Absent in melanoma 2 regulates tumor cell proliferation in glioblastoma multiforme

摘要

Introduction Inflammation is a key aspect of glioblastoma multiforme (GBM) although it remains unclear how it contributes to GBM pathogenesis. Inflammasomes are intracellular multi-protein complexes that are involved in innate immunity and are activated by cellular stress, principally in macrophages. This study examined the expression of inflammasome-associated genes in GBM, particularly absent in melanoma 2 (AIM2). Methods Tissue samples from surgically-resected GBM tumors (n = 10) were compared to resected brain specimens from patients with epilepsy (age- and sex-matched Other Disease Controls (ODC, n=5)) by qRT-PCR, western blotting and immunofluorescence. Gene expression studies in human astrocytoma U251 cells were performed and the effects of deleting the absent in melanoma 2 (AIM2) gene using the CRISPR-Cas9 system were analyzed. Results GBM tissues showed significantly elevated expression of multiple immune (CD3E, CD163, CD68, MX1, ARG1) and inflammasome (AIM2, NLRP1, IL18, CASP1, and IL-33) genes compared to ODC tissues, without induction of IL1B, IFNG or TNFA. An insert-containing AIM2 variant transcript was highly expressed in GBM tissues and in U251 cells. AIM2 immunoreactivity was concentrated in the tumor core in the absence of PCNA immunodetection and showed a predominant 52 kDa immunoreactive band on western blot. Deletion of AIM2 resulted in significantly enhanced proliferation of U251 cells, which also displayed increased resistance to temozolomide treatment. Conclusions GBM tumors express a distinct profile of inflammasome-associated genes in a tumor-specific manner. AIM2 expression in tumor cells suppressed cell proliferation while also conferring increased susceptibility to contemporary GBM therapy.