STAG2 Protein Expression in Non-muscle-invasive Bladder Cancer: Associations with Sex, Genomic and Transcriptomic Changes, and Clinical Outcomes.

Background: Mutations in STAG2 cause complete loss of STAG2 protein in approximately one-third of non-muscle-invasive bladder cancers (NMIBCs). STAG2 protein expression is easily determined via immunohistochemistry (IHC) and published data suggest that loss of STAG2 expression is a good prognostic indicator in NMIBC. Objective: To confirm the relationship between STAG2 protein expression and clinical outcomes and tumour characteristics in NMIBC. Design setting and participants: IHC was used to determine STAG2 expression in 748 incident urothelial bladder cancers (UBCs) and recurrence-free, progression-free, and disease-specific survival were compared for patients with and without STAG2 loss. Exome and RNA sequencing were used to explore links between STAG2 loss and tumour molecular characteristics. Results and limitations: STAG2 loss was observed in 19% of UBC patients and was 1.6-fold more common among female patients. Loss was frequent among grade 1 pTa tumours (40%), decreasing with stage and grade to only 5% among grade 3 pT2+ tumours. Loss was associated with fewer copy-number changes and less aggressive expression subtypes. In UBC, STAG2 loss was a highly significant prognostic indicator of better disease-free survival but was not independent of stage and grade. STAG2 loss was not a statistically significant predictor of NMIBC recurrence. STAG2 loss was significantly associated with better progression-free survival in NMIBC and appeared to be more prognostic for males than for females. Conclusions: A simple IHC-based STAG2 test shows promise for identifying NMIBC patients at lower risk of progression to MIBC for whom more conservative treatments may be suitable. Patient summary: A protein called STAG2 is frequently lost in early bladder cancers, most often in less aggressive tumours. STAG2 loss is easily measured and could be used as a biomarker to help guide treatment decisions.

Trends in urine biomarker discovery for urothelial bladder cancer: DNA, RNA, or protein?

Urothelial bladder cancer is a complex disease displaying a landscape of heterogenous molecular subtypes, mutation profiles and clinical presentations. Diagnosis and surveillance rely on flexible cystoscopy which has high accuracy, albeit accompanied by a high-cost burden for healthcare providers and discomfort for patients. Advances in "omic" technologies and computational biology have provided insights into the molecular pathogenesis of bladder cancer and provided powerful tools to identify markers for disease detection, risk stratification, and predicting responses to therapy. To date, numerous attempts have been made to discover and validate diagnostic biomarkers that could be deployed as an adjunct to the cystoscopic diagnosis and long-term surveillance of bladder cancer. We report a comprehensive literature analysis using PubMed to assess the changing trends in investigating DNA, RNA, or proteins as diagnostic urinary biomarkers over a period of 5 decades: 1970-2020. A gradual shift has been observed in research away from protein biomarkers to nucleic acids including different classes of RNA, and DNA methylation and mutation markers. Until 2000, publications involving protein biomarker discovery constituted 87% of the total number of research articles with DNA comprising 6% and RNA 7%. Since 2000 the proportion of protein biomarker articles has fallen to 40%, and DNA and RNA studies increased to 32% and 28%, respectively. Clearly research focus, perhaps driven by technological innovation, has shifted from proteins to nucleic acids. We optimistically hypothesise that, following thorough validation, a clinically useful detection test for bladder cancer based on a panel of DNA or RNA markers could become reality within 5-10 years.

Tropomyosins: Potential Biomarkers for Urothelial Bladder Cancer.

Despite the incidence and prevalence of urothelial bladder cancer (UBC), few advances in treatment and diagnosis have been made in recent years. In this review, we discuss potential biomarker candidates: the tropomyosin family of genes, encoded by four loci in the human genome. The expression of these genes is tissue-specific. Tropomyosins are responsible for diverse cellular roles, most notably based upon their interplay with actin to maintain cellular processes, integrity and structure. Tropomyosins exhibit a large variety of splice forms, and altered isoform expression levels have been associated with cancer, including UBC. Notably, tropomyosin isoforms are detectable in urine, offering the potential for non-invasive diagnosis and risk-stratification. This review collates the basic knowledge on tropomyosin and its isoforms, and discusses their relationships with cancer-related phenomena, most specifically in UBC.

MRE11A Isoform Expression Associated with Outcome Following Radiotherapy in Muscle-Invasive Bladder Cancer does not Alter Cell Survival and DNA Double-Strand Break Repair Following Ionising Radiation.

BACKGROUND: DNA double strand breaks are the cytotoxic lesions produced by ionising radiation. Critical for the repair of these lesions is the DNA damage response protein MRE11 which, in a complex with RAD50 and NBS1, mediates DNA damage signalling and double-strand break repair. We previously found the presence of an MRE11 germline single nucleotide polymorphism (SNP), rs1805363 (G > A), to be associated with poor outcome following radiotherapy (RT) and increased expression of MRE11 isoform 2 in a limited panel of bladder cancer cell lines and tumours. OBJECTIVES: To look for further evidence in support of the SNP/isoform association in a larger panel of germline and tumour samples donated by patients diagnosed with invasive bladder cancer, and to test the hypothesis that bladder cancer cells expressing MRE11 isoform 2 would be more radio resistant than cells expressing MRE11 isoform 1. METHODS: Germline DNA from 189 patients with invasive bladder cancer (141 T2, 48 T1) was genotyped for the rs1805363 G > A SNP. Loss of heterozygosity was determined by genotyping tumour DNA in 17GA germline patients. The Cancer Genome Atlas was mined to correlate presence of the GA germline genotype with MRE11 isoform expression. We used colony formation assays and γH2AX foci kinetics after ionising radiation in RT112 MRE11 knockdown cells expressing ectopic MRE11 isoform 1 or 2. RESULTS: Of the 189 germline DNA samples, 22 contained both the A minor allele and G major allele with the remaining wild type containing only the G major allele. LOH was identified in seven of 17 available tumour samples. Tumour MRE11 isoform 2 expression was found to be significantly higher (p = 0.007) in patients's samples containing the A minor allele compared to those with only the G major allele (n = 23). In the TCGA database we found 16% (66 out of 406) of bladder tumours heterozygous for the SNP and only two homozygous, and a significant relative increase of isoform 2 usage (p = 0.017). We identified no significant difference in radio sensitivity between bladder cancer cells expressing either MRE11 isoform. CONCLUSIONS: In this study the MRE11 isoform 2 was not found to be associated with increased cellular sensitivity to radiation. We conclude that the previously reported association between the germline rs1805363 SNP and poor survival in MIBC patients following RT is unlikely to be related to the DNA damage response function of MRE11 isoform 2.