salivary cystatin S levels in caries-free children were higher than the children with early childhood caries. Results of the present study suggest that considering clinical examination, demographic and socioeconomic factors, along with the salivary cystatin S levels, could be usefull for early diagnosis ofearly childhood caries in high-risk children; furthermore, cystatin S is a protective factor against dental caries.

UNASSIGNED: Members of the cystatin family have increasingly been proven to be involved in several tumors, including gastric cancer (GC) and colorectal cancer (CRC). Cystatin S (CST4) was found to be upregulated at the gene expression level in GC cells, making it a potential novel biomarker for the early diagnosis of gastrointestinal cancer.
UNASSIGNED: Quantitative real-time polymerase chain reaction and Western blotting analysis were used to explore CST4 expression in gastrointestinal cancer tissues and cell lines. We purified CST4 recombinant protein and generated anti-CST4 monoclonal antibodies to develop an antibody-sandwich enzyme-linked immunosorbent assay (ELISA) analysis system for blood CST4 detection. The performance and clinical efficacy of the detection method were evaluated using a training set and validation set, respectively.
UNASSIGNED: According to the quantitative real-time polymerase chain reaction and Western blotting results, CST4-mRNA expression and protein expression were upregulated in gastrointestinal cancer tissues and cell lines. The ELISA detection system for CST4 showed significantly better sensitivities of 69.0% and 69.0% and specificities of 85.6% and 83.6% for GC and CRC, respectively, than other common clinical biomarkers, carcinoembryonic antigen, CA19-9, CA125, and CA72-4. Clinical verification experiments using GC and CRC validation sets also found distinguishable CST4 median concentrations (177.7 pg·mL-1 and 174.2 pg·mL-1 respectively) and high positive detection rates (72.3% and 88.4% respectively), further confirming the specificity and sensitivity of this method.
UNASSIGNED: We validated the overexpression of CST4 in gastrointestinal cancer tissues and cell lines and developed an antibody-sandwich ELISA analysis system for blood CST4 detection, which exhibited high specificity and sensitivity. Novel blood biomarkers of CST4 have enormous potential in terms of clinical diagnostic value in GC and CRC.

Salivary cystatin S is a defence protein mainly produced by submandibular glands and involved in innate oral immunity. This study aimed to verify whether cystatin S was diversely expressed in different disease subsets of primary Sjogren\'s syndrome (pSS) patients, defined on the basis of salivary flow [unstimulated salivary flow rate (USFR)], minor salivary gland (MSG) focus score and submandibular gland ultrasonography abnormalities. We also evaluated miR-126 and miR-335-5p expression in MSG biopsies to verify whether an aberrant regulation of cystatin S at the glandular level may influence its salivary expression.
Forty pSS patients and 20 sex- and age-matched healthy volunteers were included. Salivary cystatin S levels were assessed by western blot analysis using a stain-free technology. The expression of miR-126, miR-335-5p and cystatin S was assessed by quantitative PCR in 15 MSG biopsies differing for USFR and MSG focus score.
We found that salivary cystatin S was significantly decreased in pSS patients vs healthy volunteers ( P = 0.000), especially in those with hyposalivation. A positive correlation was observed between cystatin S and USFR ( r = 0.75, P = 0.01). Salivary cystatin S was also significantly reduced in patients with a submandibular gland ultrasonography score ⩾2. The expression levels of miR-126 and miR-335-5P increased in inverse proportion with USFR. The mRNA of cystatin S did not change significantly, suggesting post-transcriptional regulation.
Cystatin S emerged as a promising biomarker for pSS, strongly correlated with glandular dysfunction. An upregulation of miR-126 and miR-335-5P might be implicated in its expression.