Modeling Therapy-Driven Evolution of Glioblastoma with Patient-Derived Xenografts

Abstract

Adult-type diffusely infiltrating gliomas, of which glioblastoma is the most common and aggressive, almost always recur after treatment and are fatal. Improved understanding of therapy-driven tumor evolution and acquired therapy resistance in gliomas is essential for improving patient outcomes, yet the majority of the models currently used in preclinical research are of therapy-naïve tumors. Here, we describe the development of therapy-resistant IDH-wildtype glioblastoma patient-derived xenografts (PDX) through orthotopic engraftment of therapy naïve PDX in athymic nude mice, and repeated in vivo exposure to the therapeutic modalities most often used in treating glioblastoma patients: radiotherapy and temozolomide chemotherapy. Post-temozolomide PDX became enriched for C>T transition mutations, acquired inactivating mutations in DNA mismatch repair genes (especially MSH6), and developed hypermutation. Such post-temozolomide PDX were resistant to additional temozolomide (median survival decrease from 80 days in parental PDX to 42 days in a temozolomide-resistant derivative). However, temozolomide-resistant PDX were sensitive to lomustine (also known as CCNU), a nitrosourea which induces tumor cell apoptosis by a different mechanism than temozolomide. These PDX models mimic changes observed in recurrent GBM in patients, including critical features of therapy-driven tumor evolution. These models can therefore serve as valuable tools for improving our understanding and treatment of recurrent glioma.

Ribonucleotide reductase regulatory subunit M2 drives glioblastoma TMZ resistance through modulation of dNTP production

“…5K). Furthermore, combination therapy is also effective on a TMZ-resistant recurrent PDX model, GBM6R (Bottom left, P = 0.0008), resistant to TMZ therapy ( 44 ).…”

In vivo perturb-seq of cancer and microenvironment cells dissects oncologic drivers and radiotherapy responses in glioblastoma

“…The observation that in vivo perturbations resulted in greater heterogeneity of transcriptional responses, especially when combined with radiotherapy, was a distinct feature of performing perturbations within a preformed tumor with an intact immune system. However, we cannot exclude contributions from differences in the experimental timelines between in vitro and in vivo perturb-seq workflows, as in vivo experimental timelines were constrained by slower growth rates of tumors compared to their respective cell cultures 53 , therefore requiring longer periods of time between perturbation and cell isolation. Furthermore, the apparent discrepancy between the cell types transduced by sgRNA lentiviruses in the GL261 CED experiments for CRISPRi in malignant cells (Fig.…”