Overexpression of peptide deformylase in breast, colon, and lung cancers

Harsharan Randhawa,Katie M Reindl,Shireen Chikara,Tuba Yildirim,Jyotsana Menon,Drew Gehring

doi:10.1186/1471-2407-13-321

Harsharan Randhawa, Katie M Reindl + Show 4 more

Open Access

https://doi.org/10.1186/1471-2407-13-321

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Abstract

BackgroundHuman mitochondrial peptide deformylase (PDF) has been proposed as a novel cancer therapeutic target. However, very little is known about its expression and regulation in human tissues. The purpose of this study was to characterize the expression pattern of PDF in cancerous tissues and to identify mechanisms that regulate its expression.MethodsThe mRNA expression levels of PDF and methionine aminopeptidase 1D (MAP1D), an enzyme involved in a related pathway with PDF, were determined using tissue panels containing cDNA from patients with various types of cancer (breast, colon, kidney, liver, lung, ovarian, prostate, or thyroid) and human cell lines. Protein levels of PDF were also determined in 2 colon cancer patients via western blotting. Colon cancer cells were treated with inhibitors of ERK, Akt, and mTOR signaling pathways and the resulting effects on PDF and MAP1D mRNA levels were determined by qPCR for colon and lung cancer cell lines. Finally, the effects of a PDF inhibitor, actinonin, on the proliferation of breast, colon, and prostate cell lines were determined using the CyQUANT assay.ResultsPDF and MAP1D mRNA levels were elevated in cancer cell lines compared to non-cancer lines. PDF mRNA levels were significantly increased in breast, colon, and lung cancer samples while MAP1D mRNA levels were increased in just colon cancers. The expression of PDF and MAP1D varied with stage in these cancers. Further, PDF protein expression was elevated in colon cancer tissue samples. Inhibition of the MEK/ERK, but not PI3K or mTOR, pathway reduced the expression of PDF and MAP1D in both colon and lung cancer cell lines. Further, inhibition of PDF with actinonin resulted in greater reduction of breast, colon, and prostate cancer cell proliferation than non-cancer cell lines.ConclusionsThis is the first report showing that PDF is over-expressed in breast, colon, and lung cancers, and the first evidence that the MEK/ERK pathway plays a role in regulating the expression of PDF and MAP1D. The over-expression of PDF in several cancers and the inhibition of cancer cell growth by a PDF inhibitor suggest this enzyme may act as an oncogene to promote cancer cell proliferation.

Highlights

Human mitochondrial peptide deformylase (PDF) has been proposed as a novel cancer therapeutic target
We report that PDF is elevated in breast, colon, and lung cancer tissues and methionine aminopeptidase 1D (MAP1D) is elevated in colon cancer tissue samples compared to non-cancer controls
PDF mRNA expression was significantly higher in the HT-29 colon, A549 lung, and PC-3 prostate cancer cell lines compared to the CCD-18Co colon, Hs888Lu lung, and PrEC prostate non-cancer cell lines (Figure 1)

Summary

Introduction

Human mitochondrial peptide deformylase (PDF) has been proposed as a novel cancer therapeutic target. The N-terminal methionine excision (NME) pathway is indispensible for proper protein functioning. This pathway involves two enzymes; peptide deformylase (PDF) which removes the formyl group from the initial methionine in nascent peptides, and methionine aminopeptidase (MAP) which subsequently removes the initial methionine [1]. Studies show that human PDF (HsPDF) can cleave the formyl group from an initiator methionine, but with reduced kinetics compared to the prokaryotic versions of the enzyme [2,8,9]. A recent report suggests that inhibition of PDF with actinonin results in reduced aerobic respiratory capacity by influencing the expression of proteins derived from the mtDNA [11]. These results have lead to recent studies focused on the design of inhibitors to target PDF in cancer [14,15,16]

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