Lay Guat Ng

Loss of tumor suppressor KDM6A amplifies PRC2-regulated transcriptional repression in bladder cancer and can be targeted through inhibition of EZH2

Bladder cancer with loss of KDM6A expression is vulnerable to inhibition of EZH2. Cancer’s loss is targeted therapy’s gain A demethylating protein called KDM6A is a known tumor suppressor, and its function is often lost in bladder cancer as a result of inactivating mutations. There is no way to directly target the loss of the tumor suppressor, but Ler et al. found another strategy to effectively treat tumors with this mutation. The authors demonstrated that KDM6A-deficient cells are dependent on the function of another protein, called EZH2. Small-molecule inhibitors of EZH2 were effective against KDM6A-null bladder cancer in multiple mouse models, paving the way for further development of these drugs. Trithorax-like group complex containing KDM6A acts antagonistically to Polycomb-repressive complex 2 (PRC2) containing EZH2 in maintaining the dynamics of the repression and activation of gene expression through H3K27 methylation. In urothelial bladder carcinoma, KDM6A (a H3K27 demethylase) is frequently mutated, but its functional consequences and therapeutic targetability remain unknown. About 70% of KDM6A mutations resulted in a total loss of expression and a consequent loss of demethylase function in this cancer type. Further transcriptome analysis found multiple deregulated pathways, especially PRC2/EZH2, in KDM6A-mutated urothelial bladder carcinoma. Chromatin immunoprecipitation sequencing analysis revealed enrichment of H3K27me3 at specific loci in KDM6A-null cells, including PRC2/EZH2 and their downstream targets. Consequently, we targeted EZH2 (an H3K27 methylase) and demonstrated that KDM6A-null urothelial bladder carcinoma cell lines were sensitive to EZH2 inhibition. Loss- and gain-of-function assays confirmed that cells with loss of KDM6A are vulnerable to EZH2. IGFBP3, a direct KDM6A/EZH2/H3K27me3 target, was up-regulated by EZH2 inhibition and contributed to the observed EZH2-dependent growth suppression in KDM6A-null cell lines. EZH2 inhibition delayed tumor onset in KDM6A-null cells and caused regression of KDM6A-null bladder tumors in both patient-derived and cell line xenograft models. In summary, our study demonstrates that inactivating mutations of KDM6A, which are common in urothelial bladder carcinoma, are potentially targetable by inhibiting EZH2.

Mutation signatures implicate aristolochic acid in bladder cancer development

BackgroundAristolochic acid (AA) is a natural compound found in many plants of the Aristolochia genus, and these plants are widely used in traditional medicines for numerous conditions and for weight loss. Previous work has connected AA-mutagenesis to upper-tract urothelial cell carcinomas and hepatocellular carcinomas. We hypothesize that AA may also contribute to bladder cancer.MethodsHere, we investigated the involvement of AA-mutagenesis in bladder cancer by sequencing bladder tumor genomes from two patients with known exposure to AA. After detecting strong mutational signatures of AA exposure in these tumors, we exome-sequenced and analyzed an additional 11 bladder tumors and analyzed publicly available somatic mutation data from a further 336 bladder tumors.ResultsThe somatic mutations in the bladder tumors from the two patients with known AA exposure showed overwhelming AA signatures. We also detected evidence of AA exposure in 1 out of 11 bladder tumors from Singapore and in 3 out of 99 bladder tumors from China. In addition, 1 out of 194 bladder tumors from North America showed a pattern of mutations that might have resulted from exposure to an unknown mutagen with a heretofore undescribed pattern of A > T mutations. Besides the signature of AA exposure, the bladder tumors also showed the CpG > TpG and activated-APOBEC signatures, which have been previously reported in bladder cancer.ConclusionsThis study demonstrates the utility of inferring mutagenic exposures from somatic mutation spectra. Moreover, AA exposure in bladder cancer appears to be more pervasive in the East, where traditional herbal medicine is more widely used. More broadly, our results suggest that AA exposure is more extensive than previously thought both in terms of populations at risk and in terms of types of cancers involved. This appears to be an important public health issue that should be addressed by further investigation and by primary prevention through regulation and education. In addition to opportunities for primary prevention, knowledge of AA exposure would provide opportunities for secondary prevention in the form of intensified screening of patients with known or suspected AA exposure.

A Multigene Assay Identifying Distinct Prognostic Subtypes of Clear Cell Renal Cell Carcinoma with Differential Response to Tyrosine Kinase Inhibition

Patients with clear cell renal cell carcinoma (ccRCC) have divergent survival outcomes and therapeutic responses, which may be determined by underlying molecular diversity. We aimed to develop a practical molecular assay that can identify subtypes with differential prognosis and response to targeted therapy. Whole-genome expression analysis of formalin-fixed paraffin-embedded (FFPE) material from 55 ccRCC patients was performed and two molecular subtypes with differential clinical outcomes were identified by hierarchical clustering. An eight-gene quantitative polymerase chain reaction assay for classification into two subtypes was developed for FFPE material. The primary objective was to assess assay performance by correlating ccRCC prognostic subtypes to cancer-specific survival (CSS) and, for patients receiving targeted therapy, radiologic response. In three validation cohorts, patients could be distinguished into prognostic subtypes with differential CSS (Singapore General Hospital FFPE cohort: n = 224; p = 1.48 × 10(-8); the Cancer Genome Atlas RNA-Sequencing cohort: n = 419; p = 3.06 × 10(-7); Van Andel Research Institute microarray cohort: n=174; p=0.00743). For 48 patients receiving tyrosine kinase inhibitor (TKI) treatment, the prognostic classification was associated with radiologic response to treatment (p = 5.96 × 10(-4)) and prolonged survival on TKI treatment (p=0.019). The multigene assay can classify ccRCCs into clinical prognostic subtypes, which may be predictive of response in patients receiving TKI therapy.

Extramammary Paget’s disease of scrotum

We describe 4 cases of extramammary Pagets disease of the scrotum with underlying invasive carcinoma from 1997 to 1999. Three patients had metastatic inguinal lymphadenopathy. The delay in diagnosis was significant (mean 1 year). The diagnosis was made by skin biopsy in all patients. Histologically, intraepidermal cells with enlarged vesicular nuclei and vacuolated cytoplasm, which was mucin positive, were found. The mainstay of treatment is wide surgical excision, but positive margins remain a major problem. Other modes of treatment have been advocated but the efficacy for invasive disease is low. The key to successful control of the disease is therefore a high index of suspicion and early diagnosis.

Improved Detection Rate of Prostate Cancer Using the 10-Core Biopsy Strategy in Singapore

OBJECTIVES To evaluate if changing the biopsy regime to 10 cores might improve the positive predictive value (PPV) of elevated prostate-specific antigen [PSA, elevated range, 4 to 20 ng per ml, normal range, < 4 ng per ml] for the diagnosis of prostate carcinoma. METHODS From February 2000 to April 2001, 191 patients, mean age 64 years [range, 38 to 85 yr], underwent transrectal ultrasound [TRUS] for either elevated PSA [elevated range, 4 to 20 ng per ml] and/or abnormal digital rectal examination [DRE]. A 10-core TRUS-guided biopsy of the prostate was performed. This included the standard sextant biopsy and two additional cores for each far lateral zone. RESULTS Using this technique, 47 out of 191 patients [24.6%] had prostate cancer. The PPV for PSA levels of 4.1 to 10.0 ng per ml and 10.1 to 20.0 ng per ml were 19.3% and 35.4%, respectively. The lateral cores contributed 21.3% of the cancer cases, which would have been missed if only sextant biopsies were performed. CONCLUSIONS With the 10-core biopsy method, the PPV for prostate cancer for patients with a PSA in the range of 4 to 20 ng per ml was in the range of 25%. This is significantly different from previous reports. The reason for this may be due to the adoption of a better, more uniform and systematic biopsy strategy for patients with elevated PSA, or it may be a true reflection of the current population incidence. Hence, this biopsy strategy is highly recommended.

Clinical, biochemical and pathological features of initial and repeat transrectal ultrasonography prostate biopsy positive patients

Background: Using sextant biopsy, 16–41% of prostate cancers were diagnosed on repeat biopsy. The objective of the present study was to compare the differences in the clinical, biochemical and pathological features between patients with positive results on initial and repeat biopsies, with an aim to identify factors that can be used to improve the detection rate of transrectal ultrasound (TRUS) biopsy of the prostate.

Metformin Use in Relation With Survival Outcomes of Patients With Renal Cell Carcinoma

PURPOSE To examine the effect of metformin use on survival outcomes in patients with renal cell carcinoma (RCC). METHODS Retrospective analysis of 1528 RCC patients from 2 centers between 1992 and 2012 was conducted. A total of 390 diabetics with confirmed metformin use were included in the final analysis, with a median follow-up of 43.1 months. Primary outcomes were disease-free survival (DFS) and cancer-specific survival (CSS). Cox regression models were performed to evaluate the effects of potential predictors on DFS and CSS, following stratification of patients into local and metastatic disease. RESULTS We identified 290 diabetics with localized and 100 with metastatic RCC. There were no clinicopathologic differences in the profiles of metformin users and non-metformin users. For patients with localized RCC, metformin users had significantly better DFS (hazard ratio, 0.47; P < .01) and CSS (hazard ratio, 0.21; P < .01) than non-users. There was no difference in CSS between metformin users and non-metformin users in diabetics with metastatic RCC (hazard ratio, 0.78; P = .286). Limitations include retrospective design and lack of data on metformin dosage and duration of use. CONCLUSIONS Metformin use is correlated with improved survival in patients with localized RCC, but not in metastatic RCC. Future studies should focus on its potential mechanisms and clinical utility.

Outcome of Laparoscopic Live Donor Nephrectomy and Impact of Double Renal Arteries: Results From Two Transplant Centres

OBJECTIVE Live donor kidney transplantation is consistently superior to deceased donor kidney transplantation. Laparoscopic donor nephrectomy (LDN) is increasingly accepted as a safe and preferred surgical option. To evaluate the outcome of LDN and the impact of multiple arteries, a retrospective review was conducted on patients in two transplant centres. METHODS Fifty patients including eight with double vessels were studied. Standard left transperitoneal LDN was performed. Grafts including those with double vessels were prepared using the bench technique. Postoperative outcomes (up to 1 year) for donors and recipients were studied. The outcomes of recipients of a single or double vessel graft were compared. RESULTS All donors had an eventful recovery. No difference was found between the single and multiple vessels groups for operating time (168.21 ± 5.712 minutes vs. 197.50 ± 15.755 minutes) or hospital stay (3.21±0.165 days vs. 4.13±0.789 days). The recipient outcomes including hospital stay (10.17±0.596 days vs. 12.13 ± 1.797 days) and creatinine levels at day 7 (106.53 ± 5.583 μmol/L vs. 107.13 ± 11.857 μmol/L) and 1 year (120.21 ± 6.562 μmol/L vs. 124.75 ± 11.857 μmol/L) were similar. No ureteric stricture or graft loss was noted at 1-year follow-up. Recipient complications included lymphocoele (n = 2), haematoma (n = 3 with 2 requiring exploration), sepsis (n = 1), renal artery stenosis (n = 2 with 1 stented), repeated anastomosis (n = 1), and incisional hernia (n = 1). No differences were noted between the two groups. CONCLUSION Our results showed that overall donor morbidity rate was low, as reflected by the short hospital stay. Also, the overall parameters of the recipients were good. In particular, no ureteric stricture was noted, and graft survival was 100% at 1 year. The outcomes of the reconstructed group, despite the technical challenge, were similar to those of the single-vessel group.

The Successful and Novel Treatment of Non-Neurogenic Detrusor-External Sphincter Dyssynergia (DESD) with Botulinum Toxin A

Introduction: Our study aims to examine the treatment outcomes of patients with non-neurogenic detrusor-external sphincter dyssynergia (DESD) after the injection of botulinum toxin A (BTX-A, Botox®) to the external sphincter. Methods: A retrospective review of nine patients with DESD was performed. All patients were diagnosed with the aid of video urodynamic studies. Pre-operative evaluation was standardised using bladder diary, urine microscopy and culture, bedside ultrasound of the kidneys and bladder, and renal function test. Each received BTX-A injection of 50–100U to the external sphincter. The pre-operative and post-operative maximum flow rate (Qmax) and post-void residual urine (PVRU) were objectively compared using paired-samples t test. Results: All the injections were performed from December 2006 to March 2008. Of the nine patients, seven (77.8%) were female and two (22.2%) were male. The mean age was 49.2 years (range 20–64 years). The mean pre-operative maximum flow rate (Qmax) was 9.7±6.26 ml/s. A month later, the post-operative Qmax improved to 16.5±11.3 ml/s. Mean difference in Qmax was 6.76±8.1 ml/s (P = 0.037). The mean preoperative post void residual urine (PVRU) was 179.2±86.8 ml. This improved to 45.7±44.4 ml post-operatively. The mean difference in PVRU of 133.6±77.2 ml (P = 0.001). Conclusion: In patients with DESD, there is a significant improvement in PVRU and Qmax after the injection of BTX-A. Hence, BTX-A injection is an effective method of treatment for DESD. However, further studies and follow-up are required to further evaluate patient satisfaction, quality of life and need for repeated injections.

Tumor size and Fuhrman grade further enhance the prognostic impact of perinephric fat invasion and renal vein extension in T3a staging of renal cell carcinoma

To evaluate the prognostic values of perinephric fat invasion and renal vein invasion in pT3a renal cell carcinoma, as stand‐alone factors and in combination with tumor size and Fuhrman grade.