Reduced Basal Nitric Oxide Production Induces Precancerous Mammary Lesions via ERBB2 and TGF\u03b2

Gang Ren,Yashna Walia,Matthew Bommarito,Joshua Letson,Kam Yeung,Saori Furuta,Samantha Metzger,Christopher Figy,Andrea Kalinoski,Allen Schroering,Xunzhen Zheng,David Weaver

doi:10.1038/s41598-019-43239-x

Abstract

One third of newly diagnosed breast cancers in the US are early-stage lesions. The etiological understanding and treatment of these lesions have become major clinical challenges. Because breast cancer risk factors are often linked to aberrant nitric oxide (NO) production, we hypothesized that abnormal NO levels might contribute to the formation of early-stage breast lesions. We recently reported that the basal level of NO in the normal breast epithelia plays crucial roles in tissue homeostasis, whereas its reduction contributes to the malignant phenotype of cancer cells. Here, we show that the basal level of NO in breast cells plummets during cancer progression due to reduction of the NO synthase cofactor, BH4, under oxidative stress. Importantly, pharmacological deprivation of NO in prepubertal to pubertal animals stiffens the extracellular matrix and induces precancerous lesions in the mammary tissues. These lesions overexpress a fibrogenic cytokine, TGFβ, and an oncogene, ERBB2, accompanied by the occurrence of senescence and stem cell-like phenotype. Consistently, normalization of NO levels in precancerous and cancerous breast cells downmodulates TGFβ and ERBB2 and ameliorates their proliferative phenotype. This study sheds new light on the etiological basis of precancerous breast lesions and their potential prevention by manipulating the basal NO level.

Highlights

nitric oxide (NO) is produced by NO synthases 1–3 (NOS 1–3) using arginine as the substrate to exert pleiotropic functions
To support our hypothesis that aberrant NO production is involved in normal-to-precancerous progression of the breast epithelia, we have recently reported that non-malignant mammary epithelial cells (MECs) produce NO at the basal steady-state level upon interacting with the laminin-rich extracellular matrix (ECM)[24,53]
We previously demonstrated that non-malignant MECs produce the basal steady-state level of NO immediately after contacting laminin, but not collagen, in the extracellular matrix (ECM)[24]

Summary

Introduction

NO is produced by NO synthases 1–3 (NOS 1–3) using arginine as the substrate to exert pleiotropic functions. NO can exert dichotomous effects on diverse cellular processes including proliferation, apoptosis, migration, invasion and angiogenesis Such variations depend on NO’s concentration, context, timing, microenvironment, cancer type and stage[18,20,41,42,43]. To support our hypothesis that aberrant NO production is involved in normal-to-precancerous progression of the breast epithelia, we have recently reported that non-malignant mammary epithelial cells (MECs) produce NO at the basal steady-state level upon interacting with the laminin-rich extracellular matrix (ECM)[24,53]. Such NO production is critical for the establishment of mammary tissue architecture and homeostasis[24]. In the malignant counterpart derived from the same patient, NO production is defective, contributing to formation of proliferative, disorganized structures in 3D ECM cultures[24,53]

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