ALKBH5 Facilitates Hypoxia-Induced Paraspeckle Assembly and IL8 Secretion to Generate an Immunosuppressive Tumor Microenvironment.

Abstract

The dynamic changes of RNA N6-methyl-adenosine (m⁶A) during cancer progression contribute to quick adaption to microenvironmental changes. Here, we profiled the cancer cell m⁶A dynamics in the hypoxic tumor niche and its pathological consequences in glioblastoma multiforme (GBM). The m⁶A demethylase ALKBH5 was induced in GBM models under hypoxic conditions and was associated with a hypoxic gene signature in GBM patient samples. Depletion or inactivation of ALKBH5 in GBM cells significantly suppressed hypoxia-induced tumor-associated macrophage (TAM) recruitment and immunosuppression in allograft tumors. Expression and secretion of CXCL8/IL8 were significantly suppressed in ALKBH5-deficient tumors. However, ALKBH5 did not regulate CXCL8 m⁶A directly. Instead, hypoxia-induced ALKBH5 erased m⁶A deposition from the lncRNA NEAT1, stabilizing the transcript and facilitating NEAT1-mediated paraspeckle assembly, which led to relocation of the transcriptional repressor SFPQ from the CXCL8 promoter to paraspeckles and, ultimately, upregulation of CXCL8/IL8 expression. Accordingly, ectopic expression of CXCL8 in ALKBH5-deficient GBM cells partially restored TAM recruitment and tumor progression. Together, this study links hypoxia-induced epitranscriptomic changes to the emergence of an immunosuppressive microenvironment facilitating tumor evasion. SIGNIFICANCE: Hypoxia induces tumor immune microenvironment remodeling through an ALKBH5-mediated epigenetic and epitranscriptomic mechanism, providing potential immunotherapeutic strategies for treating glioblastoma.