Inhibition of enzymatic activity of HRD1 results in death of cells derived from glioblastoma multiforme, neuroblastoma, and normal astrocytes.

The aim of the present study was to examine the impact of LS-102, an inhibitor of enzymatic activity of HRD1 that is an essential E3 ubiquitin ligase of endoplasmic reticulum associated degradation (ERAD) on survival of the human cell lines derived from glioblastoma multiforme (GBM), neuroblastoma, and astrocytes. We have also examined molecular responses to HRD1 inhibition with a focus on proteins playing an essential role in unfolded protein response (UPR) and ERAD. In addition, activation of IRE1α documented by XBP1 splicing was investigated. Finally, we have examined the impact of LS-102 on p53 expression in GBM cells. Inhibition of HRD1 enzymatic activity results in cell death of all tested cells. With respect to GBM cells, U87 cells are more sensitive to LS-102 as T98G cells. Cells of cell lines derived from normal astrocytes K1884 exhibit the highest sensitivity to LS-102 among all cell types used in the study while NHA cells are the most resistant. Sensitivity of neuroblastoma SH-SY5Y cells to LS-102 is comparable to the sensitivity of U87 cells. In GBM cells, inhibition of HRD1 results in induction of the expression of proteins playing an essential role in UPR and ERAD (HRD1, SEL1L, and GRP78). XBP1 splicing induced by HRD1 inhibition was documented in T98G and K1884 cells. We did not observe induction of p53 expression in U87 cells. Since LS-102 induces cell death of normal astrocytes, it is not a candidate for the testing of its potential use as an antitumor treatment of GBM.