Investigating the Association between the Autophagy Markers LC3B, SQSTM1/p62, and DRAM and Autophagy-Related Genes in Glioma

Abstract

High-grade gliomas are extremely fatal tumors, marked by severe hypoxia and therapeutic resistance. Autophagy is a cellular degradative process that can be activated by hypoxia, ultimately resulting in tumor advancement and chemo-resistance. Our study aimed to examine the link between autophagy markers' expression in low-grade gliomas (LGGs) and high-grade gliomas (HGGs). In 39 glioma cases, we assessed the protein expression of autophagy markers LC3B, SQSTM1/p62, and DRAM by immunohistochemistry (IHC) and the mRNA expression of the autophagy genes PTEN, PI3K, AKT, mTOR, ULK1, ULK2, UVRAG, Beclin 1, and VPS34 using RT-qPCR. LC3B, SQSTM1/p62, and DRAM expression were positive in 64.1%, 51.3%, and 28.2% of glioma cases, respectively. The expression of LC3B and SQSTM1/p62 was notably higher in HGGs compared to LGGs. VPS34 exhibited a significant differential expression, displaying increased fold change in HGGs compared to LGGs. Additionally, it exhibited robust positive associations with Beclin1 (rs = 0.768), UVRAG (rs = 0.802), and ULK2 (rs = 0.786) in HGGs. This underscores a potential association between autophagy and the progression of gliomas. We provide preliminary data for the functional analysis of autophagy using a cell culture model and to identify potential targets for therapeutic interventions.

Keywords: DRAM; LC3B; SQSTM1/p62; autophagy; autophagy-related genes (ATGs); high-grade gliomas (HGGs); low-grade gliomas (LGGs).

Figure 1

Representative images of autophagy markers LC3B, SQSTM1/p62, and DRAM immunohistochemical stains in peritumoral non-glioma tissue, low-grade glioma (LGG) and high-grade gliomas (HGG) at ×400. Peritumoral non-glioma tissues and LGGs showing negative staining for autophagy markers while HGGs displaying strong dotted or punctuate cytoplasmic staining for LC3B and SQSTM1/p62 and diffuse cytoplasmic staining for DRAM.

Figure 2

Expression of autophagy-related genes (ATGs) in 2, 3, and 4 WHO grades of diffuse gliomas in 39 patients using housekeeping gene Beta-actin. The Y-axis shows the relative expression of each ATG tested. The line with the asterisk sign shows a significant difference (* p < 0.01) in the expression of VPS34 between the various grades of gliomas.

Figure 3

The graph depicts the fold change in the expression of VPS34 and mTOR in the WHO grade 2, 3, and 4 gliomas. The Y-axis represents the logarithmic fold expression. The lines marked with asterisks indicate a notable difference (* p < 0.01) in VPS34 expression between low- and high-grade cases.