Outcomes According to ALK Status Determined by Central Immunohistochemistry or Fluorescence In Situ Hybridization in Patients With ALK-Positive NSCLC Enrolled in the Phase 3 ALEX Study.

INTRODUCTION: We retrospectively examined progression-free survival (PFS) and response by ALK fluorescence in situ hybridization (FISH) status in patients with advanced ALK immunohistochemistry (IHC)-positive NSCLC in the ALEX study. METHODS: A total of 303 treatment-naive patients were randomized to receive twice-daily alectinib 600 mg or crizotinib 250 mg. ALK status was assessed centrally using Ventana ALK (D5F3) CDx IHC and Vysis ALK Break Apart FISH Probe Kit. Primary end point is investigator-assessed PFS. Secondary end points of interest are objective response rate and duration. RESULTS: Investigator-assessed PFS was significantly prolonged with alectinib versus crizotinib in ALK IHC-positive and FISH-positive tumors (n = 203, 67%) (hazard ratio [HR] = 0.37, 95% confidence interval [CI]: 0.25-0.56; p < 0.0001) and ALK IHC-positive and FISH-uninformative tumors (n = 61, 20%) (HR = 0.39, 95% CI: 0.20-0.78) but not in ALK IHC-positive and FISH-negative tumors (n = 39, 13%) (HR = 1.33, 95% CI: 0.6-3.2). Objective response rates were higher with alectinib versus crizotinib in ALK IHC-positive and FISH-positive tumors (90.6% versus 81.4%; stratified OR = 2.22, 95% CI: 0.97-5.07) and ALK IHC-positive and FISH-uninformative tumors (96.0% versus 75.0%; OR = 9.29, 95% CI: 1.05-81.88) but not in ALK IHC-positive and FISH-negative tumors (28.6% versus 44.4%; OR = 0.45, 95% CI: 0.12-1.74). Next-generation sequencing was performed in 35 of 39 patients with ALK IHC-positive and FISH-negative tumors; no ALK fusion was identified in 20 of 35 patients (57.1%) by next-generation sequencing, but 10 of 20 (50.0%) had partial response or stable disease. CONCLUSIONS: Outcomes of patients with ALK IHC-positive and FISH-positive and ALK IHC-positive and FISH-uninformative NSCLC were similar to those of the overall ALEX population. These results suggest that Ventana ALK IHC is a standard testing method for selecting patients for treatment with alectinib.

Outcomes According to ALK Status Determined by Central IHC or FISH in Patients with ALK-Positive NSCLC Enrolled in the Phase III ALEX Study.

INTRODUCTION: We retrospectively examined progression-free survival (PFS) and response by ALK fluorescence in-situ hybridization (FISH) status in patients with advanced ALK immunohistochemistry (IHC)-positive non-small-cell lung cancer (NSCLC) in the ALEX study. METHODS: 303 treatment-naïve patients were randomized to receive twice-daily alectinib 600 mg or crizotinib 250 mg. ALK status was assessed centrally using Ventana ALK (D5F3) CDx IHC and Vysis ALK Break Apart FISH Probe Kit. Primary endpoint: investigator-assessed PFS. Secondary endpoints of interest: objective response rate (ORR) and duration. RESULTS: Investigator-assessed PFS was significantly prolonged with alectinib versus crizotinib in ALK IHC-positive/FISH-positive tumors (n = 203, 67%) (HR 0.37, 95% CI: 0.25-0.56) and ALK IHC-positive/FISH-uninformative tumors (n = 61, 20%) (HR 0.39, 95% CI: 0.20-0.78), but not ALK IHC-positive/FISH-negative tumors (n = 39, 13%) (HR 1.33, 95% CI: 0.6-3.2). ORRs were higher with alectinib versus crizotinib in ALK IHC-positive/FISH-positive tumors 90.6% versus 81.4%; stratified odds ratio [OR] 2.22, 95% CI: 0.97-5.07) and ALK IHC-positive/FISH-uninformative tumors (96.0% versus 75.0%; OR 9.29, 95% CI: 1.05-81.88), but not ALK IHC-positive/FISH-negative tumors (28.6% versus 44.4%; OR 0.45, 95% CI: 0.12-1.74). Next-generation sequencing (NGS) was performed in 35/39 patients with ALK IHC-positive/FISH-negative tumors; no ALK fusion was identified in 20/35 (57.1%) patients by NGS, but 10/20 (50.0%) had partial response/stable disease. CONCLUSION: Outcomes of patients with ALK IHC-positive/FISH-positive and ALK IHC-positive/FISH-uninformative NSCLC were similar to the overall ALEX population. These results suggest that Ventana ALK IHC is a standard testing method for selecting patients for treatment with alectinib.

The impact of pre-analytical processing on staining quality for H&E, dual hapten, dual color in situ hybridization and fluorescent in situ hybridization assays.

With the advent of personalized medicine, anatomic pathology-based molecular assays, including in situ hybridization (ISH) and mRNA detection tests, are performed routinely in many laboratories and have increased in their clinical importance and complexity. These assays require appropriately fixed tissue samples that preserve both nucleic acid targets and histomorphology to ensure reliable test results for determining patient treatment options. However, all aspects of tissue processing, including time until tissue fixation, type of fixative, duration of fixation, post-fixation treatments, and sectioning of the sample, impact the staining results. ASCO/CAP has issued pre-analytical guidelines to standardize tissue processing for HER2 testing in breast carcinoma specimens: 10% neutral-buffered formalin (NBF) with a fixation time from at least 6 to 48h [1]. Often, this recommendation is not followed to the detriment of staining results [2]. In this paper, we used a human breast carcinoma cell line (MCF7) generated as xenograft tumors as a model system to analyze the effects of different pre-analytical conditions on ISH staining. We performed H&E, FISH and dual colorimetric HER2 ISH assays using specimens fixed across a range of times in six different commonly used fixatives. Additionally, we investigated the effects of varying tissue section thickness, which also impacted the quality of ISH staining. Finally, we evaluated the effects of three different decalcifying solutions on human breast specimens, typically a treatment that occurs post-fixation for evaluating metastases to bone. The results indicate that time and type of fixation treatment, as well as appropriate tissue thickness and post-fixation treatment, all contribute to the quality of ISH staining results. Our data support the ASCO/CAP recommendations for standardized tissue processing (at least 6h in formalin-based fixatives and 4µm section thickness) and indicate that certain fixatives and post-fixative treatments are detrimental to molecular staining results.

Tryptophan Cu(I)-pi interaction fine-tunes the metal binding properties of the bacterial metallochaperone CusF.

The periplasmic metallochaperone CusF coordinates Cu(I) and Ag(I) through a unique site consisting of a Met(2)His motif as well as a Cu(I)-pi interaction between a nearby tryptophan, W44, and the metal ion. Through mutational analyses we investigate here the role that W44 in CusF plays in metal coordination. Nuclear magnetic resonance spectra show that the specificity of CusF for Cu(I) and Ag(I) is not altered by mutation of W44. X-ray absorption spectroscopy studies reveal that W44 protects the bound Cu(I) from oxidation as well as from adventitious ligands. Competition assays demonstrate that W44 does not significantly contribute to the affinity of CusF for metal, but that substitution of W44 by methionine, which forms a fourth Cu(I) ligand, substantially increases the affinity. These studies indicate that W44 is important in maintaining a moderate-affinity and solvent-shielded three-coordinate environment for Cu(I), which has implications for the function of CusF as a metallochaperone.

Unusual Cu(I)/Ag(I) coordination of Escherichia coli CusF as revealed by atomic resolution crystallography and X-ray absorption spectroscopy.

Elevated levels of copper or silver ions in the environment are an immediate threat to many organisms. Escherichia coli is able to resist the toxic effects of these ions through strictly limiting intracellular levels of Cu(I) and Ag(I). The CusCFBA system is one system in E. coli responsible for copper/silver tolerance. A key component of this system is the periplasmic copper/silver-binding protein, CusF. Here the X-ray structure and XAS data on the CusF-Ag(I) and CusF-Cu(I) complexes, respectively, are reported. In the CusF-Ag(I) structure, Ag(I) is coordinated by two methionines and a histidine, with a nearby tryptophan capping the metal site. EXAFS measurements on the CusF-Cu(I) complex show a similar environment for Cu(I). The arrangement of ligands effectively sequesters the metal from its periplasmic environment and thus may play a role in protecting the cell from the toxic ion.

Periplasmic metal-resistance protein CusF exhibits high affinity and specificity for both CuI and AgI.

The periplasmic protein CusF, as a part of the CusCFBA efflux complex, plays a role in resistance to elevated levels of copper and silver in Escherichia coli. Although homologues have been identified in other Gram-negative bacteria, the substrate of CusF and its precise role in metal resistance have not been described. Here, isothermal titration calorimetry (ITC) was used to demonstrate that CusF binds with high affinity to both Cu(I) and Ag(I) but not Cu(II). The affinity of CusF for Ag(I) was higher than that for Cu(I), which could reflect more efficient detoxification of Ag(I) given the lack of a cellular need for Ag(I). The chemical shifts in the nuclear magnetic resonance (NMR) spectra of CusF-Ag(I) as compared to apo-CusF show that the region of CusF most affected by Ag(I) binding encompasses three absolutely conserved residues: H36, M47, and M49. This suggests that these residues may play a role in Ag(I) coordination. The NMR spectra of CusF in the presence of Cu(II) do not indicate specific binding, which is in agreement with the ITC data. We conclude that Cu(I) and Ag(I) are the likely physiological substrates.

A novel copper-binding fold for the periplasmic copper resistance protein CusF.

We have determined the crystal structure of apo-CusF, a periplasmic protein involved in copper and silver resistance in Escherichia coli. The protein forms a five-stranded beta-barrel, classified as an OB-fold, which is a unique topology for a copper-binding protein. NMR chemical shift mapping experiments suggest that Cu(I) is bound by conserved residues H36, M47, and M49 located in beta-strands 2 and 3. These residues are clustered at one end of the beta-barrel, and their side chains are oriented toward the interior of the barrel. Cu(I) can be modeled into the apo-CusF structure with only minimal structural changes using H36, M47, and M49 as ligands. The unique structure and metal binding site of CusF are distinct from those of previously characterized copper-binding proteins.