Reverse transcriptase-polymerase chain reaction detection of AR-V7 transcripts in whole blood was associated with inferior outcomes in patients treated with abiraterone. These results reinforce the potential usefulness of AR-V7 as a prognostic and predictive biomarker for metastatic castration resistant prostate cancer.

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.

223 Background: Expression of androgen receptor splice variant 7 (AR-V7) in circulating tumor cells (CTCs) has been associated with resistance to ABI and enzalutamide (ENZ) (Antonarakis et al. N Engl J Med 2014). We have developed a RT-PCR assay that is neither time sensitive nor requires CTC enrichment for detection of prostate cancer (PCa)-associated transcripts in whole blood. Using this assay, our aim was to correlate AR-V7 expression with outcomes on ABI. Methods: 2.5 ml whole blood was collected into PAXgene RNA tubes from mCRPC patients (pts) commencing ABI. RT-PCR was performed for the following genes: AR-V7, FOXA1, GRHL2, HOXB13, KLK2, KLK3 and TMPRSS2:ERG. For each gene, the highest CT value among 20 normal controls was set as the threshold for a positive (+) test. Clinical endpoints were PSA50 response rate (RR) (PSA decline ≥ 50% confirmed ≥ 3 weeks later), PSA30 RR, time to PSA (PCWG2 criteria) or clinical progression (change in anti-cancer therapy or decline in ECOG performance status (PS) ≥ 2 levels due to PCa), and overall survival (OS). Results: Whole blood samples were obtained from 37 pts. Median age was 70. 59% received prior docetaxel. All pts were ABI and ENZ naïve. PSA50 RR was 37% and PSA30 RR was 48%. Median progression-free survival (PFS) was 3.8 months (mos) and median OS was 21.0 mos. 11% (4/37) of pts were AR-V7+. AR-V7+ pts were more likely to have high ALP (P= 0.04; Χ2), high LDH (P= 0.07) and ECOG PS ≥ 2 (P= 0.052). Pts with an AR-V7+ test had lower PSA50 RR (0% vs. 42%, P= 0.10; Χ2) and PSA30 RR (0% vs. 52%, P= 0.051) together with shorter median PFS (0.7 mos vs. 4.0 mos, P< 0.001; log-rank) and median OS (5.5 mos vs. 22.1 mos, P< 0.001). Other factors linked with worse OS were high ALP (P= 0.02), liver metastases (P= 0.03), ≤ 36 mos on primary hormone therapy (P= 0.04), HOXB13+ (P= 0.03) and KLK2+ (P< 0.001). Conclusions: RT-PCR detection of AR-V7 transcripts in whole blood was associated with a 0% PSA RR and significantly inferior PFS and OS in pts treated with ABI. These results reinforce the potential utility of AR-V7 as a prognostic and predictive biomarker for mCRPC. Validation of the assay in larger datasets is ongoing.

Extrinsic signals that regulate oligodendrocyte maturation and subsequent myelination are essential for central nervous system development and regeneration. Deficiency in the extracellular factor laminin-2 (Lm2, comprising the α2β1γ1 chains), as occurs in congenital muscular dystrophy, can lead to impaired oligodendroglial development and aberrant myelination, but many aspects of Lm2-regulated oligodendroglial signaling and differentiation remain undefined. We show that receptor-like protein tyrosine phosphatase α (PTPα, also known as PTPRA) is essential for myelin basic protein expression and cell spreading during Lm2-induced oligodendrocyte differentiation. PTPα complexes with the Lm2 receptors α6β1 integrin and dystroglycan to transduce Fyn activation upon Lm2 engagement. In this way, PTPα mediates a subset of Lm2-induced signals required for differentiation, includeing mTOR-dependent Akt activation but not Erk1/2 activation. We identify N-myc downstream regulated gene-1 (NDRG1) as a PTPα-regulated molecule during oligodendrocyte differentiation, and distinguish Lm2 receptor-specific modes of Fyn-Akt-dependent and -independent NDRG1 phosphorylation. Altogether, this reveals an Lm2-regulated PTPα-Fyn-Akt signaling axis that is critical for key aspects of the gene expression and morphological changes that mark oligodendrocyte maturation.

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Introduction. Overdose with the calcium channel blocker amlodipine can cause profound hypotension that may be exacerbated by the concurrent ingestion of an angiotensin II receptor antagonist. Best management of such overdoses is uncertain although the use of hyperinsulinaemia-euglycaemia (HIE) has been recommended. Case report. We report a case of mixed amlodipine and losartan overdose in a 50-year-old lady. Severe hypotension was resistant to conventional vasopressors and high-dose insulin/euglycaemia, but did respond to a metaraminol infusion. Conclusion. A trial of metaraminol early in severe cases of calcium channel blocker and angiotensin II receptor antagonist toxicity may be of benefit, especially when conventional ionotropic treatment measures are failing.

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