| Summary: | 碩士 === 國防醫學院 === 海底醫學研究所 === 98 === Malignant disease is among the leading causes of mortality. Head and neck cancer is the sixth most common cancer in the worldwide. Oral cavity cancer ranked fourth among all cancer deaths of male in Taiwan. Despite of early diagnosis and multi-therapeutic modalities, the overall survival of patients head & neck cancer has not been improved substantially in the last three decades. Recent studies suggest that tumor hypoxia is associated with tumor cell proliferation and invasion. Hypoxia was known to induce production of reactive oxygen species (ROS), which may serve as signaling molecules and/or induce signal transduction. In vitro studies had shown that hypoxia induced DNA incorporation, an implication of increased cellular proliferation. However, there was no actual data showing increased cell number during hypoxia exposure. Our laboratory had previously found that 1% O2 exposure did induce DNA incorporation, however, it inhibited cell growth curve as compared to normoxia group. The current study was aimed to establish an in vitro cell model of hypxia-induced cancer cell proliferation to facilitate the study of underlying mechanisms. The possible involvement of ROS in this process was also investigated. Two head and neck squamous carcinoma cell lines, FADU and SCC25, were cultured in 1% O2, 3% O2, or room air for different periods of time. Cell number was determined by a hemacytometer after trypan blue staining. BrdU assay was applied for detecting DNA incorporation, an indicator of cell proliferation. The levels of superoxide anion and hydrogen peroxide were measured by nitro blue tetrazolium, and by 2,7-dichloridihydrofluorescein diacetate, respectively. The results showed 1% O2 exposure plus serum free pretreatment significantly inhibited cell growth curve. Three percent O2 had less inhibitiory effect. In cells without the serum free pre-treatment, 1% and 3% O2 enhanced cell growth, and BrdU uptake. Increased production of hydrogen peroxide, but not SOD, was noted in both FADU and SCC25 cell lines. When pretreated with catalase, the hypoxia induced FADU cell proliferation was inhibited. In summary, this study has established that 1% or 3% O2 exposure without serum-free pretreatment may stimulate proliferation of head and neck cancer cells in vitro. ROS, especially the hydrogen peroxide, may have an important role in hypoxia induced cancer cell proliferation.
|
|---|
