Panoply™ Human IL33 Knockdown Stable Cell Line

Gliomas are the most common subtype of primary brain tumors and represent a highly aggressive form of nervous system cancer. Interleukin-33 (IL-33) is recognized as a dual-function cytokine: it acts both as an "alarmin" released upon tissue damage and as a protein associated with nuclear chromatin. In this study, researchers performed IL-33 gene knockdown (IL33KD) and overexpression (IL33oe) in rat C6 glioma cells and human glioma cell lines (U251MG and U87MG). The results showed that IL33oe glioma cells developed resistance to the DNA-damaging effects of the alkylating agent temozolomide (TMZ), a phenomenon likely attributable to the upregulated expression of DNA repair genes in these cells. Furthermore, analysis of nuclear morphology via transmission electron microscopy (TEM) and histone H2A immunofluorescence staining revealed that IL33KD attenuated abnormal nuclear features in cancer cells (such as nuclear invaginations, elongated clefts, and multiple nucleoli); conversely, IL33oe promoted alterations in nuclear morphology, such as the formation of multilobed nuclei. Additional findings indicated that IL33KD led to reduced levels of histones H2A and H3, as well as the downregulation of the non-histone DNA-binding nuclear proteins HMGA1 (high-mobility group protein A1) and HMGA2. In contrast, IL33oe resulted in elevated levels of H2A, H3, HMGA1, and HMGA2 proteins. Taken together, these results demonstrate that the upregulation of nuclear IL-33 expression is associated with increased expression of DNA repair genes, thereby reducing the sensitivity of glioma cells to DNA-damaging agents.

Transmission electron microscopy (TEM) analysis of U251MG nuclear morphology revealed that Scramble-U251MG cells exhibited nuclear structures characterized by grooves and long clefts (Figure 1A, arrows) as well as multiple nucleoli (Figure 1A, arrowheads), whereas such structures were less frequently observed in IL33KD-U251MG cells. Nuclear IL-33 is a chromatin-associated protein that functions by binding to the acidic patches of histones H2A and H2B. Researchers further performed immunofluorescence assays targeting H2A in U251MG and U87MG cells. The results showed that IL33KD reduced nuclear grooves and clefts (Figure 1B, arrows), whereas IL33 overexpression (IL33oe) promoted the formation of abnormal nuclear lobulation (Figure 1B, arrowheads). Similarly, IL33oe-induced nuclear polylobulation was observed in U87MG cells (Figure 1C, arrowheads). These findings suggest that nuclear IL-33 protein may regulate nuclear morphology through interactions with histones and chromatin.

Figure 1. Altered expression of nuclear IL-33 causes a change in the nuclear shape of human glioma cells. (Chung Y H, et al., 2021)