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Affiliations of authors: Department of Medical Oncology (EG, AA, GJP) and Department of Neurosurgery (TL, VC, TW), VU University Medical Center, and Centre for Integrative Bioinformatics (AvdV), VU University, Amsterdam, the Netherlands; Department of Ricerca Traslazionale e delle Nuove Tecnologie in Medicina e Chirurgia, University of Pisa, Pisa, Italy (NF, UB, EV); Department of Neurology, Stanford University, Stanford, CA (VC); Department of Neurology, Massachusetts General Hospital and Neuroscience Program, Harvard Medical School, Boston, MA (TW); Medical Oncology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD (QW, J-HL, YW, GG).
Published: January 2014
AI Article Synopsis
Article Abstract
Background: Loss of 18q22.3 is a prognostic marker in pancreatic ductal adenocarcinoma (PDAC). This study investigated genes encoded by this cytoband.
Methods: We studied mRNA/protein expression in radically resected (n = 130) and metastatic patients (n = 50). The role of CYB5A was tested in 11 PDAC cell lines and five primary cultures through retrovirus-mediated upregulation and small interfering RNA using wound-healing, invasion, annexin-V, electron microscopy, and autophagic assays, as well as autophagy genes and kinases arrays. CYB5A+ orthotopic models (n = 6 mice/group) were monitored by Firefly and Gaussia-luciferase bioluminescence, magnetic resonance imaging, and high-frequency ultrasound. Data were analyzed by t test, Fisher exact-test, log-rank test and Cox proportional hazards models. All statistical tests were two-sided.
Results: Both resected and metastatic patients with low mRNA or protein expression of CYB5A had statistically significantly shorter survival (eg, median = 16.7 months, 95% confidence interval [CI] = 13.5 to 19.9; vs median = 24.8 months, 95% CI = 12.8 to 36.9; P = .02, two-sided log-rank test; n = 82 radically resected PDACs), and multivariable analyses confirmed prognostic relevance. Moreover, we characterized a novel function to CYB5A, autophagy induction, concomitant with reduced proliferation and migration/invasion of PDAC cells. Network analysis of proautophagic pathways suggested CYB5A interaction with TRAF6, which was confirmed by TRAF6 downregulation after CYB5A reconstitution (-69% in SU.86.86-CYB5A+; P = .005, two-sided t test). CYB5A silencing had opposite effects, restoring TRAF6 expression and wound healing. In vivo studies showed that CYB5A induced autophagy while inhibiting tumor growth/metastasis and increasing survival (median = 57 days, 95% CI = 52 to 61; vs median = 44 days, 95% CI = 21 to 57; P = .03, two-sided log-rank test).
Conclusions: These results define CYB5A as a novel prognostic factor for PDAC that exerts its tumor-suppressor function through autophagy induction and TRAF6 modulation.
