Prognostic significance of serum fucosylated pro-haptoglobin in advanced renal cell carcinoma patients treated with immune checkpoint inhibitors.

With the widespread use of immune checkpoint inhibitors (ICIs), identifying predictive biomarkers is critical. Recently, serum fucosylated haptoglobin (Fuc-Hp) was thought to play an important role in tumour immunity in several types of cancer. Therefore, evaluating serum Fuc-Hp in the peripheral blood can potentially identify non-invasive predictive biomarkers for the clinical efficacy of ICIs. In this study, 31 patients with advanced renal cell carcinoma (RCC) treated with nivolumab were enrolled and defined as responders or non-responders according to RECIST criteria. Serum samples were collected before and 1 month after treatment initiation, and an ELISA assay was performed using Aleuria Aurantia Lectin (AAL) and 10-7G monoclonal antibodies that recognise Fuc-mature Hp (Fuc-mHp) and Fuc-pro Hp (Fuc-pHp), respectively. We first measured AAL-haptoglobin (Fuc-mHp) and total haptoglobin levels before nivolumab and found that neither value could predict the clinical response. Notably, serum 10-7G levels were significantly lower in the responder group (p = 0.035). We also confirmed the use of serum 10-7G levels for predicting progressive disease after nivolumab (area under the curve, 0.816). Accordingly, low 10-7G levels were significantly correlated with better progression-free survival (p = 0.041). In conclusion, serum Fuc-pHp analysis may identify patients with advanced RCC who benefit from ICIs.

Prohaptoglobin is a possible prognostic biomarker for colorectal cancer.

BACKGROUND AND AIMS: Fucosylated haptoglobin is a novel glycan biomarker for colorectal and other cancers, while the significance of its precursor, prohaptoglobin (proHp), remains to be elucidated. In this study, we investigated whether proHp can be a colorectal cancer (CRC) biomarker and the biological functions of proHp in CRC using 10-7G, a monoclonal antibody recently developed in our laboratory. MATERIALS AND METHODS: Serum proHp level in 74 patients with CRC was semi-quantified by western blotting, and 5-year recurrence-free survival and overall survival were analyzed for groups stratified by proHp status (high vs. low). We also performed immunohistochemical analyses of 17 CRC tissue sections using 10-7G mAb. The biological functions of proHp were evaluated by overexpressing proHp in CRC cell lines. RESULTS: Serum proHp correlated with the clinical stage and poorer prognosis of CRC. In the primary CRC sections, immune cells were stained positive for 10-7G in ∼50% of the cases. Overexpression of proHp in HCT116 human CRC cells induced epithelial-mesenchymal transition-like changes and promoted cell migration in CRC cells. CONCLUSION: We provide evidence for the first time that proHp has potential as a prognostic biomarker for CRC and demonstrated specific biological activities of proHp.

CKAP4 is a potential exosomal biomarker and therapeutic target for lung cancer.

Background: Globally, lung cancer causes the most cancer death. While molecular therapy progress, including epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs), has provided remarkable therapeutic effects, some patients remain resistant to these therapies and therefore new target development is required. Cytoskeleton-associated membrane protein 4 (CKAP4) is a receptor of the secretory protein Dickkopf-1 (DKK1) and the binding of DKK1 to CKAP4 promotes tumor growth via Ak strain transforming (AKT) activation. We investigated if CKAP4 functions as a diagnostic biomarker and molecular therapeutic target for lung cancer. Methods: CKAP4 secretion with exosomes from lung cancer cells and the effect of CKAP4 palmitoylation on its trafficking to the exosomes were examined. Serum CKAP4 levels were measured in mouse xenograft models, and 92 lung cancer patients and age- and sex-matched healthy controls (HCs). The lung cancer tissues were immunohistochemically stained for DKK1 and CKAP4, and their correlation with prognosis and serum CKAP4 levels were investigated. Roles of CKAP4 in the lung cancer cell proliferation were examined, and the effects of the combination of an anti-CKAP4 antibody and osimertinib, a third generation TKI, on anti-tumor activity were tested using in vitro and in vivo experiments. Results: CKAP4 was released from lung cancer cells with exosomes, and its trafficking to exosomes was regulated by palmitoylation. CKAP4 was detected in sera from mice inoculated with lung cancer cells overexpressing CKAP4. In 92 lung cancer patients, positive DKK1 and CKAP4 expression patients showed worse prognoses. Serum CKAP4 positivity was higher in lung cancer patients than in HCs. After surgical operation, serum CKAP4 levels were decreased. CKAP4 overexpression in lung cancer cells promoted in vitro cell proliferation and in vivo subcutaneous tumor growth, which were inhibited by an anti-CKAP4 antibody. Moreover, treatment with this antibody or osimertinib, a third generation TKI, inhibited AKT activity, sphere formation, and xenograft tumor growth in lung cancer cells harboring EGFR mutations and expressing both DKK1 and CKAP4, while their combination showed stronger inhibition. Conclusions: CKAP4 may represent a novel biomarker and molecular target for lung cancer, and combination therapy with an anti-CKAP4 antibody and osimertinib could provide a new lung cancer therapeutic strategy.

Twin research shows glycan changes are more susceptible to environmental factors than their carrier glycoproteins.

Changes in protein glycosylation are clinically used as biomarkers. In the present study, we employed a twin cohort to investigate the contributions of genetic and environmental factors to glycan modifications of glycoproteins. Mac-2 binding protein (Mac-2 bp), haptoglobin (Hp), and their glycosylated forms are liver fibrosis and cancer biomarkers. Sera from 107 twin pairs without clinical information were used as a training cohort for the Mac-2 bp and Mac-2 bp glycosylation isomer (M2BPGi) assay. As a validation cohort, 22 twin pairs were enrolled in the study. For each twin pair, one twin was diagnosed with liver or pancreatic disease. For the training cohort, the correlation ratios of serum Mac-2 bp and M2BPGi levels in twin sera with random sequences were 0.30 and 0.018, respectively. The correlation ratios between twin pairs in the validation cohort for serum Mac-2 bp and M2BPGi levels were 0.75 and 0.35, respectively. In contrast, correlation ratios of serum Hp and fucosylated haptoglobin (Fuc-Hp) levels between twin sera with liver and pancreatic disease were 0.49 and 0.16, respectively. Although serum protein levels of glycoproteins are susceptible to genetic factors, characteristic glycan changes of these glycoproteins are more susceptible to environmental factors, including liver and pancreatic disease.

Transcription factor SP1 regulates haptoglobin fucosylation via induction of GDP-fucose transporter 1 in the hepatoma cell line HepG2.

Fucosylation is involved in cancer and inflammation, and several fucosylated proteins, such as AFP-L3 for hepatocellular carcinoma, are used as cancer biomarkers. We previously reported an increase in serum fucosylated haptoglobin (Fuc-Hp) as a biomarker for several cancers, including pancreatic and colon cancer and hepatocellular carcinoma. The regulation of fucosylated protein production is a complex cellular process involving various fucosylation regulatory genes. In this report, we investigated the molecular mechanisms regulating Fuc-Hp production in cytokine-treated hepatoma cells using a partial least squares (PLS) regression model. We found that SLC35C1, which encodes GDP-fucose transporter 1 (GFT1), is the most responsible factor for Fuc-Hp production among various fucosylation regulatory genes. Furthermore, the transcription factor SP1 was essential in regulating SLC35C1 expression. We also found that an SP1 inhibitor was able to suppress Fuc-Hp production without affecting total Hp levels. Taken together, Fuc-Hp production was regulated by SP1 via induction of GFT1 in the hepatoma cell line HepG2.

Serum Mac-2 binding protein level predicts the development of liver-related events and colorectal cancer in patients with NAFLD.

We previously demonstrated that Mac-2 binding protein (M2BP) is a useful biomarker for nonalcoholic fatty liver disease (NAFLD), particularly NAFLD fibrosis prediction. In the present study, we investigated the prognostic value of M2BP in patients with NAFLD. A total of 506 patients with biopsy-confirmed NAFLD from 2002 to 2013 were enrolled in this study in Japan. Three hundred fifty-three of these patients with NAFLD were available for follow-up for more than 100 days and showed no liver-related events at the time of entry. Liver-related events were defined as hepatocellular carcinoma (HCC), decompensation, and gastroesophageal varices with variceal treatment. The mean follow-up duration of all the subjects was 2716 ± 1621 days (102-7483 days). Eighteen patients developed new liver-related events (HCC, 8; decompensation, 11; varices, 8). Nine patients developed cardiovascular disease (CVD), and 24 patients developed new cancers in other organs. The median serum M2BP level was 1.603 µg/mL, and we divided our cohort into two groups according to the serum M2BP level: M2BP low group (M2BP Low) and M2BP high group (M2BP Hi). The incidence of HCC was significantly higher in M2BP Hi (n = 8) than in M2BP Low (n = 0). The incidence of liver-related events was significantly higher in M2BP Hi (n = 16) than in M2BP Low (n = 2). The incidences of death, CVD events, and cancer in other organs were not different between the groups. Interestingly, the incidence of colorectal cancer was significantly higher in M2BP Hi (n = 5) than in M2BP Low (n = 0). Conclusion: M2BP is a useful biomarker to predict liver-related events, particularly HCC. Additionally, M2BP is a potential predictive biomarker of colorectal cancer development.

Identification of fucosylated haptoglobin-producing cells in pancreatic cancer tissue and its molecular mechanism.

Fucosylated haptoglobin is a well-established glyco-biomarker of pancreatic cancer. We recently established a novel anti-glycan antibody (10-7G mAb) that specifically recognizes fucosylated haptoglobins, including prohaptoglobin (proHpt). Serum concentrations of the 10-7G value, as measured by ELISA, were increased in patients with pancreatic cancer relative to the healthy controls. However, it is currently unknown which specific tissue or cell type produces fucosylated haptoglobins or proHpt. In the present study, we performed immunohistochemical (IHC) and ELISA analyses of pancreatic cancer tissue samples using 10-7G mAb. Among 21 pancreatic tissue sections, only 1 showed direct staining of pancreatic cells with the 10-7G mAb. However, 12 of the 21 sections stained positively for immune cells. Although there was no significant difference in the 10-7G expression between the positive and negative staining IHC groups, the median value of serum 10-7G was slightly higher in IHC-positive cases. Among many assayed leukemic cell lines, differentiated THP-1 cells (a human acute monocytic leukemia cell line) were found to have the highest levels of proHpt, per Western blot using 10-7G mAb. Interestingly, production of proHpt in vitro was dramatically increased under either hypoxic conditions or after IL-6 treatment. These results suggest that immune cells, including macrophages, in the pancreatic tissue microenvironment produce fucosylated haptoglobin and proHpt. Thus, fucosylated haptoglobins can be detected by the 10-7G mAb and may be a promising biomarker for pancreatic cancer.

Detection of fucosylated haptoglobin using the 10-7G antibody as a biomarker for evaluating endoscopic remission in ulcerative colitis.

BACKGROUND: Inflammatory bowel disease (IBD) is a chronic, relapsing inflammation of the digestive tract. Although fecal and serum biomarkers have been extremely important and supportive for monitoring of IBD, their low sensitivity and high variability characteristics limit clinical efficacy. Thus, the establishment of better biomarkers is expected. Fucosylation is one of the most important glycosylation modifications of proteins. Fucosylated haptoglobin (Fuc-Hpt) is used as a biomarker for several cancers and inflammation-related diseases. We recently established a novel glycan monoclonal antibody (mAb), designated 10-7G, which recognizes Fuc-Hpt. We developed an enzyme-linked immunosorbent assay (ELISA) to measure serum levels of Fuc-Hpt (10-7G values). AIM: To investigate the usefulness of the serum 10-7G values as a potential biomarker for monitoring disease activity in IBD. METHODS: This was a case control study. Intestinal tissues of IBD patients (n = 10) were examined immunohistochemically using the 10-7G mAb. We determined 10-7G values using serum from patients with ulcerative colitis (UC, n = 110), Crohn's disease (n = 45), acute enteritis (AE, n = 11), and healthy volunteers (HVs) who exhibited normal (n = 20) or high (n = 79) C-reactive protein (CRP) levels at medical check-up. We investigated the correlation between the 10-7G value and various clinical parameters of IBD patients by correlation analysis. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the usefulness of the 10-7G values as a biomarker for clinical and endoscopic remission of UC compared to conventional serum biomarkers. RESULTS: In the immunohistochemical analysis, positive 10-7G mAb staining was observed in lymphocytes infiltrating into inflammatory sites of the mucosal layer and lymphoid follicles. The 10-7G values were significantly higher in patients with IBD (P < 0.001) and AE (P < 0.05) compared with HVs. In addition, 10-7G values were correlated with clinical examination parameters related to inflammation in patients with UC, particularly the CRP level (rs = 0.525, P = 0.003) and clinical activity index score (rs = 0.435, P = 0.038). However, there was no correlation between 10-7G values and CRP in HVs with high CRP levels, suggesting that the 10-7G values is not the same as a general inflammation biomarker. ROC curve analysis showed that area under the curve (AUC) value of 10-7G values for the diagnosis of endoscopic remission was higher than other biomarkers (AUC value = 0.699). CONCLUSION: The serum 10-7G value is a novel biomarker for evaluating intestinal inflammation and endoscopic mucosal healing in UC.

Serum Mac-2 Binding Protein Levels Associate with Metabolic Parameters and Predict Liver Fibrosis Progression in Subjects with Fatty Liver Disease: A 7-Year Longitudinal Study.

Background: Mac-2 binding protein (M2BP) is a highly glycosylated secreted glycoprotein that is involved in immune defense and regulation. Our cross-sectional studies indicated that serum M2BP was a useful liver fibrosis biomarker for nonalcoholic fatty liver disease (NAFLD). In this study, we conducted a 7-year longitudinal study to investigate the significance of serum M2BP levels (baseline and at 7-year follow-up) and their relationships with other metabolic parameters of fatty liver disease. Methods: We enrolled 715 study subjects (521 male and 194 female) during health examinations. Study subjects received blood sampling tests and abdominal ultrasound tests at baseline and follow-up. Results: Univariate analyses demonstrated that serum M2BP levels were significantly correlated with various parameters related to metabolic risk (body mass index (BMI), systolic blood pressure, triglyceride, high density lipoprotein (HDL)-cholesterol) and metabolic syndrome diseases (obesity, hypertension, dyslipidemia, diabetes mellitus, fatty liver (FL)). Multiple logistic regression analyses demonstrated that BMI and FL were independent determinants for serum M2BP levels. Baseline serum M2BP levels were significant independent determinants for changes in platelet count, Fibrosis-4 (FIB4) index, and NAFLD fibrosis score. Higher serum M2BP levels (>1.80 µg/mL) strongly correlated with changes in the FIB4-index. Conclusions: The results of this study suggest that changes in serum M2BP levels reflect changes in specific metabolic disease-related parameters, and baseline serum M2BP levels could predict changes in liver fibrosis.

Loss of core fucosylation reduces low-density lipoprotein receptor expression in hepatocytes by inducing PCSK9 production.

Fucosylation is a type of glycosylation, a form of post-transcriptional regulation of proteins, involved in cancer and inflammation. It involves the attachment of a fucose residue to N-glycans, O-glycans, and glycolipids, which is catalyzed by a family of enzymes called fucosyltransferases (Futs). Among the many Futs, α-1,6-fucosyltransferase (Fut8) is the only enzyme that produces α-1,6-fucosylated oligosaccharides (core fucose). In the human liver, the expression and activity of Fut8 are frequently elevated during progression of chronic liver diseases. Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a well-known negative regulator of the low-density lipoprotein receptor (LDLR). Here, we found that loss of core fucose in immortalized hepatocytes led to LDLR downregulation through a dramatic induction of PCSK9. We used the immortalized hepatocytes derived from Fut8 knockout mice or a Fut8 knockdown AML12 hepatocyte cell line. Using these cells, we investigated the effects of Fut8 on hepatocyte cholesterol influx. Both cell lines had reduced LDLR protein levels, resulting from marked increases in PCSK9 expression. Intracellular cholesterol levels were significantly lower and LDL cholesterol uptake was suppressed in Fut8-KO cells. Hepatocyte nuclear factor 1α accumulated in nuclei of Fut8-KO hepatocytes, which mediated increases in PCSK9 mRNA expression. Our findings demonstrated that loss of core fucosylation promoted degradation of LDLR and impaired cholesterol uptake, which is a novel mechanism that regulates cholesterol influx, suggesting that Fut8 might be a novel causative gene for familial hypercholesterolemia.

Identification of the epitope of 10-7G glycan antibody to recognize cancer-associated haptoglobin.

We previously identified fucosylated haptoglobin (Fuc-Hpt) as a clinical serum biomarker of pancreatic cancer and established the novel glycan monoclonal antibody (mAb) 10-7G. This antibody recognizes cancer-associated haptoglobin including Fuc-Hpt and the precursor of haptoglobin. Interestingly, Western blot analysis showed that the 10-7G mAb reacts with the haptoglobin α chain, which has no N-glycan potential sites; haptoglobin ß chain has four N-glycan sites. In this study, we identified the epitope for the 10-7G mAb using haptoglobin deletion mutants, as well as inhibition ELISA with recombinant peptides. We illustrated molecular graphics to show a relationship between the epitope and the ß chain. Furthermore, we hypothesized that the 10-7G mAb minimally recognizes normal haptoglobin, but aberrant glycosylation on the ß chain causes conformational changes, enabling the 10-7G mAb to easily access the epitope within the α chain. Because 10-7G values, an enzyme-linked immunosorbent assay-immobilized 10-7G mAb, in patients with pancreatic cancer varied by haptoglobin phenotype, the amount of aberrant glycosylation needed to affect haptoglobin conformation probably depends on haptoglobin phenotype. Taken together, the 10-7G mAb recognized characteristic peptides on the haptoglobin α chain as a result of conformational changes and is a promising tool for diagnosing pancreatic cancer by haptoglobin phenotype.

Establishment and characterization of a fucosylated α-fetoprotein-specific monoclonal antibody: a potential application for clinical research.

The Lens culinaris agglutinin (LCA)-reactive fraction of α-fetoprotein (AFP-L3) is a well-known cancer biomarker for hepatocellular carcinoma (HCC) with very high specificity. Because LCA recognizes only bi-antennary N-glycans with a core fucose, some of fucosylated AFP in HCC patients may not be detected. Then glycan antibodies, which recognize both specific glycan and protein, are desired for glycobiology. Here, we successfully established a novel glycan antibody for fucosylated AFP and demonstrated its potential clinical application. After immunization with a fucosylated AFP peptide, positive screening was performed for fucosylated AFP peptides using solid-phase enzyme-linked immunosorbent assay (ELISA). The newly developed antibody was designated: fucosylated AFP-specific mAb (FasMab). Western blot analysis showed that FasMab reacted with AFP produced by HepG2 cells, but not with AFP produced by α-1,6-fucosyltransferase deficient HepG2 cells. The specific binding of FasMab to fucosylated AFP was confirmed with ELISA as well as western blot analysis. A preliminary high sensitivity chemiluminescence enzyme immunoassay kit showed increased levels of fucosylated AFP in the sera of patients with HCC, but not in the sera of normal patients, or patients with chronic liver diseases. Thus, the novel glycan antibody, FasMab, is a promising tool to study fucosylated AFP with clinical and basic research applications.

Haptoglobin phenotype is a critical factor in the use of fucosylated haptoglobin for pancreatic cancer diagnosis.

Fucosylation is one of the most important glycosylations involved in cancer and inflammation. Many studies have reported significant increases in serum fucosylated haptoglobin (Fuc-Hpt) in a variety of cancer patients. In this study, we measured Fuc-Hpt using a lectin-antibody enzyme-linked immunosorbent assay (ELISA) or a novel ELISA system that used a glycan antibody for Fuc-Hpt. Hpt is known to be divided into three phenotypes (Hpt1-1, Hpt2-1, and Hpt2-2), depending on its genetic background. Normal levels of serum Hpt are different in each Hpt phenotype and these phenotypes are associated with the incidence of several human diseases. Here, we investigated how Hpt phenotype affected measurements of Fuc-Hpt, using two kinds of ELISA. Interestingly, we found that serum Fuc-Hpt levels were dramatically lower in the Hpt1-1 phenotype for both types of ELISA. For Hpt2-1 and Hpt2-2, we observed significantly increased serum Fuc-Hpt levels in patients with pancreatic cancer. When cases of the Hpt1-1 phenotype were depleted, our receiver operating characteristic (ROC) curve analyses showed that the area under the curve (AUC) value for pancreatic cancer diagnosis increased in each ELISA. Taken together, our results indicate that Hpt phenotype is a critical for the clinical application of Fuc-Hpt as a cancer biomarker.

Establishment of an antibody specific for cancer-associated haptoglobin: a possible implication of clinical investigation.

We previously found that the serum level of fucosylated haptoglobin (Fuc-Hpt) was significantly increased in pancreatic cancer patients. To delineate the mechanism underlying this increase and develop a simple detection method, we set out to generate a monoclonal antibody (mAb) specific for Fuc-Hpt. After multiple screenings by enzyme-linked immunosorbent assay (ELISA), a 10-7G mAb was identified as being highly specific for Fuc-Hpt generated in a cell line as well as for Hpt derived from a pancreatic cancer patient. As a result from affinity chromatography with 10-7G mAb, followed by lectin blot and mass spectrometry analyses, it was found that 10-7G mAb predominantly recognized both Fuc-Hpt and prohaptoglobin (proHpt), which was also fucosylated. In immunohistochemical analyses, hepatocytes surrounding metastasized cancer cells were stained by the 10-7G mAb, but neither the original cancer cells themselves nor normal hepatocytes exhibited positive staining, suggesting that metastasized cancer cells promote Fuc-Hpt production in adjacent hepatocytes. Serum level of Fuc-Hpt determined with newly developed ELISA system using the 10-7G mAb, was increased in patients of pancreatic and colorectal cancer. Interestingly, dramatic increases in Fuc-Hpt levels were observed at the stage IV of colorectal cancer. These results indicate that the 10-7G mAb developed is a promising antibody which recognizes Fuc-Hpt and could be a useful diagnostic tool for detecting liver metastasis of cancer.