Alcohol reshapes a liver premetastatic niche for cancer by extra- and intrahepatic crosstalk-mediated immune evasion.

Cancer metastatic organotropism is still a mystery. The liver is known to be susceptible to cancer metastasis and alcoholic injury. However, it is unclear whether and how alcohol facilitates liver metastasis and how to intervene. Here, we show that alcohol preferentially promotes liver metastasis in colon-cancer-bearing mice and post-surgery pancreatic cancer patients. The mechanism is that alcohol triggers an extra- and intrahepatic crosstalk to reshape an immunosuppressive liver microenvironment. In detail, alcohol upregulates extrahepatic IL-6 and hepatocellular IL-6 receptor expression, resulting in hepatocyte STAT3 signaling activation and downstream lipocalin-2 (Lcn2) upregulation. Furthermore, LCN2 promotes T cell-exhaustion neutrophil recruitment and cancer cell epithelial plasticity. In contrast, knocking out hepatocellular Stat3 or systemic Il6 in alcohol-treated mice preserves the liver microenvironment and suppresses liver metastasis. This mechanism is reflected in hepatocellular carcinoma patients, in that alcohol-associated signaling elevation in noncancerous liver tissue indicates adverse prognosis. Accordingly, we discover a novel application for BBI608, a small molecular STAT3 inhibitor that can prevent liver metastasis. BBI608 pretreatment protects the liver and suppresses alcohol-triggered premetastatic niche formation. In conclusion, under extra- and intrahepatic crosstalk, the alcoholic injured liver forms a favorable niche for cancer cell metastasis, while BBI608 is a promising anti-metastatic agent targeting such microenvironments.

Ipilimumab, Pembrolizumab, or Nivolumab in Combination with BBI608 in Patients with Advanced Cancers Treated at MD Anderson Cancer Center.

Background: BBI608 is an investigational reactive oxygen species generator that affects several molecular pathways. We investigated BBI608 combined with immune checkpoint inhibitors in patients with advanced cancers. Methods: BBI608 (orally twice daily) was combined with ipilimumab (3 mg/kg IV every 3 weeks); pembrolizumab (2 mg/kg IV every 3 weeks); or nivolumab (3 mg/kg IV every 4 weeks). We assessed the safety, antitumor activity and the pharmacokinetic profile of BBI combined with immunotherapy. Results: From 1/2017 to 3/2017, 12 patients were treated (median age, 54 years; range, 31-78; 6 men). Treatment was overall well tolerated. No dose-limiting toxicity was observed. The most common adverse events were diarrhea (5 patients: grade (G)1-2, n = 3; G3, n = 2) and nausea (4 patients, all G1). Prolonged disease stabilization was noted in five patients treated with BBI608/nivolumab lasting for 12.1, 10.1, 8.0, 7.7 and 7.4 months. The median progression-free survival was 2.73 months. The median overall survival was 7.56 months. Four patients had prolonged overall survival (53.0, 48.7, 51.9 and 48.2 months). Conclusions: Checkpoint inhibitors combined with BBI608 were well tolerated. Several patients had prolonged disease stabilization and overall survival. Prospective studies to elucidate the mechanisms of response and resistance to BBI608 are warranted.

STAT3 inhibitor BBI608 enhances the antitumor effect of gefitinib on EGFR-mutated non-small cell lung cancer cells.

Gefitinib is known as epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI) while an increasing number of patients with non-small cell lung cancer (NSCLC) are becoming resistant to EGFR-TKI. Therefore, innovative methods are urgently needed to overcome primary and acquired resistance to EGFR-TKIs in NSCLC patients. The viability of HCC827 cells and HCC827 Ge-resistant (Ge-r) cells treated with gefitinib and/or STAT3 inhibitor and/or Overexpression (Oe)-ROR1 was detected by CCK-8 assay. The colony formation, invasion, migration and apoptosis of HCC827 Ge-r cells treated with gefitinib and/or STAT3 inhibitor and/or Oe-ROR1 transfection were, respectively, detected by clone formation assay, transwell assay, wound healing assay and flow cytometry analysis. The protein expressions of EGFR, STAT3, invasion and migration-related proteins, ROR1/ABCB1/P53 pathway and apoptosis-related proteins were analyzed by Western blot analysis. The transfection effect of Oe-ROR1 in HCC827 Ge-r cells was confirmed by qRT-PCR and Western blot analysis. In vivo animal experiment was used to confirm the role of STAT3 in improving the sensitivity of HCC827 Ge-r cells to gefitinib. As a result, after treatment of gefitinib, the viability of HCC827 cells was lower than that of HCC827 Ge-r cells and the expression of p/t-EGFR and p/t-STAT3 was decreased in HCC827 cells and HCC827 Ge-r cells after treatment of gefitinib. STAT3 inhibitor BBI608 enhanced the ability of gefitinib to inhibit viability, invasion and migration while promoting apoptosis of HCC827 Ge-r cells treated with gefitinib, which was partially reversed by ROR1 overexpression. STAT3 inhibitor further down-regulated the expression of MMP2, MMP9, ROR1, ABCB1 and BCl2, while up-regulated the expression of p53, bax and cleaved caspase3 in HCC827 Ge-r cells treated with gefitinib, which was partially reversed by ROR1 overexpression. In vivo experiment, STAT3 inhibitor further suppressed the size of NSCLC tissues, and further down-regulated the expression of ROR1 and ABCB1 while up-regulated the expression of p53 in NSCLC tissues. In conclusion, STAT3 inhibitor enhanced the antitumor effect of gefitinib on EGFR-mutated NSCLC cells through regulating ROR1/ABCB1/P53 pathway.

Design, synthesis and biological evaluation of novel potent STAT3 inhibitors based on BBI608 for cancer therapy.

Persistently activated signal transducer and activator of transcription 3 (STAT3) plays an important role in the development of multiple cancers, and therefore is a potential therapeutic target for cancer prevention. Herein, we report the rational design, synthesis, and biological evaluation of novel potent STAT3 inhibitors based on BBI608. Among them, compound A11 exhibited the most potent in vitro tumor cell growth inhibitory activities toward MDA-MB-231, MDA-MB-468 and HepG2 cells with IC50 values as low as 0.67 ± 0.02 µM, 0.77 ± 0.01 µM and 1.24 ± 0.16 µM, respectively. Fluorescence polarization (FP) assay validated the binding of compound A11 in STAT3 SH2 domain with the IC50 value of 5.18 µM. Further mechanistic studies indicated that A11 inhibited the activation of STAT3 (Y705), and thus reduced the expression of STAT3 downstream genes CyclinD1 and C-Myc. Simultaneously, it induced cancer cell S phase arrest and apoptosis in a concentration-dependent manner. An additional in vivo study revealed that A11 suppressed the MDA-MB-231 xenograft tumor growth in mice at the dose of 10 mg/kg (i.p.) without obvious body-weight loss. Finally, molecular docking study further elucidated the binding mode of A11 in STAT3 SH2 domain.

Napabucasin (BBI 608), a potent chemoradiosensitizer in rectal cancer.

BACKGROUND: The induction of reactive oxygen species (ROS) represents a viable strategy for enhancing the activity of radiotherapy. The authors hypothesized that napabucasin would increase ROS via its ability to inhibit NAD(P)H:quinone oxidoreductase 1 and potentiate the response to chemoradiotherapy in rectal cancer via distinct mechanisms. METHOD: Proliferation studies, colony formation assays, and ROS levels were measured in HCT116 and HT29 cell lines treated with napabucasin, chemoradiation, or their combination. DNA damage (pγH2AX), activation of STAT, and downstream angiogenesis were evaluated in both untreated and treated cell lines. Finally, the effects of napabucasin, chemoradiotherapy, and their combination were assessed in vivo with subcutaneous mouse xenograft models. RESULTS: Napabucasin significantly potentiated the growth inhibition of chemoradiation in both cell lines. Napabucasin increased ROS generation. Inhibition of ROS by N-acetylcysteine decreased the growth inhibitory effect of napabucasin alone and in combination with chemoradiotherapy. Napabucasin significantly increased pγH2AX in comparison with chemoradiotherapy alone. Napabucasin reduced the levels of pSTAT3 and VEGF and inhibited angiogenesis through an ROS-mediated effect. Napabucasin significantly potentiated the inhibition of growth and blood vessel formation by chemoradiotherapy in mouse xenografts. CONCLUSION: Napabucasin is a radiosensitizer with a novel mechanism of action: increasing ROS production and inhibiting angiogenesis. Clinical trials testing the addition of napabucasin to chemoradiotherapy in rectal cancer are needed.

STAT3 inhibitory activity of naphthoquinones isolated from Tabebuia avellanedae.

The extract of Tabebuia avellanedae has been used as a folk medicine, and the various biological activities of T. avellanedae have been extensively studied. However, few studies have reported which natural products play a role in their biological effects. In this study, we evaluated representative naphthoquinones isolated from T. avellanedae and found that furanonaphthoquinones were the key structures required to exhibit STAT3 phosphorylation inhibitory activities. Our SAR analysis indicated that removal of a hydroxyl group enhanced the STAT3 phosphorylation inhibitory activity. In addition, the combined results of a mobility shift assay, SH2 domain binding assay, and docking simulation by Autodock 4.2.6 suggested that (S)-5-hydroxy-2-(1-hydroxyethyl)naphtho[2,3-b]furan-4,9-dione (1) could directly bind to the hinge region of STAT3.

Targeted activation of Stat3 in combination with paclitaxel results in increased apoptosis in epithelial ovarian cancer cells and a reduced tumour burden.

OBJECTIVES: Stat3 is persistently activated in ovarian cancer cells, with a crucial role in tumour onset and progression. In this study, we examined the anti-tumour effect of a small-molecule inhibitor napabucasin (BBI608) on epithelial ovarian cancer (EOC) in vitro and in vivo, and investigated the underlying molecular mechanism of this drug in combination with paclitaxel. MATERIALS AND METHODS: A total of 156 ovarian cancer patient samples were analysed to determine the correlation between pStat3 expression in tumour cells and the prognosis of EOC patients. The anti-tumour effect of BBI608 and/or paclitaxel on ovarian cancer in vitro was evaluated by CCK-8, flow cytometry, Western blot and transwell assays. An in vivo intraperitoneal model was performed to confirm the effect of BBI608 on pStat3-mediated peritoneal metastasis when combined with paclitaxel. RESULTS: Patients with high expression of pStat3 had poorer overall survival and progression-free survival than those with low pStat3 expression. The synergy of BBI608 in combination with paclitaxel exerted dramatic growth inhibition and induced apoptosis in EOC cell lines. In vivo, the combination of two drugs significantly decreased intraperitoneal tumour burden and ascites volume, prolonged survival of tumour-bearing mice compared with each monotherapy; these results were associated with downregulation of phospho-Stat3 and activation of apoptosis pathway. CONCLUSIONS: Targeting the activation of Stat3 may be a potential therapeutic approach for EOC by acting synergistically with paclitaxel.

A self-enforcing HOXA11/Stat3 feedback loop promotes stemness properties and peritoneal metastasis in gastric cancer cells.

Rationale: Peritoneal metastasis is one of the most common and life-threatening metastases in gastric cancer patients. The disseminated gastric cancer cells forming peritoneal metastasis exhibit a variety of characteristics that contrast with those of adjacent epithelial cell of gastric mucosa and even primary gastric cancer cells. We hypothesized that the gene expression profiles of peritoneal foci could reveal the identities of genes that might function as metastatic activator. Methods: In this study, we show, using in vitro, in vivo, in silico and gastric cancer tissues studies in humans and mice, that Homoebox A11 (HOXA11) potently promote peritoneal metastasis of gastric cancer cells. Results: Its mechanism of action involves alternation of cancer stemness and subsequently enhancement of the adhesion, migration and invasion and anti-apoptosis. This is achieved, mainly, through formation of a positive feedback loop between HOXA11 and Stat3, which is involved in the stimulation of Stat3 signaling pathway. Conclusions: These observations uncover a novel peritoneal metastatic activator and demonstrate the association between HOXA11, Stat3 and cancer stemness of gastric cancer cells, thereby revealing a previously undescribed mechanism of peritoneal metastasis.

STAT3 induces G9a to exacerbate HER3 expression for the survival of epidermal growth factor receptor-tyrosine kinase inhibitors in lung cancers.

BACKGROUND: HER3 mediates drug resistance against epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs), resulting in tumor relapse in lung cancers. Previously, we demonstrated that EGFR induces HER3 overexpression, which facilitates the formation of cancer stem-like tumorspheres. However, the cellular mechanism through which EGFR regulates HER3 expression remains unclear. We hypothesized that EGFR downstream of STAT3 participates in HER3 expression because STAT3 contributes to cancer stemness and survival of EGFR-TKI resistant cancers. METHODS: First, RNAseq was used to uncover potential genes involved in the formation of lung cancer HCC827-derived stem-like tumorspheres. EGFR-positive lung cancer cell lines, including HCC827, A549, and H1975, were individually treated with a panel containing 172 therapeutic agents targeting stem cell-associated genes to search for potential agents that could be applied against EGFR-positive lung cancers. In addition, gene knockdown and RNAseq were used to investigate molecular mechanisms through which STAT3 regulates tumor progression and the survival in lung cancer. RESULTS: BBI608, a STAT3 inhibitor, was a potential therapeutic agent that reduced the cell viability of EGFR-positive lung cancer cell lines. Notably, the inhibitory effects of BBI608 were similar with those associated with YM155, an ILF3 inhibitor. Both compounds reduced G9a-mediated HER3 expression. We also demonstrated that STAT3 upregulated G9a to silence miR-145-5p, which exacerbated HER3 expression in this study. CONCLUSIONS: The present study revealed that BBI608 could eradicate EGFR-positive lung cancers and demonstrated that STAT3 enhanced the expression of HER3 through miR-145-5p repression by G9a, indicating that STAT3 is a reliable therapeutic target against EGFR-TKI-resistant lung cancers.

Napabucasin (BBI608) eliminate AML cells in vitro and in vivo via inhibition of Stat3 pathway and induction of DNA damage.

Acute myeloid leukemia (AML) is a heterogeneous malignancy of hematopoietic stem cells with poor clinical outcome despite recent improvements in chemotherapy and stem cell transplantation regimens. Thus, new therapeutic agents are urgently needed in order to prolong the disease-free survival of AML patients in clinic. Here, we report that BBI608 is highly active against diverse AML cell lines in vitro and primary samples obtained from patients with AML ex vivo, as well as effective in vivo in AML xenograft models. Meanwhile, the anti-AML property of BBI608 is closely associated with the inhibition of Stat3 pathway and induction of DNA damage. Of note, BBI608 combined with Bcl-2 inhibitor (i.e., ABT-199) exerts a significantly enhanced anti-leukemia effect in BBI608-resistant cell line Kasumi-1. Together, the present findings suggest that BBI608 might represent a potential candidate agent for AML treatment.

Therapeutic Targeting Strategies of Cancer Stem Cells in Gastrointestinal Malignancies.

Cancer stem cells (CSCs) are thought to be a distinct population of cells within a tumor mass that are capable of asymmetric division and known to have chemoresistant characteristics. The description and identification of CSC models in cancer growth and recurrence has inspired the design of novel treatment strategies to overcome treatment resistance by targeting both CSCs and non-CSC tumor cells. Several cellular signaling pathways have been described as playing a role in the induction and maintenance of stemness in CSCs, such as the Wnt/ß-catenin, Notch, STAT3, and Hedgehog pathways. In this review, we aim to review some of the ongoing CSC therapeutic targeting strategies in gastrointestinal malignancies.

The Cancer Stem Cell Inhibitor Napabucasin (BBI608) Shows General Cytotoxicity in Biliary Tract Cancer Cells and Reduces Cancer Stem Cell Characteristics.

Biliary tract cancer is a devastating disease with limited therapeutic options. The involvement of cancer stem cells in biliary tract cancer is likely. Napabucasin is a previously described cancer stem cell inhibitor that is currently being used in clinical trials. However, data regarding napabucasin and biliary tract cancer are not available yet. We tested the general cytotoxic effect of napabucasin on a comprehensive biliary tract cancer in vitro model, using resazurin assay and Annexin V/7-AAD staining. The effect of napabucasin on functional cancer stem cell characteristics was analyzed via soft agar assay, aldehyde-dehydrogenase-1 assay, measurement of surface CD326 expression, and measurement of clonogenic growth. The evaluation of the effect of napabucasin on cancer stem cell protein and gene expression was performed using Western blot and reverse transcription-PCR-based human cancer stem cell array. Napabucasin showed a concentration- and cell line-dependent cytotoxic effect, and increased the apoptotic and necrotic cell fractions. Treatment with napabucasin significantly reduced the formation of tumor spheres and clonogenic growth, as well as CD326 surface expression. Expression of cancer stem cell markers were reduced following napabucasin treatment on the protein and mRNA levels. Our study provides first data regarding napabucasin as a promising substance for the treatment of biliary tract cancer.

CanStem111P trial: a Phase III study of napabucasin plus nab-paclitaxel with gemcitabine.

Napabucasin (also known as BBI-608 or BBI608) is an investigational, oral agent hypothesized to inhibit multiple oncogenic pathways. In this article, we describe the design and rationale for the CanStem111P clinical trial, a multicenter, randomized, open-label, Phase III study designed to determine the efficacy and safety of combining napabucasin with nab-paclitaxel and gemcitabine for first-line treatment of patients with metastatic pancreatic adenocarcinoma (NCT02993731). Patients were randomized in a 1:1 fashion to receive weekly gemcitabine and nab-paclitaxel with or without napabucasin. The results of this study will help define the role of this novel agent in the management of advanced pancreatic cancer.

BBI608 inhibits cancer stemness and reverses cisplatin resistance in NSCLC.

Non-small cell lung cancer (NSCLC) is the most common cause of cancer-related deaths worldwide. While partial or complete tumor regression can be achieved in patients, particularly with cisplatin-based strategies, these initial responses are frequently short-lived and are followed by tumor relapse and chemoresistance. Identifying the root of cisplatin resistance in NSCLC and elucidating the mechanism(s) of tumor relapse, is of critical importance in order to determine the point of therapeutic failure, which in turn, will aid the discovery of novel therapeutics, new combination strategies and a strategy to enhance the efficacy of current chemotherapeutics. It has been hypothesized that cancer stem cells (CSCs) may be the initiating factor of resistance. We have previously identified and characterized an aldehyde dehydrogenase 1 CSC subpopulation in cisplatin resistant NSCLC. BBI608 is a small molecule STAT3 inhibitor known to suppress cancer relapse, progression and metastasis. Here, we show that BBI608 can inhibit stemness gene expression, deplete CSCs and overcome cisplatin resistance in NSCLC.

Design, synthesis and activity of BBI608 derivatives targeting on stem cells.

STAT3 plays a vital role in maintaining the self-renewal of tumor stem cells. BBI608, a small molecule identified by its ability to inhibit gene transcription driven by STAT3 and cancer stemness properties, can inhibit stemness gene expression and kill stemness-high cancer cells isolated from a variety of cancer types. In order to improve the pharmacokinetic properties of BBI608 and the antitumor activity, a series of BBI608 derivatives were designed and synthesized here. Most of these compounds were more potent than BBI608 on HepG2 cells, compound LD-8 had the most potent inhibitory activity among them and was 5.4-fold more potent than BBI608 (IC50 = 11.2 µM), but had considerable activity on normal liver cells L-02. Compounds LD-17 (IC50 = 3.5 µM) and LD-19 (IC50 = 2.9 µM) were found to possess significant inhibitory activities and good selectivity. The results showed that compound LD-19 was worthy to investigate further as a lead compound according to its potent inhibitory activity, ideal ClogP value and better water solubility.

A clinical trial protocol paper discussing the BRIGHTER study.

Napabucasin is a novel oral first-in-class cancer stemness inhibitor. Preclinical and early phase clinical trials showed promising antitumor efficacy signals for napabucasin in a variety of malignancies. In this article, we describe the design and rationale for the now completed BRIGHTER trial, a multicenter, randomized, placebo-controlled, Phase III study designed to determine the efficacy and safety of combining napabucasin with paclitaxel in previously treated patients with advanced gastric and gastroesophageal junction adenocarcinoma (NCT02178956). Patients were randomized in a 1:1 fashion to receive weekly paclitaxel with either napabucasin or placebo. The study failed to achieve its primary end point of overall survival in the intention to treat population. Ongoing analysis of the secondary end points includes progression-free survival, objective response rate, disease control rate, the safety of the combination therapy and evaluation of efficacy in the biomarker-positive subpopulation.

The Use of Naphthoquinones and Furano-naphthoquinones as Antiinvasive Agents.

BACKGROUND: Cancer is a leading cause of mortality in the world and metastasis is to blame. A number of naphthoquinones (NQs) have shown ability to reduce cancer stemness and metastatic potential. Furano-naphthoquinones (FNQs), which is a class of NQ characterized by the incorporation of an additional furan ring, have demonstrated improved anti-cancer potency as compared to the other classes of NQs. OBJECTIVE: In this study, the natural origins, synthetic routes and derivatives of migrastatic NQs were reviewed. The anti-invasive and anti-metastatic mechanisms of NQs and the more powerful FNQs in targeting cancer were also discussed. METHODS: The articles related to the anti-invasive mechanisms of NQs were comprehensively reviewed. The plant origins, synthetic routes and antitumor effects of more than 360 FNQs were also covered and presented according to their chemical structures. RESULTS: Anti-cancer NQs inhibit cancer invasion by acting on epithelial-mesenchymal transition (EMT), cancer stem cells (CSCs) and signal transducer and activator of transcription 3 (STAT3) signaling. BBI608, a natural FNQ, has entered phases I and II clinical trials. It has been regarded as a potential candidate for new-generation lead compound acting directly on CSCs to overcome the problem of chemotherapy resistance. Apart from the plant-derived FNQs, there are a number of synthetic FNQs that were found to intervene in cancer invasion and metastasis. CONCLUSION: The anti-invasive mechanisms of NQs have been thoroughly studied. FNQs generally show higher anti-cancer activity than that of NQs. The mechanisms of action of FNQs are worth further investigation.

Suppression of cancer relapse and metastasis by inhibiting cancer stemness.

Partial or even complete cancer regression can be achieved in some patients with current cancer treatments. However, such initial responses are almost always followed by relapse, with the recurrent cancer being resistant to further treatments. The discovery of therapeutic approaches that counteract relapse is, therefore, essential for advancing cancer medicine. Cancer cells are extremely heterogeneous, even in each individual patient, in terms of their malignant potential, drug sensitivity, and their potential to metastasize and cause relapse. Indeed, hypermalignant cancer cells, termed cancer stem cells or stemness-high cancer cells, that are highly tumorigenic and metastatic have been isolated from cancer patients with a variety of tumor types. Moreover, such stemness-high cancer cells are resistant to conventional chemotherapy and radiation. Here we show that BBI608, a small molecule identified by its ability to inhibit gene transcription driven by Stat3 and cancer stemness properties, can inhibit stemness gene expression and block spherogenesis of or kill stemness-high cancer cells isolated from a variety of cancer types. Moreover, cancer relapse and metastasis were effectively blocked by BBI608 in mice. These data demonstrate targeting cancer stemness as a novel approach to develop the next generation of cancer therapeutics to suppress cancer relapse and metastasis.