Unbiased peptoid cell screen identifies a peptoid targeting newly appeared cell surface vimentin on tumor transformed early lung cancer cells

Linker optimization and activity validation of a cell surface vimentin targeted homo-dimeric peptoid antagonist for lung cancer stem cells

Epithelial-to-mesenchymal transition (EMT) endows epithelia-derived cancer cells with properties of stem cells that govern cancer invasion and metastasis. Vimentin is one of the best studied EMT markers and recent reports indicate that vimentin interestingly translocated onto cell surface under various tumor conditions. We recently reported a cell surface vimentin (CSV) specific peptoid antagonist named JM3A. We now investigated the selective antagonist activity of the optimized homo-dimeric version of JM3A, JM3A-L2D on stem-like cancer cells or cancer stem cells (CSCs) over normal cells in non-small cell lung cancer (NSCLC). Homo-dimerization of JM3A provided the avidity effect and improved the biological activity compared to the monomeric version. We first optimized the central linker length of the dimer by designing seven JM3A derivatives with varying linker lengths/types and evaluated the anti-cancer activity using the standard MTS cell viability assay. The most optimized derivative contains a central lysine linker and two glycines, named JM3A-L2D, which displayed 100 nM vimentin binding affinity (Kd) with an anti-cancer activity (IC50) of 6.7 µM on H1299 NSCLC cells. This is a 190-fold improvement in binding over the original JM3A. JM3A-L2D exhibited better potency on high vimentin-expressing NSCLC cells (H1299 and H460) compared to low vimentin-expressing NSCLC cells (H2122). No activity was observed on normal bronchial HBEC3-KT cells. The anti-CSC activity of JM3A-L2D was evaluated using the standard colony formation assay and JM3A-L2D disrupted the colony formation with IC50 ∼ 400 nM. In addition, JM3A-L2D inhibited cell migration activity at IC50 ∼ 2 µM, assessed via wound healing assay. The underlying mechanism of action seems to be the induction of apoptosis by JM3A-L2D on high-vimentin expressing H1229 and H460 NSCLC cells. Our optimized highly CSV selective peptoid has the potential to be developed as an anti-cancer drug candidate, especially considering the high serum stability and economical synthesis of peptoids.

Recent advances in anticancer peptoids

Since most tumors become resistant to drugs in a gradual and irreversible manner, making treatment less effective over time, anticancer drugs require continuous development. Peptoids are a class of peptidomimetics that can be easily synthesized and optimized. They exhibit a number of unique characteristics, including protease resistance, non-immunogenicity, do not interfere with peptide functionality and skeleton polarity, and can adopt different conformations. They have been studied for their efficacy in different cancer therapies, and can be considered as a promising alternative molecular category for the development of anticancer drugs. Herein, we discuss the extensive recent advances in peptoids and peptoid hybrids in the treatment of cancers such as prostate, breast, lung, and other ones, in the hope of providing a reference for the further development of peptoid anticancer drugs.

Pyrvinium Pamoate: Past, Present, and Future as an Anti-Cancer Drug

Pyrvinium, a lipophilic cation belonging to the cyanine dye family, has been used in the clinic as a safe and effective anthelminthic for over 70 years. Its structure, similar to some polyaminopyrimidines and mitochondrial-targeting peptoids, has been linked with mitochondrial localization and targeting. Over the past two decades, increasing evidence has emerged showing pyrvinium to be a strong anti-cancer molecule in various human cancers in vitro and in vivo. This efficacy against cancers has been attributed to diverse mechanisms of action, with the weight of evidence supporting the inhibition of mitochondrial function, the WNT pathway, and cancer stem cell renewal. Despite the overwhelming evidence demonstrating the efficacy of pyrvinium for the treatment of human cancers, pyrvinium has not yet been repurposed for the treatment of cancers. This review provides an in-depth analysis of the history of pyrvinium as a therapeutic, the rationale and data supporting its use as an anticancer agent, and the challenges associated with repurposing pyrvinium as an anti-cancer agent.

Optimization of a cell surface vimentin binding peptoid to extract antagonist effect on lung cancer cells

Targeting cytoskeletal proteins that are uniquely translocated to cancer cell surface may provide an alternative path for conventional drug discovery. Vimentin is such a cell surface-translocated cytoskeletal protein (CSV) found in non small cell lung cancer (NSCLC). We previously reported the identification of CSV-binding peptoid, named JM3A. While JM3A had no antagonist effect, here we used multiple strategies to optimize the binding of JM3A on CSV and extract the antagonistic effect. We first performed minimum pharmacophore identification studies using alanine/sarcosine scans. These studies revealed that residues 1-4 and 8 (from the C-terminus) are not important and those residues 5-7 are important for JM3A binding to CSV. We then found that our previous N-terminal benzophenone (BP)-coupled JM3A (JM3A-BP), which was used for pull-down and target identification studies, displayed 3-fold binding enhancement. The molecular docking studies indicated that the BP moiety binds to a new binding pocket on the vimentin coil 2 fragment, and further studies using 12 benzophenone-like moieties indicated that at least two phenyl groups are needed to occupy this new binding site. Interestingly, the binding was improved when non-important and bulky residues at the 4th and 8th positions were replaced with methyl groups (JM3A-4,8-BP). We next dimerized JM3A-4,8-BP to enhance the binding via the "avidity effect," using a central lysine linker to develop JM3A-4,8-BPD1 (EC50 = 300 nM). This showed 27- and 63-fold-improvement in binding over JM3A-4,8-BP and JM3A monomers, respectively. JM3A4,8BPD1 also displayed binding comparable to vimentin antibody. Finally, we observed an antagonist effect on H1299 NSCLC cell proliferation and viability from this most improved dimeric JM3A-4,8BPD1, which was not shown by the monomeric versions.

A peptoid interleukin‐15 receptor antagonist suppresses inflammation and arthritis in mice

Objective

To discover a novel peptoid antagonist that targets the interleukin‐15 (IL‐15) receptor and to evaluate its therapeutic efficacy in the treatment of inflammation and arthritis.

Methods

A new compound (IFRA3, interleukin‐15 receptor antagonist 3) was discovered using a unique on‐bead two‐colour combinatorial cell screening of a peptoid library. The interaction of IFRA3 with IL‐15 receptor was assessed by in vitro pull‐down and thermal shift assays. The efficacy of IFRA3 in treating inflammation and arthritis was evaluated in mouse models.

Results

IFRA3Q1 (a tetrameric derivative of IFRA3) inhibited the activity of IL‐15 and suppressed CTLL‐2 cell proliferation (which depends on IL‐15 activity). IFRA3Q1 exhibited strong in vivo anti‐inflammatory activity in carrageenan‐induced inflammation in mice. Furthermore, IFRA3Q1 inhibited collagen‐induced arthritis in DBA/1J mice.

Conclusion

By binding to and inhibiting the function of IL‐15 receptor, IFRA3Q1 exhibited significant anti‐arthritis activity. Our findings suggest that IFRA3Q1 represents a new paradigm for arthritis therapy by targeting IL‐15 signalling.