The Distant Molecular Effects on the Brain by Cancer Treatment

Abstract

Cancer survivors experience cancer-related cognitive impairment (CRCI) secondary to treatment. Chemotherapy and radiation therapy independently contribute to cognitive dysfunction; however, the underlying mechanisms leading to dysfunction remain unclear. We characterized brain gene expression changes in a mouse model of CRCI to identify the mechanistic underpinnings. Eleven-to-twelve-week-old SKH1 mice were treated with doxorubicin (DOX), hindlimb radiation (RT), concurrent hindlimb radiation and doxorubicin (DOX-RT), or no treatment (control). Sixteen days following treatment, gene expression was measured from murine brains using the NanoString nCounter^® glial profiling panel. Gene expression was normalized and compared between groups. No two groups shared the same expression pattern, and only Gnb1 and Srpr were upregulated in multiple treatment groups. Brains from DOX-treated mice had upregulated Atf2, Atp5b, Gnb1, Rad23b, and Srpr and downregulated Sirt5 expression compared to control brains. Brains from RT-treated mice demonstrated increased Abcg2 and Fgf2 and decreased C1qa and C1qb expression compared to control brains. Brains from DOX-RT-treated mice had upregulated Adar, E2f3, Erlec1, Gnb1, Srpr, Vim, and Pdgfra expression and downregulated Rock2 and Inpp5f expression compared to control brains. The gene expression changes demonstrated here highlight roles for neuronal transmission and oxidative stress in the pathogenesis of doxorubicin-related CRCI and inflammation in RT-related CRCI.

Keywords: SKH1 mice; cancer neuropathology; cancer treatment; cancer-related cognitive impairment CRCI.

Figure 1

Overview of gene changes in the brain of mice treated with cancer treatment. (A) Heat map of normalized data, with orange indicating high expression and blue indicating low expression. (B) Heatmap showing gene pathway clustering of the groups. Control, control mice; DOX, doxorubicin-treated mice; RT, hindlimb-radiation-treated mice; DOX-RT, doxorubicin- and hindlimb-radiation-treated mice. n = 6 mice per group.

Figure 1

Overview of gene changes in the brain of mice treated with cancer treatment. (A) Heat map of normalized data, with orange indicating high expression and blue indicating low expression. (B) Heatmap showing gene pathway clustering of the groups. Control, control mice; DOX, doxorubicin-treated mice; RT, hindlimb-radiation-treated mice; DOX-RT, doxorubicin- and hindlimb-radiation-treated mice. n = 6 mice per group.

Figure 2

Cancer treatment is associated with molecular changes in the brain. (A) Volcano plot shows all differentially expressed genes above background between brains from DOX and control mice, with genes of high statistical significance on top and high fold change on either side using a log linear regression. (B) Volcano plot shows all differential expressed genes above background between brains from RT and control mice, with genes of high statistical significance on top and high fold change on either side using a log linear regression. (C) Volcano plot shows all differential expressed genes above background between brains from DOX-RT and control mice, with genes of high statistical significance on top and high fold change on either side using a log linear regression. Solid line p-value < 0.01; dotted line p-value < 0.001. Control, control mice; DOX, doxorubicin-treated mice; RT, hindlimb-radiation-treated mice; DOX-RT, doxorubicin- and hindlimb-radiation-treated mice. n = 6 mice per group.

Figure 2

Cancer treatment is associated with molecular changes in the brain. (A) Volcano plot shows all differentially expressed genes above background between brains from DOX and control mice, with genes of high statistical significance on top and high fold change on either side using a log linear regression. (B) Volcano plot shows all differential expressed genes above background between brains from RT and control mice, with genes of high statistical significance on top and high fold change on either side using a log linear regression. (C) Volcano plot shows all differential expressed genes above background between brains from DOX-RT and control mice, with genes of high statistical significance on top and high fold change on either side using a log linear regression. Solid line p-value < 0.01; dotted line p-value < 0.001. Control, control mice; DOX, doxorubicin-treated mice; RT, hindlimb-radiation-treated mice; DOX-RT, doxorubicin- and hindlimb-radiation-treated mice. n = 6 mice per group.

Figure 3

Cancer treatment causes significant gene changes in the brain of mice. Mice treated with DOX had significant upregulation of genes in their brain, including Atf2 (A), Atp5b (B), Gnb1 (C), Rad23b (D), and Srpr (F), compared to control mice. Mice treated with DOX-RT had significant downregulation of the Sirt5 (E) gene in their brain compared to control mice. Comparison showed brains from mice treated with RT had significant upregulation of Abcg2 (G) and Fgf2 (J) genes and downregulation of C1qa (H) and C1qb (I) compared to control mice. Mice treated with DOX-RT had significant upregulation of Adar (K), E2f3 (L), Erlec1 (M), Gnb1 (C), Pdgfra (O), Srpr (F), and Vim (Q) gene expression and downregulation of Inpp5f (N) and Rock2 (P) gene expression compared to control mice. Data represent the mean and SEM evaluated by ANOVA and post hoc analysis. DOX, doxorubicin-treated group; RT, hindlimb-radiation-treated group; DOX-RT, doxorubicin- and hindlimb-radiation-treated group. n = 6 mice per group. * p-value < 0.05; ** p-value < 0.01; *** p-value < 0.001.

Figure 3

Cancer treatment causes significant gene changes in the brain of mice. Mice treated with DOX had significant upregulation of genes in their brain, including Atf2 (A), Atp5b (B), Gnb1 (C), Rad23b (D), and Srpr (F), compared to control mice. Mice treated with DOX-RT had significant downregulation of the Sirt5 (E) gene in their brain compared to control mice. Comparison showed brains from mice treated with RT had significant upregulation of Abcg2 (G) and Fgf2 (J) genes and downregulation of C1qa (H) and C1qb (I) compared to control mice. Mice treated with DOX-RT had significant upregulation of Adar (K), E2f3 (L), Erlec1 (M), Gnb1 (C), Pdgfra (O), Srpr (F), and Vim (Q) gene expression and downregulation of Inpp5f (N) and Rock2 (P) gene expression compared to control mice. Data represent the mean and SEM evaluated by ANOVA and post hoc analysis. DOX, doxorubicin-treated group; RT, hindlimb-radiation-treated group; DOX-RT, doxorubicin- and hindlimb-radiation-treated group. n = 6 mice per group. * p-value < 0.05; ** p-value < 0.01; *** p-value < 0.001.