EML4-ALK Rearrangement as a Mechanism of Resistance to Osimertinib in Metastatic Lung Adenocarcinoma: A Case Report.

Osimertinib, a third-generation EGFR tyrosine kinase inhibitor, is the preferred frontline therapy for EGFR-mutant advanced NSCLC. However, despite its high initial response rates, multiple EGFR-independent mechanisms of resistance have been reported in patients receiving osimertinib. One such mechanism is the emergence of acquired, targetable oncogenic fusion events. It has been documented in other case reports that combination therapies can be efficacious in these scenarios. In our case report, we present a patient with EGFR-mutant advanced NSCLC who developed an acquired EML4-ALK rearrangement mediating resistance to osimertinib, which was overcome by using a combination of osimertinib with the ALK tyrosine kinase inhibitor alectinib.

Effect of prior therapy on tumor mutational burden in NSCLC.

BACKGROUND: Higher tumor mutation burden (TMB) in advanced non-small cell lung cancer (NSCLC) is associated with superior outcomes with checkpoint inhibitor therapy. Tissue samples subject to TMB analysis may be acquired after DNA-damaging therapies such as chemotherapy or radiation. The impact of these therapies on TMB results is unclear. This retrospective analysis explored differences in TMB among treatment-naïve samples and treatment-experienced samples. METHODS: NSCLC samples that underwent molecular profiling at a CLIA-certified genomics laboratory (Caris Life Sciences, Phoenix, AZ) and had available treatment and clinical history were identified. TMB was estimated by counting all coding variants (missense, nonsense, frameshift, in-frame InDels) identified by next-generation sequencing. Exceptions were synonymous mutations and any single nucleotide polymorphisms described as germline. History was reviewed under an IRB approved protocol to determine whether patients had received cytotoxic chemotherapy or radiation therapy in the year prior to collection of the tissue subject to TMB analysis. TMB values were compared between cohorts using the Wilcoxon test. Smoking adjusted P values were calculated using the chi-squared test of deviance. RESULTS: TMB was calculated for 970 annotated tumor specimens. Of these, 155 patients received chemotherapy and/or radiation prior to tissue collection. The median TMB was 8 mut/Mb in both the treatment-naïve and treatment-experienced cohorts. After adjusting for smoking, there was no significant difference in TMB between these cohorts (P=0.22). When analyzed separately, neither prior chemotherapy nor prior radiation therapy influenced TMB. TMB was higher when the specimen source was collected from a metastatic site compared to the primary site. CONCLUSIONS: Prior exposure to chemotherapy or radiation therapy was not associated with a significant difference in TMB.

KDM6B promotes activation of the oncogenic CDK4/6-pRB-E2F pathway by maintaining enhancer activity in MYCN-amplified neuroblastoma.

The H3K27me2/me3 histone demethylase KDM6B is essential to neuroblastoma cell survival. However, the mechanism of KDM6B action remains poorly defined. We demonstrate that inhibition of KDM6B activity 1) reduces the chromatin accessibility of E2F target genes and MYCN, 2) selectively leads to an increase of H3K27me3 but a decrease of the enhancer mark H3K4me1 at the CTCF and BORIS binding sites, which may, consequently, disrupt the long-range chromatin interaction of MYCN and E2F target genes, and 3) phenocopies the transcriptome induced by the specific CDK4/6 inhibitor palbociclib. Overexpression of CDK4/6 or Rb1 knockout confers neuroblastoma cell resistance to both palbociclib and the KDM6 inhibitor GSK-J4. These data indicate that KDM6B promotes an oncogenic CDK4/6-pRB-E2F pathway in neuroblastoma cells via H3K27me3-dependent enhancer-promoter interactions, providing a rationale to target KDM6B for high-risk neuroblastoma.

A novel closed-body model of spinal cord injury caused by high-pressure air blasts produces extensive axonal injury and motor impairments.

Diffuse axonal injury is thought to be the basis of the functional impairments stemming from mild traumatic brain injury. To examine how axons are damaged by traumatic events, such as motor vehicle accidents, falls, sports activities, or explosive blasts, we have taken advantage of the spinal cord with its extensive white matter tracts. We developed a closed-body model of spinal cord injury in mice whereby high-pressure air blasts targeted to lower thoracic vertebral levels produce tensile, compressive, and shear forces within the parenchyma of the spinal cord and thereby cause extensive axonal injury. Markers of cytoskeletal integrity showed that spinal cord axons exhibited three distinct pathologies: microtubule breakage, neurofilament compaction, and calpain-mediated spectrin breakdown. The dorsally situated axons of the corticospinal tract primarily exhibited microtubule breakage, whereas all three pathologies were common in the lateral and ventral white matter. Individual axons typically demonstrated only one of the three pathologies during the first 24h after blast injury, suggesting that the different perturbations are initiated independently of one another. For the first few days after blast, neurofilament compaction was frequently accompanied by autophagy, and subsequent to that, by the fragmentation of degenerating axons. TuJ1 immunolabeling and mice with YFP-reporter labeling each revealed more extensive microtubule breakage than did ßAPP immunolabeling, raising doubts about the sensitivity of this standard approach for assessing axonal injury. Although motor deficits were mild and largely transient, some aspects of motor function gradually worsened over several weeks, suggesting that a low level of axonal degeneration continued past the initial wave. Our model can help provide further insight into how to intervene in the processes by which initial axonal damage culminates in axonal degeneration, to improve outcomes after traumatic injury. Importantly, our findings of extensive axonal injury also caution that repeated trauma is likely to have cumulative adverse consequences for both brain and spinal cord.