Circumvention of Nuclear Factor κB-Induced Chemoresistance by Cytoplasmic-Targeted Anthracyclines

Pivarubicin Is More Effective Than Doxorubicin Against Triple-Negative Breast Cancer In Vivo

Triple-negative breast cancer (TNBC) is unresponsive to antiestrogen and anti-HER2 therapies, requiring the use of cytotoxic drug combinations of anthracyclines, taxanes, cyclophosphamide, and platinum compounds. Multidrug therapies achieve pathological cure rates of only 20–40%, a consequence of drug resistance and cumulative dose limitations necessitated by the reversible cardiotoxic effects of drug therapy. Safer and more effective treatments for TNBC are required to achieve durable therapeutic responses. This study describes the mechanistic analyses of the novel anthracycline, pivarubicin, and its in vivo efficacy against human primary TNBC. Pivarubicin directly activates PKCd, triggers rapid mitochondrial-dependent apoptosis, and circumvents resistance conferred by overexpression of P-glycoprotein, Bcl-2, Bcl-X_L, and Bcr-Abl. As a consequence, pivarubicin is more cytotoxic than doxorubicin against MDA-MB-231, and SUM159 TNBC cell lines grown in both monolayer culture and tumorspheres. Comparative in vivo efficacy of pivarubicin and doxorubicin was performed in an orthotopic NSG mouse model implanted with MDA-MB-231 human TNBC cells and treated with the maximum tolerated doses (MTDs) of pivarubicin and doxorubicin. Tumor growth was monitored by digital caliper measurements and determination of endpoint tumor weight and volume. Endpoint cardiotoxicity was assessed histologically by identifying microvacuolization in ventricular cardiomyocytes. Primary tumors treated with multiple rounds of doxorubicin at MTD failed to inhibit tumor growth compared with vehicle-treated tumors. However, administration of a single MTD of pivarubicin produced significant inhibition of tumor growth and tumor regression relative to tumor volume prior to initiation of treatment. Histological analysis of hearts excised from drug- and vehicle-treated mice revealed that pivarubicin produced no evidence of myocardial damage at a therapeutic dose. These results support the development of pivarubicin as a safer and more effective replacement for doxorubicin against TNBC as well as other malignancies for which doxorubicin therapy is indicated.

miR-199a-5p is involved in doxorubicin resistance of non-small cell lung cancer (NSCLC) cells

Non-small cell lung cancer (NSCLC) is one of the prevalent and deadly cancers worldwide. Chemotherapy resistance is one of the most challenging problems for NSCLC and other cancer treatment. Recent study suggested that miRNAs are involved in therapeutic functions of chemotherapy during cancer treatment. Our present study established doxorubicin (Dox) resistant NSCLC A549 and H460 cells (named A549Dox/R and H460 Dox/R). We found that miR-199a-5p was significantly down regulated in Dox resistant cells. Over expression of miR-199a-5p can increase the Dox sensitivity of resistant cells. Among various targets of miR-199a-5p, chemoresistance can increase the expression of ABCC1 and HIF-1α. Gain and loss of function studies confirmed that both ABCC1 and HIF-1α were involved in the chemoresistance of NSCLC cells. Collectively, our data showed that miR-199a-5p regulated expression of ABCC1 and HIF-1α were involved in Dox resistance of NSCLC.

pH-Sensitive pullulan–DOX conjugate nanoparticles for co-loading PDTC to suppress growth and chemoresistance of hepatocellular carcinoma

Co-delivery of DOX and PDTC using pH-sensitive pullulan–DOX conjugate nanoparticles helped to suppress growth and chemoresistance of hepatocellular carcinoma.

N-benzyladriamycin-14-valerate (AD 198) exhibits potent anti-tumor activity on TRAF3-deficient mouse B lymphoma and human multiple myeloma

Background

TRAF3, a new tumor suppressor identified in human non-Hodgkin lymphoma (NHL) and multiple myeloma (MM), induces PKCδ nuclear translocation in B cells. The present study aimed to evaluate the therapeutic potential of two PKCδ activators, N-Benzyladriamycin-14-valerate (AD 198) and ingenol-3-angelate (PEP005), on NHL and MM.

Methods

In vitro anti-tumor activities of AD 198 and PEP005 were determined using TRAF3^-/- mouse B lymphoma and human patient-derived MM cell lines as model systems. In vivo therapeutic effects of AD 198 were assessed using NOD SCID mice transplanted with TRAF3^-/- mouse B lymphoma cells. Biochemical studies were performed to investigate signaling mechanisms induced by AD 198 or PEP005, including subcellular translocation of PKCδ.

Results

We found that AD 198 exhibited potent in vitro and in vivo anti-tumor activity on TRAF3^-/- tumor B cells, while PEP005 displayed contradictory anti- or pro-tumor activities on different cell lines. Detailed mechanistic investigation revealed that AD 198 did not affect PKCδ nuclear translocation, but strikingly suppressed c-Myc expression and inhibited the phosphorylation of ERK, p38 and JNK in TRAF3^-/- tumor B cells. In contrast, PEP005 activated multiple signaling pathways in these cells, including PKCδ, PKCα, PKCϵ, NF-κB1, ERK, JNK, and Akt. Additionally, AD198 also potently inhibited the proliferation/survival and suppressed c-Myc expression in TRAF3-sufficient mouse and human B lymphoma cell lines. Furthermore, we found that reconstitution of c-Myc expression conferred partial resistance to the anti-proliferative/apoptosis-inducing effects of AD198 in human MM cells.

Conclusions

AD 198 and PEP005 have differential effects on malignant B cells through distinct biochemical mechanisms. Our findings uncovered a novel, PKCδ-independent mechanism of the anti-tumor effects of AD 198, and suggest that AD 198 has therapeutic potential for the treatment of NHL and MM involving TRAF3 inactivation or c-Myc up-regulation.

A phase I trial of liposomal doxorubicin, bevacizumab, and temsirolimus in patients with advanced gynecologic and breast malignancies

PURPOSE

Liposomal doxorubicin (D) and bevacizumab (A) are active single agents in gynecologic and breast malignancies which share a resistance mechanism: upregulation of hypoxia inducible factor (HIF-1α). We, therefore, added temsirolimus (T), which inhibits HIF-1α, to D and A (DAT). Trial objectives were assessment of safety, preliminary efficacy, and identification of biological response correlates.

PATIENTS AND METHODS

Cycle length was 21 days, with IV D, A, and T on day 1; T on days 8 and 15 (3+3 dose-escalation design with expansion cohorts). Mutational assays for PIK3CA, BRAF, KRAS, and immunhistochemistry for PTEN loss were conducted.

RESULTS

This article details 74 patients with gynecologic and breast malignancies who received at least one dose of drug on study. Median patient age: 52 (27-79); prior regimens: 4 (1-11). Responses: 1 (1.4%) complete response (CR), 14 (18.9%) partial responses (PR), and 13 (17.6%) with stable disease (SD) ≥ 6 months (total = 37.9%). The most common grade 1 toxicities were fatigue (27%) and anemia (20.2%). Notable grade 3/4 toxicities: thrombocytopenia (9.5%), mucositis (6.7%), and bowel perforation (2.7%). PIK3CA mutations or PTEN loss were identified in 25 of 59 (42.3%) of tested patients. Among these, nine (36%) achieved CR/PR and four (16%) had SD ≥ 6 months (CR+PR+SD ≥ 6 months = 52%).

CONCLUSIONS

DAT is well tolerated with manageable side effects. Responses observed warrant further evaluation. Mutational analyses were notable for a high percentage of responders with phosphoinositide-3-kinase pathway aberrations.

Protection from doxorubicin-induced cardiomyopathy using the modified anthracycline N-benzyladriamycin-14-valerate (AD 198)

The anthracycline doxorubicin (Dox) is an effective antitumor agent. However, its use is limited because of its toxicity in the heart. N-Benzyladriamycin-14-valerate (AD 198) is a modified anthracycline with antitumor efficacy similar to that of Dox, but with significantly less cardiotoxicity and potentially cardioprotective elements. In the present study, we investigated the possibility of in vivo protective effects of low-dose AD 198 against Dox-induced cardiomyopathy. To do this, rats were divided into four groups: vehicle, Dox (20 mg/kg; single injection day 1), AD 198 (0.3 mg/kg per injection; injections on days 1, 2, and 3), or a combination treatment of Dox + AD 198. Seventy-two hours after beginning treatment, hearts from the Dox group had decreased phosphorylation of AMP kinase and troponin I and reduced poly(ADP-ribose) polymerase, β-tubulin, and serum albumin expression. Dox also increased the phosphorylation of phospholamban and expression of inducible nitric-oxide synthase in hearts. Each of these Dox-induced molecular changes was attenuated in the Dox + AD 198 group. In addition, excised hearts from rats treated with Dox had a 25% decrease in left ventricular developed pressure (LVDP) and a higher than normal increase in LVDP when perfused with a high extracellular Ca(2+) solution. The Dox-induced decrease in baseline LVDP and hyper-responsiveness to [Ca(2+)] was not observed in hearts from the Dox + AD 198 group. Thus Dox, with well established and efficient antitumor protocols, in combination with low levels of AD 198, to counter anthracycline cardiotoxicity, may be a promising next step in chemotherapy.

RNA aptamer-targeted inhibition of NF-kappa B suppresses non-small cell lung cancer resistance to doxorubicin

Due to the prevalence of tumor chemoresistance, the clinical response of advanced non-small cell lung cancer (NSCLC) to chemotherapy is poor. We suppressed tumor resistance to doxorubicin (Dox) in A549 cells, a human NSCLC cell line, both in vitro and in vivo in a lung tumor xenograft model, using a novel adenoviral expression system to deliver an RNA aptamer (A-p50) that specifically inhibits nuclear factor-kappaB (NF-kappaB) activation. By achieving selective, targeted, and early inhibition of NF-kappaB activity, we demonstrate that NF-kappaB plays a critical role in Dox-induced chemoresistance by regulating genes involved in proliferation (Ki-67), response to DNA damage (GADD153), antiapoptosis (Bcl-XL), and pH regulation (CA9). This Dox-induced NF-kappaB activation and subsequent chemoresistance is dependent on expression of p53. We also demonstrate that NF-kappaB promotes angiogenesis in the presence of Dox via the hypoxia-inducible factor-1alpha/vascular endothelial growth factor (HIF-1alpha/VEGF) pathway, revealing a previously unknown mechanism of NSCLC resistance to Dox. These studies provide important insights into the mechanisms of Dox-induced chemoresistance, and they demonstrate a novel, effective, and clinically practical strategy for interfering with these processes.

N-Benzyladriamycin-14-valerate (AD 198): a non-cardiotoxic anthracycline that is cardioprotective through PKC-epsilon activation

N-Benzyladriamycin-14-valerate (AD 198) is one of several novel anthracycline protein kinase C (PKC)-activating agents developed in our laboratories that demonstrates cytotoxic superiority over doxorubicin (Adriamycin; DOX) through its circumvention of multiple mechanisms of drug resistance. This characteristic is attributed at least partly to the principal cellular action of AD 198: PKC activation through binding to the C1b (diacylglycerol binding) regulatory domain. A significant dose-limiting effect of DOX is chronic, dose-dependent, and often irreversible cardiotoxicity ascribed to the generation of reactive oxygen species (ROS) from the semiquinone ring structure of DOX. Despite the incorporation of the same ring structure in AD 198, we hypothesized that AD 198 might also be cardioprotective through its ability to activate PKC-epsilon, a key component of protective ischemic preconditioning in cardiomyocytes. Chronic administration of fractional LD(50) doses of DOX and AD 198 to mice results in histological evidence of dose-dependent ventricular damage by DOX but is largely absent from AD 198-treated mice. The absence of significant cardiotoxicity with AD 198 occurs despite the equal ability of DOX and AD 198 to generate ROS in primary mouse cardiomyocytes. Excised rodent hearts perfused with AD 198 prior to hypoxia induced by vascular occlusion are protected from functional impairment to an extent comparable to preconditioning ischemia. AD 198-mediated cardioprotection correlates with increased PKC-epsilon activation and is inhibited in hearts from PKC-epsilon knockout mice. These results suggest that, despite ROS production, the net cardiac effect of AD 198 is protection through activation of PKC-epsilon.

Celecoxib enhances doxorubicin-induced cytotoxicity in MDA-MB231 cells by NF-κB-mediated increase of intracellular doxorubicin accumulation

Non-steroidal anti-inflammatory drugs (NSAIDs) and cyclo-oxygenase (COX) inhibitors are anti-inflammatory agents that have also shown to be useful in anticancer therapy. In the present study, we show that the specific COX-2 inhibitor celecoxib enhances the inhibitory effect of doxorubicin (dox) on human MDA-MB231 breast tumour growth in vivo and in vitro. We also found that celecoxib increased the intracellular accumulation and retention of dox in vitro. Since the NSAID indomethacin and the specific COX-2 inhibitor NS398 did not affect the in vitro actions of dox, these effects are likely to be mediated via a COX-independent mechanism. It has been suggested that some COX-inhibitors can enhance the actions of cytostatics by overcoming multidrug resistance through the inhibition of ABC-transporter proteins. However, we found that the three main ATP-binding cassette (ABC)-transporter proteins, implicated in dox transport, were inactive in MDA-MB231 cells. Therefore, the finding that the P-glycoprotein (P-gp) blocker PSC833 also increased cellular accumulation of dox was unexpected. In order to unravel the molecular mechanisms involved in dox accumulation, we examined the involvement of NF-kappaB, as this transcription factor has been implicated in celecoxib action as well as in chemoresistance. We found that celecoxib and PSC833, but not indomethacin or NS398, almost completely inhibited basal- and dox induced NF-kappaB gene-reporter activity and p65 subunit nuclear translocation. Furthermore, the NF-kappaB inhibitor PDTC mimicked the actions of celecoxib and PSC833 on cell growth and on intracellular accumulation of dox, suggesting that NF-kappaB is functionally involved in the actions of these compounds. In conclusion, we show that structurally different compounds, among which are celecoxib and PSC833, increase the intracellular accumulation of dox and enhance dox induced cytotoxicity in MDA-MB231 breast cancer cells most likely via the modulation of NF-kappaB activity.

N-Benzyladriamycin-14-valerate (AD 198) cytotoxicty circumvents Bcr-Abl anti-apoptotic signaling in human leukemia cells and also potentiates imatinib cytotoxicity

Bcr-Abl activity in chronic myelogenous leukemia (CML) results in dysregulated cell proliferation and resistance against multiple cytotoxic agents due to the constitutive activation of proliferative signaling pathways. Currently, the most effective treatment of CML is the inhibition of Bcr-Abl activity by imatinib mesylate (Gleevec). Imatinib efficacy is limited by development of resistance through either expression of Bcr-Abl variants that bind imatinib less avidly, increased expression of Bcr-Abl, or expression of multidrug transport proteins. N-Benzyladriamycin-14-valerate (AD 198) is a novel antitumor PKC activating agent that triggers rapid apoptosis through PKC-delta activation and mitochondrial depolarization in a manner that is unaffected by Bcl-2 expression. We demonstrate that Bcr-Abl expression does not confer resistance to AD 198. Further, AD 198 rapidly induces Erk1/2 and STAT5 phosphorylation prior to cytochrome c release from mitochondria, indicating that proliferative pathways are active even as drug-treated cells undergo apoptosis. At sub-cytotoxic doses, AD 198 and its cellular metabolite, N-benzyladriamycin (AD 288) sensitize CML cells to imatinib through a supra-additive reduction in the level of Bcr-Abl protein expression. These results suggest that AD 198 is an effective treatment for CML both in combination with imatinib and alone against imatinib-resistant CML cells.

Signals from within: the DNA-damage-induced NF-kappaB response

An appropriate response to genotoxic stress is essential for maintenance of genome stability and avoiding the passage to neoplasia. Nuclear factor kappaB (NF-kappaB) is activated as part of the DNA damage response and is thought to orchestrate a cell survival pathway, which, together with the activation of cell cycle checkpoints and DNA repair, allows the cell in cases of limited damage to restore a normal life cycle, unharmed. In this respect, NF-kappaB is one of the main factors accounting for chemotherapy resistance and as such impedes effective cancer treatment, representing an important drug target. Despite this high clinical relevance, signalling cascades leading to DNA damage-induced NF-kappaB activation are poorly understood and the use of highly divergent experimental set-ups in the past led to many controversies in the field. Therefore, in this review, we will try to summarize the current knowledge of distinct DNA damage-induced NF-kappaB signalling pathways.

N-benzyladriamycin-14-valerate (AD 198) activates protein kinase C-?? holoenzyme to trigger mitochondrial depolarization and cytochrome c release independently of permeability transition pore opening and Ca2+ influx

Unlike nuclear-targeted anthracyclines, the extranuclear-targeted doxorubicin congener, N-benzyladriamycin-14-valerate (AD 198), does not interfere with normal topoisomerase II activity, but binds to the C1b regulatory domain of conventional and novel isoforms of protein kinase C (PKC). The resulting interaction leads to enzyme activation and rapid apoptosis in a variety of mammalian cell lines through a pathway involving mitochondrial events such as membrane depolarization (Deltapsim) and cytochrome c release. Unlike other triggers of apoptosis, AD 198-mediated apoptosis is unimpeded by the expression of Bcl-2 and Bcl-XL. We have further examined AD 198-induced apoptosis in 32D.3 mouse myeloid cells to determine how the anti-apoptotic effects of Bcl-2 are circumvented. The PKC-delta inhibitor, rottlerin, and transfection with a transdominant-negative PKC-delta expression vector both inhibit AD 198 cytotoxicity through inhibition of Deltapsim and cytochrome c release. While the pan-caspase inhibitor Z-VAD-FMK blocks AD 198-induced PKC-delta cleavage, however, it does not inhibit Deltapsim and cytochrome c release, indicating that AD 198 induces PKC-delta holoenzyme activation to achieve apoptotic mitochondrial effects. AD 198-mediated Deltapsim and cytochrome c release are also unaffected by cellular treatment with either the mitochondrial permeability transition pore complex (PTPC) inhibitor cyclosporin A or the Ca chelators EGTA and BAPTA-AM. These results suggest that AD 198 activates PKC-delta holoenzyme, resulting in Deltapsim and cytochrome c release through a mechanism that is independent of both PTPC activation and Ca flux across the mitochondria. PTPC-independent mitochondrial activation by AD 198 is consistent with the inability of Bcl-2 and Bcl-XL expression to block AD 198-induced apoptosis.

Differential regulation of NF-kappaB activation and function by topoisomerase II inhibitors

Background

While many common chemotherapeutic drugs and other inducers of DNA-damage result in both NF-κB nuclear translocation and DNA-binding, we have previously observed that, depending on the precise stimulus, there is great diversity of the function of NF-κB. In particular, we found that treatment of U-2 OS osteosarcoma cells with the anthracycine daunorubicin or with ultraviolet (UV-C) light resulted in a form of NF-κB that repressed rather than induced NF-κB reporter plasmids and the expression of specific anti-apoptotic genes. Anthracyclines such as daunorubicin can induce DNA-damage though inhibiting topoisomerase II, intercalating with DNA and undergoing redox cycling to produce oxygen free radicals. In this study we have investigated other anthracyclines, doxorubicin and aclarubicin, as well as the anthracenedione mitoxantrone together with the topoisomerase II inhibitor ICRF-193, which all possess differing characteristics, to determine which of these features is specifically required to induce both NF-κB DNA-binding and transcriptional repression in U-2 OS cells.

Results

The use of mitoxantrone, which does not undergo redox cycling, and the reducing agent epigallocatechingallate (EGCG) demonstrated that oxygen free radical production is not required for induction of NF-κB DNA-binding and transcriptional repression by these agents and UV-C. In addition, the use of aclarubicin, which does not directly inhibit topoisomerase II and ICRF-193, which inhibits topoisomerase II but does not intercalate into DNA, demonstrated that topoisomerase II inhibition is not sufficient to induce the repressor form of NF-κB.

Conclusion

Induction of NF-κB DNA-binding and transcriptional repression by topoisomerase II inhibitors was found to correlate with an ability to intercalate into DNA. Although data from our and other laboratories indicates that topoisomerase II inhibition and oxygen free radicals do regulate NF-κB, they are not required for the particular ability of NF-κB to repress rather than activate transcription. Together with our previous data, these results demonstrate that the nature of the NF-κB response is context dependent. In a clinical setting such effects could profoundly influence the response to chemotherapy and suggest that new methods of analyzing NF-κB function could have both diagnostic and prognostic value.

N-Benzyladriamycin-14-Valerate (AD198) Induces Apoptosis through Protein Kinase C-δ–Induced Phosphorylation of Phospholipid Scramblase 3

Phospholipid scramblase 3 (PLS3) is an enzyme that plays a critical role in mitochondrial morphology, functions, and apoptotic response. During apoptosis, activated protein kinase C-delta (PKC-delta) translocates to mitochondria and phosphorylates PLS3. Here, we utilize an extranuclear-targeted anthracycline N-benzyladriamycin-14-valerate (AD198), a PKC-delta activator, to investigate the mechanism of PLS3 phosphorylation by PKC-delta. Overexpression of PLS3 enhanced, whereas down-regulation of PLS3 by small interfering RNA decreased, the sensitivity of AD198-induced apoptosis. Overexpression of PKC-delta, but not the kinase-defective PKC-delta, and AD198 treatment enhanced threonine phosphorylation of PLS3. The phosphorylated threonine was mapped to Thr21 of PLS3. Mutation of Thr21 to alanine did not affect mitochondrial localization of PLS3 but abolished threonine phosphorylation by PKC-delta in vitro and AD198-induced PLS3 phosphorylation in vivo. Expression of PLS3(T21A) in cells could not enhance AD198-induced apoptosis compared with expression of the wild-type PLS3. Using benzyloxycarbonyl-Val-Ala-Asp-(OMe) fluoromethyl ketone and cyclosporine A, we also showed that AD198-induced PLS3 phosphorylation occurs upstream of caspase activation and independent of mitochondrial permeability transition. These studies establish that AD198-activated PKC-delta induces phosphorylation of mitochondrial PLS3 at Thr21 and that PLS3 is a critical downstream effector of PKC-delta in AD198-induced apoptosis.

RET signals through focal adhesion kinase in medullary thyroid cancer cells

BACKGROUND

The RET proto-oncogene is implicated in medullary thyroid cancer (MTC) and has been shown to signal indirectly to focal adhesion kinase (FAK) in cell types other than MTC. We have previously shown that FAK is phosphorylated in MTC cells. We hypothesized that inhibition of RET with pharmacologic inhibitors or by depletion with siRNA would decrease FAK phosphorylation in MTC cells, thereby implicating a RET-FAK signaling pathway.

METHODS

Human MTC cells (TT cells) were treated with pharmacologic inhibitors or transfected with RET siRNA. Total protein was detected by immunoblotting. Phosphorylated FAK was detected by immunoprecipitating total FAK and immunoblotting with antiphosphotyrosine.

RESULTS

Treatment of MTC cells with the inhibitor PP2 significantly inhibited RET phosphorylation and, to a lesser extent, FAK phosphorylation. Imatinib mesylate inhibited FAK phosphorylation only at high doses. RET siRNA significantly decreased RET expression and FAK phosphorylation.

CONCLUSIONS

RET signals through FAK in MTC cells. Whether this is due to a direct or indirect interaction is not yet clear. PP2 or a similar inhibitor might be a useful treatment for MTC.