Methotrexate used in combination with aminolaevulinic acid for photodynamic killing of prostate cancer cells.
Photodynamic therapy (PDT) using 5-aminolaevulinic acid (ALA) to drive production of an intracellular photosensitiser, protoporphyrin IX (PpIX), is a promising cancer treatment. However, ALA-PDT is still suboptimal for thick or refractory tumours. Searching for new approaches, we tested a known inducer of cellular differentiation, methotrexate (MTX), in combination with ALA-PDT in LNCaP cells. Methotrexate alone promoted growth arrest, differentiation, and apoptosis. Methotrexate pretreatment (1 mg l(-1), 72 h) followed by ALA (0.3 mM, 4 h) resulted in a three-fold increase in intracellular PpIX, by biochemical and confocal analyses. After exposure to 512 nm light, killing was significantly enhanced in MTX-preconditioned cells. The reverse order of treatments, ALA-PDT followed by MTX, yielded no enhancement. Methotrexate caused a similar relative increase in PpIX, whether cells were incubated with ALA, methyl-ALA, or hexyl-ALA, arguing against a major effect upon ALA transport. Searching for an effect among porphyrin synthetic enzymes, we found that coproporphyrinogen oxidase (CPO) was increased three-fold by MTX at the mRNA and protein levels. Transfection of LNCaP cells with a CPO-expressing vector stimulated the accumulation of PpIX. Our data suggest that MTX, when used to modulate intracellular production of endogenous PpIX, may provide a new combination PDT approach for certain cancers.
Sinha
A K
AK
Department of Dermatology, Wellman Center for Photomedicine, Harvard Medical School, Boston, MA 02114, USA.
Anand
S
S
Ortel
B J
BJ
Chang
Y
Y
Mai
Z
Z
Hasan
T
T
Maytin
E V
EV
D000622:Aminolevulinic Acid / Q000494:pharmacology*; D017209:Apoptosis; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002470:Cell Survival; D003304:Coproporphyrinogen Oxidase / Q000378:metabolism; D006801:Humans; D008297:Male; D008727:Methotrexate / Q000008:administration & dosage / Q000494:pharmacology*; D015741:Metribolone / Q000494:pharmacology; D008954:Models, Biological; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000494:pharmacology; D011471:Prostatic Neoplasms / Q000628:therapy*; D011524:Protoporphyrins / Q000378:metabolism; D015854:Up-Regulation
D017319:Photosensitizing Agents; D011524:Protoporphyrins; D015741:Metribolone; D000622:Aminolevulinic Acid; C028025:protoporphyrin IX; D003304:Coproporphyrinogen Oxidase; D008727:Methotrexate