DDDR-21 - A temozolomide-induced long noncoding RNA, linc02454, regulates chemosensitivity in glioblastoma via modulation of CXCR4

Introduction: Chemoresistance is one of the primary factors influencing the poor prognosis in glioblastoma (GBM) patients. Long noncoding RNAs (lncRNAs) are a novel class of RNAs representing up to 80% of the genome, and noted to induce profound alterations in transcriptional regulation and phenotype, including chemotherapy response. We therefore set out to identify novel lncRNAs induced by chemotherapy that regulate GBM chemosensitivity. We further evaluated the mechanism by which a candidate chemoresistance-associated lncRNA exerts function.

Methods: We evaluated gene expression following temozolomide treatment in multiple glioma lines (via RNA-seq). Candidate lncRNAs demonstrating significant expression upon TMZ treatment were assessed for association with patient survival. We further evaluated the effect of knockdown of candidate lncRNAs upon resulting TMZ sensitivity and downstream gene expression.

Results: Linc02454 was among the most highly upregulated genes following TMZ treatment. Linc02454 resides on chromosome 12q14 within a locus of genes amplified in 10% of GBM patients. Elevated linc02454 expression was associated with decreased survival in TCGA data, while linc02454 knockdown reduced in vitro GBM cell viability in response to TMZ. RNA-seq identified CXC-chemokine receptor 4 (CXCR4) among the most heavily downregulated genes following lncRNA knockdown. Finally, TMZ induces similar increases in linc02454 and CXCR4, while CXCR4 KD chemosensitivity phenotypes closely parallel linc02454 KD phenotypes.

Conclusion: TMZ-induced increases in long noncoding RNAs, particularly in linc02454, regulate expression of well-known and previously targeted chemokines, including CXCR4. Subsequent studies, evaluating the manner by which chemotherapy increases linc02454, and the manner by which linc02454 affects CXCR4 and treatment sensitivity may improve GBM temozolomide sensitivity.