Polyoxypregnanes as safe, potent, and specific ABCB1-inhibitory pro-drugs to overcome multidrug resistance in cancer chemotherapy in vitro and in vivo.

Multidrug resistance (MDR) mediated by ATP binding cassette subfamily B member 1 (ABCB1) is significantly hindering effective cancer chemotherapy. However, currently, no ABCB1-inhibitory drugs have been approved to treat MDR cancer clinically, mainly due to the inhibitor specificity, toxicity, and drug interactions. Here, we reported that three polyoxypregnanes (POPs) as the most abundant constituents of Marsdenia tenacissima (M. tenacissima) were novel ABCB1-modulatory pro-drugs, which underwent intestinal microbiota-mediated biotransformation in vivo to generate active metabolites. The metabolites at non-toxic concentrations restored chemosensitivity in ABCB1-overexpressing cancer cells via inhibiting ABCB1 efflux activity without changing ABCB1 protein expression, which were further identified as specific non-competitive inhibitors of ABCB1 showing multiple binding sites within ABCB1 drug cavity. These POPs did not exhibit ABCB1/drug metabolizing enzymes interplay, and their repeated administration generated predictable pharmacokinetic interaction with paclitaxel without obvious toxicity in vivo. We further showed that these POPs enhanced the accumulation of paclitaxel in tumors and overcame ABCB1-mediated chemoresistance. The results suggested that these POPs had the potential to be developed as safe, potent, and specific pro-drugs to reverse ABCB1-mediated MDR. Our work also provided scientific evidence for the use of M. tenacissima in combinational chemotherapy.

Efficacy of annexin A3 blockade in sensitizing hepatocellular carcinoma to sorafenib and regorafenib.

BACKGROUND & AIMS: Advanced hepatocellular carcinoma (HCC) is a lethal malignancy with limited treatment options. Sorafenib is the only FDA-approved first-line targeted drug for advanced HCC, but its effect on patient survival is limited. Further, patients ultimately present with disease progression. A better understanding of the causes of sorafenib resistance, enhancing the efficacy of sorafenib and finding a reliable predictive biomarker are crucial to achieve efficient control of HCC. METHODS: The functional effects of ANXA3 in conferring sorafenib resistance to HCC cells were analyzed in apoptotic and tumorigenicity assays. The role of ANXA3/PKCδ-mediated p38 signaling, and subsequently altered autophagic and apoptotic events, was assessed by immunoprecipitation, immunoblotting, immunofluorescence and transmission electron microscopy assays. The prognostic value of ANXA3 in predicting response to sorafenib was evaluated by immunohistochemistry. The therapeutic value of targeting ANXA3 to combat HCC with anti-ANXA3 monoclonal antibody alone or in combination with sorafenib/regorafenib was investigated ex vivo and in vivo. RESULTS: ANXA3 conferred HCC cells with resistance to sorafenib. ANXA3 was found enriched in sorafenib-resistant HCC cells and patient-derived xenografts. Mechanistically, overexpression of ANXA3 in sorafenib-resistant HCC cells suppressed PKCδ/p38 associated apoptosis and activated autophagy for cell survival. Clinically, ANXA3 expression correlated positively with the autophagic marker LC3B in HCC and was associated with a worse overall survival in patients who went on to receive sorafenib treatment. Anti-ANXA3 monoclonal antibody therapy combined with sorafenib/regorafenib impaired tumor growth in vivo and significantly increased survival. CONCLUSION: Anti-ANXA3 therapy in combination with sorafenib/regorafenib represents a novel therapeutic strategy for HCC treatment. ANXA3 represents a useful predictive biomarker to stratify patients with HCC for sorafenib treatment. LAY SUMMARY: This study represents the most extensive pre-clinical characterization of anti-ANXA3 monoclonal antibodies for the treatment of hepatocellular carcinoma to date. These results support the clinical trial development of anti-ANXA3 antibodies in combination with sorafenib/regorafenib. Further studies will optimize patient target selection and identify the best treatment combinations.

TP53INP1 Downregulation Activates a p73-Dependent DUSP10/ERK Signaling Pathway to Promote Metastasis of Hepatocellular Carcinoma.

Identifying critical factors involved in the metastatic progression of hepatocellular carcinoma (HCC) may offer important therapeutic opportunities. Here, we report that the proapoptotic stress response factor TP53INP1 is often selectively downregulated in advanced stage IV and metastatic human HCC tumors. Mechanistic investigations revealed that TP53INP1 downregulation in early-stage HCC cells promoted metastasis via DUSP10 phosphatase-mediated activation of the ERK pathway. The DUSP10 promoter included putative binding sites for p73 directly implicated in modulation by TP53INP1. Overall, our findings show how TP53INP1 plays a critical role in limiting the progression of early-stage HCC, with implications for developing new therapeutic strategies to attack metastatic HCC. Cancer Res; 77(17); 4602-12. ©2017 AACR.

Reversal of multidrug resistance by Marsdenia tenacissima and its main active ingredients polyoxypregnanes.

ETHNOPHARMACOLOGICAL RELEVANCE: Multidrug resistance (MDR) of cancer is often associated with the overexpression of ATP-binding cassette (ABC) transporters, such as P-glycoprotein (P-gp), multidrug resistance-associated protein-1 (MRP-1) and breast cancer resistance protein (BCRP or ABCG2), in cancer cells, which facilitates the active efflux of a wide variety of chemotherapeutic drugs out of the cells. Marsdenia tenacissima is a traditional Chinese medicinal herb that has long been clinically used for treatment of cancers, particularly in combinational use with anticancer drugs. Polyoxypregnanes (POPs) are identified as main constituents of this herb, and three of them have been reported to exhibit P-gp modulatory effect and thus reverse MDR. Therefore, it is of great necessity to investigate more POPs that have potential to reverse transporters-mediated MDR. AIM OF THE STUDY: We aimed to identify POPs as the chemical basis responsible for circumventing ABC transporters-mediated MDR by M. tenacissima. MATERIALS AND METHODS: The MDR reversal effects of M. tenacissima crude extract together with a series of isolated POPs were evaluated on several MDR cancer cell lines that overexpress P-gp, MRP1 or ABCG2. The activities of P-gp, MRP1 and ABCG2 were determined by the flow cytometry-based substrate efflux assay. Molecular docking of POPs to a three-dimensional human P-gp homology structure was also performed. RESULTS: The crude extract of M. tenacissima was firstly found to circumvent P-gp-mediated MDR. Then, 11 polyoxypregnane compounds (POPs) isolated from this herb were found to overcome P-gp-, MRP1- and/or ABCG2-mediated MDR. Further mechanistic study delineated that the reversal of MDR by these POPs was due to significant increase in the intracellular concentrations of the substrate anticancer drugs via their inhibition of different ABC transporter-mediated efflux activities. Furthermore, molecular docking revealed that POPs with P-gp modulatory effect bound to P-gp and fitted well into the cavity between the alpha and beta subunit of P-gp via forming hydrogen bonds. In addition, several key structural determinants for inhibition of P-gp, MRP1 or ABCG2 by POPs were illustrated. CONCLUSIONS: Our findings advocated the rational use of M. tenacissima to enhance efficacies of conventional anticancer drugs in tumors with ABC drug transporters-mediated MDR. Furthermore, 11 POPs were found to contribute to MDR reversal effect of M. tenacissima via inhibition of different ABC efflux transporters.

Octamer 4/microRNA-1246 signaling axis drives Wnt/ß-catenin activation in liver cancer stem cells.

Wnt/ß-catenin signaling is activated in CD133 liver cancer stem cells (CSCs), a subset of cells known to be a root of tumor recurrence and therapy resistance in hepatocellular carcinoma (HCC). However, the regulatory mechanism of this pathway in CSCs remains unclear. Here, we show that human microRNA (miRNA), miR-1246, promotes cancer stemness, including self-renewal, drug resistance, tumorigencity, and metastasis, by activation of the Wnt/ß-catenin pathway through suppressing the expression of AXIN2 and glycogen synthase kinase 3ß (GSK3ß), two key members of the ß-catenin destruction complex. Clinically, high endogenous and circulating miR-1246 was identified in HCC clinical samples and correlated with a worse prognosis. Further functional analysis identified octamer 4 (Oct4) to be the direct upstream regulator of miR-1246, which cooperatively drive ß-catenin activation in liver CSCs. CONCLUSION: These findings uncover the noncanonical regulation of Wnt/ß-catenin in liver CSCs by the Oct4/miR-1246 signaling axis, and also provide a novel diagnostic marker as well as therapeutic intervention for HCC. (Hepatology 2016;64:2062-2076).

Cancer-Associated Fibroblasts Regulate Tumor-Initiating Cell Plasticity in Hepatocellular Carcinoma through c-Met/FRA1/HEY1 Signaling.

Like normal stem cells, tumor-initiating cells (T-ICs) are regulated extrinsically within the tumor microenvironment. Because HCC develops primarily in the context of cirrhosis, in which there is an enrichment of activated fibroblasts, we hypothesized that cancer-associated fibroblasts (CAFs) would regulate liver T-ICs. We found that the presence of α-SMA(+) CAFs correlates with poor clinical outcome. CAF-derived HGF regulates liver T-ICs via activation of FRA1 in an Erk1,2-dependent manner. Further functional analysis identifies HEY1 as a direct downstream effector of FRA1. Using the STAM NASH-HCC mouse model, we find that HGF-induced FRA1 activation is associated with the fibrosis-dependent development of HCC. Thus, targeting the CAF-derived, HGF-mediated c-Met/FRA1/HEY1 cascade may be a therapeutic strategy for the treatment of HCC.

Neuropilin-2 promotes tumourigenicity and metastasis in oesophageal squamous cell carcinoma through ERK-MAPK-ETV4-MMP-E-cadherin deregulation.

Oesophageal squamous cell carcinoma (ESCC) is the most common histological subtype of oesophageal cancer. The disease is particularly prevalent in southern China. The incidence of the disease is on the rise and its overall survival rate remains dismal. Identification and characterization of better molecular markers for early detection and therapeutic targeting are urgently needed. Here, we report levels of transmembrane and soluble neuropilin-2 (NRP2) to be significantly up-regulated in ESCC, and to correlate positively with advanced tumour stage, lymph node metastasis, less favourable R category and worse overall patient survival. NRP2 up-regulation in ESCC was in part a result of gene amplification at chromosome 2q. NRP2 overexpression promoted clonogenicity, angiogenesis and metastasis in ESCC in vitro, while NRP2 silencing by lentiviral knockdown or neutralizing antibody resulted in a contrary effect. This observation was extended in vivo in animal models of subcutaneous tumourigenicity and tail vein metastasis. Mechanistically, overexpression of NRP2 induced expression of ERK MAP kinase and the transcription factor ETV4, leading to enhanced MMP-2 and MMP-9 activity and, as a consequence, suppression of E-cadherin. In summary, NRP2 promotes tumourigenesis and metastasis in ESCC through deregulation of ERK-MAPK-ETV4-MMP-E-cadherin signalling. NRP2 represents a potential diagnostic or prognostic biomarker and therapeutic target for ESCC. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

C-terminal truncated hepatitis B virus X protein promotes hepatocellular carcinogenesis through induction of cancer and stem cell-like properties.

Tumor relapse after chemotherapy typifies hepatocellular carcinoma (HCC) and is believed to be attributable to residual cancer stem cells (CSCs) that survive initial treatment. Chronic infection with hepatitis B virus (HBV) has long been linked to the development of HCC. Upon infection, random HBV genome integration can lead to truncation of hepatitis B virus X (HBx) protein at the C-terminus. The resulting C-terminal-truncated HBx (HBx-ΔC) was previously shown to confer enhanced invasiveness and diminished apoptotic response in HCC cells. Here, we found HBx-ΔC to promote the appearance of a CD133 liver CSC subset and confer cancer and stem cell-like features in HCC. HBx-ΔC was exclusively detected in HCC cell lines that were raised from patients presented with a HBV background with concomitant CD133 expression. Stable overexpression of the naturally occurring HBx-ΔC mutants, HBx-Δ14 or HBx-Δ35, in HCC cells Huh7 and immortalized normal liver cells MIHA resulted in a significant increase in the cells ability to self-renew, resist chemotherapy and targeted therapy, migrate and induce angiogenesis. MIHA cells with the mutants stably overexpressed also resulted in the induction of CD133, mediated through STAT3 activation. RNA sequencing profiling of MIHA cells with or without HBx-ΔC mutants stably overexpressed identified altered FXR activation. This, together with rescue experiments using a selective FXR inhibitor suggested that C-terminal truncated HBx can mediate cancer stemness via FXR activation. Collectively, we find C-terminal truncated HBx mutants to confer cancer and stem cell-like features in vitro and to play an important role in driving tumor relapse in HCC.

Polyoxypregnane steroids with an open-chain sugar moiety from Marsdenia tenacissima and their chemoresistance reversal activity.

A polyoxypregnane aglycone, 12ß-O-acetyl-11α-O-isobutyryltenacigenin B, and four polyoxypregnane glycosides with a pachybionic acid ester moiety, 12ß-O-acetyl-3-O-(6-deoxy-3-O-methyl-ß-D-allopyranosyl-(1→4)-ß-D-oleandronyl)-11α-O-isobutyryltenacigenin B, 12ß-O-acetyl-3-O-(6-deoxy-3-O-methyl-ß-D-allopyranosyl-(1→4)-ß-D-oleandronyl)-11α-O-tigloyltenacigenin B, 12ß-O-acetyl-3-O-(6-deoxy-3-O-methyl-ß-D-allopyranosyl-(1→4)-ß-D-oleandronyl)-11α-O-2-methylbutyryltenacigenin B, and 12ß-O-acetyl-3-O-(ß-D-glucopyranosyl-(1→4)-6-deoxy-3-O-methyl-ß-D-allopyranosyl-(1→4)-D-oleandronyl)-11α-O-tigloyltenacigenin B, were isolated from the canes of Marsdenia tenacissima, together with a disaccharide derivative. Their structures were elucidated by extensive spectroscopic analysis, and the absolute configurations were further determined by X-ray crystallographic analysis. With the exception of the disaccharide derivative, all five compounds are unusual naturally occurring polyoxypregnane glycosides bearing an open-chain sugar moiety. Two of these exhibit a wide spectrum of chemoresistance reversal activity, and potential mechanisms were studied accordingly.

Polyoxypregnane steroids from the stems of Marsdenia tenacissima.

A new polyoxypregnane aglycone, tenacigenin D (1), and seven new C21 steroid glycosides, tenacissimosides D-J (2-8), were isolated from the stems of Marsdenia tenacissima. Their structures were determined by interpretation of their 1D and 2D NMR and other spectroscopic data, as well as by comparison with published values for related known compounds. Compound 1 was found to circumvent P-glycoprotein (P-gp)-mediated multidrug resistance through an inhibitory effect on P-gp with a similar potency to verapamil. In addition, compound 1 potentiated the activity of erlotinib and gefitinib in epidermal growth factor receptor tyrosine kinase inhibitor (EGFR TKI)-resistant non-small-cell lung cancer cells.

Regulatory role of miR-142-3p on the functional hepatic cancer stem cell marker CD133.

Tumor relapse after therapy typifies hepatocellular carcinoma (HCC) and is believed to be attributable to residual cancer stem cells (CSCs) that survive treatment. We have previously identified a CSC population derived from HCC that is characterized by CD133. Despite our growing knowledge of the importance of this subset of cells in driving HCC, the regulatory mechanism of CD133 is not known. Epigenetic changes are believed to be essential in the control of cancer and stem cells. Here, we report the epigenetic regulation of CD133 by miR-142-3p. The interaction between CD133 and miR-142-3p was identified by in silico prediction and substantiated by luciferase reporter analysis. Expression of CD133 was found to be inversely correlated with miR-142-3p in HCC clinical samples as well as in cell lines. Importantly, lower miR-142-3p expression in HCC was significantly associated with worst survival. Functional studies with miR-142-3p stably transduced in HCC cells demonstrated a diminished ability to self-renew, initiate tumor growth, invade, migrate, induce angiogenesis and resist chemotherapy. Rescue experiments whereby CD133 and miR-142-3p is simultaneously overexpressed compensated the deregulated ability of the cells to confer these features. Thus, miR-142-3p directly targets CD133 to regulate its ability to confer cancer and stem cell-like features in HCC.

Clinical implications of microRNAs in liver cancer stem cells.

The prognosis of patients diagnosed with hepatocellular carcinoma (HCC) is often dismal, mainly due to late presentation, high recurrence rate, and frequent resistance to chemotherapy and radiotherapy. Accumulating evidence on the differential microRNA (miRNA) expression patterns between non-tumor and HCC tissues or between liver cancer stem cells (CSCs) and non-CSC subsets and the significant clinical implications of these differences suggest that miRNAs are a promising, non-invasive marker for the prognosis and diagnosis of the disease. This perspective article summarizes the current knowledge of miRNAs in liver CSCs and highlights the need for further investigations of the role of miRNAs in regulating liver CSC subsets for possible future clinical applications.

Reversal of P-glycoprotein-mediated multidrug resistance by a synthetic α-aminoxy peptidomimetic.

The lack of selectivity and adequate potency of currently known P-glycoprotein (P-gp) inhibitors obscured their further development for clinical use to circumvent P-gp-mediated multidrug resistance (MDR), which necessitates the investigation of novel ones with higher potency and better specificity. The present study investigated the reversal effect of a new synthetic α-aminoxy lysine-peptidomimetic (Lys-P) on P-gp-mediated MDR. Effects of Lys-P on cytotoxicity of P-gp substrate doxorubicin (Dox) and intracellular accumulation of another P-gp substrate rhodamine 123 were examined in HEK293 cells. Its interaction mechanism and effect on P-gp expression were further investigated using ATPase assay and Western blot in Caco-2 cells, respectively. Lys-P restored the cytotoxicity of Dox toward the resistant MDR1-transfected HEK293 and MCF-7 TX400 cells without affecting their corresponding parental cells. It also significantly increased intracellular accumulation (21-fold) of rhodamine 123 in HEK293 MDR1 cells. Further mechanistic studies demonstrated that in the Caco-2 cell monolayer model, Lys-P abolished the P-gp-mediated efflux of Dox due to uncompetitive inhibition of P-gp ATPase without altering P-gp expression. Our findings demonstrated that Lys-P can be used as a promising lead compound for further development into selective and efficient MDR reversing agents for combination use with P-gp substrate drugs in cancer chemotherapy.

Circumvention of multi-drug resistance of cancer cells by Chinese herbal medicines.

Multi-drug resistance (MDR) of cancer cells severely limits therapeutic outcomes. A proposed mechanism for MDR involves the efflux of anti-cancer drugs from cancer cells, primarily mediated by ATP-binding cassette (ABC) membrane transporters including P-glycoprotein. This article reviews the recent progress of using active ingredients, extracts and formulae from Chinese medicine (CM) in circumventing ABC transporters-mediated MDR. Among the ABC transporters, Pgp is the most extensively studied for its role in MDR reversal effects. While other MDR reversal mechanisms remain unclear, Pgp inhibition is a criterion for further mechanistic study. More mechanistic studies are needed to fully establish the pharmacological effects of potential MDR reversing agents.

Quantitative comparison of ginsenosides and polyacetylenes in wild and cultivated American ginseng.

Quantitative comparison of seven ginsenosides in wild and cultivated American ginseng revealed that the Rg(1)/Rd ratio presented a significantly large difference between cultivated and type-I (one of the defined chemotypes) wild American ginseng, facilitating this ratio as a characteristic marker for differentiating these two groups. Similarly, the ratio (Rg(1)+Re)/Rd, and the ratio of protopanaxatriol (PPT)-type ginsenosides to protopanaxadiol (PPD)-type ginsenosides showed a large difference between these two groups. On the other hand, type-II wild samples were found to have high Rg(1)/Rb(1) and Rg(1)/Re ratios and low panaxydol/panaxynol ratio, which is entirely different from Type-I American ginseng, but is very similar to that of Asian ginseng. This not only suggests that the chemotype should be taken into consideration properly when using these parameters for differentiating American and Asian ginseng, but also indicates that type-II wild American ginseng may have distinct pharmacological activities and therapeutic effects.