| Background Laryngeal carcinoma is one of the popular carcinoma of head and neck. The standard therapy for it is operation, radiotherapy, chemotherapy. But none of the standard therapy can get satisfied curative effect. Photodynamic therapy(PDT) is a new way for carcinoma treatment, and it's advantage is non-invasiveness, little side effect, combination with other therapy for treatment of carcinoma. In 1994, new photofrin Ⅱ which was new drug for PDT was permitted to be used in clinic and this was the sign that PDT was to be the fourth standard therapy for carcinoma. Photodynamic therapy is treatment modality involving the administration of photosensitizing compound, which selectively accumulates in the hyperproliferative target cells followed by local irradiation with visible light of lesion. Eventually target tissue will be damaged by necrosis and apoptosis.Radiotherapy is a standard therapy for laryngeal carcinoma. But now radiotherapy is only fitted for early stage laryngeal carcinoma but not for extensive infiltrated laryngeal carcinoma or recurrent carcinoma. About half century before Gary LH suggested that hypoxic was the most important reason for carcinoma resistant to the effect of radiation. And followed study in vivo or vitro have confirmed this viewpoint that hypoxic cells require about three times the radiation dose that well-oxygenated cells need to achieve the same degree of cytotoxicity. This leads to more dose radiation in clinical therapy to cure carcinoma. But more dose radiation also lead to more injury for normal tissues. And there is about 15% laryngeal carcinoma patients are resistant to radiation. So how to improve the effect of radiation is being more important for clinical doctors. And radiosensitizer which can enhance tumor inactivation became one of the hot point in recent years.Hypericin(HY) is a new kind of nature photosensitizer which has anti-inflammatory, anti-virus, anti-tumor and enhance immunity activation. And HY is characterized by high absorption around 470nm and high singlet oxygen yield. So we can make a conclusion that using hypericin as photosensitizer should be efficient in treatment of laryngeal carcinoma. Because limitation in light source PDT is uselessness in treatment of great entity tumor. Larynx is composed of cartilage, muscle, ligament and mucosa, so every anatomic site of larynx is small and strength of penetration of light source is powerful. And more excited is that volum of laryngeal carcinoma is always small, so light can easily penetrate it. With the development of laser and light guide fiber, fibrolaryngoscope today is widely used in clinic. And fibrolaryngoscope can be used not only in making diagnosis but also in transporting light. So PDT should be efficient in treatment in laryngeal carcinoma.Early in 1975 scholars had found that hematoporphyrin derivative (HPD) could improve radiation cytotoxicity. Now many studies have proved that hypericin have more biological activation than HPD and other traditional photosensitizer, so HY should have more powerful anti-tumor effect and it may be a ideal anti-tumor agent. Today there is no report bout hypericin as photosensitizer or as radiosensitizer used in basical study or in clinical treatment in domestic. In this study we just want to verify anti-tumor effect of HY by studying effect of HY on human laryngeal squamous cell carcinoma strain Hep-2. If HY dose have powerful effect on Hep-2 cells, so we could explore a new way to treat laryngeal carcinoma.Methods Using techniques of tumor cells culture in vitro, contrast group was set up. The test groups was divided into 4 groups: light irradiation group, no light irradiation group, radiation group, no radiation group. In light irradiation group, Hep-2 cells were exposed to different concentration hypericin as 0, 1.0, 2.0, 3.0μg/ml, then total 10 minutes light irradiation in which light energy was 7.5J/cm2 were given after an hour. In no light irradiation group, Hep-2 cells were exposed to different concentration hypericin as 5.0,10...
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