Poziotinib for EGFR exon 20-mutant NSCLC: Clinical efficacy, resistance mechanisms, and impact of insertion location on drug sensitivity

We report a phase II study of 50 advanced non-small cell lung cancer (NSCLC) patients with point mutations or insertions in EGFR exon 20 treated with poziotinib (NCT03066206). The study achieved its primary endpoint, with confirmed objective response rates (ORRs) of 32% and 31% by investigator and blinded independent review, respectively, with a median progression-free survival of 5.5 months. Using preclinical studies, in silico modeling, and molecular dynamics simulations, we found that poziotinib sensitivity was highly dependent on the insertion location, with near-loop insertions (amino acids A767 to P772) being more sensitive than far-loop insertions, an observation confirmed clinically with ORRs of 46% and 0% observed in near versus far-loop, respectively (p = 0.0015). Putative mechanisms of acquired resistance included EGFR T790M, MET amplifications, and epithelial-to-mesenchymal transition (EMT). Our data demonstrate that poziotinib is active in EGFR exon 20-mutant NSCLC, although this activity is influenced by insertion location.

Overexpression of Dicer in precursor lesions of lung adenocarcinoma

Differential microRNA (miR) expression is described in non-small cell lung carcinoma. miR biogenesis requires a set of proteins collectively referred to as the miR machinery. In the proposed multistep carcinogenesis model, peripheral adenocarcinoma of the lung develops from noninvasive precursor lesions known as atypical adenomatous hyperplasia (AAH) and bronchioloalveolar carcinoma (BAC). The gene array analysis of BAC and adenocarcinoma showed a transient up-regulation of Dicer (a key effector protein for small interfering RNA and miR function) and PACT along with down-regulation of most genes encoding miR machinery proteins. Immunohistochemically, Dicer was up-regulated in AAH and BAC and down-regulated in areas of invasion and in advanced adenocarcinoma. A fraction of adenocarcinomas lose Dicer as a result of deletions at the Dicer locus. Expanded immunohistochemical and Western blot analysis showed higher Dicer level in squamous cell carcinoma (SCC) of the lung when compared with adenocarcinoma. Other proteins of the RNA-induced silencing complex (RISC; SND1, PACT, and FXR1) were also present at higher levels in a SCC cell line when compared with an adenocarcinoma cell line. In conclusion, the stoichiometry of miR machinery and RISC depends on histologic subtype of lung carcinoma, varies along the AAH-BAC-adenocarcinoma sequence, and might explain the observed abnormal miR profile in lung cancer. The status of the endogenous miR machinery in various histologic subtypes and stages of lung cancer may help to predict the toxicity of and susceptibility to future RNA interference-based therapy.

BRAF mutation is unusual in chronic lymphocytic thyroiditis-associated papillary thyroid carcinomas and absent in non-neoplastic nuclear atypia of thyroiditis

Chronic lymphocytic thyroiditis (CLT) has an epidemiological relationship to papillary thyroid carcinoma (PTC). The follicular epithelium in CLT can be markedly atypical, with cytologic changes ranging from oncocytic morphology to clearing and overlapping. At the molecular level, the association between CLT and PTC is more controversial. In order to further characterize the molecular changes in CLT, this study examined the BRAF gene in 27 patient samples with CLT and without carcinoma and 28 samples with CLT and carcinoma (12 conventional papillary carcinomas, 13 follicular variants, and 3 tall cell variants). Microdissection, PCR, and sequencing of exon 15 of the BRAF gene were performed. BRAF mutations were uncommon in the cases studied with only two microscopic and two clinically sized PTCs had BRAF mutations (14%). There was no evidence of BRAF mutation in any of the areas with atypical follicular epithelium in CLT. These data suggest that BRAF is a less frequent mechanism of tumorigenesis in a background of CLT and that BRAF mutation is not present in the atypical follicular epithelium of CLT.