Development of resistance to a trinuclear platinum complex in ovarian carcinoma cells.
BBR3464 is a trinuclear platinum complex that exhibits a potent cytotoxicity and efficacy against cisplatin-resistant tumors. To better understand the determinants of cellular resistance to BBR3464, we selected a resistant ovarian carcinoma cell line after exposure to the complex. The resistant cells (A2780/BBR3464) exhibited a high level of resistance to the selecting agent, but a marginal cross-resistance to cisplatin. Although cellular accumulation of BBR3464 was similar in parental and in resistant cells, DNA platination was decreased in A2780/BBR3464 cells, suggesting a reduced drug accessibility to DNA. This behavior reflected a partial drug inactivation at cytoplasmic level, as a consequence of increased levels of nucleophilic molecules including metallothioneins and human neurofilament low, but not glutathione. A2780/BBR3464 cells also exhibited a reduced susceptibility to apoptosis, which was consistent with reduced expression of Bax, and an alteration of DNA mismatch repair system, as reflected by lack of expression of MLH1 and PMS2, which could impair the recognition/repair of DNA lesions. Whereas both platinum drugs induced G2/M arrest in the parental cells, BBR3464, but not cisplatin, caused a late G1 arrest of resistant cells. Cisplatin induced an appreciable increase of p21(WAF1) levels in both models, in contrast to BBR3464 that produced a substantial upregulation of p21(WAF1) only in parental cells. An inverse relationship with p21(WAF1) modulation was found for CHK1 in parental cells treated with both agents and in resistant cells treated with cisplatin. This pattern of response is consistent with a regulatory loop involving p53 and p21(WAF1) at G2 checkpoint. In contrast, no modulation of CHK1 was found in A2780/BBR3464 treated with the triplatinum compound. These findings, indicating a different activation of regulatory pathways at DNA damage checkpoints in response to cisplatin and BBR3464, support an altered ability of resistant cells to recognize or tolerate sublethal lesions induced by BBR3464.
Perego
Paola
P
Istituto Nazionale Tumori, via Venezian 1, 20133 Milan, Italy. paola.perego@istitutotumori.mi.it
Gatti
Laura
L
Righetti
Sabina C
SC
Beretta
Giovanni L
GL
Carenini
Nives
N
Corna
Elisabetta
E
Dal Bo
Laura
L
Tinelli
Stella
S
Colangelo
Donato
D
Leone
Roberto
R
Apostoli
Piero
P
Lombardi
Luciano
L
Beggiolin
Gino
G
Piazzoni
Laura
L
Zunino
Franco
F
D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D020137:Base Pair Mismatch; D002330:Carmustine / Q000494:pharmacology; D000071877:Checkpoint Kinase 1; D002945:Cisplatin / Q000494:pharmacology; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000096:biosynthesis; D018736:DNA Adducts; D004249:DNA Damage; D004260:DNA Repair; D004273:DNA, Neoplasm / Q000187:drug effects; D004317:Doxorubicin / Q000494:pharmacology; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D005260:Female; D016193:G1 Phase / Q000187:drug effects; D005978:Glutathione / Q000378:metabolism; D006801:Humans; D008558:Melphalan / Q000494:pharmacology; D008668:Metallothionein / Q000096:biosynthesis; D009944:Organoplatinum Compounds / Q000494:pharmacology*; D010051:Ovarian Neoplasms / Q000473:pathology*; D017239:Paclitaxel / Q000494:pharmacology; D011494:Protein Kinases / Q000096:biosynthesis; D014407:Tumor Cells, Cultured / Q000187:drug effects
D000970:Antineoplastic Agents; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D018736:DNA Adducts; D004273:DNA, Neoplasm; D009944:Organoplatinum Compounds; D004317:Doxorubicin; D008668:Metallothionein; D011494:Protein Kinases; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1; D005978:Glutathione; C114062:BBR 3464; D017239:Paclitaxel; D002945:Cisplatin; D008558:Melphalan; D002330:Carmustine