Zhengduo Yang

Transcription Factor STAT3 as a Novel Molecular Target for Cancer Prevention

Signal Transducers and Activators of Transcription (STATs) are a family of transcription factors that regulate cell proliferation, differentiation, apoptosis, immune and inflammatory responses, and angiogenesis. Cumulative evidence has established that STAT3 has a critical role in the development of multiple cancer types. Because it is constitutively activated during disease progression and metastasis in a variety of cancers, STAT3 has promise as a drug target for cancer therapeutics. Recently, STAT3 was found to have an important role in maintaining cancer stem cells in vitro and in mouse tumor models, suggesting STAT3 is integrally involved in tumor initiation, progression and maintenance. STAT3 has been traditionally considered as nontargetable or undruggable, and the lag in developing effective STAT3 inhibitors contributes to the current lack of FDA-approved STAT3 inhibitors. Recent advances in cancer biology and drug discovery efforts have shed light on targeting STAT3 globally and/or specifically for cancer therapy. In this review, we summarize current literature and discuss the potential importance of STAT3 as a novel target for cancer prevention and of STAT3 inhibitors as effective chemopreventive agents.

Novel Nitrogen-Enriched Oridonin Analogues with Thiazole-Fused A‑Ring: Protecting Group-Free Synthesis, Enhanced Anticancer Profile, and Improved Aqueous Solubility

Oridonin (1), a complex ent-kaurane diterpenoid isolated from the traditional Chinese herb Isodon rubescens , has demonstrated great potential in the treatment of various human cancers due to its unique and safe anticancer pharmacological profile. Nevertheless, the clinical development of oridonin for cancer therapy has been hampered by its relatively moderate potency, limited aqueous solubility, and poor bioavailability. Herein, we report the concise synthesis of a series of novel nitrogen-enriched oridonin derivatives with thiazole-fused A-ring through an efficient protecting group-free synthetic strategy. Most of them, including compounds 7-11, 13, and 14, exhibited potent antiproliferative effects against breast, pancreatic, and prostate cancer cells with low micromolar to submicromolar IC50 values as well as markedly enhanced aqueous solubility. These new analogues obtained by rationally modifying the natural product have been demonstrated not only to significantly induce the apoptosis and suppress growth of triple-negative MDA-MB-231 breast cancer both in vitro and in vivo but also effective against drug-resistant ER-positive MCF-7 clones.

Fragment-based drug design and identification of HJC0123, a novel orally bioavailable STAT3 inhibitor for cancer therapy

Fragment-based drug design (FBDD) is a promising approach for the generation of lead molecules with enhanced activity and especially drug-like properties against therapeutic targets. Herein, we report the fragment-based drug design, systematic chemical synthesis and pharmacological evaluation of novel scaffolds as potent anticancer agents by utilizing six privileged fragments from known STAT3 inhibitors. Several new molecules such as compounds 5, 12, and 19 that may act as advanced chemical leads have been identified. The most potent compound 5 (HJC0123) has demonstrated to inhibit STAT3 promoter activity, downregulate phosphorylation of STAT3, increase the expression of cleaved caspase-3, inhibit cell cycle progression and promote apoptosis in breast and pancreatic cancer cells with low micromolar to nanomolar IC50 values. Furthermore, compound 5 significantly suppressed estrogen receptor (ER)-negative breast cancer MDA-MB-231 xenograft tumor growth in vivo (p.o.), indicating its great potential as an efficacious and orally bioavailable drug candidate for human cancer therapy.

Oridonin Ring A-Based Diverse Constructions of Enone Functionality: Identification of Novel Dienone Analogues Effective for Highly Aggressive Breast Cancer by Inducing Apoptosis

Oridonin (1) has attracted considerable attention in recent years because of its unique and safe anticancer pharmacological profile. Nevertheless, it exhibits moderate to poor effects against highly aggressive cancers including triple-negative and drug-resistant breast cancer cells. Herein, we report the rational design and synthesis of novel dienone derivatives with an additional α,β-unsaturated ketone system diversely installed in the A-ring based on this class of natural scaffold that features dense functionalities and stereochemistry-rich frameworks. Efficient and regioselective enone construction strategies have been established. Meanwhile, a unique 3,7-rearrangement reaction was identified to furnish an unprecedented dienone scaffold. Intriguingly, these new analogues have been demonstrated to significantly induce apoptosis and inhibit colony formation with superior antitumor effects against aggressive and drug-resistant breast cancer cells in vitro and in vivo while also exhibiting comparable or lower toxicity to normal human mammary epithelial cells in comparison with 1.

Inhibition of farnesoid X receptor controls esophageal cancer cell growth in vitro and in nude mouse xenografts

Gastroesophageal reflux is a risk factor for esophageal adenocarcinoma, and bile acid and its farnesoid X receptor (FXR) have been implicated in esophageal tumorigenesis. The authors investigated the role of FXR expression and activity in esophageal cancer initiation and growth.

Discovery of Potent Anticancer Agent HJC0416, an Orally Bioavailable Small Molecule Inhibitor of Signal Transducer and Activator of Transcription 3 (STAT3)

In a continuing effort to develop orally bioavailable small-molecule STAT3 inhibitors as potential therapeutic agents for human cancer, a series of novel diversified analogues based on our identified lead compound HJC0149 (1) (5-chloro-N-(1,1-dioxo-1H-1λ(6)-benzo[b]thiophen-6-yl)-2-hydroxybenzamide, Eur. J. Med. Chem. 2013, 62, 498-507) have been rationally designed, synthesized, and pharmacologically evaluated. Molecular docking studies and biological characterization supported our earlier findings that the O-alkylamino-tethered side chain on the hydroxyl group is an effective and essential structural determinant for improving biological activities and druglike properties of these molecules. Compounds with such modifications exhibited potent antiproliferative effects against breast and pancreatic cancer cell lines with IC50 values from low micromolar to nanomolar range. Among them, the newly discovered STAT3 inhibitor 12 (HJC0416) displayed an intriguing anticancer profile both in vitro and in vivo (i.p. & p.o.). More importantly, HJC0416 is an orally bioavailable anticancer agent as a promising candidate for further development.

Abstract P6-12-04: Targeting STAT3 with novel small molecule inhibitors to sensitize breast cancer cells to radiation therapy

Radiation therapy plays an important role in controlling the growth and progression of breast cancer. However, its efficacy is limited by the radiation-associated toxicity to normal tissue, and the intrinsic or acquired radioresistance developed in cancer cells. It was well documented that radiation onto cancer tissues cause complex changes in gene expression patterns. Thus, it may be possible to manipulate the expression of specific genes in cancer cells to increase radiosensitivity and reduce radioresistance. Accumulating studies strongly demonstrated that signal transducers and activators of transcription 3 (STAT3) is involved in cell survival, proliferation, inflammation, invasion, metastasis, angiogenesis and immune responses. Particularly, STAT3 is activated by ionizing radiation. We hypothesized that blocking STAT3 will increase sensitivity to irradiation in cancer cells. To this end, we synthesized a series of novel STAT3 inhibitors to address the challenge of radioresistance in breast cancer cells including metastatic and triple-negative lines. Among them, the compound HJC0152 and HJC0123 displayed significant inhibition of proliferation of MDA-MB-231, MCF-7 and MCF-7/Adr in dose and time dependent manners. HJC0152 and HJC0123 also induced apoptosis and necrosis in comparison to the control cells. We also found that these STAT3 inhibitors induce apoptosis of MDA-MB-231, MCF-7 and MCF-7/Adr cells by inhibiting anti-apoptotic protein Bcl-2 expression, increasing the expression of apoptotic effector protein caspase-3 and Bax. In addition, we found that HJC0152 and HJC0123 in combination with X-ray irradiation induce G2/M cell cycle arrest in MDA-MB-231, MCF-7 andMCF-7/Adr cells. The new STAT3 inhibitors increased the radiosensitivity of MDA-MB-231, MCF-7 and MCF-7/Adr cell lines, inhibited radiation-induced DNA damage repair, and promoted cells to enter mitosis, a phase more sensitive to irradiation. These changes were accompanied with decreased activation of STAT3 and decreased expression of the STAT3 downstream gene, Bcl-2. Our findings suggest that STAT3 blockade may represent an effective strategy to overcome radiation resistance, using STAT3 inhibitors as radiation sensitizers to restore the sensitivity of cancer cells to radiation therapy. Citation Format: Lili Wang, Zhengduo Yang, Qing Xia, Haijun Chen, Guoshuai Cai, Christopher Wild, Jia Zhou, Qiang Shen. Targeting STAT3 with novel small molecule inhibitors to sensitize breast cancer cells to radiation therapy [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P6-12-04.

Abstract B85: Role of the TASK2 in regulating breast cancer cell proliferation

Selective estrogen receptor (ER) modulators (SERMs) such as tamoxifen and raloxifene, and aromatase inhibitors are able to partially reduce incidence in high-risk women to develop ER-positive breast cancer but not all ER-positive neither ER-negative breast cancers. Thus, effective targets and agents for the prevention of both ER-positive and ER-negative breast cancer are urgently needed. Potassium ion channels are essential in maintaining cellular homeostasis in terms of transmitting signal molecules, regulating cell volume and secreting ions and hormones. A family of potassium channels, TASKs, is differentially expressed in normal breast tissue and breast cancer tissues. In particular, TASK2 mRNA was found upregulated in human breast carcinoma but not in normal mammary gland tissue, and TASK2 is significantly up-regulated in ER-negative vs ER-positive breast cancers across multiple studies among the Oncomine databases. We hypothesized that TASK2 plays an important role in regulating growth of breast cancer cells. We then knocked down the TASK2 gene expression using siRNA in ER-positive and ER-negative breast cancer cells. Transient knockdown of TASK2 suppressed cell proliferation significantly in 7/8 ER-negative and moderately in 3/5 ER-positive breast cancer cell lines. However, proliferation of an immortal breast epithelial cell line, MCF-10A, was not affected. We are now investigating the phenotypic alterations in normal and malignant breast cells after overexpressing or knocking down the TASK2 gene. Current results suggest that TASK2 plays an important role in breast cell growth. Thus, TASK2 is a potential novel target for future breast cancer prevention and treatment. Citation Information: Cancer Prev Res 2011;4(10 Suppl):B85.

Abstract 329: Reprogramming glucose metabolism and energy production with a small molecule HJC0152 suppresses breast cancer development and progression to metastasis

Currently there are no targeted therapeutic strategies for estrogen receptor (ER)-negative breast cancer (ENBC), which constitutes 30-40% of breast cancer cases and is prone to metastasize and recur. Distant metastasis accounts for 90% of cancer-associated deaths. The majority of deaths from breast cancer are caused by distant metastasis developed in lung, liver, bone, or brain. However, to date it remains a challenge and unmet need to treat existing metastasis and block new metastasis in cancer patients. Dysregulated glucose and energy metabolism is critically involved in the development and progression of various cancers via promoting aberrant cell growth, malignant transformation and metastasis, but the potential role of glucose/energy metabolism in ENBC progression and metastasis has scarcely been explored heretofore, thus representing a key knowledge gap and a potential avenue for anticancer targeting. A number of anticancer metabolic and biogenetic therapies have been developed, yet none of them has progressed to clinical use, due to their limited potency, specificity or drug properties such as toxicity and poor bioavailability. We recently identified a novel small molecule HJC0152 that significantly suppresses ENBC xenograft tumor growth and blocks ER-negative mammary tumor development in mouse models. HJC0152 treatment for 24-72 hours differentially modulates protein expression of HK1, PFK-L, PFKFB2, ENO2, PDH, PDK1, PGAM1 and ALDOA in a time-dependent manner. HJC0152 also regulates the transcription of genes involved in glucose and mitochondrial energy metabolism, including the subunits of mitochondrial respiratory chain complexes. Functional assessments of mitochondrial complexes demonstrate that HJC0152 significantly inhibits Complexes IV but increases Complex V (ATP synthase) function, while Complexes I and II function is minimally affected. Migration and invasion of MDA-MB-231 cells are significantly inhibited by HJC0152 treatment. In vivo, HJC0152 administrated either before, concurrent with or after tail vein injection of MDA-MB-231 cells dramatically blocks the development of lung macro- and micro-metastasis in all groups. These results suggest that HJC0152 can specifically reprogram/restore the dysregulated glucose metabolism by inducing specific glycolytic enzyme expression and mitochondrial respiratory chain function, likely via targeting one or more upstream signal molecule(s) that regulates glucose and energy metabolism, thereby suppressing breast cancer progression to metastasis. This work was supported by Grants P50 CA097007, P30DA028821, and R21MH093844 (J.Z.) from the NIH, CPRIT (J.Z.), John Sealy Memorial Endowment Fund (J.Z.), DFI Seed Grants from MD Anderson Cancer Center (Q.S.), and Holden Family Research Grant in Breast Cancer Prevention from the Prevent Cancer Foundation (Q.S). Citation Format: Hao Zou, Na Ye, Hui Pang, Dan Zhang, Ruping Yan, Haijun Chen, Guoshuai Cai, Lili Wang, Zhengduo Yang, Haiying Chen, Grace Xu, Yingchao Zhang, Ritu Arora, Ming Tan, Yongchang Wei, Jia Zhou, Qiang Shen. Reprogramming glucose metabolism and energy production with a small molecule HJC0152 suppresses breast cancer development and progression to metastasis. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 329.

Abstract 3805: Anticancer agent HJC0416 inhibits the growth of breast cancer xenografts via downregulating STAT3 signaling

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Signal transducers and activators of transcription (STATs) play important roles in regulating the expression of genes activated during tumorigenesis. Particularly, STAT3 has been shown to contribute significantly in breast carcinogenesis and is often overexpressed in primary breast tumors. Increased STAT3 transcriptional activity is correlated with ER-negative phenotype in breast cancer cell lines and in primary invasive ductal breast carcinomas. Therefore, STAT3 emerges as a promising target for breast cancer treatment and prevention. We have designed, synthesized and screened a series of novel STAT3 inhibitors utilizing fragment-based drug design strategy. A number of small molecules with novel scaffolds have been discovered with low-micromolar to nanomolar potency in inhibiting the proliferation of various human breast cancer and pancreatic cancer cells. The identified compound HJC0416 significantly suppresses STAT3 promoter activity and STAT3 phosphorylation, reduces total STAT3 protein expression, induces cell growth arrest and early apoptosis in triple-negative breast cancer cell line MDA-MB-231. HJC0416 also demonstrated a better efficacy in suppressing the growth of MDA-MB-231 breast xenograft tumors via intraperitoneal and oral administrative routes, with remarkably improved aqueous solubility and less toxicity than the lead compounds. We further demonstrated that p70S6K and MAPK pathways mediate the inhibitory effects from HJC0416 via downregulating RPS6, PDCD4 and EEF2K proteins. In conclusion, the new anticancer agent HJC0416 inhibits the growth of breast cancer xenografts via suppressing STAT3 expression and its phosphorylation. Citation Format: Ailian Xiong, Haijun Chen, Zhengduo Yang, Guoshuai Cai, Lili Wang, Chunyong Ding, Grace G. Xu, Christopher Wild, Na Ye, Ivan P. Uray, Jia Zhou, Qiang Shen. Anticancer agent HJC0416 inhibits the growth of breast cancer xenografts via downregulating STAT3 signaling. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3805. doi:10.1158/1538-7445.AM2014-3805