Journal
BIOMEDICINE & PHARMACOTHERAPY
Volume 155, Issue -, Pages -Publisher
ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER
DOI: 10.1016/j.biopha.2022.113678
Keywords
ATRA; Carcinoma; Photodynamic therapy; Apoptosis; Unfolded protein response; Experimental cancer therapeutics
Funding
- South-Eastern Norway Regional Health Authority [2017068, 2016023]
- Norwegian Radium Hospital Research Foundation [FU0803, SE2101]
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Combining short-term low-dose all-trans retinoic acid (ATRA) with photodynamic therapy (PDT) can enhance the treatment of solid tumors by inducing apoptosis and activating multiple signaling pathways.
The vitamin A metabolite all-trans retinoic acid (ATRA; tretinoin) has anticancer potential. However, lack of clinical success has prevented its approval for solid tumours. Herein, we propose combining short-term low-dose ATRA with fimaporfin-based photodynamic therapy (ATRA+PDT) for the improved treatment of solid cancers. Compared to monotherapies, ATRA+PDT induced synergistic cytotoxic responses including promotion of apoptosis in colon and breast carcinoma cell lines. Neither enhanced activity of alkaline phosphatase (ALP) nor increased expression of CD133 was detected after ATRA treatment indicating that the improved therapeutic effect of ATRA+PDT is independent of the differentiation state of the cancer cells. In the human colorectal adenocarcinoma cell line HT-29, the effect of ATRA+PDT on gene expression was evaluated by RNA sequencing (RNA-seq). We identified 1129 differentially expressed genes (DEGs) after ATRA+PDT compared to PDT. In-genuity Pathway Analysis (IPA) predicted the unfolded protein response (UPR), interferon (IFN) signaling and retinoic acid-mediated apoptosis signaling as strongly activated canonical pathways after ATRA+PDT compared to PDT. A validation of the RNA-sec data by RT-qPCR revealed that ATRA+PDT elevated mRNA expression of early growth response 1 (EGR1) and strongly the stress-induced activating transcription factor 3 (ATF3), of which was confirmed on the protein level. In addition, ATRA+PDT abolished mRNA expression of regenerating islet-derived protein 4 (REG4). During the first 20 days post-ATRA+PDT, we obtained significant anti-tumour responses in HT-29 xenografts, including complete responses in 2/5 mice. In conclusion, ATRA+PDT repre-sent a novel combination therapy for solid tumours that should be further tested in immunocompetent preclinical models.
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