Hyperbaric Oxygen Therapy (HBO), DNA Damage and Tumor Progression - A Survival Study on a Mice Tumor Model

HBO has been used as an adjuvant to chemo (CT) or radiotherapy (RT) in cancer; however, in our previous work on survival study in small animal mice model, we reported cancer enhancing effect after cessation of the HBO therapy. The present study was designed to understand the underlying molecular mechanism that may be linked to cancer enhancing phenomenon. Tumor bearing C3H mice were subjected to hyperbaric hyperoxia (1.1 bar & 1.2 bar) therapy consequently for 6 days with a day off in between for 3 weeks. Each session comprised of daily 120 minutes of HBO exposure prior to and after being subjected to RT or CT. Another group was subjected to one, two and three weeks of HBO therapy to observe graded response and severity of DNA damage. We observed proportionate increase in the severity of DNA damage and histone modification in the tumor samples when subjected to longer duration of HBO therapy as compared to tumor control. Thus, we suggest that HBO therapy should be given under highly dose controlled condition and with caution, else dual effect of oxygen toxicity and molecular effects may lead to tumor enhancement or recurrence and/or metastasis.