Albumin Nanoparticles Surface Decorated with a Tumor-Homing Peptide Help in Selective Killing of Triple-Negative Breast Cancer Cells

In this article, we describe a method of delivery of doxorubicin using a novel tumor-homing peptide-based albumin nanoparticle system to triple-negative breast cancer cells (TNBC). The absence and reduced expression of the hormone (estrogen, progesterone) and HER2 (human epidermal growth factor 2) receptors, respectively, render TNBC patients nonsusceptible to different available targeted therapies. These peptide-modified nanoparticles could be taken up by TNBC cells more effectively than their bare counterparts. The drug-loaded peptide-modified nanoparticles achieved an optimal but crucial balance between cell killing in cancerous cells and cell survival in the noncancerous ones. This appears to be because of different routes of entry and subsequent fate of the bare and peptide-modified nanoparticles in cancerous and noncancerous cells. In a TNBC mouse model, the peptide-modified system fared better than the free drug in mounting an antitumor response while not being toxic systemically.

StackTHPred: Identifying Tumor-Homing Peptides through GBDT-Based Feature Selection with Stacking Ensemble Architecture

One of the major challenges in cancer therapy lies in the limited targeting specificity exhibited by existing anti-cancer drugs. Tumor-homing peptides (THPs) have emerged as a promising solution to this issue, due to their capability to specifically bind to and accumulate in tumor tissues while minimally impacting healthy tissues. THPs are short oligopeptides that offer a superior biological safety profile, with minimal antigenicity, and faster incorporation rates into target cells/tissues. However, identifying THPs experimentally, using methods such as phage display or in vivo screening, is a complex, time-consuming task, hence the need for computational methods. In this study, we proposed StackTHPred, a novel machine learning-based framework that predicts THPs using optimal features and a stacking architecture. With an effective feature selection algorithm and three tree-based machine learning algorithms, StackTHPred has demonstrated advanced performance, surpassing existing THP prediction methods. It achieved an accuracy of 0.915 and a 0.831 Matthews Correlation Coefficient (MCC) score on the main dataset, and an accuracy of 0.883 and a 0.767 MCC score on the small dataset. StackTHPred also offers favorable interpretability, enabling researchers to better understand the intrinsic characteristics of THPs. Overall, StackTHPred is beneficial for both the exploration and identification of THPs and facilitates the development of innovative cancer therapies.

A Dual-Reporter Platform for Screening Tumor-Targeted Extracellular Vesicles

Extracellular vesicle (EV)-mediated transfer of biomolecules plays an essential role in intercellular communication and may improve targeted drug delivery. In the past decade, various approaches to EV surface modification for targeting specific cells or tissues have been proposed, including genetic engineering of parental cells or postproduction EV engineering. However, due to technical limitations, targeting moieties of engineered EVs have not been thoroughly characterized. Here, we report the bioluminescence resonance energy transfer (BRET) EV reporter, PalmReNL-based dual-reporter platform for characterizing the cellular uptake of tumor-homing peptide (THP)-engineered EVs, targeting PDL1, uPAR, or EGFR proteins expressed in MDA-MB-231 breast cancer cells, simultaneously by bioluminescence measurement and fluorescence microscopy. Bioluminescence analysis of cellular EV uptake revealed the highest binding efficiency of uPAR-targeted EVs, whereas PDL1-targeted EVs showed slower cellular uptake. EVs engineered with two known EGFR-binding peptides via lipid nanoprobes did not increase cellular uptake, indicating that designs of EGFR-binding peptide conjugation to the EV surface are critical for functional EV engineering. Fluorescence analysis of cellular EV uptake allowed us to track individual PalmReNL-EVs bearing THPs in recipient cells. These results demonstrate that the PalmReNL-based EV assay platform can be a foundation for high-throughput screening of tumor-targeted EVs.

SCMTHP: A New Approach for Identifying and Characterizing of Tumor-Homing Peptides Using Estimated Propensity Scores of Amino Acids

Tumor-homing peptides (THPs) are small peptides that can recognize and bind cancer cells specifically. To gain a better understanding of THPs’ functional mechanisms, the accurate identification and characterization of THPs is required. Although some computational methods for in silico THP identification have been proposed, a major drawback is their lack of model interpretability. In this study, we propose a new, simple and easily interpretable computational approach (called SCMTHP) for identifying and analyzing tumor-homing activities of peptides via the use of a scoring card method (SCM). To improve the predictability and interpretability of our predictor, we generated propensity scores of 20 amino acids as THPs. Finally, informative physicochemical properties were used for providing insights on characteristics giving rise to the bioactivity of THPs via the use of SCMTHP-derived propensity scores. Benchmarking experiments from independent test indicated that SCMTHP could achieve comparable performance to state-of-the-art method with accuracies of 0.827 and 0.798, respectively, when evaluated on two benchmark datasets consisting of Main and Small datasets. Furthermore, SCMTHP was found to outperform several well-known machine learning-based classifiers (e.g., decision tree, k-nearest neighbor, multi-layer perceptron, naive Bayes and partial least squares regression) as indicated by both 10-fold cross-validation and independent tests. Finally, the SCMTHP web server was established and made freely available online. SCMTHP is expected to be a useful tool for rapid and accurate identification of THPs and for providing better understanding on THP biophysical and biochemical properties.

Application of the Tumor Site Recognizable and Dual-Responsive Nanoparticles for Combinational Treatment of the Drug-Resistant Colorectal Cancer

PURPOSE

Combination of PCI and chemotherapy represents a promising strategy for combating drug resistance of cancer. However, poor solubility of photosensitizers and unselectively released drugs at unwanted sites significantly impaired the treatment efficacy. Therefore, in the present study, we aimed to develop a nano-platform which could efficiently co-entrapping photosensitizers and chemotherapeutics for active targeting therapy of drug resistant cancers.

METHODS

Two pro-drugs were respectively developed by covalently linking the Ce6 with each other via the GSH-sensitive linkage and the PTX with mPEG-PLA-COOH through the ROS sensitive-linker. The dual-responsive nanoparticles (PNP-Ce6) was developed by emulsion/solvent evaporation method and further modified with tLyp-1 peptides. Physicochemical properties of nanoparticles were determined by the TEM and DLC. Cellular uptake assay was investigated with the Ce6 acting as the fluorescent probe and cell growth was studied by the MTT experiment. In vivo tumor targeting and anti-tumor assay was investigated on the colorectal cancer-bearing mice.

RESULTS

The developed tPNP-Ce6 were stable enough under the normal physiological conditions. However, free Ce6 and PTX were completely released when exposed the tPNP-Ce6 to the redox environment. Excellent tumor-targeting drug delivery was achieved by the tPNP-Ce6, which in turn resulted in satisfactory anit-tumor effect. Of great importance, super inhibition effect on tumor progress was achieved by the combination therapy when compared with the group only received with chemotherapy..

CONCLUSION

The results obtained in the present study indicated that the developed tPNP-Ce6 may have great potential in enhancing the therapeutic efficacy of drug-resistant colorectal cancer. Graphical Abstract Left: Targeting delivery of drug to tumor site by the tumor recognizable and dual-responsive nanoparticles and penetrating into tumor inner via the mediation of irradiation. Right: Nanoparticle distribution within tumor tissues with green represents the blood vessels stained with CD31, blue signal represents the cell nuclei stained with DAPI and red shows fluorescence of Ce6 as the indicator of the nanoparticles.

Cancer-Cell-Specific Drug Delivery by a Tumor-Homing CPP-Gossypol Conjugate Employing a Tracelessly Cleavable Linker

Tumor-targeted drug delivery is highly important for improving chemotherapy, as it reduces the dose of cytotoxic agents and minimizes the death of healthy tissues. Towards this goal, a conjugate was synthesized of gossypol and a MCF-7 cancer cell specific CPP (cell penetrating peptide), thus providing a selective drug delivery system. Utilizing the aldehyde moiety of gossypol, the tumor homing CPP RLYMRYYSPTTRRYG was attached through a semi-labile imine linker, which was cleaved in a traceless fashion under aqueous conditions and had a half-life of approximately 10 hours. The conjugate killed MCF-7 cells to a significantly greater extent than HeLa cells or healthy fibroblasts.

Screening and characterization of a novel high-efficiency tumor-homing cell-penetrating peptide from the buffalo cathelicidin family

Targeted delivery of antitumor drugs is especially important for tumor therapy. Cell-penetrating peptides (CPPs) have been shown to be very effective drug carriers for tumor therapy. However, most CPPs lack tumor cell specificity. Here, we identified a highly efficient CPP, CAT, from the newly identified buffalo-derived cathelicidin family, which exhibits a preferential binding capacity for multiple tumor cell lines and delivers carried drug molecules into cells. CAT showed an approximately threefold to sixfold higher translocation efficiency than some reported cell-penetrating antimicrobial peptides, including the well-known classical CPP TAT. Moreover, the delivery efficiency of CAT was greater in a variety of tested tumor cells than in normal cells, especially for the human hepatoma cell line SMMC-7721, for which delivery was 7 times more efficient than the normal human embryonic lung cell line MRC-5, according to fluorescent labeling experiment results. CAT was conjugated to the Momordica charantia-derived type-I ribosome-inactivating protein MAP 30, and the cytotoxicity of the MAP 30-CAT fusion protein in the tumor cell line SMMC-7721 was significantly enhanced compared with that of the unconjugated MAP 30. The IC50 value of MAP 30-CAT was approximately 83 times lower than the IC50 value of the original MAP 30. Interestingly, the IC50 value of MAP 30 alone for MRC-5 was approximately twofold higher than the value for SMMC-7721, showing a small difference. However, when MAP 30 was conjugated to CAT, the difference in IC50 values between the two cell lines was significantly increased by 38-fold. The results of the flow cytometric detection of apoptosis revealed that the increase in cytotoxicity after CAT conjugation was mainly caused by the increased induction of apoptosis by the fusion protein. These results suggest that CAT, as a novel tumor-homing CPP, has great potential in drug delivery applications in vivo and will be beneficial to the development of tumor therapeutics.

Pacifastin-derived Peptides Target Tumors for Use in In Vivo Imaging

BACKGROUND/AIM

Developments in imaging have improved cancer diagnosis, but identification of malignant cells during surgical resection remains a challenge. The aim of this study was to investigate the pacifastin family of peptides for novel activity targeting tumor cells and the delivery of either imaging or therapeutic agents.

MATERIALS AND METHODS

Variants of pacifastin family peptides were generated, chemically modified and tested in human tumor xenografts.

RESULTS

A tumor-homing peptide-dye conjugate (THP1) accumulated in tumors in vivo and was internalized into cells. Examination of related peptides revealed residues critical for accumulation and allowed the engineering of improved tumor-targeting variants. A THP1-drug conjugate carrying the microtubule inhibitor, MMAE, showed limited activity in vitro and no difference compared to vehicle control in vivo.

CONCLUSION

Although there are some obstacles to developing pacifastin-derived peptides for therapeutic activity, these optimized peptides have great promise for cancer imaging.

Tumor-Homing and Penetrating Peptide-Functionalized Photosensitizer-Conjugated PEG-PLA Nanoparticles for Chemo-Photodynamic Combination Therapy of Drug-Resistant Cancer

The combination of photodynamic therapy (PDT) and chemotherapy holds great potential in combating drug-resistant cancers. However, the major challenge that lies ahead is how to achieve high coloading capacity for both photosensitizer and chemo-drugs and how to gain efficient delivery of drugs to the drug-resistant tumors. In this study, we prepared a nanovehicle for codelivery of photosensitizer (pyropheophorbide-a, PPa) and chemo-drugs (paclitaxel, PTX) based on the synthesis of PPa-conjugated amphiphilic copolymer PPa-PLA-PEG-PLA-PPa. The obtained nanoparticles (PP NP) exhibited a satisfactory high drug-loading capacity for both drugs. To achieve effective tumor-targeting therapy, the surface of PP NP was decorated with a tumor-homing and penetrating peptide F3. In vitro cellular experiments showed that F3-functionalized PP NP (F3-PP NP) exhibited higher cellular association than PP NP and resulted in the strongest antiproliferation effect. In addition, compared with the unmodified nanoparticles, F3-PP NP exhibited a more preferential enrichment at the tumor site. Pharmacodynamics evaluation in vivo demonstrated that a longer survival time was achieved by the tumor-bearing mice treated with PP NP (+laser) than those treated with chemotherapy only or PDT only. Such antitumor efficacy of combination therapy was further improved following the F3 peptide functionalization. Collectively, these results suggested that targeted combination therapy may pave a promising way for the therapy of drug-resistant tumor.

Multi-targeting Peptide-Functionalized Nanoparticles Recognized Vasculogenic Mimicry, Tumor Neovasculature, and Glioma Cells for Enhanced Anti-glioma Therapy

Chemotherapy failure of glioma, the most aggressive and devastating cancer, might be ascribed to the physiologic barriers of the tumor mainly including heterogeneous tumor perfusion and vascular permeability, which result in a limited penetration of chemotherapeutics. Besides, the vasculogenic mimicry (VM) channels, which are highly resistant to anti-angiogenic therapy and serve as a complement of angiogenesis, were abound in glioma and always associated with tumor recurrence. In order to enhance the therapy effect of anti-glioma, we developed a PEG-PLA-based nanodrug delivery system (nanoparticles, NP) in this study and modified its surface with CK peptide, which was composed of a human sonic hedgehog (SHH) targeting peptide (CVNHPAFAC) and a KDR targeting peptide (K237) through a GYG linker, for facilitating efficient VM channels, tumor neovasculature, and glioma cells multi-targeting delivery of paclitaxel. In vitro cellular assay showed that CK-NP-PTX not only exhibited the strongest antiproliferation effect on U87MG cells and HUVEC cells but also resulted in the most efficient destruction of VM channels when compared with CVNHPAFAC-NP, K237-NP, and the unmodified ones. Besides, CK-NP accumulated more selectively at the glioma site as demonstrated by in vivo and ex vivo imaging. As expected, the glioma-bearing mice treated with CK-NP-PTX achieved the longest median survival time compared to those treated with CVNHPAFAC-NP-PTX and K237-NP-PTX. These findings indicated that the multi-targeting therapy mediated by CK peptide might provide a promising way for glioblastoma therapy.

Specific tumor delivery of paclitaxel using glycolipid-like polymer micelles containing gold nanospheres

It is difficult for most of the drug delivery systems to really display a temporal and spatial release of entrapped drug once the systems are iv administrated. We hypothesized that the photothermal effect, mediated by a near-infrared (NIR) laser and hollow gold nanospheres (HAuNS), can modulate paclitaxel (PTX) release from polymer micelles, and further result in the enhanced antitumor activity of the micelles. We loaded PTX and HAuNS, which display strong plasmon absorption in the NIR region, into glycolipid-like polymer micelles with an excellent cell internalization capability. The surface of the micelles was conjugated successfully with a peptide, which has the specific-binding with EphB4, a member of the Eph family of receptor tyrosine kinases overexpressed on cell membrane of numerous tumors, to increase the delivery of PTX into tumor cells. Rapid and repetitive drug release from our polymer (HP-TCS) micelles could be readily achieved upon NIR laser irradiation. Our data demonstrated the specific delivery of HP-TCS micelles into positive-EphB4 tumors using a duel-tumor model after iv administration during the whole experiment process (1-48 h). Interestingly, significantly higher uptake of the micelles by SKOV3 tumors (positive-EphB4) than A549 tumors (negtive-EphB4) was observed, with increased ratio on experiment time. However, the specific cell uptake was observed only during the short incubation time (1-4 h) in vitro. Our data also indicated the treatment of tumor cells with the micelles followed by NIR laser irradiation showed significantly greater toxicity activity than the treatment with the micelles alone, free PTX and the micelles (without PTX loading) plus NIR laser irradiation. The enhanced toxicity activity to tumor cells should be attributed to the enhanced drug cellular uptake mediated by the glycolipid-like micelles, chemical toxicity of the released drug from the micelles due to the trigger of NIR laser, and the photothermal ablation under NIR laser irradiation.

Engineering strategy to improve peptide analogs: from structure-based computational design to tumor homing

We present a chemical strategy to engineer analogs of the tumor-homing peptide CREKA (Cys-Arg-Glu-Lys-Ala), which binds to fibrin and fibrin-associated clotted plasma proteins in tumor vessels (Simberg et al. in Proc Natl Acad Sci USA 104:932-936, 2007) with improved ability to inhibit tumor growth. Computer modeling using a combination of simulated annealing and molecular dynamics were carried out to design targeted replacements aimed at enhancing the stability of the bioactive conformation of CREKA. Because this conformation presents a pocket-like shape with the charged groups of Arg, Glu and Lys pointing outward, non-proteinogenic amino acids α-methyl and N-methyl derivatives of Arg, Glu and Lys were selected, rationally designed and incorporated into CREKA analogs. The stabilization of the bioactive conformation predicted by the modeling for the different CREKA analogs matched the tumor fluorescence results, with tumor accumulation increasing with stabilization. Here we report the modeling, synthetic procedures, and new biological assays used to test the efficacy and utility of the analogs. Combined, our results show how studies based on multi-disciplinary collaboration can converge and lead to useful biomedical advances.

Silk-based nanocomplexes with tumor-homing peptides for tumor-specific gene delivery

Nanoscale complexes of recombinant silk molecules containing THPs with DNA are designed as less cytotoxic and highly target-specific gene carriers. Genetically engineered silk proteins containing poly(L-lysine) domains to interact with pDNA and the THP to bind to specific tumorigenic cells for target-specific pDNA delivery are prepared, followed by in vitro transfection into MDA-MB-435 melanoma cells, highly metastatic human breast tumor MDA-MB-231 cells, and non-tumorigenic MCF-10A breast epithelial cells. The silk/poly(L-lysine) block copolymer containing Lyp1 (ML-Lyp1) shows significant differences from silk/poly(L-lysine) block copolymer containing F3 (ML-F3) in cytotoxicity to MCF10A cells. ML-F3 is the most promising candidate for target delivery into tumorigenic cells.