Steinbach P, Kriegmair M, Baumgartner R, Hofstädter F, Knüchel R
Institute of Pathology, University of Regensburg, Germany.
Urology. 1994 Nov;44(5):676-81. doi: 10.1016/s0090-4295(94)80203-3.
For photodynamic therapy 5-aminolevulinic acid is an attractive compound, since it is a physiologic endogenous substance, and its application in excess results in the accumulation of the metabolite protoporphyrin IX, a very effective photosensitizer. The topical application of 5-aminolevulinic acid in the urinary bladder led to pronounced fluorescence in neoplasias when excited with violet laser light during cystoscopy. The aim of this study was the determination of the transmural distribution of protoporphyrin IX in order to estimate potential efficacy and side effects of a therapeutic application of 5-aminolevulinic acid.
5-Aminolevulinic acid was instilled prior to cystoscopy and biopsies were taken of lesions that were either fluorescing or nonfluorescing. Fluorescence distribution was analyzed by fluorescence microscopy on cryostat sections prepared from 72 biopsy specimens. In addition, multicellular spheroids grown from tumor cells and fibroblasts were exposed to 5-aminolevulinic acid and analyzed accordingly.
Biopsy preparations showed that the fluorescence of protoporphyrin IX was limited to normal and neoplastic urothelial cells. Clinical findings were supported by the in vitro data, which showed negative protoporphyrin IX fluorescence in fibroblasts.
Thus, 5-aminolevulinic acid might be superior in selective accumulation to conventional sensitizers known to localize also in endothelial cells of the tumor stroma. The data appear to hold great promise for 5-aminolevulinic acid in photodynamic diagnosis and therapy in bladder cancer, as phototoxicity will be limited to mucosal lesions. Bladder shrinkage due to photodamage of subepithelial structures even in case of high light doses is not expected.
对于光动力疗法而言，5-氨基酮戊酸是一种有吸引力的化合物，因为它是一种生理性内源性物质，过量应用会导致代谢产物原卟啉IX的积累，原卟啉IX是一种非常有效的光敏剂。膀胱内局部应用5-氨基酮戊酸后，在膀胱镜检查时用紫光激光激发，肿瘤组织会发出明显的荧光。本研究的目的是确定原卟啉IX的透壁分布，以评估5-氨基酮戊酸治疗应用的潜在疗效和副作用。
在膀胱镜检查前滴注5-氨基酮戊酸，对有荧光或无荧光的病变进行活检。通过荧光显微镜对从72份活检标本制备的低温切片进行荧光分布分析。此外，将由肿瘤细胞和成纤维细胞培养的多细胞球体暴露于5-氨基酮戊酸并进行相应分析。
活检制剂显示原卟啉IX的荧光仅限于正常和肿瘤性尿路上皮细胞。体外数据支持临床发现，体外数据显示成纤维细胞中原卟啉IX荧光呈阴性。
因此，5-氨基酮戊酸在选择性聚集方面可能优于已知也定位于肿瘤基质内皮细胞的传统敏化剂。这些数据似乎为5-氨基酮戊酸在膀胱癌的光动力诊断和治疗中带来了巨大希望，因为光毒性将仅限于粘膜病变。即使在高光剂量情况下，预计也不会因上皮下结构的光损伤而导致膀胱收缩。
