Proteomic identification of the oncoprotein STAT3 as a target of a novel Skp1 inhibitor.

Xin Cheng,Yong-Qiang Liu,Li-Wei Qu,Jinsong Liu,Guang-Biao Zhou,Xiao-Lu Wang,Xin-Chun Li,Bo Zhou,Yong-Zhi Lu,Gui-Zhen Wang,Yong-Xian Cheng,Sheng-Ce Tao,Li-Na Yang

doi:10.18632/oncotarget.13153

Abstract

The S phase kinase-associated protein 1 (Skp1), an adaptor protein of the Skp1-Cul1-F-box protein complex, binds the ubiquitin E3 ligase Skp2 and is critical to its biological functions. Targeting of Skp1 by a small compound 6-O-angeloylplenolin (6-OAP) results in dissociation and degradation of Skp2 and mitotic arrest of lung cancer cells. Here, by using a proteome microarray containing 16,368 proteins and a biotinylated 6-OAP, we identified 99 proteins that could bind 6-OAP, with Skp1 and STAT3 sitting at the central position of the 6-OAP interactome. 6-OAP formed hydrogen bonds with Ser611/Ser613/Arg609 at the SH2 domain of STAT3 and inhibited the constitutive and interleukin-6-induced phosphorylated STAT3 (pSTAT3), leading to inhibitory effects on lung cancer cells and suppression of Skp2 transcription. STAT3 was overexpressed in tumor samples compared to counterpart normal lung tissues and was inversely associated with prognosis of the patients. 6-OAP inhibited tumor growth in SCID mice intravenously injected with lung cancer cells, and downregulated both STAT3 and Skp2 in tumor samples. Given that 6-OAP is a Skp1 inhibitor, our data suggest that this compound may target Skp1 and STAT3 to suppress Skp2, augmenting its anti-lung cancer activity.

Highlights

Lung cancer is the malignant epithelial tumor arising from the respiratory mucosa with complex changes across the genome [1,2,3]
Signal transducer and activator of transcription 3 (STAT3) was overexpressed in tumor samples compared to counterpart normal lung tissues and was inversely associated with prognosis of the patients. 6-OAP inhibited tumor growth in SCID mice intravenously injected with lung cancer cells, and downregulated both STAT3 and Skp2 in tumor samples
Bio-6-OAP or biotin was probed on the human proteome microarray, and after free Bio6-OAP/biotin was removed, the microarray was further incubated with a Cy3 conjugated streptavidin (Cy3-SA) to present the Bio-6-OAP-protein interactions, and the specific binding between biotin and streptavidin was used for readout (Figure 1B)

Summary

Introduction

Lung cancer is the malignant epithelial tumor arising from the respiratory mucosa (bronchi, bronchioles, and alveoli) with complex changes across the genome [1,2,3]. It is the No 1 cancer killer worldwide with an only 15% of five-year overall survival rate for all stages combined [4]. Targeted therapies such as epidermal growth factor receptor (EGFR) inhibitors benefit a proportion of patients [5, 6]), but will eventually fail because of drug resistance resulting from secondary mutations (e.g., T790M) in EGFR or other mechanisms [7]. Arsenic trioxide which achieves a 5-year overall survival of more than 90% in acute promyelocytic leukemia when used in combination with retinoic acid, targets PML-RARα fusion protein, hexokinase-2, and binds 360 proteins [12, 13]

Methods

Results

Conclusion