Development of a Penetratin-Conjugated Stapled Peptide that Inhibits Wnt/β-Catenin Signaling

Paeoniflorigenone inhibits ovarian cancer metastasis through targeting the MUC1/Wnt/β‑catenin pathway

Ovarian cancer (OC) is one of the most common gynecological malignancies. Currently, chemoradiotherapy is the primary clinical treatment approach for OC; however, it has severe side effects and a high rate of recurrence. Thus, there is an urgent need to develop innovative therapeutic options. Paeoniflorigenone (PFG) is a monoterpene compound isolated from the traditional Chinese medicine Paeoniae Radix Rubra. PFG can inhibit the proliferation of tumor cells; however, its anticancer activity against OC has yet to be elucidated. Mucin 1 (MUC1) is highly expressed in various malignant tumors, and is associated with tumor proliferation, metastasis and epithelial‑mesenchymal transition (EMT). In addition, MUC1 affects numerous signaling pathways in tumor cells. In order to develop a possible treatment approach for metastatic OC, the antitumor activity of PFG in OC cells was investigated using Cell Counting Kit‑8 assay, Edu assay, flow cytometry, Transwell assay and western blot analysis. In addition, it was assessed how PFG affects MUC1 expression and function. The experiments revealed that PFG significantly inhibited OC cell proliferation, migration, invasion and EMT. PFG also induced S‑phase cell cycle arrest in OC cells. Furthermore, PFG inhibited MUC1 promoter activity, which led to a decrease in MUC1 protein expression. By contrast, MUC1 promoted OC progression, including cell proliferation, cell cycle progression and cell migration. Stable knockdown of MUC1 in OC cells improved the ability of PFG to block the Wnt/β‑catenin pathway, and to limit tumor cell invasion and migration, whereas MUC1 overexpression partially counteracted the antitumor effects of PFG. In conclusion, the present study demonstrated that PFG may inhibit the MUC1/Wnt/β‑catenin pathway to induce anti‑metastatic, anti‑invasive and anti‑EMT effects on OC. Notably, MUC1 may be a direct target of PFG. Thus, PFG holds promise as a specific antitumor agent for the treatment of OC.

Innovative peptide architectures: advancements in foldamers and stapled peptides for drug discovery

INTRODUCTION

Peptide foldamers play a critical role in pharmaceutical research and biomedical applications. This review highlights recent (post-2020) advancements in novel foldamers, synthetic techniques, and their applications in pharmaceutical research.

AREAS COVERED

The authors summarize the structures and applications of peptide foldamers such as α, β, γ-peptides, hydrocarbon-stapled peptides, urea-type foldamers, sulfonic-γ-amino acid foldamers, aromatic foldamers, and peptoids, which tackle the challenges of traditional peptide drugs. Regarding antimicrobial use, foldamers have shown progress in their potential against drug-resistant bacteria. In drug development, peptide foldamers have been used as drug delivery systems (DDS) and protein-protein interaction (PPI) inhibitors.

EXPERT OPINION

These structures exhibit resistance to enzymatic degradation, are promising for therapeutic delivery, and disrupt crucial PPIs associated with diseases such as cancer with specificity, versatility, and stability, which are useful therapeutic properties. However, the complexity and cost of their synthesis, along with the necessity for thorough safety and efficacy assessments, necessitate extensive research and cross-sector collaboration. Advances in synthesis methods, computational modeling, and targeted delivery systems are essential for fully realizing the therapeutic potential of foldamers and integrating them into mainstream medical treatments.

In silico optimization of peptides that inhibit Wnt/β-catenin signaling

The Wnt/β-catenin signaling pathway causes transcriptional activation through the interaction between β-catenin and T cell-specific transcription factor (TCF) and regulates a wide variety of cellular responses, including proliferation, differentiation and cell motility. Excessive transcriptional activation of the Wnt/β-catenin pathway is implicated in developing or exacerbating various cancers. We have recently reported that liver receptor homolog-1 (LRH-1)-derived peptides inhibit the β-catenin/TCF interaction. In addition, we developed a cell-penetrating peptide (CPP)-conjugated LRH-1-derived peptide that inhibits the growth of colon cancer cells and specifically inhibits the Wnt/β-catenin pathway. Nonetheless, the inhibitory activity of the CPP-conjugated LRH-1-derived peptide was unsatisfactory (ca. 20 μM), and improving the bioactivity of peptide inhibitors is required for their in vivo applications. In this study, we optimized the LRH-1-derived peptide using in silico design to enhance its activity further. The newly designed peptides showed binding affinity toward β-catenin comparable to the parent peptide. In addition, the CPP-conjugated stapled peptide, Penetratin-st6, showed excellent inhibition (ca. 5 μM). Thus, the combination of in silico design by MOE and MD calculations has revealed that logical molecular design of PPI inhibitory peptides targeting β-catenin is possible. This method can be also applied to the rational design of peptide-based inhibitors targeting other proteins.

Cell-Penetrating Peptides (CPPs) as Therapeutic and Diagnostic Agents for Cancer

Cell-Penetrating Peptides (CPPs) are short peptides consisting of <30 amino acids. Their ability to translocate through the cell membrane while carrying large cargo biomolecules has been the topic of pre-clinical and clinical trials. The ability to deliver cargo complexes through membranes yields potential for therapeutics and diagnostics for diseases such as cancer. Upon cellular entry, some CPPs have the ability to target specific organelles. CPP-based intracellular targeting strategies hold tremendous potential as they can improve efficacy and reduce toxicities and side effects. Further, recent clinical trials show a significant potential for future CPP-based cancer treatment. In this review, we summarize recent advances in CPPs based on systematic searches in PubMed, Embase, Web of Science, and Scopus databases until 30 September 2022. We highlight targeted delivery and explore the potential uses for CPPs as diagnostics, drug delivery, and intrinsic anti-cancer agents.