Enhanced killing of SCC17B human head and neck squamous cell carcinoma cells after photodynamic therapy plus fenretinide via the de novo sphingolipid biosynthesis pathway and apoptosis.
Because photodynamic therapy (PDT) alone is not always effective as an anticancer treatment, PDT is combined with other anticancer agents for improved efficacy. The clinically-relevant fenretinide [N-(4-hydroxyphenyl) retinamide; 4HPR], was combined with the silicon phthalocyanine photosensitizer Pc4-mediated PDT to test for their potential to enhance killing of SCC17B cells, a clinically-relevant model of human head and neck squamous cell carcinoma. Because each of these treatments induces apoptosis and regulates the de novo sphingolipid (SL) biosynthesis pathway, the role of ceramide synthase, the pathway-associated enzyme, in PDT+4HPR-induced apoptotic cell death was determined using the ceramide synthase inhibitor fumonisin B1 (FB). PDT+4HPR enhanced loss of clonogenicity. zVAD-fmk, a pan-caspase inhibitor, and FB, protected cells from death post-PDT+4HPR. In contrast, the anti-apoptotic protein Bcl2 inhibitor ABT199 enhanced cell killing after PDT+4HPR. Combining PDT with 4HPR led to FB-sensitive, enhanced Bax associated with mitochondria and cytochrome c redistribution. Mass spectrometry data showed that the accumulation of C16-dihydroceramide, a precursor of ceramide in the de novo SL biosynthesis pathway, was enhanced after PDT+4HPR. Using quantitative confocal microscopy, we found that PDT+4HPR enhanced dihydroceramide/ceramide accumulation in the ER, which was inhibited by FB. The results suggest that SCC17B cells are sensitized to PDT by 4HPR via the de novo SL biosynthesis pathway and apoptosis, and imply potential clinical relevance of the combination for cancer treatment.
Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, Detroit, MI 48201, USA.
Nithin B
NB
Boppana
Department of Physiology, McGill University, Montreal, QC H3G 1YC, Canada.
Ursula
U
Stochaj
Department of Physiology, McGill University, Montreal, QC H3G 1YC, Canada.
Mohamed
M
Kodiha
Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29425, USA.
Alicja
A
Bielawska
Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29425, USA.
Jacek
J
Bielawski
Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29425, USA.
Jason S
JS
Pierce
British Columbia Cancer Agency, Vancouver, BC V5Z 1L3, Canada.
Mladen
M
Korbelik
Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, Detroit, MI 48201, USA.
Duska
D
Separovic
D016588:Anticarcinogenic Agents / Q000627:therapeutic use*; D017209:Apoptosis / Q000187:drug effects*; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy / Q000473:pathology*; D003131:Combined Modality Therapy; D017313:Fenretinide / Q000627:therapeutic use*; D006258:Head and Neck Neoplasms / Q000188:drug therapy / Q000473:pathology*; D006801:Humans; D018613:Microscopy, Confocal; D010778:Photochemotherapy / Q000379:methods*; D021241:Spectrometry, Mass, Electrospray Ionization; D013107:Sphingolipids / Q000096:biosynthesis*; D014407:Tumor Cells, Cultured; D014410:Tumor Stem Cell Assay / Q000379:methods*
D016588:Anticarcinogenic Agents; D013107:Sphingolipids; D017313:Fenretinide