Combined effects of exercise and immuno-chemotherapy treatments on tumor growth in MC38 colorectal cancer-bearing mice

Abstract

Acute exercise induces transient modifications in the tumor microenvironment and has been linked to reduced tumor growth along with increased infiltration of immune cells within the tumor in mouse models. In this study, we aimed to evaluate the impact of acute exercise before treatment administration on tumor growth in a mice model of MC38 colorectal cancer receiving an immune checkpoint inhibitor (ICI) and chemotherapy. Six-week-old mice injected with colorectal cancer cells (MC38) were randomized in 4 groups: control (CTRL), immuno-chemotherapy (TRT), exercise (EXE) and combined intervention (TRT/EXE). Both TRT and TRT-EXE received ICI: anti-PD1-1 (1 injection/week) and capecitabine + oxaliplatin (5 times a week) for 1 week (experimentation 1), 3 weeks (experimentation 2). TRT-EXE and EXE groups were submitted to 50 minutes of treadmill exercise before each treatment administration. Over the protocol duration, tumor size has been monitored daily. Tumor growth and microenvironment parameters were measured after the intervention on Day 7 (D7) and Day 16 (D16). From day 4 to day 7, tumor volumes decreased in the EXE/TRT group while remaining stable in the TRT group (p=0.0213). From day 7 until day 16 tumor volume decreased with no significant difference between TRT and TRT/EXE. At D7 the TRT/EXE group exhibited a higher total infiltrate T cell (p=0.0118) and CD8+ cytotoxic T cell (p=0.0031). At D16, tumor marker of apoptosis, vascular integrity and inflammation were not significantly different between TRT and TRT/EXE. Our main result was that acute exercise before immuno-chemotherapy administration significantly decreased early-phase tumor growth (D0 to D4). Additionally, exercise led to immune cell infiltration changes during the first week after exercise, while no significant molecular alterations in the tumor were observed 3 weeks after exercise.

Keywords: acute exercise; cancer immunotherapy; colorectal cancer; immune cell; immune check point inhibitor.

Figure 1

Experimental design and tumor volume change and post intervention intratumoral immune cell infiltration in Experiment 1 (A) Experimental study design. N=20 mice/group (B) The average fold changes in tumor volume at each measurement were calculated as follows: the ratio of the tumor volume on the corresponding day to the tumor volume on day 0 (Mean ± SEM) (C-F) Flow cytometric characterization of MC38 tumor infiltrating immune cell populations: proportion of total in immune infiltration CD45+ cells (C), proportion of total lymphocyte infiltration CD3+ cells on total CD45+ cells (CD45+CD3⁺) (D), proportion of CD4+ T cells on CD3+ (CD45+CD3+CD4⁺) (E), proportion of CD8+ T cells on CD3+ (CD45+CD3+CD8⁺) (F) **p<0.01, *p<0.05, TRT: Treatment; EXE: Exercise.

Figure 2

Design and tumor volume change of Experiment 2 (A) Experimental study design. N=20 mice/group (B) The average fold changes in tumor volume at each measurement were calculated as follows: the ratio of the tumor volume on the corresponding day to the tumor volume on day 0 (Mean ± SEM). All data are presented as mean ± SEM. *p<0.05. TRT: Treatment; EXE: Exercise.

Figure 3

Tumor apoptosis, inflammation, vascular permeability, and growth after 16 days of treatment and exercise (A, B) Western blot analysis. Representative and quantification of western blots for cCASP3, GAPDH, pAKT and Akt. (C) mRNA expression of angiopoietin-1 (ANGPT1), angiopoietin-2 (ANGPT2), Tumor Necrose Factor alpha (Tnfa), Interleukin 6 (IL6), (CHOP) and Interleukin 2 receptor beta chain (IL2rb) in the tumor. (D) ANGPT2: ANGPT 1 ratio. Data are represented as means ± SEM. *p<0.05. TRT: Treatment; EXE: Exercise.