Differentiation-dependent photodynamic therapy regulated by porphobilinogen deaminase in B16 melanoma

Abstract

Protoporphyrin IX (PpIX) synthesis by malignant cells is clinically exploited for photodiagnosis and photodynamic therapy following administration of 5-aminolevulinic acid (ALA). The expression and activity of the housekeeping porphobilinogen deaminase (PBGD) was correlated to PpIX synthesis in differentiating B16 melanoma cells. Differentiation was stimulated by two inducers, butyrate and hexamethylene bisacetamide (HMBA), both of which promote the formation of typical melanosomes and melanin, as well as morphological changeover. A marked decrease in total PBGD activity and PpIX synthesis was observed following stimulation by butyrate, while HMBA induced an opposite effect. In contrast, ferrochelatase levels remained unchanged. Photodynamic inactivation of the cells undergoing differentiation was largely dependent on the PpIX accumulation, which was modulated by the two inducers butyrate and HMBA. Fluorescence immunostaining with anti-PBGD antibodies revealed a major PBGD fraction in the nucleus and a minor fraction in the cytosol. This nuclear localisation pattern was confirmed by expression of PBGD fused to green fluorescence protein. We suggest that efficient photodynamic therapy of cancer facilitated by ALA administration can be enhanced using combined therapeutic modalities.

Low-Dose Methotrexate Enhances Aminolevulinate-Based Photodynamic Therapy in Skin Carcinoma Cells In vitro and In vivo

“…A third enzyme reported to be rate-limiting in some situations is porphobilinogen deaminase (PBGD). Zvi Malik’s group showed that in cultured B16 melanoma cells, treatment with differentiation-altering agents (HMBA, or butyrate) caused decreases or increases that correlated with enzyme levels and enzyme activity, suggesting that PBGD is rate-limiting in that system (47). Although PBGD message levels by RT-PCR were unchanged after MTX pretreatment in our system (data not shown), we did not have access to a suitable anti-PBGD antibody, so the question of whether MTX affects PBGD remains open.…”

Aloe-emodin as antiproliferative and differentiating agent on human U937 monoblastic leukemia cells

“…Treatment with 10 and 50 μM AE, compared to the control, significantly induced an enhancement of TG activity by about 37% and 140% after 72 h of exposure with the anthraquinone, respectively. PpIX, a compound synthesized during heme biosynthesis, can accumulate to high levels preferentially in differentiated cells (Ortel et al, 2002) and it has been recently considered a differentiation indicator for some cancer cell lines (Ickowicz-Schwartz et al, 2004). The effect of AE on intracellular accumulation of PpIX in U937 cells is shown in Table 1, where the concentration of intracellular PpIX significantly increased after the treatments.…”

Protoporphyrin IX Level Correlates with Number of Mitochondria, But Increase in Production Correlates with Tumor Cell Size

“…It has been illustrated that neoplastic cell lines produce more PpIX when in the plateau growth phase than in the exponential growth phase following the administration of ALA, and the opposite was found to be true in nonneoplastic cell lines; however, no correlation between growth rate and PpIX production was seen for either neoplastic or nonneoplastic cells (22). Cellular differentiation therapy has been shown to increase PpIX production when applied to cells for short periods of time prior to incubation with ALA (24,25). Cell size was found to have a slight positive correlation to PpIX production, with larger cells showing higher production of PpIX in the two cell lines studied (26).…”