Y. Mizushima et al., EFFECT OF CISPLATIN EXPOSURE ON THE DEGREE OF N-MYC AMPLIFICATION IN SMALL-CELL LUNG-CARCINOMA CELL-LINES WITH N-MYC AMPLIFICATION, Oncology, 53(5), 1996, pp. 417-421
To know whether the degree of N-myc gene amplification would change or
not by the treatment with chemotherapeutic agents, we studied the eff
ect of cisplatin (CDDP) exposure on the degree of amplification of the
N-myc gene in two small cell lung carcinoma (SCLC) cell lines with N-
myc amplification (H-69, SBC-4). The N-myc gene was amplified around 6
0-fold in H-69 and 40-fold in SEC-4 cells compared with placenta tissu
es, and these two cell Lines were more resistant to CDDP than the nine
other SCLC cell lines without N-myc amplification. H-69/CP cells beca
me 4.1 times and SBC-4/CP cells 2.1 times more resistant to CDDP compa
red to their parent cells by continuous in vitro exposure to CDDP. How
ever, there was no significant difference in the degree of amplificati
on or overexpression of the N-myc gene between parent and CDDP-resista
nt cells in both cell lines. Namely, the degree of N-myc amplification
did not show a significant change by making these cells more resistan
t to CDDP. These results suggest that (1) the amplification of the N-m
yc gene may be unchangeable by chemotherapeutic agents, and (2) the de
gree of CDDP resistance may not correlate with the degree of amplifica
tion or overexpression of the N-myc gene, if activation of the N-myc g
ene would be related to the drug resistance.