Photodynamic therapy induces rapid cell death by apoptosis in L5178Y mouse lymphoma cells.
The mode of cell death of two strains of mouse lymphoma L5178Y cells was studied following photodynamic therapy (PDT) sensitized by chloroaluminum phthalocyanine. Strains LY-R and LY-S differ in their relative sensitivities to UVC radiation, X-radiation, and PDT; both responded to PDT by undergoing apoptosis. The DNA was degraded into fragments with lengths which are multiples of approximately 180-190 base pairs (i.e., oligonucleosome size), a biochemical marker of apoptosis. The DNA fragmentation was dose and time dependent which indicates this response to be an enzymic process related to cell killing. Cycloheximide, a protein synthesis inhibitor, and actinomycin D, an RNA synthesis inhibitor, enhanced the endonucleolytic DNA fragmentation. Transmission electron microscopy revealed chromatin condensation around the periphery of the nucleus, which is also characteristic of apoptosis. The induction of apoptosis in L5178Y cells by PDT was rapid, with marked degradation of DNA occurring in as little as 30 min. The rapidity of the response to PDT suggests that cellular damage produced by PDT can directly activate endonucleolysis and chromatin condensation, thereby by-passing many of the early steps in the signal transduction program which are acted upon by other agents causing apoptosis.
Department of Radiology, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106.
M L
ML
Agarwal
M E
ME
Clay
E J
EJ
Harvey
H H
HH
Evans
A R
AR
Antunez
N L
NL
Oleinick
D000535:Aluminum / Q000494:pharmacology*; D000818:Animals; D016923:Cell Death / Q000187:drug effects* / Q000528:radiation effects; D002843:Chromatin / Q000187:drug effects / Q000528:radiation effects / Q000648:ultrastructure; D004249:DNA Damage; D004273:DNA, Neoplasm / Q000187:drug effects / Q000528:radiation effects; D007211:Indoles / Q000494:pharmacology*; D007940:Leukemia L5178; D051379:Mice; D008854:Microscopy, Electron; D009942:Organometallic Compounds / Q000494:pharmacology*; D010778:Photochemotherapy; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D014466:Ultraviolet Rays; D014965:X-Rays
D002843:Chromatin; D004273:DNA, Neoplasm; D007211:Indoles; D009942:Organometallic Compounds; D011838:Radiation-Sensitizing Agents; C044797:chloroaluminum phthalocyanine; D000535:Aluminum