sTRA Glycan Research Articles

Detection of Chemotherapy-resistant Pancreatic Cancer Using a Glycan Biomarker, sTRA.

A subset of pancreatic ductal adenocarcinomas (PDACs) is highly resistant to systemic chemotherapy, but no markers are available in clinical settings to identify this subset. We hypothesized that a glycan biomarker for PDACs called sialylated tumor-related antigen (sTRA) could be used for this purpose. We tested for differences between PDACs classified by glycan expression in multiple systems: sets of cell lines, organoids, and isogenic cell lines; primary tumors; and blood plasma from human subjects. The sTRA-expressing models tended to have stem-like gene expression and the capacity for mesenchymal differentiation, in contrast to the nonexpressing models. The sTRA cell lines also had significantly increased resistance to seven different chemotherapeutics commonly used against pancreatic cancer. Patients with primary tumors that were positive for a gene expression classifier for sTRA received no statistically significant benefit from adjuvant chemotherapy, in contrast to those negative for the signature. In another cohort, based on direct measurements of sTRA in tissue microarrays, the patients who were high in sTRA again had no statistically significant benefit from adjuvant chemotherapy. Furthermore, a blood plasma test for the sTRA glycan identified the PDACs that showed rapid relapse following neoadjuvant chemotherapy. This research demonstrates that a glycan biomarker could have value to detect chemotherapy-resistant PDAC in clinical settings. This capability could aid in the development of stratified treatment plans and facilitate biomarker-guided trials targeting resistant PDAC.

Abstract PR-010: Blinded and meta-analysis validation of an improved serological test for PDAC using the combination of CA19-9 and the sTRA glycan

Abstract Improvements in the clinical outcomes of pancreatic cancer patients may be achieved if physicians could identify the disease earlier. Recent studies demonstrated the promise of a biomarker panel is a simple combination between CA19-9 and another marker called sTRA, so named because it detects the sialylated version of the glycan bound by the TRA-1-60 (tumor-related antigen) antibody. The sTRA glycan is structurally related to the CA19-9 antigen and is produced by a different subtype of cancer cells than make CA19-9. We hypothesized that, among patients with PDAC, different patients have plasma elevations in CA19-9 than have plasma elevations in sTRA, and that as a result, a panel comprising the two markers detects more cancers at high specificity (low false-positive rate) than either marker alone. To test this hypothesis, we analyzed the relationships and biomarker performance of CA19-9 and sTRA across seven different datasets, encompassing 729 patient samples collected from four different clinical centers. We tested whether unique elevation occurred for each marker in each dataset, and whether the combination of markers performed better than then individual markers for distinguishing PDAC from healthy subjects and from benign pancreatic disease. We observed complementary elevations of sTRA or CA19-9 in the PDAC patients in each dataset. A two-marker panel composed of CA19-9 and sTRA and a three-marker panel composed of CA19-9 and two versions of the sTRA immunoassay gave statistically significant improvements over CA19-9 across the datasets for distinguishing PDAC from non-PDAC samples (healthy, chronic pancreatitis, pancreatic cyst, and biliary stricture/stones). At 95% specificity, sensitivity was improved from 36-55% across datasets for CA19-9 to 61-67% across datasets for the three-marker panel. The lead panel further showed 95% specificity and 61% sensitivity using blinded calls on another validation set (N = 340). This analysis serves as broad support for an improved serological test for PDAC using the combination of CA19-9 and sTRA. In light of this level of validation, the lead panel could be considered the most promising panel from the currently available information. If further validated using clinical assays, it may be good enough for surveillance among patients with increased risk for PDAC, in combination with follow-up modalities to establish diagnosis. Citation Format: Ying Liu, Ben Staal, Daniel Barnett, Zonglin He, Chongfeng Gao, Mark Hurd, Pamela Bartlett, Aatur Singhi, J. Bradley Morrow, Gregory Cote, Anirban Maitra, Ying Huang, Randall Brand, Brian Haab. Blinded and meta-analysis validation of an improved serological test for PDAC using the combination of CA19-9 and the sTRA glycan [abstract]. In: Proceedings of the AACR Virtual Special Conference on Pancreatic Cancer; 2020 Sep 29-30. Philadelphia (PA): AACR; Cancer Res 2020;80(22 Suppl):Abstract nr PR-010.

Abstract PO-002: Detection of chemotherapy-resistant pancreatic cancer using a glycan Biomarker

Abstract A subset of pancreatic ductal adenocarcinomas (PDACs) is highly resistant to systemic chemotherapy, but no markers are available in clinical settings to identify this subset. In this study, we evaluate the role of sTRA, a glycan biomarker for PDAC, in predicting chemotherapeutic responses. We tested the correlation between chemosensitivity and glycan expression in PDACs in multiple systems including sets of cell lines, organoids, and isogenic cell lines; primary tumors; and blood plasma from human subjects. The sTRA-expressing models tended to have stem-like gene expression and the capacity for mesenchymal differentiation, in contrast to the non-expressing models. The sTRA cell lines also had significantly increased resistance to seven different chemotherapeutics commonly used against pancreatic cancer. Patients with primary tumors that were positive for a gene-expression classifier for sTRA received no statistically significant benefit from adjuvant chemotherapy, in contrast to those negative for the signature. In another cohort, based on direct measurements of sTRA in tissue microarrays, the patients who were high in sTRA again had no statistically significant benefit from adjuvant chemotherapy. Furthermore, a blood-plasma test for the sTRA glycan identified the PDACs that showed rapid relapse following neoadjuvant chemotherapy. This research demonstrates that a glycan biomarker could have value to detect chemotherapy resistant PDAC in clinical settings. This capability could aid in the development of stratified treatment plans and facilitate biomarker-guided trials targeting resistant PDAC. Citation Format: ChongFeng Gao, Luke Wisniewski, Ying Liu, Ben Staal, Ian Beddows, Dennis Plenker, Mohammed Aldakkak, Johnathan Hall, Daniel Barnett, Mirna Kheir Gouda, Peter Allen, Richard Drake, Amer Zureikat, Ying Huang, Douglas Evans, Aatur Singhi, Randall Brand, David Tuveson, Susan Tsai, Brian Haab. Detection of chemotherapy-resistant pancreatic cancer using a glycan Biomarker [abstract]. In: Proceedings of the AACR Virtual Special Conference on Pancreatic Cancer; 2020 Sep 29-30. Philadelphia (PA): AACR; Cancer Res 2020;80(22 Suppl):Abstract nr PO-002.

Abstract 3147A: The use of the sTRA glycan for predicting responses to neoadjuvant therapy in patients with pancreatic ductal adenocarcinoma

Abstract The sTRA glycan has been validated as a serological and cell-surface biomarker of pancreatic ductal adenocarcinoma (PDAC). In previous work, a biomarker panel using sTRA and CA19-9 performed significantly better than CA19-9 for distinguishing PDAC from benign diseases of the pancreas; here we explored whether the subgroup identified by sTRA has a different prognosis than other subgroups. We examined the plasma levels of sTRA and CA19-9 in two cohorts of patients with resectable or borderline-resectable PDAC. In each cohort, two samples per patient were collected: one prior to any therapy, and another after neoadjuvant therapy but before surgery. In the first cohort (n = 54), the ratio of post-therapy to pre-therapy plasma sTRA was statistically higher (p < 0.05, student’s t-test using logged ratios) in patients with poor response, as assessed by surgical pathology. CA19-9 had higher ratios in a subset of the poor-response subjects but without statistical significance. In the second cohort (n = 75), the pre-treatment and post-treatment levels of sTRA were significantly higher (p < 0.01, Wilcoxon Rank-Sum test) in patients with shorter survival (<2 years). In contrast, CA19-9 did not show statistical significance in the pre-treatment or post-treatment levels, but the post:pre ratios were substantially higher in a subset of the short-survival group. In both cohorts, sTRA identified a subset of poor responders that was non-identical to the one identified by CA19-9. As a result, a biomarker panel combining the markers provided better accuracy for identifying poor responders than either marker alone. In an analysis of 24 cell line models of PDAC, the cell lines that secreted sTRA had a statistically higher resistance to chemotherapy than those not secreting sTRA, whereas the cell lines secreting CA19-9 showed no such association. Therefore, pancreatic cancers that produce sTRA may be a distinct subtype with higher resistance to chemotherapy, and sTRA in combination with CA19-9 could be a valuable serological predictor of responsiveness to chemotherapy. Citation Format: Ben Staal, Ying Liu, Peter Hsueh, Mohammed Aldakkak, Herbert Zeh, Douglas Evans, Randall E. Brand, Susan Tsai, Brian B. Haab. The use of the sTRA glycan for predicting responses to neoadjuvant therapy in patients with pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3147A.

The sTRA Plasma Biomarker: Blinded Validation of Improved Accuracy Over CA19-9 in Pancreatic Cancer Diagnosis.

The CA19-9 biomarker is elevated in a substantial group of patients with pancreatic ductal adenocarcinoma (PDAC), but not enough to be reliable for the detection or diagnosis of the disease. We hypothesized that a glycan called sTRA (sialylated tumor-related antigen) is a biomarker for PDAC that improves upon CA19-9. We examined sTRA and CA19-9 expression and secretion in panels of cell lines, patient-derived xenografts, and primary tumors. We developed candidate biomarkers from sTRA and CA19-9 in a training set of 147 plasma samples and used the panels to make case-control calls, based on predetermined thresholds, in a 50-sample validation set and a blinded, 147-sample test set. The sTRA glycan was produced and secreted by pancreatic tumors and models that did not produce and secrete CA19-9. Two biomarker panels improved upon CA19-9 in the training set, one optimized for specificity, which included CA19-9 and 2 versions of the sTRA assay, and another optimized for sensitivity, which included 2 sTRA assays. Both panels achieved statistical improvement (P < 0.001) over CA19-9 in the validation set, and the specificity-optimized panel achieved statistical improvement (P < 0.001) in the blinded set: 95% specificity and 54% sensitivity (75% accuracy), compared with 97%/30% (65% accuracy). Unblinding produced further improvements and revealed independent, complementary contributions from each marker. sTRA is a validated serological biomarker of PDAC that yields improved performance over CA19-9. The new panels may enable surveillance for PDAC among people with elevated risk, or improved differential diagnosis among patients with suspected pancreatic cancer.

Abstract 4624: The sTRA glycan is complementary to CA19-9 as a serologic biomarker of pancreatic cancer

Abstract The CA19-9 biomarker is elevated in a substantial group of patients with pancreatic cancer, but not enough to be reliable for detection, diagnosis, or monitoring of the disease. We hypothesized that a glycan called sTRA complements CA19-9, and that the two biomarkers in combination provide added information over either biomarker individually. As an individual marker, the sTRA assay performed equivalently with CA19-9 for distinguishing cancers from benign pancreatic diseases, but in combination, CA19-9 and sTRA showed exclusive elevations in significantly different groups of patients. Using high-specificity cutoffs giving one false-positive detection in each marker, sTRA was elevated in 34/46 (74%) patients with low CA19-9 in stage III/IV cancers and 28/70 (40%) with low CA19-9 in stage I/II cancers. A three-marker panel consisting of CA19-9 and two versions of the sTRA assay gave 81% sensitivity and 88% specificity (84% accuracy) in a training set of 72 stage I-IV cancers and 75 benign disease controls, compared to 57% sensitivity and 92% specificity (75% accuracy) for CA19-9 alone. The application of the fixed three-marker classifier to a test set of 25 cancers and 25 benign controls gave 80% sensitivity and 84% specificity, compared to 56% sensitivity and 96% specificity for CA19-9 alone. In an analysis of patient-matched tumor tissue and plasma samples, we found that the tumors secreting both sTRA and CA19-9 into the blood tended to be conventional PDAC with well-to-moderate differentiation and heavy marker staining in the ductal lumens, but the tumors secreting only sTRA showed sTRA staining in glands with extremely large and unpolarized nuclei and vacuolated or foamy cytoplasm. Those without plasma elevations in either marker did not have glandular features of typical adenocarcinoma. Surprisingly, about half of the patients without plasma elevations of CA19-9 nevertheless showed strong tumor staining. Such tumors expressed CA19-9 mostly in poorly differentiated patches of cells with compact nuclei and cytoplasm. Thus, sTRA and CA19-9 are complementary serologic biomarkers that together could increase the diagnostic accuracy for PDAC and potentially identify distinct subgroups of tumors. Citation Format: Ying Liu, Daniel Barnett, Ben Staal, Ying Huang, Katie Partyka, Herbert Zeh, Aatur Singhi, Richard R. Drake, Randall E. Brand, Brian B. Haab. The sTRA glycan is complementary to CA19-9 as a serologic biomarker of pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4624.

The CA19-9 and Sialyl-TRA Antigens Define Separate Subpopulations of Pancreatic Cancer Cells

Molecular markers to detect subtypes of cancer cells could facilitate more effective treatment. We recently identified a carbohydrate antigen, named sTRA, that is as accurate a serological biomarker of pancreatic cancer as the cancer antigen CA19-9. We hypothesized that the cancer cells producing sTRA are a different subpopulation than those producing CA19-9. The sTRA glycan was significantly elevated in tumor tissue relative to adjacent pancreatic tissue in 3 separate tissue microarrays covering 38 patients. The morphologies of the cancer cells varied in association with glycan expression. Cells with dual staining of both markers tended to be in well-to-moderately differentiated glands with nuclear polarization, but exclusive sTRA staining was present in small clusters of cells with poor differentiation and large vacuoles, or in small and ill-defined glands. Patients with higher dual-staining of CA19-9 and sTRA had statistically longer time-to-progression after surgery. Patients with short time-to-progression (<2 years) had either low levels of the dual-stained cells or high levels of single-stained cells, and such patterns differentiated short from long time-to-progression with 90% (27/30) sensitivity and 80% (12/15) specificity. The sTRA and CA19-9 glycans define separate subpopulations of cancer cells and could together have value for classifying subtypes of pancreatic adenocarcinoma.