Book of abstract 2008

UV induced rare forms) using RT-PCR. Alternative/mutant EGFR extracellular domains
were found with high frequency: 15 out of the 28 samples contained low molecular weight
PCR products. We have postulated that the mutant EGFR in human melanoma may serve
a target for EGFR TK inhibitors. We have used two clinically available EGFR inhibitors,
Gefitinib (Iressa, ZD1839) and Erlotinib (Tarceva, OSI-774) to test the sensitivity of
human melanoma cell lines. Melanoma cells were proved to be resistant to OSI-774 while
ZD1839 exhibited >50% inhibition of proliferation at 10 μM. Furthermore, in 6 out of
the 8 human melanoma cell lines ZD1839 induced significant increase in apoptotic rates
at a concentration of 25 μM. Next we have pretreated HT168M1 cells with ZD1839 for
48 hr and the surviving tumor cells were tested for their migratory potential in a Boyden
chamber assay. We found that ZD1839-pretreated cells lost their migratory potential,
which started at 0.1 μM drug concentration and became highly significant at 10 μM.
Phosphoproteome analysis of WM983B human melanoma cells indicated that ZD1839
inhibited constitutive phosphorylation of MAPK/ERK1, CDC2 and JNK at 5 and 30
min exposures. Ultimately, we have tested the antitumoral effects of ZD1839 in vivo using
a spleen-liver melanoma (WM983B) metastasis model in SCID mice. Tumor cells were
inoculated into the spleen at a dose of 106 cells/animal and daily i.p. drug treatment was
started on day 7 th (0.1-20 mg/kg) for two weeks. When the weight loss of animals in
the control group exceeded 20%, the experiment was terminated. Analysis of the primary
spleen tumors revealed no effect of ZD1839. However, ZD1839 significantly inhibited
liver metastasis formation of human melanoma cells by 62% (2 mg/kg) and 86% (20 mg/
kg). Our data suggest that human melanoma may frequently carry extracellular domain
mutations in the EGFR and these aberrations may render it sensitive to EGFR tyrosine
kinase inhibitors.
This work was supported by the Ministry of Education (NKFP-1a-0024-05). ZD1839 was supplied by
AstraZeneca.
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