Enhancing the antiproliferative effect of topoisomerase II inhibitors using a polypeptide inhibitor of c-Myc

Tilting MYC toward cancer cell death

MYC oncoprotein promotes cell proliferation and serves as the key driver in many human cancers; therefore, considerable effort has been expended to develop reliable pharmacological methods to suppress its expression or function. Despite impressive progress, MYC-targeting drugs have not reached the clinic. Recent advances suggest that within a limited expression range unique to each tumor, MYC oncoprotein can have a paradoxical, proapoptotic function. Here we introduce a counterintuitive idea that modestly and transiently elevating MYC levels could aid chemotherapy-induced apoptosis and thus benefit the patients as much, if not more than MYC inhibition.

Liposome-coated nano doxorubicin induces apoptosis on oral squamous cell carcinoma CAL-27 cells

OBJECTIVE

This study aims to investigate the apoptotic effect of Doxorubicin and its nano-formulated form (Doxil) on oral squamous cell carcinoma CAL-27 cells.

DESIGN

Cell viability using MTT assay, mode of cell death using fluorescence analysis, expression of the apoptotic marker caspase-3 using indirect ELISA technique and expression of C-Myc gene using reverse transcriptase and real time PCR.

RESULTS

Doxil treatment resulted in a higher percentage of apoptotic cells than doxorubicin treatment, while doxorubicin treatment resulted in a higher percentage of necrotic cells than Doxil treatment. Doxil-treated cells exhibited 3.38-fold higher caspase-3 levels than control cells, while doxorubicin significantly increased caspase-3 levels by 2.72-fold. The percentage of C-Myc mRNA inhibition was 27% in doxorubicin-treated cells and 41% in Doxil-treated cells.

CONCLUSIONS

Doxil exerted a higher apoptotic effect on CAL-27 cells compared to doxorubicin. It showed a higher increase in capase-3 level than doxorubicin and also exerted a more percentage of C-Myc mRNA inhibition.

Fluidic shear stress increases the anti-cancer effects of ROS-generating drugs in circulating tumor cells

PURPOSE

Many anti-cancer drugs are used in chemotherapy; however, little is known about their efficacy against circulating tumor cells (CTCs). In this study, we investigated whether the pulsatile fluidic shear stress (SS) in human arteries can affect the efficacy of anti-cancer drugs.

METHODS

Cancer cells were circulated in our microfluidic circulatory system, and their responses to drug and SS treatments were determined using various assays. Breast and cervical cancer cells that stably expressed apoptotic sensor proteins were used to determine apoptosis in real-time by fluorescence resonance energy transfer (FRET)-based imaging microscopy. The occurrence of cell death in non-sensor cells were revealed by annexin V and propidium iodide staining. Cell viability was determined by MTT assay. Intracellular reactive oxygen species (ROS) levels were determined by staining cells with two ROS-detecting dyes: 2',7'-dichlorofluorescin diacetate and dihydroethidium.

RESULTS

Fluidic SS significantly increased the potency of the ROS-generating drugs doxorubicin (DOX) and cisplatin but had little effect on the non-ROS-generating drugs Taxol and etoposide. Co-treatment with SS and ROS-generating drugs dramatically elevated ROS levels in CTCs, while the addition of antioxidants abolished the pro-apoptotic effects of DOX and cisplatin. More importantly, the synergistic killing effects of SS and DOX or cisplatin were confirmed in circulated lung, breast, and cervical cancer cells, some of which have a strong metastatic ability.

CONCLUSIONS

These findings suggest that ROS-generating drugs are more potent than non-ROS-generating drugs for destroying CTCs under pulsatile fluidic conditions present in the bloodstream. This new information is highly valuable for developing novel therapies to eradicate CTCs in the circulation and prevent metastasis.

Tumor penetrating peptides inhibiting MYC as a potent targeted therapeutic strategy for triple-negative breast cancers

Overexpression of MYC oncogene is highly prevalent in many malignancies such as aggressive triple-negative breast cancers (TNBCs) and it is associated with very poor outcome. Despite decades of research, attempts to effectively inhibit MYC, particularly with small molecules, still remain challenging due to the featureless nature of its protein structure. Herein, we describe the engineering of the dominant-negative MYC peptide (OmoMYC) linked to a functional penetrating 'Phylomer' peptide (FPPa) as a therapeutic strategy to inhibit MYC in TNBC. We found FPPa-OmoMYC to be a potent inducer of apoptosis (with IC₅₀ from 1-2 µM) in TNBC cells with negligible effects in non-tumorigenic cells. Transcriptome analysis of FPPa-OmoMYC-treated cells indicated that the fusion protein inhibited MYC-dependent networks, inducing dynamic changes in transcriptional, metabolic, and apoptotic processes. We demonstrated the efficacy of FPPa-OmoMYC in inhibiting breast cancer growth when injected orthotopically in TNBC allografts. Lastly, we identified strong pharmacological synergisms between FPPa-OmoMYC and chemotherapeutic agents. This study highlights a novel therapeutic approach to target highly aggressive and chemoresistant MYC-activated cancers.

Far upstream element-binding protein 1 is a prognostic biomarker and promotes nasopharyngeal carcinoma progression

Nasopharyngeal carcinoma (NPC) is a malignant epithelial tumor with tremendous invasion and metastasis capacities, and it has a high incidence in southeast Asia and southern China. Previous studies identified that far upstream element-binding protein 1 (FBP1), a transcriptional regulator of c-Myc that is one of the most frequently aberrantly expressed oncogenes in various human cancers, including NPC, is an important biomarker for many cancers. Our study aimed to investigate the expression and function of FBP1 in human NPC. Quantitative real-time RT-PCR (qRT-PCR), western blot and immunohistochemical staining (IHC) were performed in NPC cells and biopsies. Furthermore, the effect of FBP1 knockdown on cell proliferation, colony formation, side population tests and tumorigenesis in nude mice were measured by MTT, clonogenicity analysis, flow cytometry and a xenograft model, respectively. The results showed that the mRNA and protein levels of FBP1, which are positively correlated with c-Myc expression, were substantially higher in NPC than that in nasopharyngeal epithelial cells. IHC revealed that the patients with high FBP1 expression had a significantly poorer prognosis compared with the patients with low expression (P=0.020). In univariate analysis, high FBP1 and c-Myc expression predicted poorer overall survival (OS) and poorer progression-free survival. Multivariate analysis indicated that high FBP1 and c-Myc expression were independent prognostic markers. Knockdown of FBP1 reduced cell proliferation, clonogenicity and the ratio of side populations, as well as tumorigenesis in nude mice. These data indicate that FBP1 expression, which is closely correlated with c-Myc expression, is an independent prognostic factor and promotes NPC progression. Our results suggest that FBP1 can not only serve as a useful prognostic biomarker for NPC but also as a potential therapeutic target for NPC patients.

Cell-penetrating peptides: strategies for anticancer treatment

Cell-penetrating peptides (CPP) provide an efficient strategy for the intracellular delivery of bioactive molecules in various biomedical applications. This review focuses on recent advances in the use of CPPs to deliver anticancer therapeutics and imaging reagents to cancer cells, along with CPP contributions to novel tumor-targeting techniques. CPPs are now used extensively to deliver a variety of therapeutics, despite lacking cell specificity and having a short duration of action. Resolution of these shortcomings to enable increased cancer cell and/or tumor specificity could improve CPP-based drug delivery strategies, expand combined drug delivery possibilities, and strengthen future clinical applications of these peptides.

Fusion of cell-penetrating peptides to thermally responsive biopolymer improves tumor accumulation of p21 peptide in a mouse model of pancreatic cancer

Current therapies for the treatment of pancreatic cancer are limited. The limitations of this type of treatment are abundant. The majority of chemotherapeutic agents used in clinics are highly toxic to both tumor cells and normal tissues due to the lack of specificity. Resistance can develop due to overexposure of these agents. To address these issues, these agents must be made more exclusive toward the tumor site. We have developed a macromolecular carrier based on the sequence of the biopolymer elastin-like polypeptide (ELP) that is able to aggregate upon reaching the externally heated tumor environment. This carrier is specific to the tumor as it only aggregates at the heated tumor site. ELP is soluble below its transition temperature but will aggregate when the temperature is raised above its transition temperature. ELP was modified by p21, a cell cycle inhibitory peptide, and the addition of Bac, a cell-penetrating peptide with nuclear localization capabilities. In this study, p21-ELP-Bac and its control, ELP-p21, were used in cell proliferation studies using the pancreatic cancer cell lines Panc-1, MiaPaca-2, and S2013. ELP-p21 had little effect on proliferation, while the half maximal inhibitory concentration of p21-ELP-Bac was ∼30 μM. As translocation across the plasma membrane is a limiting step for delivery of macromolecules, these polypeptides were utilized in a pancreatic xenograft model to study the plasma clearance, biodistribution, tumor accumulation, and tumor reduction capabilities of the polypeptide with and without a cell-penetrating peptide.

Penetrating the cell membrane, thermal targeting and novel anticancer drugs: the development of thermally targeted, elastin-like polypeptide cancer therapeutics

Therapeutic peptides offer important cancer treatment approaches. Designed to inhibit oncogenes and other oncoproteins, early therapeutic peptides applications were hampered by pharmacokinetic properties now addressed through tumor targeting strategies. Active targeting with environmentally responsive biopolymers or macromolecules enhances therapeutics accumulation at tumor sites; passive targeting with macromolecules, or liposomes, exploits angiogenesis and poor lymphatic drainage to preferentially accumulate therapeutics within tumors. Genetically engineered, thermally-responsive, elastin-like polypeptides use both strategies and cell-penetrating peptides to further intratumoral cell uptake. This review describes the development and application of cell-penetrating peptide-elastin-like polypeptide therapeutics for the thermally targeted delivery of therapeutic peptides.

A polypeptide drug carrier for maternal delivery and prevention of fetal exposure

BACKGROUND

Pregnant females are largely overlooked in drug development due to concerns for fetal health. Additionally, pregnancy is often an exclusion criterion in clinical trials, so the safety of many drugs during pregnancy is unknown.

PURPOSE

The goal of this study was to evaluate Elastin-like Polypeptide (ELP), a synthetic protein derived from human elastin, for maternally sequestered drug delivery. ELP is a versatile drug carrier with a long plasma half-life, low immunogenicity, and the ability to be fused to nearly any small molecule or protein-based therapeutic.

METHODS

We determined the pharmacokinetics, biodistribution, and fetal exposure to the ELP drug carrier using quantitative fluorescence techniques in a rat pregnancy model.

RESULTS

After either bolus IV administration or continuous infusion over five days, ELPs accumulated strongly in the kidneys, liver, and placenta, but importantly, little to no ELPs were detectable in the fetus. Within the placenta, ELPs were localized to the chorionic plate and broadly distributed within the labyrinth, but were excluded from the fetal portion of the chorionic villi.

CONCLUSION

These data indicate that ELP does not cross the placenta, and they suggest that this adaptable drug delivery system is a promising platform for prevention of fetal drug exposure.

Elastin-like polypeptides: the influence of its molecular weight on local hyperthermia-induced tumor accumulation

Elastin-like polypeptides (ELP) are thermally responsive polypeptides that are soluble in solutions at 37°C, but which aggregate above 42°C. ELP can be used as effective carrier systems of anticancer molecules, because they can be targeted to tumor sites through the application of local hyperthermia. Since molecular size largely influences how successfully therapeutic agents can cross the vasculatures of tumors, it was crucial to determine an optimal molecular size. In this study, we designed and evaluated three ELP macromolecules with varying molecular weights (43, 63, and 122 kDa), with the goal of determining which would optimize the ELP drug delivery system. The N-terminus of the ELP macromolecule was modified with the cell penetrating peptide Bac to enhance intratumoral and intracellular uptake, and it was also confirmed that each polypeptide had the target transition temperature of 37-42°C and the results of the studies, using tumor-bearing mice, showed that the tumor accumulations increased in the case of all three peptides when local hyperthermia was applied, but that the elimination patterns from these tumors varied according to peptide size. Local hyperthermia was found to produce prolonged retention of all ELP conjugates in tumors except Bac-ELP43. In addition, the pharmacokinetic analysis showed that two larger polypeptides with 63 and 122 kDa have increased AUC in comparison with the 43 kDa polypeptide. These results suggest that, when combined with local hyperthermia, the larger ELP conjugates (63 and 122 kDa) have advantages over the smaller Bac-ELP43 polypeptide in terms of enhanced permeability and higher retention effects.

Thermally targeted p21 peptide enhances bortezomib cytotoxicity in androgen-independent prostate cancer cell lines

Prostate cancer remains one of the most common malignancies in men. Besides surgical resection, treatments for prostate cancer include hormone therapy, chemotherapy, and radiation therapy. Advancement of prostate cancer to an androgen-independent state limits the potential of conventional therapeutic approaches. Bortezomib, an FDA-approved proteosomal inhibitor for the treatment of myeloid leukemia, has been shown to have a positive effect on the inhibition of prostate cancer growth. Unfortunately, bortezomib has a very narrow therapeutic window, which can lead to severe side effects. Elastin-like polypeptide (ELP) is a genetically engineered, thermally responsive macromolecular carrier that enables a targeted delivery of the bound molecule because of its soluble property under normal physiologic conditions. In addition, ELP aggregates in response to mild hyperthermia. Using ELP as a carrier, it is possible to improve the pharmacological properties of the therapeutic drug as well as reduce toxicity in normal tissues. In this work, we have investigated the combination treatment of androgen-independent prostate cancer cells with bortezomib and the C-terminal part of the p21(WAF1/CIP1) protein bound to the ELP carrier. We have found that combination treatment with bortezomib and ELP-bound p21(WAF1/CIP1) protein leads to increased cell cycle arrest as well as apoptosis with respect to single treatments. We believe that this approach represents a promising direction for the treatment of androgen-independent prostate cancer.

Structural and hydrodynamic analysis of a novel drug delivery vector: ELP[V5G3A2-150]

The therapeutic potential of elastin-like polypeptide (ELP) conjugated to therapeutic compounds is currently being investigated as an approach to target drugs to solid tumors. ELPs are hydrophobic polymers that are soluble at low temperatures and cooperatively aggregate above a transition temperature (TT), allowing for thermal targeting of covalently attached drugs. They have been shown to cooperatively transition from a disordered structure to a repeating type II β-turn structure, forming a β-spiral above the TT. Here we present biophysical measurements of the structural, thermodynamic, and hydrodynamic properties of a specific ELP being investigated for drug delivery, ELP[V5G3A2-150]. We examine the biophysical properties below and above the TT to understand and predict the therapeutic potential of ELP-drug conjugates. We observed that below the TT, ELP[V5G3A2-150] is soluble, with an extended conformation consisting of both random coil and heterogeneous β structures. Sedimentation velocity experiments indicate that ELP[V5G3A2-150] undergoes weak self-association with increasing temperature, and above the TT the hydrophobic effect drives aggregation entropically. These experiments also reveal a previously unreported temperature-dependent critical concentration (Cc) that resembles a solubility constant. Labeling ELP[V5G3A2-150] with fluorescein lowers the TT by 3.5°C at 20 μM, whereas ELP[V5G3A2-150] dissolution in physiological media (fetal bovine serum) increases the TT by ∼2.2°C.

Salinomycin increases chemosensitivity to the effects of doxorubicin in soft tissue sarcomas

Background

Chemotherapy for soft tissue sarcomas remains unsatisfactory due to their low chemosensitivity. Even the first line chemotherapeutic agent doxorubicin only yields a response rate of 18-29%. The antibiotic salinomycin, a potassium ionophore, has recently been shown to be a potent compound to deplete chemoresistant cells like cancer stem like cells (CSC) in adenocarcinomas. Here, we evaluated the effect of salinomycin on sarcoma cell lines, whereby salinomycin mono- and combination treatment with doxorubicin regimens were analyzed.

Methods

To evaluate the effect of salinomycin on fibrosarcoma, rhabdomyosarcoma and liposarcoma cell lines, cells were drug exposed in single and combined treatments, respectively. The effects of the corresponding treatments were monitored by cell viability assays, cell cycle analysis, caspase 3/7 and 9 activity assays. Further we analyzed NF-κB activity; p53, p21 and PUMA transcription levels, together with p53 expression and serine 15 phosphorylation.

Results

The combination of salinomycin with doxorubicin enhanced caspase activation and increased the sub-G1 fraction. The combined treatment yielded higher NF-κB activity, and p53, p21 and PUMA transcription, whereas the salinomycin monotreatment did not cause any significant changes.

Conclusions

Salinomycin increases the chemosensitivity of sarcoma cell lines - even at sub-lethal concentrations - to the cytostatic drug doxorubicin. These findings support a strategy to decrease the doxorubicin concentration in combination with salinomycin in order to reduce toxic side effects.

Thermally targeted delivery of a c-Myc inhibitory polypeptide inhibits tumor progression and extends survival in a rat glioma model

Treatment of glioblastoma is complicated by the tumors' high resistance to chemotherapy, poor penetration of drugs across the blood brain barrier, and damaging effects of chemotherapy and radiation to normal neural tissue. To overcome these limitations, a thermally responsive polypeptide was developed for targeted delivery of therapeutic peptides to brain tumors using focused hyperthermia. The peptide carrier is based on elastin-like polypeptide (ELP), which is a thermally responsive biopolymer that forms aggregates above a characteristic transition temperature. ELP was modified with cell penetrating peptides (CPPs) to enhance delivery to brain tumors and mediate uptake across the tumor cells' plasma membranes and with a peptide inhibitor of c-Myc (H1). In rats with intracerebral gliomas, brain tumor targeting of ELP following systemic administration was enhanced up to 5-fold by the use of CPPs. When the lead CPP-ELP-fused c-Myc inhibitor was combined with focused hyperthermia of the tumors, an additional 3 fold increase in tumor polypeptide levels was observed, and 80% reduction in tumor volume, delayed onset of tumor-associated neurological deficits, and at least doubled median survival time including complete regression in 80% of animals was achieved. This work demonstrates that a c-Myc inhibitory peptide can be effectively delivered to brain tumors.

A novel carbazole derivative, MHY407, sensitizes cancer cells to doxorubicin-, etoposide-, and radiation treatment via DNA damage

In this study, we synthesized a novel carbazole derivative, MHY407, as a sensitizer of cancer cells to increase DNA damage. We then evaluated the anticancer effects of MHY407 and identified the molecular mechanism for the sensitization of breast cancer cell lines. MHY407 significantly increased DNA damage as determined by DNA breakage, levels of damage-responsive proteins, and DNA foci. In addition, MHY407 increased p21 and decreased cyclin D1 protein levels. MHY407 also involved increased cell cycle arrest at the S phase. Furthermore, in doxorubicin and etoposide-treated breast cancer cells, co-treatment with MHY407 reduced cell viability and increased apoptosis. Co-treatment of MHY407 with doxorubicin or etoposide increased DNA damage-related proteins and foci formation, suggesting that increased DNA damage by MHY407 plays an important role in the sensitization. In addition, MHY407 also sensitized the cancer cells to DNA damaging radiation treatment. These results may contribute to the development of MHY407-based treatments for cancer patients receiving DNA-damage therapy.

Correlation between multi-drug resistance-associated membrane transport in clonal cancer cells and the cell cycle phase

Multidrug resistance driven by ABC membrane transporters is one of the major reasons for treatment failure in human malignancy. Some limited evidence has previously been reported on the cell cycle dependence of ABC transporter expression. However, it has never been demonstrated that the functional activity of these transporters correlates with the cell cycle position. Here, we studied the rate of intrinsic ABC transport in different phases of the cell cycle in cultured MCF-7 breast cancer cells. The rate was characterized in terms of the efflux kinetics from cells loaded with an ABC transporter substrate. As averaging the kinetics over a cell population could lead to errors, we studied kinetics of ABC transport at the single-cell level. We found that the rate of ABC transport in MCF-7 cells could be described by Michaelis-Menten kinetics with two classical parameters, V(max) and K(M). Each of these parameters showed similar unimodal distributions with different positions of maxima for cell subpopulations in the 2c and 4c states. Compared to the 2c cells, the 4c cells exhibited greater V(max) values, indicating a higher activity of transport. They also exhibited a greater V(max)/K(M) ratio, indicating a higher efficiency of transport. Our findings suggest that cell cycle-related modulation of MDR may need to be taken into account when designing chemotherapy regimens which include cytostatic agents.

Salinomycin sensitizes cancer cells to the effects of doxorubicin and etoposide treatment by increasing DNA damage and reducing p21 protein

BACKGROUND AND PURPOSE

Salinomycin (Sal) has recently been shown to inhibit various cancer stem cells. Here, we investigated whether Sal could sensitize cancer cells to the effects of doxorubicin (DOX) or etoposide (ETO).

EXPERIMENTAL APPROACH

Using the Comet assay, immunocytochemistry and Western blot analysis, we assessed the ability of Sal to increase DNA breakage. We performed a cell proliferation assay to determine cell viability, cellular detachment, increased pre-G1 region, Annexin V staining and TUNEL assay to measure the ability of Sal to increase apoptosis.

KEY RESULTS

Sal increased DNA breakage and phosphorylated levels of p53 and H2AX. Sal also induced the formation of DNA foci with pH2AX and 53BP1. Furthermore, Sal increased the sensitivity of cancer cells to the apoptotic effects of DOX or ETO. We found that pH2AX, pBRCA1, p53BP1 and pChk1 levels were greatly increased after co-treatment of Sal with DOX or ETO. The level of anti-apoptotic p21 protein was increased by DOX or ETO but decreased by Sal, which increased proteasome activity.

CONCLUSIONS AND IMPLICATIONS

This is the first study to report that Sal increases DNA damage, and this effect plays an important role in the increased apoptosis caused by Sal. Overall, we demonstrated that the ability of Sal to sensitize cancer cells to the effects of DOX or ETO is associated with an increase in DNA damage and a decrease in anti-apoptotic protein p21 levels. These results may contribute to the development of Sal-based chemotherapy for cancer patients receiving DOX or ETO treatment.

Cell penetrating elastin-like polypeptides for therapeutic peptide delivery

Current treatment of solid tumors is limited by side effects that result from the non-specific delivery of drugs to the tumor site. Alternative targeted therapeutic approaches for localized tumors would significantly reduce systemic toxicity. Peptide therapeutics are a promising new strategy for targeted cancer therapy because of the ease of peptide design and the specificity of peptides for their intracellular molecular targets. However, the utility of peptides is limited by their poor pharmacokinetic parameters and poor tissue and cellular membrane permeability in vivo. This review article summarizes the development of elastin-like polypeptide (ELP) as a potential carrier for thermally targeted delivery of therapeutic peptides (TP), and the use of cell penetrating peptides (CPP) to enhance the intracellular delivery of the ELP-fused TPs. CPP-fused ELPs have been used to deliver a peptide inhibitor of c-Myc function and a peptide mimetic of p21 in several cancer models in vitro, and both polypeptides are currently yielding promising results in in vivo models of breast and brain cancer.

A thermally targeted peptide inhibitor of symmetrical dimethylation inhibits cancer-cell proliferation

Targeting splicing machinery components is an underdeveloped strategy for cancer therapy. Uridine-rich small nuclear ribonucleoproteins (UsnRNPs) are essential spliceosome components that recognize splice sites in newly transcribed RNA. The major spliceosomal snRNPs are comprised of UsnRNA bound by a ring of Sm proteins. The survival of motor neuron (SMN) complex provides specificity for binding of Sm proteins to UsnRNAs. Three of the seven proteins that comprise the Sm core possess post-translationally modified C-terminal symmetric dimethylarginine (sDMA) residues which promote binding of these proteins to SMN. Here we describe a peptide inhibitor of sDMA that is capable of interfering with SMN/SmB interaction. The inhibitory peptide was attached to elastin-like polypeptide, a thermally responsive macromolecular carrier, in order to increase its stability and allow enhancement of its cellular uptake by thermal targeting. The fusion polypeptide inhibited the interaction of SMN/SmB, inhibited proliferation, and induced apoptosis in HeLa cells.

Inhibition of ovarian cancer cell proliferation by a cell cycle inhibitory peptide fused to a thermally responsive polypeptide carrier

Current treatment of solid tumors is limited by normal tissue tolerance, resulting in a narrow therapeutic index. To increase drug specificity and efficacy and to reduce toxicity in normal tissues, we have developed a polypeptide carrier for a cell cycle inhibitory peptide, which has the potential to be thermally targeted to the tumor site. The design of this polypeptide is based on elastin-like polypeptide (ELP). The coding sequence of ELP was modified by the addition of the cell penetrating peptide Bac-7 at the N-terminus and a 23 amino acid peptide derived from p21 at the C-terminus (Bac-ELP1-p21). Bac-ELP1-p21 is soluble in aqueous solutions below physiological temperature (37 degrees C) but aggregates when the temperature is raised above 39 degrees C, making it a promising thermally responsive therapeutic carrier that may be actively targeted to solid tumors by application of focused hyperthermia. While Bac-ELP1-p21 at 37 degrees C did not have any effect on SKOV-3 cell proliferation, the use of hyperthermia increased the antiproliferative effect of Bac-ELP1-p21 compared with a thermally unresponsive control polypeptide. Bac-ELP1-p21 displayed both a cytoplasmic and nuclear distribution in the SKOV-3 cells, with nuclear-localized polypeptide enriched in the heated cells, as revealed by confocal microscopy. Using Western blotting, we show that Bac-ELP1-p21 caused a decrease in Rb phosphorylation levels in cells treated at 42 degrees C. The polypeptide also induced caspase activation, PARP cleavage, and cell cycle arrest in S-phase and G2/M-phase. These studies indicate that ELP is a promising macromolecular carrier for the delivery of cell cycle inhibitory peptides to solid tumors.

Early effects of doxorubicin in perfused heart: transcriptional profiling reveals inhibition of cellular stress response genes

Doxorubicin (DXR) belongs to the most efficient anticancer drugs. However, its clinical application is limited by the risk of severe cardiac-specific toxicity, for which an efficient treatment is missing. Underlying molecular mechanisms are not sufficiently understood so far, but nonbiased, systemic approaches can yield new clues to develop targeted therapies. Here, we applied a genome-wide transcriptome analysis to determine the early cardiac response to DXR in a model characterized earlier, that is, rat heart perfusion with 2 muM DXR, leading to only mild cardiac dysfunction. Single-gene and gene set enrichment analysis of DNA microarrays yielded robust data on cardiac transcriptional reprogramming, including novel DXR-responsive pathways. Main characteristics of transcriptional reprogramming were 1) selective upregulation of individual genes or gene sets together with widespread downregulation of gene expression; 2) repression of numerous transcripts involved in cardiac stress response and stress signaling; 3) modulation of genes with cardiac remodeling capacity; 4) upregulation of "energy-related" pathways; and 5) similarities to the transcriptional response of cancer cells. Some early responses like the induction of glycolytic and Krebs cycle genes may have compensatory function. Only minor changes in the cardiac energy status or the respiratory activity of permeabilized cardiac fibers have been observed. Other responses potentially contribute to acute and also chronic toxicity, in particular, those in stress-responsive and cardiac remodeling transcripts. We propose that a blunted response to stress and reduced "danger signaling" is a prime component of toxic DXR action and can drive cardiac cells into pathology.

Application of thermally responsive elastin-like polypeptide fused to a lactoferrin-derived peptide for treatment of pancreatic cancer

A well characterized, peptide derivative of bovine lactoferrin, L12, has been shown to possess anticancer properties in multiple cell lines. However, adverse side effects in normal tissues and poor plasma kinetics that hinder the clinical effectiveness of current chemotherapeutics also deter the potential for effective delivery of this L12 peptide. To overcome these limitations, we have developed an Elastin-like polypeptide (ELP) carrier that has the potential to thermally target therapeutic peptides and chemotherapeutics to a tumor site. The coding sequence of ELP was modified with the L12 peptide at the C-terminus and a membrane transduction domain derived from the HIV-1 Tat protein at the N-terminus (Tat-ELP-L12). The thermally responsive Tat-ELP1-L12 is soluble in aqueous solutions at 37 degrees C but aggregates near 41 degrees C, which makes Tat-ELP1-L12 ideal for targeting to solid tumors on application of focused hyperthermia. We observed that under hyperthermia conditions at 42 degrees C, Tat-ELP1-L12 mediated cytotoxicity in MIA PaCa-2 pancreatic adenocarcinoma cells was enhanced by nearly thirty-fold. We investigated the mechanisms of cell death and found evidence of mitochondrial membrane depolarization and caspase activation, which are characteristic of apoptosis, as well as, increased membrane permeability, as shown by LDH release. These results suggest that Tat-ELP1-L12 possesses cytotoxic properties to cancer cells in vitro and may have the potential to provide an effective vehicle to thermally target solid tumors.

Triple negative breast cancer--current status and prospective targeted treatment based on HER1 (EGFR), TOP2A and C-MYC gene assessment

BACKGROUND

Every year about one million women worldwide are diagnosed with breast cancer which is the most common malignancy in female. Of these, triple negative breast carcinoma represents 10-17 %. Triple negative breast carcinomas, characterized by estrogen, progesterone and HER2 receptor negativity are very aggressive tumours with poor prognosis. Individualized treatment (tailored therapy) based on molecular biology markers of tumor and patient is the trend in clinical practice these days. However, molecular targets and predictors for the treatment of triple negative breast carcinoma do not currently exist.

METHODS AND RESULTS

This minireview focuses on biomarkers (HER1/EGFR, TOP2A and C-MYC genes) that may predict the response of triple negative breast carcinoma patients to chemotherapy and/or targeted biological treatment with a summary of current knowledge about them.

CONCLUSION

HER1 belonging to the HER family of receptors plays an important role in cell proliferation, migration and protection against apoptosis. HER1 protein could be targeted by monoclonal antibodies and/or tyrosine kinase inhibitors (TKIs). Given signal pathway complexity and HER family member cooperation, it may be better to simultaneously target a number of these receptors (e.g. HER1/HER2 by lapatinib). Thus, HER1 assessment could reveal a particular breast cancer patient group with probably good response to HER1 targeted therapy. TOP2A gene, encoding topoisomerase II alpha (target for anthracyclines) is predictive of response to anthracycline therapy. TOP2A aberrations (amplification, deletion) are found in up to approximately 30-90 % of HER2 amplified breast cancer and amplifications are more common than deletions. Recent publications describe TOP2A amplification also in 2.7-8.8 % HER2 nonamplified breast cancers. Patients with a pathologic complete response to anthracycline based neoadjuvant chemotherapy had a good overall prognosis regardless of molecular subtype of breast cancer. These results suggest that particularly tumors with a complete pathological response to anthracyclines could have TOP2A amplification. C-MYC encodes nuclear DNA binding proteins that regulate proliferation and apoptosis; amplification is associated with poor prognosis and hormonally negative breast carcinoma.

Targeting a c-Myc inhibitory polypeptide to specific intracellular compartments using cell penetrating peptides

The therapeutic index of current anti-cancer chemotherapeutics can be improved by two major mechanisms: 1) developing drugs which are specifically toxic to the cancer cells and 2) developing methods to deliver drugs to the tumor site. In an attempt to combine these approaches, we developed a thermally responsive polypeptide inhibitor of c-Myc. This polypeptide is based on the thermally responsive Elastin-like polypeptide (ELP). When injected systemically, ELP-fused drugs will aggregate and accumulate at the tumor site where local hyperthermia is applied. ELP was fused to a peptide which blocks c-Myc/Max dimerization (H1), thereby inhibiting transcription activation by c-Myc (ELP-H1). In this study, the cellular uptake, intracellular distribution, and potency of the Pen, Tat and Bac cell penetrating peptides fused to ELP-H1 were evaluated. While Pen-ELP-H1 and Tat-ELP-H1 were localized in the cytoplasm, Bac-ELP-H1 localized to the nucleus in a subset of the cells and was the most potent inhibitor of MCF-7 cell proliferation. This data demonstrates that ELP can be targeted to the desired cellular compartment simply by choice of the CPP used, resulting in a more potent nuclear targeted c-Myc inhibitory polypeptide which may be beneficial in cancer therapy.

Temperature sensitive peptides: engineering hyperthermia-directed therapeutics

PURPOSE

Recent progress suggests that short peptide motifs can be engineered into biopolymers with specific temperature dependent behavior. This review discusses peptide motifs capable of thermo-responsive behavior, and broadly summarizes design approaches that exploit these peptides as drug carriers. This review focuses on one class of thermally responsive peptide-based biopolymers, elastin-like polypeptides in greater detail.

ANALYSIS

Four peptide motifs are presented based on leucine zippers, human collagen, human elastin, and silkworm silk that are potential building blocks for thermally responsive biopolymers. When these short motifs (<7 amino acids) are repeated many times, they generate biopolymers with higher order structure and complex temperature triggered behaviors. These structures are thermodynamically modulated, making them intrinsically temperature sensitive. These four motifs can be categorized by the directionality and reversibility of association. Elastin-like polypeptides (ELPs) are one promising motif that reversibly associates during heating. ELPs aggregate sharply above an inverse phase transition temperature, which depends on polymer hydrophobicity, molecular weight, and concentration. ELPs can be modified with chemotherapeutics, are biodegradable, are biocompatible, have low immunogenicity, and have terminal pharmacokinetic half-lives >8 h. ELP block copolymers can reversibly form micelles in response to hyperthermia, and this behavior can modulate the binding avidity of peptide ligands. When high molecular weight ELPs are systemically administered to mice they accumulate in tumors; furthermore, hyperthermia can initiate the ELP phase transition and double the concentration of peptide in the tumor.

CONCLUSIONS

Temperature sensitive peptides are a powerful engineering platform that will enable new strategies for hyperthermia-directed drug delivery.

Increase of therapeutic effects by treating melanoma with targeted combinations of c-myc antisense and doxorubicin

Patients with advanced or metastatic melanoma have a very poor prognosis, due to the resistance of melanoma cells to conventional chemotherapy. We previously reported that coated cationic liposomes targeted with a monoclonal antibody against the disialoganglioside GD(2) and containing c-myc antisense oligodeoxynucleotides (alpha GD(2)-CCL[c-myc-as]) induced partial tumor growth arrest in melanoma xenografts. Here we addressed the role of c-myc-asODN treatment in the susceptibility to doxorubicin (DXR) in human melanoma cells. Cytotoxicity studies revealed that growth of melanoma cells was inhibited to a greater extent by alpha GD(2)-CCL[c-myc-as] than by the corresponding non-targeted formulations or by free c-myc-as. Targeted c-myc-as sensitized cells to DXR, reducing the IC(50) by approximately 10-fold. Scrambled ODNs had no effect on the IC(50) of DXR. Compared to either treatment alone, combination of targeted c-myc-as and DXR resulted in earlier apoptosis and in cell death after 2 days of treatment. In vivo experiments revealed that liposomal formulations of c-myc-as and DXR, both targeted via GD(2), led to the most pronounced delay in tumor growth when administered in a sequential manner. As a result, their combination translates into a statistically significant suppression of blood vessel density and an enhanced apoptosis, compared to all treatments given separately. Our data indicate the increasing cell sensitivity to DXR by c-myc-asODNs as a promising basis for developing novel anti-tumor strategy against advanced melanoma.

The Myc oncoprotein as a therapeutic target for human cancer

Myc expression is deregulated in a wide range of human cancers and is often associated with aggressive, poorly differentiated tumors. The Myc protein is a transcription factor that regulates a variety of cellular processes including cell growth and proliferation, cell-cycle progression, transcription, differentiation, apoptosis, and cell motility. Potential strategies that either inhibit the growth promoting effect of Myc and/or activate its pro-apoptotic function are presently being explored. In this review, we give an overview of Myc activation in human tumors and discuss current strategies aimed at targeting Myc for cancer treatment. Such therapies could have potential in combination with mechanistically different cytotoxic drugs to combat and eradicate tumors cells.