Response to ALA-PDT in 3D ovarian cancer and in vivo models of peritoneal dissemination

CALVO G; RAMÍREZ J ; DI VENOSA G ; ORLANDO G ; GOLA G ; SÁENZ D; CASAS A ; CÉSPEDES M ; TARUSELLI A; HASAN T; URTREGER A

Barcelona

Congreso; 17th Congress of the International Union of Photobiology and 18th Congress of the European Society for Photobiology; 2019

Introduction: ALA-PDT is an effective therapy mainly for dermatologic cancer, although its uses have been extended in the last years. PDT with benzoporphyrin derivatives has been employed in the treatment of ovarian cancer [1]. In addition, Photodiagnosis with ALA for intraoperative detection of peritoneal metastases of ovarian cancer has been proposed [2].When ALA is administered systemically, tumor selective production of Protoporphyrin IX is observed. One approach to broaden clinical ALA-PDT uses is the design of derivatives of ALA with the aim of improving bioavailability and selectivity.Three-dimensional culture models (spheroids) have proven to be a realistic scenario to test response to ALA-PDT, where physical variables reduce tumor response to treatment. On the other hand, 3D tumorspheres are enriched in stem-like cells, which are related to metastasis and resistance. Since ovarian cancer frequently presents peritoneal dissemination, the use of 3D models mimicking peritoneal metastasis, constitutes an interesting approach. The aim of this study was to gain insight in the response of ovarian cancer 3D models to PDT employing ALA or new derivatives, and to analyze its selectivity for tumor tissue in vivo.Materials and methods: SKOV-3 and IGROV-1 human ovarian cancer cell lines were employed. SKOV-3 spheroids were used as metastatic nodules model and IGROV-1 tumorspheres, as tumor stem cells model. Athymic mice N:NIH (S)-Fox1 nu were injected i.p. with SKOV-3 cells to induce peritoneal dissemination. White lamps and a 630 nm laser (Lumiia, Argentina) were employed as light sources. ALA and ALA derivatives synthesised by multicomponent reactions [3] were employed.Results: IGROV-1 tumorspheres overexpressed NANOG, OCT4 and SOX2 pluripotent genes [4] and exhibited 2-fold increase of resistance to ALA-PDT as compared to 2D cultures, thus suggesting a role of ovarian stem cells in the resistance to PDT.The role of the 3D structure on the resistance was studied in spheroid SKOV-3 cultures. They proved to be resistant to ALA-PDT employing low power non-coherent light sources. However, they were responsive to the treatment employing a coherent red light source. In addition to increasing light dose, the other approach to revert resistance to PDT was the use of more lypophilic ALA compounds, of which the so called 89-ALA was the one which better penetrate the spheroid structure.When 89-ALA was injected into mice with i.p. dissemination of SKOV-3 cells, fluorescence was much more confined to the tumor spots in comparison to ALA.Conclusions: The use of ALA derivatives improves ALA-PDT performance in ovarian cancer. Our results reinforce the importance of the studies of pro-photosensitizer penetration and PDT response in 3D models as a previous step to animal studies.