Reduced Basal Nitric Oxide Production Induces Precancerous Mammary Lesions via ERBB2 and TGFβ

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, BH 4 , 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.

Correction of arginine metabolism with sepiapterin—the precursor of nitric oxide synthase cofactor BH4—induces immunostimulatory-shift of breast cancer

“…The declined basal NO production is due to reduced bioavailability of the NOS cofactor, BH 4 , under oxidative stress. Consistently, ectopic addition of the BH 4 precursor, sepiapterin, restores basal NO production and inhibits proliferation of breast cancer cells [ 39 ].…”

“…We recently reported that breast epithelial cells produce basal NO when cultivated in the basement membrane. Conversely, the production is impaired in cells undergoing the early-stage breast carcinogenesis, resulting in the upregulation of TGFβ and HER2 [ 37 – 39 ]. The declined basal NO production is due to reduced bioavailability of the NOS cofactor, BH 4 , under oxidative stress.…”

“…To examine the mechanism of NO-mediated PD-L1 regulation, we tested for the involvement of STAT3 and SMAD3, known positive regulators of PD-L1 [ 70 , 71 ]. Besides, STAT3 and SMAD3 are shown to be negatively regulated by NO [ 36 , 39 , 72 ]. To determine which transcription factor was involved in L-NAME-induced upregulation of PD-L1, we inhibited STAT3 (Stattic) or SMAD3 (SIS3) in breast cancer cells treated with L-NAME.…”

“…We previously reported that BH 4 bioavailability in breast epithelial cells declined during early-stage carcinogenesis, lowering basal NO production. Treating cultured breast cancer cells with sepiapterin not only normalized basal NO levels, but also suppressed cell proliferation [ 37 – 39 ].…”

The role of extracellular matrix in tumour angiogenesis: the throne has NOx servants

“…However, the mechanical reverting and the development of the same phenotypically healthy program observed by [ 92 ] was promoted in the case of SNAP. Furthermore, the culture of the breast cancer progression series premalignant AT1, malignant CA1d and DCIS cells, able to form ductal carcinoma in situ , in IrECM gel caused reduced production of NO and nitrite along with reduced levels of the cytosolic SNOC compared to MCF10A cells [ 128 ]. However, the levels of nNOS and eNOS remained high in all cell lines, with a reduction in the levels of iNOS; both nNOS and eNOS share equally in maintaining the basal NO levels in MCF10A cells.…”