Proliferation of human mammary cancer cells exposed to 27-hydroxycholesterol

27-Hydroxycholesterol in cancer development and drug resistance

27-Hydroxycholesterol (27HC), a cholesterol metabolite, functions both as a selective oestrogen receptor (ER) modulator and a ligand for liver X receptors (LXRs). The discovery of 27HC involvement in carcinogenesis has unveiled new research avenues, yet its precise role remains controversial and context-dependent. In this review, we provide an overview of the biosynthesis and metabolism of 27HC and explore its cancer-associated signalling, with a particular focus on ER- and LXR-mediated pathways. Given the tissue-specific dual role of 27HC, we discuss its differential impact across various cancer types. Furthermore, we sort out 27HC-contributed drug resistance mechanisms from the perspectives of drug efflux, cellular proliferation, apoptosis, epithelial-mesenchymal transition (EMT), antioxidant defence, epigenetic modification, and metabolic reprogramming. Finally, we highlight the chemical inhibitors to mitigate 27HC-driven cancer progression and drug resistance. This review offers an updated role of 27HC in cancer biology, setting the stage for future research and the development of targeted therapeutics.

Circulating levels of biomarkers and risk of ductal carcinoma in situ of the breast in the UK Biobank study

Observational studies have shown associations between circulating levels of various biomarkers (eg, total cholesterol [TC], low-density lipoprotein cholesterol [LDL], insulin-like growth factor-1 [IGF-1], C-reactive protein [CRP] and glycated hemoglobin-1c [HbA1c]) and the risk of invasive breast cancer (IBC). Ductal carcinoma in situ of the breast (DCIS) is a nonobligate precursor of IBC and shares several risk factors with it. However, the relationship between these biomarkers and DCIS risk remains unexplored. We studied the association between circulating levels of TC, LDL-C, high-density lipoprotein cholesterol (HDL-C), Lipoprotein (a) (Lp-(a)), IGF-1, CRP and HbA1c, with the risk of DCIS in 156801women aged 40 to 69 years and breast cancer-free at enrolment when blood samples and information on demographic and health-related factors were collected. Incident cases of DCIS were ascertained during the follow-up via linkage to the UK cancer registries Multivariable-adjusted Cox proportional hazards models were used to estimate the hazard ratios (HRs) and 95% confidence intervals (CIs) for the associations of interest. In all, 969 DCIS incident cases were diagnosed during 11.4 years of follow-up. Total cholesterol was inversely associated with the risk of DCIS (HRquintile(Q)5vsQ1  = 0.47, 95% CI: 0.27-0.82, Ptrend  = .008). Conversely, LDL-C was positively associated with DCIS risk (HRQ3vsQ1  = 1.43, 95% CI: 1.01-2.04, HRQ4vsQ1  = 1.60, 95% CI: 1.04-2.47, HRQ5vsQ1  = 2.29, 95% CI: 1.36-3.88, Ptrend  = .004). In postmenopausal women, CRP had a weak positive association with DCIS risk, while HbA1c showed a nonlinear association with the risk. These results, in conjunction with those from previous studies on IBC, provide support for the association of several biomarkers with the risk of an early stage of breast cancer.

Examining the expression of low-density lipoprotein receptor (LDLR) and low-density lipoprotein receptor-related protein 6 (LRP6) genes in breast cancer cell lines

Cholesterol and the Wnt/β-catenin pathway have an effective role in the proliferation, survival, drug resistance, immune exhaustion, and metastasis of all types of cancer cells. Considering the role of LDLR and LRP6 proteins in cholesterol uptake by cells and activation of Wnt/β-catenin pathway, this study aims to examine the gene expression of LDLR and LRP6 in cell lines of breast cancer. Human breast cancer cell lines MCF7, MD468 and SKBR3 were cultured in suitable conditions and after extracting total RNA from them, real-Time PCR was used to measure the levels of gene expression for LDLR and LRP6. Our results showed that the expression of LDLR and LRP6 genes is significantly increased in MCF7 and MD468 cells compared to SKBR3 cells. These results suggest that LRP6 and LDLR can be considered as a therapeutic target in tumors that have a genetic profile similar to MCF7 and MD468 cells.

Low-density lipoprotein receptor promotes crosstalk between cell stemness and tumor immune microenvironment in breast cancer: a large data-based multi-omics study

BACKGROUND

Tumor cells with stemness in breast cancer might facilitate the immune microenvironment's suppression process and led to anti-tumor immune effects. The primary objective of this study was to identify potential targets to disrupt the communication between cancer cell stemness and the immune microenvironment.

METHODS

In this study, we initially isolated tumor cells with varying degrees of stemness using a spheroid formation assay. Subsequently, we employed RNA-seq and proteomic analyses to identify genes associated with stemness through gene trend analysis. These stemness-related genes were then subjected to pan-cancer analysis to elucidate their functional roles in a broader spectrum of cancer types. RNA-seq data of 3132 patients with breast cancer with clinical data were obtained from public databases. Using the identified stemness genes, we constructed two distinct stemness subtypes, denoted as C1 and C2. We subsequently conducted a comprehensive analysis of the differences between these subtypes using pathway enrichment methodology and immune infiltration algorithms. Furthermore, we identified key immune-related stemness genes by employing lasso regression analysis and a Cox survival regression model. We conducted in vitro experiments to ascertain the regulatory impact of the key gene on cell stemness. Additionally, we utilized immune infiltration analysis and pan-cancer analysis to delineate the functions attributed to this key gene. Lastly, single-cell RNA sequencing (scRNA-seq) was employed to conduct a more comprehensive examination of the key gene's role within the microenvironment.

RESULTS

In our study, we initially identified a set of 65 stemness-related genes in breast cancer cells displaying varying stemness capabilities. Subsequently, through survival analysis, we pinpointed 41 of these stemness genes that held prognostic significance. We observed that the C2 subtype exhibited a higher stemness capacity compared to the C1 subtype and displayed a more aggressive malignancy profile. Further analysis using Lasso-Cox algorithm identified LDLR as a pivotal immune-related stemness gene. It became evident that LDLR played a crucial role in shaping the immune microenvironment. In vitro experiments demonstrated that LDLR regulated the cell stemness of breast cancer. Immune infiltration analysis and pan-cancer analysis determined that LDLR inhibited the proliferation of immune cells and might promote tumor cell progression. Lastly, in our scRNA-seq analysis, we discovered that LDLR exhibited associations with stemness marker genes within breast cancer tissues. Moreover, LDLR demonstrated higher expression levels in tumor cells compared to immune cells, further emphasizing its relevance in the context of breast cancer.

CONCLUSION

LDLR is an important immune stemness gene that regulates cell stemness and enhances the crosstalk between breast cancer cancer cell stemness and tumor immune microenvironment.

The Cytotoxicity of 27-Hydroxycholesterol in MCF-7 and MDA-MB-231

BACKGROUND

Although several roles of 27-hydroxycholesterol (27-HC), the most abundant oxysterol in blood circulation, in cancers have been elucidated, its impact on breast cancer proliferation and its pathway remain unknown.

MATERIALS AND METHODS

The effect of 27-HC on breast cancer cell proliferation and its pathway was evaluated using Michigan Cancer Foundation - 7 (MCF-7) and M.D. Anderson - Metastatic Breast 231 (MDA-MB-231) cell lines. The MTT assay was applied after 24- and 48-hour incubation to distinguish cell proliferation. To determine the cause of different viability results from the MTT assay, the Annexin-FITC/PI test was used at concentrations of 0.1, 1, and 10 μM after 24- and 48-hour incubation.

RESULTS

27-HC in concentrations of 5, 10, and 20 μM induced cell cytotoxicity compared with control. Also, the annexin V conjugated with fluorescein isothiocyanate/propidium iodide (Annexin-FITC/PI) test revealed an increase in total apoptotic cells treated with 0.1, 1, and 10 μM of 27-HC after 48 hours (P value < 0.05). Besides, the cytotoxic effect of 27-HC was observed at 10 μM concentration in both cell lines, MCF-7 and MDA-MB-231 (P value < 0.05).

CONCLUSION

The identification of 27-HC's cytotoxic effects on both estrogen receptor (ER)-negative and ER-positive breast cancer cell lines is a novel discovery that may be linked to LXRβ.

The impact of lipid metabolism on breast cancer: a review about its role in tumorigenesis and immune escape

BACKGROUND

Breast cancer (BC) is the second most frequent type of cancer in the world and most common among women, configuring a major challenge to global health. BC is a complex and heterogeneous disease that can be subdivided into distinct tumor types based on the expression of molecular markers predicting patient outcomes and response to therapy. A growing number of studies have tried to expand the known markers by investigating the association of altered lipid metabolism with BC immune escape, progression, and metastasis. In this review, we describe the metabolic peculiarities of each BC subtype, understanding how this influences its aggressiveness and identifying whether these intrinsic vulnerabilities of each subtype can play a role in therapeutic management and may affect immune system cells in the tumor microenvironment.

CONCLUSION

The evidence suggests so far that when changes occur in lipid pathways, it can affect the availability of structural lipids for membrane synthesis, lipid synthesis, and degradation that contribute to energy homeostasis and cell signaling functions. These findings will guide the next steps on the path to understanding the mechanisms underlying how lipids alterations are related to disparities in chemotherapeutic response and immune escape in BC. Video Abstract.

The evolving landscape of PCSK9 inhibition in cancer

Cancer is a disease with a significant global burden in terms of premature mortality, loss of productivity, healthcare expenditures, and impact on mental health. Recent decades have seen numerous advances in cancer research and treatment options. Recently, a new role of cholesterol-lowering PCSK9 inhibitor therapy has come to light in the context of cancer. PCSK9 is an enzyme that induces the degradation of low-density lipoprotein receptors (LDLRs), which are responsible for clearing cholesterol from the serum. Thus, PCSK9 inhibition is currently used to treat hypercholesterolemia, as it can upregulate LDLRs and enable cholesterol reduction through these receptors. The cholesterol-lowering effects of PCSK9 inhibitors have been suggested as a potential mechanism to combat cancer, as cancer cells have been found to increasingly rely on cholesterol for their growth needs. Additionally, PCSK9 inhibition has demonstrated the potential to induce cancer cell apoptosis through several pathways, increase the efficacy of a class of existing anticancer therapies, and boost the host immune response to cancer. A role in managing cancer- or cancer treatment-related development of dyslipidemia and life-threatening sepsis has also been suggested. This review examines the current evidence regarding the effects of PCSK9 inhibition in the context of different cancers and cancer-associated complications.

Prevalence and Associated Predictors of Hypertension in Adult Patients with Thyroid Nodules at the Royal Commission Hospital, Kingdom of Saudi Arabia

Background

Hypertension and thyroid nodules (TNs) are common medical problems that are increasing in prevalence globally. Hence, we conducted this study to assess the prevalence and associated predictors of hypertension in adult patients with TNs at the Royal Commission Hospital, Kingdom of Saudi Arabia (KSA).

Methods

A retrospective study was conducted between 1 January 2015 and 31 December 2021. Patients with documented TNs based on the Thyroid Imaging Reporting and Data System (TI-RADS) were recruited to assess the prevalence and associated risk factors for hypertension.

Result

Three hundred ninety-one patients with TNs were recruited for this study. The median (interquartile range, IQR) age was 46.00 (20.0) years, and 332 (84.9%) of the patients were females. The median (IQR) body mass index (BMI) was 30.26 (7.71) kg/m². There was a high prevalence of hypertension (22.5%) in adult patients with TNs. In the univariate analysis, there were significant associations between diagnosed hypertension in patients with TNs and age, sex, diabetes mellitus (DM), bronchial asthma, triiodothyronine (FT3), total cholesterol and high-density lipoprotein (HDL). In the multivariate analysis, age (OR = 1.076 [95% CI 1.048 - 1.105]), sex (OR = 2.28 [95% CI 1.132 - 4.591]), DM (OR = 0.316 [95% CI 0.175 - 0.573]) and total cholesterol levels (OR = 0.820 [95% CI 0.694 - 0.969]) were significantly associated with hypertension.

Conclusion

There is a high prevalence of hypertension in patients with TNs. Age, female sex, DM and elevated total cholesterol are significant predictors of hypertension in adult patients with TNs.

CYP27A1 inhibits proliferation and migration of clear cell renal cell carcinoma via activation of LXRs/ABCA1

Cholesterol homeostasis plays an important role in the maintenance of normal body functions. CYP27A1 is a key enzyme known to regulate cholesterol homeostasis, which catalyzes the conversion of cholesterol to 27-HC and has been implicated in the occurrence and metastasis of various cancer types. The present study aimed to explore the regulatory role of CYP27A1 in the development of clear cell renal cell carcinoma (ccRCC). In particular, the effect of CYP27A1 on the proliferation and migration of ccRCC cells was investigated. The construction of a stable 786-O cell line overexpressing CYP27A1/pLVX was mediated by lentiviral infection. The proliferative capacity was assessed using MTT and colony formation. Wound healing assay was used to measure cell migration. Production of intracellular cholesterol and 27-HC was detected by enzyme-linked immunosorbent assay. The LXRs/ABCA1 pathway of cholesterol metabolism regulation was studied by RT-qPCR and Western blotting analysis after cells were treated with stimulation agents of 27-HC or T0901317 and inhibition agents of siRNA or GSK2033. The results revealed that overexpression of CYP27A1 could increase the intracellular production of 27-HC and inhibit the proliferation and migration of 786-O cells. And the treatment of 786-O cells with 27-HC induced a similar effect. CYP27A1/27HC mediated activation of the liver X receptors (LXRs) could up-regulate the expression of ATP-binding cassette transporter A1 (ABCA1), further resulting in the reduction of intracellular cholesterol contents. All of these findings indicated a regulatory role of CYP27A1 in the proliferation and migration of ccRCC, via activating LXRs/ABCA1 to regulate cholesterol homeostasis.

A Role for ER-Beta in the Effects of Low-Density Lipoprotein Cholesterol and 27-Hydroxycholesterol on Breast Cancer Progression: Involvement of the IGF Signalling Pathway?

Cholesterol-in particular, high levels of low-density lipoprotein (LDL) and its metabolite, 27-hydroxycholesterol (27-OHC)-is correlated with increases in the risks of breast cancer and obesity. Although the high expression of LDL/27-OHC has been reported in breast cancer, its effects and mechanism of action remain to be fully elucidated. In this study, we found that the effects of LDL on cell proliferation were mediated by the activation of the cytochrome P450 enzyme, sterol 27 hydroxylase, and cholesterol 27-hydroxylase (CYP27A1) in both ER-α-positive and ER-α-negative breast cancer cells. We found that treatment with 27-OHC only increased cell growth in oestrogen receptor-α (ER-α)-positive breast cancer cells in an ER-α-dependent manner, but, interestingly, the effects of 27-OHC on cell migration and invasion were independent of ER-α. Using ER-α-negative MDA-MB-231 cells, we found that 27-OHC similarly promoted cell invasion and migration, and this was mediated by oestrogen receptor β (ER-β). These results suggest that 27-OHC promotes breast cancer cell proliferation in ER-α-positive breast cancer cells via ER-α, but migration and invasion are mediated via ER-β in ER-α positive and negative cell lines. The addition of LDL/27OHC increased the production of IGF-I and the abundance of IGF-IR in TNBC. We further found that modulating ER-β using an agonist or antagonist increased or decreased, respectively, levels of the IGF-I and EGF receptors in TNBC. The inhibition of the insulin-like growth factor receptor blocked the effects of cholesterol on cell growth and the migration of TNBC. Using TCGA and METABRIC microarray expression data from invasive breast cancer carcinomas, we also observed that higher levels of ER-beta were associated with higher levels of IGF-IR. Thus, this study shows novel evidence that ER-β is central to the effects of LDL/27OHC on invasion, migration, and the IGF and EGF axes. Our data suggest that targeting ER-β in TNBC could be an alternative approach for downregulating IGF/EGF signalling and controlling the impact of LDL in breast cancer patients.

PCSK9 and cancer: Rethinking the link

BACKGROUND

Cancer is emerging as a major problem globally, as it accounts for the second cause of death despite medical advances. According to epidemiological and basic studies, cholesterol is involved in cancer progression and there are abnormalities in cholesterol metabolism of cancer cells including prostate, breast, and colorectal carcinomas. However, the importance of cholesterol in carcinogenesis and thereby the role of cholesterol homeostasis as a therapeutic target is still a debated area in cancer therapy. Proprotein convertase subtilisin/kexin type-9 (PCSK9), a serine protease, modulates cholesterol metabolism by attachment to the LDL receptor (LDLR) and reducing its recycling by targeting the receptor for lysosomal destruction. Published research has shown that PCSK9 is also involved in degradation of other LDLR family members namely very-low-density-lipoprotein receptor (VLDLR), lipoprotein receptor-related protein 1 (LRP-1), and apolipoprotein E receptor 2 (ApoER2). As a result, this protein represents an interesting therapeutic target for the treatment of hypercholesterolemia. Interestingly, clinical trials on PCSK9-specific monoclonal antibodies have reported promising results with high efficacy in lowering LDL-C and in turn reducing cardiovascular complications. It is important to note that PCSK9 mediates several other pathways apart from its role in lipid homeostasis, including antiviral activity, hepatic regeneration, neuronal apoptosis, and modulation of various signaling pathways. Furthermore, recent literature has illustrated that PCSK9 is closely associated with incidence and progression of several cancers. In a number of studies, PCSK9 siRNA was shown to effectively suppress the proliferation and invasion of the several studied tumor cells. Hence, a novel application of PCSK9 inhibitors/silencers in cancer/metastasis could be considered. However, due to poor data on effectiveness and safety of PCSK9 inhibitors in cancer, the impact of PCSK9 inhibition in these pathological conditions is still unknown.

SEARCH METHODS

A vast literature search was conducted to find intended studies from 1956 up to 2020, and inclusion criteria were original peer-reviewed publications.

PURPOSE OF REVIEW

To date, PCSK9 has been scantly investigated in cancer. The question that needs to be discussed is "How does PCSK9 act in cancer pathophysiology and what are the risks or benefits associated to its inhibition?". We reviewed the available publications highlighting the contribution of this proprotein convertase in pathways related to cancer, with focus on the potential implications of its long-term pharmacological inhibition in cancer therapy.

Analysis of Saliva Lipids in Breast and Prostate Cancer by IR Spectroscopy

We have developed a method for studying the lipid profile of saliva, combining preliminary extraction and IR spectroscopic detection. The case-control study involved patients with a histologically verified diagnosis of breast and prostate cancer and healthy volunteers. The comparison group included patients with non-malignant pathologies of the breast (fibroadenomas) and prostate gland (prostatic intraepithelial neoplasia). Saliva was used as a material for biochemical studies. It has been shown that the lipid profile of saliva depends on gender, and for males it also depends on the age group. In cancer pathologies, the lipid profile changes significantly and also depends on gender and age characteristics. The ratio of 1458/1396 cm-1 for both breast and prostate cancer has a potential diagnostic value. In both cases, this ratio decreases compared to healthy controls. For prostate cancer, the ratio of 2923/2957 cm-1 is also potentially informative, which grows against the background of prostate pathologies. It is noted that, in all cases, changes in the proposed ratios are more pronounced in the early stages of diseases, which increases the relevance of their study in biomedical applications.

Hypercholesterolemia Is an Associated Factor for Risk of Differentiated Thyroid Cancer in Chinese Population

Background

Hyperlipidemia has been hypothesized as a risk factor for thyroid cancer. However, the association between hypercholesterolemia and thyroid cancer is unclear, especially in Chinese population without available published data. We conducted this study to investigate the relationship between hypercholesterolemia and differentiated thyroid cancer (DTC) in Chinese population.

Methods

Three thousand seven hundred forty-eight patients were enrolled in the study, including 2,021 DTC patients and 1,727 benign subjects with benign thyroid nodules. Demographic characteristics, medical history, and clinical hematological examination were collected. Stratified analyses of association between hypercholesterolemia and risk of DTC were done. Multivariable logistic regression models were used to estimate the association between hypercholesterolemia and the risk of thyroid nodules being malignant. This study protocol was approved by the ethics committee of Shandong Provincial Qianfoshan Hospital and assigned in ClinicalTrials.gov protocol registration and results system (NCT03006289, https://clinicaltrials.gov/ct2/show/NCT03006289).

Results

The level of serum total cholesterol in patients with DTC is higher than that in benign subjects (P < 0.001). After adjusting hypercholesterolemia, age (P < 0.001), triglyceride (P = 0.003), and thyroid stimulating hormone (TSH) (P < 0.001) are found to be confounding factors. The risk of DTC in patients younger than 45 years old is 2.08 times than that of patients older than 45 years old (odds ratio = 0.48, 95% CI (0.38, 0.61), P < 0.001). A high TSH level is highly associated with the increased risk of DTC (P < 0.001). The multivariable logistic regression analysis revealed that the absence of hypercholesterolemia could reduce the risk of thyroid nodules being malignant (odds ratio = −0.75, 95% CI (−1.39, −0.12), P = 0.02). Comparing to the higher level of serum total cholesterol (>5.7 mmol/L), the closer the serum total cholesterol level is to normal (3.17–5.7 mmol/L), the less the risk of thyroid nodules being malignant is, and this difference is statistically significant (odds ratio = −0.67, 95% CI (−1.31, −0.03), P = 0.040). However, this difference is not found in the group of patients with lower level of total cholesterol (<3.17 mmol/L, odds ratio = 0.43, 95% CI (−1.22, 2.09), P = 0.068), suggesting that hypocholesterolemia is not a protective factor in the risk of thyroid nodules being malignant.

Conclusions

Hypercholesterolemia is an associated factor for risk of DTC in Chinese population.

Impact of Dyslipidemia on the Risk of Second Cancer in Thyroid Cancer Patients: A Korean National Cohort Study

BACKGROUND

Studies have shown that radioactive iodine therapy (RAIT) affects the development of second cancer in thyroid cancer patients. The impact of other factors, such as dyslipidemia are not clear.

METHODS

A retrospective analysis of thyroid cancer patients with a 1,251,913 person-year follow-up was conducted using data from the Health Insurance Review and Assessment database in South Korea from January 2008 to December 2018. We investigated factors related to second cancer development using a nested case-control analysis to avoid length bias.

RESULTS

The overall risk of developing second cancer was higher in thyroid cancer patients than in the general population [standardized incidence ratio, 3.34; 95% confidence interval (CI) 3.30-3.39]. Second cancer incidence was higher in patients who received RAIT than in those who did not [odds ratio (OR) 1.130; 95% CI 1.094-1.169]. Moreover, the risk of second cancer was higher in patients with dyslipidemia than in those without dyslipidemia (OR 1.265; 95% CI 1.223-1.309). After adjustment for RAIT, the incidence of a second cancer was higher in patients with dyslipidemia than in those without dyslipidemia (OR 1.262; 95% CI 1.221-1.306).

CONCLUSIONS

The risk of second cancer development in patients with thyroid cancer appears to be high. Dyslipidemia may be associated with an increased risk of several types of second cancers.

Contribution of the Low-Density Lipoprotein Receptor Family to Breast Cancer Progression

The low-density lipoprotein receptor (LDLR) family comprises 14 single-transmembrane receptors sharing structural homology and common repeats. These receptors specifically recognize and internalize various extracellular ligands either alone or complexed with membrane-spanning co-receptors that are then sorted for lysosomal degradation or cell-surface recovery. As multifunctional endocytic receptors, some LDLR members from the core family were first considered as potential tumor suppressors due to their clearance activity against extracellular matrix-degrading enzymes. LDLRs are also involved in pleiotropic functions including growth factor signaling, matricellular proteins, and cell matrix adhesion turnover and chemoattraction, thereby affecting both tumor cells and their surrounding microenvironment. Therefore, their roles could appear controversial and dependent on the malignancy state. In this review, recent advances highlighting the contribution of LDLR members to breast cancer progression are discussed with focus on (1) specific expression patterns of these receptors in primary cancers or distant metastasis and (2) emerging mechanisms and signaling pathways. In addition, potential diagnosis and therapeutic options are proposed.

Recruitment of monocytes and epigenetic silencing of intratumoral CYP7B1 primarily contribute to the accumulation of 27-hydroxycholesterol in breast cancer

Previous studies showed that intratumoral 27-Hydroxycholesterol (27-HC), a metabolite of cholesterol, promotes growth, invasion and migration of breast cancer cells and that tumor-associated macrophages (TAMs) in breast cancers are closely related to tumor growth and metastatic progression. However, the relationship between 27-HC and TAMs in breast cancer remains unclear. In the present study, we observed that CYP27A1, the 27-HC synthesizing enzyme, was expressed in a much higher level in THP1 monocytes and THP1-derived macrophages than in breast cancer cells, and the promoter of CYP7B1, the degrading enzyme for 27-HC, was highly methylated in breast tumor cells. In addition, THP-1 monocytes and murine bone marrow cells were differentiated toward M2 type macrophages after being co-cultured with breast cancer cells or being exposed to exosomes derived from breast cancer cells. M2 type macrophages produced higher amounts of 27-HC than M0 and M1 type macrophages. 27-HC not only stimulated ER+ cancer cell proliferation as reported, but also promoted the recruitment of CCR2- and CCR5-expressing monocytes by inducing macrophages to express multiple chemokines including CCL2, CCL3 and CCL4. Taken together, our data demonstrate that the hypermethylation of CYP7B1 and recruitment of monocytes likely contribute to the accumulation of 27-Hydroxycholesterol in breast cancer and that the interaction of 27-HC with macrophages further promote the development of breast cancer.

HDL and LDL: Potential New Players in Breast Cancer Development

Breast cancer is the most prevalent cancer and primary cause of cancer-related mortality in women. The identification of risk factors can improve prevention of cancer, and obesity and hypercholesterolemia represent potentially modifiable breast cancer risk factors. In the present work, we review the progress to date in research on the potential role of the main cholesterol transporters, low-density and high-density lipoproteins (LDL and HDL), on breast cancer development. Although some studies have failed to find associations between lipoproteins and breast cancer, some large clinical studies have demonstrated a direct association between LDL cholesterol levels and breast cancer risk and an inverse association between HDL cholesterol and breast cancer risk. Research in breast cancer cells and experimental mouse models of breast cancer have demonstrated an important role for cholesterol and its transporters in breast cancer development. Instead of cholesterol, the cholesterol metabolite 27-hydroxycholesterol induces the proliferation of estrogen receptor-positive breast cancer cells and facilitates metastasis. Oxidative modification of the lipoproteins and HDL glycation activate different inflammation-related pathways, thereby enhancing cell proliferation and migration and inhibiting apoptosis. Cholesterol-lowering drugs and apolipoprotein A-I mimetics have emerged as potential therapeutic agents to prevent the deleterious effects of high cholesterol in breast cancer.

CYP27A1 inhibits bladder cancer cells proliferation by regulating cholesterol homeostasis

CYP27A1, an enzyme involved in regulating cellular cholesterol homeostasis, converts cholesterol into 27-hydroxycholesterol (27-HC). The relationship between CYP27A1 and cell proliferation was studied to determine the role of CYP27A1 in bladder cancer. The expression of CYP27A1 in three bladder cancer cell lines (T24, UM-UC-3 and 5637) were assessed by qRT-PCR and Western blotting, and cells with stable CYP27A1 expression were generated by lentiviral infection. Cell proliferation was detected by MTT assays, colony formation assays and a tumor xenograft model in vitro and in vivo, and the intracellular 27-HC and cholesterol secretion levels were detected by enzyme-linked immunosorbent assays (ELISA). The results revealed that CYP27A1 expression was downregulated in androgen receptor (AR)-positive T24/UM-UC-3 cells compared with AR-negative 5637 cell. After CYP27A1 expression was restored, cell proliferation was inhibited in vitro and in vivo because much more intracellular 27-HC was produced in the CYP27A1-overexpressing cells than in the control cells. Both T24 and UM-UC-3 cells treated with 27-HC showed similar results. In addition, CYP27A1/27HC could reduce the cellular cholesterol level in both T24 and UM-UC-3 cells by upregulating ATP-binding cassette transporters G1 and A1 (ABCG1 and ABCA1) through Liver X receptors (LXRs) pathway and downregulating low-density lipoprotein receptor (LDLR) expression. These findings all suggest that CYP27A1 is a critical cholesterol sensor in bladder cancer cells that may contribute significantly to bladder cancer proliferation.

Challenges and perspectives in the treatment of diabetes associated breast cancer

Type 2 diabetes mellitus is one of the most common chronic disease worldwide and affects all cross-sections of the society including children, women, youth and adults. Scientific evidence has linked diabetes to higher incidence, accelerated progression and increased aggressiveness of different cancers. Among the different forms of cancer, research has reinforced a link between diabetes and the risk of breast cancer. Some studies have specifically linked diabetes to the highly aggressive, triple negative breast cancers (TNBCs) which do not respond to conventional hormonal/HER2 targeted interventions, have chances of early recurrence, metastasize, tend to be more invasive in nature and develop drug resistance. Commonly used anti-diabetic drugs, such as metformin, have recently gained importance in the treatment of breast cancer due to their proposed anti-cancer properties. Here we discuss the link between diabetes and breast cancer, the metabolic disturbances in diabetes that support the development of breast cancer, the challenges involved and future perspective and directions. We link the three main metabolic disturbances (dyslipidemia, hyperinsulinemia and hyperglycemia) that occur in diabetes to potential aberrant molecular pathways that may lead to the development of an oncogenic phenotype of the breast tissue, thereby leading to acceleration of cell growth, proliferation, migration, inflammation, angiogenesis, EMT and metastasis and inhibition of apoptosis in breast cancer cells. Furthermore, managing diabetes and treating cancer using a combination of anti-diabetic and classical anti-cancer drugs should prove to be more efficient in the treatment diabetes associated cancers.

27-hydroxycholesterol: A novel player in molecular carcinogenesis of breast and prostate cancer

Several studies have suggested an etiological role for hypercholesterolemia in the pathogenesis of breast cancer and prostate cancer (PCa). However, the molecular mechanisms that underlie and mediate the hypercholesterolemia-fostered increased risk for breast cancer and PCa are yet to be determined. The discovery that the most abundant cholesterol oxidized metabolite in the plasma, 27 hydroxycholesterol (27-OHC), is a selective estrogen receptor modulator (SERM) and an agonist of Liver X receptors (LXR) partially fills the void in our understanding and knowledge of the mechanisms that may link hypercholesterolemia to development and progression of breast cancer and PCa. The wide spectrum and repertoire of SERM and LXR-dependent effects of 27-OHC in the context of all facets and aspects of breast cancer and prostate cancer biology are reviewed in this manuscript in a very comprehensive manner. This review highlights recent findings pertaining to the role of 27-OHC in breast cancer and PCa and delineates the signaling mechanisms involved in the governing of different facets of tumor biology, that include tumor cell proliferation, epithelial-mesenchymal transition (EMT), as well as tumor cell invasion, migration, and metastasis. We also discuss the limitations of contemporary studies and lack of our comprehension of the entire gamut of effects exerted by 27-OHC that may be relevant to the pathogenesis of breast cancer and PCa. We unveil and propose potential future directions of research that may further our understanding of the role of 27-OHC in breast cancer and PCa and help design therapeutic interventions against endocrine therapy-resistant breast cancer and PCa.

Expression of oxysterol pathway genes in oestrogen-positive breast carcinomas

OBJECTIVE

This study investigated whether gene expression levels of key modulators of the oxysterol signalling pathway modify the prognosis of patients with oestrogen receptor-positive (ER+) breast carcinomas via interaction with endocrine therapy.

CONTEXT

The prognosis of patients with ER+ breast carcinoma depends on several factors. Previous studies have suggested that some oxygenated forms of cholesterol (oxysterols) bind to oestrogen receptor and anti-oestrogen binding site which may deregulate cholesterol homoeostasis and influence effect of therapy.

DESIGN

The expression levels of 70 oxysterol pathway genes were evaluated in a test set of breast carcinomas differing in ER expression. The genes differentially expressed in ER+ tumours were assessed in a comprehensive set of ER+ tumours to evaluate their clinical significance.

PATIENTS

A total of 193 primary patients with breast carcinoma were included.

MEASUREMENTS

The transcript levels were determined by quantitative real-time polymerase chain reaction.

RESULTS

The expression levels of 23 genes were found to be specifically dysregulated in ER+ tumours compared to ER- tumours of the test set. The expression levels of ABCG2, CYP7B1, CYP24A1, CYP39A1 and CH25H genes were found to be strongly associated with disease stage; however, none of the gene expression levels were associated with disease-free survival in patients treated with endocrine therapy.

CONCLUSIONS

The expression of a number of oxysterol pathway genes is significantly modulated by ER expression and associated with the clinical stage of patients. However, the expression of oxysterol pathway genes was not found to modify the prognosis of ER+ patients with breast carcinoma treated with endocrine therapy.

The cholesterol metabolite 27-hydroxycholesterol stimulates cell proliferation via ERβ in prostate cancer cells

BACKGROUND

For every six men, one will be diagnosed with prostate cancer (PCa) in their lifetime. Estrogen receptors (ERs) are known to play a role in prostate carcinogenesis. However, it is unclear whether the estrogenic effects are mediated by estrogen receptor α (ERα) or estrogen receptor β (ERβ). Although it is speculated that ERα is associated with harmful effects on PCa, the role of ERβ in PCa is still ill-defined. The cholesterol oxidized metabolite 27-hydroxycholesterol (27-OHC) has been found to bind to ERs and act as a selective ER modulator (SERM). Increased 27-OHC levels are found in individuals with hypercholesterolemia, a condition that is suggested to be a risk factor for PCa.

METHODS

In the present study, we determined the extent to which 27-OHC causes deleterious effects in the non-tumorigenic RWPE-1, the low tumorigenic LNCaP, and the highly tumorigenic PC3 prostate cancer cells. We conducted cell metabolic activity and proliferation assays using MTS and CyQUANT dyes, protein expression analyses via immunoblots and gene expression analyses via RT-PCR. Additionally, immunocytochemistry and invasion assays were performed to analyze intracellular protein distribution and quantify transepithelial cell motility.

RESULTS

We found that incubation of LNCaP and PC3 cells with 27-OHC significantly increased cell proliferation. We also demonstrate that the ER inhibitor ICI 182,780 (fulvestrant) significantly reduced 27-OH-induced cell proliferation, indicating the involvement of ERs in proliferation. Interestingly, ERβ levels, and to a lesser extent ERα, were significantly increased following incubation of PCa cells with 27-OHC. Furthermore, in the presence of the ERβ specific inhibitor, PHTPP, 27-OHC-induced proliferation is attenuated.

CONCLUSIONS

Altogether, our results show for the first time that 27-OHC, through ER activation, triggers deleterious effect in prostate cancer cell lines. We propose that dysregulated levels of 27-OHC may trigger or exacerbate prostate cancer via acting on ERβ.

Hypertension, serum lipids and cancer risk: A review of epidemiological evidence

Although the association between blood pressure, serum lipids and cancer risk has been investigated, the results are controversial. The aim of this literature review was to examine the epidemiological evidence and provide overview of the association between blood pressure, serum lipids and cancer risk. The arterial hypertension is closely linked with renal cell cancer development. Risk of renal cell cancer was 2-4 times higher for persons with arterial hypertension, independently of sex. In some studies arterial hypertension as one of the components of the metabolic syndrome, was associated with a higher risk of colorectal, prostate cancer and malignant melanoma. Studies suggest that a higher total serum cholesterol level is linked with higher risk of colorectum, colon, prostate and testicular cancer and lower risk of stomach, liver and hematopoietic and lymphoid tissues cancer. There was positive association between serum triglycerides and esophageal, colorectal, lung, renal, thyroid cancer. Given that hypertension is a common risk factor worldwide and its control remains inadequate, our analysis supports the relevance of public health programs aimed at reducing hypertension to reduce the incidence of a number of cancers including renal cell cancer. Effective cholesterol control may lower the risk of cancer, but further studies with longer follow-up and repeated measurements of cholesterol and other lipids are needed.

27-Hydroxycholesterol stimulates cell proliferation and resistance to docetaxel-induced apoptosis in prostate epithelial cells

Although the causes of prostate cancer (PCa) and benign prostatic hyperplasia (BPH) are not known, the role of oxidative stress, aging, and diet are suspected to increase the incidence of prostate complications. The cholesterol oxidation derivative (oxysterol) 27-hydroxycholesterol (27-OHC) is the most prevalent cholesterol metabolite in the blood. As aging, oxidative stress, and hypercholesterolemia are associated with increased risk of PCa and BPH, and because 27-OHC levels are also increased with aging, hypercholesterolemia, and oxidative stress, determining the role of 27-OHC in the progression of PCas and BPH is warranted. In this study, we determined the effect of 27-OHC in human prostate epithelial cells RWPE-1. We found that 27-OHC stimulates proliferation and increases androgen receptor (AR) transcriptional activity. 27-OHC also increased prostate-specific antigen expression and enhanced AR binding to the androgen response element compared to controls. Silencing AR expression with siRNA markedly reduced the 27-OHC-induced proliferation. Furthermore, 27-OHC blocked docetaxel-induced apoptosis. Altogether, our results suggest that 27-OHC may play an important role in PCa and BPH progression by promoting proliferation and suppressing apoptosis.

Breast cancer and (25R)-26-hydroxycholesterol

(25R)-26-Hydroxycholesterol (27-hydroxycholesterol) has been found to accumulate in breast tissue and to stimulate tumor growth via the estrogen receptor. Although most tissues express CYP27A1, the highest levels are in macrophages and most attention had been given to the production of 27-hydroxycholesterol in sub-endothelial macrophages as part of reverse cholesterol transport. In view of the newly identified biologic activity, it is important to consider the determinants of the levels of 27-hydroxycholesterol in macrophages that infiltrate breast tissue. Among these determinants are the oxysterol binding proteins expressed in macrophages, the level of expression of CYP7B1, the oxysterol 7 alpha hydroxylase that generates an inactive triol, and further oxidation of 27-hydroxycholestrol to the C27 acid by multifunctional CYP27A1. Transport of 27-hydroxycholesterol from macrophages to plasma is HDL-associated. In many tissues the ratio of 27-hydroxycholesterol to cholesterol (ng/μg) is higher than that in plasma. Tamoxifen, an effective estrogen receptor antagonist that prevents breast cancer, also has the biologic property of blocking several steps in the lanosterol to cholesterol metabolic pathway. In genetically disposed women, tamoxifen may increase the amount of 27-hydroxycholesterol in breast tissue.

The cholesterol metabolite 27-hydroxycholesterol regulates p53 activity and increases cell proliferation via MDM2 in breast cancer cells

Estrogen is synthesized from cholesterol and high cholesterol levels are suggested to be associated with increased risk of estrogen receptor(ER)-positive breast cancer. The cholesterol metabolite 27-hydroxycholesterol (27-OHC) was recently identified as a selective estrogen receptor modulator (SERM) and may therefore impact breast cancer progression. However, the mechanisms by which 27-OHC may contribute to breast cancer are not all known. We determined the extent to which 27-OHC regulates cell proliferation in MCF7 ER-positive breast cancer cell line involving the tumor suppressor protein p53. We found that treatment of MCF7 cells with 27-OHC resulted reduced p53 transcriptional activity. Conversely, treatment of the ER-negative MDA-MB 231 cells with 27-OHC induced no significant change in p53 activity. Exposure of MCF7 cells to 27-OHC was also associated with increased protein levels of the E3 ubiquitin protein ligase MDM2 and decreased levels of p53. Moreover, 27-OHC also enhanced physical interaction between p53 and MDM2. Furthermore, 27-OHC-induced proliferation was attenuated using either the p53 activator Tenovin-1 or the MDM2 inhibitor Nutlin-3 and Mdm2 siRNA. Taken together, our results indicate that 27-OHC may contribute to ER-positive breast cancer progression by disrupting constitutive p53 signaling in an MDM2-dependent manner.

Cholesterol and breast cancer pathophysiology

Cholesterol is a risk factor for breast cancer although the mechanisms by which this occurs are not well understood. One hypothesis is that dyslipidemia results in increased cholesterol content in cell membranes, thus impacting upon membrane fluidity and subsequent signaling. In addition, studies demonstrate that the metabolite, 27-hydroxycholesterol (27HC), can function as an estrogen, increasing the proliferation of estrogen receptor (ER)-positive breast cancer cells. This was unexpected because 27HC and other oxysterols activate the liver X receptors (LXR), resulting in a reduction of intracellular cholesterol. Resolution of this paradox will require dissection of the molecular mechanisms by which ER and LXR converge in breast cancer cells. Regardless, the observation that 27HC influences breast cancer provides a rationale for strategies that target cholesterol metabolism.

27-hydroxycholesterol and the expression of three estrogen-sensitive proteins in MCF7 cells

The principal aim of this study was to analyze in estrogen receptor-positive MCF7 cells the response of three estrogen-dependent proteins to 27-hydroxycholesterol (27OHC), a major circulating cholesterol metabolite. Immunofluorescence, immunoblotting and immunogold labelling analyses of MCF7 cells exposed for up to 72 h to 2 nM estradiol (E2) or to 2 µM 27OHC demonstrated similar responses in the expression of MnSOD and ERβ compared to the non-stimulated cells. Thus, the results confirm 27OHC's function as a novel selective estrogen receptor modulator (SERM). The epithelial to mesenchymal transition (EMT), observed in MCF7 cells stimulated for longer than 48 h with 2 µM 27OHC, was accompanied by lower immunoreactive levels of nuclear FOXM1 in comparison to E2-treated cells. The results presented in this study are discussed taking into consideration the relationship of hypercholesterolemia, 27OHC production, ROS synthesis and macrophage infiltration, potentially occurring in obese patients with ERα-positive, infiltrated mammary tumors.