Early Diagnostic Ability of Human Complement Factor B in Pancreatic Cancer Is Partly Linked to Its Potential Tumor-Promoting Role

Abstract

Although plasma complement factor B (CFB, NX_P00751), both alone and in combination with CA19-9 (i.e., the ComB-CAN), previously exhibited a reliable diagnostic ability for pancreatic cancer (PC), its detectability of the early stages and the cancer detection mechanism remained elusive. We first evaluated the diagnostic accuracy of ComB-CAN using plasma samples from healthy donors (HDs), patients with chronic pancreatitis (CP), and patients with different PC stages (I/II vs III/IV). An analysis of the area under the curve (AUC) by PanelComposer using logistic regression revealed that ComB-CAN has a superior diagnostic ability for early-stage PC (97.1.% [95% confidence interval (CI): (97.1–97.2)]) compared with CFB (94.3% [95% CI: 94.2–94.4]) or CA19-9 alone (34.3% [95% CI: 34.1–34.4]). In the comparisons of all stages of patients with PC vs CP and HDs, the AUC values of ComB-CAN, CFB, and CA19-9 were 0.983 (95% CI: 0.983–0.983), 0.950 (95% CI: 0.950-0.951), and 0.873 (95% CI: 0.873–0.874), respectively. We then investigated the molecular mechanism underlying the detection of early-stage PC by using stable cell lines of CFB knockdown and CFB overexpression. A global transcriptomic analysis coupled to cell invasion assays of both CFB-modulated cell lines suggested that CFB plays a tumor-promoting role in PC, which likely initiates the PI3K-AKT cancer signaling pathway. Thus our study establishes ComB-CAN as a reliable early diagnostic marker for PC that can be clinically applied for early PC screening in the general public.

Inhibition of the Alternative Complement Pathway May Cause Secretion of Factor B, Enabling an Early Detection of Pancreatic Cancer

“…To our knowledge, this represents the first observation of quantitatively differential expression of proteotypic peptide fragments of CFB (seq 2) present in the plasma of PDAC patients across different disease stages, consistent with the conventional ELISA assay results. 36,37 These findings also provide potential insights into changes in the ACP activity in this cancer across different disease stages.…”

“…56−58 Specifically, PDAC cell lines harboring KRAS mutation have been found to exhibit higher expression levels of CFB, shedding light on the oncogenic activity of CFB within the context of KRAS mutation. 13,37 Furthermore, it is known that KRAS mutation positively regulates the expression levels of complement factors and their regulator (s), including C3b, CFB, CFH, and AM (Figures 3 and 7). For the AM's role in carcinogenesis, previous studies have indicated that tumor-associated macrophages (TAMs) induce AM synthesis, which, in turn, promotes cancer cell growth, suggesting a synergistic role of AM and TAMs in the malignant development of cancer.…”

“…For transient transfection, BXPC3 cells (KRAS WT) were seeded in 24-well plates at a density of 1 × 10 5 cells/well and transfected the next day with AM plasmid using Lipofectamine 3000 (Thermo Fisher Scientific, #L3000001) according to the manufacturer’s instructions. The AM expressions were then verified by RT-PCR and Western blot analyses …”

“…This combination proves particularly valuable for PDAC patients lacking the Lewis antigen gene, a condition occurring in 5–10% of the population. , However, the precise cellular mechanism behind the increased presence of CFB in the blood of PDAC patients, serving as an indicator of early-stage pancreatic carcinogenesis, remains unresolved to date. Previous hypotheses have postulated a connection between CFB’s biomarker role in PDAC and the ACP cascade . Thus, we set out to address this enduring question regarding the cellular mechanisms driving the release of CFB into the bloodstream during early-stage PDAC.…”

“…Previous hypotheses have postulated a connection between CFB's biomarker role in PDAC and the ACP cascade. 37 Thus, we set out to address this enduring question regarding the cellular mechanisms driving the release of CFB into the bloodstream during early-stage PDAC. Initially, to confirm the elevated CFB levels at the peptide level as a PDAC biomarker, we conducted an absolute quantification of proteotypic peptides representing CFB in the PDAC plasma using the parallel reaction monitoring (PRM) assay.…”