DNA damage repair kinase DNA-PK and cGAS synergize to induce cancer-related inflammation in glioblastoma (2022)
Figure 6

Figure 6. cGAS and DNA-PKcs levels increase with tumor grade

A Correlation plot between PRKDC and MD21B1 expression in glioblastoma patients. Three distinct populations can be visualized: PRKDClow/MD21B1low; PRKDChigh/MD21B1low and PRKDChigh/MD21B1high (total patients n=224).

B Violin plots present chemokine gene expression (CXCL10, CCL2 and CCL5) in glioblastoma samples from A.

C Violin plots present macrophage gene expression (CD68 and ITGAM) in glioblastoma samples from A.

D Violin plots present pro-inflammatory M1 macrophage gene expression (CD86 and CD80) in glioblastoma samples from A.

E Violin plots present anti-inflammatory M2 macrophages gene expression (CD200R1 and CD209) in glioblastoma in samples from A.

F Violin plots present M1/M2 gene expression ratio, calculated using the mean expression of the genes indicated in D and E.

G Graph presents the survival rate of glioblastoma patients from A that present PRKDClow/MB21D1low, PRKDChigh/MB21D1low and PRKDChigh/MB21D1high expression.

H Violin plots present the expression of PRKDC and MB21D1 in datasets analyzed in A, based on tumor grade (II to IV).

I Representative images of immunohistochemical analysis of DNA-PKcs and cGAS proteins in human brain tumor samples. Scale bar, 75 µm.

J Schematic representation of the molecular mechanisms involved in the cooperation between DNA-PKcs and cGAS for type I IFN responses and chemokine secretion. In cells with undetectable cGAS levels, interaction with exogenous (1) or endogenous (2) cytosolic dsDNA leads to DNA-PK activation (3) and promotes IRF3-dependent type I IFN responses (4). In cells where both DNA-PK and cGAS are expressed, cytosolic DNA is detected by both DNA-PK and cGAS (5). DNA-PK induces cytokine and chemokine secretion through IRF3 activation and enables cGAS phosphorylation, thus promoting the activation of the cGAS-STING pathway. This cooperation fuels cancer-associated inflammation.

Data information: All graphs present means ± SEM. P-values were determined by Student's t-test. ns: not significant. * p < 0.05, ** p < 0.01, *** p < 0.001, **** p < 0.0001. One-way Anova with Tukey's multiple comparisons test was used to compare gene expression among populations in glioblastoma dataset.

Table I. Correlation between the levels of DNA-PKcs and cGAS in surgical specimens of human brain tumors. Summary of the expression patterns of DNA-PKcs and cGAS in human glioma samples. The correlation between DNA-PKcs and cGAS protein levels was analyzed using SPSS Pearson Chi-Square test (R=0.406, p=0.00568). A p-value of less than 0.05 was set as the criterion for statistical significance.

DNA-PKcs expression

- / + ++ +++ Total R/p value

cGAS - / + 9(69.2%) 6(26.1%) 2(22.2%) 17(37.8%)

++ 2(15.4%) 13(56.5%) 1(11.1%) 16(35.6%)

+++ 2(15.4%) 4(17.4%) 6(66.7%) 12(26.6%) R=0.406

Total 13(100%) 23(100%) 9(100%) 45(100%) p=0.006

Table II. Correlation between the levels of DNA-PKcs or cGAS and tumor grades in surgical specimens of human brain tumors. Summary of the expression patterns of DNA-PKcs and cGAS in human glioma samples. The correlation between tumor grades and DNA-PKcs or cGAS protein levels was analyzed using Pearson correlation test. A p-value of less than 0.05 was set as the criterion for statistical significance.

Tumor grades

I/I-II II/II-III III/III-IV IV R/p value

cGAS - / + 6(66.7%) 3(18.8%) 5(41.7%) 0(0%)

++ 3(33.3%) 7(43.8%) 5(41.7%) 1(25%)

+++ 0(0%) 6(37.4%) 2(16.6%) 3(75%) R=0.3211

Total 9(100%) 16(100%) 12(100%) 4(100%) p=0.0406

DNA-PKcs - / + 5(55.6%) 3(18.8%) 6(50%) 0(0%)

++ 4(44.4%) 10(62.5%) 1(8.3%) 0(0%)

+++ 0(0%) 3(18.8%) 5(41.7%) 4(100%) R=0.4335

Total 9(100%) 16(100%) 12(100%) 4(100%) p=0.0046

EXPANDED VIEW FIGURE LEGENDS