All ETDs from UAB

Advisory Committee Chair

Stephen Barnes

Advisory Committee Members

Gary Piazza

Clinton Grubbs

Martin Johnson

Dennis Pillion

William Grizzle

Document Type

Dissertation

Date of Award

2012

Degree Name by School

Doctor of Philosophy (PhD) Heersink School of Medicine

Abstract

ABSTRACT The nonsteroidal anti-inflammatory drug (NSAID) sulindac has displayed the ability to inhibit the proliferation of colorectal cancer (CRC) cells and to increase the sensitivity of multidrug resistant (MDR) cancer cells to a wide variety of chemotherapeutic agents. The antineoplastic activity of sulindac has been attributed to inhibition of the prostaglandin producing enzyme COX-2, but the exact mechanism remains elusive and the inhibition of prostaglandin synthesis can result in gastrointestinal, hepatic, and cardiovascular toxicities. Enzymatic, cellular, and imaging assays were used to identify mechanisms that could contribute to the antiproliferative and apoptotic activity of sulindac. Screening of more than 500 sulindac derivatives revealed structural features that correlated with increased potency for growth inhibition when compared to the COX-inhibiting parent compound, sulindac sulfide (SS). An amine derivative of sulindac, sulindac benzylamine (SBA), did not inhibit prostaglandin synthesis, yet potently inhibited the growth and induced apoptosis of human colon tumor cells. This activity appeared to involve cyclic guanosine monophosphate phosphodiesterase (cGMP PDE) inhibition, activation of cGMP-dependent protein kinase G (PKG), a decrease in ß-catenin mediated transcription and caspase activation. The ability of SS to increase the sensitivity of multidrug resistant cancer cells was investigated by focusing on the two ATP-binding cassette (ABC) transport proteins that are most implicated in clinical multidrug resistant cancer, P-glycoprotein (ABCB1) and multidrug resistant protein-1(ABCC1). Cells over-expressing ABCB1 were significantly less sensitive to SS and doxorubicin in combination than ABCC1 expressing cells. SS also inhibited the efflux of LTC4, a high affinity substrate of ABCC1, from inside-out membrane vesicles, decreased levels of reduced glutathione and increased the intracellular accumulation of calcein-AM. Using SS for comparison, two classes of compounds not previously associated with MDR inhibition were identified. The two classes, 5-quinolinones and imidazopyrimidines, contained members that selectively increased the cytotoxicity of doxorubicin in ABCC1 expressing MDR cells, in some cases potentiating the antiproliferative effect of doxorubicin treatment better than SS. Overall, these studies demonstrate that SS can be used to identify COX-independent pathways involved in the antineoplastic activity of NSAIDs, leading to the development of novel targeted compounds for safer and more effective treatment of CRC and chemoresistance.

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