Development of a Peptide-Based Nano-Sized Cathepsin B Inhibitor for Anticancer Therapy

Facile integration of a binary nano-prodrug with αPD-L1 as a translatable technology for potent immunotherapy of TNBC

Immune checkpoint blockers (ICBs)-based immunotherapy is a favorable approach for efficient triple-negative breast cancer (TNBC) treatment. However, the therapeutic efficacy of ICBs is greatly compromised by immunosuppressive tumor microenvironments (TMEs) and low expression levels of programmed cell death ligand-1 (PD-L1). Herein, we constructed an amphiphilic prodrug by linking a hydrophobic STING agonist, MSA-2 and a hydrophilic chemotherapeutic drug, gemcitabine (GEM) via an ester bond, which can self-assemble into GEM-MSA-2 (G-M) nanoparticles (NPs) with a tumor growth inhibition (TGI) value of 87.1 % in a murine 4T1 transplantation tumor model. Notably, the immunogenic cell death (ICD)-triggering effect of GEM together with the cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway activation properties of MSA-2 enables efficient infiltration of non-exhausting T cells and repolarization of macrophages from M2 to M1 types in the tumor microenvironment for transforming a cold tumor to a hot one. Most importantly, G-M NPs treatment increases the PD-L1 expression levels, thus providing a unique opportunity for further integration with anti-PD-L1 monoclonal antibody (αPD-L1) for eliciting stronger immunity that ultimately leads to a TGI value of 98.0 % in the primary tumor and significantly protects against distal and disseminated tumor rechallenge. Overall, this study presents a minimalist nano-prodrug combined with αPD-L1 as a simple yet robust translatable nanotechnology for potent chemo-immunotherapy of TNBC. STATEMENT OF SIGNIFICANCE: Enhancing the therapeutic efficacy of αPD-L1 for tumor immunotherapy via a translatable technology remains a challenge. We report herein facile integration of a binary nano-prodrug with αPD-L1 for potent immunotherapy of TNBC. An amphiphilic prodrug is constructed by linking a hydrophobic STING agonist, MSA-2 and a hydrophilic chemotherapeutic drug, gemcitabine (GEM) via an ester bond. The resulting self-assembled GEM-MSA-2 (G-M) nanoparticles (NPs) show a tumor growth inhibition (TGI) value of 87.1 % in a murine 4T1 transplantation tumor model. Besides the induced immunogenic cell death (ICD) and activated cGAS-STING pathway, G-M NPs increase the PD-L1 expression levels, providing a unique opportunity for further integration with αPD-L1 to elicit stronger immunity that ultimately leads to a TGI value of 98.0 % in the primary tumor and significantly protects against distal and disseminated tumor rechallenge.

Identification of a novel subtilisin-derived peptide, SC-(1-31), with cytotoxic activity

Subtilisins are alkaline serine proteases secreted by various species of Bacillus and can produce peptides by autolysis. A peptide from subtilisin NAT was found to disrupt the membrane of Streptococcus pneumoniae and to be cytotoxic only against tumor cell lines was found from subtilisin NAT. However, there has been little research on peptides derived from subtilisin Carlsberg, another famous subtilisin variant. In this research, we found another unique short peptide from subtilisin Carlsberg, which is produced by the fermentation of Bacillus licheniformis. This peptide had a molecular mass of 3225 Da and was identified as the N-terminal 31-amino acid residues of subtilisin Carlsberg, which has not been reported before. The peptide, named SC-(1-31), contains several cationic (pI = 9.83) and hydrophobic amino acid residues. It killed both cancer (Caco-2 and HeLa) and normal cell lines (WI-38) in concentration-dependent manners. The peptide was identified as a cytotoxic peptide based on its comparable toxicity towards cancer and normal cell lines. Liposome disruption assay suggested that this peptide may kill cells by disrupting the cell membrane.

Peptide-drug conjugates: A new paradigm for targeted cancer therapy

Peptide-drug conjugates (PDCs) are the new hope for targeted therapy after antibody-drug conjugates (ADCs). Compared with ADCs, the core advantages of PDCs are enhanced tissue penetration, easier chemical synthesis, and lower production costs. Two PDCs have been approved by the US Food and Drug Administration (FDA) for the treatment of cancer. The therapeutic effects of PDCs are remarkable, but PDCs also encounter problems when used as targeted therapeutics, such as poor stability, a short blood circulation time, a long research and development time frame, and a slow clinical development process. Therefore, it is very urgent and important to understand the latest research progress of cancer cells targeting PDC, the solution to its stability problem, the scheme of computer technology to assist its research and development, and the direction of its future development. In this manuscript, based on the structure and function of PDCs, the latest research progress on PDCs from the aspects of cancer cell-targeting peptide (CTP) selection, pharmacokinetic characteristics, stability regulation and so on were systematically reviewed, hoping to highlight the current problems and future development directions of PDCs.

Role of Cathepsin B Expression in Oral Squamous Cell Carcinoma: A Comprehensive Review

This comprehensive review delves into the intricate landscape of oral squamous cell carcinoma (OSCC) by examining the role of cathepsin B expression in its pathogenesis. OSCC, a prevalent and clinically significant oral malignancy, poses a considerable global health burden, necessitating a thorough exploration of its underlying molecular mechanisms. Cathepsin B, a lysosomal cysteine protease, emerges as a critical player in OSCC, influencing tumour initiation, invasion, and metastasis. The review begins with a brief overview of OSCC, emphasizing its epidemiological and clinical features, followed by exploring the significance of studying cathepsin B expression in this context. In the manuscript, the structure and function of cathepsin B are elucidated, providing a foundation for understanding its aberrant expression in OSCC. Clinical studies revealing correlations with tumour grade and stage, along with prognostic significance, are scrutinized, offering insights into the potential diagnostic and prognostic utility of cathepsin B. The biological functions of cathepsin B in OSCC, including its impact on tumour invasion and modulation of apoptosis, are comprehensively discussed. The Therapeutic Implications section explores targeting cathepsin B as a potential strategy, emphasizing the need for future research to overcome associated challenges. In the Conclusion section, the review synthesizes key findings, delineates implications for future research, and highlights the potential impact of cathepsin B on OSCC diagnosis and treatment, contributing to the ongoing efforts to advance our understanding of this complex malignancy, which is associated with a high mortality rate and improve clinical outcomes.

Smart Delivery Systems Responsive to Cathepsin B Activity for Cancer Treatment

Cathepsin B is a lysosomal cysteine protease, contributing to vital cellular homeostatic processes including protein turnover, macroautophagy of damaged organelles, antigen presentation, and in the extracellular space, it takes part in tissue remodeling, prohormone processing, and activation. However, aberrant overexpression of cathepsin B and its enzymatic activity is associated with different pathological conditions, including cancer. Cathepsin B overexpression in tumor tissues makes this enzyme an important target for smart delivery systems, responsive to the activity of this enzyme. The generation of technologies which therapeutic effect is activated as a result of cathepsin B cleavage provides an opportunity for tumor-targeted therapy and controlled drug release. In this review, we summarized different technologies designed to improve current cancer treatments responsive to the activity of this enzyme that were shown to play a key role in disease progression and response to the treatment.