The brain-penetrant cell-cycle inhibitor p28 sensitizes brain metastases to DNA-damaging agents.

Background: Brain metastases (BMs), the most common tumors of the central nervous system, are life-threatening with a dismal prognosis. The major challenges to developing effective treatments for BMs are the limited abilities of drugs to target tumors and to cross the blood-brain barrier (BBB). We aimed to investigate the efficacy of our therapeutic approach against BMs in mouse models that recapitulate the clinical manifestations of BMs. Methods: BMs mouse models were constructed by injecting human breast, lung cancer, and melanoma intracardially, which allowed the BBB to remain intact. We investigated the ability of the cell-penetrating peptide p28 to cross the BBB in an in vitro 3D model and in the BMs animal models. The therapeutic effects of p28 in combination with DNA-damaging agents (radiation and temozolomide) on BMs were also evaluated. Results: p28 crossed the intact BBB more efficiently than the standard chemotherapeutic agent, temozolomide. Upon crossing the BBB, p28 localized preferentially to tumor lesions and enhanced the efficacy of DNA-damaging agents by activating the p53-p21 axis. In the BMs animal models, radiation in combination with p28 significantly reduced the tumor burden of BMs. Conclusions: The cell-cycle inhibitor p28 can cross the BBB localize to tumor lesions in the brain and enhance the inhibitory effects of DNA-damaging agents on BMs, suggesting the potential therapeutic benefits of this molecule in BMs.

Cross-talk between cancer and Pseudomonas aeruginosa mediates tumor suppression.

Microorganisms living at many sites in the human body compose a complex and dynamic community. Accumulating evidence suggests a significant role for microorganisms in cancer, and therapies that incorporate bacteria have been tried in various types of cancer. We previously demonstrated that cupredoxin azurin secreted by the opportunistic pathogen Pseudomonas aeruginosa, enters human cancer cells and induces apoptotic death1-4. However, the physiological interactions between P. aeruginosa and humans and their role in tumor homeostasis are largely unknown. Here, we show that P. aeruginosa upregulated azurin secretion in response to increasing numbers of and proximity to cancer cells. Conversely, cancer cells upregulated aldolase A secretion in response to increasing proximity to P. aeruginosa, which also correlated with enhanced P. aeruginosa adherence to cancer cells. Additionally, we show that cancer patients had detectable P. aeruginosa and azurin in their tumors and exhibited increased overall survival when they did, and that azurin administration reduced tumor growth in transgenic mice. Our results suggest host-bacterial symbiotic mutualism acting as a diverse adjunct to the host defense system via inter-kingdom communication mediated by the evolutionarily conserved proteins azurin and human aldolase A. This improved understanding of the symbiotic relationship of bacteria with humans indicates the potential contribution to tumor homeostasis.

Tumor-targeting cell-penetrating peptide, p28, for glioblastoma imaging and therapy.

Despite recent advances in cancer research, glioblastoma multiforme (GBM) remains a highly aggressive brain tumor as its treatment options are limited. The current standard treatment includes surgery followed by radiotherapy and adjuvant chemotherapy. However, surgery without image guidance is often challenging to achieve maximal safe resection as it is difficult to precisely discern the lesion to be removed from surrounding brain tissue. In addition, the efficacy of adjuvant chemotherapy is limited by poor penetration of therapeutics through the blood-brain barrier (BBB) into brain tissues, and the lack of tumor targeting. In this regard, we utilized a tumor-targeting cell-penetration peptide, p28, as a therapeutic agent to improve the efficacy of a current chemotherapeutic agent for GBM, and as a carrier for a fluorescence imaging agent for a clear identification of GBM. Here, we show that a near-infrared (NIR) imaging agent, ICG-p28 (a chemical conjugate of an FDA-approved NIR dye, indocyanine green ICG, and tumor-targeting p28 peptide) can preferentially localize tumors in multiple GBM animal models. Moreover, xenograft studies show that p28, as a therapeutic agent, can enhance the cytotoxic activity of temozolomide (TMZ), one of the few effective drugs for brain tumors. Collectively, our findings highlight the important role of the tumor-targeting peptide, which has great potential for intraoperative image-guided surgery and the development of new therapeutic strategies for GBM.

Nontoxic Tumor-Targeting Optical Agents for Intraoperative Breast Tumor Imaging.

Precise identification of the tumor margins during breast-conserving surgery (BCS) remains a challenge given the lack of visual discrepancy between malignant and surrounding normal tissues. Therefore, we developed a fluorescent imaging agent, ICG-p28, for intraoperative imaging guidance to better aid surgeons in achieving negative margins in BCS. Here, we determined the pharmacokinetics (PK), biodistribution, and preclinical toxicity of ICG-p28. The PK and biodistribution of ICG-p28 indicated rapid tissue uptake and localization at tumor lesions. There were no dose-related effect and no significant toxicity in any of the breast cancer and normal cell lines tested. Furthermore, ICG-p28 was evaluated in clinically relevant settings with transgenic mice that spontaneously developed invasive mammary tumors. Intraoperative imaging with ICG-p28 showed a significant reduction in the tumor recurrence rate. This simple, nontoxic, and cost-effective method can offer a new approach that enables surgeons to intraoperatively identify tumor margins and potentially improves overall outcomes by reducing recurrence rates.

Image-guided surgery with a new tumour-targeting probe improves the identification of positive margins.

BACKGROUND: Given the lack of visual discrepancy between malignant and surrounding normal tissue, current breast conserving surgery (BCS) is associated with a high re-excision rate. Due to the increasing cases of BCS, a novel method of complete tumour removal at the initial surgical resection is critically needed in the operating room to help optimize the surgical procedure and to confirm tumour-free edges. METHODS: We developed a unique near-infrared (NIR) fluorescence imaging probe, ICG-p28, composed of the clinically nontoxic tumour-targeting peptide p28 and the FDA-approved NIR dye indocyanine green (ICG). ICG-p28 was characterized in vitro and evaluated in multiple breast cancer animal models with appropriate control probes. Our experimental approach with multiple-validations and -blinded procedures was designed to determine whether ICG-p28 can accurately identify tumour margins in mimicked intraoperative settings. FINDINGS: The in vivo kinetics were analysed to optimize settings for potential clinical use. Xenograft tumours stably expressing iRFP as a tumour marker showed significant colocalization with ICG-p28, but not ICG alone. Image-guided surgery with ICG-p28 showed an over 6.6 × 103-fold reduction in residual normalized tumour DNA at the margin site relative to control approaches (i.e., surgery with ICG or palpation/visible inspection alone), resulting in an improved tumour recurrence rate (92% specificity) in multiple breast cancer animal models independent of the receptor expression status. ICG-p28 allowed accurate identification of tumour cells in the margin to increase the complete resection rate. INTERPRETATION: Our simple and cost-effective approach has translational potential and offers a new surgical procedure that enables surgeons to intraoperatively identify tumour margins in a real-time, 3D fashion and that notably improves overall outcomes by reducing re-excision rates. FUNDING: This work was supported by NIH/ National Institute of Biomedical Imaging and Bioengineering, R01EB023924.

A Method of Tumor In Vivo Imaging with a New Peptide-Based Fluorescent Probe.

Precise surgical resection directly influences the prognosis and survival of patients with solid tumors. However, it is often difficult to distinguish tumor from normal tissue during resection without any intraoperative imaging guidance. Image-guided surgery particularly when coupled with a near-infrared (NIR) fluorescent agent may improve positive-margin rate thereby improving the overall prognosis. We have developed a unique tumor-targeting fluorescence imaging agent that can aid in the accurate localization of human cancer cells in preclinical settings. The NIR imaging agent, ICG-p28, a water-soluble, nontoxic, and pan-tumor targeting probe consisting of a cell-penetrating peptide (p28) conjugated to indocyanine green (ICG), can accurately localize tumors in vivo. Development of the noninvasive, targeted imaging agent can potentially improve in the resections of tumors by enabling the localization of lesions that are currently difficult or impossible to detect by visual observation or palpation. Here, we describe the methods of preclinical animal imaging models by using NIR fluorescence imager coupled with a new tumor-targeting agent.

p28-Mediated Activation of p53 in G2-M Phase of the Cell Cycle Enhances the Efficacy of DNA Damaging and Antimitotic Chemotherapy.

p28 is an anionic cell-penetrating peptide of 28 amino acids that activates wild-type and mutated p53, leading subsequently to selective inhibition of CDK2 and cyclin A expression and G2-M cell-cycle arrest. In this study, we investigated the cytotoxic effects of p28 treatment alone and in combination with DNA-damaging and antimitotic agents on human cancer cells. p28 enhanced the cytotoxic activity of lower concentrations (IC20-50) of DNA-damaging drugs (doxorubicin, dacarbazine, temozolamide) or antimitotic drugs (paclitaxel and docetaxel) in a variety of cancer cells expressing wild-type or mutated p53. Mechanistic investigations revealed that p28 induced a post-translational increase in the expression of wild-type or mutant p53 and p21, resulting in cell-cycle inhibition at the G2-M phase. The enhanced activity of these anticancer agents in combination with p28 was facilitated through the p53/p21/CDK2 pathway. Taken together, these results highlight a new approach to maximize the efficacy of chemotherapeutic agents while reducing dose-related toxicity. Cancer Res; 76(8); 2354-65. ©2016 AACR.

p28, an anionic cell-penetrating peptide, increases the activity of wild type and mutated p53 without altering its conformation.

p28, a cell penetrating peptide, binds to the DNA binding domain (DBD) of p53, inducing a post-translational increase in intracellular levels of wild type and mutant p53 activating pathways that inhibit cancer cell proliferation at G2/M. Cancer cells respond to p28 with an increase in p53 activity, except when mutations either alter DNA contact or completely unfold the DBD. The increase in p53 activity is accompanied by a significant reduction in the level of the E3 ligase COP1, with no alteration in p53 conformation. This suggests p28 can activate p53 over a wide range of conformational mutations by inhibiting the binding of COP1 to p53.

MADD knock-down enhances doxorubicin and TRAIL induced apoptosis in breast cancer cells.

The Map kinase Activating Death Domain containing protein (MADD) isoform of the IG20 gene is over-expressed in different types of cancer tissues and cell lines and it functions as a negative regulator of apoptosis. Therefore, we speculated that MADD might be over-expressed in human breast cancer tissues and that MADD knock-down might synergize with chemotherapeutic or TRAIL-induced apoptosis of breast cancer cells. Analyses of breast tissue microarrays revealed over-expression of MADD in ductal and invasive carcinomas relative to benign tissues. MADD knockdown resulted in enhanced spontaneous apoptosis in human breast cancer cell lines. Moreover, MADD knockdown followed by treatment with TRAIL or doxorubicin resulted in increased cell death compared to either treatment alone. Enhanced cell death was found to be secondary to increased caspase-8 activation. These data indicate that strategies to decrease MADD expression or function in breast cancer may be utilized to increase tumor cell sensitivity to TRAIL and doxorubicin induced apoptosis.

A cell penetrating peptide derived from azurin inhibits angiogenesis and tumor growth by inhibiting phosphorylation of VEGFR-2, FAK and Akt.

Amino acids 50-77 (p28) of azurin, a 128 aa cupredoxin isolated from Pseudomonas aeruginosa, is essentially responsible for azurin's preferential penetration of cancer cells. We now report that p28 also preferentially penetrates human umbilical vein endothelial cells (HUVEC), co-localized with caveolin-1 and VEGFR-2, and inhibits VEGF- and bFGF-induced migration, capillary tube formation and neoangiogenesis in multiple xenograft models. The antiangiogenic effect of p28 in HUVEC is associated with a dose-related non-competitive inhibition of VEGFR-2 kinase activity. However, unlike other antiangiogenic agents that inhibit the VEGFR-2 kinase, p28 decreased the downstream phosphorylation of FAK and Akt that normally precedes cellular repositioning of the cytoskeletal (F-actin), focal adhesion (FAK and paxillin), and cell to cell junction protein PECAM-1, inhibiting HUVEC motility and migration. The decrease in pFAK and pAkt levels suggests that p28 induces a pFAK-mediated loss of HUVEC motility and migration and a parallel Akt-associated reduction in cell matrix attachment and survival. This novel, direct antiangiogenic effect of p28 on endothelial cells may enhance the cell cycle inhibitory and apoptotic properties of this prototype peptide on tumor cell proliferation as it enters a Phase II clinical trial.

Preclinical pharmacokinetics, metabolism, and toxicity of azurin-p28 (NSC745104) a peptide inhibitor of p53 ubiquitination.

PURPOSE: Characterize the preclinical pharmacokinetics, metabolic profile, multi-species toxicology, and antitumor efficacy of azurin-p28 (NSC 745104), an amphipathic, 28 amino acid fragment (aa 50-77) of the copper containing redox protein azurin that preferentially enters cancer cells and is currently under development for treatment of p53-positive solid tumors. METHODS: An LC/MS/MS assay was developed, validated, and applied to liver microsomes, serum, and tumor cells to assess cellular uptake and metabolic stability. Pharmacokinetics was established after administration of a single intravenous dose of p28 in preclinical species undergoing chronic toxicity testing. Antitumor efficacy was assessed on human tumor xenografts. A human therapeutic dose was predicted based on efficacy and pharmacokinetic parameters. RESULTS: p28 is stable, showed tumor penetration consistent with selective entry into tumor cells and significantly inhibited p53-positive tumor growth. Renal clearance, volume of distribution, and metabolic profile of p28 was relatively similar among species. p28 was non-immunogenic and non-toxic in mice and non-human primates (NHP). The no observed adverse effect level (NOAEL) was 120 mg/kg iv in female mice. A NOAEL was not established for male mice due to decreased heart and thymus weights that was reversible and did not result in limiting toxicity. In contrast, the NOAEL for p28 in NHP was defined as the highest dose (120 mg/kg/dose; 1,440 mg/m(2)/dose) studied. The maximum-tolerated dose (MTD) for subchronic administration of p28 to mice is >240 mg/kg/dose (720 mg/m(2)/dose), while the MTD for subchronic administration of p28 to Cynomolgous sp. is >120 mg/kg (1,440 mg/m(2)/dose). The efficacious (murine) dose of p28 was 10 mg/kg ip per day. CONCLUSIONS: p28 does not exhibit preclinical immunogenicity or toxicity, has a similar metabolic profile among species, and is therapeutic in xenograft models.

A 28-amino-acid peptide fragment of the cupredoxin azurin prevents carcinogen-induced mouse mammary lesions.

Azurin, a member of the cupredoxin family of redox proteins, preferentially penetrates human cancer cells and exerts cytostatic and apoptotic effects. Azurin and amino acids 50-77 (p28) of azurin also produce a dose-dependent reduction in the proliferation of human mammary cancer by increasing the level of the tumor suppressor protein p53 in the cancer cell nucleus. We show that the development of 7,12-dimethylbenz[a]anthracene-induced hormone-dependent premalignant mammary ductal lesions and hormone-independent mammary alveolar lesions in mouse mammary gland organ culture is also significantly reduced by azurin and p28. The dose-dependent reduction in carcinogen-induced mammary cell proliferation by p28 was associated with an increase in the expression of p53. p28 also enhanced the inhibitory effect of a low dose of the antiestrogen tamoxifen on the development of hormone-dependent mammary ductal lesions, but did not enhance the inhibitory activity of fenretinide (N-4-hydroxyphenyl retinamide) on hormone-independent mammary alveolar lesions. These observations suggest that cupredoxins and fragments derived from them can exert a chemopreventive effect on carcinogen-induced mammary gland transformation, irrespective of hormonal environment, and enhance the inhibitory effects of tamoxifen in this model of preneoplastic mammary development.

A peptide fragment of azurin induces a p53-mediated cell cycle arrest in human breast cancer cells.

We report that amino acids 50 to 77 of azurin (p28) preferentially enter the human breast cancer cell lines MCF-7, ZR-75-1, and T47D through a caveolin-mediated pathway. Although p28 enters p53 wild-type MCF-7 and the isogenic p53 dominant-negative MDD2 breast cancer cell lines, p28 only induces a G(2)-M-phase cell cycle arrest and apoptosis in MCF-7 cells. p28 exerts its antiproliferative activity by reducing proteasomal degradation of p53 through formation of a p28:p53 complex within a hydrophobic DNA-binding domain (amino acids 80-276), increasing p53 levels and DNA-binding activity. Subsequent elevation of the cyclin-dependent kinase inhibitors p21 and p27 reduces cyclin-dependent kinase 2 and cyclin A levels in a time-dependent manner in MCF-7 cells but not in MDD2 cells. These results suggest that p28 and similar peptides that significantly reduce proteasomal degradation of p53 by a MDM2-independent pathway(s) may provide a unique series of cytostatic and cytotoxic (apoptotic) chemotherapeutic agents.

Bacterial proteins as potential drugs in the treatment of leukemia.

Azurin and Laz are bacterial proteins that have been shown to exert anticancer effects against a variety of solid tumors. Their effects on liquid cancers have never been studied. We now show that they are also effective against liquid-borne cancers such as leukemia. Azurin and Laz can each enter in two leukemia cell lines but Laz exerts a greater cytotoxic effect on both K562 and HL60 cells, while having little effect on peripheral blood mononuclear cells, where they have very limited entry. In addition to Azurin and Laz, we have recently identified another protein, Pa-CARD, from Pseudomonas aeruginosa that carries a caspase recruitment domain (CARD)-like domain. This CARD domain polypeptide, called Pa-CARD, demonstrates cytotoxic activity against leukemia cells. In the leukemia cell lines, HL60 and K562, the anticancer activity of Laz and Pa-CARD is mediated through cell cycle arrest at the G2/M phase involving the Wee1 protein stabilization and the depletion of phosphorylated AKT-Ser-473, the active form of a serine/threonine kinase that is often dysregulated in many cancer types.

Noncationic peptides obtained from azurin preferentially enter cancer cells.

Azurin, a member of the cupredoxin family of copper containing redox proteins, preferentially penetrates human cancer cells and exerts cytostatic and cytotoxic (apoptotic) effects with no apparent activity on normal cells. Amino acids 50 to 77 (p28) of azurin seem responsible for cellular penetration and at least part of the antiproliferative, proapoptotic activity of azurin against a number of solid tumor cell lines. We show by confocal microscopy and fluorescence-activated cell sorting that amino acids 50 to 67 (p18) are a minimal motif (protein transduction domain) responsible for the preferential entry of azurin into human cancer cells. A combination of inhibitors that interfere with discrete steps of the endocytotic process and antibodies for caveolae and Golgi-mediated transport revealed that these amphipathic, alpha-helical peptides are unique. Unlike the cationic cell-penetrating peptides, alpha-helical antennapedia-like, or VP22 type peptides, p18 and p28 are not bound by cell membrane glycosaminoglycans and preferentially penetrate cancer cells via endocytotic, caveosome-directed, and caveosome-independent pathways. Once internalized, p28, but not p18, inhibits cancer cell proliferation initially through a cytostatic mechanism. These observations suggest the azurin fragments, p18 and p28, account for the preferential entry of azurin into human cancer cells and a significant amount of the antiproliferative activity of azurin on human cancer cells, respectively.

Randomized trial of an allogeneic melanoma lysate vaccine with low-dose interferon Alfa-2b compared with high-dose interferon Alfa-2b for Resected stage III cutaneous melanoma.

PURPOSE: To compare the overall survival (OS) of patients with resected stage III melanoma administered active specific immunotherapy and low-dose interferon alfa-2b (IFN-alpha-2b) with the OS achieved using high-dose IFN-alpha-2b. PATIENTS AND METHODS: An Ad Hoc Melanoma Working Group of 25 investigators treated 604 patients from April 1997 to January 2003. Patients were stratified by sex and number of nodes and were randomly assigned to receive either 2 years of treatment with active specific immunotherapy with allogeneic melanoma lysates and low-dose IFN-alpha-2b (arm 1) or high-dose IFN-alpha-2b alone for 1 year (arm 2). Active specific immunotherapy was injected subcutaneously (SC) weekly for 4 weeks, at week 8, and bimonthly thereafter. IFN-alpha-2b SC was begun on week 4 and continued thrice weekly at 5 MU/m2 for 2 years. IFN-alpha-2b in arm 2 was administered according to the Eastern Cooperative Oncology Group 1684 study regimen. RESULTS: Median follow-up time was 32 months for all patients and 42 months for surviving patients. Median OS time exceeds 84 months in arm 1 and is 83 months in arm 2 (P = .56). Five-year OS rate is 61% in arm 1 and 57% in arm 2. Estimated 5-year relapse-free survival (RFS) rate is 50% in arm 1 and 48% in arm 2, with median RFS times of 58 and 50 months, respectively. The incidence of serious adverse events as a result of treatment was the same in both arms, but more severe neuropsychiatric toxicity was seen in arm 2. CONCLUSION: OS and RFS achieved by active specific immunotherapy and low-dose IFN-alpha-2b were indistinguishable from those achieved by high-dose IFN-alpha-2b. Long RFS and OS times were observed in both treatment arms.

Beyond host-pathogen interactions: microbial defense strategy in the host environment.

Many extracellular pathogenic bacteria colonize human or animal bodies through evasion of the host immune system, a process called host-pathogen interaction. What happens when other intruders try to invade the same host and try to establish themselves in the same niche is largely unknown. In one well-studied case, Pseudomonas aeruginosa is known to secrete the protein azurin as a weapon against such invaders as cancers, parasites and viruses. The production of such weapons by pathogenic bacteria could provide important insights into how a pathogen responds in the post-colonization state to impede other intruders for its own survival. Moreover, these molecules might find use in the pharmaceutical industry as next-generation therapeutics.

Role of microphthalmia transcription factor (Mitf) in melanoma differentiation.

We transfected the melanocyte-specific Mitf-M isoform into the aggressive melanoma UISO-Mel-6 cell lines. Our data show that Mitf decreases cell proliferation and results in cells which grow in clusters. By analyzing the expression of the markers of differentiation, we demonstrate that Mitf favored increased expression of tyrosinase and tyrosinase-related protein-1. In addition, Mitf induces Bcl-2 expression following transfection of UISO-Mel-6 cells. We also showed that Mitf gene affects cell-cycle distribution by resting cells preferentially in G2/G1 phase, and inducing the expression of p21 and p27. Moreover, we performed in vivo studies using subcutaneous injection of UISO-Mel-6 and UISO-Mel-6-Mitf in Balb/c nude mice. Our data show that Mitf inhibits tumor growth and decreases Ki67 expression. Tumors induced by UISO-Mel-6 cells were ulcerated and resulted in metastases to liver. None of the mice injected with UISO-Mel-6(Mitf+) cells harbored liver metastases. Our results suggest that Mitf is involved in melanoma differentiation and leads to a less aggressive phenotype.

Cupredoxin-cancer interrelationship: azurin binding with EphB2, interference in EphB2 tyrosine phosphorylation, and inhibition of cancer growth.

Azurin is a member of a family of metalloproteins called cupredoxins. Although previously thought to be involved in electron transfer, azurin has recently been shown to preferentially enter cancer cells than normal cells and induce apoptosis in such cells. Azurin also demonstrates structural similarity to a ligand known as ephrinB2, which binds its cognate receptor tyrosine kinase EphB2 to initiate cell signaling. Eph/ephrin signaling is known to be involved in cancer progression. We now demonstrate that azurin binds to the EphB2-Fc receptor with high affinity. We have localized a C-terminal domain of azurin (Azu 96-113) that exhibits structural similarity to ephrinB2 at the G-H loop region known to be involved in receptor binding. A synthetic peptide (Azu 96-113) as well as a GST fusion derivative GST-Azu 88-113 interferes with the growth of various human cancer cells. In a prostate cancer cell line DU145 lacking functional EphB2, azurin or its GST-fusion derivatives had little cytotoxic effect. However, in DU145 cells expressing functional EphB2, azurin and GST-Azu 88-113 demonstrated significant cytotoxicity, whereas ephrinB2 promoted cell growth. Azurin inhibited the ephrinB2-mediated autophosphorlyation of the EphB2 tyrosine residue, thus interfering in upstream cell signaling and contributing to cancer cell growth inhibition.

Bacterial proteins and CpG-rich extrachromosomal DNA in potential cancer therapy.

Bacterial proteins such as azurin and Laz have recently been shown to enter preferentially to cancer cells and kill them by multiple mechanisms. Historically, bacterial DNA, particularly the unmethylated CpG dinucleotides, have been shown to trigger activation of specific Toll-like receptors (TLRs) in immune cells, leading to various cytokine and chemokine production that allows cancer cell death and their regression. However, the enhanced release of specific protein or extrachromosomal DNA by bacteria in response to exposure to cancer cells has not been previously demonstrated. In this review, we discuss how an opportunistic, extracellular pathogenic bacterium, Pseudomonas aeruginosa, senses the presence of cancer cells and releases a specific protein or extrachromosomal DNA with antitumor activity for inhibition of cancer cell growth.