Transcutaneous carbon dioxide application suppresses bone destruction caused by breast cancer metastasis

Abstract

Hypoxia plays a significant role in cancer progression, including metastatic bone tumors. We previously reported that transcutaneous carbon dioxide (CO2) application could decrease tumor progression through the improvement of intratumor hypoxia. Therefore, we hypothesized that decreased hypoxia using transcutaneous CO2 could suppress progressive bone destruction in cancer metastasis. In the present study, we examined the effects of transcutaneous CO2 application on metastatic bone destruction using an animal model. The human breast cancer cell line MDA-MB-231 was cultured in vitro under three different oxygen conditions, and the effect of altered oxygen conditions on the expression of osteoclast-differentiation and osteolytic factors was assessed. An in vivo bone metastatic model of human breast cancer was created by intramedullary implantation of MDA-MB-231 cells into the tibia of nude mice, and treatment with 100% CO2 or a control was performed twice weekly for two weeks. Bone volume of the treated tibia was evaluated by micro-computed tomography (µCT), and following treatment, histological evaluation was performed by hematoxylin and eosin staining and immunohistochemical staining for hypoxia-inducible factor (HIF)-1α, osteoclast-differentiation and osteolytic factors, and tartrate-resistant acid phosphatase (TRAP) staining for osteoclast activity. In vitro experiments revealed that the mRNA expression of RANKL, PTHrP and IL-8 was significantly increased under hypoxic conditions and was subsequently reduced by reoxygenation. In vivo results by µCT revealed that bone destruction was suppressed by transcutaneous CO2, and that the expression of osteoclast-differentiation and osteolytic factors, as well as HIF-1α, was decreased in CO2-treated tumor tissues. In addition, multinucleated TRAP-positive osteoclasts were significantly decreased in CO2-treated tumor tissues. Hypoxic conditions promoted bone destruction in breast cancer metastasis, and reversal of hypoxia by transcutaneous CO2 application significantly inhibited metastatic bone destruction along with decreased osteoclast activity. The findings in this study strongly indicated that transcutaneous CO2 application could be a novel therapeutic strategy for treating metastatic bone destruction.

Impacts of Hypoxia on Osteoclast Formation and Activity: Systematic Review

“…In their work, the mice had hypoxia stress (8% O 2 ) for 10 h followed by 3 h of reoxygenation. The induction of hypoxia condition to tissues in a study by Takemori et al (2019) was unique compared to the others since it did not involve manipulating O 2 content in the air but through applying CO 2 hydrogel to corresponding tissue [ 24 ]. The number of animals used per group in these four studies ranged from six to 10.…”

“…N/BS), and the number of osteoclasts/total area (N. Oc/TA) [ 22 , 23 ]. On the other hand, osteoclast formation following hypoxia was also assessed based on the number of osteoclasts in the femur following TRAP [ 20 , 24 ]. In determining the impact of hypoxia on bone resorption systemically, the levels of bone resorption marker, C-telopeptide of type-1 collagen (CTX-I), in serum was measured [ 20 , 23 ].…”

A novel topical treatment for bone metastases using a gelatin hydrogel incorporating cisplatin as a sustained release system

“…[32][33][34][35] Although this model has been instrumental in revealing molecular mechanisms underlying metastatic processes and translational studies for drug development, several problems remain because of its requirement for high technical proficiency to exactly insert a syringe needle into the left ventricle of a mouse, which causes severe cardiac stress and rapid mortality. 36,37 In the current study, we employed an intratibial injection model 38,39 because it is technically simple and suitable to investigate the longterm effects of drugs. Second, we found that GM-CDDP exerted strong antitumor effects in the bone metastatic mouse model using MDA-MB-231 human breast cancer cells, but we used only one breast cancer cell line in the present study.…”

Topical cutaneous application of carbon dioxide via a hydrogel for improved fracture repair: results of phase I clinical safety trial

“…Another example relates to the effects of this therapy on tumors. CO 2 therapy has been demonstrated to have inherent antitumor effects [30–33] by suppressing metastasis [33, 34], enhancing the antitumor effect of radiation therapy [35, 36], and suppressing bone destruction caused by bone metastasis [37]. All of these are targets that warrant further examination in clinical trials.…”