Human WDR5 promotes breast cancer growth and metastasis via KMT2-independent translation regulation

Metastatic breast cancer remains a major cause of cancer-related deaths in women, and there are few effective therapies against this advanced disease. Emerging evidence suggests that key steps of tumor progression and metastasis are controlled by reversible epigenetic mechanisms. Using an in vivo genetic screen, we identified WDR5 as an actionable epigenetic regulator that is required for metastatic progression in models of triple-negative breast cancer. We found that knockdown of WDR5 in breast cancer cells independently impaired their tumorigenic as well as metastatic capabilities. Mechanistically, WDR5 promotes cell growth by increasing ribosomal gene expression and translation efficiency in a KMT2-independent manner. Consistently, pharmacological inhibition or degradation of WDR5 impedes cellular translation rate and the clonogenic ability of breast cancer cells. Furthermore, a combination of WDR5 targeting with mTOR inhibitors leads to potent suppression of translation and proliferation of breast cancer cells. These results reveal novel therapeutic strategies to treat metastatic breast cancer.

Evaluation of prognostic risk models for postoperative pulmonary complications in adult patients undergoing major abdominal surgery: a systematic review and international external validation cohort study

BACKGROUND

Stratifying risk of postoperative pulmonary complications after major abdominal surgery allows clinicians to modify risk through targeted interventions and enhanced monitoring. In this study, we aimed to identify and validate prognostic models against a new consensus definition of postoperative pulmonary complications.

METHODS

We did a systematic review and international external validation cohort study. The systematic review was done in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We searched MEDLINE and Embase on March 1, 2020, for articles published in English that reported on risk prediction models for postoperative pulmonary complications following abdominal surgery. External validation of existing models was done within a prospective international cohort study of adult patients (≥18 years) undergoing major abdominal surgery. Data were collected between Jan 1, 2019, and April 30, 2019, in the UK, Ireland, and Australia. Discriminative ability and prognostic accuracy summary statistics were compared between models for the 30-day postoperative pulmonary complication rate as defined by the Standardised Endpoints in Perioperative Medicine Core Outcome Measures in Perioperative and Anaesthetic Care (StEP-COMPAC). Model performance was compared using the area under the receiver operating characteristic curve (AUROCC).

FINDINGS

In total, we identified 2903 records from our literature search; of which, 2514 (86·6%) unique records were screened, 121 (4·8%) of 2514 full texts were assessed for eligibility, and 29 unique prognostic models were identified. Nine (31·0%) of 29 models had score development reported only, 19 (65·5%) had undergone internal validation, and only four (13·8%) had been externally validated. Data to validate six eligible models were collected in the international external validation cohort study. Data from 11 591 patients were available, with an overall postoperative pulmonary complication rate of 7·8% (n=903). None of the six models showed good discrimination (defined as AUROCC ≥0·70) for identifying postoperative pulmonary complications, with the Assess Respiratory Risk in Surgical Patients in Catalonia score showing the best discrimination (AUROCC 0·700 [95% CI 0·683-0·717]).

INTERPRETATION

In the pre-COVID-19 pandemic data, variability in the risk of pulmonary complications (StEP-COMPAC definition) following major abdominal surgery was poorly described by existing prognostication tools. To improve surgical safety during the COVID-19 pandemic recovery and beyond, novel risk stratification tools are required.

FUNDING

British Journal of Surgery Society.

CECR2 drives breast cancer metastasis by promoting NF-κB signaling and macrophage-mediated immune suppression

Metastasis is the major cause of cancer-related deaths due to the lack of effective therapies. Emerging evidence suggests that certain epigenetic and transcriptional regulators drive cancer metastasis and could be targeted for metastasis treatment. To identify epigenetic regulators of breast cancer metastasis, we profiled the transcriptomes of matched pairs of primary breast tumors and metastases from human patients. We found that distant metastases are more immune inert with increased M2 macrophages compared to their matched primary tumors. The acetyl-lysine reader, cat eye syndrome chromosome region candidate 2 (CECR2), was the top up-regulated epigenetic regulator in metastases associated with an increased abundance of M2 macrophages and worse metastasis-free survival. CECR2 was required for breast cancer metastasis in multiple mouse models, with more profound effect in the immunocompetent setting. Mechanistically, the nuclear factor κB (NF-κB) family member v-rel avian reticuloendotheliosis viral oncogene homolog A (RELA) recruits CECR2 to increase chromatin accessibility and activate the expression of their target genes. These target genes include multiple metastasis-promoting genes, such as TNC, MMP2, and VEGFA, and cytokine genes CSF1 and CXCL1, which are critical for immunosuppression at metastatic sites. Consistent with these results, pharmacological inhibition of CECR2 bromodomain impeded NF-κB-mediated immune suppression by macrophages and inhibited breast cancer metastasis. These results reveal that targeting CECR2 may be a strategy to treat metastatic breast cancer.

KDM5B promotes immune evasion by recruiting SETDB1 to silence retroelements

Tumours use various strategies to evade immune surveillance^1,2. Immunotherapies targeting tumour immune evasion such as immune checkpoint blockade have shown considerable efficacy on multiple cancers^3,4 but are ineffective for most patients due to primary or acquired resistance^5-7. Recent studies showed that some epigenetic regulators suppress anti-tumour immunity^2,8-12, suggesting that epigenetic therapies could boost anti-tumour immune responses and overcome resistance to current immunotherapies. Here we show that, in mouse melanoma models, depletion of KDM5B-an H3K4 demethylase that is critical for melanoma maintenance and drug resistance^13-15-induces robust adaptive immune responses and enhances responses to immune checkpoint blockade. Mechanistically, KDM5B recruits the H3K9 methyltransferase SETDB1 to repress endogenous retroelements such as MMVL30 in a demethylase-independent manner. Derepression of these retroelements activates cytosolic RNA-sensing and DNA-sensing pathways and the subsequent type-I interferon response, leading to tumour rejection and induction of immune memory. Our results demonstrate that KDM5B suppresses anti-tumour immunity by epigenetic silencing of retroelements. We therefore reveal roles of KDM5B in heterochromatin regulation and immune evasion in melanoma, opening new paths for the development of KDM5B-targeting and SETDB1-targeting therapies to enhance tumour immunogenicity and overcome immunotherapy resistance.

PRMT6 Regulates RAS/RAF Binding and MEK/ERK-Mediated Cancer Stemness Activities in Hepatocellular Carcinoma through CRAF Methylation

Arginine methylation is a post-translational modification that plays pivotal roles in signal transduction and gene transcription during cell fate determination. We found protein methyltransferase 6 (PRMT6) to be frequently downregulated in hepatocellular carcinoma (HCC) and its expression to negatively correlate with aggressive cancer features in HCC patients. Silencing of PRMT6 promoted the tumor-initiating, metastasis, and therapy resistance potential of HCC cell lines and patient-derived organoids. Consistently, loss of PRMT6 expression aggravated liver tumorigenesis in a chemical-induced HCC PRMT6 knockout (PRMT6^-/-) mouse model. Integrated transcriptome and protein-protein interaction studies revealed an enrichment of genes implicated in RAS signaling and showed that PRMT6 interacted with CRAF on arginine 100, which decreased its RAS binding potential and altered its downstream MEK/ERK signaling. Our work describes a critical repressive function for PRMT6 in maintenance of HCC cells by regulating RAS binding and MEK/ERK signaling via methylation of CRAF on arginine 100.

Abstract 4479: Protein arginine methyltransferase PRMT6 regulates cancer stemness through CRAF methylation in hepatocellular carcinoma

Arginine methylation is a post-translational modification that plays pivotal roles in signal transduction and gene transcription during cell fate determination. We found protein methyltransferase 6 (PRMT6) to be frequently down-regulated in hepatocellular carcinoma (HCC) cells and its expression to negatively correlate with aggressive cancer features in HCC patients. Silencing of PRMT6 promoted the tumor-initiating, metastasis and therapy resistance potential of HCC cells. Consistently, loss of PRMT6 expression aggravated liver tumorigenesis in a DEN+CCL4 HCC induced PRMT6-/- mouse model. Integrated transcriptome and protein-protein interaction studies revealed an enrichment of genes implicated in RAS signaling and that PRMT6 interacted with CRAF, and likely other RAF family members, and their methylation at conserved arginine 100, negatively regulating its activity, and as a consequence resulting in enhanced MEK/ERK signaling. Our work uncovered a critical repressive function for PRMT6 in maintenance of HCC cells by regulating the MEK/ERK pathway via arginine methylation of RAF, providing a new avenue of molecular mechanism by which ERK mediated stemness in HCC cells are developed.

Citation Format: LH Chan, L Zhou, Kai Yu Ng, TL Wong, TK Lee, YP Ching, YF Yuan, D Xie, S Richard, MS Huen, XY Guan, S Ma. Protein arginine methyltransferase PRMT6 regulates cancer stemness through CRAF methylation in hepatocellular carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4479.

Abstract LB-139: PRMT6-dependent CRAF/ERK signaling regulates cancer stem cell plasticity in liver cancer

Hepatocellular carcinoma (HCC), the major type of liver cancer, remains one of the most prevalent and deadliest cancer types in the world. Contemporary challenge in treating HCC has been the common therapy resistance and recurrence after therapy, all of which have been reported to be associated with stem-like behavior of cancer cells. Our group has previously identified a functional liver cancer stem cell (CSC) subset marked by the CD133 cell surface phenotype. Utilizing a PCR array encompassing diverse human chromatin modifiers, protein arginine methyltransferase 6 (PRMT6) was found to be differentially down-regulated in CD133+ liver CSCs of human HCC cells as well as CD133 enriched chemoresistant hepatospheres as compared to their counterparts. Clinically, reduced PRMT6 expression was detected in HCC specimens and correlated with a higher risk of metastasis. PRMT6 negatively regulated diverse in vitro cancer stem cell properties of HCC cells including self-renewal, therapy resistance, metastasis and expression of CSC and pluripotency markers. In addition, PRMT6 also suppressed in vivo tumor initiation and serial transplantation. Surprising, contrary to its usual localization in the nucleus as a chromatin modification enzyme mediating histone H3R2 methylation, we found PRMT6 to be predominantly expressed in the cytoplasm in normal liver and HCC cells. Through tandem affinity purification and subsequent mass spectrometry profiling, we identified CRAF, a serine/threonine-protein kinase, as a novel cytoplasmic protein partner of PRMT6. Binding of PRMT6 to CRAF inhibited its kinase activity through site-specific arginine methylation, resulting in inhibition of ERK-mediated CSC plasticity in HCC, demonstrated through in vivo / in vitro methylation assays, kinase assay and functional rescue experiments with the ERK inhibitor U0126. The link between PRMT6, ERK and cancer stemness was further substantiated in primary human normal liver and HCC organoids with or without PRMT6 modulated. Taken together, we found PRMT6 to be down-regulated in the liver CSC subset and to be functionally involved in regulating liver CSC plasticity via an unprecedented role in the cytoplasm through suppression of CRAF/ERK cascade.

Citation Format: Lok Hei Chan, Lei Zhou, Kai Yu Ng, Tin Lok Wong, Stella Chai, Terence K Lee, Xin Yuan Guan, Yick Pang Ching, Chung Mau Lo, Kwan Man, Benedetta Artegiani, Hans Clevers, Helen H Yan, Suet Yi Leung, Stèphane Richard, Michael SY Huen, Stephanie Ma. PRMT6-dependent CRAF/ERK signaling regulates cancer stem cell plasticity in liver cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr LB-139. doi:10.1158/1538-7445.AM2017-LB-139

Abstract 2333: The tumor suppressive role of PRMT6 in regulating the pathogenesis of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most common primary malignancy of the liver. The overall 5-year survival rate of HCC patients remains at a dismal 15% due to late diagnosis, metastasis and frequent tumor relapse. The presence of cancer stem cells (CSCs) has been proposed to account partly for the challenge of treating HCC. Our group has previously identified CD133 as a functional CSC marker of HCC. By adopting a PCR array encompassing diverse human chromatin modifiers, protein arginine methyltransferase 6 (PRMT6) was found to be differentially down-regulated in CD133+ human HCC cells. 55.8% (43/77) of clinical HCC tumor tissues showed down-regulated PRMT6 expression and patients with reduced PRMT6 expression were at significant risk of disrupted tumor encapsulation and manifested vascular invasion. An antagonistic relationship between PRMT6 and CD133 was observed in HCC cells, while modulation of PRMT6 led to an inversely altered CD133 expression. PRMT6 knockdown in liver cancer cells induced morphological alterations, where extensive cytoplasmic stretching and filopodia-like projections were observed. Moreover, PRMT6 regulated cancer and stem cell-like properties in vitro and in vivo including proliferation, colony formation, invasion, migration, angiogenesis, self-renewal, chemo-sensitivity and tumor initiation. In addition, stable knockdown of CD133 in HCC cells did not alter PRMT6 expression levels, which suggested that PRMT6 is potentially functioning upstream of CD133. Ongoing studies are in progress to delineate the underlying mechanisms by which PRMT6 suppress HCC.

Citation Format: Lok Hei Chan, Kai Yu Ng, Stephanie Ma. The tumor suppressive role of PRMT6 in regulating the pathogenesis of hepatocellular carcinoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2333. doi:10.1158/1538-7445.AM2015-2333

Hedgehog signaling induces osteosarcoma development through Yap1 and H19 overexpression

Osteosarcoma is one of the most common bone tumors. However, the genetic basis for its pathogenesis remains elusive. Here, we investigated the roles of Hedgehog (Hh) signaling in osteosarcoma development. Genetically-engineered mice with ubiquitous upregulated Hh signaling specifically in mature osteoblasts develop focal bone overgrowth, which greatly resembles the early stage of osteosarcoma. However, these mice die within three months, which prohibits further analysis of tumor progression. We therefore generated a mouse model with partial upregulated Hh signaling in mature osteoblasts and crossed it into a p53 heterozygous background to potentiate tumor development. We found that these mutant mice developed malignant osteosarcoma with high penetrance. Isolated primary tumor cells were mainly osteoblastic and highly proliferative with many characteristics of human osteosarcomas. Allograft transplantation into immunocompromised mice displayed high tumorigenic potential. More importantly, both human and mouse tumor tissues express high level of yes-associated protein 1 (Yap1), a potent oncogene that is amplified in various cancers. We show that inhibition of Hh signaling reduces Yap1 expression and knockdown of Yap1 significantly inhibits tumor progression. Moreover, long non-coding RNA H19 is aberrantly expressed and induced by upregulated Hh signaling and Yap1 overexpression. Our results demonstrate that aberrant Hh signaling in mature osteoblasts is responsible for the pathogenesis of osteoblastic osteosarcoma through Yap1 and H19 overexpression.

The effect of Piper betel extract on the wound healing process in experimentally induced diabetic rats

BACKGROUND

Piper betel (PB) possesses antimicrobial, antifungal, antioxidant and wound healing properties due to its powerful antioxidant effect. Diabetes mellitus (DM) is a metabolic disorder which is associated with complications like impaired wound healing, nephropathy and neuropathy. The main aim of the study was to study the wound healing properties of PB.

MATERIALS AND METHODS

A total of 33 male Sprague-Dawley rats (250-300 g) were taken and divided into 3 groups: Group I (control) comprising of 14 rats; Group II (diabetic untreated) comprising of 9 rats; Group III (diabetic treated) comprising of 10 rats. After 10 days of acclimatization, the animals were fasted overnight and diabetes was induced by administration of streptozotocin (45 mg/Kg body weight in a single dose, through tail vein) to group II and III animals. Four 6 mm-diameter full thickness skin excision wounds were created and PB extract (50 mg diluted in 0.1 ml of normal saline) was applied locally for 10 days in group III. The group I and II received normal saline (0.1 ml) for 10 days. The total protein content and the wound contraction rate were determined.

RESULTS

The wound contraction rate of group III (35.03 +/- 2.96) was higher as compared to group II (18.40 +/- 3.87) with p = 0.014. The total protein content for group III was 106.39 +/- 4.46 as compared to group II (72.86 +/- 12.86) with p = 0.050.

CONCLUSION

PB acted as a protective agent in the early phase of wound healing by increasing total protein content and wound contraction rate.

In vivo study of response threshold in retinal degenerate model at different degenerate stages

Retinal prostheses are being developed to apply electrical stimulation to the retina in order to restore vision of individuals who suffer from diseases such as retinitis pigmentosa (RP) and aged related macular degeneration (AMD). Various electrical stimulus parameters have been extensively studied in both experimental and clinical settings. Both electrophysiological and psychophysical results have shown that outer retina disease exhibit higher stimulus threshold in one degenerate group versus the control group. Fewer studies have been conducted to investigate the change in threshold currents as a function of different degenerate stages. We propose to study the electrophysiological change in degenerate rat retinas by using an in vivo recording method. We recorded retinal-driven superior colliculus cells response in two control groups and four degenerate groups. Current pulses of seven different stimulus pulse durations were applied to the retinas to obtain strength duration curve per group. Preliminary results showed that for the postnatal (P) day 90 and 180 degenerate groups, threshold currents were not significantly different from the normal control group (P90 and P230). For P300 degenerate group, the threshold currents progressively increased. For P760 degenerate group, threshold currents were significantly elevated across all the stimulus pulse durations tested. Charge densities calculated for P760 degenerate group exceeded the safe limit of the stimulating electrode. Cell morphology in all control and degenerate groups is still under investigation for a correlation study.

Lithium isotope geochemistry and origin of Canadian shield brines

Hypersaline calcium/chloride shield brines are ubiquitous in Canada and areas of northern Europe. The major questions relating to these fluids are the origin of the solutes and the concentration mechanism that led to their extreme salinity. Many chemical and isotopic tracers are used to solve these questions. For example, lithium isotope systematics have been used recently to support a marine origin for the Yellowknife shield brine (Northwest Territories). While having important chemical similarities to the Yellowknife brine, shield brines from the Sudbury/Elliot Lake (Ontario) and Thompson/Snow Lake (Manitoba) regions, which are the focus of this study, exhibit contrasting lithium behavior. Brine from the Sudbury Victor mine has lithium concentrations that closely follow the sea water lithium-bromine concentration trajectory, as well as delta6Li values of approximately -28/1000. This indicates that the lithium in this brine is predominantly marine in origin with a relatively minor component of crustal lithium leached from the host rocks. In contrast, the Thompson/Snow Lake brine has anomalously low lithium concentrations, indicating that it has largely been removed from solution by alteration minerals. Furthermore, brine and nonbrine mine waters at the Thompson mine have large delta6Li variations of approximately 30/1000, which primarily reflects mixing between deep brine with delta6Li of -35 +/- 2/1000 and near surface mine water that has derived higher delta6Li values through interactions with their host rocks. The contrary behavior of lithium in these two brines shows that, in systems where it has behaved conservatively, lithium isotopes can distinguish brines derived from marine sources.

The rod-cone shift and its effect on ganglion cells in the cat's retina

We examined how several characteristics of cat retinal ganglion cells--receptive field size, spatial resolution, and centre-surround antagonism--change with background illumination. Spectral sensitivity was also measured to see how these changes depend on the rod-cone shift. The radius of the centre mechanism changed very little across the mesopic range. The absence of a change can be attributed to the connections rods make with cones, and to the small spatial spread of rods which connect to a cone. The highest spatial frequency to which a cell could respond dropped sharply with falling background illumination. This loss of spatial resolution is due partly to increasing receptive field size, and partly to loss of contrast gain. Centre-surround antagonism approached zero as background illumination fell. The loss of antagonism could have been due to either a change in the subtractive relationship between centre and surround, or due to a loss of surround strength relative to centre strength; the latter was shown to be the case.