Tumor Edge-to-Core Transition Promotes Malignancy in Primary-to-Recurrent Glioblastoma Progression in a PLAGL1/CD109-mediated mechanism
Authors: Li Chaoxi , Cho Hee Jin , Yamashita Daisuke , Abdelrashid Moaaz , Chen Qin , Bastola Soniya , Chagoya Gustavo , A. Elsayed Galal , Komarova Svetlana , Ozaki Saya , Ohtsuka Yoshihiro , Kunieda Takeharu , Kornblum Harley I , Kondo Toru , Nam Do-Hyun , Nakano Ichiro 
Published: September 2020

Background

Glioblastoma remains highly lethal due to its inevitable recurrence. This recurrence is found locally in most cases, indicating that post-surgical tumor-initiating cells (TICs) accumulate at tumor edge. These edge TICs then generate recurrent tumors harboring new core lesions. Here, we investigated the clinical significance of the edge-to-core transition (ECT) signature causing glioblastoma recurrence and sought to identify central mediators for ECT.

Methods

First, we examined the association of the ETC-related expression changes and patient outcome in matched primary and recurrent samples (n=37). Specifically, we tested whether the combined decrease of the edge TIC marker PROM1 (CD133) with the increase of the core TIC marker CD109 representing ECT during the primary-to-recurrence progression indicates poorer patient outcome. We then investigated the specific molecular mediators that trigger tumor recurrence driven by the ECT signature. Subsequently, the functional and translational significance of the identified molecule was validated within our patient-derived tumor edge-TIC modelsin vitroandin vivo.

Results

Patients exhibiting a CD133down/CD109upsignature during recurrence representing ECT displayed a strong association with poorer progression-free survival and overall survival among all tested patients. Differential gene expression identified that PLAGL1 was tightly correlated with the core TIC marker CD109 and was linked to a shorter survival of glioblastoma patients. Experimentally, forced PLAGL1 overexpression enhanced, while its knockdown reduced, the glioblastoma edge-derived tumor growthin vivoand subsequent mouse survival, suggesting its essential role in the ECT-mediated glioblastoma development.

Conclusions

ECT is likely an ongoing lethal process in primary glioblastoma contributing to its recurrence partly in a PLAGL1/CD109-mediated mechanism.

Key Points

ECT is a pathobiological process contributing to glioblastoma lethality

The CD133down/CD109upsignature is a novel prognostic molecular biomarker in ECT

PLAGL1 regulates growth of edge-located tumor-initiating cells

Importance of the Study

Very few studies have sought to longitudinally characterize the transition of molecular landscapes from primary to recurrent glioblastoma. Post-surgical edge-located TICs are presumably the predominant source of tumor recurrence, yet this cellular subpopulation in glioblastoma remains largely uncharacterized. This study evaluates the significance of glioblastoma edge-derived core transition (ECT) for tumor recurrence in the primary-recurrent paired sample set. We elucidate a prognostically-significant shift in molecular and cellular phenotypes associated with ECT in the CD133down/CD109upgroup. Moreover, our results provide clinical and experimental evidence that PLAGL1 is a mediator of glioblastoma ECT and its subsequent tumor development by the direct transcriptional regulation of the core TIC marker CD109.