Tryptophan catabolism is dysregulated in leiomyomas

Characterization of m6A Modifiers and RNA Modifications in Uterine Fibroids

Uterine leiomyoma or fibroids are prevalent noncancerous tumors of the uterine muscle layer, yet their origin and development remain poorly understood. We analyzed RNA expression profiles of 15 epigenetic mediators in uterine fibroids compared to myometrium using publicly available RNA sequencing (RNA-seq) data. To validate our findings, we performed RT-qPCR on a separate cohort of uterine fibroids targeting these modifiers confirming our RNA-seq data. We then examined protein profiles of key N6-methyladenosine (m6A) modifiers in fibroids and their matched myometrium, showing no significant differences in concordance with our RNA expression profiles. To determine RNA modification abundance, mRNA and small RNA from fibroids and matched myometrium were analyzed by ultra-high performance liquid chromatography-mass spectrometry identifying prevalent m6A and 11 other known modifiers. However, no aberrant expression in fibroids was detected. We then mined a previously published dataset and identified differential expression of m6A modifiers that were specific to fibroid genetic subtype. Our analysis also identified m6A consensus motifs on genes previously identified to be dysregulated in uterine fibroids. Overall, using state-of-the-art mass spectrometry, RNA expression, and protein profiles, we characterized and identified differentially expressed m6A modifiers in relation to driver mutations. Despite the use of several different approaches, we identified limited differential expression of RNA modifiers and associated modifications in uterine fibroids. However, considering the highly heterogenous genomic and cellular nature of fibroids, and the possible contribution of single molecule m6A modifications to fibroid pathology, there is a need for greater in-depth characterization of m6A marks and modifiers in a larger and diverse patient cohort.

In Vivo Effects of Bay 11-7082 on Fibroid Growth and Gene Expression: A Preclinical Study

Current medical therapies for fibroids have major limitations due to their hypoestrogenic side effects. Based on our previous work showing the activation of NF-kB in fibroids, we hypothesized that inhibiting NF-kB in vivo would result in the shrinkage of tumors and reduced inflammation. Fibroid xenografts were implanted in SCID mice and treated daily with Bay 11-7082 (Bay) or vehicle for two months. Bay treatment led to a 50% reduction in tumor weight. RNAseq revealed decreased expression of genes related to cell proliferation, inflammation, extracellular matrix (ECM) composition, and growth factor expression. Validation through qRT-PCR, Western blotting, ELISA, and immunohistochemistry (IHC) confirmed these findings. Bay treatment reduced mRNA expression of cell cycle regulators (CCND1, E2F1, and CKS2), inflammatory markers (SPARC, TDO2, MYD88, TLR3, TLR6, IL6, TNFα, TNFRSF11A, and IL1β), ECM remodelers (COL3A1, FN1, LOX, and TGFβ3), growth factors (PRL, PDGFA, and VEGFC), progesterone receptor, and miR-29c and miR-200c. Collagen levels were reduced in Bay-treated xenografts. Western blotting and IHC showed decreased protein abundance in certain ECM components and inflammatory markers, but not cleaved caspase three. Ki67, CCND1, and E2F1 expression decreased with Bay treatment. This preclinical study suggests NF-kB inhibition as an effective fibroid treatment, suppressing genes involved in proliferation, inflammation, and ECM remodeling.

Targeting the long non-coding RNA MIAT for the treatment of fibroids in an animal model

Our previous studies indicated that there is overexpression of MIAT in fibroids and MIAT is a sponge for the miR-29 family in these tumors. The objective of the present study was to determine if the knockdown of MIAT in fibroid xenografts will increase miR-29 levels and reduce the expression of genes targeted by this miRNA such as collagen and cell cycle regulatory proteins in a mouse model for fibroids. Ovariectomized CB-17 SCID/Beige mice bearing estrogen/progesterone pellets were implanted subcutaneously in the flank with equal weight of fibroid explants which had been transduced by lentivirus for either control (empty vector) or MIAT knockdown for four weeks (n=7). Knockdown of MIAT in fibroid xenografts resulted in a 30% reduction of tumor weight and a marked increase in miR-29a, -b, and -c levels in the xenografts. There was reduced cell proliferation and expression of cell cycle regulatory genes CCND1, CDK2, and E2F1 and no significant changes in apoptosis. The xenografts with MIAT knockdown expressed lower mRNA and protein levels of FN1, COL3A1, and TGF-β3, and total collagen protein. Targeting MIAT, which sponges the pro-fibrotic miR-29 family, is an effective therapy for fibroids by reducing cell proliferation and thereby, tumor growth and accumulation of ECM, which is a hallmark of these benign gynecologic tumors.

Altered extracellular matrix-related pathways accelerate the transition from normal to prefibroid myometrium in Black women

BACKGROUND

Black women experience a disproportionate impact of uterine fibroids compared to White women, including earlier diagnosis, higher frequency, and more severe symptoms. The etiology underlying this racial disparity remains elusive.

OBJECTIVE

The aim of this study was to evaluate the molecular differences in normal myometrium (fibroid-free uteri) and at-risk myometrium (fibroid-containing uteri) tissues in Black and White women.

STUDY DESIGN

We conducted whole-genome RNA-seq on normal and at-risk myometrium tissues obtained from both self-identified Black and White women (not Hispanic or Latino) to determine global gene expression profiles and to conduct enriched pathway analyses (n=3 per group). We initially assessed the differences within the same type of tissue (normal or at-risk myometrium) between races. Subsequently, we analyzed the transcriptome of normal myometrium compared to at-risk myometrium in each race and determined the differences between them. We validated our findings through real-time PCR (sample size range=5-12), western blot (sample size range=5-6), and immunohistochemistry techniques (sample size range=9-16).

RESULTS

The transcriptomic analysis revealed distinct profiles between Black and White women in normal and at-risk myometrium tissues. Interestingly, genes and pathways related to extracellular matrix and mechanosensing were more enriched in normal myometrium from Black than White women. Transcription factor enrichment analysis detected greater activity of the serum response transcription factor positional motif in normal myometrium from Black compared to White women. Furthermore, we observed increased expression levels of myocardin-related transcription factor-serum response factor and the serum response factor in the same comparison. In addition, we noted increased expression of both mRNA and protein levels of vinculin, a target gene of the serum response factor, in normal myometrium tissues from Black women as compared to White women. Importantly, the transcriptomic profile of normal to at-risk myometrium conversion differs between Black and White women. Specifically, we observed that extracellular matrix-related pathways are involved in the transition from normal to at-risk myometrium and that these processes are exacerbated in Black women. We found increased levels of Tenascin C, type I collagen alpha 1 chain, fibronectin, and phospho-p38 MAPK (Thr180/Tyr182, active) protein levels in at-risk over normal myometrium tissues from Black women, whereas such differences were not observed in samples from White women.

CONCLUSION

These findings indicate that the racial disparities in uterine fibroids may be attributed to heightened production of extracellular matrix in the myometrium in Black women, even before the tumors appear. Future research is needed to understand early life determinants of the observed racial differences.

The Effect of Race/Ethnicity and MED12 Mutation on the Expression of Long Non-Coding RNAs in Uterine Leiomyoma and Myometrium

The objective of this study was to elucidate the expression of long non-coding RNA (lncRNA) in leiomyomas (Lyo) and paired myometrium (Myo) and explore the impact of race and MED12 mutation. Fold change analysis (Lyo/paired Myo) indicated the expression of 63 lncRNAs was significantly altered in the mutated group but not in the non-mutated Lyo. Additionally, 65 lncRNAs exhibited an over 1.5-fold change in the Black but not the White group. Fifteen differentially expressed lncRNAs identified with next-generation sequencing underwent qRT-PCR confirmation. Compared with Myo, the expression of TPTEP1, PART1, RPS10P7, MSC-AS1, SNHG12, CA3-AS1, LINC00337, LINC00536, LINC01436, LINC01449, LINC02433, and LINC02624 was significantly higher, while the expression of ZEB2-AS1, LINC00957, and LINC01186 was significantly lower. Comparison of normal Myo with diseased Myo showed significant differences in the expression of several lncRNAs. Analysis based on race and Lyo MED12 mutation status indicated a significantly higher expression of RPS10P7, SNHG12, LINC01449, LINC02433, and LINC02624 in Lyo from Black patients. The expression of TPTEP1, PART1, RPS10P7, MSC-AS1, LINC00337, LINC00536, LINC01436, LINC01449, LINC02433, and LINC02624 was higher, while LINC01186 was significantly lower in the MED12-mutated group. These results indicate that Lyo are characterized by aberrant lncRNA expression, which is further impacted by race and Lyo MED12 mutation status.

Therapeutic effects of in vivo administration of an inhibitor of tryptophan 2,3-dioxygenase (680c91) for the treatment of fibroids: a preclinical study

OBJECTIVE

Fibroids are characterized by marked overexpression of tryptophan 2,3 dioxygenase (TDO2). The objective of this study was to determine the effectiveness of in vivo administration of an inhibitor of TDO2 (680C91) on fibroid size and gene expression.

DESIGN

Animal and ex vivo human study.

SETTING

Academic Research Institution.

SUBJECTS

Severe combined immunodeficiency mice bearing human fibroid xenografts treated with vehicle and TDO2 inhibitor.

INTERVENTION

Daily intraperitoneal administration of 680C91 or vehicle for 2 months and in vitro studies with fibroid explants.

MAIN OUTCOME MEASURES

Tumor weight and gene expression profile of xenografts and in vitro mechanistic experiments using fibroid explants.

RESULTS

Compound 680C91 was well-tolerated with no effects on blood chemistry and body weight. Treatment of mice with 680C91 resulted in 30% reduction in the weight of fibroid xenografts after 2 months of treatment and as expected lower levels of kynurenine, the byproduct of tryptophan degradation and an endogenous ligand of aryl hydrocarbon receptor (AhR) in the xenografts. The expression of cytochrome P450 family 1 subfamily B member 1 (CYP1B1), transforming growth factor β3 (TGF-β3), fibronectin (FN1), cyclin-dependent kinase 2 (CDK2), E2F transcription factor 1 (E2F1), interleukin 8 (IL-8) and secreted protein acidic and cysteine rich (SPARC) mRNA were lower in the xenografts of mice treated with 680C91 compared with vehicle controls. Similarly, the protein abundance of collagen, FN1, CYP1B1, and SPARC were lower in the xenografts of 680C9- treated mice compared with vehicle controls. Immunohistochemical analysis of xenografts indicated decreased expression of collagen, Ki67 and E2F1 but no significant changes in cleaved caspase 3 expression in mice treated with 680C91. The levels of kynurenine in the xenografts showed a direct correlation with the tumor weight and FN1 levels. In vitro studies with fibroid explants showed a significant induction of CYP1B1, TGF-β3, FN1, CDK2, E2F1, IL8, and SPARC mRNA by tryptophan, which could be blocked by cotreatment with 680C91 and the AhR antagonist CH-223191.

CONCLUSION

The results indicate that correction of aberrant tryptophan catabolism in fibroids could be an effective treatment through its effect to reduce cell proliferation and extracellular matrix accumulation.

Tryptophan metabolism enzymes are potential targets in ovarian clear cell carcinoma

AIM

As the second most prevalent subtype of epithelial ovarian cancers, ovarian clear cell carcinoma (OCCC) is known for its chemoresistance to conventional platinum-based therapy. In this work, we examined the tryptophan (Trp) metabolism enzymes' differential expression in patients with OCCC to assess the potential for personalised treatment.

METHODS

A total of 127 OCCC tissues were used to construct tissue microarrays, and immunohistochemistry (IHC) staining of the Trp enzymes IDO1, IDO2, TDO2 and IL4I1 was performed. The correlations between Trp enzyme expression and clinical characteristics were analysed.

RESULTS

Positive IDO1, IDO2, TDO2 and IL4I1 staining was identified in 26.8%, 94.5%, 75.6% and 82.7% of OCCC respectively. IDO1-positive samples were more common in the chemoresistant group than in the platinum-sensitive group (46.7% vs. 19.8%). Moreover, positive expression of IDO1, TDO2 and IL4I1 was related to advanced stage, metastasis, bilateral tumours, endometriosis and tumour rupture (p < 0.05) respectively. Univariate analysis revealed a significant association between bilateral tumours, lymph node metastasis, advanced stage, distant metastasis and aberrant cytology with a poor prognosis for OCCC, while the absence of residual tumour was correlated with a favourable outcome (p < 0.05). However, only bilateral tumours and lymph node metastases were related to a poor prognosis after multivariate analysis.

CONCLUSION

This is the first study to investigate the expression of the Trp enzymes IDO1, IDO2, TDO2 and IL4I1 in OCCC tissues. IDO2, TDO2 and IL4I1 were detected in the majority of OCCC. Clinical traits were correlated with IDO1, IDO2, TDO2 and IL4I1 expression. IDO1 may be used as a therapeutic target given the large percentage of chemoresistant cases with IDO1 expression. These results will aid the development of personalised therapies for OCCC.

The kynurenine pathway presents multi-faceted metabolic vulnerabilities in cancer

The kynurenine pathway (KP) and associated catabolites play key roles in promoting tumor progression and modulating the host anti-tumor immune response. To date, considerable focus has been on the role of indoleamine 2,3-dioxygenase 1 (IDO1) and its catabolite, kynurenine (Kyn). However, increasing evidence has demonstrated that downstream KP enzymes and their associated metabolite products can also elicit tumor-microenvironment immune suppression. These advancements in our understanding of the tumor promotive role of the KP have led to the conception of novel therapeutic strategies to target the KP pathway for anti-cancer effects and reversal of immune escape. This review aims to 1) highlight the known biological functions of key enzymes in the KP, and 2) provide a comprehensive overview of existing and emerging therapies aimed at targeting discrete enzymes in the KP for anti-cancer treatment.

MED12 mutation activates the tryptophan/kynurenine/AHR pathway to promote growth of uterine leiomyomas

Uterine leiomyomas cause heavy menstrual bleeding, anemia, and pregnancy loss in millions of women worldwide. Driver mutations in the transcriptional mediator complex subunit 12 (MED12) gene in uterine myometrial cells initiate 70% of leiomyomas that grow in a progesterone-dependent manner. We showed a distinct chromatin occupancy landscape of MED12 in mutant MED12 (mut-MED12) versus WT-MED12 leiomyomas. Integration of cistromic and transcriptomics data identified tryptophan 2,3-dioxygenase (TDO2) as the top mut-MED12 target gene that was significantly upregulated in mut-MED12 leiomyomas when compared with adjacent myometrium and WT-MED12 leiomyomas. TDO2 catalyzes the conversion of tryptophan to kynurenine, an aryl hydrocarbon receptor (AHR) ligand that we confirmed to be significantly elevated in mut-MED12 leiomyomas. Treatment of primary mut-MED12 leiomyoma cells with tryptophan or kynurenine stimulated AHR nuclear translocation, increased proliferation, inhibited apoptosis, and induced AHR-target gene expression, whereas blocking the TDO2/kynurenine/AHR pathway by siRNA or pharmacological treatment abolished these effects. Progesterone receptors regulated the expression of AHR and its target genes. In vivo, TDO2 expression positively correlated with the expression of genes crucial for leiomyoma growth. In summary, activation of the TDO2/kynurenine/AHR pathway selectively in mut-MED12 leiomyomas promoted tumor growth and may inform the future development of targeted treatments and precision medicine.

The Influence of Race/Ethnicity on the Transcriptomic Landscape of Uterine Fibroids

The objective of this study was to determine if the aberrant expression of select genes could form the basis for the racial disparity in fibroid characteristics. The next-generation RNA sequencing results were analyzed as fold change [leiomyomas/paired myometrium, also known as differential expression (DF)], comparing specimens from White (n = 7) and Black (n = 12) patients. The analysis indicated that 95 genes were minimally changed in tumors from White (DF ≈ 1) but were significantly altered by more than 1.5-fold (up or down) in Black patients. Twenty-one novel genes were selected for confirmation in 69 paired fibroids by qRT-PCR. Among these 21, coding of transcripts for the differential expression of FRAT2, SOX4, TNFRSF19, ACP7, GRIP1, IRS4, PLEKHG4B, PGR, COL24A1, KRT17, MMP17, SLN, CCDC177, FUT2, MYO5B, MYOG, ZNF703, CDC25A, and CDCA7 was significantly higher, while the expression of DAB2 and CAV2 was significantly lower in tumors from Black or Hispanic patients compared with tumors from White patients. Western blot analysis revealed a greater differential expression of PGR-A and total progesterone (PGR-A and PGR-B) in tumors from Black compared with tumors from White patients. Collectively, we identified a set of genes uniquely expressed in a race/ethnicity-dependent manner, which could form the underlying mechanisms for the racial disparity in fibroids and their associated symptoms.

Characterization of m6A modifiers and RNA modifications in uterine fibroids

Uterine leiomyoma or fibroids are the most common prevalent noncancerous tumors of the uterine muscle layer. Common symptoms associated with fibroids include pelvic pain, heavy menstrual bleeding, anemia, and pelvic pressure. These tumors are a leading cause of gynecological care but lack long-term therapy as the origin and development of fibroids are not well understood. Several next-generation sequencing technologies have been performed to identify the underlying genetic and epigenetic basis of fibroids. However, there remains a systemic gap in our understanding of molecular and biological process that define uterine fibroids. Recent epitranscriptomics studies have unraveled RNA modifications that are associated with all forms of RNA and are thought to influence both normal physiological functions and the progression of diseases. We quantified RNA expression profiles by analyzing publicly available RNA-seq data for 15 known epigenetic mediators to identify their expression profile in uterine fibroids compared to myometrium. To validate our findings, we performed RT-qPCR on a separate cohort of uterine fibroids targeting these modifiers confirming our RNA-seq data. We then examined protein profiles of key m6A modifiers in fibroids and their matched myometrium. In concordance with our RNA expression profiles, no significant differences were observed in these proteins in uterine fibroids compared to myometrium. To determine abundance of RNA modifications, mRNA and small RNA from fibroids and matched myometrium were analyzed by UHPLC MS/MS. In addition to the prevalent N6-methyladenosine (m6A), we identified 11 other known modifiers but did not identify any aberrant expression in fibroids. We then mined a previously published dataset and identified differential expression of m6A modifiers that were specific to fibroid genetic sub-type. Our analysis also identified m6A consensus motifs on genes previously identified to be dysregulated in uterine fibroids. Overall, using state-of-the-art mass spectrometry, RNA expression and protein profiles, we characterized and identified differentially expressed m6A modifiers in relation to driver mutations. Despite the use of several different approaches, we identified limited differential expression of RNA modifiers and associated modifications in uterine fibroids. However, considering the highly heterogenous genomic and cellular nature of fibroids, and the possible contribution of single molecule m6A modifications to fibroid pathology, there is a need for greater in-depth characterization of m6A marks and modifiers in a larger and varied patient cohort.

Therapeutic Effects of Long-Term Administration of Tranilast in an Animal Model for the Treatment of Fibroids

Tranilast (N-3, 4-dimethoxycinnamoyl anthranilic acid) is an orally administered drug with antiallergic properties and approved in Japan and the Republic of Korea for the treatment of asthma and hypertrophic scars. Previous in vitro studies indicated that tranilast reduced fibroid growth through its inhibitory effects on cell proliferation and induction of apoptosis. The objective of this study was to determine the efficacy of tranilast for treatment of human-derived fibroids in a mouse model. SCID mice (ovariectomized, supplemented with estrogen and progesterone) were implanted with fibroid explants and treated for two months with tranilast (50 m/kg/daily) or the vehicle. After sacrifice, xenografts were excised and analyzed. Tranilast was well tolerated without adverse side effects. There was a 37% reduction in tumor weight along with a significant decrease in staining for Ki67, CCND1, and E2F1; a significant increase in nuclear staining for cleaved caspase 3; and reduced staining for TGF-β3 and Masson's trichrome in the tranilast treated mice. There was a significant inhibition of mRNA and protein expression of fibronectin, COL3A1, CCND1, E2F1, and TGF-β3 in the xenografts from the tranilast-treated mice. These promising therapeutic effects of tranilast warrant additional animal studies and human clinical trials to evaluate its efficacy for treatment of fibroids.

Differential Expression of MED12-Associated Coding RNA Transcripts in Uterine Leiomyomas

Recent studies have demonstrated that somatic MED12 mutations in exon 2 occur at a frequency of up to 80% and have a functional role in leiomyoma pathogenesis. The objective of this study was to elucidate the expression profile of coding RNA transcripts in leiomyomas, with and without these mutations, and their paired myometrium. Next-generation RNA sequencing (NGS) was used to systematically profile the differentially expressed RNA transcripts from paired leiomyomas (n = 19). The differential analysis indicated there are 394 genes differentially and aberrantly expressed only in the mutated tumors. These genes were predominantly involved in the regulation of extracellular constituents. Of the differentially expressed genes that overlapped in the two comparison groups, the magnitude of change in gene expression was greater for many genes in tumors bearing MED12 mutations. Although the myometrium did not express MED12 mutations, there were marked differences in the transcriptome landscape of the myometrium from mutated and non-mutated specimens, with genes regulating the response to oxygen-containing compounds being most altered. In conclusion, MED12 mutations have profound effects on the expression of genes pivotal to leiomyoma pathogenesis in the tumor and the myometrium which could alter tumor characteristics and growth potential.

MED12 mutations in uterine leiomyomas: prediction of volume reduction by gonadotropin-releasing hormone agonists

BACKGROUND

Gonadotropin-releasing hormone agonists are used to treat premenopausal uterine leiomyomas; however, leiomyoma volume reduction is not always achieved. The reduction rate after this treatment varies for each leiomyoma, even in the same patient. Therefore, an effective method for predicting uterine leiomyoma volume reduction is required to reduce the adverse hypoestrogenic effects and drug-related economic burden related to gonadotropin-releasing hormone agonists.

OBJECTIVE

This study aimed to determine the predictive use of MED12 mutations for evaluating the effect of gonadotropin-releasing hormone agonist treatment concerning reducing uterine leiomyoma volume and to predict the MED12 mutation status based on the findings of magnetic resonance imaging performed before treatment.

STUDY DESIGN

MED12 exon 2 mutation and erythropoietin expression in uterine leiomyomas were evaluated concerning volume reduction, as measured using magnetic resonance imaging. We developed a system for classifying leiomyomas according to T2-weighted magnetic resonance imaging signals to noninvasively predict the presence or absence of MED12 mutations in leiomyomas. Leiomyoma samples (>5 cm) were obtained from 168 patients during surgery (hysterectomy or myomectomy) between 2005 and 2021 at Yokohama City University Hospital. To analyze the rate of leiomyoma volume reduction, 41 patients had been preoperatively administered the gonadotropin-releasing hormone agonist (leuprorelin acetate 3.75 mg, monthly subcutaneous injection) for 3 months; magnetic resonance imaging was performed before and after treatment without contrast material.

RESULTS

Patients with MED12 exon 2 mutations had smaller volume reduction after treatment with the gonadotropin-releasing hormone agonist (P<.001, Mann-Whitney U test) and displayed lower signal intensity on T2-weighted images than those with leiomyomas expressing wild-type MED12 exon 2. The newly proposed magnetic resonance imaging-based classification system showed that MED12 exon 2 mutations were more frequent in the low-signal group than in the high-signal group, with nearly equal proportions of mutated and wild-type MED12 exon 2 leiomyomas noted in the intermediate group. The low-signal group had significantly lower erythropoietin expression levels than the high-signal group (P<.001, Kruskal-Wallis test with the Dunn posthoc analysis).

CONCLUSION

MED12 mutation status can be a candidate marker for predicting the effect of gonadotropin-releasing hormone agonists on uterine leiomyoma reduction. Magnetic resonance imaging findings can be used to determine MED12 mutation status as a noninvasive strategy to select patients who will most likely benefit from gonadotropin-releasing hormone agonist treatment.

Mono-(2-ethyl-5-hydroxyhexyl) phthalate promotes uterine leiomyoma cell survival through tryptophan-kynurenine-AHR pathway activation

Uterine leiomyoma is the most common tumor in women and causes severe morbidity in 15 to 30% of reproductive-age women. Epidemiological studies consistently indicate a correlation between leiomyoma development and exposure to endocrine-disrupting chemical phthalates, especially di-(2-ethylhexyl) phthalate (DEHP); however, the underlying mechanisms are unknown. Here, among the most commonly encountered phthalate metabolites, we found the strongest association between the urine levels of mono(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), the principal DEHP metabolite, and the risk of uterine leiomyoma diagnosis (n = 712 patients). The treatment of primary leiomyoma and smooth muscle cells (n = 29) with various mixtures of phthalate metabolites, at concentrations equivalent to those detected in urine samples, significantly increased cell viability and decreased apoptosis. MEHHP had the strongest effects on both cell viability and apoptosis. MEHHP increased cellular tryptophan and kynurenine levels strikingly and induced the expression of the tryptophan transporters SLC7A5 and SLC7A8, as well as, tryptophan 2,3-dioxygenase (TDO2), the key enzyme catalyzing the conversion of tryptophan to kynurenine that is the endogenous ligand of aryl hydrocarbon receptor (AHR). MEHHP stimulated nuclear localization of AHR and up-regulated the expression of CYP1A1 and CYP1B1, two prototype targets of AHR. siRNA knockdown or pharmacological inhibition of SLC7A5/SLC7A8, TDO2, or AHR abolished MEHHP-mediated effects on leiomyoma cell survival. These findings indicate that MEHHP promotes leiomyoma cell survival by activating the tryptophan-kynurenine-AHR pathway. This study pinpoints MEHHP exposure as a high-risk factor for leiomyoma growth, uncovers a mechanism by which exposure to environmental phthalate impacts leiomyoma pathogenesis, and may lead to the development of novel druggable targets.

Further characterization of tryptophan metabolism and its dysregulation in fibroids

OBJECTIVE

To determine the expression of enzymes in tryptophan (Trp) catabolism in fibroids and matched myometrium and determine the effects of race and mediator complex subunit 12 gene (MED12) mutation on their expression.

DESIGN

Experimental laboratory study.

SETTING

Academic research laboratory.

PATIENT(S)

Women of reproductive age who underwent hysterectomy while on no hormonal medications before surgery.

INTERVENTION(S)

Fibroids and matched myometrium were obtained from patients who underwent hysterectomy from different race or ethnic groups.

MAIN OUTCOME MEASURE(S)

The expression of enzymes in the Trp catabolic pathway, tryptophan transporters, and the cytochrome P450 1B1 gene (CYP1B1) in the fibroids and matched myometrium of women from different race and ethnic groups and in tumors bearing the MED12 mutation and tumors without the mutation was determined using quantitative reverse-transcription polymerase chain reaction. The levels of serotonin, kynurenic acid (KYNA), and nicotinamide adenine dinucleotide (NAD) were determined using enzyme-linked immunosorbent assay.

RESULT(S)

In fibroids, the expression of tryptophan hydroxylase 1 (TPH1), kynurenine amino transferase (KAT)2, large neutral amino acid transporter small subunit 2 (SLC7A8), and large neutral amino acid transporter small subunit 1 (SLC7A5) messenger RNA (mRNA) was high and that of kynureninase (KYNU) and tryptophanyl-tRNA ligase (WARS1) mRNA was low, with no changes in the expression of WARS2, kynurenine formamidase (AFMID), kynurenine 3-monooxygenase (KMO), KAT1, KAT3, and KAT4 compared with that in the matched myometrium (n = 81). The expression of CYP1B1 mRNA, a marker of the activation of the aryl hydrocarbon receptor, was higher in fibroids. Tumors bearing the MED12 mutation expressed higher levels of CYP1B1 and lower levels of WARS1, KAT1, KAT3, and KAT4 mRNAs compared with tumors without the MED12 mutation. Race or ethnicity affected the expression of KYNU, with tumors from African American and Hispanic patients expressing lower levels of KYNU mRNA compared with those from Caucasian patients. We also quantified the levels of serotonin, KYNA, and NAD, which are the end products of Trp catabolism. There were no significant differences in the levels of serotonin and KYNA, whereas the levels of NAD were lower in fibroids than in the paired myometrium. This reduction in the levels of NAD was independent of race or ethnicity.

CONCLUSION(S)

In addition to the expression of tryptophan 2,3-dioxygenase or indoleamine-pyrrole 2,3-dioxygenase, there was marked dysregulation in the expression of other enzymes in the Trp metabolic pathway and Trp transporters in fibroids. Both MED12 mutation status and race or ethnicity had selective effects on the expression of the components of this pathway. Additional functional studies are necessary to establish the physiologic significance of the tryptophan degradation pathway in the pathogenesis of fibroids and its potential as a target for novel therapies.

Differential Expression of Super-Enhancer-Associated Long Non-coding RNAs in Uterine Leiomyomas

Super-enhancer-associated long non-coding RNAs (SE-lncRNAs) are a specific set of lncRNAs transcribed from super-enhancer (SE) genomic regions. Recent studies have revealed that SE-lncRNAs play essential roles in tumorigenesis through the regulation of oncogenes. The objective of this study was to elucidate the expression profile of SE-lncRNAs with concurrent assessment of associated mRNAs in leiomyomas and paired myometrium. Arraystar SE-lncRNAs arrays were used to systematically profile the differentially expressed SE-lncRNAs along with the corresponding SE-regulated protein coding genes in eight leiomyomas and paired myometrium. The analysis indicated 7680 SE-lncRNAs were expressed, of which 721 SE-lncRNAs were overexpressed, while 247 SE-lncRNAs were underexpressed by 1.5-fold or greater in leiomyoma. Thirteen novel SE-lncRNAs and their corresponding protein coding genes were selected, and their expression was confirmed in eighty-one paired leiomyoma tissues by quantitative real-time PCR. The thirteen pairs of SE-lncRNAs and their corresponding protein coding genes included RP11-353N14.2/CBX4, SOCS2-AS1/SOCS2, RP1-170O19.14/HOXA11, CASC15/PRL, EGFLAM-AS1/EGFLAM, RP11-225H22/NEURL1, RP5-1086K13.1/CD58, AC092839.3/SPTBN1, RP11-69I8.3/CTGF, TM4SF1-AS1/TM4SF1, RP11-373D23/FOSL2, RP11-399K21.11/COMTD1, and CTB-113P19.1/SPARC. Among these SE-lncRNAs, the expression of SOCS2-AS1/SOCS2, RP11-353N14.2/CBX4, RP1-170O19.14/HOXA11, and RP11-225H22/NEURL1 was significantly higher in African Americans as compared with Caucasians. The expression of RP11-353N14.2/CBX4, SOCS2-AS1/SOCS2, CASC15/PRL, and CTB-113P19.1/SPARC was significantly higher in tumors with MED12-mutation-positive as compared with MED12-mutation-negative tumors. Collectively, our results indicate that the differential expression of SE in leiomyomas is another mechanism contributing to dysregulation of protein coding genes in leiomyomas and that race and MED12 mutation can influence the expression of a select group of SE.

Tryptophan 2,3-Dioxygenase-2 in Uterine Leiomyoma: Dysregulation by MED12 Mutation Status

Uterine leiomyomas (fibroids) are common benign tumors in women. The tryptophan metabolism through the kynurenine pathway plays important roles in tumorigenesis in general. Leiomyomas expressing mutated mediator complex subunit 12 (mut-MED12) were reported to contain significantly decreased tryptophan levels; the underlying mechanism and the role of the tryptophan metabolism-kynurenine pathway in leiomyoma tumorigenesis, however, remain unknown. We here assessed the expression and regulation of the key enzymes that metabolize tryptophan. Among these, the tissue mRNA levels of tryptophan 2,3-dioxygenase (TDO2), the rate limiting enzyme of tryptophan metabolism through the kynurenine pathway, was 36-fold higher in mut-MED12 compared to adjacent myometrium (P < 0.0001), and 14-fold higher compared to wild type (wt)-MED12 leiomyoma (P < 0.05). The mRNA levels of other tryptophan metabolizing enzymes, IDO1 and IDO2, were low and not significantly different, suggesting that TDO2 is the key enzyme responsible for reduced tryptophan levels in mut-MED12 leiomyoma. R5020 and medroxyprogesterone acetate (MPA), two progesterone agonists, regulated TDO2 gene expression in primary myometrial and leiomyoma cells expressing wt-MED12; however, this effect was absent or blunted in leiomyoma cells expressing G44D mut-MED12. These data suggest that MED12 mutation may alter progesterone-mediated TDO2 expression in leiomyoma, leading to lower levels of tryptophan in mut-MED12 leiomyoma. This highlights that fibroids can vary widely in their response to progesterone as a result of mutation status and provides some insight for understanding the effect of tryptophan-kynurenine pathway on leiomyoma tumorigenesis and identifying targeted interventions for fibroids based on their distinct molecular signatures.

Long Noncoding RNA MIAT Modulates the Extracellular Matrix Deposition in Leiomyomas by Sponging MiR-29 Family

The objective of this study was to determine the expression and functional role of a long noncoding RNA (lncRNA) MIAT (myocardial infarction-associated transcript) in leiomyoma pathogenesis. Leiomyoma compared with myometrium (n = 66) expressed significantly more MIAT that was independent of race/ethnicity and menstrual cycle phase but dependent on MED12 (mediator complex subunit 12) mutation status. Leiomyomas bearing the MED12 mutation expressed higher levels of MIAT and lower levels of microRNA 29 family (miR-29a, -b, and -c) compared with MED12 wild-type leiomyomas. Using luciferase reporter activity and RNA immunoprecipitation analysis, MIAT was shown to sponge the miR-29 family. In a 3-dimensional spheroid culture system, transient transfection of MIAT siRNA in leiomyoma smooth muscle cell (LSMC) spheroids resulted in upregulation of miR-29 family and downregulation of miR-29 targets, collagen type I (COL1A1), collagen type III (COL3A1), and TGF-β3 (transforming growth factor β-3). Treatment of LSMC spheroids with TGF-β3 induced COL1A1, COL3A1, and MIAT levels, but repressed miR-29 family expression. Knockdown of MIAT in LSMC spheroids blocked the effects of TGF-β3 on the induction of COL1A1 and COL3A1 expression. Collectively, these results underscore the physiological significance of MIAT in extracellular matrix accumulation in leiomyoma.