Targeted anticancer immunotoxins and cytotoxic agents with direct killing moieties

Targeted Therapy and Personalized Medicine

Targeted therapy and personalized medicine are novel emerging disciplines of cancer research intended for treatment and prevention. One of the most significant advancements in modern oncology is the shift from an organ-centric strategy to a personalized strategy guided by deep molecular analysis. This shift in view, which focuses on the tumour's precise molecular changes, has paved the way for individualized treatment. Researchers and clinicians are using targeted therapies to select the best treatment available based on the molecular characterization of malignant cancer. In the treatment of a cancer, personalized medicine entails the use of genetic, immunological, and proteomic profiling to provide therapeutic alternatives as well as prognostic information about cancer. In this book, targeted therapies and personalized medicine have been covered for specific malignancies, including latest FDA-approved targeted therapies and it also sheds light on effective anti-cancer regimens and drug resistance. This will help to enhance our ability to conduct individualized health planning, make early diagnoses, and choose optimal medications for each cancer patient with predictable side effects and outcomes in a quickly evolving era. Various applications and tools' capacity have been improved for early diagnosis of cancer and the growing number of clinical trials that choose specific molecular targets reflects this predicament. Nevertheless, there are several limitations that must need to be addressed. Hence, in this chapter, we will discuss recent advancements, challenges, and opportunities in personalized medicine for various cancers, with a specific emphasis on target therapies in diagnostics and therapeutics.

Emerging concepts in designing next-generation multifunctional nanomedicine for cancer treatment

Nanotherapy has emerged as an improved anticancer therapeutic strategy to circumvent the harmful side effects of chemotherapy. It has been proven to be beneficial to offer multiple advantages, including their capacity to carry different therapeutic agents, longer circulation time and increased therapeutic index with reduced toxicity. Over time, nanotherapy evolved in terms of their designing strategies like geometry, size, composition or chemistry to circumvent the biological barriers. Multifunctional nanoscale materials are widely used as molecular transporter for delivering therapeutics and imaging agents. Nanomedicine involving multi-component chemotherapeutic drug-based combination therapy has been found to be an improved promising approach to increase the efficacy of cancer treatment. Next-generation nanomedicine has also utilized and combined immunotherapy to increase its therapeutic efficacy. It helps in targeting tumor immune response sparing the healthy systemic immune function. In this review, we have summarized the progress of nanotechnology in terms of nanoparticle designing and targeting cancer. We have also discussed its further applications in combination therapy and cancer immunotherapy. Integrating patient-specific proteomics and biomarker based information and harnessing clinically safe nanotechnology, the development of precision nanomedicine could revolutionize the effective cancer therapy.

Modifications of Ribonucleases in Order to Enhance Cytotoxicity in Anticancer Therapy

Ribonucleases (RNases) are a superfamily of enzymes that have been extensively studied since the 1960s. For a long time, this group of secretory enzymes was studied as an important model for protein chemistry such as folding, stability and enzymatic catalysis. Since it was discovered that RNases displayed cytotoxic activity against several types of malignant cells, recent investigation has focused mainly on the biological functions and medical applications of engineered RNases. In this review, we describe structures, functions and mechanisms of antitumor activity of RNases. They operate at the crossroads of transcription and translation, preferentially degrading tRNA. As a result, this inhibits protein synthesis, induces apoptosis and causes death of cancer cells. This effect can be enhanced thousands of times when RNases are conjugated with monoclonal antibodies. Such combinations, called immunoRNases, have demonstrated selective antitumor activity against cancer cells both in vitro and in animal models. This review summarizes the current status of engineered RNases and immunoRNases as promising novel therapeutic agents for different types of cancer. Also, we describe our experimental results from published or previously unpublished research and compare with other scientific information.

Antineoplastic effect of a diphtheria toxin-based nanoparticle targeting acute myeloid leukemia cells overexpressing CXCR4

Nanomedicine has opened an opportunity to improve current clinical practice by enhancing the selectivity in the delivery of antitumor drugs to specific cancer cells. These new strategies are able to bypass toxicity on normal cells increasing the effectiveness of current anticancer treatments. In acute myeloid leukemia (AML) current chemotherapy treatments generate a relevant toxic impact in normal cells and severe side effects or even patient death. In this study, we have designed a self-assembling protein nanoparticle, T22-DITOX-H6, which incorporates a ligand (T22) targeting CXCR4-overexpressing (CXCR4⁺) cells, and a potent cytotoxic diphtheria toxin domain. CXCR4 is overexpressed in AML leukemic cells and associates with poor prognosis, being, therefore, a relevant clinical target. We demonstrate here that T22-DITOX-H6 induces apoptosis in CXCR4⁺ leukemic cells through CXCR4-dependent internalization. In addition, repeated T22-DITOX-H6 treatment (10 μg/dose per 10 doses, intravenously injected) in a disseminated AML mouse model (NSG mice intravenously injected with THP-1-Luci cells, n = 10 per group) potently blocks the dissemination of AML cells in bone marrow, spleen and liver of treated mice, without inducing toxicity in healthy tissues. In conclusion, our strategy of selectively ablating CXCR4 positive leukemic cells by administering the T22-DITOX-H6 nanoparticle could be a promising treatment, especially in patients undergoing AML relapse after chemotherapy, in which leukemic cells overexpress CXCR4.

Aptamer-Driven Toxin Gene Delivery in U87 Model Glioblastoma Cells

A novel suicide gene therapy approach was tested in U87 MG glioblastoma multiforme cells. A 26nt G-rich double-stranded DNA aptamer (AS1411) was integrated into a vector at the 5' of a mammalian codon-optimized saporin gene, under CMV promoter. With this plasmid termed "APTSAP", the gene encoding ribosome-inactivating protein saporin is driven intracellularly by the glioma-specific aptamer that binds to cell surface-exposed nucleolin and efficiently kills target cells, more effectively as a polyethyleneimine (PEI)-polyplex. Cells that do not expose nucleolin at the cell surface such as 3T3 cells, used as a control, remain unaffected. Suicide gene-induced cell killing was not observed when the inactive saporin mutant SAPKQ DNA was used in the (PEI)-polyplex, indicating that saporin catalytic activity mediates the cytotoxic effect. Rather than apoptosis, cell death has features resembling autophagic or methuosis-like mechanisms. These main findings support the proof-of-concept of using PEI-polyplexed APTSAP for local delivery in rat glioblastoma models.

Cytotoxic and apoptotic properties of a novel nano-toxin formulation based on biologically synthesized silver nanoparticle loaded with recombinant truncated pseudomonas exotoxin A

Bacterial toxins have received a great deal of attention in the development of antitumor agents. Currently, these protein toxins were used in the immunotoxins as a cancer therapy strategy. Despite the successful use of immunotoxins, immunotherapy strategies are still expensive and limited to hematologic malignancies. In the current study, for the first time, a nano-toxin comprised of truncated pseudomonas exotoxin (PE38) loaded silver nanoparticles (AgNPs) were prepared and their cytotoxicity effect was investigated on human breast cancer cells. The PE38 protein was cloned into pET28a and expressed in Escherichia coli, BL21 (DE3), and purified using metal affinity chromatography and was analyzed by 15% sodium dodecyl sulfate-polyacrylamide gel electrophoresis. AgNPs were biologically prepared using cell-free supernatant of E. Coli K12 strain. Nanoparticle formation was characterized by energy dispersive spectroscopy, transmission electron microscopy, and dynamic light scattering. The PE38 protein was loaded on AgNPs and prepared the PE38-AgNPs nano-toxin. Additionally, in vitro release indicated a partial slow release of toxin in about 100 hr. The nano-toxin exhibited dose-dependent cytotoxicity on MCF-7 cells. Also, real-time polymerase chain reaction results demonstrated the ability of nano-toxin to upregulate Bax/Bcl-2 ratio and caspase-3, -8, -9, and P53 apoptotic genes in the MCF-7 tumor cells. Apoptosis induction was determined by Annexin-V/propidium flow cytometry and caspases activity assay after treatment of cancer cells with the nano-toxin. In general, in the current study, the nano-toxin exhibit an inhibitory effect on the viability of breast cancer cells through apoptosis, which suggests that AgNPs could be used as a delivery system for targeting of toxins to cancer cells.

A Spectroscopic Study on Secondary Structure and Thermal Unfolding of the Plant Toxin Gelonin Confirms Some Typical Structural Characteristics and Unravels the Sequence of Thermal Unfolding Events

Gelonin from the Indian plant Gelonium multiflorum belongs to the type I ribosome-inactivating proteins (RIPs). Like other members of RIPs, this toxin glycoprotein inhibits protein synthesis of eukaryotic cells; hence, it is largely used in the construction of immunotoxins composed of cell-targeted antibodies. Lysosomal degradation is one of the main issues in targeted tumor therapies, especially for type I RIP-based toxins, as they lack the translocation domains. The result is an attenuated cytosolic delivery and a decrease of the antitumor efficacy of these plant-derived toxins; therefore, strategies to permit their release from endosomal vesicles or modifications of the toxins to make them resistant to degradation are necessary to improve their efficacy. Using infrared spectroscopy, we thoroughly analyzed both the secondary structure and the thermal unfolding of gelonin. Moreover, by the combination of two-dimensional correlation spectroscopy and phase diagram method, it was possible to deduce the sequence of events during the unfolding, confirming the typical characteristic of the RIP members to denature in two steps, as a sequential loss of tertiary and secondary structure was detected at 58 °C and at 65 °C, respectively. Additionally, some discrepancies in the unfolding process between gelonin and saporin-S6, another type I RIP protein, were detected.

Bacterial Proteinaceous Compounds With Multiple Activities Toward Cancers and Microbial Infection

In recent decades, cancer and multidrug resistance have become a worldwide problem, resulting in high morbidity and mortality. Some infectious agents like Streptococcus pneumoniae, Stomatococcus mucilaginous, Staphylococcus spp., E. coli. Klebsiella spp., Pseudomonas aeruginosa, Candida spp., Helicobacter pylori, hepatitis B and C, and human papillomaviruses (HPV) have been associated with the development of cancer. Chemotherapy, radiotherapy and antibiotics are the conventional treatment for cancer and infectious disease. This treatment causes damage in healthy cells and tissues, and usually triggers systemic side-effects, as well as drug resistance. Therefore, the search for new treatments is urgent, in order to improve efficacy and also reduce side-effects. Proteins and peptides originating from bacteria can thus be a promising alternative to conventional treatments used nowadays against cancer and infectious disease. These molecules have demonstrated specific activity against cancer cells and bacterial infection; indeed, proteins and peptides can be considered as future antimicrobial and anticancer drugs. In this context, this review will focus on the desirable characteristics of proteins and peptides from bacterial sources that demonstrated activity against microbial infections and cancer, as well as their efficacy in vitro and in vivo.

The Situation of Cancer Treatment in Ethiopia: Challenges and Opportunities

Background

Less attention is given to cancer treatment and control in Ethiopia.

Methods

To investigate the challenges and opportunities facing cancer treatment services in Ethiopia. A purposive sampling technique was applied to recruit the study subjects from Black Lion Specialized Hospital Oncology Department. A semi-structured interview guide was used to investigate challenges and opportunities in oncology service in Ethiopia. Data was transcribed and coded by two independent coders and analyzed thematically in reference to the objectives.

Results

Fifteen professionals from four different disciplines were interviewed on opportunities and challenges facing cancer treatment in Ethiopia. Out of these respondents 3 were senior clinical oncologists while 4 individuals were senior oncology residents. The rest were 2 medical Physicists, 2 radiotherapy technologists and 4 oncology nurses. Majority (80%) of the respondents were males. We demonstrate that the challenges of cancer treatment service in Ethiopia emanate from the patients themselves, the administrating body, the professionals, and the technology limitations. In general, the result of this study was grouped under the following five themes: Customer-related challenges, provider-related challenges, facility-related challenges, technology-related challenges and the opportunities.

Conclusions

Several assignments are waiting for the policy makers, the professionals, the communities and other concerned bodies to combat the alarmingly growing burden of cancer in Ethiopia. Escalating the awareness of the general population about cancer, expanding well-developed diagnostic and treatment centers, and producing well-trained competent oncology professionals are the forefront challenges in combating cancer in Ethiopia.

Design of a recombinant immunotoxin against the human granulocyte-colony stimulating factor receptor

Immunotoxin is a new strategy for protein therapy of cancer. This engineered protein contains two parts, the immune part which is an antibody or cytokine, directed against the cancer cell receptor, and the toxin part consisting of a plant or bacterial toxin leading to apoptosis by protein synthesis inhibition. The knowledge of cell-surface receptor overexpression in cancer cells can help scientists to construct new anti-cancer agents. The granulocyte colony stimulating factor (G-CSF) receptor is expressed on the cell surface of some blood cancers such as acute myeloid leukemia (AML). Therefore, this receptor can be used as an immunotoxin for treatment of some cancers. The aim of this work was to design and produce DT-GCSF immunotoxin using truncated DT fused to G-CSF. For fusion protein construction, DT389 and G-CSF fragments, were amplified by PCR using specific primers. A flexible linker SerGly4SerMet (SG4SM) was used to fuse the PCR products by SOEing PCR procedure to achieve an appropriate fusion protein, and the fused fragment was subcloned into pET21b. The new construction (pET-DT₃₈₉GCSF) was transformed into E. coli strain BL21 (DE3) and the expression of the construction was confirmed by SDS-PAGE and Western blotting techniques. The data demonstrated the expression and purity rates of DT₃₈₉GCSF about 25% and 90%, respectively. This chimeric protein construction can be used as a new anti-AML drug, but its in vitro and in vivo biological activity should be analyzed.

Bouganin, an Attractive Weapon for Immunotoxins

Bougainvillea (Bougainvillea spectabilis Willd.) is a plant widely used in folk medicine and many extracts from different tissues of this plant have been employed against several pathologies. The observation that leaf extracts of Bougainvillea possess antiviral properties led to the purification and characterization of a protein, named bouganin, which exhibits typical characteristics of type 1 ribosome-inactivating proteins (RIPs). Beyond that, bouganin has some peculiarities, such as a higher activity on DNA with respect to ribosomal RNA, low systemic toxicity, and immunological properties quite different than other RIPs. The sequencing of bouganin and the knowledge of its three-dimensional structure allowed to obtain a not immunogenic mutant of bouganin. These features make bouganin a very attractive tool as a component of immunotoxins (ITs), chimeric proteins obtained by linking a toxin to a carrier molecule. Bouganin-containing ITs showed very promising results in the experimental treatment of both hematological and solid tumors, and one bouganin-containing IT has entered Phase I clinical trial. In this review, we summarize the milestones of the research on bouganin such as bouganin chemico-physical characteristics, the structural properties and de-immunization studies. In addition, the in vitro and in vivo results obtained with bouganin-containing ITs are summarized.

Targeted therapy of human glioblastoma via delivery of a toxin through a peptide directed to cell surface nucleolin

Targeted anticancer therapies demand discovery of new cellular targets to be exploited for the delivery of toxic molecules and drugs. In this perspective, in the last few years, nucleolin has been identified as an interesting surface marker to be used for the therapy of glioblastoma. In this study, we investigated whether a synthetic antagonist of cell-surface nucleolin known as N6L, previously reported to decrease both tumor growth and tumor angiogenesis in several cancer cell lines, including glioblastoma cells, as well as endothelial cells proliferation, could be exploited to deliver a protein toxin (saporin) to glioblastoma cells. The pseudopeptide N6L cross-linked to saporin-S6 induced internalization of the toxin inside glioblastoma cancer cells. Our results in vitro demonstrated the effectiveness of this conjugate in inducing cell death, with an ID50 four orders of magnitude lower than that observed for free N6L. Furthermore, the preliminary in vivo study demonstrated efficiency in reducing the tumor mass in an orthotopic mouse model of glioblastoma.

Tumour endothelial marker 1/endosialin-mediated targeting of human sarcoma

BACKGROUND

Tumour endothelial marker 1 (TEM1/endosialin/CD248) is a tumour-restricted cell-surface protein expressed by human sarcomas. We previously developed a high-affinity human single-chain variable fragment (scFv)-Fc fusion protein (78Fc) against TEM1 and demonstrated its specific binding to human and mouse TEM1.

PATIENT AND METHODS

Clinical sarcoma specimens were collected between 2000 and 2015 at the Hospital of the University of Pennsylvania, as approved by the institutional review board and processed by standard formalin-fixed paraffin embedded techniques. We analysed TEM1 expression in 19 human sarcoma subtypes (n = 203 specimens) and eight human sarcoma-cell lines. Near-infrared (NIR) imaging of tumour-bearing mice was used to validate 78Fc binding to TEM1⁺ sarcoma in vivo. Finally, we tested an immunotoxin conjugate of anti-TEM1 78Fc with saporin (78Fc-Sap) for its therapeutic efficacy against human sarcoma in vitro and in vivo.

RESULTS

TEM1 expression was identified by immunohistochemistry in 96% of human sarcomas, of which 81% expressed TEM1 both on tumour cells and the tumour vasculature. NIR imaging revealed specific in vivo targeting of labelled 78Fc to TEM1⁺ sarcoma xenografts. Importantly, 78Fc-Sap was effective in killing in vitro TEM1⁺ sarcoma cells and eliminated human sarcoma xenografts without apparent toxicity in vivo.

CONCLUSION

TEM1 is an important therapeutic target for human sarcoma, and the high-affinity TEM1-specific scFv fusion protein 78Fc is suitable for further clinical development for therapeutic applications in sarcoma.

An overview of targeted cancer therapy

Cancer is a multifactorial disease and is one of the leading causes of death worldwide. The contributing factors include specific genetic background, chronic exposure to various environmental stresses and improper diet. All these risk factors lead to the accumulation of molecular changes or mutations in some important proteins in cells which contributes to the initiation of carcinogenesis. Chemotherapy is an effective treatment against cancer but undesirable chemotherapy reactions and the development of resistance to drugs which results in multi-drug resistance (MDR) are the major obstacles in cancer chemotherapy. Strategies which are in practice with limited success include alternative formulations e.g., liposomes, resistance modulation e.g., PSC833, antidotes/toxicity modifiers e.g., ICRF-187 and gene therapy. Targeted therapy is gaining importance due to its specificity towards cancer cells while sparing toxicity to off-target cells. The scope of this review involves the various strategies involved in targeted therapy like-monoclonal antibodies, prodrug, small molecule inhibitors and nano-particulate antibody conjugates.

Pseudomonas aeruginosa exotoxin T induces potent cytotoxicity against a variety of murine and human cancer cell lines

In patients with malignancy, the major barrier to achieving complete response is emergence of resistance to current chemotherapeutic agents. One of the major mechanisms by which tumour cells become resistant to therapies is by altering cellular drug targets through mutations and/or deletions. Resistance by this mechanism is achieved more easily if the drug has limited cellular targets and/or processes. We hypothesized that as Pseudomonas aeruginosa exotoxin T (ExoT) targets six proteins that are required for cancer cell survival and proliferation, it is highly unlikely for cancer cells to develop resistance to this toxin. We assessed ExoT's cytotoxicity against multiple invasive and highly resistant tumour cell lines in order to evaluate its potential as a chemotherapeutic agent. Our data demonstrated that ExoT induced potent cytotoxicity in all tumour cell lines that we examined. Collectively, our data highlighted the potential of ExoT as a possible chemotherapeutic candidate for the treatment of cancer.

Potential antitumor therapeutic application of Grimontia hollisae thermostable direct hemolysin mutants

We report on the preparation of a new type of immunotoxin by conjugation of an epidermal growth factor receptor (EGFR)-binding peptide and an R46E mutation of thermostable direct hemolysin from Grimontia hollisae, (Gh-TDH^R46E/EB). The hybrid immunotoxin was purified to homogeneity and showed a single band with slight slower mobility than that of Gh-TDH^R46E. Cytotoxicity assay of Gh-TDH^R46E/EB on EGFR highly, moderately, low, and non-expressed cells, A431, MDA-MB-231, HeLa, and HEK293 cells, respectively, showed apparent cytotoxicity on A431 and MDA-MB-231 cells but not on HeLa or HEK293 cells. In contrast, no cytotoxicity was observed for these cells treated with either Gh-TDH^R46E or EB alone, indicating enhanced cytotoxic efficacy of Gh-TDH^R46E by the EGFR binding moiety. Further antitumor activity assay of Gh-TDH^R46E/EB in a xenograft model of athymic nude mice showed obvious shrinkage of tumor size and degeneration, necrosis, and lesions of tumor tissues compared to the normal tissues. Therefore, the combination of Gh-TDH^R46E with target affinity agents opens new possibilities for pharmacological treatment of cancers and potentiates the anticancer drug's effect.

Saporin-S6: a useful tool in cancer therapy

Thirty years ago, the type 1 ribosome-inactivating protein (RIP) saporin-S6 (also known as saporin) was isolated from Saponaria officinalis L. seeds. Since then, the properties and mechanisms of action of saporin-S6 have been well characterized, and it has been widely employed in the construction of conjugates and immunotoxins for different purposes. These immunotoxins have shown many interesting results when used in cancer therapy, particularly in hematological tumors. The high enzymatic activity, stability and resistance to conjugation procedures and blood proteases make saporin-S6 a very useful tool in cancer therapy. High efficacy has been reported in clinical trials with saporin-S6-containing immunotoxins, at dosages that induced only mild and transient side effects, which were mainly fever, myalgias, hepatotoxicity, thrombocytopenia and vascular leak syndrome. Moreover, saporin-S6 triggers multiple cell death pathways, rendering impossible the selection of RIP-resistant mutants. In this review, some aspects of saporin-S6, such as the chemico-physical characteristics, the structural properties, its endocytosis, its intracellular routing and the pathogenetic mechanisms of the cell damage, are reported. In addition, the recent progress and developments of saporin-S6-containing immunotoxins in cancer immunotherapy are summarized, including in vitro and in vivo pre-clinical studies and clinical trials.

Orexin 2 receptor as a potential target for immunotoxin and antibody-drug conjugate cancer therapy

Targeting tumor-specific receptors is a promising approach for cytotoxic agents. The orexin 2 receptor (OX2R) has reportedly been expressed in a few types of cancer, but not in normal, cells. This study aimed to explore and assess the expression levels of OX2R in a wide range of cancer cell lines and clinical samples to identify its localization. To analyze OX2R expression, we developed a polyclonal antibody specific to OX2R by immunizing two rabbits with a peptide cocktail. A total of 36 cancer cell lines were employed for reverse transcription polymerase chain reaction (RT-PCR) and western blot analysis, and 221 samples from various tissue arrays were used for the immunohistochemistry of OX2R expression. OX2R was identified in three cancerous cell lines, from the gallbladder, squamous cell carcinoma of the head and neck (SCCHN) and glioblastoma. With clinical samples of tissue arrays, 69/221 (31.2%) samples reacted positively with the OX2R antibody. We confirmed its presence on the cell membrane. In conclusion, OX2R was identified on several cancer cells as well as clinical samples. Further studies with larger numbers of clinical samples are required to confirm the statistical significance of the presence and relationships of OX2R with tumor histology. Results of the current study suggested that OX2R is a potent target for immunotoxin or antibody-drug conjugate (ADC) cancer therapy on OX2R-positive cancer cells.

Targeting interleukin-4 receptor α with hybrid peptide for effective cancer therapy

Interleukin-4 receptor α (IL-4Rα) chain is highly expressed on the surface of various human solid tumors. We designed a novel hybrid peptide termed IL-4Rα-lytic peptide that targets the IL-4Rα chain. The IL-4Rα-lytic peptide contains a target moiety to bind to IL-4Rα and a cellular toxic lytic peptide that selectively kills cancer cells. The anticancer activity of the IL-4Rα-lytic peptide was evaluated in vitro and in vivo. It was found that the IL-4Rα-lytic peptide has cytotoxic activity in cancer cell lines expressing IL-4Rα, determined by quantitative real-time PCR. The IC(50) ratios of the lytic peptide to the IL-4Rα-lytic peptide correlated well with the expression levels of IL-4Rα on cancer cells (r = 0.80). In addition, IL-4Rα-lytic peptide administered either intratumoraly or intravenously significantly inhibited tumor growth in xenograft model of human pancreatic cancer (BXPC-3) in mice. These results indicate that the IL-4Rα-lytic peptide generated in this study has a potent and selective anticancer potential against IL-4Rα-positive solid cancers.

Semaphorin 3A lytic hybrid peptide binding to neuropilin-1 as a novel anti-cancer agent in pancreatic cancer

We previously reported that novel targeted "hybrid peptide" in which epidermal growth factor receptor (EGFR) binding peptide was conjugated with lytic-type peptide had selective cytotoxic activity to EGFR expressing cancer cells. In this study, we have generated a novel type hybrid peptide, semaphorin 3A lytic (Sema3A-lytic), which is composed of two functional amino acid domains: a sequence derived from Sema3A that binds to neuropilin-1 (NRP1) and a cytotoxic lytic peptide. We found that this hybrid peptide had cytotoxic activity against NRP1-positive pancreatic cancer cell lines such as BxPC-3 and Panc-1, whereas the peptide did not affect the viability of normal cells in vitro. It was also found by affinity analysis that Sema3A peptide binds to NRP1, and two arginines (372R and 377R) in Sema3A peptide are involved in the interaction with NRP1 protein. In addition, confocal microscopy analysis revealed that Sema3A-lytic peptide could not penetrate normal cells regardless of the presence of NRP1 mRNA, suggesting that the ability of Sema3A-lytic peptide to concentrate adjacent to the cell membrane by binding to NRP1 with the target-binding moiety contributes to its selective cytotoxic activity. These results indicate that Sema3A-lytic hybrid peptide would be a possible anti-cancer agent for treatment of human pancreatic cancer.

Antibody-targeted nanoparticles for cancer therapy

In recent years, nanoparticulate-mediated drug delivery research has examined a full spectrum of nanoparticles that can be used in diagnostic and therapeutic cancer applications. A key aspect of this technology is in the potential to specifically target the nanoparticles to diseased cells using a range of molecules, in particular antibodies. Antibody–nanoparticle conjugates have the potential to elicit effective targeting and release of therapeutic targets at the disease site, while minimizing off-target side effects caused by dosing of normal tissues. This article provides an overview of various antibody-conjugated nanoparticle strategies, focusing on the rationale of cell-surface receptors targeted and their potential clinical application.

Engineering a switchable toxin: the potential use of PDZ domains in the expression, targeting and activation of modified saporin variants

A critical problem in studying ribosome-inactivating proteins (RIPs) lies in the very limited possibility to produce them in heterologous systems. In fact, their inherent toxicity for the producing organism nearly always prevents their recombinant expression. In this study, we designed, expressed and characterized an engineered form of the RIP saporin (SapVSAV), bearing a C-terminal extra sequence that is recognized and bound by the second PDZ domain from murine PTP-BL protein (PDZ2). The co-expression of SapVSAV and PDZ2 in Escherichia coli BL21 cells greatly enhances the production of the toxin in a soluble form. The increase of production was surprisingly not due to protection from bacterial intoxication, but may arise from a stabilization effect of PDZ2 on the toxin molecule during biosynthesis. We found that once purified, SapVSAV is stable but is not toxic to free ribosomes, while it is fully active against human cancer cells. This strategy of co-expression of a toxin moiety and a soluble PDZ domain may represent a new system to increase the production of recombinant toxic proteins and could allow the selection of new extra sequences to target PDZ domains inside specific mammalian cellular domains.

Imaging and pharmacokinetics of (64)Cu-DOTA-HB22.7 administered by intravenous, intraperitoneal, or subcutaneous injection to mice bearing non-Hodgkin's lymphoma xenografts

PURPOSE

The aim of the study is to compare the tumor-specific targeting, pharmacokinetics, and biodistribution of (64)Cu-DOTA-HB22.7 when administered to xenograft-bearing mice intravenously (IV), intraperitoneally (IP), and subcutaneously (SQ).

PROCEDURES

Mice bearing human non-Hodgkin's lymphoma (NHL) xenografts were injected IV, IP, or SQ with (64)Cu-DOTA-HB22.7. Xenograft targeting was evaluated by micro positron emission tomography (microPET) and confirmed by organ biodistribution studies. Blood measurements of (64)Cu were performed to determine the pharmacokinetics and clearance of (64)Cu-DOTA-HB22.7.

RESULTS

(64)Cu-DOTA-HB22.7 demonstrated equivalent tumor targeting within 24-48 h, regardless of the route of administration. Organ biodistribution confirmed tumor-specific targeting. Blood pharmacokinetics demonstrated that (64)Cu-DOTA-HB22.7 accessed the bloodstream after IP and SQ administration to a similar degree as IV administration, albeit at a slower rate.

CONCLUSIONS

These findings establish (64)Cu-DOTA-HB22.7 as a potential radioimmunotherapeutic and/or NHL-specific imaging agent. These findings provide evidence that IP and SQ administration can achieve results equivalent to IV administration and may lead to more efficient, reproducible treatment plans for antibody-based therapeutics.

Nanotechnology and cancer

The biological picture of cancer is rapidly advancing from models built from phenomenological descriptions to network models derived from systems biology, which can capture the evolving pathophysiology of the disease at the molecular level. The translation of this (still academic) picture into a clinically relevant framework can be enabling for the war on cancer, but it is a scientific and technological challenge. In this review, we discuss emerging in vitro diagnostic technologies and therapeutic approaches that are being developed to handle this challenge. Our discussion of in vitro diagnostics is guided by the theme of making large numbers of measurements accurately, sensitively, and at very low cost. We discuss diagnostic approaches based on microfluidics and nanotechnology. We then review the current state of the art of nanoparticle-based therapeutics that have reached the clinic. The goal of the presentation is to identify nanotherapeutic strategies that are designed to increase efficacy while simultaneously minimizing the toxic side effects commonly associated with cancer chemotherapies.

Effect of DAB(389)IL-2 immunotoxin on the course of experimental autoimmune encephalomyelitis in Lewis rats

Activated T cells express the high affinity interleukin 2 receptor (IL-2R also CD25) that binds interleukin 2 (IL-2) and transduces signals important for the proliferation and survival of these cells. We investigated the effect of the genetically engineered immunotoxin DAB(389)IL-2 on experimental autoimmune encephalomyelitis (EAE), an autoimmune disease of the central nervous system (CNS) mediated by activated myelin-reactive T cells. EAE is the most commonly used animal model of the human disease multiple sclerosis (MS). DAB(389)IL-2 is a recombinant fusion product made of a portion of diphtheria toxin, which contains binding and translocation components of the toxin linked to IL-2. The diphtheria toxin targets and kills cells expressing the high affinity IL-2 receptor and has been successfully used in several autoimmune and neoplastic conditions. We observed a significant suppression of guinea-pig spinal cord homogenate (gpSCH)-MBP induced active EAE in Lewis rats at 2 x 1,600 kU of DAB(389)IL-2 given on days 7 and 9 post-immunization and complete suppression with the same dose on days 7, 8 and 9 or 7, 8, 9 and 10 after immunization during the active disease period. There were reduced mononuclear cell infiltrates of CD4(+), CD8(+), CD25(+) and alphabetaTCR(+) T cells in the spinal cord of treated rats. However, treatment at day 11 or 12 post-immunization led to severe, fatal disease. The toxin added to cultures in vitro or injected in vivo suppressed antigen- and mitogen-induced T cell proliferation. DAB(389)IL-2 treatment in vivo or exposure of encephalitogenic T cells in vitro prior to transfer did have a significant inhibitory effect on adoptive transfer EAE. Our data demonstrate that DAB(389)IL-2 immunotoxin can suppress active and passive EAE if applied at specific, early time points, but can have negative consequences at later time points.