Rodriguez Lorena, Divenosa Gabriela, Batlle Alcira, Macrobert Alexander, Casas Adriana
Centro de Investigaciones sobre Porfirinas y Porfirias (CIPYP), CONICET and Hospital de Clínicas José de San Martín, University of Buenos Aires, Viamonte 1881 10A, 1056 Buenos Aires, Argentina.
Photochem Photobiol Sci. 2007 Dec;6(12):1306-10. doi: 10.1039/b704235c. Epub 2007 Jun 20.
Aminolevulinic acid (ALA)-based photodynamic therapy (PDT) has been successfully employed in the treatment of certain tumours. Porphyrins endogenously generated from ALA induce tumour regression after illumination with light of an appropriate wavelength. The aim of this work was to compare porphyrin production from ALA and sensitivity to photodynamic treatment in a tumour/normal cell line pair. We employed the HB4a cell line from normal mammary luminal epithelium and its counterpart transfected with the oncogen H-Ras (VAL/12 Ras). After 3 h of exposure to ALA, HB4a-Ras cells produce a maximum of 150 ng porphyrins per 10(5) cells whereas HB4a produce 95 ng porphyrins per 10(5) cells. In addition, HB4a-Ras cells show a plateau of porphyrin synthesis at 1 mM whereas HB4a porphyrins peak at the same concentration, and then decrease quickly. This higher porphyrin synthesis in the tumorigenic cell line does not lead to a higher response to the photodynamic treatment upon illumination. Lethal doses 50, LD(50), determined by MTT assay were 0.015 J cm(-2) and 0.039 J cm(-2) for HB4a and HB4a-Ras respectively after 3 h exposure to 1 mM ALA. The conclusion of this work is that a tumour cell line obtained by transfection of the Ras oncogene, although producing higher porphyrin synthesis from ALA, is more resistant to ALA-PDT than the parental non-tumour line, however the mechanism is not related to photosensitiser accumulation, but very likely to cell survival responses.
基于氨基乙酰丙酸（ALA）的光动力疗法（PDT）已成功应用于某些肿瘤的治疗。ALA内源性生成的卟啉在用适当波长的光照射后可诱导肿瘤消退。本研究的目的是比较肿瘤/正常细胞系对中ALA生成卟啉的情况以及对光动力治疗的敏感性。我们使用了来自正常乳腺腔上皮的HB4a细胞系及其转染了致癌基因H-Ras（VAL/12 Ras）的对应细胞系。在暴露于ALA 3小时后，HB4a-Ras细胞每10⁵个细胞最多产生150 ng卟啉，而HB4a细胞每10⁵个细胞产生95 ng卟啉。此外，HB4a-Ras细胞在1 mM时卟啉合成达到平台期，而HB4a细胞在相同浓度时卟啉达到峰值，然后迅速下降。致瘤细胞系中这种较高的卟啉合成并未导致光照后对光动力治疗有更高的反应。通过MTT法测定，在暴露于1 mM ALA 3小时后，HB4a和HB4a-Ras的半数致死剂量LD₅₀分别为0.015 J/cm²和0.039 J/cm²。本研究的结论是，通过转染Ras致癌基因获得的肿瘤细胞系，尽管从ALA产生更高的卟啉合成，但比亲代非肿瘤细胞系对ALA-PDT更具抗性，然而其机制与光敏剂积累无关，很可能与细胞存活反应有关。
