Generation of orthotopic intracranial glioblastoma patient-derived xenograft models: insights into extrachromosomal DNA-driven MYC(N) and PDGFRA oncogene amplification and preliminary therapeutic evaluation

Background: This study aimed to establish orthotopic intracranial patient-derived xenograft (PDX) models to investigate molecular and pathological features and to evaluate potential preclinical therapeutic approaches in glioblastoma (GBM). Methods: Fresh or cryopreserved patient tumor tissues were first expanded as subcutaneous PDXs and subsequently used to generate orthotopic intracranial PDXs. Tumor growth and similarity to patient tumors were assessed by magnetic resonance imaging (MRI), pathological analyses, and multi-omics profiling. A selected intracranial PDX was further used to evaluate the potential preclinical efficacy of natural killer (NK) cells combined with Avastin® and irinotecan. The cytotoxic effects of this combination were also examined in primary GBM cells obtained from the original tumor of the same PDX. Results: Subcutaneous PDX engraftment was successful in 13 out of 16 cases (81.3 %), and orthotopic intracranial PDXs were established from six of these with a 100 % success rate. Subcutaneous tumors expanded within 9 to 31 weeks, while intracranial tumors formed within 4 to 14 weeks. Subcutaneous growth was influenced by the Ki-67 index and the cryopreservation duration. Multi-omics analysis revealed extrachromosomal DNA (ecDNA)-driven amplifications of MYC(N), PDGFRA, CDK4, and MDM2 in PDXs from two patients. PDGFRA, CDK4, and MDM2 amplifications were consistent with those in the primary tumors, whereas MYC(N) amplification, initially minimal or absent in patient samples, was markedly enriched in the PDXs. Of the multiple PDXs from a single patient, the one PDX harboring ecDNA-driven MYCN amplification showed a greatly accelerated growth rate. Notably, PDXs containing ecDNA-driven MYC amplification exhibited a histological transformation toward primitive embryonal features. Combining NK cells with Avastin® and irinotecan enhanced cytotoxicity in vitro and prolonged survival in intracranial PDXs harboring ecDNA-driven MYC and PDGFRA amplifications. Conclusion: Intracranial PDX models were successfully established from cryopreserved GBM tissues through subcutaneous expansion. These models offer a clinically relevant platform for investigating GBM biology and evaluating the therapeutic efficacy of chemoimmunotherapy.