Purpose: Tumor drug resistance limits the response to chemotherapy. Interestingly, sequential combination therapy enhances the anticancer efficacy of drugs like cisplatin (CDDP) via synergistic effects. We assayed the synergistic effects of combined photodynamic therapy programmed death receptor-ligand 1 (PDT) and chemotherapy in malignant Hep-2 cells.
Methods: In the cultured Hep-2 cells, meta-tetra(hydroxyphenyl)chlorin (m-THPC) and CDDP were administered separately or in combination. The cellular viability and apoptosis were assessed, accompanied by measurement of the expression of Bax, Bcl-2, ATG-7, and LC3 (LC3-I and LC3-II). Additionally, nuclear chromatin changes, drug retention, and PD-L1 expression were further investigated following different treatments.
Results: The sequential treatment significantly diminished cell viability and induced cell apoptosis, in consistency with the usage of single therapeutic strategies, as reflected by an increase in Bax expression and decrease of Bcl-2 expression. Moreover, ATG-7 and LC3-II/LC3-I ratio were reduced after administration of the sequential treatment. Synergetic effect of nuclear chromatin configuration, negative effects of cellular drug retention, and a decrease in PD-L1 expression were observed following the sequential treatment.
Conclusion: The application of sequential treatment of PDT in combination with chemotherapy offers a promising therapeutic option for cancer treatment, by regulating the PD-L1 expression, autophagy, and non-mitochondrial pathways.
Keywords: photodynamic therapy, sequential treatment, chemotherapy, PD-L1, Hep-2 cell