Suppression of rat tumor colonies in the lung by oxygen at high pressure is a local effect

Oxygen-dependent regulation of tumor growth and metastasis in human breast cancer xenografts

Background

Tumor hypoxia is relevant for tumor growth, metabolism, resistance to chemotherapy and metastasis. We have previously shown that hyperoxia, using hyperbaric oxygen treatment (HBOT), attenuates tumor growth and shifts the phenotype from mesenchymal to epithelial (MET) in the DMBA-induced mammary tumor model. This study describes the effect of HBOT on tumor growth, angiogenesis, chemotherapy efficacy and metastasis in a triple negative MDA-MB-231 breast cancer model, and evaluates tumor growth using a triple positive BT-474 breast cancer model.

Materials and methods

5 x 10⁵ cancer cells were injected s.c. in the groin area of NOD/SCID female mice. The BT-474 group was supplied with Progesterone and Estradiol pellets 2-days prior to tumor cell injection. Mice were divided into controls (1 bar, pO₂ = 0.2 bar) or HBOT (2.5 bar, pO₂ = 2.5 bar, 90 min, every third day until termination of the experiments). Treatment effects were determined by assessment of tumor growth, proliferation (Ki67-staining), angiogenesis (CD31-staining), metastasis (immunostaining), EMT markers (western blot), stromal components collagen type I, Itgb1 and FSP1 (immunostaining) and chemotherapeutic efficacy (5FU).

Results

HBOT significantly suppressed tumor growth in both the triple positive and negative tumors, and both MDA-MB-231 and BT-474 showed a decrease in proliferation after HBOT. No differences were found in angiogenesis or 5FU efficacy between HBOT and controls. Nevertheless, HBOT significantly reduced both numbers and total area of the metastastatic lesions, as well as reduced expression of N-cadherin, Axl and collagen type I measured in the MDA-MB-231 model. No change in stromal Itgb1 and FSP1 was found in either tumor model.

Conclusion

Despite the fact that behavior and prognosis of the triple positive and negative subtypes of cancer are different, the HBOT had a similar suppressive effect on tumor growth, indicating that they share a common oxygen dependent anti-tumor mechanism. Furthermore, HBOT significantly reduced the number and area of metastatic lesions in the triple negative model as well as a significant reduction in the EMT markers N-cadherin, Axl and density of collagen type I.

Effects of hyperbaric oxygen therapy on tumor growth in murine model of PC-3 prostate cancer cell line

OBJECTIVES

To test the hypothesis that hyperbaric oxygen (HBO) has no effect on tumor growth in a murine model of indolent in vivo prostate cancer. HBO means breathing pure (100%) oxygen under increased atmospheric pressure.

METHODS

Human prostate PC-3 cells were injected into 40 severe combined-immunodeficient mice. They were randomized to undergo 20 sessions of either HBO or normobaric air in standardized conditions and observed for 4 weeks before histologic assessment of any palpable tumors that had developed. The analysis of the developed PC-3 tumors included tumor volume, microvessel density, apoptosis-associated markers (ie, p53, p27), and the proliferative index (Ki-67).

RESULTS

The exposure to HBO at 2 atm for 20 treatment sessions, which comprised a daily 90-minute session, 5 d/wk, had no effect on the prostate cancer volume (P > .05). No differences were observed in tumor microvessel density, proliferative index, or apoptosis markers compared with the non-HBO group (P > .05).

CONCLUSIONS

HBO did not have a tumor stimulatory effect on prostate cancer and could potentially be used safely in conjunction with other therapeutic modalities.

Hyperbaric oxygen therapy for malignancy: a review

One unique feature of tumors is the presence of hypoxic regions, which occur predominantly at the tumor center. Hypoxia has a major impact on various aspects of tumor cell function and proliferation. Hypoxic tumor cells are relatively insensitive to conventional therapy owing to cellular adaptations effected by the hypoxic microenvironment. Recent efforts have aimed to alter the hypoxic state and to reverse these adaptations to improve treatment outcome. One way to increase tumor oxygen tensions is by hyperbaric oxygen (HBO) therapy. HBO therapy can influence the tumor microenvironment at several levels. It can alter tumor hypoxia, a potent stimulus that drives angiogenesis. Hyperoxia as a result of HBO also produces reactive oxygen species, which can damage tumors by inducing excessive oxidative stress. This review outlines the importance of oxygen to tumors and the mechanisms by which tumors survive under hypoxic conditions. It also presents data from both experimental and clinical studies for the effect of HBO on malignancy.

The effect of hyperbaric oxygen therapy on tumour growth in a mouse model of colorectal cancer liver metastases

BACKGROUND AND AIMS

Hyperbaric oxygen (HBO) therapy involves the administration of 100% oxygen at high pressure. It has been used to treat a variety of conditions including non-healing wounds, carbon monoxide poisoning, and as an adjuvant to radiotherapy or chemotherapy. The effect of HBO alone on the growth of malignancy remains controversial. This study investigates the impact of HBO on tumour growth, kinetics and microcirculation of colorectal cancer liver metastases in an experimental model.

METHODS

Male CBA mice were induced with colorectal liver metastases via an intrasplenic injection of a murine derived colorectal cell line. Tumours were examined using quantitative stereological analysis, histology and scanning electron microscopy of microvascular resin casts. The effect of HBO on tumour proliferation and apoptosis was quantified using immunohistochemistry.

RESULTS

Daily exposure to HBO at 2.4 atm for 90 min had no effect on the volume of liver metastases. At day 13, HBO caused a significant reduction in tumour necrosis and proliferation compared to the non-HBO group (p=0.002 and p=0.008, respectively). By day 25 however, no differences were observed (p>0.05). No differences in apoptosis or microvascular architecture were observed.

CONCLUSION

HBO did not have a tumour stimulatory effect on colorectal liver metastases and may potentially be used safely in conjunction with other therapeutic treatment modalities.

Hyperbaric oxygen alone or combined with 5-FU attenuates growth of DMBA-induced rat mammary tumors

We tested the hypothesis that hyperbaric oxygen (HBO) alone and with chemotherapy (5-FU) attenuates tumor growth of DMBA-induced tumors in rats. Six series were performed: (1) Controls (air and vehicle 0.9% NaCl i.p.), (2) 5-FU (0.2 mg/kg i.p.), (3) HBO (2 bar for 90 min and vehicle), (4) HBO and 5-FU, (5) HBO (11 days) and air (next 12 days), (6) HBO (23 days). All treatments were applied on days 1, 4, 7, 10 (Series 1-4), as well as on days 14, 17 and 23 (Series 5-6). Tumor diameter increased by 76.7 and 41.2% in untreated controls and in the 5-FU group, respectively, after 10 days. Tumor size fell by 17-24.2% in the HBO groups and by 35.5% when combined with 5-FU (P < 0.05 compared to HBO). HBO treatment reduced the total number of blood vessels in the tumors. After completion of HBO treatment tumor size increased, but statistically insignificant, during the next 12 days.