Sulindac-derived compounds for breast cancer therapy

Institution: The Burnham Institute for Medical Research
Investigator(s): Xiao-Kun Zhang, Ph.D. -
Award Cycle: 2014 (Cycle 20) Grant #: 20IB-0138 Award: $292,498
Award Type: IDEA
Research Priorities
Detection, Prognosis and Treatment>Innovative Treatment Modalities: search for a cure



Initial Award Abstract (2014)

Resistance of breast cancer to available therapies and lack of treatment for triple-negative breast cancer (TNBC) represent critical unmet medical needs in the treatment of breast cancer. The PI3K/AKT signaling pathway is abnormally activated in more than 70% of breast tumors and is believed to play a key role in TNBC and drug resistance. Thus, the pathway has been targeted for developing therapeutics against TNBC and for overcoming drug resistance. However, current strategies that rely on direct inhibition of PI3K/AKT activities have resulted in profound toxicities because they affect normal cells and cell pathways. Identification of better therapeutic targets that are responsible for the aberrant activation of the PI3K/AKT pathway will offer new strategies for developing novel and effective TNBC drugs. We recently discovered that retinoid X receptor-alpha (RXR-alpha) is abnormally processed into a shortened, truncated, form of the protein called tRXR-alpha as cells become cancers and that breast tumors have particularly high levels of this tRXR-alpha protein. In addition, we found that tRXR-alpha protein promotes breast cancer cell growth by binding to PI3K and activating the PI3K/AKT pathway. Therefore, tRXR-alpha represents a potential therapeutic target for TNBC and drug resistance. Moreover, we discovered that nonsteroidal anti-inflammatory drug (NSAID) Sulindac and Sulindac-derived compounds (analogs) could bind to tRXR-alpha, block it from activating the PI3K/AKT pathway, and inhibit the growth of breast cancer cells. Thus, in this IDEA grant application, we propose to develop new Sulindac analogs with improved efficacy and selectivity for breast cancer therapy and for overcoming drug resistance.

The question(s) or central hypotheses of the research: The central hypotheses of our research are: (i) tRXR-alpha is a tumor protein and plays a critical role in the development of breast cancer, the survival of TNBC cells and drug resistance, (ii) tRXR-alpha is a novel therapeutic target involved in the abnormal activation of the PI3K/AKT pathway and (iii) Sulindac analogs targeting tRXR-alpha represent a new class of therapeutics for treating breast cancer including TNBC and for disabling drug resistance.

The general methodology: We will design, synthesize and evaluate a few new Sulindac analogs with a goal of identifying a drug candidate. We will first design new Sulindac analogs using computer-aided drug design approaches and will evaluate the inhibitory effects of the new analogs on the activity of the PI3K/AKT pathway. We will then use a panel of TNBC and non-TNBC breast cancer cell lines to evaluate and determine the effects of the new analogs on breast cancer cell growth and apoptosis. Furthermore, we will use breast tumor animal models to determine the anti-tumor effects of the analogs

Innovative elements of the project: There are several innovative and exploratory aspects of the project: (i) our concept that tRXR-alpha is a key molecule involved in the aberrant activation of PI3K/AKT pathway in breast cancer cells is novel and significant. This provides a new target and strategy to modify the PI3K/AKT pathway for breast cancer therapy, (ii) our discovery that Sulindac and analogs could target tRXR-alpha to kill cancer cells including TNBC cells offers a great starting point to develop small molecule therapeutics for breast cancer treatment and drug resistance and (iii) since our proposed Sulindac analogs are derived from an existing drug with proven drug safety in human, they hold great promise on a "critical path" to advance the topic under investigation to clinic.




Final Report (2016)

The objective of our IDEA grant application is to identify Sulindac-derived compounds, which target tumor protein tRXRa for breast cancer therapy. The tRXRa protein is a proteolytically-cleaved nuclear receptor RXRa, which is produced in breast cancer cells but not in normal mammary cells. The oncogenic effect of tRXRa is largely attributed to its activation of the phosphoinositide 3-kinase (PI3K)/AKT survival pathway and the inhibitor of kappa B (kB) kinase (IKK)/NF-kB inflammatory pathway, two major signaling pathways that are abnormally activated in breast cancer cells to confer their growth, metastasis, and drug resistance. We previously discovered that nonsteroidal anti-inflammatory drug (NSAID) Sulindac and Sulindac-derived compounds (analogs) could bind to tRXRa and inhibit its oncogenic activities, leading to growth inhibition of breast cancer cells. We proposed two aims to address our objective. Aim 1 is to design, synthesize, and characterize Sulindac analogs for binding to the new tRXRa binding site, and Aim 2 is to assess the efficacy and selectivity of Sulindac-derived tRXRa modulators.

We have successfully designed and synthesized over 35 Sulindac analogs. The analogs were initially evaluated for their binding to RXRa and induction of breast cancer cell apoptosis. After initial evaluations, several analogs including K-80003, K-8008, and K- 8012 were further subjected to in depth mechanistic studies and evaluation in animals. Our results identified K-80003 as a potent antibreast cancer agent with desirable pharmacological and toxicological profiles. In vitro, K-80003 is active against ER-positive MCF-7 and triple negative MDA-MB-231 breast cancer cells. In animals, K-80003 alone or combination with K-8008, another Sulindac analog, inhibited the growth of MCF-7 breast cancer cells in nude mice. K-80003 also inhibited the growth of mammary tumor in the transgenic MMTV-PyMT mouse model. Moreover, it inhibited the metastasis of PyMT mammary tumor to the lung. Mechanistically, K-80003 is capable of inhibiting tRXRa interaction with p85a and TRAF2 in breast cancer cells, leading to downregulation of both PI3K/AKT survival and IKK/NF-kB inflammatory signaling pathways. In addition, K-80003 inhibited tRXRa from interacting with TRAF6 resulting in suppression of the NF-kB signaling in macrophages. Thus, K-80003 exerts its anti-breast cancer effect by inhibiting the development of tumor inflammatory microenvironment. Our X-ray crystallographic studies reveal a unique binding of K-80003 to tRXRa. Such a binding promotes tetramerization of tRXRa but not RXRa, thus providing a molecular explanation for its effective antagonism of tRXRa activities. A GMP-compliant manufacturing process for K-80003 has been established. Safety pharmacological studies that included assessments of cardiovascular, CNS, respiratory and gastrointestinal systems have been performed. Toxicological studies comprising acute single dose and repeat dose experiments have been conducted that comprise pharmacokinetic (PK), toxicokinetic (TK) and histopathological assessments. K-80003 displays very desirable toxicological and pharmacological profiles and it is under evaluation by FDA for clinical trial against cancer.




Conference Abstract (2016)

Sulindac-derived compounds for breast cancer therapy

Investigator: Xiao-kun Zhang
Institution: Sanford Burnham Prebys Medical Discovery Institute

The objective of our IDEA grant application is to identify Sulindac-derived compounds targeting the truncated retinoid X receptor-? (tRXR?) for breast cancer therapy. tRXR? protein is a proteolytically-cleaved RXR? nuclear receptor that is produced in breast cancer cells but not in normal mammary cells. The oncogenic effect of tRXR? is largely attributed to its activation of the phosphoinositide 3-kinase (PI3K)/AKT survival pathway and its inhibition of the kappa B kinase (IKK)/NF-?B inflammatory pathway, two major pathways that are abnormally activated in breast cancer cells to confer their growth, metastasis and drug resistance. We previously discovered that nonsteroidal anti-inflammatory drug (NSAID) Sulindac and Sulindac-derived compounds (analogs) could bind to tRXR? and inhibit its oncogenic activities, leading to the growth inhibition of breast cancer cells. We proposed two aims to address our objective. Aim 1 is to design, synthesize, and characterize Sulindac analogs that can bind to a novel binding site on tRXR?, and Aim 2 is to assess the efficacy and selectivity of Sulindac-derived tRXR? modulators.

We have designed and synthesized over 40 Sulindac analogs. The analogs were evaluated for their binding to RXR? and induction of breast cancer cell apoptosis. Our evaluation showed that K-80003 and related analogs can effectively inhibit the growth of breast cancer cells. Our mechanistic studies demonstrated that some of these analogs suppressed the PI3K/AKT signaling by inhibiting the interaction of tRXR? with the p85? subunit of PI3K, while others inhibited the IKK/NF-?B signaling by preventing tRXR? from binding to tumor necrosis factor receptor-associated factor 2 (TRAF2). Among the analogs, we found K-80003 unique and effective with the ability to not only prevent tRXR? from interacting with p85? and TRAF2 in breast cancer cells but also inhibit tRXR? from interacting with TRAF6 and activation of NF-?B in macrophages. Thus, K-80003 is an effective inhibitor of tumor inflammatory microenvironment by targeting tRXR?-mediated survival and inflammatory pathways both in breast cancer cells and macrophages. Our X-ray crystallographic studies revealed a unique binding mechanism of K-80003, which resulted in the tetramerization of tRXR? but not RXR?, thus providing a molecular explanation for its effective antagonism effect against tRXR? activities. K-80003 is active in the triple negative MDA-MB-231 breast cancer cells. K-80003 alone or combination with another Sulindac analog K-8008 inhibited the growth of breast cancer cells in nude mice and the growth of mammary tumor in the transgenic MMTV-PyMT mouse model of breast tumor. A GMP-compliant manufacturing process for K-80003 has been established. Safety pharmacological studies that included assessments of cardiovascular, CNS, respiratory and gastrointestinal systems have been performed. Toxicological studies comprising acute single dose and repeat dose experiments have been conducted that comprise pharmacokinetic (PK), toxicokinetic (TK) and histopathological assessments. K-80003 displays very desirable toxicological and pharmacological profiles and it is under evaluation by FDA for clinical trial against cancers.



Regulation of the nongenomic actions of retinoid X receptor-a by targeting the coregulator-binding sites - doi: 10.1038/aps.2014.109
Periodical:Acta Pharmacol Sin
Index Medicus: Act Pharm Sin
Authors: Zhang, X-k, Su Y, Chen, L, Chen, F, Liu, J, Zhou, H.
Yr: 2014 Vol: Nbr: Abs: Pg:

Nitrostyrene Derivatives Act as RXR Ligands to Inhibit TNF Activation of NF- kB
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Index Medicus: Cancer Res
Authors: Zeng Z, Sun Z, Huang M, et al.
Yr: 2015 Vol: Mar 20 Nbr: Abs: Pg:

Induction of Nur77-dependent apoptotic pathway by a coumari derivative through activation of JNk and p38 MAPK. PMCID: PMC4247515.
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Index Medicus: Carcinogenesis
Authors: Zhou Y, Zhao W, Xie G, et al.
Yr: 2014 Vol: 35 Nbr: Abs: Pg:2660-9

Targeting truncated RXR for cancer therapy
Periodical:Acta Biochimica et Biophysica Sinica
Index Medicus: Acta Biochim Biophys Sin
Authors: Zhang, XK., Zhou, H., and Su, Y.
Yr: 2016 Vol: 48 Nbr: Abs: Pg:49-59

Homokiol sensitizes breast cancer cells to TNFinduction of apoptosis by inhibiting Nur77 expression
Periodical:British Journal of Pharmacology
Index Medicus: British J Pharmacol
Authors: Xie L, Jiang F, Zhang X, Alitongbieke G, Shi X, Meng M, Xu Y, Ren A, Wang J, Cai L, et al.
Yr: 2016 Vol: 173 Nbr: Abs: Pg:344-356

NSC-640358 acts as RXR ligand to promote TNF-mediated apoptosis of cancer cell
Periodical:Protein & Cell
Index Medicus: Protein Cell
Authors: Chen, F., Chen, J., Lin, J., Cheltsov, AV., Xu, L., Chen, Y., Zeng, Z., Chen, L., et al.
Yr: 2015 Vol: 6 Nbr: Abs: Pg:654-666

Binding characterization, synthesis and biological evaluation of RXRa antagonists targeting the coactivator binding site
Periodical:Bioorganic & Medicinal Chemistry
Index Medicus: Bioorg Med Chem
Authors: Xu D, Guo S, Chen Z, Bao Y, Huang F, Xu D, Zhang X, Zeng Z, Zhou H, Zhang X, Su Y
Yr: 2016 Vol: 26 Nbr: 16 Abs: Pg:3846-9