Hyperbaric oxygen therapy increases the effect of 5-fluorouracil chemotherapy on experimental colorectal cancer in mice

Abstract

Tumor hypoxia may compromise the results of chemotherapy for treating colorectal cancer because it stimulates angiogenesis and the release of tumor growth factors. Hyperbaric oxygen (HBO) supplementation may potentiate the effects of chemotherapy in such cases. This study aimed to assess the effect of HBO therapy combined with chemotherapy on the treatment of colorectal cancer in mice. C57BL6 mice were submitted to the intrarectal instillation of N-methyl-N-nitrosoguanidine (MNNG) and treated with 5-fluorouracil (5FU) and/or HBO therapy. The MNNG group presented the highest dysplastic crypt rate. The 5FU + HBO group presented the highest rate of apoptotic cells per dysplastic crypt. The 5FU group presented the highest expression of hypoxia-inducible factor-1 alpha and CD44. HBO therapy increased the effect of 5FU on the treatment of the experimental colorectal neoplasia in mice.

Figure 1

Experiment design. Note: * Normal saline solution was applied intraperitoneally at weeks 12 and 13, and the mice were confined in the hyperbaric chamber without pressurization for the time corresponding to one HBO therapy session. ** They were confined in the hyperbaric chamber without pressurization. 5FU: 5-Fluorouracil; HBO: hyperbaric oxygen; MNNG: N-methyl-N-nitrosoguanidine.

Figure 2

Experimental hyperbaric chamber. Note: a: Animal entrance opening; b: manometer; c: tube to connect to the oxygen; d: oxygen outlet valve; e: display for observing the session measuring 15 cm in diameter.

Figure 3

HBO therapy reduces the dysplastic crypt rate in 5FU-treated colorectal cancer mice. Note: Data are expressed as mean ± SEM (n = 15, 10, 10, 10). *P < 0.05 (one-way analysis of variance followed by Bonferroni’s post-hoc test). 5FU: 5-Fluorouracil; HBO: hyperbaric oxygen; MNNG: N-methyl-N-nitrosoguanidine.

Figure 4

HBO therapy increases the apoptotic cell rate in 5FU-treated colorectal cancer mice. Note: Data are expressed as mean ± SEM (n = 15, 10, 10, 10). ****P < 0.0001 (one-way analysis of variance followed by Bonferroni’s post-hoc test). 5FU: 5-Fluorouracil; HBO: hyperbaric oxygen; MNNG: N-methyl-N-nitrosoguanidine.

Figure 5

HBO therapy reduces the rate of HIF-1α- and CD44-positive cells in 5FU-treated colorectal cancer mice. Note: (A) HIF-1α-positive cells (arrow) in rectal neoplasias. A1–4: MNNG, 5FU, HBO, and 5FU + HBO groups. (B) Quantitative results of HIF-1α-positive cells in A. (C) CD44-positive cells (arrow) in rectal neoplasias. Scale bars: 20 μm. C1–4: MNNG, 5FU, HBO, and 5FU + HBO groups. (D) Quantitative results of CD44- positive cells in C. Data are expressed as mean ± SEM (n = 15, 15, 10, 10, 10). ****P < 0.0001 (one-way analysis of variance followed by Bonferroni’s post-hoc test). 5FU: 5-Fluorouracil; HBO: hyperbaric oxygen; HIF-1α: hypoxia-inducible factor-1 alpha; MNNG: N-methyl-N-nitrosoguanidine.