We evaluated possible diagnostic and prognostic values of serum midkine in malignant pleural mesothelioma in comparison with those of serum mesothelin, a well-established diagnostic biomarker. Serum mesothelin and midkine levels were determined with an enzyme-linked immunosorbent assay. We examined specimens from 95 Turkish cases with malignant pleural mesothelioma, 56 metastatic cancers to pleura, 27 other types of benign pleural diseases and 20 benign asbestos pleurisy. The cut-off values were 1.5 nmol/L for mesothelin and 421 pg/mL for midkine. Sensitivity and specificity of mesothelin were 51.6 and 71.4%, 51.6 and 85.2%, and 51.6 and 85% for differentiating mesothelioma from metastatic cancers to pleura, other benign pleural diseases and benign asbestos pleurisy, respectively. Sensitivity and specificity of midkine were 61.1 and 41.1%, 61.1 and 48.1%, and 61.1 and 75% to distinguish mesothelioma from metastatic cancers to pleura, other benign pleural diseases and benign asbestos pleurisy, respectively. Combination of both biomarkers did not improve the differential diagnostic efficacy. Mesothelin levels were elevated in the epitheloid type and in the advanced cases, but were not related to the prognosis. In contrast, elevated baseline levels of midkine were independently associated with a poor prognosis of mesothelioma patients after adjusting for the stage, the histological subtypes and treatment schedules (HR = 1.84; 95% CI: 1.09-3.09) (p = 0.022). Serum mesothelin showed moderate sensitivity and high specificity to differentiate malignant pleural mesothelioma from metastatic malignancy to pleura and from benign pleural diseases. In contrast, midkine was a useful marker for predicting prognosis of mesothelioma patients.

Inflammation is closely associated with cerebrovascular diseases, cardiovascular diseases, diabetes, and cancers, and it is accompanied by the development of autoantibodies in the early stage of inflammation-related diseases. Hence, it is meaningful to discover novel antibody biomarkers targeting inflammation-related diseases. In this study, Jumonji C-domain-containing 6 (JMJD6) was identified by the serological identification of antigens through recombinant cDNA expression cloning. In particular, JMJD6 is an antigen recognized in serum IgG from patients with unstable angina pectoris (a cardiovascular disease). Then, the serum antibody levels were examined using an amplified luminescent proximity homogeneous assay-linked immunosorbent assay and a purified recombinant JMJD6 protein as an antigen. We observed elevated levels of serum anti-JMJD6 antibodies (s-JMJD6-Abs) in patients with inflammation-related diseases such as ischemic stroke, acute myocardial infarction (AMI), diabetes mellitus (DM), and cancers (including esophageal cancer, EC; gastric cancer; lung cancer; and mammary cancer), compared with the levels in healthy donors. The s-JMJD6-Ab levels were closely associated with some inflammation indicators, such as C-reactive protein and intima–media thickness (an atherosclerosis index). A better postoperative survival status of patients with EC was observed in the JMJD6-Ab-positive group than in the negative group. An immunohistochemical analysis showed that JMJD6 was highly expressed in the inflamed mucosa of esophageal tissues, esophageal carcinoma tissues, and atherosclerotic plaques. Hence, JMJD6 autoantibodies may reflect inflammation, thereby serving as a potential biomarker for diagnosing specific inflammation-related diseases, including stroke, AMI, DM, and cancers, and for prediction of the prognosis in patients with EC.

The relationship between energy production and cancer is attracting attention. This study aimed to investigate the clinicopathological significance of fumarate hydratase (FH), a tricarboxylic acid cycle enzyme, in gastric cancer using autoantibodies as biomarkers. The study analyzed 116 patients who underwent gastric cancer surgery and 96 healthy controls. Preoperative serum FH autoantibody (s-FH-Ab) titers were analyzed using an immunosorbent assay with an amplified luminescent proximity homogeneous assay. Receiver operating characteristic analysis was used to determine the cutoff s-FH-Ab titer. Clinicopathological factors and prognosis were compared between the high and low s-FH-Ab groups. The s-FH-Ab levels were significantly higher in the gastric cancer group than in the control group (p = 0.01). Levels were elevated even in patients with stage I gastric cancer compared with healthy controls (p = 0.02). A low s-FH-Ab level was significantly associated with distant metastasis (p = 0.01), peritoneal dissemination (p < 0.05), and poor overall survival (p < 0.01). Multivariate analysis revealed that low s-FH-Ab levels were an independent risk factor for poor prognosis (p < 0.01). Therefore, s-FH-Ab levels may be a useful biomarker for early diagnosis and the prediction of prognosis in patients with gastric cancer.

Given that esophageal cancer is highly malignant, the discovery of novel prognostic markers is eagerly awaited. We performed serological identification of antigens by recombinant cDNA expression cloning (SEREX) and identified SKI proto‐oncogene protein and transmembrane p24 trafficking protein 5 (TMED5) as antigens recognized by serum IgG antibodies in patients with esophageal carcinoma. SKI and TMED5 proteins were expressed in Escherichia coli, purified by affinity chromatography, and used as antigens. The serum anti‐SKI antibody (s‐SKI‐Ab) and anti‐TMED5 antibody (s‐TMED5‐Ab) levels were significantly higher in 192 patients with esophageal carcinoma than in 96 healthy donors. The presence of s‐SKI‐Abs and s‐TMED5‐Abs in the patients' sera was confirmed by western blotting. Immunohistochemical staining showed that the TMED5 protein was highly expressed in the cytoplasm and nuclear compartments of the esophageal squamous cell carcinoma tissues, whereas the SKI protein was localized predominantly in the nuclei. Regarding the overall survival in 91 patients who underwent radical surgery, the s‐SKI‐Ab‐positive and s‐TMED5‐Ab‐negative statuses were significantly associated with a favorable prognosis. Additionally, the combination of s‐SKI‐Ab‐positive and s‐TMED5‐Ab‐negative cases showed an even clearer difference in overall survival as compared with that of s‐SKI‐Ab‐negative and s‐TMED5‐Ab‐positive cases. The s‐SKI‐Ab and s‐TMED5‐Ab biomarkers are useful for diagnosing esophageal carcinoma and distinguishing between favorable and poor prognoses.

Atherosclerosis is associated with vascular diseases, diabetes, and cancers. The Jumonji C-domain-containing 6 (JMJD6) gene plays an important role in diverse biological processes. In addition, autoantibodies are reportedly useful in the early diagnosis and treatment of many diseases. Here, JMJD6 was identified by serological identification of antigens by recombinant cDNA expression cloning as an antigen recognized by serum IgG from patients with unstable angina pectoris. Then, we performed amplified luminescent proximity homogeneous assay-linked immunosorbent assay using purified recombinant antigens and found elevated levels of serum anti-JMJD6 antibodies (s-JMJD6-Abs) in patients with atherosclerosis-related diseases including ischemic stroke, acute myocardial infarction (AMI), diabetes mellitus (DM), and cancers including esophageal cancer (EC), gastric cancer, lung cancer, and mammary cancer, compared with those in healthy donors. The s-JMJD6-Ab levels were closely associated with hypertension, habitual smoking, and the intima-media thickness, an atherosclerosis index. The better postoperative survival status was shown in patients with EC from the JMJD6-Ab-positive group than the negative group, especially from JMJD6-Ab-positive/PD-L1-negative group and JMJD6-Ab-positive/p53-Ab-negative group than JMJD6-Ab-negative/PD-L1-positive group and JMJD6-Ab-negative/p53-Ab-positive group, respectively. Hence, JMJD6 autoantibodies may reflect atherosclerosis severity, thereby a potential biomarker for atherosclerosis-related diseases including ischemic stroke, AMI, DM, and cancers and for predicting EC prognosis.