Estrogen markedly reduces circulating low-density neutrophils and enhances pro-tumoral gene expression in neutrophil of tumour-bearing mice

Abstract

Background Neutrophils are important for immune surveillance of tumour cells. Neutrophils may also be epigenetically programmed in the tumour microenvironment to promote tumour progression. In addition to the commonly known high-density neutrophils (HDN) based on their separation on density gradient, recent studies have reported the presence of high levels of low-density neutrophils (LDN) in tumour-bearing mice and cancer patients. We reported previously that estrogen promotes the growth of estrogen receptor α-negative mammary tumours in mice undergoing mammary involution through stimulating pro-tumoral activities of neutrophils in the mammary tissue. Methods Female BALB/cAnNTac mice at 7–8 weeks old were mated and bilateral ovariectomy was performed 2 days post-partum. At 24 h after forced-weaning of pups to induce mammary involution, post-partum female mice were injected with either E2V, or vehicle control on alternative days for 2-weeks. On 48 h post-weaning, treated female mice were inoculated subcutaneously with 4 T1-Luc2 cells into the 9th abdominal mammary gland. Age-matched nulliparous female was treated similarly. Animals were euthanized on day 14 post-tumour inoculation for analysis. To evaluate the short-term effect of estrogen, post-partum females were treated with only one dose of E2V on day 12 post-tumour inoculation. Results Estrogen treatment for 2-weeks reduces the number of blood LDN by more than 10-fold in tumour-bearing nulliparous and involuting mice, whilst it had no significant effect on blood HDN. The effect on tumour-bearing mice is associated with reduced number of mitotic neutrophils in the bone marrow and increased apoptosis in blood neutrophils. Since estrogen enhanced tumour growth in involuting mice, but not in nulliparous mice, we assessed the effect of estrogen on the gene expression associated with pro-tumoral activities of neutrophils. Whilst 48 h treatment with estrogen had no effect, 2-weeks treatment significantly increased the expression of Arg1, Il1b and Tgfb1 in both HDN and LDN of involuting mice. In contrast, estrogen increased the expression of Arg1 and Ccl5 in HDN and LDN of nulliparous mice. Conclusions Prolonged estrogenic stimulation in tumour-bearing mice markedly hampered tumour-associated increase of LDN plausibly by inhibiting their output from the bone marrow and by shortening their life span. Estrogen also alters the gene expression in neutrophils that is not seen in tumour-free mice. The results imply that estrogen may significantly influence the tumour-modulating activity of blood neutrophils.

The association between plasma chemokines and breast cancer risk and prognosis: A mendelian randomization study

“…Interestingly, we also found that many of the associations between chemokines and breast cancer or its survival were more pronounced in luminal A- or ER-positive cancers, suggesting that the effect of chemokines might be related to estrogen-related carcinogenesis ( Lim and Lin, 2021 ). However, we still found a potential causal association between CCL16 and triple-negative breast cancer.…”

Tumor-associated neutrophils are a negative prognostic factor in luminal breast cancers lacking immunosuppressive macrophage recruitment

“…They include immunosuppression as well as promotion of tumor growth, angiogenesis and distant metastasis, which is mediated via a CD90-TIMP-1 loop and the G-CSF-RLN2-MMP-9 axis in breast cancer [9,30,31]. Moreover, estrogen alters the activity and gene expression of neutrophils to contribute to tumor formation and growth [32,33]. Furthermore, TANs might also play a role in resistance to radiotherapy, which is a key element of breast-conserving treatment strategies in breast cancer [34].…”

Tumor Microenvironment as a Therapeutic Target in Melanoma Treatment

“…Consequently, TANs can remodel ECM and promote tumor invasion [ 190 , 203 ]. In addition to the production of proinflammatory cytokines/chemokines, TANs also produce immunosuppressive factors, including arginase 1 and TGF-β [ 204 ]. These immunosuppressive factors are mainly involved in the suppression of adaptive immunity [ 205 ] as well as in the release of HGF to promote tumor progression [ 206 ].…”