The Journal of Thoracic and Cardiovascular Surgery, Vol 101, 795-799, Copyright © 1991 by The American Association for Thoracic Surgery and The Western Thoracic Surgical Association
Photodynamic therapy of oncogene-transformed cells
HI Pass, S Evans, WA Matthews, R Perry, D Venzon, JA Roth and P Smith
Thoracic Oncology Section, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892.
Photodynamic therapy with dihematoporphyrin ether sensitizes malignant
cells to damage by 630 nm light. The in vitro, in vivo photodynamic therapy
sensitivity of a cell line transformed by the Kirsten ras oncogene (45342)
was studied to establish a new photodynamic therapy model. With the colony
formation assay, neither light alone nor dihematoporphyrin ether alone
affected 45342 survival. Energy-dependent photodynamic therapy effects were
seen in vitro in dihematoporphyrin ether-incubated and light-exposed cells
(90% cytotoxicity = 950 joules/m2; 99% cytotoxicity = 1575 joules/m2; p2
less than 0.05). Subcutaneous allografts of 45342 were established in nu/nu
mice, and ideal route (intravenous or intraperitoneal) of dihematoporphyrin
ether delivery, dihematoporphyrin ether tissue kinetics, and in vivo
photodynamic therapy effects were examined. Intravenous administration not
only gave higher levels of the sensitizer in various tissues, but also was
associated with less variation than the intraperitoneal route. Selective
dihematoporphyrin ether retention was documented in the tumors at 24 hours
after injection compared with other tissues, and photodynamic therapy with
0.3 W/cm2 to a total dose of 150 joules/cm2 led to progressive coagulative
tumor necrosis and tumor regression. These studies confirm that
transformed, malignant cells are sensitive to photodynamic therapy, and
this model may prove in future studies to increase efficacy to photodynamic
therapy (i.e., with dihematoporphyrin ether delivery by monoclonal
antibodies).