Tissue microarrays: one size does not fit all

<p>Abstract</p> <p>Background</p> <p>Although tissue microarrays (TMAs) are commonly employed in clinical and basic-science research, there are no guidelines for evaluating the appropriateness of a TMA for a given biomarker and tumor type. Furthermore, TMA performance across multiple biomarkers has not been systematically explored.</p> <p>Methods</p> <p>A simulated TMA with between 1 and 10 cores was designed to study tumor expression of 6 biomarkers with varied expression patterns (B7-H1, B7-H3, survivin, Ki-67, CAIX, and IMP3) using 100 patients with clear cell renal cell carcinoma (RCC). We evaluated agreement between whole tissue section and TMA immunohistochemical biomarker quantification to assess how many TMA cores are necessary to adequately represent RCC whole tissue section expression. Additionally, we evaluated associations of whole tissue section and TMA expression with RCC-specific death.</p> <p>Results</p> <p>The number of simulated TMA cores necessary to adequately represent whole tissue section quantification is biomarker specific. Although 2-3 cores appeared adequate for B7-H3, Ki-67, CAIX, and IMP3, even as many as 10 cores resulted in poor agreement for B7-H1 and survivin compared to RCC whole tissue sections. While whole tissue section B7-H1 was significantly associated with RCC-specific death, no significant associations were detected using as many as 10 TMA cores, suggesting that TMAs can result in false-negative findings if the TMA is not optimally designed.</p> <p>Conclusions</p> <p>Prior to TMA analysis, the number of TMA cores necessary to accurately represent biomarker expression on whole tissue sections should be established as there is not a one-size-fits-all TMA. We illustrate the use of a simulated TMA as a cost-effective tool for this purpose.</p

Structure, function, and evolution of metallo-β-lactamases from the B3 subgroup-emerging targets to combat antibiotic resistance

β-Lactams are the most widely employed antibiotics in clinical settings due to their broad efficacy and low toxicity. However, since their first use in the 1940s, resistance to β-lactams has proliferated to the point where multi-drug resistant organisms are now one of the greatest threats to global human health. Many bacteria use β-lactamases to inactivate this class of antibiotics via hydrolysis. Although nucleophilic serine-β-lactamases have long been clinically important, most broad-spectrum β-lactamases employ one or two metal ions (likely Zn2+) in catalysis. To date, potent and clinically useful inhibitors of these metallo-β-lactamases (MBLs) have not been available, exacerbating their negative impact on healthcare. MBLs are categorised into three subgroups: B1, B2, and B3 MBLs, depending on their sequence similarities, active site structures, interactions with metal ions, and substrate preferences. The majority of MBLs associated with the spread of antibiotic resistance belong to the B1 subgroup. Most characterized B3 MBLs have been discovered in environmental bacteria, but they are increasingly identified in clinical samples. B3-type MBLs display greater diversity in their active sites than other MBLs. Furthermore, at least one of the known B3-type MBLs is inhibited by the serine-β-lactamase inhibitor clavulanic acid, an observation that may promote the design of derivatives active against a broader range of MBLs. In this Mini Review, recent advances in structure-function relationships of B3-type MBLs will be discussed, with a view to inspiring inhibitor development to combat the growing spread of β-lactam resistance

Structure, function, and evolution of metallo-β-lactamases from the B3 subgroup—emerging targets to combat antibiotic resistance

β-Lactams are the most widely employed antibiotics in clinical settings due to their broad efficacy and low toxicity. However, since their first use in the 1940s, resistance to β-lactams has proliferated to the point where multi-drug resistant organisms are now one of the greatest threats to global human health. Many bacteria use β-lactamases to inactivate this class of antibiotics via hydrolysis. Although nucleophilic serine-β-lactamases have long been clinically important, most broad-spectrum β-lactamases employ one or two metal ions (likely Zn2+) in catalysis. To date, potent and clinically useful inhibitors of these metallo-β-lactamases (MBLs) have not been available, exacerbating their negative impact on healthcare. MBLs are categorised into three subgroups: B1, B2, and B3 MBLs, depending on their sequence similarities, active site structures, interactions with metal ions, and substrate preferences. The majority of MBLs associated with the spread of antibiotic resistance belong to the B1 subgroup. Most characterized B3 MBLs have been discovered in environmental bacteria, but they are increasingly identified in clinical samples. B3-type MBLs display greater diversity in their active sites than other MBLs. Furthermore, at least one of the known B3-type MBLs is inhibited by the serine-β-lactamase inhibitor clavulanic acid, an observation that may promote the design of derivatives active against a broader range of MBLs. In this Mini Review, recent advances in structure-function relationships of B3-type MBLs will be discussed, with a view to inspiring inhibitor development to combat the growing spread of β-lactam resistance