Role of Nuclear Factor‐KB in Colon Cancer Cell Apoptosis Mediated by Aminopyropheophorbide Photosensitization

Abstract

Aminopyropheophorbide (APP) is a second generation of photosensitizer for photodynamic therapy (PDT). We demonstrated that APP strongly absorbed red light and, after being taken up by colon cancer cells (HCT-116 cells), was localized in cytoplasmic and internal membranes but not in mitochondria. The APP-mediated photosensitization was cytotoxic for HCT-116 cells through an induction of apoptosis. Indeed, DNA fragmentation (DNA laddering and terminal deoxyuridine nick-end labeling) and chromatin condensation (4',6-diamidine-2'-phenylindole staining) could be visualized soon after photosensitization. Because nuclear factor (NF)-kappa B is involved in the response to many photosensitizers, we also demonstrated its nuclear translocation in two waves: a rapid and transient one, followed by a slow and sustained phase. The NF-kappa B turned out to be involved in an antiapoptotic response to APP-mediated photosensitization because the HCT-116 cell line expressing the dominant negative mutant of inhibitor-kappa B alpha was more sensitive to apoptosis as measured by DNA fragmentation and caspase activation. These data unambiguously show that a membrane-located photosensitizer can lead to effective apoptosis, reinforcing the idea that PDT can be an effective means to eradicate colon cancer cells.

Mechanism of colon cancer cell apoptosis mediated by pyropheophorbide-a methylester photosensitization

“…It is thus likely that the active cellular site for triggering apoptosis mediated by PPME photosensitization is the ER/Golgi system. The absence of co-localization with the mitochondrial probe rhodamine-123 indicates the likelihood that the ER/Golgi is the site from which the apoptotic signal originates (Matroule et al, 1999b). Others have found that photosensitizers localize to a variety of cellular sites including the outer membrane, lysosomes, mitochondria and the nucleus resulting in damage to these structures upon light exposure (Morgan et al, 2000;Oleinick and Evans, 1998).…”

Intracellular signaling mechanisms in photodynamic therapy

“…Interestingly, in this case the activation of NF-nB was proposed to occur by a mechanism independent of the activation of InB kinases and require the activity of a tyrosine kinase [227]. Expression of a dominant negative mutant of InBa increased apoptotic death of HCT-116 cells sensitized with APP [228], suggesting that NF-nB regulates the expression of gene(s) encoding proteins with an anti-apoptotic activity. However, it was not determined whether cells prevented from undergoing apoptosis in the presence of the dominant negative mutant of InBa died by a non-apoptotic mechanism.…”

“…Furthermore, HeLa cells (human cervix carcinoma cells) and T24 cells (human transitional cell carcinoma of the urinary bladder) photosensitized with hypericin also showed a reduction in the cytosolic levels of InBa, which correlated in time with binding of nuclear proteins to the NF-nB site of the cox-2 promoter [145]. The activation of NF-nB and its role in cell death upon photosensitization was investigated using the sensitizer PPME [160,227] and its derivative aminopyropheophorbide (APP) [228], which results from the addition of a positively charged group that increases cellular uptake. PPME-mediated photosensitization of HCT-116 human colon carcinoma cells activated NF-nB by triggering the signaling pathway mediated by the IL-1 receptor.…”

Dihydroartemisinin Accentuates the Anti-Tumor Effects of Photodynamic Therapy via Inactivation of NF-κB in Eca109 and Ec9706 Esophageal Cancer Cells

“…Several studies have indicated that NF-κB activation plays a negative role in PDT. Matroule et al found that the HCT-116 cell line, which expresses a dominant-negative mutant of inhibitor-Iκα, was highly sensitive to apoptosis and indicated that NF-κB activation was involved in an anti-apoptotic response to aminopyropheophorbide (APP)-mediated photosensitization [11]. Furthermore, it has been demonstrated that inhibition of NF-κB improves glioblastoma cell death in response to 5-Aminolevulinic acid (5-ALA)-mediated PDT [12].…”