Investigation of Novel Regulation of N-myristoyltransferase by Mammalian Target of Rapamycin in Breast Cancer Cells

Marine Jacquier,Yang Zhang,Shiby Kuriakose,Apurva Bhardwaj,Shailly Varma Shrivastav,Stéphanie Portet,Anuraag Shrivastav

doi:10.1038/s41598-018-30447-0

Abstract

Breast cancer is the most common cancer in women worldwide. Hormone receptor breast cancers are the most common ones and, about 2 out of every 3 cases of breast cancer are estrogen receptor (ER) positive. Selective ER modulators, such as tamoxifen, are the first line of endocrine treatment of breast cancer. Despite the expression of hormone receptors some patients develop tamoxifen resistance and 50% present de novo tamoxifen resistance. Recently, we have demonstrated that activated mammalian target of rapamycin (mTOR) is positively associated with overall survival and recurrence free survival in ER positive breast cancer patients who were later treated with tamoxifen. Since altered expression of protein kinase B (PKB)/Akt in breast cancer cells affect N-myristoyltransferase 1 (NMT1) expression and activity, we investigated whether mTOR, a downstream target of PKB/Akt, regulates NMT1 in ER positive breast cancer cells (MCF7 cells). We inhibited mTOR by treating MCF7 cells with rapamycin and observed that the expression of NMT1 increased with rapamycin treatment over the period of time with a concomitant decrease in mTOR phosphorylation. We further employed mathematical modelling to investigate hitherto not known relationship of mTOR with NMT1. We report here for the first time a collection of models and data validating regulation of NMT1 by mTOR.

Highlights

MTOR is a serine/threonine kinase that regulates cell growth, proliferation, motility and survival[6]
We investigated the effects of rapamycin treatment on the expression of total N-myristoyltransferase 1 (NMT1) over time
Rapamycin treated MCF7 cells showed a decrease in the p-mammalian target of rapamycin (mTOR) (S2448) with a maximum decrease at 60′, whereas there was no significant change in the total mTOR levels under all experimental conditions (Fig. 1A and B) in comparison with either the control or the cells treated with the vehicle, DMSO

Summary

Introduction

MTOR is a serine/threonine kinase that regulates cell growth, proliferation, motility and survival[6]. We investigated the regulation of NMT1 by mTOR and further determined the impact of perturbations such as the effect of drugs by combining in vitro experiments and mathematical modelling approaches. We treated ER positive breast cancer cells with rapamycin and determined the effect of mTOR inhibition on NMT1 in a time dependent manner. We propose a collection of models of this regulation, including the inhibition of mTOR by rapamycin. The use of a collection of models allowed us to consider a variety of assumptions on the endogenous level of mTOR, the feedback regulation of mTOR by NMT1 and characteristics of the pathway when perturbed by rapamycin. Confronting models’ predictions to experimental data will help us determine key characteristics that are difficult to obtain experimentally, such as the relevance of the negative feedback of NMT1 on mTOR and the reversibility of the inhibition of mTOR by rapamycin

Methods

Results

Conclusion