Thursday, April 17, 2008

Exposure to hyperbaric oxygen --- Cancer

Exposure to hyperbaric oxygen induces cell cycle perturbation in prostate cancer cells.

Authors: Kalns JE , Piepmeier EH
Davis Hyperbaric Laboratory, Brooks Air Force Base, San Antonio, Texas 78235-5119, USA.
In Vitro Cell Dev Biol Anim 1999 Feb;35(2):98-101

Abstract: Cell cycle synchronization of tumor cells by exposure to hyperbaric oxygenation (HBO) may increase the efficacy of chemotherapy or radiation by placing cells into a chemosensitive portion of the cycle. The purpose of the current study was to examine oxygen pressure-dependent relationships with respect to the cell cycle in prostate tumor cells in vitro. LNCaP cells were grown in an incubator at 21% O2 and then exposed to 100% oxygen at pressures up to 6 atmospheres (atm) for 1.5 h. Cells were then returned to the incubator and evaluated for DNA content by propidium iodide and new DNA synthesis with a pulse-chase experiment. Cell cycle effects were evaluated by flow cytometry. Exposure to HBO increased the percentage of cells synthesizing new DNA in a dose-dependent fashion: 0 atm, 44%; 6 atm, 65%. Cells that synthesize new DNA accumulate in G2/M as a function of partial pressure of oxygen. These results suggest that HBO induces cells to enter the cell cycle and accumulate in G2/M. Cell cycle synchronization and entry of senescent cells into the cell cycle suggest that HBO may be a useful adjuvant to chemotherapy or radiation in the treatment of prostate cancer. There are two potential mechanisms of action that may make HBO efficacious in the treatment of prostate cancer. HBO may potentiate cancer chemotherapeutic agents that cause damage to DNA during DNA synthesis or HBO may inhibit cell division causing accumulation in G2/M.

Does hyperbaric oxygen have a cancer-causing or promoting effect? A review of the pertinent literature [see comments]

Authors: Feldmeier JJ , Heimbach RD , Davolt DA , Brakora MJ , Sheffield PJ , Porter AT
Department of Radiation Oncology, Wayne State University, Detroit, Michigan.
Undersea Hyperb Med; 21(4):467-75 1994

Abstract: We reviewed all known published reports or studies related to a possible cancer-causing or growth-enhancing effect by hyperbaric oxygen. Published articles were retrieved using Medline searches for the period 1960-1993. Additional references were obtained from bibliographies included in those articles discovered in the computer search. Also, hyperbaric medicine text books and the published proceedings of international hyperbaric conferences were visually searched. Studies and reports discovered in this fashion and related to the topic were included in the review. Twenty-four references were found: 12 were clinical reports, 11 were animal studies, and 1 reported both an animal study and a clinical report. Three clinical reports suggested a positive cancer growth enhancement, whereas 10 clinical reports showed no cancer growth enhancement. Two animal studies suggested a positive cancer-enhancing effect, and 10 animal studies showed no such effect. (The report that included both animals and humans is counted in both groups). The vast majority of published reports show no cancer growth enhancement by HBO exposure. Those studies that do show growth enhancement are refuted by larger subsequent studies, are mixed studies, or are highly anecdotal. A review of published information fails to support a cancer-causing or growth-enhancing effect by HBO. (44 Refs) review of the pertinent literature [see comments]

In Philadelphia, researchers at the University of Pennsylvania are laying the groundwork for a series of studies to determine how patients with head and neck tumors benefit from breathing pure oxygen before and after surgery.
The breathing treatment, called hyperbaric oxygen therapy (HBOT), is an unconventional method of treating cancer, though HBOT has been used for decades to treat other conditions such as heart problems, carbon monoxide poisoning, non-healing wounds such as severe burns, and scuba diving-related injuries. Breathing additional oxygen is believed to improve the body's ability to kill germs and heal. HBOT patients breathe pure oxygen, which is twice the atmospheric pressure and administered in either of two ways: The patient lies on a stretcher in a sealed, specially pressurized chamber, or inhales the oxygen from a mask or hood while sitting in a specialized chamber.
"Although scientists have known for years that hyperbaric oxygen can reverse tissue damage, there still are a lot of questions to be answered," said Stephen R. Thom, M.D., Ph.D., the center's principal investigator and a professor of emergency medicine at the University. "Our goals are to try to ascertain, under rigorous methods, the mechanisms of action, safety, and clinical efficacy of hyperbaric oxygen, and to develop and validate a model to say who benefits from this treatment."
The researchers at the new Specialized Center of Research in Hyperbaric Oxygen Therapy want to know "how much of an effect"--including on reversal of body tissue damage and on the growth and spread of tumors--HBOT has on people with head and neck tumors who have had radiation treatments, but need surgery again.
Dr. Thom said that previous studies have shown that HBOT can reverse tissue damage, but did not show by how much. A critical component of the clinical trial is that investigators will measure patient's blood vessels throughout the trial to determine if healthy tissue is growing back. The key question, Dr. Thom noted, is, "Do hyperbaric oxygen treatments have an effect on patient outcomes? We think they do, but the study will tell us for sure."

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