NSC23925, identified in a high-throughput cell-based screen, reverses multidrug resistance.
BACKGROUND
Multidrug resistance (MDR) is a major factor which contributes to the failure of cancer chemotherapy, and numerous efforts have been attempted to overcome MDR. To date, none of these attempts have yielded a tolerable and effective therapy to reverse MDR; thus, identification of new agents would be useful both clinically and scientifically.


RESULTS
To identify small molecule compounds that can reverse chemoresistance, we developed a 96-well plate high-throughput cell-based screening assay in a paclitaxel resistant ovarian cancer cell line. Coincubating cells with a sublethal concentration of paclitaxel in combination with each of 2,000 small molecule compounds from the National Cancer Institute Diversity Set Library, we identified a previously uncharacterized molecule, NSC23925, that inhibits Pgp1 and reverses MDR1 (Pgp1) but does not inhibit MRP or BCRP-mediated MDR. The cytotoxic activity of NSC23925 was further evaluated using a panel of cancer cell lines expressing Pgp1, MRP, and BCRP. We found that at a concentration of >10 microM NSC23925 moderately inhibits the proliferation of both sensitive and resistant cell lines with almost equal activity, but its inhibitory effect was not altered by co-incubation with the Pgp1 inhibitor, verapamil, suggesting that NSC23925 itself is not a substrate of Pgp1. Additionally, NSC23925 increases the intracellular accumulation of Pgp1 substrates: calcein AM, Rhodamine-123, paclitaxel, mitoxantrone, and doxorubicin. Interestingly, we further observed that, although NSC23925 directly inhibits the function of Pgp1 in a dose-dependent manner without altering the total expression level of Pgp1, NSC23925 actually stimulates ATPase activity of Pgp, a phenomenon seen in other Pgp inhibitors.


CONCLUSIONS
The ability of NSC23925 to restore sensitivity to the cytotoxic effects of chemotherapy or to prevent resistance could significantly benefit cancer patients.
Duan
Zhenfeng
Z
Sarcoma Biology Laboratory, Center for Sarcoma and Connective Tissue Oncology, Massachusetts General Hospital, Boston, Massachusetts, United States of America. zduan@partners.org
Choy
Edwin
E
Hornicek
Francis J
FJ
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000737:chemistry; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000970:Antineoplastic Agents / Q000494:pharmacology*; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D004354:Drug Screening Assays, Antitumor / Q000379:methods*; D005260:Female; D005452:Fluoresceins / Q000737:chemistry; D006801:Humans; D008956:Models, Chemical; D010051:Ovarian Neoplasms / Q000188:drug therapy; D017239:Paclitaxel / Q000494:pharmacology; D010880:Piperidines / Q000494:pharmacology*; D011804:Quinolines / Q000494:pharmacology*
C546115:(2-(4-methoxyphenyl)-4-quinolinyl)(2-piperidinyl)methanol; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000970:Antineoplastic Agents; D005452:Fluoresceins; D010880:Piperidines; D011804:Quinolines; C085925:calcein AM; D000251:Adenosine Triphosphatases; D017239:Paclitaxel