EACR26-1870

Can photodynamic therapy-conditioning influence the stemness of endometrial cancer stem cells?

B. Serambeque1, G. Neto2, S. Pinto Lopes2, F. Gomide2, M. Carvalho3, M. Pineiro4, M. Botelho5, T. MVD Pinho e Melo4, M. Laranjo5
1Univ Coimbra, Center for Innovative Biomedicine and Biotechnology (CIBB); Univ Coimbra, Coimbra Institute for Clinical and Biomedical Research (iCBR) Area of Environment Genetics and Oncobiology (CIMAGO), Institute of Biophysics, Faculty of Medicine, Coimbra, Portugal
2Univ Coimbra, Coimbra Institute for Clinical and Biomedical Research (iCBR) Area of Environment Genetics and Oncobiology (CIMAGO), Institute of Biophysics, Faculty of Medicine, Coimbra, Portugal
3Univ Coimbra, Coimbra Institute for Clinical and Biomedical Research (iCBR) area of Environment Genetics and Oncobiology (CIMAGO), Institute of Biophysics and Universitary Clinic of Gynecology, Faculty of Medicine; Gynecology Service, Department of Gynecology, Obstetrics, Reproduction and Neonatology, Unidade Local de Saúde de Coimbra, Coimbra, Portugal
4Univ Coimbra, Coimbra Chemistry Centre - Institute of Molecular Sciences and Department of Chemistry, Coimbra, Portugal
5Univ Coimbra, Center for Innovative Biomedicine and Biotechnology (CIBB), Coimbra Institute for Clinical and Biomedical Research (iCBR) Area of Environment Genetics and Oncobiology (CIMAGO), Institute of Biophysics, Faculty of Medicine; Clinical Academic Centre of Coimbra (CACC), Coimbra, Portugal
Introduction:

Photodynamic therapy (PDT), an anticancer treatment that combines a photosensitising molecule, light of a specific wavelength, and molecular oxygen to generate reactive oxygen species, leading to cellular damage, has been investigated as a promising conservative and less invasive approach for endometrial cancer. Despite presenting numerous advantages, PDT can face limitations, including restricted light penetration, limited photosensitiser internalisation, and the presence of hypoxic regions within tumors. To explore how PDT can influence the susceptibility of tumour populations, we evaluated the stemness of endometrial cancer cells surviving PDT.

Material and method:

Two endometrial cancer cell lines, HEC-1-A and ECC-1, were incubated with dihydroxymethyl derivative of tetraphenylchlorin (PX1) and temoporfin, at inhibitory concentration of 50% of metabolic activity, followed by an irradiation after 24 hours (PDT-conditioning). 72 hours later, an optimised sphere-forming protocol was performed to obtain endometrial CSC. After five or seven days, projection area, sphere-forming capacity, self-renewal, and western blot to evaluate the expression of CSC-associated markers were conducted.

Result and discussion:

PDT-conditioning did not alter the sphere-forming capacity of endometrial CSC. However, endometrial CSC seemed to present an increased self-renewal capacity after PDT-conditioning. Nevertheless, PDT-conditioning induced a decrease in the projection area of ECC-1 CSC with both photosensitisers, and in HEC-1-A CSC with PX1. Also, the evaluation of the CSC-associated markers revealed that PDT-conditioning induced a tendency to decrease the Nanog expression in ECC-1 CSC and the SOX2 expression in HEC-1-A CSC with temoporfin. These results suggest that PDT-conditioning may do not change the proportion of stem-like endometrial cells, but can potentiate their self-renewal capacity. Nonetheless, PDT-conditioning seems to interfere with the endometrial CSC proliferative potential.

Conclusion:

Overall, these findings suggest that PDT-conditioning may differentially modulate CSC behaviour and stemness-associated pathways, highlighting a complex CSC response to PDT that motivates further exploration.

Acknowledgement:

FCT supports CIBB (doi:10.54499/UIDB/04539/2020; doi:10.54499/UIDP/04539/2020; doi:10.54499/LA/P/0058/2020; doi:10.54499/UID/04539/2025); CQC (doi:10.54499/UIDB/00313/2020; doi:10.54499/UIDP/00313/2020; TEMA (doi:10.54499/UIDB/00481/2020), UIDP/00481/2020 (doi:10.54499/UIDP/00481/2020); Projects CarboNCT (doi:10.54499/2022.03596.PTDC), Chem4LungCare (doi:10.54499/PTDC/QUI-QOR/0103/2021), and LPCC-NRC - Bolsa Professor Carlos de Oliveira 2025; PhD Scholarship from FCT and European Social Fund to BS (10.54499/2020.07672.BD).