Interplay between estrogen and retinoid signaling in breast cancer--current and future perspectives

Screening (ant)agonistic activities of xenobiotics on the retinoic acid receptor alpha (RARα) using in vitro and in silico analysis

Retinoic acid receptors (RARs) are known as crucial endocrine receptors that could mediate a broad diversity of biological processes. However, the data on endocrine disrupting effects of emerging chemicals by targeting RAR (ant)agonism are far from sufficient. Herein, we investigated the RARα agonistic or antagonistic activities for 75 emerging chemicals of concern, and explored their interactions with this receptor. A recombinant two-hybrid yeast assay was used to examine the RARα activities of the test chemicals, wherein 7 showed effects of RARα agonism and 54 exerted potentials of RARα antagonism. The representative chemicals with RARα agonistic activities, i.e. 4-hydroxylphenol (4-HP) and bisphenol AF (BPAF), significantly increased the mRNA levels of CRABP2 and CYP26A1, while 4 select chemicals with RARα antagonistic potentials, including bisphenol A (BPA), tetrabromobisphenol A (TBBPA), 4-tert-octylphenol (4-t-OP), and 4-n-nonylphenol (4-n-NP), conversely decreased the transcriptional levels of the test genes. The in silico molecular docking analysis using 3 different approaches further confirmed the substantial binding between the chemicals with RARα activities and this nuclear receptor protein. This work highlights the promising strategy for screening endocrine-disrupting effects of emerging chemicals of concern by targeting RARα (ant)agonism.

Association between dietary vitamin A intake and risk of cardiometabolic multimorbidity

The association between vitamin A and single cardiometabolic diseases has been extensively studied, but the relationship between dietary vitamin A intake and the risk of cardiometabolic multimorbidity (CMM) has not been studied. Therefore, the present study was conducted to explore the association with CMM risk by analyzing different sources of vitamin A. This study utilized 13,603 subjects aged ≥ 18 years from 1997 to 2015 from the China Health and Nutrition Survey (CHNS). Dietary intake was calculated from 3 consecutive 24-h dietary recalls combined with a house hold food inventory. CMM is defined as the development of at least two cardiometabolic diseases. After a median follow-up of 9.0 years, there were 1050 new cases of CMM. The risk of CMM was significantly lower in those with higher vitamin A intake (Q1 vs Q5 HR 0.66, 95% CI 0.54-0.81). β-carotene (Q1 vs Q5 HR 0.82, 95% CI 0.66-1.02) and retinol (Q1 vs Q5 HR 0.59, 95% CI 0.48-0.73) intake had a similarly negative correlation. Using restricted cubic spline found an L-shaped relationship between retinol intake and CMM (p non-linear < 0.001). Negative associations were also found in specific CMD groups (hypertension, cardiovascular disease, stroke and diabetes). Dietary intake of vitamin A was negatively associated with CMM risk, and this protective effect was more pronounced in patients with cardiovascular disease. There was an L-shaped association between retinol intake and CMM risk.

Dietary Total Vitamin A, β-carotene, and Retinol Intake and the Risk of Diabetes in Chinese Adults with Plant-based Diets

PURPOSE

Epidemiologic evidence regarding the role of dietary vitamin A in the development of diabetes is limited and inconsistent. This study was to explore the association between vitamin A intake and diabetes risk in Chinese adults.

METHODS

A prospective cohort study was conducted among 17 111 adults (8537 men and 8577 women) who participated in the China Health and Nutrition Survey between 1989 and 2015. Dietary intakes were assessed by 3 consecutive 24-hour dietary recalls combined with a household food inventory. Diabetes was determined by self-reported diagnosis, diabetes medication use, or additional criterion in 2009 of fasting blood glucose or hemoglobin A1c. We analyzed the association of vitamin A intake (total, β-carotene, retinol) with diabetes risk using Cox proportional hazards models.

RESULTS

A total of 519 men and 531 women developed diabetes during a median of 11 years of follow-up. Higher dietary total vitamin A intakes were associated with a lower risk of diabetes in both men (quintile 5 [Q5] vs Q1: hazard ratio [HR] = 0.69, 95% CI, 0.49-0.97, P-trend = 0.079) and women (Q5 vs Q1: HR = 0.63; 95% CI, 0.45-0.89; P-trend = 0.039). An inverse relation with diabetes risk was observed for dietary intakes of β-carotene (Q5 vs Q1: HR = 0.71; 95% CI, 0.52-0.97) and retinol (Q5 vs Q1: HR = 0.58; 95% CI, 0.39-0.85) among men, but not women. Dose-response analyses showed the association of dietary intakes of total vitamin A, β-carotene, and retinol with diabetes risk in men was L-shaped (P-nonlinearity = 0.043), reverse J-shaped (P-nonlinearity = 0.001), and linear, respectively.

CONCLUSION

Our findings suggest that adequate intake of vitamin A may help protecting against diabetes, especially for men.

Prediction of blood-based biomarkers and subsequent design of bisulfite PCR-LDR-qPCR assay for breast cancer detection

Background

Interrogation of site-specific CpG methylation in circulating tumor DNAs (ctDNAs) has been employed in a number of studies for early detection of breast cancer (BrCa). In many of these studies, the markers were identified based on known biology of BrCa progression, and interrogated using methyl-specific PCR (MSP), a technique involving bisulfite conversion, PCR, and qPCR.

Methods

In this report, we are demonstrating the development of a novel assay (Multiplex Bisulfite PCR-LDR-qPCR) which can potentially offer improvements to MSP, by integrating additional steps such as ligase detection reaction (LDR), methylated CpG target enrichment, carryover protection (use of uracil DNA glycosylase), and minimization of primer-dimer formation (use of ribose primers and RNAseH2). The assay is designed to for breast cancer-specific CpG markers identified through integrated analyses of publicly available genome-wide methylation datasets for 31 types of primary tumors (including BrCa), as well as matching normal tissues, and peripheral blood.

Results

Our results indicate that the PCR-LDR-qPCR assay is capable of detecting ~ 30 methylated copies of each of 3 BrCa-specific CpG markers, when mixed with excess amount unmethylated CpG markers (~ 3000 copies each), which is a reasonable approximation of BrCa ctDNA overwhelmed with peripheral blood cell-free DNA (cfDNA) when isolated from patient plasma. The bioinformatically-identified CpG markers are located in promoter regions of NR5A2 and PRKCB, and a non-coding region of chromosome 1 (upstream of EFNA3). Additional bioinformatic analyses would reveal that these methylation markers are independent of patient race and age, and positively associated with signaling pathways associated with BrCa progression (such as those related to retinoid nuclear receptor, PTEN, p53, pRB, and p27).

Conclusion

This report demonstrates the potential utilization of bisulfite PCR-LDR-qPCR assay, along with bioinformatically-driven biomarker discovery, in blood-based BrCa detection.

Vitamin A and Breast Cancer Survival: A Systematic Review and Meta-analysis

BACKGROUND

The association between vitamin A intake and breast cancer survival has been inconsistent. We conducted a systemic review and meta-analysis to summarize the results on the association between dietary or supplement vitamin A and its derivatives and breast cancer-specific survival and overall survival (OS). MATERIALS AND METHODS: A comprehensive search of PubMed and EMBASE was performed from inception to January 31, 2018. The summary hazard ratios and 95% confidence intervals were estimated using a random effects model.

RESULTS

Ten studies (8 cohort, 1 clinical trial, and 1 of pooled studies), with 19,450 breast cancer cases, were included in the meta-analysis. The dietary intake of β-carotene was significantly associated with improved breast cancer OS, with a summary hazard ratio of 0.70 (95% confidence interval, 0.50-0.99; I² = 37.5%) for the highest versus lowest intake and 0.93 (95% confidence interval, 0.88-0.99; I² = 38.7%) per 1200 μg/day increment of intake when assessing diet before diagnosis. Meta-regression analysis showed that adjustment for body mass index was a modified factor for the association between the intake of β-carotene and breast cancer OS (P = .013). However, the intake of other vitamin A derivatives (eg, α-carotene, β-cryptoxanthin, lycopene, retinol, lutein) had no effect on breast cancer prognosis when assessing diet before and after the diagnosis.

CONCLUSION

Our findings suggest limited evidence for the significantly inverse association between the prediagnosis dietary intake of β-carotene and OS among women with breast cancer. However, the intake of other vitamin A derivatives was not significantly associated with survival.

Gestational exposure to chlordecone promotes transgenerational changes in the murine reproductive system of males

Environmental factors can affect epigenetic events during germline reprogramming and impose distinctive transgenerational consequences onto the offspring. In this study, we examined the transgenerational effects of chlordecone (CD), an organochlorine insecticide with well-known estrogenic properties. We exposed pregnant mice to CD from embryonic day 6.5 to 15.5 and observed a reduction in spermatogonia (SG) numbers in F3, meiotic defects in spermatocytes and decrease in spermatozoa number in the first and third generation of male progeny. The RNA qRT-PCR expression analysis in F1 and transcriptomics analysis in F3 males using the whole testes revealed changes in the expression of genes associated with chromosome segregation, cell division and DNA repair. The expression of the master regulator of pluripotency, Pou5f1, decreased in foetal and increased in adult F1, but not in F3 adult testes. Analysis of histone H3K4me3 distribution revealed widespread changes in its occupancy in the genome of F1 and F3 generations. We established that 7.1% of altered epigenetic marks were conserved between F1 and F3 generations. The overlapping changes common to F1 and F3 include genes implicated in cell adhesion and transcription factor activities functions. Differential peaks observed in F1 males are significantly enriched in predicted ESR1 binding sites, some of which we confirmed to be functional. Our data demonstrate that CD-mediated impairment of reproductive functions could be transmitted to subsequent generations.

RA and ω-3 PUFA co-treatment activates autophagy in cancer cells

Retinoic acid (RA), is a promising therapeutic agent for the treatment of breast cancer. However, metabolic disorders and drug resistance reduce the efficacy of RA. In this study, we found that RA and ω-3 polyunsaturated fatty acids (ω-3 PUFAs) synergistically induced cell death in vitro and in vivo and autophagy activation. Moreover, RA-induced hypercholesterolemia was completely corrected by ω-3 PUFA supplementation. In addition, we demonstrated that the effects of this combination on the autophagic flux were independent of the two major canonic regulatory complexes controlling autophagic vesicle formation. The treatment activated Gαq-p38 MAPK signaling pathways, which resulted in autophagy of breast cancer cells. Knockdown of Gαq or P38 expression prevented RA and ω-3 PUFAs from inducing autophagy. Data indicated that Gαq-p38activation was mediated by the co-activation of GPR40 and RARα in lipid rafts, rather than by the activation of GPR120, RARβ, or RARγ. The results of this study suggest that hyperlipidemic drug side effects may be ameliorated by the administration of ω-3 PUFAs. Thus, the therapeutic indexes of the corresponding drugs may be increased.

Human papillomavirus type 16 E7 oncoprotein upregulates the retinoic acid receptor-beta expression in cervical cancer cell lines and K14E7 transgenic mice

Persistent infection with high-risk human papillomaviruses is the main etiological factor in cervical cancer (CC). The human papillomavirus type 16 (HPV16) E7 oncoprotein alters several cellular processes, regulating the expression of many genes in order to avoid cell cycle control. Retinoic acid receptor beta (RARB) blocks cell growth, inducing differentiation and apoptosis. This tumor suppressor gene is gradually silenced in late passages of foreskin keratinocytes immortalized with HPV16 and in various tumors, including CC, mainly by epigenetic modifications. We investigated the effect of E7 oncoprotein on RARB gene expression. We found that HPV16 E7 increases RARB mRNA and RAR-beta protein expression both in vitro and in the cervix of young K14E7 transgenic mice. In E7-expressing cells, RARB overexpression is further increased in the presence of the tumor suppressor p53 (TP53) R273C mutant. This effect does not change when either C33-A or E7-expressing C33-A cell line is treated with Trichostatin A, suggesting that E7 enhances RARB expression independently of histone deacetylases inhibition. These findings indicate that RARB overexpression is part of the early molecular events induced by the E7 oncoprotein.

Vitamin A, cancer treatment and prevention: the new role of cellular retinol binding proteins

Retinol and vitamin A derivatives influence cell differentiation, proliferation, and apoptosis and play an important physiologic role in a wide range of biological processes. Retinol is obtained from foods of animal origin. Retinol derivatives are fundamental for vision, while retinoic acid is essential for skin and bone growth. Intracellular retinoid bioavailability is regulated by the presence of specific cytoplasmic retinol and retinoic acid binding proteins (CRBPs and CRABPs). CRBP-1, the most diffuse CRBP isoform, is a small 15 KDa cytosolic protein widely expressed and evolutionarily conserved in many tissues. CRBP-1 acts as chaperone and regulates the uptake, subsequent esterification, and bioavailability of retinol. CRBP-1 plays a major role in wound healing and arterial tissue remodelling processes. In the last years, the role of CRBP-1-related retinoid signalling during cancer progression became object of several studies. CRBP-1 downregulation associates with a more malignant phenotype in breast, ovarian, and nasopharyngeal cancers. Reexpression of CRBP-1 increased retinol sensitivity and reduced viability of ovarian cancer cells in vitro. Further studies are needed to explore new therapeutic strategies aimed at restoring CRBP-1-mediated intracellular retinol trafficking and the meaning of CRBP-1 expression in cancer patients' screening for a more personalized and efficacy retinoid therapy.