Development of photodynamic therapy to early stage oral cancer using drug delivery system

使用血卟啉衍生物（HPD）和光辐射的光动力疗法（PDT）在对抗早期癌症方面具有很高的有效性。我们已经研究了将这种疗法应用于口腔癌的治疗，对各种类型的培养的口腔癌细胞进行了研究。鳞状细胞癌（SCC）与唾液腺源性腺癌细胞（SAC）相比，对PDT具有较高的敏感性。很明显，与鳞状细胞癌相比，SAC表现出更高水平的还原型谷胱甘肽和谷胱甘肽过氧化物酶活性。对PDT敏感性降低的SCC表现出极高水平的谷胱甘肽s转移酶活性。因此，谷胱甘肽级联的功能是决定细胞光敏性的因素。此外，与SAC相比，SCC表现出细胞内药物水平的增加。因此，我们对两种细胞在无血清培养下的细胞膜脂质组成进行了研究。可见，SCC膜脂60%为磷脂（PL）， SAC膜脂80%为中性脂（NL）。NL/PL比值表明SCC水平较低，而SAC水平显著较高。这些结果表明，PDT的细胞毒性与细胞内药物水平有关，这是由膜疏水性的差异引起的。因此，我们设计了与鳞状细胞癌细胞膜脂质组成相当的脂质体，构建了脂质体包裹的抗癌药物，并通过生长试验检测了鳞状细胞癌和囊状细胞癌对该脂质体的敏感性。结果，脂质体包裹的药物与单独药物或药物-脂质体混合物相比，对SCC表现出增强的细胞毒性。

Photodynamic therapy (PDT) using both hematoporphyrin derivative (HPD) and photoradiation has had a high rate of effectiveness in combatting early stage cancers. We have studied, to apply this therapy to treatment of oral cancer, on verious type of cultured carcinoma cells derived from oral cancers.It has been revealed that squamous cell carcinoma cells (SCC) exhibited high sensitivity to PDT in comparison with salivary gland-derived adenocarcinoma cells (SAC). It became clear that SAC exhibited an increased level of reduced glutathion and glutathion peroxidase activity in comparison to those of SCC.The SCC which showed decreased sensitivity to PDT, exhibited a extremerly high level of glutathion S-transferase activity. Consequenly, the function of glutathion cascade were factors determining photosensitivity of the cells. In addition, the SCC demonstrated an increased intracellular level of drug compare to that SAC.So we have investigated lipid composition of cell-membrane of both cells under serum-free culture. It became evident that 60% of membrane lipids of SCC was phospholipids (PL) and 80% of those of SAC was neutral lipids (NL). The NL/PL ratio indicated that SCC showed low levels but SAC showed remarkably high levels. These result indicated that the cytotoxity of PDT correlated with the intracellular levels of drug resulted from the difference of membrane hydrophobicity.Thus, we have designed liposome which is comparable to the lipid composition of SCC cell membrane, constructed the liposome-entrapped anti-cancer drugs and examined sensitivity to this liposome of both SCC and SAC by growth assay. As the result, the liposome-entrapped drug exhibited enhanced cytotoxicity on SCC compare to either drug alone or drug-liposome mixture.