The significance of lactate transporters has been recognized in various cancer types, but their role in urothelial carcinoma remains mostly unknown. The aim of this study was to investigate the functional importance of the monocarboxylate transporter (MCT) 4 in preclinical models of urothelial carcinoma and to assess its relevance in patient tumors. The association of MCT4 expression with molecular subtypes and outcome was determined in The Cancer Genome Atlas (TCGA) cohort and two independent cohorts of patients with urothelial carcinoma. Silencing of MCT4 was performed using siRNAs in urothelial carcinoma cell lines. Effects of MCT4 inhibition on cell growth, apoptosis, and production of reactive oxygen species (ROS) were assessed. Moreover, effects on lactate efflux were determined. The in vivo effects of MCT4 silencing were assessed in an orthotopic xenograft model. MCT4 expression was higher in the basal subtype. Decreased MCT4 methylation and increased RNA and protein expression were associated with worse overall survival (OS). Inhibition of MCT4 led to a reduction in cell growth, induction of apoptosis, and an increased synthesis of ROS. MCT4 inhibition resulted in intracellular accumulation of lactate. In vivo, stable knockdown of MCT4 reduced tumor growth. The expression of MCT4 in urothelial carcinoma is associated with features of aggressive tumor biology and portends a poor prognosis. Inhibition of MCT4 results in decreased tumor growth in vitro and in vivo. Targeting lactate metabolism via MCT4 therefore provides a promising therapeutic approach for invasive urothelial carcinoma, especially in the basal subtype.

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<div>Abstract<p>The significance of lactate transporters has been recognized in various cancer types, but their role in urothelial carcinoma remains mostly unknown. The aim of this study was to investigate the functional importance of the monocarboxylate transporter (MCT) 4 in preclinical models of urothelial carcinoma and to assess its relevance in patient tumors. The association of MCT4 expression with molecular subtypes and outcome was determined in The Cancer Genome Atlas (TCGA) cohort and two independent cohorts of patients with urothelial carcinoma. Silencing of MCT4 was performed using siRNAs in urothelial carcinoma cell lines. Effects of MCT4 inhibition on cell growth, apoptosis, and production of reactive oxygen species (ROS) were assessed. Moreover, effects on lactate efflux were determined. The <i>in vivo</i> effects of MCT4 silencing were assessed in an orthotopic xenograft model. MCT4 expression was higher in the basal subtype. Decreased MCT4 methylation and increased RNA and protein expression were associated with worse overall survival (OS). Inhibition of MCT4 led to a reduction in cell growth, induction of apoptosis, and an increased synthesis of ROS. MCT4 inhibition resulted in intracellular accumulation of lactate. <i>In vivo</i>, stable knockdown of MCT4 reduced tumor growth. The expression of MCT4 in urothelial carcinoma is associated with features of aggressive tumor biology and portends a poor prognosis. Inhibition of MCT4 results in decreased tumor growth <i>in vitro</i> and <i>in vivo</i>. Targeting lactate metabolism via MCT4 therefore provides a promising therapeutic approach for invasive urothelial carcinoma, especially in the basal subtype.</p></div>

<p>Suppl. Table 1: Characteristics of the TCGA cohort; Suppl. Table 2: Characteristics of cohort A. CIS= carcinoma in situ; Suppl. Table 3: Characteristics of cohort B Suppl. Fig. 1. Correlation of degree of DNA methylation at CpG site cg10183885 in the SLC16A3 gene region (see Suppl. Table 4) and MCT4 mRNA expression; Suppl. Fig. 2. Correlation of gene expression and protein expression in cohort B. Suppl. Fig. 3. Representative H&E (upper panel) and immunohistochemical images in matched bladder cancer samples (each column is one patient). CD8 was used to stain T cells (middle panel) in comparison with MCT4 expression (lower panel). Suppl. Fig. 4. Protein expression of MCT4 in benign urothelium, primary tumor tissue and lymph node metastases (cohort A). Suppl. Fig. 5. Protein expression in primary tumors according to tumor stage (left) and lymph node involvement (right) (cohort A).; Suppl. Fig. 6. MCT4 mRNA expression correlates with molecular subtypes in the TCGA cohort using the updated TCGA nomenclature (n=408); Suppl. Fig. 7. MCT4 gene expression does not correlate with overall survival in a cohort of patients undergoing neoadjuvant chemotherapy; Suppl. Fig. 8. Expression of MCT4 in urothelial carcinoma cell lines detected by Western Blot (A) and qPCR (B); Suppl. Fig. 9. Effect of MCT4 silencing on cell growth in hypoxic conditions determined by MTT assay. Suppl. Fig. 10. Effect of inhibition of MCT4 using siRNA on cell growth of the MCT4 negative cell line RT4 determined by MTT assay; Suppl. Fig 11. Effect of MCT4 silencing on cell growth in glucose free conditions determined by MTT assay; Suppl.Fig. 12. Effect of different concentrations of MCT4 specific antisense olignucleotide (ASO) on cell growth determined by MTT assay. Suppl. Fig. 13. Oxygen consumption rates at baseline (A), following glucose injection (B) and following oligomycin injection (C) in cell lines treated with control siRNA or MCT4 specific siRNAs.</p>

Background: Transitions of care represent a vulnerable time for patients where unintended therapeutic changes are common and inadequate communication of information frequently results in medication errors. Pharmacists have a large impact on the success of patients during these care transitions; however, their role and experiences are largely absent from the literature. Objectives: The purpose of this study was to gain a greater understanding of British Columbian hospital pharmacists’ perceptions of the hospital discharge process and their role in it. Methods:  A qualitative study utilizing focus groups and key informant interviews of British Columbian hospital pharmacists was conducted from April to May 2021. Questions asked during interviews were developed following a detailed literature search and included questions regarding the use of frequently studied interventions. Interview sessions were transcribed and then thematically analyzed using both NVivo software and manual coding. Results:  Three focus groups with a total of 20 participants and one key informant interview were conducted. Six themes were identified through data analysis: (1) overall perspectives; (2) important roles of pharmacists in discharges; (3) patient education; (4) barriers to optimal discharges; (5) solutions to current barriers; and (6) prioritization. Conclusions and Relevance: Pharmacists play a vital role in patient discharges but due to limited resources and inadequate staffing models they are often unable to be optimally involved. Understanding the thoughts and perceptions of pharmacists on the discharge process can help us better allocate limited resources to ensure patients receive optimal care.