ALA-Dependent Cancericides - Chlorophyll Biosynthesis and Technological Applications - page 435

The relative merits of ALA and Oph in inducing Proto accumulation and cell
lysis were also investigated by treatment of MLA 144 cells in darkness either with
ALA, with Oph, or with a combination of the two compounds. Although ALA alone
induced significant levels of Proto accumulation and photodynamic cell injury, the
most dramatic tetrapyrrole accumulation and cell destruction were observed when
cells were treated jointly with ALA + Oph (Rebeiz et al. 1992 ). The addition of
Oph doubled Proto accumulation and significantly increased cell lysis in the light.
1,10-Phenanthroline, alone, did not induce Proto accumulation.
19.2.3 Proto-Dependent Photodestruction of MLA
and WEHI 164-Clone13 Cells Following
ALA and Oph Treatments
The susceptibility of other transformed cell lines to ALA + Oph treatment was also
investigated. The response of a human granulocytic leukemia cell line (K562), and
a murine fibrosarcoma cell line (WEHI 164 clone 13), was compared to that of
MLA 144 cells (Rebeiz et al. 1992 ). Both transformed cell lines exhibited photo-
dynamic injury similar to the MLA 144 cells.
However, the human granulocytic leukemia cells were extremely sensitive to
treatment as evidenced by the lower concentrations of ALA and Oph that induced
significant photodynamic cell lysis (Rebeiz et al. 1992 ).
19.2.4 Enhancement of Proto Accumulation
by Murine Splenocyte Treatment
Since increased tetrapyrrole biosynthesis and accumulation is more likely to take
place in rapidly growing and multiplying cells in need of heme for cytochrome
formation, it was conjectured that slowly proliferating cells might be less prone to
accumulate tetrapyrroles than rapidly multiplying cells. To test this hypothesis,
splenocyte suspensions from BALB/c mice were prepared and, following incuba-
tion in the presence or absence of the mitogenic lectin Con A (1.25 pLg/mL
for 40 h), were untreated or treated with 1 mM ALA + 0.75 mM Oph for 3.5 h
(Rebeiz et al. 1992 ).
The amount of Proto accumulation in these two cell populations was
compared to ALA + Oph treated MLA 144 cells. Resting splenocytes treated
with ALA + Oph accumulated much less Proto compared to similarly treated
Con A-activated splenocytes, which exhibited a 50-fold increase in cell prolife-
ration as indicated by tritiated thymidine incorporation.
Concanavalin A-activated splenocytes accumulated levels of Proto comparable
to those of ALA + Oph treated MLA 144 lymphoma cells.