American Association for Cancer Research
10780432ccr180792-sup-198375_2_supp_4813331_ps0v9b.jpeg (561.79 kB)

Supplementary figure 1 from Oligosaccharyltransferase Inhibition Reduces Receptor Tyrosine Kinase Activation and Enhances Glioma Radiosensitivity

Download (561.79 kB)
posted on 2023-03-31, 21:41 authored by Marta Baro, Cecilia Lopez Sambrooks, Amanda Quijano, W. Mark Saltzman, Joseph Contessa

Dose response of NGI-1, temozolomide and etoposide in glioma cell lines





Parallel signaling reduces the effects of receptor tyrosine kinase (RTK)–targeted therapies in glioma. We hypothesized that inhibition of protein N-linked glycosylation, an endoplasmic reticulum co- and posttranslational modification crucial for RTK maturation and activation, could provide a new therapeutic approach for glioma radiosensitization.Experimental Design: We investigated the effects of a small-molecule inhibitor of the oligosaccharyltransferase (NGI-1) on EGFR family receptors, MET, PDGFR, and FGFR1. The influence of glycosylation state on tumor cell radiosensitivity, chemotherapy-induced cell toxicity, DNA damage, and cell-cycle arrest were determined and correlated with glioma cell receptor expression profiles. The effects of NGI-1 on xenograft tumor growth were tested using a nanoparticle formulation validated by in vivo molecular imaging. A mechanistic role for RTK signaling was evaluated through the expression of a glycosylation-independent CD8-EGFR chimera. NGI-1 reduced glycosylation, protein levels, and activation of most RTKs. NGI-1 also enhanced the radiosensitivity and cytotoxic effects of chemotherapy in those glioma cells with elevated ErbB family activation, but not in cells without high levels of RTK activation. NGI-1 radiosensitization was associated with increases in both DNA damage and G1 cell-cycle arrest. Combined treatment of glioma xenografts with fractionated radiotherapy and NGI-1 significantly reduced tumor growth compared with controls. Expression of the CD8-EGFR eliminated the effects of NGI-1 on G1 arrest, DNA damage, and cellular radiosensitivity, identifying RTK inhibition as the principal mechanism for the NGI-1 effect. This study suggests that oligosaccharyltransferase inhibition with NGI-1 is a novel approach to radiosensitize malignant gliomas with enhanced RTK signaling.See related commentary by Wahl and Lawrence, p. 455