gms | German Medical Science

Objective: Glioma stem cells (GSCs) are considered to be responsible for glioblastoma's (GBM) dismal prognosis. The Wingless (WNT) signaling pathway promotes stemness and resistance towards therapies in various cancers including of the brain, however underlying molecular mediators of chemo resistance are not fully understood.

Methods: Spheroidal GSC cultures were pharmacologically treated with novel porcupine inhibitor WNT974/LGK974 as well as temozolomide (TMZ). Whole mRNA activation levels were assessed with Affymetrix Gene Expression Array technology. Genetic suppression of gene activation was achieved through CRISPR/Cas9 mediated genome modification verified by SYBR green based transcript quantification or Western blot based protein analyses. Functional in vitro assays of the project include measurement of growth with Titer Blue and clonogenicity with Soft agar assay.

Results: We have previously shown that pharmacological WNT inhibition using LGK974 reduces stem cell properties in glioblastoma in vitro. Here, we demonstrate that LGK974 together with standard of care options TMZ or γ-radiation acts synergistically in terms of suppression of cell growth. Importantly, we observed synergy in cells independent of their O6-alkylguanine DNA alkyltransferase (MGMT) promoter methylation status, known to predict TMZ response rate in GBM. Applying global transcriptomics and genetic suppression models, we identified the oxidative enzyme aldehyde dehydrogenase 3A1 (ALDH3A1) as a novel WNT pathway target in GBMs involved in promoting resistance against TMZ. Moreover, ALDH3A1 blockade caused significant suppression of various stem cell characteristics.

Conclusion: Our study supports a novel role of ALDH3A1 in GBM mediating resistance to TMZ through the promotion of stem cell properties related to aberrant WNT signaling.