Phosphoenolpyruvate Carboxykinase Maintains Glycolysis-driven Growth in Drosophila Tumors

Rashid Hussain,Zeeshan Shaukat,Stephen L Gregory,Robert Saint,Mahwish Khan

doi:10.1038/s41598-017-11613-2

Rashid Hussain, Zeeshan Shaukat + Show 3 more

Open Access

https://doi.org/10.1038/s41598-017-11613-2

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Journal: Scientific Reports	Publication Date: Sep 14, 2017
Citations: 9	License type: open-access

Affiliation: University of Adelaide, Flinders University

Abstract

Tumors frequently fail to pass on all their chromosomes correctly during cell division, and this chromosomal instability (CIN) causes irregular aneuploidy and oxidative stress in cancer cells. Our objective was to test knockdowns of metabolic enzymes in Drosophila to find interventions that could exploit the differences between normal and CIN cells to block CIN tumor growth without harming the host animal. We found that depleting by RNAi or feeding the host inhibitors against phosphoenolpyruvate carboxykinase (PEPCK) was able to block the growth of CIN tissue in a brat tumor explant model. Increasing NAD+ or oxidising cytoplasmic NADH was able to rescue the growth of PEPCK depleted tumors, suggesting a problem in clearing cytoplasmic NADH. Consistent with this, blocking the glycerol-3-phosphate shuttle blocked tumor growth, as well as lowering ROS levels. This work suggests that proliferating CIN cells are particularly vulnerable to inhibition of PEPCK, or its metabolic network, because of their compromised redox status.

Highlights

Having found metabolic targets that were able to kill proliferating cells with induced chromosomal instability (CIN), we wished to understand their mechanism of action in the context of a growing CIN tumour
Our results suggest that metabolic interventions that constrain clearance of NADH can generate toxic reactive oxygen species (ROS) levels in CIN tumours without harming the host
Dissection of third instar larval brains from control animals marked with RFP and transplanted in to a wild type adult host showed no growth (Fig. 1b), but depletion of Brat by RNAi resulted in strong growth of the RFP-tagged transplanted tissue (Fig. 1c) that would typically kill the host within two weeks

Summary

Introduction

Having found metabolic targets that were able to kill proliferating cells with induced CIN, we wished to understand their mechanism of action in the context of a growing CIN tumour. Oxygen species (ROS), was measured in labelled 3rd instar larval brains depleted for Brat (da > Gal[4]; UAS-RFP; UAS-brat-RNAi), and compared with subsequent serial passages of the explanted tissue (P1 to P3) or with tissue treated with an antioxidant (EGCG) or pro-oxidant (Mnd; Menadione) as controls. (g) The rate of chromosomal instability was measured in larval brains (da > Gal[4]; UAS-RFP; UAS-brat-RNAi) and subsequent passages of this explanted tissue. (h,i) Representative images of normal and defective anaphases from Brat depleted brain tissue (da > Gal[4]; UAS-RFP; UAS-brat-RNAi), quantitated in (g). Metabolic candidates in this model identified targets such as PEPCK that could effectively block tumour growth. Elevated levels of ROS were observed in the targeted tissue, and adding antioxidants could rescue growth. Our results suggest that metabolic interventions that constrain clearance of NADH can generate toxic ROS levels in CIN tumours without harming the host

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Results

Conclusion