Preclinical translational screening of palladium(II)-porphyrin photosensitizers across human and Oncopig bladder cancer cell lines.

BACKGROUND

Bladder cancer remains a highly recurrent malignancy with limited long-term response to conventional therapies. The development of new treatments is also hindered by the lack of preclinical models that accurately reproduce human disease. In this context, Oncopig-derived models provide a translationally relevant platform for evaluating candidate therapies before progression to in vivo studies.

METHODS

Here, we performed a preclinical in vitro screening of three palladium(II)-porphyrins, 3-Pd(PPh3), 3-Pd(dppf), and 3-Pd(PEPSI), in human (T24, RT4, 5637) and Oncopig-derived bladder cancer cell models. Cytotoxicity was assessed under light and dark conditions using MTT and LIVE/DEAD assays, while intracellular ROS generation was quantified via DCFH-DA fluorescence. Gene expression profiling (qRT-PCR) targeted oxidative stress and apoptosis markers (SOD, CAT, GPx, BAX, BCL2, CASP3/8/9), and nuclear morphology was analyzed using DAPI staining.

RESULTS

All three compounds exhibited light-dependent cytotoxicity with minimal dark toxicity. While 3-Pd(PPh3) and 3-Pd(dppf) demonstrated potent photodynamic activity with nanomolar IC50 values, 3-Pd(PEPSI) showed consistently higher IC50 values across the tested bladder cancer cell lines, indicating lower photodynamic potency under the evaluated conditions. Photoactivation triggered significant ROS production and upregulation of CAT and CASP3, alongside increased BAX/BCL2 ratios, supporting a ROS-mediated apoptotic mechanism. Notably, Oncopig-derived cells exhibited molecular and phenotypic responses closely matching those of human bladder cancer cell lines.

CONCLUSION

These findings support the translational potential of Pd(II)-porphyrins for bladder cancer PDT and position Oncopig-derived in vitro models as a responsible preclinical screening layer to prioritize photosensitizers before future large-animal validation of localized and image-guided PDT strategies.