Tumorigenesis is a complex and dynamic process, consisting of three stages: initiation, progression, and metastasis. Tumors are encircled by extracellular matrix (ECM) and stromal cells, and the physiological state of the tumor microenvironment (TME) is closely connected to every step of tumorigenesis. Evidence suggests that the vital components of the TME are fibroblasts and myofibroblasts, neuroendocrine cells, adipose cells, immune and inflammatory cells, the blood and lymphatic vascular networks, and ECM. This manuscript, based on the current studies of the TME, offers a more comprehensive overview of the primary functions of each component of the TME in cancer initiation, progression, and invasion. The manuscript also includes primary therapeutic targeting markers for each player, which may be helpful in treating tumors.

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Role of tumor microenvironment in tumorigenesis.

Prognostic factors are clinical and pathological features that give information in estimating the likely clinical outcome of an individual suffering from cancer. The author gives a short review of the most important prognostic factors in breast cancer. 376 breast cancer cases of a ten year interval in a county hospital are summarized. Traditional clinico-pathological parameters i.e. TNM and steroid receptor status are discussed. The more common karyotipic, oncogene and tumor suppressor gene alterations are outlined in the study. Methods for their detection are presented and their value in prognostication is reviewed. Emphasis was laid on steroid receptors, c-erpB-2, p53 and bcl-2 alterations. Genes responsible for heritable forms of increased breast cancer risk are briefly reviewed.

Prognostic factors in breast cancer

The tumor suppressor p53 has established functions in cancer. Specifically, it has been shown to cause cell-cycle arrest and apoptosis in response to DNA damage. It is also one of the most commonly mutated or silenced genes in cancer and for this reason has been extensively studied. Recently, the role of p53 has been shown to go beyond its effects on cell cycle and apoptosis, with effects on metabolism emerging as a key contributor to cancer growth in situations where p53 is lost. Beyond this, the role of p53 in the tumor microenvironment is poorly understood. The publication by Wang and colleagues demonstrates for the first time that p53 is a key negative regulator of aromatase and, hence, estrogen production in the breast tumor microenvironment. It goes further by demonstrating that an important regulator of aromatase, the obesity-associated and tumor-derived factor prostaglandin E2, inhibits p53 in the breast adipose stroma. This review presents these findings in the context of established and emerging roles of p53 and discusses possible implications for the treatment of breast cancer.

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p53: protection against tumor growth beyond effects on cell cycle and apoptosis

Arsenic induces pancreatic dysfunction and ferroptosis via mitochondrial ROS-autophagy-lysosomal pathway.

Obesity-related breast cancer is an important threat that affects especially post-menopausal women. The link between obesity and breast cancer seems to be relying on the microenvironment generated at adipose tissue level, which includes inflammatory cytokines. In addition, its association with systemic endocrine changes, including hyperinsulinemia, increased estrogens levels, and hyperleptinemia may be key factors for tumor development. These factors may promote tumor initiation, tumor primary growth, tissue invasion, and metastatic progression. Although the relationship between obesity and breast cancer is already established, the different pathophysiological mechanisms involved are not clear. Obesity-related insulin resistance is a well-known risk factor for breast cancer development in post-menopausal women. However, the role of inflammation and other adipokines, especially leptin, is less studied. Leptin, like insulin, appears to be a growth factor for breast cancer cells. There exists a link between leptin and metabolism of estrogens and between leptin and other factors in a more complex network. As a result, obesity-associated hyperleptinemia has been suggested as an important mediator in the pathophysiology of breast cancer. On the other hand, recent data on the paradoxical effect of obesity on cancer immunotherapy efficacy has brought some controversy, since the proinflammatory effect of leptin may help the effect of immune checkpoint inhibitors. Therefore, a better knowledge of the molecular mechanisms that mediate leptin action may be helpful to understand the underlying processes which link obesity to breast cancer in post-menopausal women, as well as the possible role of leptin in the response to immunotherapy in obese patients.

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Obesity and Breast Cancer: Role of Leptin.

Aromatase overexpression in dysfunctional adipose tissue links obesity to postmenopausal breast cancer.

Obesity is a risk factor for postmenopausal breast cancer and the majority of these cancers are estrogen dependent. Aromatase converts androgens into estrogens and its increased expression in breast adipose stromal cells (ASC) is a major driver of estrogen receptor-positive breast cancer. In particular, obesity-associated and tumor-derived factors, such as prostaglandin E2 (PGE2), have been shown to drive the expression of aromatase by stimulating the activity of the proximal promoter II (PII). The tumor-suppressor p53 is a key regulator of cell-cycle arrest and apoptosis and is frequently mutated in breast cancer. Mutations in p53 are rare in tumor-associated ASCs. Therefore, it was hypothesized that p53 is regulated by PGE2 and involved in the PGE2-mediated regulation of aromatase. Results demonstrate that PGE2 causes a significant decrease in p53 transcript and nuclear protein expression, as well as phosphorylation at Ser15 in primary human breast ASCs. Stabilization of p53 with RITA leads to a significant decrease in the PGE2-stimulated aromatase mRNA expression and activity, and PII activity. Interaction of p53 with PII was demonstrated and this interaction is decreased in the presence of PGE2. Moreover, mutation of the identified p53 response element leads to an increase in the basal activity of the promoter. Immunofluorescence on clinical samples demonstrates that p53 is decreased in tumor-associated ASCs compared with ASCs from normal breast tissue, and that there is a positive association between perinuclear (inactive) p53 and aromatase expression in these cells. Furthermore, aromatase expression is increased in breast ASCs from Li-Fraumeni patients (germline TP53 mutations) compared with non-Li-Fraumeni breast tissue. Overall, our results demonstrate that p53 is a negative regulator of aromatase in the breast and its inhibition by PGE2 provides a novel mechanism for aromatase regulation in obesity and breast cancer.

https://cancerres.aacrjournals.org/content/canres/75/4/645.full.pdf

Prostaglandin E2 inhibits p53 in human breast adipose stromal cells: a novel mechanism for the regulation of aromatase in obesity and breast cancer.

Aromatase converts androgens into estrogens and its expression within adipose stromal cells (ASCs) is believed to be the major driver of estrogen-dependent cancers in older women. Ghrelin is a gut-hormone that is involved in the regulation of appetite and known to bind to and activate the cognate ghrelin receptor, GHSR1a. The unacylated form of ghrelin, des-acyl ghrelin, binds weakly to GHSR1a but has been shown to play an important role in regulating a number of physiological processes. The aim of this study was to determine the effect of ghrelin and des-acyl ghrelin on aromatase in primary human ASCs. Primary human ASCs were isolated from adipose tissue of women undergoing cosmetic surgery. Real-time PCR and tritiated water-release assays were performed to examine the effect of treatment on aromatase transcript expression and aromatase activity, respectively. Treatments included ghrelin, des-acyl ghrelin, obestatin, and capromorelin (GHSR1a agonist). GHSR1a protein expression was assessed by Western blot and effects of treatment on Ca(2+) and cAMP second messenger systems were examined using the Flexstation assay and the Lance Ultra cAMP kit, respectively. Results demonstrate that pM concentrations of ghrelin and des-acyl ghrelin inhibit aromatase transcript expression and activity in ASCs under basal conditions and in PGE2-stimulated cells. Moreover, the effects of ghrelin and des-acyl ghrelin are mediated via effects on aromatase promoter PII-specific transcripts. Neither the GHSR1a-specific agonist capromorelin nor obestatin had any effect on aromatase transcript expression or activity. Moreover, GHSR1a protein was undetectable by Western blot and neither ghrelin nor capromorelin elicited a calcium response in ASCs. Finally, ghrelin caused a significant decrease in basal and forskolin-stimulated cAMP in ASC. These findings suggest that ghrelin acts at alternate receptors in ASCs by decreasing intracellular cAMP levels. Ghrelin mimetics may be useful in the treatment of estrogen-dependent breast cancer.

https://minerva-access.unimelb.edu.au/bitstream/handle/11343/59316/BCRT Ghrelin paper 120614.pdf

Ghrelin and des-acyl ghrelin inhibit aromatase expression and activity in human adipose stromal cells: suppression of cAMP as a possible mechanism

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Xuyi Wang

Papers

p53: protection against tumor growth beyond effects on cell cycle and apoptosis

Aromatase overexpression in dysfunctional adipose tissue links obesity to postmenopausal breast cancer.

Prostaglandin E2 inhibits p53 in human breast adipose stromal cells: a novel mechanism for the regulation of aromatase in obesity and breast cancer.

Ghrelin and des-acyl ghrelin inhibit aromatase expression and activity in human adipose stromal cells: suppression of cAMP as a possible mechanism

Erratum: p53: Protection against tumor growth beyond effects on cell cycle and apoptosis (Cancer Res (2015) 75 (5001-5007))