Enzyme studies in human transitional cell carcinoma of the urinary bladder

Prognostic Role of Serum Lactate Dehydrogenase in Patients With Urothelial Carcinoma: A Systematic Review and Meta-Analysis

Background: To investigate the potential prognostic role of serum lactate dehydrogenase (LDH) in patients with urothelial carcinoma (UC) using the method of systematic review and meta-analysis.

Materials and Methods: We searched PubMed, Embase, Cochrane Library, and Web of Science for eligible studies up to February 2020. Pooled hazard ratios (HRs) and 95% confidence intervals (CIs) were used to estimate the relationship.

Results: A total of 14 studies including 4,009 patients with UC were incorporated. The results showed that a high pretreatment serum LDH was associated with an inferior overall survival (OS, HR 1.61, 95% CI 1.39–1.87, p < 0.001), cancer-specific survival (CSS, HR 1.41, 95% CI 1.05–1.90, p = 0.022), and disease-free survival (DFS, HR 1.64, 95% CI 1.04–2.59, p = 0.034) in UC. Subgroup analyses identified that a high pretreatment serum LDH was associated with a poor OS (HR 1.97, 95% CI 1.02–3.81, p = 0.042) and DFS (HR 1.64, 95% CI 1.04–2.59, p = 0.034) in upper tract urothelial carcinoma, a short OS (HR 1.71, 95% CI 1.37–2.15, p < 0.001) in urothelial carcinoma of bladder.

Conclusion: Our findings indicated that a high level of pretreatment serum LDH was associated with inferior OS, CSS, and DFS in patients with UC. This biomarker can be an important factor incorporated into the prognostic models for UC.

Metabolic phenotype of bladder cancer

Metabolism of bladder cancer represents a key issue for cancer research. Several metabolic altered pathways are involved in bladder tumorigenesis, representing therefore interesting targets for therapy. Tumor cells, including urothelial cancer cells, rely on a peculiar shift to aerobic glycolysis-dependent metabolism (the Warburg-effect) as the main energy source to sustain their uncontrolled growth and proliferation. Therefore, the high glycolytic flux depends on the overexpression of glycolysis-related genes (SRC-3, glucose transporter type 1 [GLUT1], GLUT3, lactic dehydrogenase A [LDHA], LDHB, hexokinase 1 [HK1], HK2, pyruvate kinase type M [PKM], and hypoxia-inducible factor 1-alpha [HIF-1α]), resulting in an overproduction of pyruvate, alanine and lactate. Concurrently, bladder cancer metabolism displays an increased expression of genes favoring the pentose phosphate pathway (glucose-6-phosphate dehydrogenase [G6PD]) and the fatty-acid synthesis (fatty acid synthase [FASN]), along with a decrease of AMP-activated protein kinase (AMPK) and Krebs cycle activities. Moreover, the PTEN/PI3K/AKT/mTOR pathway, hyper-activated in bladder cancer, acts as central regulator of aerobic glycolysis, hence contributing to cancer metabolic switch and tumor cell proliferation. Besides glycolysis, glycogen metabolism pathway plays a robust role in bladder cancer development. In particular, the overexpression of GLUT-1, the loss of the tumor suppressor glycogen debranching enzyme amylo-α-1,6-glucosidase, 4-α-glucanotransferase (AGL), and the increased activity of the tumor promoter enzyme glycogen phosphorylase impair glycogen metabolism. An increase in glucose uptake, decrease in normal cellular glycogen storage, and overproduction of lactate are consequences of decreased oxidative phosphorylation and inability to reuse glucose into the pentose phosphate and de novo fatty acid synthesis pathways. Moreover, AGL loss determines augmented levels of the serine-to-glycine enzyme serine hydroxymethyltransferase-2 (SHMT2), resulting in an increased glycine and purine ring of nucleotides synthesis, thus supporting cells proliferation. A deep understanding of the metabolic phenotype of bladder cancer will provide novel opportunities for targeted therapeutic strategies.

Tumor enzymes and prognosis in transitional cell carcinoma of the bladder: prediction of risk of progression in patients with superficial disease

The activities of 6 enzymes of carbohydrate metabolism were estimated in superficial transitional cell carcinomas from 103 patients undergoing transurethral resection of the bladder for the first time. The patients were followed by quarterly endoscopic examinations for a maximum of 81 months (median 33 months). During followup 24 patients had progressive disease. The activities of phosphofructokinase and phosphohexose isomerase were significantly lower in tumors from patients whose disease had superficially invaded the lamina propria (stage pT1) than in others in whom it was confined to the bladder mucosa (stage pTa). Similarly the activities of the 2 enzymes were significantly higher in well differentiated (grade 1) than in moderately well differentiated (grade 2) carcinomas. Univariate analyses using the log rank test showed that neither pathological stage nor malignancy grade of the carcinoma was a significant factor in predicting the risk of progression. Of the 6 enzymes, below median activities of phosphofructokinase, lactate dehydrogenase and phosphohexose isomerase were associated with a significantly increased risk of progression in these patients. Multivariate analyses using Cox's proportional hazards model showed that the activity of lactic dehydrogenase in superficial transitional cell carcinoma is an independent prognostic factor in predicting the risk of progression. It is postulated that the measurements of the activities of the 3 enzymes in tumors from patients with superficial transitional cell carcinoma might help to select individual patients with a high risk of progression for adjuvant intravesical treatments.