The new platinum(IV) derivative LA-12 shows stronger inhibitory effect on Hsp90 function compared to cisplatin

Table 1 Analysis of interaction of Hsp90 with LA-12

Sample	Applied	Result (± SD)	Result
	compound	mg Pt/ml	ng Pt/mg protein
D-MEM	negative	-
10 μM cisplatin	10 μM cisplatin	2.09 (0.05)
50 μM cisplatin	50 μM cisplatin	9.93 (0.21)
10 μM LA-12	10 μM LA-12	1.96 (0.01)
50 μM LA-12	50 μM LA-12	9.14 (0.26)
L1	negative	-
L2	10 μM cisplatin	0.040 (0.0004)	20
L3	50 μM cisplatin	0.290 (0.005)	145
L4	10 μM LA-12	1.98 (0.02)	990
L5	50 μM LA-12	11.6 (0.26)	5500
P1	negative	-
P2	10 μM cisplatin	-
P3	50 μM cisplatin	< 0.02
P4	10 μM LA-12	0.034 (0.004)
P5	50 μM LA-12	0.222 (0.01)
NC1	50 μM cisplatin	-
NC2	50 μM LA-12	-
AC1	50 μM cisplatin	-
AC2	50 μM LA-12	-

Platinum levels were determined by AAS in whole cell lysates (L1-5) of H1299 control cells and cells treated with 10 μM and 50 μM LA-12 or cisplatin for 9 hours. The protein concentration of cell lysates was 2 mg/ml. The amounts of platinum bound to Hsp90 was measured after immunoprecipitation of Hsp90 from H1299 control cells and cells treated with 10 μM and 50 μM LA-12 or cisplatin for 9 hours (P1-5). Immunoprecipitations without antibody (NC1-2) and with DO-1 antibody (AC1-2) in cells treated with 50 μM LA-12 and cisplatin were performed as negative control for crossreactivity of platinum compounds with other reaction components. Control AAS platinum measurements were perfomed in D-MEM cell medium containing 10 μM and 50 μM LA-12 or cisplatin. Results are mean ± SD of triplicate experiments.

ISSN: 1476-4598