Comprehensive profiling of H-Ras signalling in angiosarcoma endothelium

The MS1/SVR system, in which MS1 represents immortalized endothelial cells and SVR represents MS1 cells transformed with oncogenic human-rat sarcoma protein (H-Ras), has been used for around 20 years as a valuable tool to study angiogenesis and carcinogenesis. Despite the use of these cells in numerous studies, a comprehensive profile of the signalling differences due to oncogenic H-Ras transformation has not been performed previously. In this study, we profiled the well-known MS1 and SVR cell lines using a combination of both Western blot and gene chip assays.

Abstract 1116: Targeting replication stress by carbazole blue- A novel strategy to treat triple negative breast cancers

Background: Triple-negative breast cancers (TNBC) are the most aggressive forms of breast cancer and almost 60% of patients with TNBCs develop chemo-resistance, leading to recurrence, poor prognosis and poor survival. TNBCs have been reported to have high levels of replication stress, which plays pivotal role in genomic instability, and therapy resistance. Targeting replication stress is an emerging approach for better TNBC treatment. Here, we evaluated the anticancer efficacy of carbazole blue (CB), a synthetic analogue of carbazole that we recently synthesized on TNBC cells growth and progression.

Experimental Design: The effect of CB on breast cancer growth was assessed in vitro as well as in orthotopic mouse xenograft and PDX-models of breast cancer. In addition, the therapeutic efficacy and safety of CB was determined in long term toxicity studies in mice and also in ex-vivo explants from breast cancer patients. The mechanism of action of CB was evaluated by performing gene expression, cell cycle, apoptosis and DNA repair studies as well as proteins involved in the above mentioned mechanisms.

Results: Our results demonstrated that CB inhibits short and long term viability of TNBC cells in a dose dependent manner without affecting normal mammary epithelial cells. We show that the systemic delivery of CB using nanoparticle-based delivery approach suppressed breast cancer growth without inducing toxicity in preclinical and PDX mouse models of triple negative breast cancer. Our long term toxicity studies reveled that CB treatment did not induce any toxicity in Balb/c mice. Using ex-vivo explants from breast cancer patients, we demonstrated that CB modulated breast cancer growth. Consistent with that, our results revealed that CB treatment induced G1/S cell cycle arrest and apoptosis in TNBCs. Interestingly, our gene expression analysis revealed that CB modulates expression and activity of several genes known to be involved in DNA replication and DNA repair machinery.

Conclusions: Our results for the first time showed the CB can serve as a novel and potent therapeutic agent for treating breast cancer in general and TNBC in particular. These findings highlight the potential of CB to be applied as a safe regimen for treating breast cancer patients. As exploiting replication stress to treat cancer is gaining major interest, compound/s that may induce replication stress and inhibit DNA repair ability of cancer cells, has immense translational potential.

Citation Format: Subapriya Rajamanickam, Kaitlyn Bates, Santosh Timilsina, JunHyoung Park, Benjamin Onyeagucha, Panneerdoss Subbarayalu, Nourhan Abdelfattah, Kwang Hwa Jung, Edward Favours, Tabrez A. Mohammad, Hung-I Harry Chen, Benny A. Kaipparettu, Yidong Chen, Jack L. Arbiser, Manjeet K Rao. Targeting replication stress by carbazole blue- A novel strategy to treat triple negative breast cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1116. doi:10.1158/1538-7445.AM2017-1116

Targeting the duality of cancer

Cancer is the second leading cause of death in the United States, and is an increasing cause of death in the developing world. While there is great heterogeneity in the anatomic site and mutations involved in human cancer, there are common features, including immortal growth, angiogenesis, apoptosis evasion, and other features, that are common to most if not all cancers. However, new features of human cancers have been found as a result of clinical use of novel “targeted therapies,” angiogenesis inhibitors, and immunotherapies, including checkpoint inhibitors. These findings indicate that cancer is a moving target, which can change signaling and metabolic features based upon the therapies offered. It is well-known that there is significant heterogeneity within a tumor and it is possible that treatment might reduce the heterogeneity as a tumor adapts to therapy and, thus, a tumor might be synchronized, even if there is no major clinical response. Understanding this concept is important, as concurrent and sequential therapies might lead to improved tumor responses and cures. We posit that the repertoire of tumor responses is both predictable and limited, thus giving hope that eventually we can be more effective against solid tumors. Currently, among solid tumors, we observe a response of 1/3 of tumors to immunotherapy, perhaps less to angiogenesis inhibition, a varied response to targeted therapies, with relapse and resistance being the rule, and a large fraction being insensitive to all of these therapies, thus requiring the older therapies of chemotherapy, surgery, and radiation. Tumor phenotypes can be seen as a continuum between binary extremes, which will be discussed further. The biology of cancer is undoubtedly more complex than duality, but thinking of cancer as a duality may help scientists and oncologists discover optimal treatments that can be given either simultaneously or sequentially.

Activation of tumor suppressor LKB1 by honokiol abrogates cancer stem-like phenotype in breast cancer via inhibition of oncogenic Stat3

Tumor suppressor and upstream master kinase Liver kinase B1 (LKB1) plays a significant role in suppressing cancer growth and metastatic progression. We show that low-LKB1 expression significantly correlates with poor survival outcome in breast cancer. In line with this observation, loss-of-LKB1 rendered breast cancer cells highly migratory and invasive, attaining cancer stem cell-like phenotype. Accordingly, LKB1-null breast cancer cells exhibited an increased ability to form mammospheres and elevated expression of pluripotency-factors (Oct4, Nanog and Sox2), properties also observed in spontaneous tumors in Lkb1^-/- mice. Conversely, LKB1-overexpression in LKB1-null cells abrogated invasion, migration and mammosphere-formation. Honokiol (HNK), a bioactive molecule from Magnolia grandiflora increased LKB1 expression, inhibited individual cell-motility and abrogated the stem-like phenotype of breast cancer cells by reducing the formation of mammosphere, expression of pluripotency-factors and aldehyde dehydrogenase activity. LKB1, and its substrate, AMP-dependent protein kinase (AMPK) are important for HNK-mediated inhibition of pluripotency factors since LKB1-silencing and AMPK-inhibition abrogated, while LKB1-overexpression and AMPK-activation potentiated HNK's effects. Mechanistic studies showed that HNK inhibited Stat3-phosphorylation/activation in an LKB1-dependent manner, preventing its recruitment to canonical binding-sites in the promoters of Nanog, Oct4 and Sox2. Thus, inhibition of the coactivation-function of Stat3 resulted in suppression of expression of pluripotency factors. Further, we showed that HNK inhibited breast tumorigenesis in mice in an LKB1-dependent manner. Molecular analyses of HNK-treated xenografts corroborated our in vitro mechanistic findings. Collectively, these results present the first in vitro and in vivo evidence to support crosstalk between LKB1, Stat3 and pluripotency factors in breast cancer and effective anticancer modulation of this axis with HNK treatment.

Disruption of mitochondrial electron transport chain function potentiates the pro-apoptotic effects of MAPK inhibition

The mitochondrial network is a major site of ATP production through the coupled integration of the electron transport chain (ETC) with oxidative phosphorylation. In melanoma arising from the V600E mutation in the kinase v-RAF murine sarcoma viral oncogene homolog B (BRAF^V600E), oncogenic signaling enhances glucose-dependent metabolism while reducing mitochondrial ATP production. Likewise, when BRAF^V600E is pharmacologically inhibited by targeted therapies (e.g. PLX-4032/vemurafenib), glucose metabolism is reduced, and cells increase mitochondrial ATP production to sustain survival. Therefore, collateral inhibition of oncogenic signaling and mitochondrial respiration may help enhance the therapeutic benefit of targeted therapies. Honokiol (HKL) is a well tolerated small molecule that disrupts mitochondrial function; however, its underlying mechanisms and potential utility with targeted anticancer therapies remain unknown. Using wild-type BRAF and BRAF^V600E melanoma model systems, we demonstrate here that HKL administration rapidly reduces mitochondrial respiration by broadly inhibiting ETC complexes I, II, and V, resulting in decreased ATP levels. The subsequent energetic crisis induced two cellular responses involving cyclin-dependent kinases (CDKs). First, loss of CDK1-mediated phosphorylation of the mitochondrial division GTPase dynamin-related protein 1 promoted mitochondrial fusion, thus coupling mitochondrial energetic status and morphology. Second, HKL decreased CDK2 activity, leading to G₁ cell cycle arrest. Importantly, although pharmacological inhibition of oncogenic MAPK signaling increased ETC activity, co-treatment with HKL ablated this response and vastly enhanced the rate of apoptosis. Collectively, these findings integrate HKL action with mitochondrial respiration and shape and substantiate a pro-survival role of mitochondrial function in melanoma cells after oncogenic MAPK inhibition.

HMG-CoA synthase 1 is a synthetic lethal partner of BRAFV600E in human cancers

Contributions of metabolic changes to cancer development and maintenance have received increasing attention in recent years. Although many human cancers share similar metabolic alterations, it remains unclear whether oncogene-specific metabolic alterations are required for tumor development. Using an RNAi-based screen targeting the majority of the known metabolic proteins, we recently found that oncogenic BRAF^V600E up-regulates HMG-CoA lyase (HMGCL), which converts HMG-CoA to acetyl-CoA and a ketone body, acetoacetate, that selectively enhances BRAF^V600E-dependent MEK1 activation in human cancer. Here, we identified HMG-CoA synthase 1 (HMGCS1), the upstream ketogenic enzyme of HMGCL, as an additional "synthetic lethal" partner of BRAF^V600E Although HMGCS1 expression did not correlate with BRAF^V600E mutation in human melanoma cells, HMGCS1 was selectively important for proliferation of BRAF^V600E-positive melanoma and colon cancer cells but not control cells harboring active N/KRAS mutants, and stable knockdown of HMGCS1 only attenuated colony formation and tumor growth potential of BRAF^V600E melanoma cells. Moreover, cytosolic HMGCS1 that co-localized with HMGCL and BRAF^V600E was more important than the mitochondrial HMGCS2 isoform in BRAF^V600E-expressing cancer cells in terms of acetoacetate production. Interestingly, HMGCL knockdown did not affect HMGCS1 expression levels, whereas HMGCS1 knockdown caused a compensating increase in HMGCL protein level because of attenuated protein degradation. However, this increase did not reverse the reduced ketogenesis in HMGCS1 knockdown cells. Mechanistically, HMGCS1 inhibition decreased intracellular acetoacetate levels, leading to reduced BRAF^V600E-MEK1 binding and consequent MEK1 activation. We conclude that the ketogenic HMGCS1-HMGCL-acetoacetate axis may represent a promising therapeutic target for managing BRAF^V600E-positive human cancers.

Prevention of Dietary-Fat-Fueled Ketogenesis Attenuates BRAF V600E Tumor Growth

Lifestyle factors, including diet, play an important role in the survival of cancer patients. However, the molecular mechanisms underlying pathogenic links between diet and particular oncogenic mutations in human cancers remain unclear. We recently reported that the ketone body acetoacetate selectively enhances BRAF V600E mutant-dependent MEK1 activation in human cancers. Here we show that a high-fat ketogenic diet increased serum levels of acetoacetate, leading to enhanced tumor growth potential of BRAF V600E-expressing human melanoma cells in xenograft mice. Treatment with hypolipidemic agents to lower circulating acetoacetate levels or an inhibitory homolog of acetoacetate, dehydroacetic acid, to antagonize acetoacetate-BRAF V600E binding attenuated BRAF V600E tumor growth. These findings reveal a signaling basis underlying a pathogenic role of dietary fat in BRAF V600E-expressing melanoma, providing insights into the design of conceptualized "precision diets" that may prevent or delay tumor progression based on an individual's specific oncogenic mutation profile.

Treatment of extensive erythema multiforme with topical gentian violet

Topical and systemic therapies for erythema multiforme have been widely described in the literature. The pathogenesis of erythema multiforme involves increased expression of vascular endothelial growth factor resulting in the promotion of microvascular permeability and angiogenesis. Gentian violet has been shown to have antiangiogenic properties. Here, we present a case of erythema multiforme successfully treated with topical gentian violet. We report the case of a patient who presented with erythema multiforme. Prior pertinent history included diabetes mellitus type I, limiting the clinical use of systemic corticosteroids. Topical gentian violet was used to treat the cutaneous lesions. Our patient responded well to treatment with topical gentian violet with stabilization and resolution of the lesions without using systemic therapy that may pose serious side effects in the setting of other comorbidities such as diabetes mellitus type I. This case highlights the variable therapeutic options available for treatment of erythema multiforme, including topical gentian violet. While further studies are needed, this case demonstrates the antiangiogenic properties and clinical utility of topical gentian violet in the treatment of erythema multiforme.

Double Jeopardy: The Rubber Ball Bounces Twice

Soblet et al. describe cis mutations in TEK/Tie-2 in blue rubber bleb nevus and sporadic vascular malformations. This suggests that the remaining normal allele is required for the phenotype. Second, it suggests therapeutic approaches to treatment signal transduction inhibition.

High-Level Expression of Vascular Endothelial Growth Factor and its Receptors in an Aphthous Ulcer

Background:

Aphthous ulcers are an extremely common disorder of unknown etiology. These ulcers cause significant morbidity through pain and interference with eating. Thalidomide, an angiogenesis inhibitor, is efficacious for the treatment of aphthous ulcers.

Methods:

In situ hybridization was performed on an idiopathic aphthous ulcer using probes specific for the angiogenesis factor vascular endothelial growth factor, and its receptors, in order to determine whether these ulcers are highly angiogenic.

Conclusions:

Aphthous ulcers are highly angiogenic. Thalidomide may act to heal aphthous ulcers by inhibiting angiogenesis and promoting reepithelialization. Excess angiogenesis may inhibit reepithelialization in certain types of ulcers, and angiogenesis inhibitors may actually promote wound healing if ulcers are caused by excess angiogenesis.

Use of Polyphenolic Compounds in Dermatologic Oncology

Polyphenols are a widely used class of compounds in dermatology. While phenol itself, the most basic member of the phenol family, is chemically synthesized, most polyphenolic compounds are found in plants and form part of their defense mechanism against decomposition. Polyphenolic compounds, which include phenolic acids, flavonoids, stilbenes, and lignans, play an integral role in preventing the attack on plants by bacteria and fungi, as well as serving as cross-links in plant polymers. There is also mounting evidence that polyphenolic compounds play an important role in human health as well. One of the most important benefits, which puts them in the spotlight of current studies, is their antitumor profile. Some of these polyphenolic compounds have already presented promising results in either in vitro or in vivo studies for non-melanoma skin cancer and melanoma. These compounds act on several biomolecular pathways including cell division cycle arrest, autophagy, and apoptosis. Indeed, such natural compounds may be of potential for both preventive and therapeutic fields of cancer. This review evaluates the existing scientific literature in order to provide support for new research opportunities using polyphenolic compounds in oncodermatology.

Pro-Apoptotic Activity of New Honokiol/Triphenylmethane Analogues in B-Cell Lymphoid Malignancies

Honokiol and triphenylmethanes are small molecules with anti-tumor properties. Recently, we synthesized new honokiol analogues (HAs) that possess common features of both groups. We assessed the anti-tumor effectiveness of HAs in B-cell leukemia/lymphoma cells, namely in chronic lymphocytic leukemia (CLL) cells ex vivo and in pre-B-cell acute lymphoblastic leukemia (Nalm-6), Burkitt lymphoma (BL; Raji), diffuse large B-cell lymphoma (DLBCL; Toledo) and multiple myeloma (MM; RPMI 8226) cell lines. Four of these compounds appeared to be significantly active against the majority of cells examined, with no significant impact on healthy lymphocytes. These active HAs induced caspase-dependent apoptosis, causing significant deregulation of several apoptosis-regulating proteins. Overall, these compounds downregulated Bcl-2 and XIAP and upregulated Bax, Bak and survivin proteins. In conclusion, some of the HAs are potent tumor-selective inducers of apoptosis in ex vivo CLL and in BL, DLBCL and MM cells in vitro. Further preclinical studies of these agents are recommended.

Down-Regulation of SOX2 Underlies the Inhibitory Effects of the Triphenylmethane Gentian Violet on Melanoma Cell Self-Renewal and Survival

Human melanomas contain a population of tumor-initiating cells that are able to maintain the growth of the tumor. We previously showed that the embryonic transcription factor SOX2 is essential for self-renewal and tumorigenicity of human melanoma-initiating cells. However, targeting a transcription factor is still challenging. Gentian violet (GV) is a cationic triphenylmethane dye with potent antifungal and antibacterial activity. Recently, a combination therapy of imiquimod and GV has shown an inhibitory effect against melanoma metastases. Whether and how GV affects melanoma cells remains unknown. Here we show that GV represses melanoma stem cell self-renewal through inhibition of SOX2. Mechanistically, GV hinders EGFR activation and inhibits the signal transducer and activator of transcription-3 [(STAT3)/SOX2] axis. Importantly, we show that GV treatment decreases STAT3 phosphorylation at residue tyrosine 705, thus preventing the translocation of STAT3 into the nucleus and its binding to SOX2 promoter. In addition, GV affects melanoma cell growth by promoting mitochondrial apoptosis and G2 cell cycle arrest. This study shows that in melanoma, GV affects both the stem cell and the tumor bulk compartments, suggesting the potential use of GV in treating human melanoma alone or in combination with targeted therapy and/or immunotherapy.

Effective local anesthesia for onabotulinumtoxin A injections to treat hyperhidrosis associated with traumatic amputation

BACKGROUND

Botulinum toxin type A (BTX-A) injections are an effective treatment for controlling hyperhidrosis at sites of amputation. Hyperesthesia associated with amputated limbs is a major barrier to performing this procedure under local anesthesia.

OBJECTIVE

To present a novel method for improving local anesthesia with BTX-A injections. Methods &

RESULTS

A 29-year-old military veteran with a below-the-knee amputation of his right leg was suffering from amputation site hyperhidrosis, which was impeding his ability to comfortably wear a prosthesis. Prior to presenting to our clinic, the patient received one treatment of BTX-A injections to his amputation stump while under general anesthesia for surgical repair of trauma-related injuries. In our dermatology clinic, we repeated the procedure using topical lidocaine-prilocaine (30 gm total) for local anesthesia. This provided effective relief of hyperhidrosis for 6 months, but the procedure was very painful (9/10 intensity). We repeated the same procedure 6 months later, using ice in addition to topical lidocaine-prilocaine (30 gm) for local anesthesia; this resulted in reduced pain (3/10 intensity) for the patient.

CONCLUSIONS

We suggest using ice in combination with a topical anesthetic as an effective method for pain control that avoids general anesthesia in treating amputation-associated hyperhidrosis.

Tris (dibenzylideneacetone) dipalladium: a small-molecule palladium complex is effective in inducing apoptosis in chronic lymphocytic leukemia B-cells

Here we tested impact of Tris (dibenzylideneacetone) dipalladium (Tris-DBA) on chronic lymphocytic leukemia (CLL) B-cell survival. Indeed, treatment of CLL B-cells with Tris-DBA induced apoptosis in a dose-dependent manner irrespective of IgVH mutational status. Further analyses suggest that Tris-DBA-induced apoptosis involves reduced expression of the anti-apoptotic proteins Bcl-xL, and XIAP with an upregulation of the pro-apoptotic protein BIM in CLL B-cells. Our findings also indicate that Tris-DBA targets the ribosomal protein (rp)-S6, an essential component of the Akt/mTOR signaling axis in CLL B-cells. Of interest, CLL bone marrow stromal cells were unable to protect the leukemic B cells from Tris-DBA-induced apoptosis in an in vitro co-culture system. Finally, co-administration of Tris-DBA and the purine nucleoside analog fludarabine (F-ara-A) augmented CLL B-cell apoptosis levels in vitro showing synergistic effects. In total, Tris-DBA is effective at inducing apoptosis in CLL B-cells even in the presence of stromal cells likely by targeting directly the signal mediator, rpS6.

Inhibition of FoxM1-Mediated DNA Repair by Imipramine Blue Suppresses Breast Cancer Growth and Metastasis

PURPOSE

The approaches aimed at inhibiting the ability of cancer cells to repair DNA strand breaks have emerged as promising targets for treating cancers. Here, we assessed the potential of imipramine blue (IB), a novel analogue of antidepressant imipramine, to suppress breast cancer growth and metastasis by inhibiting the ability of breast cancer cells to repair DNA strand breaks by homologous recombination (HR).

EXPERIMENTAL DESIGN

The effect of IB on breast cancer growth and metastasis was assessed in vitro as well as in preclinical mouse models. Besides, the therapeutic efficacy and safety of IB was determined in ex vivo explants from breast cancer patients. The mechanism of action of IB was evaluated by performing gene-expression, drug-protein interaction, cell-cycle, and DNA repair studies.

RESULTS

We show that the systemic delivery of IB using nanoparticle-based delivery approach suppressed breast cancer growth and metastasis without inducing toxicity in preclinical mouse models. Using ex vivo explants from breast cancer patients, we demonstrated that IB inhibited breast cancer growth without affecting normal mammary epithelial cells. Furthermore, our mechanistic studies revealed that IB may interact and inhibit the activity of proto-oncogene FoxM1 and associated signaling that play critical roles in HR-mediated DNA repair.

CONCLUSIONS

These findings highlight the potential of IB to be applied as a safe regimen for treating breast cancer patients. Given that FoxM1 is an established therapeutic target for several cancers, the identification of a compound that inhibits FoxM1- and FoxM1-mediated DNA repair has immense translational potential for treating many aggressive cancers. Clin Cancer Res; 22(14); 3524-36. ©2016 AACR.

Abstract P4-07-06: Imipramine Blue - A safe and potent therapeutic regimen that suppresses breast cancer growth and progression by targeting DNA damage surveillance pathway

Despite improvement in overall survival of breast cancer patients, many women don't survive this disease. Moreover, the quality of life for patients who do survive is often substantially reduced due to the toxicity associated with the chemotherapy. Here, we report that imipramine blue (IB), a novel analogue of anti-depressant imipramine that we recently synthesized, may serve as a safe and potent therapeutic agent for treating breast cancers. We show that IB reduced cell growth, migration and invasion of breast cancer cells. Systemic delivery of IB using nanoparticle-based drug delivery approach suppressed breast cancer growth and metastasis without inducing any toxicity in pre-clinical orthotropic mouse models. Notably, using ex-vivo model of tumor explants from breast cancer patients, we demonstrated that IB inhibited breast cancer growth without affecting normal mammary epithelial cell proliferation. Furthermore, IB improved the sensitivity of breast cancer cells to chemotherapy drugs paclitaxel and doxorubicin. Our results revealed that IB mediated its anti-tumor effect by targeting genes involved in cell cycle progression, microtubule dynamics and DNA damage surveillance pathway including Forkhead Box M1 (FOXM1), stathmin1, S-phase kinase-associated protein 2 (Skp2) and XRCC3, which we show to be highly expressed in breast cancer patients. Importantly, we demonstrated that IB inhibited breast cancer cell's ability to repair DNA strand breaks by impairing homologous recombination events. These findings highlight the potential of IB to be used as a potent therapeutic regimen for treating breast cancer patients. Since IB-1 is derived from a FDA approved drug it has potential to be rapidly translated to the clinic.

Citation Format: Rajamanickam S, Subbarayalu P, Timilsina S, Gorthi A, Drake MT, Chen Y, Vadlamudi R, Bishop AJR, Arbiser JL, Rao MK. Imipramine Blue - A safe and potent therapeutic regimen that suppresses breast cancer growth and progression by targeting DNA damage surveillance pathway. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-07-06.

The novel Aryl hydrocarbon receptor inhibitor biseugenol inhibits gastric tumor growth and peritoneal dissemination

Biseugenol (Eug) is known to antiproliferative of cancer cells; however, to date, the antiperitoneal dissemination effects have not been studied in any mouse cancer model. In this study, Aryl hydrocarbon receptor (AhR) expression was associated with lymph node and distant metastasis in patients with gastric cancer and was correlated with clinicolpathological pattern. We evaluated the antiperitoneal dissemination potential of knockdown AhR and Biseugenol in cancer mouse model and assessed mesenchymal characteristics. Our results demonstrate that tumor growth, peritoneal dissemination and peritoneum or organ metastasis implanted MKN45 cells were significantly decreased in shAhR and Biseugenol-treated mice and that endoplasmic reticulum (ER) stress was caused. Biseugenol-exposure tumors showed acquired epithelial features such as phosphorylation of E-cadherin, cytokeratin-18 and loss mesenchymal signature Snail, but not vimentin regulation. Snail expression, through AhR activation, is an epithelial-to-mesenchymal transition (EMT) determinant. Moreover, Biseugenol enhanced Calpain-10 (Calp-10) and AhR interaction resulted in Snail downregulation. The effect of shCalpain-10 in cancer cells was associated with inactivation of AhR/Snail promoter binding activity. Inhibition of Calpain-10 in gastric cancer cells by short hairpin RNA or pharmacological inhibitor was found to effectively reduced growth ability and vessel density in vivo. Importantly, knockdown of AhR completed abrogated peritoneal dissemination. Herein, Biseugenol targeting ER stress provokes Calpain-10 activity, sequentially induces reversal of EMT and apoptosis via AhR may involve the paralleling processes. Taken together, these data suggest that Calpain-10 activation and AhR inhibition by Biseugenol impedes both gastric tumor growth and peritoneal dissemination by inducing ER stress and inhibiting EMT.

Abstract 1787: Imipramine blue: a novel NOX inhibitor as potent therapeutic agent to treat triple-negative breast cancers

Breast cancer is the most common cancer in women and the second leading cause of cancer death in US. Triple-negative breast cancers (TNBC) are the most aggressive forms of breast cancer. Almost 60% of patients with TNBCs develop chemo-resistance, leading to early relapse and shorter survival. The family of NADPH oxidases (NOX) enzymes is more abundant source of reactive oxygen species, which generally over expressed in a wide range of cancers including breast cancer. Over expression of NOX family of proteins in the tumor cells and stroma results in the activation of several intracellular pathways that promotes neoplastic transformation. Moreover, NOX is an important metabolic enzyme that plays a critical role in supporting increased glycolysis in cancer cells by generating NAD+, a substrate for one of the key glycolytic reactions. The constitutive upregulation of glycolysis is thought to confer significant growth advantage to cancer cells leading to uncontrolled proliferation and increased invasion. This is especially true for TNBC that shows a strong association with the Warburg effect. Herein we evaluated first time the role of imipramine blue (IB), a NOX inhibitor and a derivative of the FDA approved antidepressant imipramine in TNBC cells growth and progression. Our results demonstrated that imipramine blue inhibits TNBC, MDA-MB-231, MDA-MB-468 and Bt-549 cells growth without affecting normal mammary epithelial (MCF-10A) cells. Notably, our studies revealed that imipramine blue targets multiple NOX family members, which are highly expressed in breast tumors when compared to adjacent normal tissue. Imipramine blue treatment also reduced migration and invasion and inhibited the self-renewal capability of MDA-MB-231 cells. Importantly, imipramine blue treatment significantly reduced experimental lung metastasis of MDA-MB-231 cells in athymic nude mice without induce apparent toxicity. Our gene microarray results further showed that IB treatment significantly altered an array of genes, including FOXM1, Aurora kinase A (AURAK) and Polo-like kinase 1 (PLK1), which play important roles in cancer growth and progression as well as in mediating sensitivity/resistance of paclitaxel (PTX), a chemotherapy drug that is routinely used as a first line treatment for breast cancer patients. Taken together, our findings propose NOX inhibitor imipramine blue as a novel therapeutic agent with less toxicity to treat triple negative breast cancers.

Citation Format: Subapriya Rajamanickam, Panneerdoss Subbarayalu, Santhosh Timilsina, Michael T. Drake, Zhenze Zhao, Hung I Harry Chen, Yidong Chen, Jack L. Arbiser, Manjeet K K. Rao. Imipramine blue: a novel NOX inhibitor as potent therapeutic agent to treat triple-negative breast cancers. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1787. doi:10.1158/1538-7445.AM2015-1787

Honokiol abrogates leptin-induced tumor progression by inhibiting Wnt1-MTA1-β-catenin signaling axis in a microRNA-34a dependent manner

Obesity greatly influences risk, progression and prognosis of breast cancer. As molecular effects of obesity are largely mediated by adipocytokine leptin, finding effective novel strategies to antagonize neoplastic effects of leptin is desirable to disrupt obesity-cancer axis. Present study is designed to test the efficacy of honokiol (HNK), a bioactive polyphenol from Magnolia grandiflora, against oncogenic actions of leptin and systematically elucidate the underlying mechanisms. Our results show that HNK significantly inhibits leptin-induced breast-cancer cell-growth, invasion, migration and leptin-induced breast-tumor-xenograft growth. Using a phospho-kinase screening array, we discover that HNK inhibits phosphorylation and activation of key molecules of leptin-signaling-network. Specifically, HNK inhibits leptin-induced Wnt1-MTA1-β-catenin signaling in vitro and in vivo. Finally, an integral role of miR-34a in HNK-mediated inhibition of Wnt1-MTA1-β-catenin axis was discovered. HNK inhibits Stat3 phosphorylation, abrogates its recruitment to miR-34a promoter and this release of repressor-Stat3 results in miR-34a activation leading to Wnt1-MTA1-β-catenin inhibition. Accordingly, HNK treatment inhibited breast tumor growth in diet-induced-obese mouse model (exhibiting high leptin levels) in a manner associated with activation of miR-34a and inhibition of MTA1-β-catenin. These data provide first in vitro and in vivo evidence for the leptin-antagonist potential of HNK revealing a crosstalk between HNK and miR34a and Wnt1-MTA1-β-catenin axis.

Solenopsin A and analogs exhibit ceramide-like biological activity

BACKGROUND

(-)-Solenopsin A is a piperidine alkaloid that is a component of the venom of the fire ant Solenopsis invicta. Previously, we have demonstrated that solenopsin exhibit anti-angiogenic activity and downregulate phosphoinositol-3 kinase (PI3K) in the p53 deficient renal cell carcinoma cell line 786-O. Solenopsin has structural similarities to ceramide, a major endogenous regulator of cell signaling and cancer therapy induced apoptosis.

METHODS

Different analogs of solenopsin were synthesized in order to explore structure-activity relationships. The anti-proliferative effect of solenopsin and analogs was tested on six different cell lines, including three tumor cell lines, two normal cutaneous cell lines, and one immortalized hyperproliferative cell line. FRET-based reporters were used to study the affect of solenopsin and analogs on Akt activity and PDK1 activation and sucrose density gradient fractionation was performed to examine recruitment of PTEN to membrane rafts. Western-blotting was used to evaluate the affect of solenopsin and analogs on the Akt and the MAPK 44/42 pathways in three different tumor cell lines. Measurement of cellular oxygen consumption rate together with autophagy staining was performed to study mitochondrial function. Finally, the affect of solenopsin and analogs on ROS production was investigated.

RESULTS

In this paper we demonstrate that solenopsin analogs with potent anti-proliferative effects can be synthesized from inexpensive dimethylpyridines. To determine whether solenopsin and analogs act as ceramide analogs, we examined the effect of solenopsin and analogs on two stereotypic sites of ceramide activity, namely at lipid rafts and mitochondria. We found that native solenopsin, (-)-solenopsin A, inhibits functional Akt activity and PDK1 activation in lipid rafts in a similar fashion as ceramide. Both cis and trans analogs of solenopsin reduce mitochondrial oxygen consumption, increase reactive oxygen, and kill tumor cells with elevated levels of Akt phosphorylation. However, only solenopsin induces mitophagy, like ceramide.

CONCLUSIONS

The requirements for ceramide induced mitophagy and inhibition of Akt activity and PDK1 activation in lipid rafts are under strict stereochemical control. The naturally occurring (-)-solenopsin A mimic some of the functions of ceramide and may be therapeutically useful in the treatment of hyperproliferative and malignant disorders of the skin, even in the presence of elevated levels of Akt.

Suppression of NF-κB activation by gentian violet promotes osteoblastogenesis and suppresses osteoclastogenesis

Skeletal mass is regulated by the coordinated action of bone forming osteoblasts and bone resorbing osteoclasts. Accelerated rates of bone resorption relative to bone formation lead to net bone loss and the development of osteoporosis, a devastating disease that predisposes the skeleton to fractures. Bone fractures are associated with significant morbidity and in the case of hip fractures, high mortality. Gentian violet (GV), a cationic triphenylmethane dye, has long been used as an antifungal and antibacterial agent and is presently under investigation as a potential chemotherapeutic and antiangiogenic agent. However, effects on bone cells have not been previously reported and the mechanisms of action of GV, are poorly understood. In this study we show that GV suppresses receptor activator of NF-κB ligand (RANKL)-induced differentiation of RAW264.7 osteoclast precursors into mature osteoclasts, but paradoxically stimulates the differentiation of MC3T3 cells into mineralizing osteoblasts. These actions stem from the capacity of GV to suppress activation of the nuclear factor kappa B (NF-κB) signal transduction pathway that is required for osteoclastogenesis, but inhibitory to osteoblast differentiation and activity. Our data reveal that GV is an inhibitor of NF-κB activation and may hold promise for modulation of bone turnover to promote a balance between bone formation and bone resorption, favorable to gain of bone mass.

Inactivation of NADPH oxidases NOX4 and NOX5 protects human primary fibroblasts from ionizing radiation-induced DNA damage

Human exposure to ionizing radiation from medical procedures has increased sharply in the last three decades. Recent epidemiological studies suggest a direct relationship between exposure to ionizing radiation and health problems, including cancer incidence. Therefore, minimizing the impact of radiation exposure in patients has become a priority in the development of future clinical practices. Crucial players in radiation-induced DNA damage include reactive oxygen species (ROS), but the sources of these have remained elusive. To the best of our knowledge, we show here for the first time that two members of the ROS-generating NADPH oxidase family (NOXs), NOX4 and NOX5, are involved in radiation-induced DNA damage. Depleting these two NOXs in human primary fibroblasts resulted in reduced levels of DNA damage as measured by levels of radiation-induced foci, a marker of DNA double-strand breaks (DSBs) and the comet assay coupled with increased cell survival. NOX involvement was substantiated with fulvene-5, a NOXs-specific inhibitor. Moreover, fulvene-5 mitigated radiation-induced DNA damage in human peripheral blood mononuclear cells ex vivo. Our results provide evidence that the inactivation of NOXs protects cells from radiation-induced DNA damage and cell death. These findings suggest that NOXs inhibition may be considered as a future pharmacological target to help minimize the negative effects of radiation exposure for millions of patients each year.

Abstract LB-61: Inhibiting “Dedifferentiation” in breast cancer cells using Honokiol - a plant derived polyphenol

Introduction: Dedifferentiation involves terminally differentiated cells reverting back to less differentiated cells such as precursor cells or stem cells within their own lineage allowing the cells to proliferate again before re-differentiation. Tumorigenesis involves uncontrolled cell proliferation and many host-related factors aid in dedifferentiation of tumor cells into stem cell like phenotypes hence providing a mechanism leading to tumor heterogeneity and aggressiveness. Pluripotency factors Oct4, Nanog and Sox2 have been implicated in dedifferentiation and are highly expressed in tumors. The importance of active constitutive agents in natural products has become increasingly apparent owing to their potential cancer chemopreventive and therapeutic properties. Honokiol (HNK) is a natural phenolic compound isolated from an extract of seed cones from Magnolia grandiflora. Recent studies from our laboratory demonstrated that HNK has suppressing effects on different aspects of cancer progression. The present study was designed to specifically examine the potential of HNK to inhibit pluripotency related transcription factors and reverse the process of dedifferentiation associated with uncontrolled cell proliferation in tumorigenesis.

Results: Here, we provide evidence that HNK inhibits the ability of breast cancer cells to form mammospheres. HNK treatment inhibits dedifferentiation/pluripotency markers Oct4, Nanog, Sox2 in MCF-7, MDA-MB-231, T47D, MDA-MB-468 breast cancer cells. An analysis of underlying signaling mechanism reveal that HNK inhibits phosphorylation of Stat3 and the downregulation of pluripotency factors is mediated via inhibition of Stat3. Stat3 inhibitor, Stattic potentiates the effect of HNK while overexpression of constitutively active Stat3 interferes with HNK-mediated inhibition of Oct4, Nanog and Sox2. It is interesting to note that HNK treatment also increases the expression of upstream kinase and tumor suppressor LKB1. Utilizing LKB1-null cells and gain-of-function strategies, we show that HNK-mediated inhibition of Oct4, Nanog and Sox2 is regulated by tumor suppressor LKB1. The ability of HNK to inhibit mammosphere formation is abrograted in breast cancer cells stably-silenced for LKB1. In vitro and in vivo analyses show novel functional interactions between HNK, Stat3, LKB1 and dedifferentiation/pluripotency markers.

Conclusions: Taken together, these studies provide evidence for a previously unrecognized cross-talk between HNK and dedifferentiation/pluripotency markers Oct4, Nanog, Sox2 via tumor suppressor LKB1-Stat3 axis in inhibiting “dedifferentiation” in breast cancer.

Citation Format: Sonali Sengupta, Michael Y. Bonner, Jack L. Arbiser, Neeraj K. Saxena, Dipali Sharma. Inhibiting “Dedifferentiation” in breast cancer cells using Honokiol - a plant derived polyphenol. [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 LB-61. doi:10.1158/1538-7445.AM2014-LB-61

Abstract LB-187: Novel mechanistic insights into the bioactive compound honokiol-mediated inhibition of epithelial to mesenchymal transition in breast cancer: Therapeutic modulation of miR-34a via tumor suppressor LKB1

Introduction: An emerging hypothesis is that epithelial-mesenchymal-transition (EMT) bestows metastatic potential to epithelial cancer cells enabling them to invade, migrate and subsequently disseminate to form distant metastases resulting in non-curable disease. Pharmacological inhibition of EMT can potentially lead to reversion of aggressive breast cancer cells to a more-differentiated epithelial phenotype by inducing mesenchymal-epithelial transition (MET) to prevent metastasis and diminish distant recurrence. The importance of active constitutive agents in natural products has become increasingly apparent owing to their potential cancer chemopreventive and therapeutic properties. Honokiol (HNK) is a natural phenolic compound isolated from an extract of seed cones from Magnolia grandiflora. Recent studies from our lab demonstrated that HNK has suppressing effects on different aspects of cancer progression. The present study was designed to specifically examine the potential of HNK to inhibit EMT and elucidate the molecular mechanism by which HNK inhibits EMT in breast cancer cells.

Aim: To elucidate the mechanism by which HNK inhibits EMT in breast cancer cells.

Results: Here, we provide molecular evidence that HNK inhibits EMT in breast cancer cells resulting in significant downregulation of mesenchymal marker proteins and concurrent upregulation of epithelial markers. In vitro and in vivo analyses show functional interactions between HNK, STAT3, and EMT-signaling components. Mechanistically, HNK inhibits recruitment of STAT3 on mesenchymal transcription factor ZEB1 promoter resulting in decreased ZEB1 expression and nuclear translocation. We also discover that HNK increases E-cadherin expression via STAT3-mediated release of ZEB1 from E-cadherin promoter. Since ZEB1 is a transcriptional repressor of miR-34a, we next examined the effect of HNK on miR-34a expression. Intriguingly, we found that HNK upregulates the levels of miR-34a in a time- and dose-dependent manner. It is interesting to note that HNK treatment also increases the expression of upstream kinase and tumor suppressor LKB1. Utilizing LKB1-null cells and gain-of-function strategies, we found that HNK-mediated increase in miR-34a is regulated by tumor suppressor LKB1.

Conclusions: Taken together, these studies provide evidence for a previously unrecognized cross-talk between HNK and miR-34a via tumor suppressor LKB1 in inhibiting EMT in breast cancer.

Citation Format: Dimiter B. Avtanski, Michael Y. Bonner, Timothy P. Tiutan, Jack L. Arbiser, Neeraj K. Saxena, Dipali Sharma. Novel mechanistic insights into the bioactive compound honokiol-mediated inhibition of epithelial to mesenchymal transition in breast cancer: Therapeutic modulation of miR-34a via tumor suppressor LKB1. [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 LB-187. doi:10.1158/1538-7445.AM2014-LB-187

Honokiol inhibits androgen receptor activity in prostate cancer cells

BACKGROUND

We have shown previously that honokiol (HNK), a bioactive component of the medicinal plant Magnolia officinalis, inhibits growth of human prostate cancer cells in vitro and in vivo. However, the effect of HNK on androgen receptor (AR) signaling has not been studied.

METHODS

LNCaP, C4-2, and TRAMP-C1 cells were used for various assays. Trypan blue dye exclusion assay or clonogenic assay was performed for determination of cell viability. The effects of HNK and/or its analogs on protein levels of AR and its target gene product prostate specific antigen (PSA) were determined by western blotting. RNA interference of p53 was achieved by transient transfection. Reverse transcription-polymerase chain reaction was performed for mRNA expression of AR. Nuclear level of AR was visualized by microscopy. Apoptosis was quantified by DNA fragmentation assay or flow cytometry after Annexin V-propidium iodide staining.

RESULTS

HNK and its dichloroacetate analog (HDCA) were relatively more effective in suppressing cell viability and AR protein level than honokiol epoxide or biseugenol. Nuclear translocation of AR stimulated by a synthetic androgen (R1881) was markedly suppressed in the presence of HNK. Downregulation of AR protein resulting from HNK exposure was attributable to transcriptional repression as well as proteasomal degradation. HNK-mediated suppression of AR protein was maintained in LNCaP cells after knockdown of p53 protein. HNK-induced apoptosis was not affected by R1881 treatment.

CONCLUSIONS

The present study demonstrates, for the first time, that HNK inhibits activity of AR in prostate cancer cells regardless of the p53 status.

Honokiol enhances paclitaxel efficacy in multi-drug resistant human cancer model through the induction of apoptosis

Resistance to chemotherapy remains a major obstacle in cancer therapy. This study aimed to evaluate the molecular mechanism and efficacy of honokiol in inducing apoptosis and enhancing paclitaxel chemotherapy in pre-clinical multi-drug resistant (MDR) cancer models, including lineage-derived human MDR (KB-8-5, KB-C1, KB-V1) and their parental drug sensitive KB-3-1 cancer cell lines. In vitro analyses demonstrated that honokiol effectively inhibited proliferation in KB-3-1 cells and the MDR derivatives (IC₅₀ ranging 3.35±0.13 µg/ml to 2.77±0.22 µg/ml), despite their significant differences in response to paclitaxel (IC₅₀ ranging 1.66±0.09 ng/ml to 6560.9±439.52 ng/ml). Honokiol induced mitochondria-dependent and death receptor-mediated apoptosis in MDR KB cells, which was associated with inhibition of EGFR-STAT3 signaling and downregulation of STAT3 target genes. Combined treatment with honokiol and paclitaxel synergistically augmented cytotoxicity in MDR KB cells, compared with treatment with either agent alone in vitro. Importantly, the combined treatment significantly inhibited in vivo growth of KB-8-5 tumors in a subcutaneous model. Tumor tissues from the combination group displayed a significant inhibition of Ki-67 expression and an increase in TUNEL-positive cells compared with the control group. These results suggest that targeting multidrug resistance using honokiol in combination with chemotherapy drugs may provide novel therapeutic opportunities.

Gentian violet induces wtp53 transactivation in cancer cells

Recent studies suggest that gentian violet (GV) may have anticancer activity by inhibiting for instance NADPH oxidases (Nox genes) whose overexpression is linked to tumor progression. Nox1 overexpression has been shown to inhibit transcriptional activity of the oncosuppressor p53, impairing tumor cell response to anticancer drugs. The tumor suppressor p53 is a transcription factor that, upon cellular stress, is activated to induce target genes involved in tumor cell growth inhibition and apoptosis. Thus, its activation is important for efficient tumor eradication. In this study, we examined the effect of GV on wild-type (wt) p53 activity in cancer cells. We found that GV was able to overcome the inhibitory effect of the NADPH oxidase Nox1 on p53 transcriptional activity. For the first time we show that GV was able to directly induce p53/DNA binding and transcriptional activity. In vitro, GV markedly induced cancer cell death and apoptotic marker PARP cleavage in wtp53-carrying cells. GV-induced cell death was partly inhibited in cells deprived of p53, suggesting that the anticancer activity of GV may partly depend on p53 activation. GV is US Food and Drug Administration approved for human use and may, therefore, have therapeutic potential in the management of cancer through p53 activation.

Honokiol inhibits epithelial-mesenchymal transition in breast cancer cells by targeting signal transducer and activator of transcription 3/Zeb1/E-cadherin axis

Epithelial-mesenchymal transition (EMT), a critical step in the acquisition of metastatic state, is an attractive target for therapeutic interventions directed against tumor metastasis. Honokiol (HNK) is a natural phenolic compound isolated from an extract of seed cones from Magnolia grandiflora. Recent studies from our lab show that HNK impedes breast carcinogenesis. Here, we provide molecular evidence that HNK inhibits EMT in breast cancer cells resulting in significant downregulation of mesenchymal marker proteins and concurrent upregulation of epithelial markers. Experimental EMT induced by exposure to TGFβ and TNFα in spontaneously immortalized nontumorigenic human mammary epithelial cells is also completely reversed by HNK as evidenced by morphological as well as molecular changes. Investigating the downstream mediator(s) that may direct EMT inhibition by HNK, we found functional interactions between HNK, Stat3, and EMT-signaling components. In vitro and in vivo analyses show that HNK inhibits Stat3 activation in breast cancer cells and tumors. Constitutive activation of Stat3 abrogates HNK-mediated activation of epithelial markers whereas inhibition of Stat3 using small molecule inhibitor, Stattic, potentiates HNK-mediated inhibition of EMT markers, invasion and migration of breast cancer cells. Mechanistically, HNK inhibits recruitment of Stat3 on mesenchymal transcription factor Zeb1 promoter resulting in decreased Zeb1 expression and nuclear translocation. We also discover that HNK increases E-cadherin expression via Stat3-mediated release of Zeb1 from E-cadherin promoter. Collectively, this study reports that HNK effectively inhibits EMT in breast cancer cells and provide evidence for a previously unrecognized cross-talk between HNK and Stat3/Zeb1/E-cadherin axis.

Gentian violet: a 19th century drug re-emerges in the 21st century

Gentian violet (GV) has a long and varied history as a medicinal agent. Historically used as an antibacterial and antifungal, recent reports have shown its utility as an antitypranosomal, antiviral and anti-angiogenic agent. The objective of this article is to summarize evidence regarding the efficacy and safety of GV use in dermatology. Recent discoveries have found novel targets of GV, namely NADPH oxidase in mammalian cells and thioredoxin reductase 2 in bacterial, fungal and parasitic cells. These discoveries have expanded the use of GV in the 21st century. Given that GV is well tolerated, effective and inexpensive, its use in dermatology is predicted to increase.

Inducing apoptosis of cancer cells using small-molecule plant compounds that bind to GRP78

Background:

Glucose regulated protein 78 (GRP78) functions as a sensor of endoplasmic reticulum (ER) stress. The aim of this study was to test the hypothesis that molecules that bind to GRP78 induce the unfolded protein response (UPR) and enhance cell death in combination with ER stress inducers.

Methods:

Differential scanning calorimetry (DSC), measurement of cell death by flow cytometry and the induction of ER stress markers using western blotting.

Results:

Epigallocatechin gallate (EGCG), a flavonoid component of Green Tea Camellia sinensis, and honokiol (HNK), a Magnolia grandiflora derivative, bind to unfolded conformations of the GRP78 ATPase domain. Epigallocatechin gallate and HNK induced death in six neuroectodermal tumour cell lines tested. Levels of death to HNK were twice that for EGCG; half-maximal effective doses were similar but EGCG sensitivity varied more widely between cell types. Honokiol induced ER stress and UPR as predicted from its ability to interact with GRP78, but EGCG was less effective. With respect to cell death, HNK had synergistic effects on melanoma and glioblastoma cells with the ER stress inducers fenretinide or bortezomib, but only additive (fenretinide) or inhibitory (bortezomib) effects on neuroblastoma cells.

Conclusion:

Honokiol induces apoptosis due to ER stress from an interaction with GRP78. The data are consistent with DSC results that suggest that HNK binds to GRP78 more effectively than EGCG. Therefore, HNK may warrant development as an antitumour drug.

The natural product honokiol inhibits calcineurin inhibitor-induced and Ras-mediated tumor promoting pathways

Although calcineurin inhibitors (CNIs) are very useful in preventing allograft rejection, they can mediate a rapid progression of post-transplantation malignancies. The CNI cyclosporine A (CsA) can promote renal tumor growth through activation of the proto-oncogene ras and over-expression of the angiogenic cytokine VEGF; the ras activation also induces over-expression of the cytoprotective enzyme HO-1, which promotes survival of renal cancer cells. Here, we show that the natural product honokiol significantly inhibited CsA-induced and Ras-mediated survival of renal cancer cells through the down-regulations of VEGF and HO-1. Thus, honokiol treatment may help to prevent tumor-promoting effects of CsA in transplant patients.

Anti-invasive adjuvant therapy with imipramine blue enhances chemotherapeutic efficacy against glioma

The invasive nature of glioblastoma (GBM) represents a major clinical challenge contributing to poor outcomes. Invasion of GBM into healthy tissue restricts chemotherapeutic access and complicates surgical resection. Here, we test the hypothesis that an effective anti-invasive agent can "contain" GBM and increase the efficacy of chemotherapy. We report a new anti-invasive small molecule, Imipramine Blue (IB), which inhibits invasion of glioma in vitro when tested against several models. IB inhibits NADPH (reduced form of nicotinamide adenine dinucleotide phosphate) oxidase-mediated reactive oxygen species generation and alters expression of actin regulatory elements. In vivo, liposomal IB (nano-IB) halts invasion of glioma, leading to a more compact tumor in an aggressively invasive RT2 syngeneic astrocytoma rodent model. When nano-IB therapy was followed by liposomal doxorubicin (nano-DXR) chemotherapy, the combination therapy prolonged survival compared to nano-IB or nano-DXR alone. Our data demonstrate that nano-IB-mediated containment of diffuse glioma enhanced the efficacy of nano-DXR chemotherapy, demonstrating the promise of an anti-invasive compound as an adjuvant treatment for glioma.

Targeting the intrinsic inflammatory pathway: honokiol exerts proapoptotic effects through STAT3 inhibition in transformed Barrett's cells

One way to link chronic inflammation with cancer is through the intrinsic inflammatory pathway, in which genetic alterations that induce malignant transformation also produce a cancer-promoting, inflammatory microenvironment. Signal transducer and activator of transcription 3 (STAT3) contributes to the intrinsic inflammatory pathway in Barrett's esophagus. In human tumors, honokiol (a polyphenol in herbal teas) has growth-inhibitory and proapoptotic effects associated with suppressed activation of STAT3. We used human Barrett's epithelial and esophageal adenocarcinoma cell lines to determine effects of honokiol on cell number, necrosis, apoptosis, and anchorage-independent growth and to explore STAT3's role in those effects. We determined Ras activity and expression of phosphorylated ERK1/2, phosphorylated Akt, and phosphorylated STAT3 in the presence or absence of honokiol. Cells were infected with constitutively active Stat3-C to assess effects of honokiol-induced STAT3 inhibition on apoptosis. Honokiol decreased cell number and increased necrosis and apoptosis in transformed Barrett's cells, but not in nontransformed cells. In adenocarcinoma cells, honokiol also increased necrosis and apoptosis and decreased anchorage-independent growth. Within 30 min of honokiol treatment, transformed Barrett's cells decreased expression of phosphorylated STAT3; decreases in Ras activity and phosphorylated ERK1/2 expression were detected at 24 h. Infection with Stat3-C significantly reduced apoptosis after honokiol treatment. Honokiol causes necrosis and apoptosis in transformed Barrett's and esophageal adenocarcinoma cells, but not in nontransformed Barrett's cells, and the proapoptotic effects of honokiol are mediated by its inhibition of STAT3 signaling. These findings suggest a potential role for targeting the intrinsic inflammatory pathways as a therapeutic strategy to prevent Barrett's carcinogenesis.

Cooperative benefit for the combination of rapamycin and imatinib in tuberous sclerosis complex neoplasia

Tuberous sclerosis (TS) is a common autosomal-dominant disorder characterized by tumors of the skin, lung, brain, and kidneys. Monotherapy with rapamycin however resulted in partial regression of tumors, implying the involvement of additional pathways. We have previously implicated platelet-derived growth factor-BB in TS-related tumorigenesis, thus providing a rationale for a combination of mTOR/PDGF blockade using rapamycin and imatinib. Here, we test this combination using a well-established preclinical model of cutaneous tumorigenesis in TS, tsc2ang1 cells derived from a skin tumor from a mouse heterozygous for tsc2. Treatment of tsc2ang1 cells with a combination of rapamycin and imatinib led to an inhibition of proliferation compared with either vehicle treatment or treatment with rapamycin or imatinib monotherapy. Combination therapy also led to a decrease in Akt activation. Potent in vivo activity in animal experiments by combination therapy was noted, without toxicity to the animals. Our findings provide a rationale for the combined use of rapamycin and imatinib, both FDA approved drugs, for the treatment of TS.

Targeting NADPH oxidases for the treatment of cancer and inflammation

NADPH oxidases are a family of oxidases that utilize molecular oxygen to generate hydrogen peroxide and superoxide, thus indicating physiological functions of these highly reactive and short-lived species. The regulation of these NADPH oxidases (nox) enzymes is complex, with many members of this family exhibiting complexity in terms of subunit composition, cellular location, and tissue-specific expression. While the complexity of the nox family (Nox1-5, Duox1, 2) is daunting, the complexity also allows for targeting of NADPH oxidases in disease states. In this review, we discuss which inflammatory and malignant disorders can be targeted by nox inhibitors, as well as clinical experience in the use of such inhibitors.

Abstract 153: Honokiol, a promising small molecular weight natural agent, activates AMP-activated protein kinase in breast cancer cells via LKB1-dependent pathway and inhibits breast carcinogenesis

Introduction: Research over the past few years have established LKB1-AMPK pathway as an important metabolic checkpoint interconnecting the signaling pathways controlling metabolism and cancer cell growth. Thus, it is of major interest to find effective therapeutic strategies to manipulate LKB1-AMPK axis to inhibit cancer growth. The importance of active constitutive agents in natural products has become increasingly apparent owing to their potential cancer preventive as well as therapeutic properties. Honokiol, a small-molecule polyphenol isolated from magnolia species, is widely known for its therapeutic potential as an anti-inflammatory, anti-thrombosis, anti-oxidant agent and more recently for its protective function in carcinogenesis. In the present study, we sought to examine the effectiveness of honokiol in modulating LKB1-AMPK axis, preventing mammary tumorigenesis and inhibiting metastasis. Methods: Clonogenicity, 3D-colony formation, matrigel invasion, scratch-migration and spheroid-migration assays were used to examine breast cancer cell growth and metastatic potential upon honokiol treatment. Western blot and immunofluorescence analysis were used to examine activation of LKB1-AMPK axis. Functional importance of AMPK and LKB1 was examined by using AMPK-null and AMPK-WT immortalized mouse embryonic fibroblasts (MEFs) and isogenic LKB1-knockdown cell line pairs. Breast cancer xenografts, immunohistochemical and western blot analysis of tumors were used. Results: Analysis of the underlying molecular mechanisms revealed that honokiol treatment increases AMP-activated protein kinase (AMPK) phosphorylation and activity as evident by increased phosphorylation of downstream target of AMPK, acetyl-coenzyme A carboxylase (ACC) and inhibition of phosphorylation of p70S6kinase (pS6K) and eukaryotic translation initiation factor 4E binding protein 1 (4EBP1). Using AMPK-null and AMPK-WT (MEFs); we found that AMPK is required for honokiol-mediated modulation of pACC-pS6K. Intriguingly, we discovered that honokiol treatment increased the expression and cytoplasmic translocation of tumor suppressor gene LKB1 in breast cancer cells. LKB1 knockdown inhibited honokiol-mediated activation of AMPK and more importantly, inhibition of migration and invasion of breast cancer cells. Furthermore, honokiol treatment resulted in inhibition of breast tumorigenesis in vivo. Analysis of tumors showed significant increase in the levels of cytoplasmic LKB1 and phospho-AMPK in honokiol-treated tumors. Conclusions: Taken together, these data providing first in vitro and in vivo evidence of the efficacy of honokiol in activating LKB1-AMPK axis resulting in effective inhibition of mammary tumorigenesis and metastasis provide impetus to determine its activity in clinical setting.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 153. doi:1538-7445.AM2012-153

Abstract 1994: Honokiol reduces drug resistance by down-regulation of survivin expression in multidrug resistant squamous cell carcinoma of the head and neck

Background: Resistance to chemotherapy is a major obstacle in cancer therapy. The purpose of this study is to evaluate honokiol in combination with paclitaxel in controlling proliferation of multi-drug resistant (MDR) cancer cells. Honokiol is a small molecule purified from Magnolia officinalis. Honokiol has been shown to suppress tumor growth through apoptosis and inhibition of angiogenesis. In this study, we investigated the effects and mechanisms of those effects of honokiol on MDR squamous cell cancers of the head and neck (SCCHN) Methods: Serial MDR SCCHN lines including KB-8-5, KB-C1, and KB-V1 derived from the drug sensitive parental KB-3-1 cells were used in this study. Cytotoxic effects of honokiol alone and in combination with paclitaxel on apoptosis in drug-sensitive and -resistant cells were evaluated in vitro and in a subcutaneous KB-8-5 xenograft model, Results: The cell growth inhibition analysis revealed a wide range of IC50 values of paclitaxel from 1.66±0.09 to 6560.9 ±439.52 ng/ml in the KB serial cell lines, indicating that those cell lines have different levels of resistance to the paclitaxel treatment. In contrast, honokiol effectively inhibited proliferation and induced apoptosis in all four cell lines with IC50 values from 3.35±0.13 to 2.77±0.22 μg/ml. Mechanistic studies revealed that honokiol induced similar mitochondria-dependent apoptosis in drug resistant cell lines regardless of the differential resistance levels to paclitaxel treatment. Moreover these effects were associated with inhibition of STAT3 phosphorylation and down-regulation of STAT3 target gene expression, including survivin and Mcl-1. Combined treatment with honokiol and paclitaxel synergistically increased cytotoxicity as compared to the single drug treatment. This combination also significantly inhibited growth of xenografted tumors in nude mice. Conclusion: These results suggest that honokiol may be a promising drug in overcoming paclitaxel resistence of SCCHN. Targeting MDR SCCHN using honokiol in combination with paclitaxel, may benefit patients with SCCHN. (Supported by grants P50CA128613, GCC Distinguished Cancer Scholar to Dong M. Shin and Jonathan J Beitler)

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1994. doi:1538-7445.AM2012-1994

Transgrediens pachyonychia congenita (PC): case series of a nonclassical PC presentation

BACKGROUND

Pachyonychia congenita (PC) is a rare keratin disorder that typically presents with nail dystrophy and focal plantar keratoderma. We present seven cases of PC with transgrediens involvement of the dorsal feet.

OBJECTIVES

To document the extension of their disease to the dorsum of the feet in patients with mutation-confirmed PC, to report the natural history of PC with such transgrediens involvement, to generate hypotheses regarding aetiology, and to suggest prevention and treatment modalities.

METHODS

Genetically confirmed cases of PC with transgrediens foot involvement were verified through the International Pachyonychia Congenita Research Registry (IPCRR) and characterized via telephone survey and photography.

RESULTS

Seven patients with PC in the IPCRR were confirmed to have transgrediens lesions on the dorsal feet (six KRT6A mutations; one KRT16 mutation). Six cases had pre-existing nontransgrediens keratoderma and all cases reported standing, wearing shoes, foot moisture, and/or infection as exacerbating or predisposing factors. Improvement, reported in six cases, was attributed to use of antibiotics or gentian violet, or improved footwear.

CONCLUSIONS

Transgrediens involvement of the dorsal feet is a rare manifestation of mutation-confirmed PC and may be more common in patients who carry a KRT6A mutation. Trauma, friction, infection and wound healing may exacerbate or predispose toward transgrediens lesions. It remains to be proven whether transgrediens-associated infection is causal or represents a primary or secondary process. Patients with PC who develop transgrediens lesions may benefit from fungal and bacterial cultures, followed by appropriate antimicrobial treatments. Efforts to decrease skin friction and moisture may also improve and/or prevent transgrediens spread.

Honokiol activates AMP-activated protein kinase in breast cancer cells via an LKB1-dependent pathway and inhibits breast carcinogenesis

INTRODUCTION

Honokiol, a small-molecule polyphenol isolated from magnolia species, is widely known for its therapeutic potential as an antiinflammatory, antithrombosis, and antioxidant agent, and more recently, for its protective function in the pathogenesis of carcinogenesis. In the present study, we sought to examine the effectiveness of honokiol in inhibiting migration and invasion of breast cancer cells and to elucidate the underlying molecular mechanisms.

METHODS

Clonogenicity and three-dimensional colony-formation assays were used to examine breast cancer cell growth with honokiol treatment. The effect of honokiol on invasion and migration of breast cancer cells was evaluated by using Matrigel invasion, scratch-migration, spheroid-migration, and electric cell-substrate impedance sensing (ECIS)-based migration assays. Western blot and immunofluorescence analysis were used to examine activation of the liver kinase B1 (LKB1)-AMP-activated protein kinase (AMPK) axis. Isogenic LKB1-knockdown breast cancer cell line pairs were developed. Functional importance of AMPK activation and LKB1 overexpression in the biologic effects of honokiol was examined by using AMPK-null and AMPK-wild type (WT) immortalized mouse embryonic fibroblasts (MEFs) and isogenic LKB1-knockdown cell line pairs. Finally, mouse xenografts, immunohistochemical and Western blot analysis of tumors were used.

RESULTS

Analysis of the underlying molecular mechanisms revealed that honokiol treatment increases AMP-activated protein kinase (AMPK) phosphorylation and activity, as evidenced by increased phosphorylation of the downstream target of AMPK, acetyl-coenzyme A carboxylase (ACC) and inhibition of phosphorylation of p70S6kinase (pS6K) and eukaryotic translation initiation factor 4E binding protein 1 (4EBP1). By using AMPK-null and AMPK-WT (MEFs), we found that AMPK is required for honokiol-mediated modulation of pACC-pS6K. Intriguingly, we discovered that honokiol treatment increased the expression and cytoplasmic translocation of tumor-suppressor LKB1 in breast cancer cells. LKB1 knockdown inhibited honokiol-mediated activation of AMPK and, more important, inhibition of migration and invasion of breast cancer cells. Furthermore, honokiol treatment resulted in inhibition of breast tumorigenesis in vivo. Analysis of tumors showed significant increases in the levels of cytoplasmic LKB1 and phospho-AMPK in honokiol-treated tumors.

CONCLUSIONS

Taken together, these data provide the first in vitro and in vivo evidence of the integral role of the LKB1-AMPK axis in honokiol-mediated inhibition of the invasion and migration of breast cancer cells. In conclusion, honokiol treatment could potentially be a rational therapeutic strategy for breast carcinoma.