Origin of anti-tumor activity of the cysteine-containing GO peptides and further optimization of their cytotoxic properties

Irina I Tyuryaeva,Olga G Lyublinskaya,Ivan S Podkorytov,Nikolai R Skrynnikov

doi:10.1038/srep40217

Irina I Tyuryaeva, Olga G Lyublinskaya + Show 2 more

Open Access

https://doi.org/10.1038/srep40217

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Abstract

Antitumor GO peptides have been designed as dimerization inhibitors of prominent oncoprotein mucin 1. In this study we demonstrate that activity of GO peptides is independent of the level of cellular expression of mucin 1. Furthermore, these peptides prove to be broadly cytotoxic, causing cell death also in normal cells such as dermal fibroblasts and endometrial mesenchymal stem cells. To explore molecular mechanism of their cytotoxicity, we have designed and tested a number of new peptide sequences containing the key CxC or CxxC motifs. Of note, these sequences bear no similarity to mucin 1 except that they also contain a pair of proximal cysteines. Several of the new peptides turned out to be significantly more potent than their GO prototypes. The results suggest that cytotoxicity of these peptides stems from their (moderate) activity as disulfide oxidoreductases. It is expected that such peptides, which we have termed DO peptides, are involved in disulfide-dithiol exchange reaction, resulting in formation of adventitious disulfide bridges in cell proteins. In turn, this leads to a partial loss of protein function and rapid onset of apoptosis. We anticipate that coupling DO sequences with tumor-homing transduction domains can create a potentially valuable new class of tumoricidal peptides.

Highlights

Acids, CQC, that proved to be responsible for the anti-tumor activity of GO-201
GO-202 showed the level of activity identical to GO-201 when applied to acute myeloid leukemia and lung adenocarcinoma cells[12,13]
We focus on GO-202 where the active sequence is synthesized from L-amino acids, allowing one to draw a connection to native protein sequences

Summary

Introduction

Acids, CQC, that proved to be responsible for the anti-tumor activity of GO-201. A control peptide CP-1 containing two alanine-for-cysteine substitutions, [R]9AQARRKNYGQLDIFP, showed no appreciable cytotoxic properties. The rationale was to further improve the proteolytic resistance of the peptide This variant, which was branded GO-203, showed high level of activity against non-small cell lung cancer, prostate cancer, acute myeloid leukemia, breast cancer, multiple myeloma, and other forms of cancer[14,15,16,17,18,19,20]. Phase I/II trials in patients with relapsed or refractory acute myeloid leukemia are currently underway and further trials are planned for patients with multiple myeloma (clinicaltrials.gov identifiers NCT02204085 and NCT02658396, respectively) In contemplating these results, we were intrigued by the fact that GO-203, which is comprised of all D-amino acids, displayed a high level of anti-tumor efficacy. Our main findings are summarized below: (i) GO peptides are broadly cytotoxic – they can be lethal to cancer cells, and to normal cells; (ii) The cytotoxic effect of GO peptides is unrelated to the expression of mucin – the cell line that strongly overexpresses MUC1 turns out to be less vulnerable to the effect of GO peptides, whereas other cell lines that show low-level MUC1 expression prove to be extremely sensitive; (iii) We designed several new cysteine-containing peptides which showed considerably stronger cytotoxic activity than the original GO peptides, while bearing no resemblance to MUC1

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Conclusion