Nigel P. Mongan

Increased Expression of the Polycomb Group Gene, EZH2, in Transitional Cell Carcinoma of the Bladder

Purpose: The Polycomb group gene, EZH2, functions as a transcriptional repressor involved in gene silencing. Amplification of EZH2 has been reported in several malignancies, including prostate, breast, and lymphoma. We evaluated EZH2 mRNA and protein expression in bladder specimens from patients and the EZH2 mRNA expression in five bladder cancer cell lines. Experimental Design:EZH2 mRNA expression was assessed by reverse transcription-PCR (RT-PCR) in 38 bladder tissue specimens. We also evaluated 39 bladder cancer specimens for EZH2 protein expression using immunohistochemistry with affinity-purified antibodies to human EZH2. In addition, five human bladder cancer cell lines were analyzed by RT-PCR for EZH2 mRNA expression. Results: Five of 14 (36%) nontumor bladder specimens versus 21 of 24 (88%) bladder tumors showed EZH2 mRNA expression (P = 0.003). All of the invasive tumors (10 of 10) had detectable EZH2 mRNA expression, compared with 11 of 14 (79%) superficial tumors. In addition, EZH2 mRNA expression was noted in 100% (16 of 16) of high-grade bladder tumors versus 50% (4 of 8) of low-grade tumors (P = 0.01). EZH2 protein expression, meanwhile, was increased in neoplastic tissue compared with nontumor urothelium (78% versus 69% of nuclei, P < 0.005). There were no differences in EZH2 protein levels between superficial and invasive tumors. High-grade tumors had increased EZH2 staining compared with normal urothelium (78% versus 68%, P < 0.005), whereas low-grade lesions did not. Four of five human bladder cancer cell lines expressed high levels of EZH2, whereas only low levels were detected in one cell line. Conclusions: We report a significant increase in EZH2 expression in transitional cell carcinoma of the bladder compared with normal urothelium. These data suggest that similar to other human malignancies, increased EZH2 expression correlates with oncogenesis of the bladder.

Role of androgen receptor and associated lysine‐demethylase coregulators, LSD1 and JMJD2A, in localized and advanced human bladder cancer

Bladder cancer is approximately three times more common in men as compared to women. We and others have previously investigated the contribution of androgens and the androgen receptor (AR) to bladder cancer. JMJD2A and LSD1 are recently discovered AR coregulator proteins that mediate AR‐dependent transcription via recently described histone lysine‐demethylation (KDM) mechanisms. We used immunohistochemistry to examine JMJD2A, LSD1, and AR expression in 72 radical cystectomy specimens, resulting in evaluation of 129 tissue samples (59 urothelial carcinoma, 70 benign). We tested levels of these proteins for statistical association with clinicopathologic variables and patient survival. Expression of these markers was also assessed in human bladder cancer cell lines. The effects of pharmacological inhibition of LSD1 on the proliferation of these bladder cancer cells was determined. JMJD2A and AR levels were significantly lower in malignant versus benign urothelium, while increased LSD1 levels were observed in malignant urothelium relative to benign. A significant reduction in all three proteins occurred with cancer stage progression, including muscle invasion (JMJD2A/LSD1/AR), extravesical extension (JMJD2A/LSD1), and lymph node metastasis (JMJD2A/AR). Lower JMJD2A intensity correlated with additional poor prognostic features, including lymphovascular invasion, concomitant carcinoma in situ and tobacco usage, and predicted significantly worse overall survival. Pharmacological inhibition of LSD1 suppressed bladder cancer cell proliferation and androgen‐induced transcription. Our results support a novel role for the AR–KDM complex in bladder cancer initiation and progression, identify JMJD2A as a promising prognostic biomarker, and demonstrate targeting of the KDM activity as an effective potential approach for bladder cancer growth inhibition.

m6A potentiates Sxl alternative pre-mRNA splicing for robust Drosophila sex determination

N6-methyladenosine (m6A) is the most common internal modification of eukaryotic messenger RNA (mRNA) and is decoded by YTH domain proteins. The mammalian mRNA m6A methylosome is a complex of nuclear proteins that includes METTL3 (methyltransferase-like 3), METTL14, WTAP (Wilms tumour 1-associated protein) and KIAA1429. Drosophila has corresponding homologues named Ime4 and KAR4 (Inducer of meiosis 4 and Karyogamy protein 4), and Female-lethal (2)d (Fl(2)d) and Virilizer (Vir). In Drosophila, fl(2)d and vir are required for sex-dependent regulation of alternative splicing of the sex determination factor Sex lethal (Sxl). However, the functions of m6A in introns in the regulation of alternative splicing remain uncertain. Here we show that m6A is absent in the mRNA of Drosophila lacking Ime4. In contrast to mouse and plant knockout models, Drosophila Ime4-null mutants remain viable, though flightless, and show a sex bias towards maleness. This is because m6A is required for female-specific alternative splicing of Sxl, which determines female physiognomy, but also translationally represses male-specific lethal 2 (msl-2) to prevent dosage compensation in females. We further show that the m6A reader protein YT521-B decodes m6A in the sex-specifically spliced intron of Sxl, as its absence phenocopies Ime4 mutants. Loss of m6A also affects alternative splicing of additional genes, predominantly in the 5′ untranslated region, and has global effects on the expression of metabolic genes. The requirement of m6A and its reader YT521-B for female-specific Sxl alternative splicing reveals that this hitherto enigmatic mRNA modification constitutes an ancient and specific mechanism to adjust levels of gene expression.

Mutations in ZMYND10, a Gene Essential for Proper Axonemal Assembly of Inner and Outer Dynein Arms in Humans and Flies, Cause Primary Ciliary Dyskinesia

Primary ciliary dyskinesia (PCD) is a ciliopathy characterized by airway disease, infertility, and laterality defects, often caused by dual loss of the inner dynein arms (IDAs) and outer dynein arms (ODAs), which power cilia and flagella beating. Using whole-exome and candidate-gene Sanger resequencing in PCD-affected families afflicted with combined IDA and ODA defects, we found that 6/38 (16%) carried biallelic mutations in the conserved zinc-finger gene BLU (ZMYND10). ZMYND10 mutations conferred dynein-arm loss seen at the ultrastructural and immunofluorescence level and complete cilia immotility, except in hypomorphic p.Val16Gly (c.47T>G) homozygote individuals, whose cilia retained a stiff and slowed beat. In mice, Zmynd10 mRNA is restricted to regions containing motile cilia. In a Drosophila model of PCD, Zmynd10 is exclusively expressed in cells with motile cilia: chordotonal sensory neurons and sperm. In these cells, P-element-mediated gene silencing caused IDA and ODA defects, proprioception deficits, and sterility due to immotile sperm. Drosophila Zmynd10 with an equivalent c.47T>G (p.Val16Gly) missense change rescued mutant male sterility less than the wild-type did. Tagged Drosophila ZMYND10 is localized primarily to the cytoplasm, and human ZMYND10 interacts with LRRC6, another cytoplasmically localized protein altered in PCD. Using a fly model of PCD, we conclude that ZMYND10 is a cytoplasmic protein required for IDA and ODA assembly and that its variants cause ciliary dysmotility and PCD with laterality defects.

Valproic acid, in combination with all-trans retinoic acid and 5-aza-2′-deoxycytidine, restores expression of silenced RARβ2 in breast cancer cells

Epigenetic silencing of tumor suppressor genes has been established as an important process of carcinogenesis. The retinoic acid (RA) receptor β2 (RARβ2) gene is one such tumor suppressor gene often silenced during carcinogenesis. The combined use of histone deacetylase and DNA methyltransferase inhibitors has been shown to reverse the epigenetic silencing of numerous growth regulatory genes. Valproic acid (VPA), which has long been used in the treatment of epilepsy, was shown recently to be an effective histone deacetylase inhibitor that can induce differentiation of neoplastically transformed cells. In this study, we show for the first time that VPA, in combination with RA and the DNA methyltransferase inhibitor 5-aza-2′-deoxycytidine (Aza-dC), can overcome the epigenetic barriers to transcription of a prototypical silenced tumor suppressor gene, RARβ2, in human breast cancer cells. Chromatin immunoprecipitation assays show that the combination of VPA, RA, and Aza-dC increases histone acetylation at the silenced RARβ2 promoter of MCF-7 breast cancer cells. Furthermore, reverse transcription-PCR analyses reveal cell type–specific effects in the actions of VPA on RARβ2 expression in cultured human breast cancer cells. Finally, we show that VPA, in combination with RA and Aza-dC, inhibits the proliferation of both estrogen receptor α-positive (MCF-7) and estrogen receptor α-negative (MDA-MB-231) breast cancer cell lines. These data suggest that VPA may ultimately be useful in combination therapies in the treatment of human breast cancers.

The putative human stem cell marker, Rex-1 (Zfp42): structural classification and expression in normal human epithelial and carcinoma cell cultures.

Human Rex‐1 (hRex‐1) (also referred to as zinc‐finger protein‐42, Zfp42) encodes a zinc finger protein expression of which is believed to be characteristic of pluripotent stem cells. We have applied bioinformatics to classify the relationship of human, rat, and mouse REX1 proteins in the C2H2 family of zinc finger proteins and demonstrate that REX1 is a member of the YY1 sub‐family of transcription factors, which includes the Drosophila pleiohomeotic (Pho) protein. We have generated a molecular model of the human REX1 zinc finger domains based on the crystal structure of the YY1 transcription factor. To date, expression of hRex‐1 and its extensively studied mouse homolog mRex‐1, has been reported only in embryonic and adult stem cells and in differentiated spermatocytes. In this study, reverse transcription‐PCR and Western analysis were employed to assay for hRex‐1 expression in cultured normal human epithelial cells and human carcinoma cell lines. Expression of hRex‐1 mRNA was detected in normal human epidermal keratinocytes, normal prostate epithelial cells (PrEC), bronchial, and small airway lung epithelial cells. Other stem cell markers, such as Oct 4, DAB2, and cMyc were also detected in normal human epidermal keratinocyte cultures. Expression of hRex‐1 was also detected in some human tumor cell lines including MDA‐MB‐468 mammary carcinoma, SCC‐15 head and neck squamous cell carcinoma, and N‐TERA2 human teratocarcinoma cells. Western analyses confirmed expression of the human REX1 (ZFP42) protein in MDA‐MB‐468 cells and normal human keratinocytes. This research has identified model human cell culture systems, in addition to embryonic stem (ES) cells, in which Rex‐1 is expressed, and this should enable the characterization of REX1 functions in normal adult epithelial cells and tumorigenic stem cells.

Overcoming Drug Resistance and Treating Advanced Prostate Cancer.

Most of the prostate cancers (PCa) in advanced stage will progress to castration-resistant prostate cancer (CRPC). Within CRPC group, 50-70% of the patients will develop bone metastasis in axial and other regions of the skeleton. Once PCa cells spread to the bone, currently, no treatment regimens are available to eradicate the metastasis, and cancer-related death becomes inevitable. In 2012, it is estimated that there will be 28,170 PCa deaths in the United States. Thus, PCa bone metastasis-associated clinical complications and treatment resistance pose major clinical challenges. In this review, we will present recent findings on the molecular and cellular pathways that are responsible for bone metastasis of PCa. We will address several novel mechanisms with a focus on the role of bone and bone marrow microenvironment in promoting PCa metastasis, and will further discuss why prostate cancer cells preferentially metastasize to the bone. Additionally, we will discuss novel roles of several key pathways, including angiogenesis and extracellular matrix remodeling in bone marrow and stem cell niches with their relationship to PCa bone metastasis and poor treatment response. We will evaluate how various chemotherapeutic drugs and radiation therapies may allow aggressive PCa cells to gain advantageous mutations leading to increased survival and rendering the cancer cells to become resistant to treatment. The novel concept relating several key survival and invasion signaling pathways to stem cell niches and treatment resistance will be reviewed. Lastly, we will provide an update of several recently developed novel drug candidates that target metastatic cancer microenvironments or niches, and discuss the advantages and significance provided by such therapeutic approaches in pursuit of overcoming drug resistance and treating advanced PCa.

The lysine specific demethylase‐1 (LSD1/KDM1A) regulates VEGF‐A expression in prostate cancer

Recurrent prostate cancer remains a major clinical challenge. The lysine specific demethylase‐1 (LSD1/KDM1A), together with the JmjC domain‐containing JMJD2A and JMJD2C proteins, have emerged as critical regulators of histone lysine methylation. The LSD1–JMJD2 complex functions as a transcriptional co‐regulator of hormone activated androgen and estrogen receptors at specific gene promoters. LSD1 also regulates DNA methylation and p53 function. LSD1 is overexpressed in numerous cancers including prostate cancer through an unknown mechanism. We investigated expression of the LSD1 and JMJD2A in malignant human prostate specimens. We correlated LSD1 and JMJD2A expression with known mediators of prostate cancer progression: VEGF‐A and cyclin A1. We show that elevated expression of LSD1, but not JMJD2A, correlates with prostate cancer recurrence and with increased VEGF‐A expression. We show that functional depletion of LSD1 expression using siRNA in prostate cancer cells decreases VEGF‐A and blocks androgen induced VEGF‐A, PSA and Tmprss2 expression. We demonstrate that pharmacological inhibition of LSD1 reduces proliferation of both androgen dependent (LnCaP) and independent cell lines (LnCaP: C42, PC3). We show a direct mechanistic link between LSD1 over‐expression and increased activity of pro‐angiogenic pathways. New therapies targeting LSD1 activity should be useful in the treatment of hormone dependent and independent prostate cancer.

Phase 1/2 clinical trial of interferon α2b and weekly liposome-encapsulated all-trans retinoic acid in patients with advanced renal cell carcinoma

To evaluate the feasibility, efficacy, and biologic effects of weekly liposome-encapsulated all-trans retinoic acid (ATRA-IV) plus interferon α2b (IFN) in patients with advanced renal cell carcinoma (RCC). Twenty-six patients with metastatic RCC were treated on a phase 1/2 trial with weekly ATRA-IV and IFN SQ daily 5 d/wk. Twelve patients received ATRA-IV at three dose levels (60, 75, and 90 mg/m2) according to phase 1 methodology, and 14 additional patients received 90 mg/m2. Response was assessed according to an intention-to-treat analysis. Serum retinoic acid (RA) concentrations were assayed and peripheral blood mononuclear cell mRNA expression of RA and IFN-inducible genes (RARα, RARβ2, IRF1, CRABP2, and TRAIL) were examined. No dose limiting toxicities occurred at 60 mg/m2; grade 3 leukopenia affected 1/6 patients at 75 mg/m2, whereas 3 patients received 90 mg/m2 without a dose limiting toxicities. Fourteen additional patients received 90 mg/m2 ATRA-IV without grade 3/4 toxicity. Five of 26 (19%) patients achieved a major response, with a median duration of 14 months (range 9 to 23); 9 additional patients (41%) demonstrated stable disease or minor response lasting ≥4 months. No significant differences in serum (RA) after ATRA infusion were detected between weeks 1 and 8 of treatment. Peripheral blood mononuclear cell mRNA expression did not correlate with clinical response. The addition of weekly ATRA-IV to IFN therapy is feasible and well tolerated, resulting in sustainable increased serum (RA). This regimen demonstrates antitumor activity in metastatic RCC, and suggests ATRA-IV augments IFN therapy.

The role of HIF1α in renal cell carcinoma tumorigenesis

The transcription factor HIF1α is implicated in the development of clear cell renal cell carcinoma (ccRCC). Although HIF1α was initially believed to be essential for ccRCC development, recent studies hypothesize an oncogenic role for HIF2α in ccRCC, but a tumor suppressor role for HIF1α [1], leading to uncertainty as to the precise roles of the different HIF transcription factors in this disease. Using evidence available from studies with human ccRCC cell lines, mouse xenografts, murine models of ccRCC, and human ccRCC specimens, we evaluate the roles of HIF1α and HIF2α in the pathogenesis of ccRCC. We present a convergence of clinical and mechanistic data supporting an important role for HIF1α in promoting tumorigenesis in a clinically important and large subset of ccRCC. This indicates that current understanding of the exact roles of HIF1α and HIF2α is incomplete and that further research is required to determine the diverse roles of HIF1α and HIF2α in ccRCC.Key messagesThe TRACK mouse ccRCC model with constitutively active HIF1α but not HIF2α expressed in proximal tubules develops RCC.HIF1α protein is expressed in the majority of human ccRCC specimens.Elevated HIF1α in ccRCC correlates with a worse prognosis.Many publications do not support a tumor suppressor role for HIF1α in ccRCC.HIF1α, but not HIF2α, is expressed in some types of cancer stem cells.