Receptor Tyrosine Kinase Fusions and BRAF Kinase Fusions are Rare but Actionable Resistance Mechanisms to EGFR Tyrosine Kinase Inhibitors

Introduction

We analyzed a large set of EGFR-mutated (EGFR+) NSCLC to identify and characterize cases with co-occurring kinase fusions as potential resistance mechanisms to EGFR tyrosine kinase inhibitors (TKIs).

Coronavirus Disease Contact Tracing Outcomes and Cost,Salt Lake County,Utah, USA,March–May 2020

Outcomes and costs of coronavirus disease (COVID-19) contact tracing are limited. During March–May 2020, we constructed transmission chains from 184 index cases and 1,499 contacts in Salt Lake County, Utah, USA, to assess outcomes and estimate staff time and salaries. We estimated 1,102 staff hours and $29,234 spent investigating index cases and contacts. Among contacts, 374 (25%) had COVID-19; secondary case detection rate was ≈31% among first-generation contacts, ≈16% among second- and third-generation contacts, and ≈12% among fourth-, fifth-, and sixth-generation contacts. At initial interview, 51% (187/370) of contacts were COVID-19–positive; 35% (98/277) became positive during 14-day quarantine. Median time from symptom onset to investigation was 7 days for index cases and 4 days for first-generation contacts. Contact tracing reduced the number of cases between contact generations and time between symptom onset and investigation but required substantial resources. Our findings can help jurisdictions allocate resources for contact tracing.     

Quantitative Graft Integration of Fetal Hippocampal Transplants Labeled with 5′ Bromodeoxyuridine into Normal Adult Hippocampus

Quantitative studies of neural graft development require: (1) a cell label which is both preferential for neurons and can be measured in terms of specific labeling; (2) a serial reconstruction method for identifying labeled cells in a three-dimensional pattern in the host; and (3) measurements of cell dispersion which indicate the specificity of cell movement in the host. We have used 5′ bromodeoxyuridine (BrdU) as a nuclear marker of transplanted fetal hippocampal cells, performing daily injections into the donor to label the majority of cells in the hippocampus between Gestation Days 15 and 19. After harvesting, the BrdU-labeled hippocampal cell suspensions were either cultured or grafted into normal adult hippocampus. The labeling index of these fetal hippocampal cells was calculated to be 90% in both smears of cell suspensions and 48-h cultures and these were predominantly (77%) neurons by immunostains. Quantitative studies of potential toxicity of the BrdU in culture also revealed no differences in neurite development or survival, compared to unlabeled cells. The survival and migration of grafted cells were quantitatively evaluated by three-dimensional serial reconstruction of host brain sections. Absolute graft cell survival (cells recovered/cells injected) varied according to location: grafts in close proximity to the ventricle and white matter tracts (corpus callosum or fimbria) showed improved survival (20 and 25%, respectively) compared to grafts localized entirely within the (normal) hippocampus (only 9% survival). Although the grafts expanded considerably from the initial injection site, the graft cell dispersion appeared nonspecific. Thus, this format of quantitative graft assessment indicates that under normal (nonlesioned) host conditions the location of the grafts critically influenced graft development and there was minimal specific migration of grafted cells into cell body regions.     

Intracanal placement of Ca(OH)2: a comparison of techniques.

Ten extracted human maxillary first molars were selected with a variety of root curvatures. The distofacial roots were resected and the mesiofacial canals were instrumented to a size #25 K file. Three techniques were used to introduce Ca(OH)2 paste into the instrumented canals. These techniques were evaluated for their ability to carry the Ca(OH)2 to working length and also to produce a dense fill. The Lentulo spiral was most effective in carrying the paste to working length. The Lentulo spiral also produced the highest quality fill. The Calasept injection system followed by a #25 finger plugger was the second most effective technique. Counterclockwise rotation of a #25 K file was the least effective of the techniques tested.     

The Effects of an Herbicide and Antibiotic Mixture on Aquatic Primary Producers and Grazers

Widespread use of agrochemicals increases their likelihood of entering aquatic systems in mixture. Despite different modes of action, atrazine (herbicide) and tetracycline (antibiotic) adversely affect non-target photosynthetic organisms individually, but the effects of simultaneous exposure to both contaminants are untested. We created microcosms containing microalgae (Chlorella sp.), floating macrophytes (Lemna minor), and a zooplankton grazer (Daphnia magna). Microcosms were exposed to environmentally relevant concentrations of atrazine and tetracycline, alone and together, for 10 days. Atrazine decreased Chlorella sp. abundance, but not enough to reduce food availability to D. magna whose reproduction and mortality were unaffected. In contrast, tetracycline and atrazine appeared to have additive effects on L. minor abundance and growth inhibition. These additive adverse effects suggest increased potential for L. minor population decline over the long term, and potential for altered species interactions in aquatic systems receiving agricultural runoff.     

RAS Amplification as a Negative Predictor of Benefit from Anti-EGFR–Containing Therapy Regimens in Metastatic Colorectal Cancer

Background RAS short variant (SV) mutations in colorectal cancer (CRC) are associated with lack of benefit from epidermal growth factor receptor (EGFR) monoclonal antibody (EGFRmAb). However, the clinical implications for RAS amplification (RASa) as a biomarker for anti‐EGFR therapy in CRC remain ill defined.MethodsGenomic analysis was performed using the Foundation Medicine (FM) comprehensive genomic profiling database of 37,233 CRC cases. Clinical outcomes were assessed using two independent cohorts: the City of Hope (COH) cohort of 338 patients with metastatic CRC (mCRC) and the Flatiron Health–FM real‐world clinicogenomic database (CGDB) of 3,904 patients with mCRC.Results RASa was detected in 1.6% (614/37,233) of primarily mCRC. RASa 6–9 (n = 241, 39%), 10–19 (n = 165, 27%), and ≥ 20 (n = 209, 34%) copy number subsets had co‐RAS SV/BRAF V600E in 63%/3%, 31%/0.6%, and 4.8%/0% of cases, respectively. In the COH cohort, six patients with RASa (13–54 copies) received EGFRmAb, four of six had progressive disease, two had stable disease, and median time to treatment discontinuation (TTD) was 2.5 months. Of the CGDB EGFRmAb‐treated patients, those with RASa (n = 9) had median TTD of 4.7 months and overall survival (OS) of 11.4 months, those with RAS SV (n = 101) had median TTD and OS of 5.3 and 9.4 months, and those with RAS/BRAF wild‐type (n = 608) had median TTD and OS of 7.6 and 13.7 months.ConclusionPatients with RASa without RAS mutations (1.1% of mCRC) may have poor outcomes on EGFRmAb, although numbers herein were small, and interpretation is confounded by combination chemotherapy. Larger independent studies are warranted to determine if RASa, including degree of amplification, may act similarly to RAS mutation as a resistance mechanism to EGFRmAb therapies.Implications for PracticeGenomic data suggest that RAS amplification occurs as the sole RAS/RAF alteration in >1% of colorectal cancer cases and that degree of amplification inversely correlates with co‐occurring MAPK pathway alterations. Preliminary clinical evidence suggests that RAS amplification may function similarly to RAS mutation as a negative predictor of benefit from anti‐epidermal growth factor receptor therapies in colorectal cancer. More clinical data are needed, and comprehensive genomic profiling, including detection of RAS amplification, should be used in trial design to inform therapy selection.