Prostate cancer (PCa) risk-associated SNPs are enriched in noncoding cis-regulatory elements (rCREs), yet their modi operandi and clinical impact remain elusive. Here, we perform CRISPRi screens of ...260 rCREs in PCa cell lines. We find that rCREs harboring high risk SNPs are more essential for cell proliferation and H3K27ac occupancy is a strong indicator of essentiality. We also show that cell-line-specific essential rCREs are enriched in the 8q24.21 region, with the rs11986220-containing rCRE regulating MYC and PVT1 expression, cell proliferation and tumorigenesis in a cell-line-specific manner, depending on DNA methylation-orchestrated occupancy of a CTCF binding site in between this rCRE and the MYC promoter. We demonstrate that CTCF deposition at this site as measured by DNA methylation level is highly variable in prostate specimens, and observe the MYC eQTL in the 8q24.21 locus in individuals with low CTCF binding. Together our findings highlight a causal mechanism synergistically driven by a risk SNP and DNA methylation-mediated 3D genome architecture, advocating for the integration of genetics and epigenetics in assessing risks conferred by genetic predispositions.
Chromatin-mediated processes influence the development and progression of breast cancer. Using murine mammary carcinoma-derived tumorspheres as a functional readout for an aggressive breast cancer ...phenotype, we performed a loss-of-function screen targeting 60 epigenetic regulators. We identified the Polycomb protein Cbx8 as a key regulator of mammary carcinoma both in vitro and in vivo. Accordingly, Cbx8 is overexpressed in human breast cancer and correlates with poor survival. Our genomic analyses revealed that Cbx8 positively regulates Notch signaling by maintaining H3K4me3 levels on Notch-network gene promoters. Ectopic expression of Notch1 partially rescues tumorsphere formation in Cbx8-depleted cells. We find that Cbx8 associates with non-PRC1 complexes containing the H3K4 methyltransferase complex component WDR5, which together regulate Notch gene expression. Thus, our study implicates a key non-canonical role for Cbx8 in promoting breast tumorigenesis.
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•RNAi screen in sphere culture identifies Cbx8 in promoting breast cancer•Cbx8 is upregulated in human breast cancer and correlates with poor survival•Cbx8 promotes mammary tumors in vivo via Notch pathway activation•Cbx8 cooperates with Wdr5 to sustain Notch expression by regulating H3K4me3
Perturbed chromatin modification programs play an important role in tumor biology. Chung et al. perform a tumorsphere RNAi screen and find that the Polycomb protein Cbx8 promotes breast tumorigenesis. Cbx8 cooperates with Wdr5 in a non-canonical fashion to maintain H3K4me3 and transcription of Notch-network gene loci.
Histone lysine acylation, including acetylation and crotonylation, plays a pivotal role in gene transcription in health and diseases. However, our understanding of histone lysine acylation has been ...limited to gene transcriptional activation. Here, we report that histone H3 lysine 27 crotonylation (H3K27cr) directs gene transcriptional repression rather than activation. Specifically, H3K27cr in chromatin is selectively recognized by the YEATS domain of GAS41 in complex with SIN3A-HDAC1 co-repressors. Proto-oncogenic transcription factor MYC recruits GAS41/SIN3A-HDAC1 complex to repress genes in chromatin, including cell-cycle inhibitor p21. GAS41 knockout or H3K27cr-binding depletion results in p21 de-repression, cell-cycle arrest, and tumor growth inhibition in mice, explaining a causal relationship between GAS41 and MYC gene amplification and p21 downregulation in colorectal cancer. Our study suggests that H3K27 crotonylation signifies a previously unrecognized, distinct chromatin state for gene transcriptional repression in contrast to H3K27 trimethylation for transcriptional silencing and H3K27 acetylation for transcriptional activation.
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•H3 lysine 27 crotonylation is a chromatin state for gene transcriptional repression•GAS41 YEATS domain recognizes H3 lysine 27 crotonylation and proto-oncogenic MYC•GAS41 and MYC amplification likely causes p21 downregulation in colorectal cancer
Nan et al. demonstrate that GAS41 through its YEAST domain recognizes histone H3 lysine 27 (H3K27) crotonylation and is recruited by proto-oncogenic MYC to SIN3A-HDAC1 co-repressors to repress gene transcription. These results suggest that H3K27 crotonylation, trimethylation, and acetylation represent distinct chromatin states for transcriptional repression, silencing, and activation, respectively.
Metastases can originate from disseminated tumour cells (DTCs), which may be dormant for years before reactivation. Here we find that the orphan nuclear receptor NR2F1 is epigenetically upregulated ...in experimental head and neck squamous cell carcinoma (HNSCC) dormancy models and in DTCs from prostate cancer patients carrying dormant disease for 7-18 years. NR2F1-dependent dormancy is recapitulated by a co-treatment with the DNA-demethylating agent 5-Aza-C and retinoic acid across various cancer types. NR2F1-induced quiescence is dependent on SOX9, RARβ and CDK inhibitors. Intriguingly, NR2F1 induces global chromatin repression and the pluripotency gene NANOG, which contributes to dormancy of DTCs in the bone marrow. When NR2F1 is blocked in vivo, growth arrest or survival of dormant DTCs is interrupted in different organs. We conclude that NR2F1 is a critical node in dormancy induction and maintenance by integrating epigenetic programmes of quiescence and survival in DTCs.
Ocular surface disease in glaucoma patients is a significant ocular co-morbidity that can affect 40% to 59% of these patients worldwide. The current study was aimed at evaluating the potential ...clinical benefit of an intense pulsed light (IPL)-based treatment in glaucomatous patients with ocular surface disease due to prolonged hypotensive eyedrop treatments. To our knowledge, this is the first series analyzing the therapeutic effect of this treatment option in this type of patients.
This non-comparative prospective case series study enrolled a total of 30 glaucoma patients ranging in age from 57 to 94 years old and treated with hypotensive eyedrops for years with dry eye symptomatology. All patients received four sessions of IPL treatment using the Optima IPL system (Lumenis, Yokneam, Israel) adjusted to the official optimized Lumenis setting. Changes in symptomatology, corneal staining, conjunctival hyperemia, non-invasive break-up time (NIBUT), tear osmolarity, tear meniscus height (TMH), meiboscore and meibomian gland expressibility was analyzed after treatment.
Statistically significant reductions were observed after IPL treatment in the symptomatology scores measured with different questionnaires ocular surface disease index (OSDI), standard patient evaluation of eye dryness (SPEED) and symptom assessment questionnaire in dry eye (SANDE) as well as with the visual analogue scale (P < 0.001). Mean change in OSDI was - 15.0 ± 11.3. A significant reduction was found after treatment in the corneal staining score (P < 0.001). A significant reduction was found in tear film meniscus height (P = 0.012), as well as in tear film osmolarity (P = 0.001). A significant reduction was also found in meibomian gland expressibility (P = 0.003), changing the percentage of grade 3 eyes from 44.4% before IPL to 17.2% after treatment.
IPL therapy combined with meibomian gland expression (MGX) seems to be an effective option to improve symptomatology in glaucomatous patients with ocular surface disease due to prolonged hypotensive eyedrop treatments, with an additional improvement in clinical signs, such as tear osmolarity and corneal staining.
Retinoic acid signaling plays key roles in embryonic development and in maintaining the differentiated status of adult tissues. Recently, the nuclear retinoic acid receptor (RAR) isotypes α, β and γ ...were found to play specific functions in the expansion and differentiation of the stem compartments of various tissues. For instance, RARγ appears to be involved in stem cell compartment expansion, while RARα and RARβ are implicated in the subsequent cell differentiation. We found that over-expressing c-Myc in normal mouse mammary epithelium and in a c-Myc-driven transgenic model of mammary cancer, disrupts the balance between RARγ and RARα/β in favor of RARγ.
The effects of c-Myc on RAR isotype expression were evaluated in normal mouse mammary epithelium, mammary tumor cells obtained from the MMTV-Myc transgenic mouse model as well as human normal immortalized breast epithelial and breast cancer cell lines. The in vivo effect of the RARα-selective agonist 4-(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthyl)carboxamidobenzoic acid (Am580) was examined in the MMTV-Myc mouse model of mammary tumorigenesis.
Modulation of the RARα/β to RARγ expression in mammary glands of normal mice, oncomice, and human mammary cell lines through the alteration of RAR-target gene expression affected cell proliferation, survival and tumor growth. Treatment of MMTV-Myc mice with the RARα-selective agonist Am580 led to significant inhibition of mammary tumor growth (~90%, P<0.001), lung metastasis (P<0.01) and extended tumor latency in 63% of mice. Immunocytochemical analysis showed that in these mice, RARα responsive genes such as Cyp26A1, E-cadherin, cellular retinol-binding protein 1 (CRBP1) and p27, were up-regulated. In contrast, the mammary gland tumors of mice that responded poorly to Am580 treatment (37%) expressed significantly higher levels of RARγ. In vitro experiments indicated that the rise in RARγ was functionally linked to promotion of tumor growth and inhibition of differentiation. Thus, activation of the RARα pathway is linked to tumor growth inhibition, differentiation and cell death.
The functional consequence of the interplay between c-Myc oncogene expression and the RARγ to RARα/β balance suggests that prevalence of RARγ over-RARα/β expression levels in breast cancer accompanied by c-Myc amplification or over-expression in breast cancer should be predictive of response to treatment with RARα-isotype-specific agonists and warrant monitoring during clinical trials.
Triple negative breast cancer (TNBC) frequently relapses locally, regionally or as systemic metastases. Development of targeted therapy that offers significant survival benefit in TNBC is an unmet ...clinical need. We have previously reported that blocking interactions between PAH2 domain of chromatin regulator Sin3A and the Sin3 interaction domain (SID) containing proteins by SID decoys result in EMT reversal, and re-expression of genes associated with differentiation. Here we report a novel and therapeutically relevant combinatorial use of SID decoys. SID decoys activate RARα/β pathways that are enhanced in combination with RARα-selective agonist AM80 to induce morphogenesis and inhibit tumorsphere formation. These findings correlate with inhibition of mammary hyperplasia and a significant increase in tumor-free survival in MMTV-Myc oncomice treated with a small molecule mimetic of SID (C16). Further, in two well-established mouse TNBC models we show that treatment with C16-AM80 combination has marked anti-tumor effects, prevents lung metastases and seeding of tumor cells to bone marrow. This correlated to a remarkable 100% increase in disease-free survival with a possibility of "cure" in mice bearing a TNBC-like tumor. Targeting Sin3A by C16 alone or in combination with AM80 may thus be a promising adjuvant therapy for treating or preventing metastatic TNBC.
In early stages of metastasis malignant cells must acquire phenotypic changes to enhance their migratory behavior and their ability to breach the matrix surrounding tumors and blood vessel walls. ...Epigenetic regulation of gene expression allows the acquisition of these features that, once tumoral cells have escape from the primary tumor, can be reverted. Here we report that the expression of the Polycomb epigenetic repressor Ring1B is enhanced in tumoral cells that invade the stroma in human ductal breast carcinoma and its expression is coincident with that of Fak in these tumors. Ring1B knockdown in breast cancer cell lines revealed that Ring1B is required to sustain Fak expression in basal conditions as well as in Tgfβ-treated cells. Functionally, endogenous Ring1B is required for cell migration and invasion in vitro and for in vivo invasion of the mammary fat pad by tumoral cells. Finally we identify p63 as a target of Ring1B to regulate Fak expression: Ring1B depletion results in enhanced p63 expression, which in turns represses Fak expression. Importantly, Fak downregulation upon Ring1B depletion is dependent on p63 expression. Our findings provide new insights in the biology of the breast carcinoma and open new avenues for breast cancer prognosis and therapy.
Introduction Retinoic acid signaling plays key roles in embryonic development and in maintaining the differentiated status of adult tissues. Recently, the nuclear retinoic acid receptor (RAR) ...isotypes alpha, beta and gamma were found to play specific functions in the expansion and differentiation of the stem compartments of various tissues. For instance, RARgamma appears to be involved in stem cell compartment expansion, while RARalpha and RARbeta are implicated in the subsequent cell differentiation. We found that over-expressing c-Myc in normal mouse mammary epithelium and in a c-Myc-driven transgenic model of mammary cancer, disrupts the balance between RARgamma and RARalpha/beta in favor of RARgamma. Methods The effects of c-Myc on RAR isotype expression were evaluated in normal mouse mammary epithelium, mammary tumor cells obtained from the MMTV-Myc transgenic mouse model as well as human normal immortalized breast epithelial and breast cancer cell lines. The in vivo effect of the RARalpha-selective agonist 4-(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthyl)carboxamidobenzoic acid (Am580) was examined in the MMTV-Myc mouse model of mammary tumorigenesis. Results Modulation of the RARalpha/beta to RARgamma expression in mammary glands of normal mice, oncomice, and human mammary cell lines through the alteration of RAR-target gene expression affected cell proliferation, survival and tumor growth. Treatment of MMTV-Myc mice with the RARalpha-selective agonist Am580 led to significant inhibition of mammary tumor growth (~90%, P<0.001), lung metastasis (P<0.01) and extended tumor latency in 63% of mice. Immunocytochemical analysis showed that in these mice, RARalpha responsive genes such as Cyp26A1, E-cadherin, cellular retinol-binding protein 1 (CRBP1) and p27, were up-regulated. In contrast, the mammary gland tumors of mice that responded poorly to Am580 treatment (37%) expressed significantly higher levels of RARgamma. In vitro experiments indicated that the rise in RARgamma was functionally linked to promotion of tumor growth and inhibition of differentiation. Thus, activation of the RARalpha pathway is linked to tumor growth inhibition, differentiation and cell death. Conclusions The functional consequence of the interplay between c-Myc oncogene expression and the RARgamma to RARalpha/beta balance suggests that prevalence of RARgamma over-RARalpha/beta expression levels in breast cancer accompanied by c-Myc amplification or over-expression in breast cancer should be predictive of response to treatment with RARalpha-isotype-specific agonists and warrant monitoring during clinical trials. See related editorial by Garattini et al
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![Reversal by RAR[alpha] agon...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/1465-5411/small "Reversal by RAR[alpha] agonist Am580 of c-Myc-induced imbalance in RAR[alpha]/RAR[gamma] expression during MMTV-Myc tumorigenesis")